ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Books
  • Articles  (4,336)
  • Wiley  (4,336)
  • 2010-2014  (4,336)
  • 1980-1984
  • 1950-1954
  • 2011  (4,336)
  • Geography  (4,336)
Collection
  • Books
  • Articles  (4,336)
Source
Publisher
Years
  • 2010-2014  (4,336)
  • 1980-1984
  • 1950-1954
Year
Journal
Topic
  • 1
    facet.materialart.
    Unknown
    Yield vs. quality trade‐offs for wheat in response to carbon dioxide and ozone (2011)
    Wiley
    Details
    Publication Date: 2011
    Description: Abstract Although it is established that there exist potential trade‐offs between grain yield and grain quality in wheat exposed to elevated carbon dioxide (CO2) and ozone (O3), their underlying causes remain poorly explored. To investigate the processes affecting grain quality under altered CO2 and O3, we analysed 57 experiments with CO2 or O3 exposure in different exposure systems. The study covered 24 cultivars studied in 112 experimental treatments from 11 countries. A significant growth dilution effect on grain protein was found: a change in grain yield of 10% by O3 was associated with a change in grain protein yield of 8.1% (R2=0.96), while a change in yield effect of 10% by CO2 was linked to a change in grain protein yield effect of 7.5% (R2=0.74). Superimposed on this effect, elevated CO2, but not O3, had a significant negative effect on grain protein yield also in the absence of effects on grain yield, indicating that there exists a process by which CO2 restricts grain protein accumulation, which is absent for O3. Grain mass, another quality trait, was more strongly affected by O3 than grain number, while the opposite was true for CO2. Harvest index was strongly and negatively influenced by O3, but was unaffected by CO2. We conclude that yield vs. protein trade‐offs for wheat in response to CO2 and O3 are constrained by close relationships between effects on grain biomass and less than proportional effects on grain protein. An important and novel finding was that elevated CO2 has a direct negative effect on grain protein accumulation independent of the yield effect, supporting recent evidence of CO2‐induced impairment of nitrate uptake/assimilation. Finally, our results demonstrated that processes underlying responses of grain yield vs. quality trade‐offs are very different in wheat exposed to elevated O3 compared to elevated CO2.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Dust impact on the West African heat low in summertime (2011)
    Wiley
    Details
    Publication Date: 2011-06-08
    Description: The impact of dust on a six-day pulsation of the West African heat low (WAHL) in summertime (14–20 July 2006) is investigated, with convective rainfall and dust bursts being observed over the Sahel at the beginning and end of the episode. Three Meso-NH simulations were designed which differed in their dust representation. All the simulations capture the variation in the WAHL intensity well, including the simulation without any dust effects. This shows the primary role of large-scale forcing on the WAHL pulsation. In spite of additional daytime heating and night-time cooling effects over the Sahara, the simulation with dust climatology resembles the simulation without any dust effects. In contrast, the simulation using a prognostic dust scheme enhances alternating northward advection of warm and dry air and southward advection of cold and wet air associated with the propagation of an African easterly wave, leading to a strengthening of the WAHL variabilities. This study highlights two effects of dust on the WAHL over the Sahara: a so-called direct effect associated with dust radiative heating, which increases the WAHL thickness, and a so-called indirect effect that intensifies both the African easterly jet and a related African easterly wave. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Characteristics of discontinuous permafrost based on ground temperature measurements and electrical resistivity tomography, southern Yukon, Canada (2011)
    Wiley
    Details
    Publication Date: 2011-06-09
    Description: Warm permafrost conditions (mean temperatures of −3°C to −0.1°C) were investigated in detail at 13 valley and mountain sites in the sporadic (10–50%) and extensive (50–90%) discontinuous permafrost zones in the southern half of the Yukon (60°N to 64°N), using a combination of ground temperature monitoring, electrical resistivity tomography (ERT), frost table probing and coring. Sites were selected to cover a wide range of substrates, vegetation types and ground ice contents. ERT profiling in the spring imaged both deep seasonal frost and perennially frozen ground. Deep active layers measured by probing at the end of summer were also detectable by ERT. Where ground temperatures indicated that the base of permafrost was at a depth of less than 25 m, vertical transitions in apparent resistivity were more sharply defined in coarse materials than in fine-grained deposits, probably because of differences in unfrozen moisture contents at temperatures just below 0°C. Apparent resistivity values related to excess ice fraction and ground temperatures were similar to those previously obtained in Mongolia and Iceland, but generally lower than in ice-rich rock glaciers in European studies. The observations revealed the complexity of site conditions where permafrost is discontinuous and the utility of ERT, in combination with other methods, to investigate permafrost thickness, spatial extent and ice content for infrastructure planning or climate change studies. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 1045-6740
    Electronic ISSN: 1099-1530
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Motivation, rationale and key results from the GERBILS Saharan dust measurement campaign (2011)
    Wiley
    Details
    Publication Date: 2011-06-09
    Description: The Geostationary Earth Radiation Budget Intercomparison of Longwave and Shortwave radiation (GERBILS) was an observational field experiment over North Africa during June 2007. The campaign involved 10 flights by the FAAM BAe-146 research aircraft over southwestern parts of the Sahara Desert and coastal stretches of the Atlantic Ocean. Objectives of the GERBILS campaign included characterisation of mineral dust geographic distribution and physical and optical properties, assessment of the impact upon radiation, validation of satellite remote sensing retrievals, and validation of numerical weather prediction model forecasts of aerosol optical depths (AODs) and size distributions. We provide the motivation behind GERBILS and the experimental design and report the progress made in each of the objectives. We show that mineral dust in the region is relatively non-absorbing (mean single scattering albedo at 550 nm of 0.97) owing to the relatively small fraction of iron oxides present (1–3%), and that detailed spectral radiances are most accurately modelled using irregularly shaped particles. Satellite retrievals over bright desert surfaces are challenging owing to the lack of spectral contrast between the dust and the underlying surface. However, new techniques have been developed which are shown to be in relatively good agreement with AERONET estimates of AOD and with each other. This encouraging result enables relatively robust validation of numerical models which treat the production, transport, and deposition of mineral dust. The dust models themselves are able to represent large-scale synoptically driven dust events to a reasonable degree, but some deficiencies remain both in the Sahara and over the Sahelian region, where cold pool outflow from convective cells associated with the intertropical convergence zone can lead to significant dust production. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, the Met Office
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Modeling Production of Migratory Catfish Larvae (Pimelodidae) on the basis of Regional Hydro-climatology features of the Madre de Dios Basin in Southeastern Peru (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 6
    facet.materialart.
    Unknown
    Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Rapid population growth and economic development have led to increased anthropogenic pressures on the Tibetan Plateau, causing significant land cover changes with potentially severe ecological consequences. To assess whether these pressures are also affecting the remote montane-boreal lakes on the SETibetan Plateau, fossil pollen and diatom data from two lakes were synthesised. The interplay of aquatic and terrestrial ecosystem response was explored in respect to climate variability and human activity over the past 200 years. Non-metric multidimensional scaling and procrustes rotation analysis were undertaken to determine whether pollen and diatom responses in each lake were similar and synchronous. Detrended canonical correspondence analysis was used to develop quantitative estimates of compositional species turnover. Despite instrumental evidence of significant climatic warming on the southeastern Plateau, the pollen and diatom records indicate very stable species composition throughout their profiles and show only very subtle responses to environmental changes over the past 200 years. The compositional species turnover (0.36-0.94 SD) is relatively low in comparison to the species reorganisations known from the periods during the mid- and early-Holocene (0.64-1.61 SD) on the SE Plateau, and also in comparison to turnover rates of sediment records from climate - sensitive regions in the circum-arctic. Our results indicate that climatically-induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem in our study area. Synergistic processes of post Little Ice Age warming, 20 th century climate warming and extensive reforestations since the 19 th century have initiated a change from natural oak-pine forests to semi-natural, likely less resilient pine-oak forests. Further warming and anthropogenic disturbances would possibly exceed the ecological threshold of these ecosystems and lead to severe ecological consequences.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 7
    facet.materialart.
    Unknown
    Early response of the platypus to climate warming (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Combining a climatic envelope modeling technique with more than two centuries (1800-2009) of distribution records has revealed the effects of a changing climate on the egg-laying monotreme, the platypus, Ornithorhynchus anatinus . We show that the main factor associated with platypus occurrence switched from aquatic habitat availability (estimated by rainfall) to thermal tolerances (estimated by annual maximum temperature) in the 1960's. This correlates directly with the change in the annual maximum temperature anomaly from cooler to warmer conditions in southeastern Australia. Modeling of platypus habitat under emission scenarios (A1B, A2, B1 and B2) revealed large decreases (〉 30%) in thermally suitable habitat by 2070. This reduction, compounded by increasing demands for water for agriculture and potable use, suggests that there is real cause for concern over the future status of this species, and highlights the need for restoration of thermal refugia within the platypus’ modeled range.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 8
    facet.materialart.
    Unknown
    Metabolically-induced pH fluctuations by some coastal calcifiers exceed projected 22nd century ocean acidification: a mechanism for differential susceptibility? (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Anthropogenically-mediated decreases in pH, termed ocean acidification (OA), may be a major threat to marine organisms and communities. Research has focussed mainly on tropical coral reefs, but temperate reefs play a no less important ecological role in colder waters, where OA effects may first be manifest. Here, we report that trends in pH at the surface of three ecologically-important cold-water calcifiers (a primary producer and herbivores), under a range of fluid flows, differ substantially from one another, and for two of the three calcifiers the pH, during darkness, is lower than the mean projected pH due to OA for the surface waters of the global ocean beyond the year 2100. Using micro-optodes, we show that each calcifier had a different pH gradient between its surface and mainstream seawater, i.e. within the diffusion boundary layer which appears to act as an environmental buffer to mainstream pH. Abalone encountered only mainstream seawater pH, whereas pH at the sea urchins’ surface was reduced by ~0.35 units. For coralline algae, pH was ~0.5 units higher in the light and ~0.35 units lower under darkness than in ambient mainstream seawater. This wide range of pH within the DBL of some calcifiers will probably affect their performance under projected future reductions in pH due to OA. Differing exposure to a range of surface pH may result in differential susceptibility of calcifiers to OA. Such fluctuations are no doubt regulated by the interplay of water movement, morphology and metabolic rates (e.g. respiration, calcification and/or photosynthesis). Our study, by considering physics (flow regime), chemistry (pH gradients versus OA future projections) and biology (trophic level, physiology and morphology), reveals that predicting species-specific responses and subsequent ecosystem restructuring to OA is complex and requires a holistic, ecomechanical, approach.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 9
    facet.materialart.
    Unknown
    Exploring the assimilation of IASI radiances in forecasting polar lows (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: We studied the use of IASI data to improve the forecasts of extreme weather events in the Arctic region. For this purpose, the HARMONIE/Norway regional model was used. A set of 366 IASI channels was initially chosen from the ECMWF archived database. Active channels showing the best fit with the analysis system were selected by applying a multi-step monitoring technique. The IASI data were assimilated together with most of the available conventional and operational satellite observations using a three-dimensional variational data assimilation system. Four experiments with cyclic assimilations and subsequent 48-hour forecasts were performed during the IPY-THORPEX campaign period to evaluate the impact of the IASI data and the campaign observations on the hydrostatic HARMONIE/Norway analyses and forecasts. The assessment of the degrees of freedom for signals on the analysis showed that incorporating the IASI data in the assimilation system improved the contribution of the other observations. The utilization of an energy norm-based approach proved the sensitivity of the forecasts to the IASI channels in cases dominated by dynamic instabilities leading to quickly developing weather systems like, for example, polar lows. Comparison of the HARMONIE/Norway forecasts against independent observations and the ECMWF analyses showed a clear positive impact of the IASI data on geopotential fields in mid-troposphere and in the troposphere in general, respectively. We found small but significant positive impact on the temperature and humidity in the lower troposphere. A case-study showed positive impact of IASI radiances on the analysis and forecasts of a polar low. The impact on the forecasts lasted up to 24 hours when extra in situ campaign data were excluded from the analysis, and up to 36 hours when the campaign data were assimilated together with the IASI radiances. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 10
    facet.materialart.
    Unknown
    TDR pressure cell for monitoring water content retention and bulk electrical conductivity curves in undisturbed soil samples (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: The water retention curve (θ(ψ)), which defines the relationship between soil volumetric water content (θ) and matric potential (ψ), is of paramount importance in characterizing the hydraulic behaviour of soils. However, few methods are so far available for estimating θ(ψ) in undisturbed soil samples. We present a new design of TDR-pressure cell (TDR-Cell) for estimating θ(ψ) in undisturbed soil samples. The TDR-Cell consists of a 50-mm-long and 50-mm internal diameter stainless steel cylinder (which constitutes the outer frame of a coaxial line) attached to a porous ceramic disc and closed at the ends with two aluminium lids. A 49-mm-long and 3-mm-diameter stainless steel rod, which runs longitudinally through the centre of the cylinder, constitutes the inner rod of a coaxial TDR probe. The TDR-Cell was used to determine the θ(ψ) curves of a packed sand and seven undisturbed soil samples from three profiles of agricultural soils. These θ(ψ) curves were subsequently compared to those obtained from the corresponding 2-mm sieved soils using the pressure plate method. Measurements of bulk electrical conductivity, σ a , as a function of the water content, σ a (θ), of the undisturbed soil samples were also performed. An excellent correlation (R 2 = 0.988) was found between the θ values measured by TDR on the different undisturbed soils and the corresponding θ obtained from the soil gravimetric water content. A typical bimodal θ(ψ) function was found for most of the undisturbed soil samples. Comparison between the θ(ψ) curves measured with the TDR-Cell and those obtained from the 2-mm sieved soils showed that the pressure plate method overestimates θ at low ψ values. The σ a (θ) relationship was well described by a simple power expression (R 2 〉 0.95), in which the power factor, defined as tortuosity, ranged between 1.18 and 3.75. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 11
    facet.materialart.
    Unknown
    Investigation and Modeling of winter streamflow timing and magnitude under changing climate conditions for the Catskill Mountain region, New York, USA (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: Snowfall is an important part of the yearly water balance for the Catskill Mountains in New York State, the location of water supply reservoirs for New York City. Recent studies have shown that the effects of climate change on the hydrology of the Catskills will most likely create (1) a decrease in the proportion of precipitation falling as snow, (2) a shift in the timing of snowmelt that will cause snowmelt-supplemented streamflow events to occur earlier in the fall and winter, and (3) a decrease in the magnitude of traditionally high April streamflow. The shift in timing of snowmelt-influenced streamflow events is measured by the winter-early spring centre of volume (WSCV), defined as the Julian Day on which half the total streamflow volume from January to May occurs. Studies of streamflow, precipitation, and temperature trends in the last 50 years have shown that the WSCV is already earlier by about 5–10 days. This study investigates the use of watershed-scale snowpack and snowmelt algorithms that are incorporated in two existing watershed water quality models, Generalized Watershed Loading Functions-Variable Source Area (GWLF-VSA) and Soil and Water Assessment Tool (SWAT), to capture the potential effects of climate change on the timing and magnitude of streamflow during the late fall, winter, and early spring for the Catskill Mountain region. The GWLF-VSA model reasonably simulated the recent shifts in the winter streamflow timing, with simulations over the previous 50-year period yielding shifts in WSCV of 2–15 days. The SWAT model yielded similar results as the GWLF-VSA simulations. Scenarios of potential climate change 100 years in the future showed a similar shift in direction of timing winter streamflow, but at a larger magnitude than observed to date with WSCV occurring 15–20 days earlier. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 12
    facet.materialart.
    Unknown
    Germanium-silicon as a flow path tracer: Application to the Rio Icacos watershed (2011)
    Wiley
    Details
    Publication Date: 2011-06-17
    Description: We use dissolved silicon together with its “geochemical twin” germanium for the first time as a hydrologic tracer to study water delivery to the stream during storm events in the Rio Icacos watershed, Puerto Rico. Ge and Si were measured on base flow, stormflow, springwater, and soil water samples. Compositions of all of these waters appear to reflect varying contributions from three components, which we attribute to solutes released from bedrock weathering (groundwater), from short-term soil-water interaction (quick soil water), and longer-term soil-water interaction (matrix soil water). Base flow stream waters have high Si and moderate Ge (Ge/Si ratio ∼0.29 μmol/mol), consistent with a predominantly bedrock weathering source as indicated by their similarity with water sampled from springs emerging from the saprolite-bedrock boundary on a hillslope landslide scar. During storm events there is a shift toward more dilute compositions (but higher Ge/Si ratios) similar to those measured on water samples from temporary depression storage and overland flow (quick soil water). Geochemical mass balance shows that 80%–90% of the stream chemistry can be explained by mixing groundwater with this quick soil water composition, which we infer to reflect new water traveling as shallow throughflow. Stream water δ18O values decrease to more negative values typical of precipitation supporting rapid delivery of rainwater to the stream channel during stormflow. The third component, with a Ge-rich composition characteristic of soil matrix water sampled by tension lysimeters, is required to explain higher stream water Ge/Si ratios measured during hydrograph recession. We infer from this an additional, slower, and less dominant pathway for delivery of soil water to the stream channel.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 13
    facet.materialart.
    Unknown
    Multiscale modeling of chemotaxis in homogeneous porous media (2011)
    Wiley
    Details
    Publication Date: 2011-06-19
    Description: We present a predictive, multiscale modeling framework for chemotaxis in porous media. This model results from volume averaging the governing equations for bacterial transport at the microscale and is expressed in terms of effective medium coefficients that are predicted from the solution of the associated closure problems. As a result, the averaged chemotactic velocity is an explicit function of the attractant concentration field and diffusivity, rather than an empirical effective chemotactic sensitivity coefficient. The model was validated by comparing the transverse bacterial concentration profiles with experimental measurements for Escherichia coli HCB1 in a T-sensor. The averaged chemotactic velocity predicted by the model was found to be within the range of values reported in the literature. Reasonable agreement (approximately 10% mean absolute error) between theory and experiments was found for several flow rates. In order to assess the potential for decreasing the computational demands of the model, the macroscale domain was divided into subdomains for the coupling of bacterial transport to that of the attractant. Sensitivity analysis was performed regarding the number of subdomains chosen, and the results indicate that bacterial transport (as measured by concentration profiles) was not highly affected by this choice. Overall, these results suggest that the predictive, multiscale modeling framework is reliable for modeling chemotaxis in porous media when chemotactic transport is significant compared to convective transport.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 14
    facet.materialart.
    Unknown
    Impacts of the ice-cover and sea-surface temperature on a polar low over the Nordic seas: a numerical case study (2011)
    Wiley
    Details
    Publication Date: 2011-06-21
    Description: Extreme mesoscale weather in the Arctic region consists mainly of cases with shallow fronts that often form in the vicinity of the ice-edge and intense storms called polar lows. This article describes high-resolution numerical simulations of a severe weather event that occurred on 1 March 2008 over the Barents Sea. The event was recorded during the IPY–THORPEX field experiments carried out during February and March 2008. The numerical simulations indicated the formation of a low-pressure system over the Barents Sea on 29 February 2008 due to baroclinic instability. On 1 March, the surface low moved onto the sea-ice around Spitsbergen and decayed later on. The conditions that prevailed before the dissipation of the surface low were favourable for the formation of a polar low. Two experiments were performed to test the possibilities of triggering a polar low through certain modifications to the surface conditions. In the first experiment, the sea-ice around Spitsbergen was removed. No polar low developed in this case, since the static stability was too high. In the second experiment, an attempt to reduce the static stability was made by raising the sea-surface temperature by 5 K. The surface low persisted over the Barents Sea area due to the increased surface heating and led to a strong outbreak of Arctic air over the Norwegian Sea on 2 March. The Arctic-air outbreak formed a sharp baroclinic zone which was absent in the control simulation. A secondary mesoscale low was triggered near the baroclinic zone over the Norwegian Sea, which grew into an intense polar low with surface winds reaching hurricane force. Formation of the polar low was due to baroclinic instability, whereas convective instability was important during the growth of the low. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 15
    facet.materialart.
    Unknown
    Modified equilibrium temperature models for cold-water streams (2011)
    Wiley
    Details
    Publication Date: 2011-06-21
    Description: Water temperature determines the spatial distribution of fish species, including cold-water fish such as trout, and is driven by the balance of the heat flux across the water surface and the heat flux across the sediment surface. In this study, a modified equilibrium temperature model was developed for cold-water streams that includes the effect of groundwater inflow. The modified equilibrium temperature model gives estimates of daily average stream temperature based on climate conditions, riparian shading, stream width, and groundwater input rate and temperature. For a small tributary stream with relatively uniform riparian shading, the modified equilibrium temperature was found to be a good predictor of daily average stream temperature, with a root-mean-square errors (RMSE) of 1.2°C. The modified equilibrium temperature model also gave good estimates (1.4°C RMSE) of daily average stream temperature for a larger stream when riparian shading was averaged over sufficiently long distances. A sensitivity analysis using the modified equilibrium temperature model confirmed that water temperature in cold-water streams varies strongly with riparian shading, stream width, and both groundwater inflow rate and temperature. These groundwater parameters therefore need to be taken into account when climate change impacts on stream temperature are projected. The stream temperature model developed in this study is a useful tool to characterize temperature conditions in cold-water streams with different levels of riparian shading and groundwater inputs and to assess the impact of future land use and climate change on temperature in these streams.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 16
    facet.materialart.
    Unknown
    Reductions in daily soil temperature variability increases soil microbial biomass C and reduces soil N availability in the Chihuahuan Desert: potential implications for ecosystem C and N fluxes (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Maximum and minimum soil temperatures affect belowground processes. In the past 50 years in arid regions, measured reductions in the daily temperature range of air (DTR air ) most likely generated similar reductions in the unmeasured daily temperature range of soil (DTR soil ). However, the role of DTR soil in regulating microbial and plant processes has not been well described. We experimentally reduced DTR soil in the Chihuahuan Desert at Big Bend National Park over 3 years. We used shade cloth that effectively decreased DTR soil by decreasing daily maximum temperature and increasing nighttime minimum temperature. A reduction in DTR soil generated on average a two-fold increase in soil microbial biomass carbon (MBC), a 42% increase in soil CO 2 efflux and a 16% reduction in soil NO 3 - -N availability; soil available NH 4 + -N was reduced by 18% in the third year only. Reductions in DTR soil increased soil moisture up to 15% a few days after a substantial rainfall. Increased soil moisture contributed to higher CO 2 efflux, but not MBC, which was significantly correlated with DTR soil . Net photosynthetic rates at saturating light ( A sat ) in Larrea tridentata was not affected by reductions in DTR soil over the 3-year period. Arid ecosystems may become greater sources of C to the atmosphere with reduced DTR soil , resulting in a positive feedback to rising global temperatures, if increased C loss is not eventually balanced by increased C uptake. Ultimately, ecosystem models of N and C fluxes will need to account for these temperature-driven processes.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 17
    facet.materialart.
    Unknown
    Reconstruction and attribution of the carbon sink of European forests between 1950 and 2000 (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: European forests are an important carbon sink, yet the relative contributions to this sink of climate, atmospheric CO2 concentration ([CO2]), nitrogen deposition and forest management are under debate. We attributed the European carbon sink in forests using ORCHIDEE-FM, a process-based vegetation model that differs from earlier versions of ORCHIDEE by its explicit representation of stand growth and idealized forest management. The model was applied on a grid across Europe to simulate changes in the net ecosystem productivity (NEP) of forests with and without changes in climate, [CO2] and age structure, the three drivers represented in ORCHIDEE-FM. The model simulates carbon stocks and volume increment that are comparable – RMSE of 2 m3 ha-1 yr-1 and 1.7 kgC m-2 respectively – with inventory-derived estimates at country level for 20 European countries. Our simulations estimate a mean European forest NEP of 175 ± 52 gC m-2 yr-1 in the 1990s. The model simulation that is most consistent with inventory records provides an upwards trend of forest NEP of 1 ± 0.5 gC m-2 yr-2 between 1950 and 2000 across the EU 25. Further, the method used for reconstructing past age structure was found to dominate its contribution to temporal trends in NEP. The potentially large fertilizing effect of nitrogen deposition cannot be told apart as the model does not explicitly simulate the nitrogen cycle. Among the three drivers that were considered in this study, the fertilizing effect of increasing [CO2] explains about 61% of the simulated trend, against 26% to changes in climate, and 13% only to changes in forest age structure. The major role of [CO2] at the continental scale is due to its homogeneous impact on NPP. At the local scale, however, changes in climate and forest age structure often dominate trends in NEP by affecting NPP and heterotrophic respiration.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 18
    facet.materialart.
    Unknown
    Landslide impact on organic carbon cycling in a temperate montane forest (2011)
    Wiley
    Details
    Publication Date: 2011-06-23
    Description: In humid, forested mountain belts, bedrock landslides can harvest organic carbon from above ground biomass and soil (OC modern ) while acting to refresh the landscape surface and turnover forest ecosystems. Here we assess the impact of landslides on organic carbon cycling in 13 river catchments spanning the length of the western Southern Alps, New Zealand, over four decades. We combine spatial and temporal landslide maps with the observed distribution and measured variability of hillslope OC modern stocks. On average, we estimate that landslides mobilised 7.6 ± 2.9 tC km -2  yr -1 of OC modern , ~30% of which was delivered to river channels. Comparison with published estimates of OC modern export in river suspended load suggests additional erosion of OC modern by small, shallow landslides or overland flow in catchments. The exported OC modern may contribute to geological carbon sequestration if buried in sedimentary deposits. Landslides may have also contributed to carbon sequestration over shorter timescales (〈100 years). 5.4 ± 3.0 tC km -2  yr -1 of the eroded OC modern was retained on hillslopes, representing a net-carbon sink following re-vegetation of scar surfaces. In addition, we find that landslides caused rapid turnover of the landscape, with rates of 0.3 % of the surface area per decade. We measured high rates of net ecosystem productivity in this forest of 94 ± 11 tC km -2  yr -1 , which is consistent with rapid landscape turnover suppressing ecosystem retrogression. Landslide-OC modern yields and rates of turnover vary between river catchments and appear to be controlled by gradients in climate (precipitation) and geomorphology (rock exhumation rate, topographic slope). Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 19
    facet.materialart.
    Unknown
    Temporal trends in N2O flux dynamics in a Danish wetland – effects of plant-mediated gas transport of N2O and O2 following changes in water level and soil mineral-N availability (2011)
    Wiley
    Details
    Publication Date: 2011-06-24
    Description: Temporal trends of N 2 O fluxes across the soil-atmosphere interface were determined using continuous flux chamber measurements over an entire growing season of a subsurface aerating macrophyte ( P halaris arundinacea ) in a non-managed Danish wetland. Observed N 2 O fluxes were linked to changes in subsurface N 2 O and O 2 concentrations, water level, light intensity as well as mineral-N availability. Weekly concentration profiles showed that seasonal variations in N 2 O concentrations were directly linked to the position of the WL and O 2 availability at the capillary fringe above the WL. N 2 O flux measurements showed surprisingly high temporal variability with marked changes in fluxes and shifts in flux directions from net source to net sink within hours associated with changing light conditions. Systematic diurnal shifts between net N 2 O emission during day time and deposition during night time were observed when max subsurface N 2 O concentrations were located below the root zone. Correlation (p〈0.001) between diurnal variations in O 2 concentrations and incoming PAR radiation highlighted the importance of plant-driven subsoil aeration of thse root zone and the associated controls on coupled nitrification/denitrification. Therefore, P . arundinacea played an important role in facilitating N 2 O transport from the root zone to the atmosphere and exclusion of the aboveground biomass in flux chamber measurements may lead to significant underestimations on net ecosystem N 2 O emissions. Complex interactions between seasonal changes in O 2 and mineral N-availability following near-surface WL fluctuations in combination with plant mediated gas transport by P . arundinacea controlled the subsurface N 2 O concentrations and gas transport mechanisms responsible for N 2 O fluxes across the soil-atmosphere interface. Results demonstrate the necessity for addressing this high temporal variability and potential plant transport of N 2 O in future studies of net N 2 O exchange across the soil-atmosphere interface
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 20
    facet.materialart.
    Unknown
    Propagation of the Storegga tsunami into ice-free lakes along the southern shores of the Barents Sea (2011)
    Wiley
    Details
    Publication Date: 2011-06-09
    Description: Deposits in coastal lakes in northernmost Norway reveal that the Storegga tsunami propagated well into the Barents Sea ca. 8100–8200 years ago. A tsunami deposit – found in cores from five coastal lakes located near the North Cape in Finnmark – rests on an erosional unconformity and consists of graded sand layers and re-deposited organic remains. Rip-up clasts of lake mud, peat and soil suggest strong erosion of the lake floor and neighbouring land. Inundation reached at least 500 m inland and minimum vertical run-up has been reconstructed to 3–4 m. In this part of the Arctic coastal lakes are usually covered by 〉1 m of solid lake ice in winter. The significant erosion and deposition of rip-up clasts indicate that the lakes were ice free and that the ground was probably not frozen. We suggest that the Storegga slide and ensuing tsunami happened sometime in the summer season, between April and October. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 21
    facet.materialart.
    Unknown
    River Meander Dynamics: developments in modelling and empirical analyses (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 22
    facet.materialart.
    Unknown
    Soil loss rates due to piping erosion (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: ABSTRACT Compared to surface soil erosion by water, subsurface erosion (piping) is generally less studied and harder to quantify. However, wherever piping occurs, it is often a significant or even the main sediment source. In this study, the significance of soil loss due to piping is demonstrated through an estimation of soil volume lost from pipes and pipe collapses (n = 560) in 137 parcels under pasture on loess-derived soils in a temperate humid climate (Belgium). Assuming a period of 5 to 10 years for pipe collapse to occur, mean soil loss rates of 2.3 and 4.6 t ha −1  yr −1 are obtained, which are at least one order of magnitude higher than surface erosion rates (0.01-0.29 t ha −1 yr −1 ) by sheet and rill erosion under a similar land use. The obtained results for the study area in the Flemish Ardennes (Belgium) correspond well to other measurements in temperate environments, they are however considerably smaller compared to soil loss rates due to subsurface erosion in semi-arid environments. Although local slope gradient and drainage area largely control the location of collapsed pipes in the study area, these topographic parameters do not explain differences in eroded volumes by piping. Hence, incorporation of subsurface erosion in erosion models is not straightforward. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 23
    facet.materialart.
    Unknown
    Fluvial and slope-wash erosion of soil-mantled landscapes: detachment- or transport-limited? (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: ABSTRACT Many numerical landform evolution models assume that soil erosion by flowing water is either purely detachment-limited (i.e. erosion rate is related to the shear stress, power, or velocity of the flow) or purely transport-limited (i.e. erosion/deposition rate is related to the divergence of shear stress, power, or velocity). This paper reviews available data on the relative importance of detachment-limited versus transport-limited erosion by flowing water on soil-mantled hillslopes and low-order valleys. Field measurements indicate that fluvial and slope-wash modification of soil-mantled landscapes is best represented by a combination of transport-limited and detachment-limited conditions with the relative importance of each approximately equal to the ratio of sand and rock fragments to silt and clay in the eroding soil. Available data also indicate that detachment/entrainment thresholds are highly variable in space and time in many landscapes, with local threshold values dependent on vegetation cover, rock-fragment armoring, surface roughness, soil texture and cohesion. This heterogeneity is significant for determining the form of the fluvial/slope-wash erosion or transport law because spatial and/or temporal variations in detachment/entrainment thresholds can effectively increase the nonlinearity of the relationship between sediment transport and stream power. Results from landform evolution modeling also suggest that, aside from the presence of distributary channel networks and autogenic cut-and-fill cycles in non-steady-state transport-limited landscapes, it is difficult to infer the relative importance of transport-limited versus detachment-limited conditions using topography alone. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 24
    facet.materialart.
    Unknown
    Predictive uncertainty of chaotic daily streamflow using ensemble wavelet networks approach (2011)
    Wiley
    Details
    Publication Date: 2011-06-11
    Description: Perfect or even mediocre weather predictions over a long period are almost impossible because of the ultimate growth of a small initial error into a significant one. Even though the sensitivity of initial conditions limits the predictability in chaotic systems, an ensemble of prediction from different possible initial conditions and also a prediction algorithm capable of resolving the fine structure of the chaotic attractor can reduce the prediction uncertainty to some extent. All of the traditional chaotic prediction methods in hydrology are based on single optimum initial condition local models which can model the sudden divergence of the trajectories with different local functions. Conceptually, global models are ineffective in modeling the highly unstable structure of the chaotic attractor. This paper focuses on an ensemble prediction approach by reconstructing the phase space using different combinations of chaotic parameters, i.e., embedding dimension and delay time to quantify the uncertainty in initial conditions. The ensemble approach is implemented through a local learning wavelet network model with a global feed-forward neural network structure for the phase space prediction of chaotic streamflow series. Quantification of uncertainties in future predictions are done by creating an ensemble of predictions with wavelet network using a range of plausible embedding dimensions and delay times. The ensemble approach is proved to be 50% more efficient than the single prediction for both local approximation and wavelet network approaches. The wavelet network approach has proved to be 30%–50% more superior to the local approximation approach. Compared to the traditional local approximation approach with single initial condition, the total predictive uncertainty in the streamflow is reduced when modeled with ensemble wavelet networks for different lead times. Localization property of wavelets, utilizing different dilation and translation parameters, helps in capturing most of the statistical properties of the observed data. The need for taking into account all plausible initial conditions and also bringing together the characteristics of both local and global approaches to model the unstable yet ordered chaotic attractor of a hydrologic series is clearly demonstrated.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 25
    facet.materialart.
    Unknown
    Convergence of approaches toward reducing uncertainty in predictions in ungauged basins (2011)
    Wiley
    Details
    Publication Date: 2011-06-11
    Description: The focus in the search for more reliable predictions in ungauged basins (PUB) has generally been on reducing uncertainty in watershed models (mainly their parameters). More recently, however, we seem to remember that the ultimate objective is not to define the parameters of a specific model but to understand the watershed: What behavior do we expect the ungauged watershed to exhibit? And what behavior should not occur in a particular ungauged watershed? The answers to these questions actually provide additional information that can be assimilated in watershed models for uncertainty reduction in PUB. This extension to hydrologic modeling approaches provides a quantitative link between watershed modeling and statistical hydrology as well as process hydrology that has to be explored. We witness a convergence of approaches—Bayesian, set theoretic, and optimization based—toward utilizing this link. The result is an opportunity for the (quantitative) dialog between modelers, statistical hydrologists, and experimentalists. We close our discussion of this development by presenting new and exciting research questions that we now have to address.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 26
    facet.materialart.
    Unknown
    Assessing the detail needed to capture rainfall-runoff dynamics with physics-based hydrologic response simulation (2011)
    Wiley
    Details
    Publication Date: 2011-06-11
    Description: Concept development simulation with distributed, physics-based models provides a quantitative approach for investigating runoff generation processes across environmental conditions. Disparities within data sets employed to design and parameterize boundary value problems used in heuristic simulation inevitably introduce various levels of bias. The objective was to evaluate the impact of boundary value problem complexity on process representation for different runoff generation mechanisms. The comprehensive physics-based hydrologic response model InHM has been employed to generate base case simulations for four well-characterized catchments. The C3 and CB catchments are located within steep, forested environments dominated by subsurface stormflow; the TW and R5 catchments are located in gently sloping rangeland environments dominated by Dunne and Horton overland flows. Observational details are well captured within all four of the base case simulations, but the characterization of soil depth, permeability, rainfall intensity, and evapotranspiration differs for each. These differences are investigated through the conversion of each base case into a reduced case scenario, all sharing the same level of complexity. Evaluation of how individual boundary value problem characteristics impact simulated runoff generation processes is facilitated by quantitative analysis of integrated and distributed responses at high spatial and temporal resolution. Generally, the base case reduction causes moderate changes in discharge and runoff patterns, with the dominant process remaining unchanged. Moderate differences between the base and reduced cases highlight the importance of detailed field observations for parameterizing and evaluating physics-based models. Overall, similarities between the base and reduced cases indicate that the simpler boundary value problems may be useful for concept development simulation to investigate fundamental controls on the spectrum of runoff generation mechanisms.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 27
    facet.materialart.
    Unknown
    Morphometric analysis of aeolian bedforms in the Namib Sand Sea using ASTER data (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: The ASTER Global Digital Elevation Model (GDEM) has made elevation data at 30 m spatial resolution freely available, enabling reinvestigation of morphometric relationships derived from limited field data using much larger sample sizes. We use these data to analyse a range of morphometric relationships derived for dunefields (between dune height, spacing, and equivalent sand thickness) in the Namib Sand Sea, which was chosen because there are a number of extant studies we could use for comparison with our results. We test the relative accuracy of GDEM for capturing dune height and shape against multiple individual ASTER DEM scenes and against field surveys, highlighting the smoothing of the dune crest and resultant underestimation of dune height, and the omission of the smallest dunes, due to the 30 m sampling of ASTER DEM products. We demonstrate that morphometric relationships derived from GDEM data are broadly comparable with relationships derived by previous methods, across a range of different dune types. The data confirm patterns of dune height, spacing and equivalent sand thickness mapped previously in the Namib Sand Sea, but add new detail to these patterns. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 28
    facet.materialart.
    Unknown
    Exploring effects of rainfall intensity and duration on soil erosion at the catchment scale using openLISEM – Prado catchment, SE Spain (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: In semi-arid areas high-intensity rainfall events are often held responsible for the main part of soil erosion. Long-term landscape evolution models usually use average annual rainfall as input, making the evaluation of single events impossible. Event-based soil erosion models are better suited for this purpose, but cannot be used to simulate longer timescales and are usually applied to plots or small catchments. In this study, the openLISEM event-based erosion model was applied to the medium sized ( 50 km 2 ) Prado catchment in SE Spain. Our aim was to (i) test the model's performance for medium sized catchments; (ii) test the ability to simulate four selected typical Mediterranean rainfall events of different magnitude, and (iii) explore the relative contribution of these different storms to soil erosion using scenarios of future climate variability. Results show that due to large differences in the hydrologic response between storms of different magnitudes, each event needed to be calibrated separately. The relation between rainfall event characteristics and the calibration factors might help in determining optimal calibration values if event characteristics are known. Calibration of the model features some drawbacks for large catchments due to spatial variability in K sat values. Scenario calculations show that, although 50% of soil erosion occurs as a result of high frequency, low intensity rainfall events, large magnitude, low frequency events potentially contribute significantly to total soil erosion. The results illustrate the need to incorporate temporal variability in rainfall magnitude-frequency distributions in landscape evolution models. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 29
    facet.materialart.
    Unknown
    Seasonal Evaluation of Rainfall Estimation by four Cumulus Parameterization Schemes and their Sensitivity Analysis (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Sustainable water resources management require scientifically sound information on precipitation, as it plays a key role in hydrological responses in a catchment. In recent years, mesoscale weather models in conjunction with hydrological models have gained great attention as they can provide high resolution downscaled weather variables. Many cumulus parameterization schemes (CPSs) have been developed and incorporated into three-dimensional Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) mesoscale model 5 (MM5). This study has performed a comprehensive evaluation of four CPSs (the Anthes–Kuo, Grell, Betts–Miller and Kain–Fritsch93 schemes) to identify how their inclusion influences the mesoscale model's precipitation estimation capabilities. The study has also compared these four CPSs in terms of variability in rainfall estimation at various horizontal and vertical levels. For this purpose, the MM5 was nested down to resolution of 81km for domain 1 (domain span 21 x 81 km) and 3km for 4 (domain span 16 x 3km) respectively with vertical resolutions at 23, 40 and 53 vertical levels. The study was carried out at the Brue catchment in Southwest England using both the ERA-40 reanalysis data and the land based observation data. The performances of four CPs were evaluated in terms of their ability to simulate the amount of cumulative rainfall in four months in 1995 representing the four seasonal months viz January (winter), March (spring), July (summer) and October (autumn). It is observed that the Anthes–Kuo scheme has produced inferior precipitation values during spring and autumn seasons while simulations during winter and summer were consistently good. The Betts–Miller scheme has produced some reasonable results, particularly at the small scaled domain (3 km grid size) during winter and summer. The KF2 scheme was the best scheme for the larger scale (81 km grid size) domain during winter season at both 23 and 53 vertical levels. This scheme tended to underestimate rainfall for other seasons including the small scale domain (3 km grid size) in the mesoscale. The Grell scheme was the best scheme in simulating rainfall rates, and was found to be superior to other three schemes with consistently better results in all four seasons and different domain scales. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 30
    facet.materialart.
    Unknown
    Spatial scale effect on the upper soil effective parameters of a distributed hydrological model (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Nonlinear dynamics and spatial variability in hydrological systems make difficult the formulation of scaling theories. Therefore, the development of knowledge related to scale effects, scaling techniques, parameterization and linkages of parameters across scales is highly relevant. The main purpose of this work is to analyse the spatial effect of the static storage capacity parameter H u and the saturated hydraulic conductivity parameter k s from microscale (sub-grid level) to mesoscale (grid level) and its implication to the definition of an optimum cell size. These two parameters describe the upper soil water characteristics in the infiltration process conceptualization of the TETIS hydrological model. At microscale, the spatial heterogeneity of H u and k s was obtained generating random parameter fields through probability distribution functions and a spatial dependence model with pre-established correlation lengths. The effective parameters at mesoscale were calculated by solving the inverse problem for each parameter field. Results indicate that the adopted inverse formulation allows transferring the non-linearity of the system from microscale to the mesoscale via non-stationary effective parameters. Their values at each cell and time step are in the range of zero to the mean value of the parameter at microscale. The stochastic simulations showed that the variance of the estimated effective parameters decreases when the ratio between mesoscale cell size and correlation length at microscale increases. For a ratio greater than 1, we found cell sizes having the characteristics of a representative elementary area (REA); in such case, the microscale variability pattern did not affect the system response at mesoscale. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 31
    facet.materialart.
    Unknown
    The Mid-Brunhes Event and West Antarctic ice sheet stability (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: The complex cyclical nature of Pleistocene climate, driven by the evolving orbital configuration of the Earth, is well known but not well understood. A major climatic transition took place at the Mid-Brunhes Event (MBE), ca. 430 ka ago after which the amplitude of the ca.100 ka climate oscillations increased, with substantially warmer interglacials, including periods warmer than present. Recent modelling has indicated that while the timing of these warmer-than-present transient (WPT) events is consistent with southern warming due to a deglaciation-forced slowdown of the Atlantic Meridional Overturning Circulation, the magnitude of warming requires a local amplification, for which a candidate is the feedback of significant West Antarctic Ice Sheet (WAIS) retreat. We here extend this argument, based on the absence of WPTs in the early ice core record (450–800 ka ago), to hypothesize that the MBE could be a manifestation of decreased WAIS stability, triggered by ongoing subglacial erosion. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 32
    facet.materialart.
    Unknown
    Analytical solutions for minimization of energy use for groundwater pumping (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Analytical solutions are obtained for optimization formulations that minimize energy used for groundwater pumping. The formulations choose pumping rates at groundwater wells while insuring that total pumpage meets a specified demand. Such formulations might be appropriate for an urban water supply or a large−scale agricultural irrigation system. Solutions are found by applying stationarity conditions. The solutions produce simple and physically meaningful requirements on drawdowns at each well. Under certain conditions, pumping rates are optimal when the sum of the nonpumping lift and two times the drawdown at each pumping well takes a constant value across the domain. The results are examined for steady and transient conditions. The results are based on only a few assumptions on the modeled system: the response of drawdown with head is linear, and all pumping activity occurs during the same time periods. Implications of these results for well field operation are suggested.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 33
    facet.materialart.
    Unknown
    Pricing for scarcity? An efficiency analysis of increasing block tariffs (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Water pricing schedules often contain significant nonlinearities, such as the increasing block tariff (IBT) structure that is abundantly applied for residential users. The IBT is frequently supported as a good tool for achieving the goals of equity, water conservation, and revenue neutrality but seldom has been grounded on efficiency justifications. In particular, existing literature on water pricing establishes that although efficient schedules will depend on demand and supply characteristics, IBT cannot usually be recommended. In this paper, we consider whether the explicit inclusion of scarcity considerations can strengthen the appeal of IBT. Results show that when both demand and costs react to climate factors, increasing marginal prices may come about as a response to a combination of water scarcity and customer heterogeneity. We derive testable conditions and then illustrate their application through an estimation of Portuguese residential water demand. We show that the recommended tariff schedule hinges crucially on the choice of functional form for demand.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 34
    facet.materialart.
    Unknown
    The influence of ambient light intensity on in situ laser diffractometers (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: In situ laser diffractometers characterize the suspended particle size distribution (PSD) by measuring laser-generated light scattered off small particles over a range of small forward angles. In environments with low particulate concentrations or high ambient light conditions the ratio of natural downwelling sunlight to scattered laser light sensed by the photodetectors is high and measurements are influenced. Here, we evaluate the effect of the ambient light field intensity on measurements made with a Laser In Situ Scattering and Transmissometry (LISST) 100X type B instrument. Paired light-dark scattering distributions are recorded over a range of underwater light intensities in high-turbidity and low-turbidity water. Light measurements displayed large erroneous concentrations of particles in the smallest size bin (1.25–1.48 μm) and showed effects over the full range of the PSD. Ambient light was found to exhibit the same constant distribution over the instrument photodetectors in both water samples, although the magnitude of the response, in laser counts per unit ambient light intensity, was PSD dependent. A technique for postprocessing data to remove the influence of light is presented for moored deployment and vertical profile data collected at Lake Tahoe, California-Nevada, United States. While measurements removed of the light effect were successfully reconstructed, the technique may not be applicable to data where the PSD or the LISST orientation relative to the sun direction change rapidly or when light intensities are high enough to quench the instrument photodetectors. Ambient light was found to have negligible effects on PSD measurements in Lake Tahoe was below intensities of ∼30 W m−2.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 35
    facet.materialart.
    Unknown
    Streamflow generation in a large, alpine watershed in the southern Rocky Mountains of Colorado: Is streamflow generation simply the aggregation of hillslope runoff responses? (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: Spatial and temporal trends in stream chemistry were investigated in a large (1600 km2) alpine watershed in the southern Rocky Mountains of Colorado to help understand mechanisms of streamflow generation. We observed linear increases of concentrations of chemical constituents in streamflow as accumulated drainage area increased along the main channel of Saguache Creek. We tested two conceptual models of streamflow generation against our stream chemistry observations. One model is essentially two-dimensional and treats streamflow generation at the large watershed scale as the aggregation of runoff responses from individual hillslopes, primarily surface and shallow subsurface flow paths. Alternatively, a fully three-dimensional conceptual model treats streamflow generation as being controlled by a distribution of large-scale groundwater flow paths as well as surface and shallow subsurface flow paths. The structure and magnitude of groundwater contributions in streamflow as a function of increasing scale provided a key distinction between these two conceptual models. End-member mixing analysis and measurements of hydraulic head gradients in streambeds were used to quantify basin-scale groundwater contributions to streamflow with increasing spatial scale in the Saguache Creek watershed. Our data show that groundwater contributions are important in streamflow generation at all scales and, more importantly, that groundwater contributions to streamflow do increase with increasing watershed scale. These results favor the three-dimensional conceptual model in which long groundwater flow paths provide a streamflow generation process at large scales that is not operative at smaller scales. This finding indicates that large watersheds may be more than simply the aggregation of hillslopes and small catchments.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 36
    facet.materialart.
    Unknown
    Subsurface characterization of groundwater contaminated by landfill leachate using microbial community profile data and a nonparametric decision-making process (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: Microbial biodiversity in groundwater and soil presents a unique opportunity for improving characterization and monitoring at sites with multiple contaminants, yet few computational methods use or incorporate these data because of their high dimensionality and variability. We present a systematic, nonparametric decision-making methodology to help characterize a water quality gradient in leachate-contaminated groundwater using only microbiological data for input. The data-driven methodology is based on clustering a set of molecular genetic-based microbial community profiles. Microbes were sampled from groundwater monitoring wells located within and around an aquifer contaminated with landfill leachate. We modified a self-organizing map (SOM) to weight the input variables by their relative importance and provide statistical guidance for classifying sample similarities. The methodology includes the following steps: (1) preprocessing the microbial data into a smaller number of independent variables using principal component analysis, (2) clustering the resulting principal component (PC) scores using a modified SOM capable of weighting the input PC scores by the percent variance explained by each score, and (3) using a nonparametric statistic to guide selection of appropriate groupings for management purposes. In this landfill leachate application, the weighted SOM assembles the microbial community data from monitoring wells into groupings believed to represent a gradient of site contamination that could aid in characterization and long-term monitoring decisions. Groupings based solely on microbial classifications are consistent with classifications of water quality from hydrochemical information. These microbial community profile data and improved decision-making strategy compliment traditional chemical groundwater analyses for delineating spatial zones of groundwater contamination.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 37
    facet.materialart.
    Unknown
    Dividing the waters: An empirical analysis of interstate compact allocation of transboundary rivers (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: Legal scholars and jurists have identified several criteria (e.g., hydrology, climate, population, and historical water use) to guide equitable allocation of transboundary rivers among riparian claimants. Are these criteria used in practice, such that a quantitative pattern emerges from actual water-sharing agreements regarding factors affecting allocations? To address this, we study interstate compacts, the principal mechanism for allocating the waters of transboundary rivers within the United States. We develop a georeferenced data set and construct variables representing conditions in state-based watersheds of 14 rivers at the times of compact ratification. A state's water allocation share of a compact serves as the dependent variable, and a set of explanatory variables is derived from legal and political theories. We estimate allocation shares using both ordinary least squares (OLS) and bootstrap regressions, and we apply two alternative specifications of the factors affecting compact allocations, one with and one without political variables. Estimated coefficients on variables for land area, population, prior water use, riparian position, and Congressional committee chair are statistically significant in the OLS regressions. The preferred OLS specification, which includes political variables, provides a good fit (R2 = 0.84). We also find that OLS and bootstrap regressions have a similar ability to predict state allocation shares. We discuss how the results could be used as a reference point in negotiations over new compacts or international river treaties and as a basis to identify existing compacts with statistical outliers.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 38
    facet.materialart.
    Unknown
    Stochastic flux-related analysis of transverse mixing in two-dimensional heterogeneous porous media (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: Transverse mixing of solutes in steady state transport is of utmost importance for assessing mixing-controlled reactions of compounds that are continuously introduced into the subsurface. Classical spatial moments analysis fails to describe mixing because the tortuous streamlines in heterogeneous formations cause plume meandering, squeezing, and stretching, which affect transverse spatial moments even if there is no mass transfer perpendicular to the direction of flow. For transverse solute mixing, however, the decisive process is the exchange of solute mass between adjacent stream tubes. We therefore reformulate the advection-dispersion equation in streamline coordinates (i.e., in terms of the potential and the stream function values) and analyze how flux-related second central moments of plumes increase with dropping hydraulic potential. We compare the ensemble behavior of these second central moments in random two-dimensional heterogeneous flow fields with the moments in an equivalent homogeneous system, thus defining an equivalent effective transverse dispersion coefficient. Unlike transverse macrodispersion coefficients derived by traditional moment analysis, our mixing-relevant, flux-related coefficient does not increase with travel distance. We present closed-form solutions for the mean enhancement of transverse mixing by heterogeneity in two-dimensional isotropic media for linear laws of local-scale transverse dispersion. The mixing enhancement factor increases with the log conductivity variance but remains fairly low. We also evaluate the variance of our cumulative measure of transverse mixing, showing that heterogeneity causes substantial uncertainty of mixing. The analytical expressions are compared to numerical Monte Carlo simulations for various values of log conductivity variance, indicating good agreement with the analytical results at low variability. In the numerical simulations, we also consider nonlinear models of local-scale transverse dispersion.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 39
    facet.materialart.
    Unknown
    Benchmarking quantitative precipitation estimation by conceptual rainfall-runoff modeling (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: Hydrologic modelers often need to know which method of quantitative precipitation estimation (QPE) is best suited for a particular catchment. Traditionally, QPE methods are verified and benchmarked against independent rain gauge observations. However, the lack of spatial representativeness limits the value of such a procedure. Alternatively, one could drive a hydrological model with different QPE products and choose the one which best reproduces observed runoff. Unfortunately, the calibration of conceptual model parameters might conceal actual differences between the QPEs. To avoid such effects, we abandoned the idea of determining optimum parameter sets for all QPE being compared. Instead, we carry out a large number of runoff simulations, confronting each QPE with a common set of random parameters. By evaluating the goodness-of-fit of all simulations, we obtain information on whether the quality of competing QPE methods is significantly different. This knowledge is inferred exactly at the scale of interest—the catchment scale. We use synthetic data to investigate the ability of this procedure to distinguish a truly superior QPE from an inferior one. We find that the procedure is prone to failure in the case of linear systems. However, we show evidence that in realistic (nonlinear) settings, the method can provide useful results even in the presence of moderate errors in model structure and streamflow observations. In a real-world case study on a small mountainous catchment, we demonstrate the ability of the verification procedure to reveal additional insights as compared to a conventional cross validation approach.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 40
    facet.materialart.
    Unknown
    Investigating spatial differentiation of model parameters in a carbon cycle data assimilation system (2011)
    Wiley
    Details
    Publication Date: 2011-06-19
    Description: Better estimates of the net exchange of CO2 between the atmosphere and the terrestrial biosphere are urgently needed to improve predictions of future CO2 levels in the atmosphere. The carbon cycle data assimilation system (CCDAS) offers the capability of inversion, while it is at the same time based on a process model that can be used independent of observational data. CCDAS allows the assimilation of atmospheric CO2 concentrations into the terrestrial biosphere model BETHY, constraining its process parameters via an adjoint approach. Here, we investigate the effect of spatial differentiation of a universal carbon balance parameter of BETHY on posterior net CO2 fluxes and their uncertainties. The parameter, β, determines the characteristics of the slowly decomposing soil carbon pool and represents processes that are difficult to model explicitly. Two cases are studied with an assimilation period of 1979 to 2003. In the base case, there is a separate β for each plant functional type (PFT). In the regionalization case, β is differentiated not only by PFT, but also according to each of 11 large continental regions as used by the TransCom project. We find that the choice of spatial differentiation has a profound impact not only on the posterior (optimized) fluxes and their uncertainties, but even more so on the spatial covariance of the uncertainties. Differences are most pronounced in tropical regions, where observations are sparse. While regionalization leads to an improved fit to the observations by about 20% compared to the base case, we notice large spatial variations in the posterior net CO2 flux on a grid cell level. The results illustrate the need for universal process formulations in global-scale atmospheric CO2 inversion studies, at least as long as the observational network is too sparse to resolve spatial fluctuations at the regional scale.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 41
    facet.materialart.
    Unknown
    Dry deposition of ammonia gas drives species change faster than wet deposition of ammonium ions: evidence from a long-term field manipulation (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Although the effects of atmospheric nitrogen deposition on species composition are relatively well known, the roles of the different forms of nitrogen, in particular gaseous ammonia (NH 3 ), have not been tested in the field. Since 2002, we have manipulated the form of N deposition to an ombrotrophic bog, Whim, on deep peat in southern Scotland, with low ambient N (wet + dry = 8 kg N ha −1 y −1 ) and S (4 kg S ha −1 y −1 ) deposition. A gradient of ammonia (NH 3 , dry N), from 70 kg N ha −1 y −1 down to background, 3-4 kg N ha −1 y −1 was generated by free air release. Wet ammonium (NH 4 + , wet N) was provided to replicate plots in a fine rainwater spray (NH 4 Cl at +8, +24, +56 kg N ha −1 y −1 ). Automated treatments are coupled to meteorological conditions, in a globally unique, field experiment. Ammonia concentrations were converted to NH 3 -N deposition (kg N ha −1 ) using a site / vegetation specific parameterization. Within 3 years, exposure to relatively modest deposition of NH 3 , 20-56 kg NH 3 -N ha −1 y −1 led to dramatic reductions in species cover, with almost total loss of Calluna vulgaris , Sphagnum capillifolium and Cladonia portentosa . These effects appear to result from direct foliar uptake and interaction with abiotic and biotic stresses, rather than via effects on the soil. Additional wet N by contrast, significantly increased Calluna cover after 5 years at the 56 kg N dose, but reduced cover of Sphagnum and Cladonia . Cover reductions caused by wet N were significantly different from and much smaller than those caused by equivalent dry N doses. The effects of gaseous NH 3 described here, highlight the potential for ammonia to destroy acid heathland and peat bog ecosystems. Separating the effects of gaseous ammonia and wet ammonium deposition, for a peat bog, have significant implications for regulatory bodies and conservation agencies.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 42
    facet.materialart.
    Unknown
    Nestedness patterns and the dual nature of community reassembly in California streams: a multivariate permutation-based approach. (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Many factors contribute to the non-random processes of extinctions and invasions that are changing the structure of ecological communities worldwide. These factors include the attributes of the species, their abiotic environment, and the interactions and feedbacks between them. The relative importance of these factors has been difficult to quantify. We used nested subset theory and a novel permutation-based extension of gradient analysis to disentangle the direct and indirect pathways by which these factors affect the metacommunity structure of freshwater fishes inhabiting the streams tributary to the San Francisco Bay. Our analyses provide quantitative measures of how species and stream attributes may influence extinction vulnerability and invasion risk, highlight the need for considering the multiple interacting drivers of community change concurrently, and indicate that the ongoing disassembly and assembly of Bay Area freshwater fish communities are not fully symmetric processes. Fish communities are being taken apart and put back together in only partially analogous trajectories of extinction and invasion for which no single explanatory hypothesis is sufficient. Our study thereby contributes to the forecasting of continued community change and its effects on the functioning of freshwater ecosystems.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 43
    facet.materialart.
    Unknown
    Impacts of atmospheric nutrient deposition on marine productivity: Roles of nitrogen, phosphorus, and iron (2011)
    Wiley
    Details
    Publication Date: 2011-06-23
    Description: Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition or mixing from deeper waters, and these nutrients drive nitrogen and carbon fixation. To evaluate the importance of atmospheric deposition, we estimate marine nitrogen and carbon fixation from present-day simulations of atmospheric deposition of nitrogen, phosphorus, and iron. These are compared with observed rates of marine nitrogen and carbon fixation. We find that Fe deposition is more important than P deposition in supporting N fixation. Estimated rates of atmospherically supported carbon fixation are considerably lower than rates of marine carbon fixation derived from remote sensing, indicating the subsidiary role atmospheric deposition plays in total C uptake by the oceans. Nonetheless, in high-nutrient, low-chlorophyll areas, the contribution of atmospheric deposition of Fe to the surface ocean could account for about 50% of C fixation. In marine areas typically thought to be N limited, potential C fixation supported by atmospheric deposition of N is only ∼1%–2% of observed rates. Although these systems are N-limited, the amount of N supplied from below appears to be much larger than that deposited from above. Atmospheric deposition of Fe has the potential to augment atmospherically supported rates of C fixation in N-limited areas. In these areas, atmospheric Fe relieves the Fe limitation of diazotrophic organisms, thus contributing to the rate of N fixation. The most important uncertainties in understanding the relative importance of different atmospheric nutrients are poorly understood speciation and solubility of Fe as well as the N:Fe ratio of diazotrophic organisms.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 44
    facet.materialart.
    Unknown
    Long-term spruce budworm outbreak dynamics reconstructed from subfossil trees (2011)
    Wiley
    Details
    Publication Date: 2011-06-23
    Description: We reconstructed the long-term spruce budworm (SBW) ( Choristoneura fumiferana Clem.) outbreak dynamics in the boreal forest of Quebec (Canada) using a dendrochronological approach with subfossil trees. Although the majority of the excavated wood belonging to the genus Picea could potentially reveal the past activity of spruce budworms in the tree rings, very few were cross-dated due to a lack of marker rings. All cross-dated trees were found within a particular zone of the peat bogs and the floating chronology was radiocarbon dated to ca. 5.1 cal ka BP. The results presented in this study suggest that the dynamics of SBW outbreaks in the studied area fluctuated during the last millennia and that severe outbreaks as observed during the 20th century seldom occurred in that part of the boreal forest since the end of the last glaciation. These results are in agreement with observations from other parts of eastern North America. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 45
    facet.materialart.
    Unknown
    Invited perspective: Why I am an optimist (2011)
    Wiley
    Details
    Publication Date: 2011-06-25
    Description: I address a range of topics that provide the sociopolitical-technological setting for my professional life. I discuss some influential features of post–World War II world geopolitics, landmark technological developments of that era, and the resulting follow-up technologies that have made it possible to approach various problems in hydrology and water resources. I next address societal needs that have driven developments in hydrology and water resources engineering and follow with a discussion of the modern foundations of our science and what I think are the principal issues in hydrology. I pose three community challenges that when accomplished should advance hydrologic science: data network needs for improving the water budgets at all scales, characterizing subsurface water flow paths, and the information archiving and mining needs from instruments that will generate substantially richer data detail than have been used for most hydrologic work to the present. I then discuss several hydrologic and water resource risk-based decision issues that matter to society to illustrate how such risks have been addressed successfully in the past. I conclude with a long-term community “grand challenge,” the coupled modeling of the ocean-atmosphere-landform hydrologic cycle for the purpose of long–lead time hydrologic prediction.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 46
    facet.materialart.
    Unknown
    An improved glacial isostatic adjustment model for the British Isles (2011)
    Wiley
    Details
    Publication Date: 2011-06-25
    Description: The glacial isostatic adjustment (GIA) of the British Isles is of interest due to the constraints that can be provided on key model parameters such as the global meltwater signal, local ice sheet history and viscoelastic earth structure. A number of recent studies have modelled relative sea-level (RSL) data from this region to constrain model parameters. As indicated in these studies, the sensitivity of these data to both local and global parameters results in a highly non-unique problem. This study aims to address this inherent non-uniqueness by combining a previously published British–Irish ice model that is based on the most recent geomorphological data with a new global ice sheet model that provides an accurate prediction of eustatic sea-level change. In addition, constraints from Global Positioning System (GPS) measurements of present-day vertical land motion are considered alongside the entirety of RSL data from both Great Britain and Ireland. A model solution is found that provides a high-quality fit to both the RSL data and the GPS data. Within the range of earth viscosity values considered, the optimal data model fits were achieved with a relatively thin lithosphere (71 km), upper mantle viscosities in the range 4–6 × 10 20 Pa s and lower mantle viscosities ≥ 3 × 10 22 Pa s. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 47
    facet.materialart.
    Unknown
    A well-established Early–Middle Pleistocene marine sequence on south-east Zakynthos island, western Greece: Magneto-biostratigraphic constraints and palaeoclimatic implications (2011)
    Wiley
    Details
    Publication Date: 2011-06-25
    Description: The chronostratigraphy of a long, onshore Early–Middle Pleistocene marine sedimentary sequence on the south-east part of Zakynthos island, Greece, is presented. Correlation of the succession with the isotope record of Ocean Drilling Program Site 963 reveals the combined influence of tectonics and eustacy in this area. The sequence is divided into three formations by two main unconformities that apparently relate to sea-level lowstands associated with two major northern hemisphere glaciations, those of marine isotope stages (MIS) 22 and 12. The Zakynthos sequence in many ways is comparable with the Italian Valle di Manche section. Magnetostratigraphic and rock magnetic analyses, supported by biostratigraphy, document the position of the Matuyama/Brunhes Chron boundary (0.77 Ma), the top and base of the Jaramillo Subchron (0.99–1.07 Ma), the Cobb Mountain Subchron (1.173–1.185 Ma) and the top of the Olduvai Subchron (1.78 Ma). The underlying strata are constrained exclusively by detailed nannofossil biostratigraphy extending at least to the lowermost Pleistocene at around 2.54 Ma and therefore certainly incorporating the base of the Olduvai Subchron (1.95 Ma) and possibly the Gauss/Matuyama Chron boundary (2.58 Ma). In addition, a remarkable increase in sedimentation rate (from 3.2 and 28 cm ka −1 to 167 cm ka −1 ) and hence resolution above the Matuyama/Brunhes boundary (Middle Pleistocene) reveals one short-lived magnetic excursion, possibly 17a (0.66 Ma), within the normal polarity Brunhes Chron. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 48
    facet.materialart.
    Unknown
    Using a climatic niche model to predict the direct and indirect impacts of climate change on the distribution of Douglas-fir in New Zealand (2011)
    Wiley
    Details
    Publication Date: 2011-06-29
    Description: Climate change is likely to have major impacts on the distribution of planted and natural forests. Here we demonstrate how a process-based niche model (CLIMEX) can be extended to project globally the potential habitat suitable for Douglas-fir. Within this distribution we use CLIMEX to predict abundance of the pathogen P haeocryptopus gaeumannii and severity of its associated foliage disease, Swiss needle cast. The distribution and severity of the disease, which can strongly reduce growth rate of Douglas-fir, is closely correlated with seasonal temperatures and precipitation. This model is used to project how climate change during the 2080s may alter the area suitable for Douglas-fir plantations within New Zealand. The climate change scenarios used indicate that the land area suitable for Douglas-fir production in the North Island will be reduced markedly from near 100% under current climate to 36 – 64% of the total land area by 2080's. Within areas shown to be suitable for the host in the North Island, four of the six climate change scenarios predict substantial increases in disease severity that will make these regions at best marginal for Douglas-fir by the 2080's. In contrast, most regions in the South Island are projected to sustain relatively low levels of disease, and remain suitable for Douglas-fir under climate change over the course of this century.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 49
    facet.materialart.
    Unknown
    Radar characteristics of continental, coastal, and maritime convection observed during AMMA/NAMMA (2011)
    Wiley
    Details
    Publication Date: 2011-06-09
    Description: Ground-based radar observations at three distinct geographical locations in West Africa along a common latitudinal band (Niamey, Niger (continental), Kawsara, Senegal (coastal), and Praia, Republic of Cape Verde (maritime)) are analyzed to determine convective system characteristics in each domain during a 29-day period in 2006. Ancillary datasets provided by the African Monsoon Multidisciplinary Analyses (AMMA) and NASA-AMMA (NAMMA) field campaigns are also used to place the radar observations in context. Results show that the total precipitation is dominated by propagating mesoscale convective systems. Convective characteristics vary according to environmental properties, such as vertical shear, CAPE, and the degree of synoptic forcing. Data are bifurcated based on the presence or absence of African easterly waves. In general, African easterly waves appear to enhance mesoscale convective system strength characteristics (e.g. total precipitation and vertical reflectivity profiles) at the inland and maritime sites. The wave regime also resulted in an increased population of the largest observed mesoscale convective systems observed near the coast, which led to an increase in stratiform precipitation. Despite this increase, differentiation of convective strength characteristics was less obvious between wave and no-wave regimes at the coast. Owing to the propagating nature of these advecting mesoscale convective systems, interaction with the regional thermodynamic and dynamic environment appears to result in more variability than enhancements due to the wave regime, independent of location. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 50
    facet.materialart.
    Unknown
    Spatial scale effect on seasonal streamflows in permafrost catchments on the Qinghai-Tibet Plateau (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: The scale issue is of central concern in hydrological processes to understand the potential upscaling or downscaling methodologies, and to develop models for scaling the dominant processes at different scales and in different environments. In this study, a typical permafrost watershed in the Qinghai-Tibet Plateau was selected. Its hydrological processes were monitored for four years from 2004 to 2008; measuring the effects of freezing and thawing depth of active soil layers on runoff processes. To identify the nature and cause of variation in the runoff response in different size catchments, catchments ranging from 1.07 km 2 to 112 km 2 were identified in the watershed. The results indicated that the variation of runoff coefficients showed a “V” shape with increasing catchment size during the spring and autumn seasons, when the active soil was subjected to thawing or freezing processes. A two-stage method was proposed to create runoff scaling models to indicate the effects of scale on runoff processes. In summer, the scaling transition model followed an exponential function for mean daily discharge, whereas the scaling model for flood flow exhibited a linear function. In autumn, the runoff process transition across multiple scales followed an exponential function with air temperature as the driving factor. These scaling models demonstrate relatively high simulation efficiency and precision, and provide a practical way for upscaling or downscaling runoff processes in a medium-size permafrost watershed. For permafrost catchments of this scale, the results show that the synergistic effect of scale and vegetation cover is an important driving factor in the runoff response. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 51
    facet.materialart.
    Unknown
    Regional Flood Frequency Analysis using Bayesian Generalized Least Squares: A Comparison between Quantile and Parameter Regression Techniques (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Regression based regional flood frequency analysis (RFFA) methods are widely adopted in hydrology. This paper compares two regression based RFFA methods using a Bayesian Generalized Least Squares (GLS) modelling framework; the two are quantile regression technique (QRT) and parameter regression technique (PRT). In this study, the QRT focuses on the development of prediction equations for a flood quantile in the range of 2 to 100 years average recurrence intervals (ARI), while the PRT develops prediction equations for the first three moments of the log Pearson Type 3 (LP3) distribution, which are the mean, standard deviation and skew of the logarithms of the annual maximum flows; these regional parameters are then used to fit the LP3 distribution to estimate the desired flood quantiles at a given site. It has been shown that using a method similar to stepwise regression and by employing a number of statistics such as the model error variance, average variance of prediction, Bayesian information criterion and Akaike information criterion, the best set of explanatory variables in the GLS regression can be identified. In this study, a range of statistics and diagnostic plots have been adopted to evaluate the regression models. The method has been applied to 53 catchments in Tasmania, Australia. It has been found that catchment area and design rainfall intensity are the most important explanatory variables in predicting flood quantiles using the QRT. For the PRT, a total of four explanatory variables were adopted for predicting the mean, standard deviation and skew. The developed regression models satisfy the underlying model assumptions quite well; of importance, no outlier sites are detected in the plots of the regression diagnostics of the adopted regression equations. Based on ‘one-at-a-time cross validation’ and a number of evaluation statistics, it has been found that for Tasmania the QRT provides more accurate flood quantile estimates for the higher ARIs while the PRT provides relatively better estimates for the smaller ARIs. The RFFA techniques presented here can easily be adapted to other Australian states and countries to derive more accurate regional flood predictions. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 52
    facet.materialart.
    Unknown
    A Synthetic Hydrologic-Response Dataset (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Synthetic data have long been employed in hydrology for model development and testing. The objective of this study was to generate a synthetic dataset of hydrologic response with higher spatial and temporal resolution than could presently be obtained in the field, spanning a longer period than the typical duration of monitoring campaigns in experimental catchments. The synthetic dataset was generated for a rangeland catchment with the Integrated Hydrology Model (InHM), and is presented for future use by the community. The InHM boundary-value problem is based upon the previously reported hypothetical reality of Tarrawarra-like hydrologic response. Whereas the emphasis in developing the hypothetical reality was on parameterizing InHM to reproduce observations from the Tarrawarra catchment, the emphasis in generating the synthetic dataset is on developing an internally valid hydrologic-response dataset that extends well beyond the period of observations at Tarrawarra. The synthetic dataset spans eleven years of continuous forcing and response data (e.g., integrated response, distributed fluxes, state variable dynamics). The dataset should be useful for a wide range of problems including evaluation of simple rainfall runoff modeling techniques, design of measurement networks, development of data-assimilation algorithms, and studies on information theory. The dataset is available at: ftp://pangea.stanford.edu/pub/loague/. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 53
    facet.materialart.
    Unknown
    Diagnostic and impact studies of a wavelet formulation of background-error correlations in a global model (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: A wavelet formulation on the sphere is being considered for modelling heterogeneous background-error correlations for the Météo-France global numerical weather prediction (NWP) model. This approach is compared with the operational spectral formulation, which is horizontally homogeneous to a large extent. Diagnostic studies have been conducted to examine geographical variations of three-dimensional correlations over the whole globe. Results indicate that the contrast between relatively broad horizontal correlations in the Tropics and sharp ones in midlatitudes is well represented by the wavelet formulation. Heterogeneities in vertical correlations are also better captured in the wavelet approach than in the spectral one, with visible changes as functions of e.g. latitude and land/sea contrasts. In addition, wavelet-based correlation estimates are shown to be partly sensitive to the choice of the calibration period. The impact of the wavelet formulation on the forecast quality has been investigated during a three-week calibration period, and also during the following three weeks. While the impact of the wavelet formulation is globally positive during the two periods, it tends to be more spectacular during the calibration time interval, as expected. These results indicate that an on-line calibration should be considered in the future, in order to exploit fully the ability of wavelets to extract correlation heterogeneities from ensemble data. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 54
    facet.materialart.
    Unknown
    An evaluation of FY-3A satellite data for numerical weather prediction (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: FY-3A, launched in May 2008, is the first in a series of seven polar-orbiting meteorological satellites due to be launched by China's Meteorological Administration in the period leading up to 2020. The FY-3A payload includes four instruments of particular interest for numerical weather prediction (NWP): microwave temperature and humidity sounders, a microwave imager, and an infrared sounder. The main features of these instruments are described. Data from the calibration–validation phase of the FY-3A mission were introduced into the ECMWF Integrated Forecasting System in order to assess the data quality and the influence of the data on analyses and forecasts. An analysis of first-guess departures has shown the data to be of good quality overall. Several issues with instrument performance and ground segment processing have been identified. The most serious of these are: uncertainties in the temperature sounder passbands on-orbit, orbital biases in the infrared instrument affecting the highest peaking channels, and scan biases in the microwave humidity sounder. Variational bias correction partially corrects for these errors, but more work remains to be done to correct the problems before the full benefit of the data is realised. In observing system experiments, the FY-3A instruments, both individually and as a package, show considerable skill when added to observation depleted control experiments. When added to a full observing system, the impacts are neutral to slightly positive, as expected. These initial results are encouraging and build confidence that the following series of FY-3 instruments will be widely used in NWP data assimilation systems. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 55
    facet.materialart.
    Unknown
    Impact of climate change on the water resources of the eastern Mediterranean and Middle East region: Modeled 21st century changes and implications (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: The likely effects of climate change on the water resources of the eastern Mediterranean and Middle East region are investigated using a high-resolution regional climate model (PRECIS) by comparing precipitation simulations of 2040–2069 and 2070–2099 with 1961–1990. The simulations show about a 10% decline in precipitation across the region by both the middle and the end of the century, with considerable variation between countries and international river basins. Results suggest that per capita water resources will not change particularly significantly in southeastern Europe, where they are relatively plentiful and population growth is minimal. However, in much of the Middle East, climate change coupled with population growth is likely to reduce per capita water resources considerably. This will inevitably result in major social, economic, and environmental change in the region. Countries where the required adaptation is likely to be particularly challenging include Turkey and Syria because of the large agricultural workforces, Iraq because of the magnitude of the change and its downstream location, and Jordan because of its meager per capita water resources coupled with limited options for desalination. If the internal water footprint of the region declines in line with precipitation but the total water footprint of the region increases in line with population, then by midcentury, as much as half the total water needs of the region may need to be provided through desalination and imported in the form of virtual water.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 56
    facet.materialart.
    Unknown
    Theoretical constraints to gully erosion research: time for a re-evaluation of concepts and assumptions? (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Gullies are conceptualized in the literature as essentially fluvial forms with dimensional boundaries arbitrarily defined between rills and river channels. This notion is incompatible with the existing variability as to form and process, as mass movements frequently exert a fundamental control on gully initiation and expansion, to the point of features outgrowing their original contributing area. The inability of a conceptual framework to incorporate existing observations inevitably constrains methodologies and research results. In this commentary, several examples of published results are contrasted to the prevailing assumption of an essentially fluvial nature with the purpose of encouraging discussion on the need for a revised conceptual framework in gully erosion research. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 57
    facet.materialart.
    Unknown
    Precessional forcing of tropical vegetation carbon storage (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Since the Mid Pleistocene Revolution, which occurred about one million years ago, global temperatures have fluctuated with a quasi-periodicity of ca. 100 ka. The pattern of past change in the extent of woodlands, and therefore by inference vegetation carbon storage, has been demonstrated to have a strong positive link with this global temperature change at high and mid latitudes. However, understanding of climate systems and ecosystem function indicates that the pattern of woodland change at low latitudes may follow a fundamentally different pattern. We present output from the intermediate complexity model GENIE-1, comprising a single transient simulation over the last 800 ka and a 174-member ensemble of 130 ka transient simulations over the last glacial cycle. These simulations suggest that while vegetation carbon storage in mid–high northern latitudes robustly follows the characteristic ca. 100 ka cycle, this signal is not a robust feature of tropical vegetation, which is subject to stronger direct forcing by the precessional (21 ka) orbital cycle (albeit with a highly uncertain response). We conclude that the correlation of palaeoenvironmental records from low latitudes with global temperature change must be done with caution. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 58
    facet.materialart.
    Unknown
    Dynamics of Murray-Darling floodplain forests under multiple stressors: The past, present, and future of an Australian icon (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: We review the human actions, proximal stressors and ecological responses for floodplain forests Australia's largest river system—the Murray-Darling Basin. A conceptual model for the floodplain forests was built from extensive published information and some unpublished results for the system, which should provide a basis for understanding, studying and managing the ecology of floodplains that face similar environmental stresses. Since European settlement, lowlands areas of the basin have been extensively cleared for agriculture and remnant forests heavily harvested for timber. The most significant human intervention is modification of river flows, and the reduction in frequency, duration and timing of flooding, which are compounded by climate change (higher temperatures and reduced rainfall) and deteriorating groundwater conditions (depth and salinity). This has created unfavorable conditions for all life-history stages of the dominant floodplain tree (Eucalyptus camaldulensis Dehnh.). Lack of extensive flooding has led to widespread dieback across the Murray River floodplain (currently 79% by area). Management for timber resources has altered the structure of these forests from one dominated by large, widely spreading trees to mixed-aged stands of smaller pole trees. Reductions in numbers of birds and other vertebrates followed the decline in habitat quality (hollow-bearing trees, fallen timber). Restoration of these forests is dependent on substantial increases in the frequency and extent of flooding, improvements in groundwater conditions, re-establishing a diversity of forest structures, removal of grazing and consideration of these interacting stressors.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 59
    facet.materialart.
    Unknown
    Snow microphysical observations in shallow mixed-phase and deep frontal Arctic cloud systems (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: Snow particle size distributions (particle size 〉400 µm) in the western Arctic measured with in situ aircraft instrumentation during the Surface Heat Budget of the Arctic/First ISCCP Regional Experiment - Arctic Clouds Experiment and Mixed-Phase Arctic Cloud Experiment are analysed. Three cases of shallow, precipitating mixed-phase boundary-layer clouds and two cases of deep, precipitating frontal clouds are examined. Overall, the shallow cases had much lower values of particle concentration and ice water content than the deep cases, indicating large differences in ice initiation and growth between these regimes. Within a given case for both the shallow and deep frontal systems, and for the dataset as a whole, crystal concentration had little correlation with temperature (height), despite an active aggregation process that was indicated by large aggregates (〉5 mm) observed in four out of the five cases. Exponential size distributions are fitted to the observations, allowing a direct comparison with the snow particle size distributions that are represented with exponential functions in many bulk microphysics schemes used in weather and climate models. Values of the fitted intercept parameter N 0 are generally 2–10 times smaller for the shallow compared to the deep frontal cases as a result of differences in crystal concentration between these regimes. Values of N 0 ∼ 10 7 m −4 specified for snow in many bulk microphysics schemes are broadly consistent with fitted N 0 for the deep cases but larger than values for the shallow cases. The deep frontal cases also exhibit a relationship between N 0 and temperature consistent with previous observations of midlatitude frontal systems. However, there are no consistent differences in N 0 between the shallow and deep cases when partitioned by ice water content. Fitted values of slope parameter λ for the shallow and deep cases are generally consistent with previous studies of lower-latitude cloud systems. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 60
    facet.materialart.
    Unknown
    Tropical cyclones, global climate change and the role of Quaternary studies (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: The number and types of late Quaternary records of tropical cyclones (TCs) and temperate storms have been increasing globally over the past 10 years. There are now numerous such records for the Atlantic Ocean (USA) and Gulf of Mexico and Caribbean Sea, South Pacific Ocean, and a fewer number from the northwest Pacific and Indian Ocean regions. The most obvious characteristic of these records is that many reveal extended alternating periods of greater and lesser TC activity over the past 6000 years. The length of these phases of relative inactivity and greater activity depends on the chronological resolution of the record, with the coarser-resolution ones displaying multi-century to millennial-scale episodes and the high-resolution records displaying decadal to centennial-scale oscillations. In several instances the likely causes of these alternating periods of TC behaviour have been attributed to different phases of climate when El Niños and La Niñas dominated or to longer-term variations in sea surface temperatures and possibly solar forcing. The picture emerging from these records is that TC behaviour is not entirely stochastic over the long term and that any simulations of long-term TC behaviour need to account for these climatic influences. Incorporation of these observations, and the many more needed, is important for understanding the future behaviour of TCs. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0267-8179
    Electronic ISSN: 1099-1417
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 61
    facet.materialart.
    Unknown
    A relationship between the aerodynamic and physical roughness of winter sea ice (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: A bulk flux algorithm predicts the turbulent surface fluxes of momentum and sensible and latent heat from mean measured or modelled meteorological variables. The bulk flux algorithm resulting from data collected over winter sea ice during SHEBA, the experiment to study the Surface Heat Budget of the Arctic Ocean, failed, however, in its first trial to predict the turbulent momentum flux over sea ice in the Antarctic. This result suggests that the main parameter for predicting the momentum flux, the aerodynamics roughness length z 0 , does not respond just to the friction velocity, as in the SHEBA algorithm, but is closely related to the physical roughness of snow-covered sea ice and may need to be site-specific. I investigate this idea with simultaneous measurements of z 0 and the physical roughness of the surface, ξ , at Ice Station Weddell. The metric ξ derives from surveys of surface elevation and is related to but always less than the standard deviation in surface elevation. On combining the z 0 – ξ pairs from Ice Station Weddell with similar data obtained over Arctic sea ice, I show that the Arctic and Antarctic z 0 – ξ data lie along a continuum such that measuring ξ could provide a means for estimating a site-specific z 0 for any global sea ice surface. Backscatter data from satellite-borne synthetic aperture radar might provide a remotely sensed estimate of ξ . Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 62
    facet.materialart.
    Unknown
    Steps toward “useful” hydroclimatic scenarios for water resource management in the Murray-Darling Basin (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: There is currently a distinct gap between what climate science can provide and information that is practically useful for (and needed by) natural resource managers. Improved understanding, and model representations, of interactions between the various climate drivers (both regional and global scale), combined with increased knowledge about the interactions between climate processes and hydrological processes at the regional scale, is necessary for improved attribution of climate change impacts, forecasting at a range of temporal scales and extreme event risk profiling (e.g., flood, drought, and bushfire). It is clear that the science has a long way to go in closing these research gaps; however, in the meantime water resource managers in the Murray-Darling Basin, and elsewhere, require hydroclimatic projections (i.e., seasonal to multidecadal future scenarios) that are regionally specific and, importantly, take into account the impacts, and associated uncertainties, of both natural climate variability and anthropogenic change. The strengths and weaknesses of various approaches for supplying this information are discussed in this paper.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 63
    facet.materialart.
    Unknown
    A simple framework for relating variations in runoff to variations in climatic conditions and catchment properties (2011)
    Wiley
    Details
    Publication Date: 2011-06-21
    Description: We use the Budyko framework to calculate catchment-scale evapotranspiration (E) and runoff (Q) as a function of two climatic factors, precipitation (P) and evaporative demand (Eo = 0.75 times the pan evaporation rate), and a third parameter that encodes the catchment properties (n) and modifies how P is partitioned between E and Q. This simple theory accurately predicted the long-term evapotranspiration (E) and runoff (Q) for the Murray-Darling Basin (MDB) in southeast Australia. We extend the theory by developing a simple and novel analytical expression for the effects on E and Q of small perturbations in P, Eo, and n. The theory predicts that a 10% change in P, with all else constant, would result in a 26% change in Q in the MDB. Future climate scenarios (2070–2099) derived using Intergovernmental Panel on Climate Change AR4 climate model output highlight the diversity of projections for P (±30%) with a correspondingly large range in projections for Q (±80%) in the MDB. We conclude with a qualitative description about the impact of changes in catchment properties on water availability and focus on the interaction between vegetation change, increasing atmospheric [CO2], and fire frequency. We conclude that the modern version of the Budyko framework is a useful tool for making simple and transparent estimates of changes in water availability.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 64
    facet.materialart.
    Unknown
    Flow to partially penetrating wells in unconfined heterogeneous aquifers: Mean head and interpretation of pumping tests (2011)
    Wiley
    Details
    Publication Date: 2011-06-21
    Description: A partially penetrating well of length Lw and radius Rw starts to pump at constant discharge Qw at t = 0 from an unconfined aquifer of thickness D. The aquifer is of random and stationary conductivity characterized by KG (geometric mean), σY2 (log conductivity variance), and I and Iv (the horizontal and vertical integral scales). The flow problem is solved under a few simplifying assumptions commonly adopted in the literature for homogeneous media: Rw/Lw $\ll$ 1, linearization of the free surface condition, and constant drainable porosity n. Additionally, it is assumed that Rw/I 〈 1 and Lw/Iv $\gg$ 1 (to simplify the well boundary conditions) and that a first-order approximation in σY2 (extended to finite σY2 on a conjectural basis) is adopted. The solution is obtained for the mean head field $\langle$H(R, z, t)$\rangle$ and the associated water table equation. The main result of the analysis is that the flow domain can be divided into three zones for $\langle$H$\rangle$: (1) the neighborhood of the well R $\ll$ I, where $\langle$H$\rangle$ = (Qw/LwKA)h0(R, z, tKefuv/nD), with h0 being the zero-order solution pertaining to a homogeneous and isotropic aquifer, KA being the conductivity arithmetic mean, and Kefuv being the effective vertical conductivity in mean uniform flow, (2) an exterior zone R ⪆ I in which $\langle$H$\rangle$ = (Qw/LwKefuh)h0(R$\sqrt{K_{efuv}/K_{efuh}}$, z, tKefuv/nD), with Kefuh being the horizontal effective conductivity, and (3) an intermediate zone in which the solution requires a few numerical quadratures, not carried out here. The application to pumping tests reveals that identification of the aquifer parameters for homogeneous and anisotropic aquifers by commonly used methods can be applied for the drawdown measured in an observation well of length Low $\gg$ Iv (to ensure exchange of space and ensemble head averages) in the second zone in order to identify Kefuh, Kefuv, and n. In contrast, the use of the drawdown in the well (first zone) leads to an overestimation of Kefuh by the factor KA/Kefuh.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 65
    facet.materialart.
    Unknown
    Variability in erosion rates related to the state of landscape transience, the semi-arid Chilean Andes (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: We quantify erosion rates in the higher sectors of the Huasco Valley, in the Main Cordillera of the semi-arid Andes of Chile, using elevation differences between three successive geomorphic markers (pediments and paleo-valleys) and the present day valley. Available Ar-Ar ages of Neogene pediments are used to estimate mean erosion rates for the three periods (16 to 13 My, 13 to 8 My, and following 8 My). The landscape of the Huasco Valley is in a transient state, as indicated by well-preserved pediment surfaces in interfluves, valleys deeply incised by fluvial and glacial erosion and scarped head-valleys that represent the current knickzones. Higher erosion rates (45-75 m/My) are calculated for the more recent period (〈8 My) during which deep incision developed compared to previous periods (6-31 m/My). Quantitative data indicate that glaciers had a much higher erosional capability than fluvial activity in the higher sectors of the Main Cordillera. Comparison with erosion rates calculated in other drainage basins of the Chilean Andes suggests that the variability of erosion rates depends on the landscape's transient erosive state. The landscape's geomorphologic response to the uplift of the Main Cordillera results in the retreat of a knickzone, for which retreat velocity depends on precipitation rate pattern and glacial erosion intensity. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 66
    facet.materialart.
    Unknown
    Nearshore human interventions reverse patterns of decline in lake calcium budgets in central Ontario as demonstrated by mass-balance analyses (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Calcium (Ca) has declined to levels threatening aquatic biota in lakes on the eastern Canadian Shield. Predictive models for future changes in lake Ca are generally based on catchment-scale studies, but these models rarely account for unmeasured sources of Ca supply that are common in the nearshore areas of developed lakes. In this study we utilize up to 29 years of hydrological and water chemistry data for three lakes in central Ontario that differ in degree of human intervention to demonstrate that shoreline development may exert large effects on Ca mass balances. In the relative absence of shoreline development, Red Chalk Lake exhibited what we consider to be the normal response, a reduction in Ca load from the catchment over the last three decades, leading to a reduction in lake export and lake Ca concentration. Calcium load, export, and lake water Ca concentration also fell in Harp Lake, but less than in Red Chalk Lake, because Ca loads were elevated by human activities in Harp Lake's moderately developed shoreline area. By contrast, Dickie Lake experienced an exceptional change in Ca dynamics: both export and lake concentrations rose because of elevated load from the shoreline area linked to the use of dust suppressants on gravel roads. Reductions in both stream Ca concentration and flow volume have led to calcium decline in streams and lakes. Long-term soil acidification processes and climatic variability with its link to hydrology can explain the general pattern of Ca decline in lakes on the south-central Canadian Shield. However, given the widespread lakeshore development and use of dust suppressants on gravel roads, predictions of lake Ca levels need to take into account nearshore activities, especially those that augment rates of Ca supply.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 67
    facet.materialart.
    Unknown
    A test of a field-based 15N-nitrous oxide pool dilution technique to measure gross N2O production in soil (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Soils are both a major source and sink of nitrous oxide (N 2 O), but the proportion of soil N 2 O production released to the atmosphere (termed the N 2 O yield) is poorly constrained due to the difficulty in measuring gross N 2 O production. The quantification of gross N 2 O fluxes would greatly improve our ability to predict N 2 O dynamics across the soil-atmosphere interface. We report a new approach, the 15 N 2 O pool dilution technique, to measure rates of gross N 2 O production and consumption under laboratory and field conditions. In the lab, gross N 2 O production and consumption compared well between the 15 N 2 O pool dilution and acetylene inhibition methods whereas the 15 NO 3 - tracer method measured significantly higher rates. In the field, N 2 O emissions were not significantly affected by increasing chamber headspace concentrations up to 100 ppb 15 N 2 O. The pool dilution model estimates of 14 N 2 O and 15 N 2 O concentrations as well as net N 2 O fluxes fit observed data very well, suggesting that the technique yielded robust estimates of gross N 2 O production. Estimated gross N 2 O consumption rates were underestimated relative to rates calculated as the difference between gross and net N 2 O production rates, possibly due to heterogeneous and/or inadequate tracer diffusion to deeper layers in the soil profile. Gross N 2 O production rates were high, averaging 8.4 ± 3.2 mg N m −2 d −1 , and were most strongly correlated to mineral nitrogen concentrations and denitrifying enzyme activity (R 2 = 0.73). Gross N 2 O production rates varied spatially, with the highest rates in soils with the best drainage and the highest mineral N availability. Estimated and calculated N 2 O consumption rates constrained the average N 2 O yield from 0.70 to 0.84. Our results demonstrate that the 15 N 2 O pool dilution technique can provide well-constrained estimates of N 2 O yields and field rates of gross N 2 O production correlated to soil characteristics, improving our understanding of terrestrial N 2 O dynamics.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 68
    facet.materialart.
    Unknown
    Climate change and the invasion of California by grasses (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Over the next century, changes in the global climate are expected to have major consequences for plant communities, possibly including the exacerbation of species invasions. We evaluated this possibility in the grass flora of California, which is economically and ecologically important and heavily invaded. We used a novel, trait-based approach involving two components: identifying differences in trait composition between native and exotic components of the grass flora and evaluating contemporary trait-climate relationships across the state. The combination of trait-climate relationships and trait differences between groups allows us to predict changes in the exotic-native balance under climate change scenarios. Exotic species are more likely to be annual, taller, with larger leaves, larger seeds, higher specific leaf area and higher leaf N percentage than native species. Across the state, all of these traits are associated with regions with higher temperature. Therefore, we predict that increasing temperatures will favor trait states that tend to be possessed by exotic species, increasing the dominance of exotic species. This prediction is corroborated by the current distribution of exotic species richness relative to native richness in California; warmer areas contain higher proportions of exotic species. This pattern was very well captured by a simple model that predicts invasion severity given only the trait-climate relationship for native species and trait differences between native and exotic species. This study provides some of the first evidence for an important interaction between climate change and species invasions across very broad geographic and taxonomic scales.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 69
    facet.materialart.
    Unknown
    An automated disc infiltrometer for infiltration rate measurements using a microflowmeter (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: This work presents a new design of disc infiltrometer, which, associated with a microflowmeter (MF) and a solenoid valve set, makes it possible to automate the infiltration rate ( Q ) measurements at different soil pressure heads (ψ). The MF consists of a 13.8-cm long and 1.5 mm i.d. pipe, with a pressure transducer connecting the two ends of the MF, inserted in a water-flow pipe that connects the Mariotte tube and the water-supply reservoir of the disc infiltrometer. Water flow is calculated from the head losses in the MF. Changes in ψ in the bubble tower, automatically effected when the infiltration rate reaches steady-state, are controlled by a datalogger connected to four solenoid valves. The new design was tested in laboratory and field conditions, and the results showed that the MF allows the soil water infiltration rates to be correctly estimated for different soil characteristics. The solenoid valve set plus datalogger system satisfactorily monitored the changes in ψ and allowed the measurement time to be optimized. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 70
    facet.materialart.
    Unknown
    A comparison of fiber-optic distributed temperature sensing to traditional methods of evaluating groundwater inflow to streams (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: There are several methods for determining the spatial distribution and magnitude of groundwater inputs to streams. We compared results of conventional methods (dye dilution gauging, acoustic Doppler velocimeter (ADV) differential gauging, and geochemical end-member mixing) to Distributed Temperature Sensing (DTS) using a fiber-optic cable installed along 900 m of Nine Mile Creek in Syracuse, New York, USA during low-flow conditions (discharge = 1.4 m 3 s -1 ). With the exception of differential gauging, all methods identified a focused, contaminated groundwater inflow and produced similar groundwater discharge estimates for that point, with a mean of 66.8 Ls -1 between all methods although the precision of these estimates varied. ADV discharge measurement accuracy was reduced by non-ideal conditions and failed to identify, much less quantify, the modest groundwater input, which was only 5% of total stream flow. These results indicate ambient tracers, such as heat and geochemical mixing, can yield spatially and quantitatively refined estimates of relatively modest groundwater inflow even in large rivers. DTS heat tracing, in particular, provided the finest spatial characterization of groundwater inflow, and may be more universally applicable than geochemical methods, for which a distinct and consistent groundwater end member may be more difficult to identify. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 71
    facet.materialart.
    Unknown
    Tree mortality in the eastern and central U.S.:Patterns and Drivers (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: Substantial uncertainty surrounds how forest ecosystems will respond to the simultaneous impacts of multiple global change drivers. Long-term forest dynamics are sensitive to changes in tree mortality rates, however we lack an understanding of the relative importance of the factors that affect tree mortality across different spatial and temporal scales. We used the US Forest Service Forest Inventory and Analysis database to evaluate the drivers of tree mortality for eastern temperate forest at the individual-level across spatial scales from tree to landscape to region. We investigated thirteen covariates in four categories: climate, air pollutants, topography, and stand characteristics. Overall, we found that tree mortality was most sensitive to stand characteristics and air pollutants. Different functional groups also varied considerably in their sensitivity to environmental drivers. This research highlights the importance of considering the interactions among multiple global change agents in shaping forest ecosystems.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 72
    facet.materialart.
    Unknown
    Linear mixed modelling of snow distribution in the central Yukon (2011)
    Wiley
    Details
    Publication Date: 2011-06-23
    Description: Remote sensing estimates of snow water equivalent (SWE) in mountainous areas are subject to large uncertainties. As a prerequisite for testing passive microwave algorithm estimations of SWE, this study aims to collect snow depth (SD) data and provide an understanding of its complex spatial structure as part of the Canadian International Polar Year observations theme. Snow accumulation, redistribution and ablation are controlled by processes that depend on a variety of topographic factors as well as land surface characteristics, which leads us to modelling SD as a function of proxy variables derived from digital elevation model and Landsat data. Field measurements were performed at 3924 locations compromising 184 sites in 50 transects over two years. These measurements were used to predict SD over the study area using a spatial linear mixed-effects model, a model type capable of handling the hierarchical structure of the field data. The model, built using stepwise variable selection, uses as predictor variables transformed elevation, slope, the logarithm of slope, potential incoming solar radiation and its transform; the normalized difference vegetation index, and a transformed tasseled cap brightness from Landsat imagery. A second, simpler model links SD with density giving SWE. The cross-validated root mean squared error of the SD distribution model was 14 cm around an overall mean of 80 cm over a domain of 250 x 250 km. This instantaneous end-of-season peak-accumulation snow map will enable the validation of satellite remote sensing over a generally inaccessible area. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 73
    facet.materialart.
    Unknown
    Relationship between specific surface area and the dry end of the water retention curve for soils with varying clay and organic carbon contents (2011)
    Wiley
    Details
    Publication Date: 2011-06-23
    Description: Accurate description of the soil water retention curve (SWRC) at low water contents is important for simulating water dynamics and biochemical vadose zone processes in arid environments. Soil water retention data corresponding to matric potentials of less than −10 MPa, where adsorptive forces dominate over capillary forces, have also been used to estimate soil specific surface area (SA). In the present study, the dry end of the SWRC was measured with a chilled-mirror dew point psychrometer for 41 Danish soils covering a wide range of clay (CL) and organic carbon (OC) contents. The 41 soils were classified into four groups on the basis of the Dexter number (n = CL/OC), and the Tuller-Or (TO) general scaling model describing water film thickness at a given matric potential ( 10. A strong correlation between the ratio of the two surface area estimates and the Dexter number was observed and applied as an additional scaling function in the TO model to rescale the soil water retention curve at low water contents. However, the TO model still overestimated water film thickness at potentials approaching ovendry condition (about −800 MPa). The semi–log linear Campbell-Shiozawa-Rossi-Nimmo (CSRN) model showed better fits for all investigated soils from −10 to −800 MPa and yielded high correlations with CL and SA. It is therefore recommended to apply the empirical CSRN model for predicting the dry part of the water retention curve (−10 to −800 MPa) from measured soil texture or surface area. Further research should aim to modify the more physically based TO model to obtain better descriptions of the SWRC in the very dry range (−300 to −800 MPa).
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 74
    facet.materialart.
    Unknown
    Elevated CO2 stimulates grassland soil respiration by increasing carbon inputs rather than by enhancing soil moisture (2011)
    Wiley
    Details
    Publication Date: 2011-06-24
    Description: It is not clear whether the consistent positive effect of elevated CO 2 on soil respiration (soil carbon flux, SCF) results from increased plant and microbial activity due to (1) greater C availability through CO 2 -induced increases in C inputs or (2) enhanced soil moisture via CO 2 -induced declines in stomatal conductance and plant water use. Global changes such as biodiversity loss or nitrogen (N) deposition may also affect these drivers, interacting with CO 2 to affect SCF. To determine the effects of these factors on SCF and elucidate the mechanism(s) behind the effect of elevated CO 2 on SCF, we measured SCF and soil moisture throughout a growing season in the Biodiversity, CO 2 , and N (BioCON) experiment. Increasing diversity and N caused small declines in soil moisture. Diversity had inconsistent small effects on SCF through its effects on abiotic conditions, while N had a small positive effect that was unrelated to soil moisture. Elevated CO 2 had large consistent effects, increasing soil moisture by 26% and SCF by 45%. However, CO 2 -induced changes in soil moisture were weak drivers of SCF: CO 2 effects on SCF and soil moisture were uncorrelated, CO 2 effect size did not change with soil moisture, within-day CO 2 effects via soil moisture were neutral or weakly negative, and the estimated effect of increased C availability was 14 times larger than that of increased soil moisture. Combined with previous BioCON results indicating elevated CO 2 increases C availability to plants and microbes, our results suggest increased SCF is driven by CO 2 -induced increases in substrate availability. Our results provide further support for increased rates of belowground C cycling at elevated CO 2 and evidence that, unlike the response of productivity to elevated CO 2 in BioCON, the response of SCF is not strongly N limited. Thus, N limited grasslands are unlikely to act as a C sink under elevated CO 2 .
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 75
    facet.materialart.
    Unknown
    Response functions for in-stream solute transport in river networks (2011)
    Wiley
    Details
    Publication Date: 2011-06-07
    Description: This paper analyzes the effects of different hydrological mechanisms on the solute response in watershed stream networks. Important processes are due to the hydraulic and chemical retention of reactive solutes in transient storage zones and the cumulative consequences of these processes from a single transport pathway as well as from the network of transport pathways. Temporal moments are derived for a distributed stream network and for a compartment-in-series model. The temporal moments are evaluated and are utilized to derive formal expressions for translating the network parameters into compartmental model parameters. The analysis reveals that in addition to the hydraulic and chemical retention processes, the morphological and topological properties of a watershed have a distinct impact on the central temporal moments in terms of averaging of the solute load weighted distances as well as the transport parameters over the network. Kinetic (rate-limited) transient storage affects second-order and higher central temporal moments and thus has a secondary effect on the parameterization of compartmental models. Additional considerable contributions to all temporal moments are introduced when parameter variability along transport pathways is considered. The paper demonstrates an improved model outcome for phosphorus transport in a small Swedish watershed by accounting for the overall network effects when parameterizing a compartment-in-series model.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 76
    facet.materialart.
    Unknown
    The full life cycle of a polar low over the Norwegian Sea observed by three research aircraft flights (2011)
    Wiley
    Details
    Publication Date: 2011-06-08
    Description: During 3–4 March 2008, the Norwegian IPY-THORPEX field campaign successfully carried out three flight missions that observed the full life cycle of a polar low over the Norwegian Sea. Here the three-dimensional structure of the polar low has been investigated using dropsonde data from the three flights. The polar low developed in a cold air outbreak, with temperature differences between the sea surface and 500 hPa of about 45–50°C. Cross-sections show that the horizontal gradients of potential temperature weakened as the polar low matured, suggesting that baroclinic energy conversion took place. Dropsonde data of potential temperature and relative humidity show evidence of a tropopause fold, which is possibly a manifestation of upper-level forcing. This is corroborated by potential vorticity inversion, which shows a dominant role of upper-level forcing throughout the polar low's lifetime. During the cyclogenesis stage the polar low circulation was confined below 700 hPa, with a northerly low-level jet of 26 m s −1 . In the mature stage, its circulation reached up to the tropopause (∼450 hPa), with maximum wind speed between 700 and 900 hPa of about 26–28 m s −1 . At this stage the polar low warm core was about 3 K warmer than surrounding air masses. The deep moist towers at the eye-like structure of the polar low extended up to the tropopause with relative humidity values above 70%, indicating a possibly important role for condensational heating in the development. Estimates of surface fluxes of sensible and latent heat using temperature and moisture from the dropsonde data show latent heat fluxes west of the polar low increasing from 175 to 300 W m −2 as the low matured, while the sensible heat fluxes rose from 200 to 280 W m −2 , suggesting a gradually increasing contribution of surface fluxes to the energetics of the polar low with time. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 77
    facet.materialart.
    Unknown
    Using time-lapse gravity for groundwater model calibration: An application to alluvial aquifer storage (2011)
    Wiley
    Details
    Publication Date: 2011-06-08
    Description: The estimation of hydrological model parameters by calibration to field data is a critical step in the modeling process. However, calibration often fails because of parameter correlation. Here it is shown that time-lapse gravity data can be combined with hydraulic head data in a coupled hydrogeophysical inversion to decrease parameter correlation in groundwater models. This is demonstrated for a model of riverbank infiltration where combined inversion successfully constrains hydraulic conductivity and specific yield in both an analytical and a numerical groundwater model. A sensitivity study shows that time-lapse gravity data are especially useful to constrain specific yield. Furthermore, we demonstrate that evapotranspiration, and riverbed conductance are better constrained by coupled inversion to gravity and head data than to head data alone. When estimating the four parameters simultaneously, the six correlation coefficients were reduced from unity when only head data were employed to significantly lower values when gravity and head data were combined. Our analysis reveals that the estimated parameter values are not very sensitive to the choice of weighting between head and gravity data over a large interval of relative weights.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 78
    facet.materialart.
    Unknown
    Discharge estimation from H-ADCP measurements in a tidal river subject to sidewall effects and a mobile bed (2011)
    Wiley
    Details
    Publication Date: 2011-06-08
    Description: Horizontal acoustic Doppler current profilers (H-ADCPs) can be employed to estimate river discharge based on water level measurements and flow velocity array data across a river transect. A new method is presented that accounts for the dip in velocity near the water surface, which is caused by sidewall effects that decrease with the width to depth ratio of a channel. A boundary layer model is introduced to convert single-depth velocity data from the H-ADCP to specific discharge. The parameters of the model include the local roughness length and a dip correction factor, which accounts for the sidewall effects. A regression model is employed to translate specific discharge to total discharge. The method was tested in the River Mahakam, representing a large river of complex bathymetry, where part of the flow is intrinsically three-dimensional and discharge rates exceed 8000 m3 s−1. Results from five moving boat ADCP campaigns covering separate semidiurnal tidal cycles are presented, three of which are used for calibration purposes, whereas the remaining two served for validation of the method. The dip correction factor showed a significant correlation with distance to the wall and bears a strong relation to secondary currents. The sidewall effects appeared to remain relatively constant throughout the tidal cycles under study. Bed roughness length is estimated at periods of maximum velocity, showing more variation at subtidal than at intratidal time scales. Intratidal variations were particularly obvious during bidirectional flow conditions, which occurred only during conditions of low river discharge. The new method was shown to outperform the widely used index velocity method by systematically reducing the relative error in the discharge estimates.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 79
    facet.materialart.
    Unknown
    Investigating Controls on the Thermal Sensitivity of Pennsylvania Streams (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Stream temperature, an important measure of ecosystem health, is expected to be altered by future changes in climate and land use, potentially leading to shifts in habitat distribution for aquatic organisms dependent on particular temperature regimes. To assess the sensitivity of stream temperature to change in a region where such a shift has the potential to occur, we examine the variability of and controls on the direct relationship between air and water temperature across the state of Pennsylvania. We characterized the relationship between air and stream temperature via linear and nonlinear regression for 57 sites across Pennsylvania at daily and weekly timescales. Model fit (r 2 ) improved for 92% (daily) and 65% (weekly) of sites for nonlinear versus linear relationships. Fit for weekly versus daily regression analysis improved by 0.08 for linear and 0.06 for nonlinear regression relationships. To investigate the mechanisms controlling stream temperature sensitivity to environmental change, we define ‘thermal sensitivity’ as the sensitivity of stream temperature of a given site to change in air temperature, quantified as the slope of the regression line between air and stream temperature. Air temperature accounted for 60 to 95% of the daily variation in stream temperature for sites at or above a Strahler stream order of 3, with thermal sensitivities ranging from low (0.02) to high (0.93). The sensitivity of stream temperature to air temperature is primarily controlled by stream size (stream order) and baseflow contribution (BFI). Together, stream order and baseflow index explained 43% of the variance in thermal sensitivity across the state, and 59% within the Susquehanna River Basin. In small streams, baseflow contribution was the major determinant of thermal sensitivity, with increasing baseflow contributions resulting in decreasing sensitivity values. In large streams, thermal sensitivity increased with stream size, as a function of accumulated heat throughout the stream network. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 80
    facet.materialart.
    Unknown
    Rainfall infiltration-derived submarine groundwater discharge from multi-layered aquifer system terminating at the coastline (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: This paper investigates the quantity of submarine groundwater discharge (SGD) from a coastal multi-layered aquifer system in response to constant rainfall infiltration. The system comprises an unconfined aquifer, a leaky confined aquifer and an aquitard between them and terminates at the coastline. An approximate analytical solution is derived based on the following assumptions: (i) flow is horizontal in the aquifers and vertical in the aquitard, and (ii) flow in the unconfined aquifer is described by nonlinear Boussinesq equation. The analytical solution is compared with numerical solutions of the strictly two-dimensional nonlinear model to validate the model assumptions used for the analytical solution. The SGD from the leaky confined aquifer increases with the inland rainfall infiltration recharge and the specific leakage of aquitard. The maximum SGD ranges from 1.87 m 3 /d to 10.37 m 3 /d per meter of shoreline when rainfall infiltration ranges from 18.2 mm/yr to 182 mm/yr and the specific leakage of aquitard varies from 10 -9 1/d to 10 -1 1/d. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 81
    facet.materialart.
    Unknown
    Three decades of water quality measurements from the Upper Severn experimental catchments at Plynlimon, Wales: an openly accessible data resource for research, modelling, environmental management and education. (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 82
    facet.materialart.
    Unknown
    Age trends in tree ring growth and isotopic archives: A case study of Pinus sylvestris L. from northwestern Norway (2011)
    Wiley
    Details
    Publication Date: 2011-06-11
    Description: Measurements of tree ring width and relative density have contributed significantly to many of the large-scale reconstructions of past climatic change, but to extract the climate signal it is first necessary to remove any nonclimatic age-related trends. This detrending can limit the lower-frequency climate information that may be extracted from the archive (the “segment length curse”). This paper uses a data set of ring widths, maximum latewood density and stable carbon and oxygen isotopes from 28 annually resolved series of known-age Pinus sylvestris L. trees in northwestern Norway to test whether stable isotopes in tree rings require an equivalent statistical detrending. Results indicate that stable oxygen and carbon isotope ratios from tree rings whose cambial age exceeds c.50 years exhibit no significant age trends and thus may be used to reconstruct environmental variability and physiological processes at this site without the potential loss of low-frequency information associated with detrending.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 83
    facet.materialart.
    Unknown
    Controls on the long-term downward transport of δ²H of water in a regionally extensive, two-layered aquitard system (2011)
    Wiley
    Details
    Publication Date: 2011-06-10
    Description: Seven high-resolution (0.3–0.6 m depth intervals), 1-D vertical profiles of the δ²H of pore water were collected across a 300 km2 study area in southern Saskatchewan, Canada, to define the vertical controls on solute transport in a 〉120 m thick, two-layered aquitard system. The 1-D profiles were augmented with an existing δ²H profile collected from a previous study. The surficial aquitard in the area consists of Quaternary deposits (either glacial till or lacustrine deposits; 13 to 128 m thick) underlain by an upper Cretaceous claystone aquitard (80–110 m thick). The shape of the individual δ²H profiles and associated 1-D transport modeling suggest diffusion is the regionally dominant vertical transport mechanism across the aquitards. The profile shape is controlled by the thickness of the Quaternary deposit and the δ²H value at the upper boundary, which coincides with the depth of the water table. The upper boundary δ²H value varies considerably across the area (−149‰ to −101‰), perhaps due to differences in local hydrological conditions (e.g., slope, aspect, infiltration) across the landscape. Modeling of all profiles shows the timing for till deposition and the timing of climate change during the Holocene are consistent across the area (∼30 ka and 7–10 ka before the present, respectively), corroborating other studies. This study provides insights into the hydrogeologic controls on solute transport in an aquitard system and associated geologic and climatic changes for a prairie region over the past 30 ka, and improves our understanding of initial and time-dependent transport boundary conditions for the study of aquitards.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 84
    facet.materialart.
    Unknown
    Vegetation Canopy and Radiation Controls on Permafrost Plateau Evolution within the Discontinuous Permafrost Zone, Northwest Territories, Canada (2011)
    Wiley
    Details
    Publication Date: 2011-06-11
    Description: ABSTRACT This study examines the links between the spatial distribution of three-dimensional vegetation structural characteristics and historical permafrost plateau area changes using airborne light detection and ranging and aerial photography. The results show that vegetation is prone to reduced canopy fractional cover (by up to 50%) and reduced canopy heights (by 16−30%) at the edges of plateaus. Reduced biomass may cause a positive feedback, whereby diminished within- and below-canopy shadowing (by 1 h of shadow time per day) results in increased radiation incident on the ground surface (16% greater at open- vs closed-canopy plateau sites) and increased longwave radiation losses (74% greater at open- vs closed-canopy plateau sites). Increased incident shortwave radiation may result in augmented thawing of permafrost and increased meltwater runoff, which further inhibits vegetation and permafrost persistence. Edge influences on ground thaw cause vegetation to die over several years (confirmed using historical aerial photography), thereby exacerbating thaw and plateau area reduction (plateau area reduction = ~27% over 60 years). Permafrost degradation is also evidenced by the increasingly fragmented characteristics of the landscape. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 1045-6740
    Electronic ISSN: 1099-1530
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 85
    facet.materialart.
    Unknown
    Impact of the spatial arrangement of land management practices on surface runoff for small catchments (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Predicting the impact of land use changes on the hydrological response is crucial for water resource management. In the particular case of small catchments (1-10 km 2 ), distributed models could provide useful answers regarding the effects of cultivation practices and man-made works on water fluxes. However, the impacts of specific land use spatial arrangements are difficult to predict because of the prohibitive number of possible cases to consider. Focusing on surface runoff, this paper describes a strategy based on a water particle tracking routine to be plugged-in a distributed model that is designed to determine the spatial arrangements of land management practices that have the greatest impact on volume, peak discharge and lag time at the catchment outlet. A case study is described; the hydrological response of the Roujan catchment (Herault, France) is simulated with the MHYDAS model. The Roujan catchment contains a vineyard in a Mediterranean climate in a landscape in which weeding practices highly influence the partition between soil infiltration and runoff. The results showed that the proposed strategy is much more efficient than a random approach to design the spatial arrangements of the vineyard weeding practices with the greatest impact. Therefore, the proposed strategy may lead to innovative policies for the spatial planning of land management practices. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 86
    facet.materialart.
    Unknown
    GIS-evaluation of two slope-calculation methods regarding their suitability in slope analysis using high-precision LiDAR Digital Elevation Models (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Description: Slope is a metric essential to describing surface hydrological processes, including overland flow, soil erosion, and sediment transport. Most commercial GIS have built-in functions to calculate slope from Digital Elevation Models (DEMs) using average-neighborhood-methods appropriate for coarse-resolution DEMs. Emergence of high-resolution DEMs from LiDAR data creates a need to re-assess the suitability of existing algorithms in calculating slope for hydrological applications. We investigate the properties of two slope-calculation methods, an average-neighborhood-slope (ANS) and a downhill-slope (DHS) method. Conceptually, the DHS method provides a more intuitive description of surface water-flow characteristics in uneven terrain. Five DEMs were used to evaluate the methods, namely a 1-m and 10-m resolution DEM interpolated from irregular height point-data generated with conventional photogrammetric techniques, and a 1-m, 5-m, and 10-m resolution DEM derived from LiDAR data. Calculated slopes were summarised for the entire DEM, along mapped streams, and within pre-defined “stream buffers”. Slopes generated for the entire DEM with 1-m resolution LiDAR DEM indicated that the ANS method on average produced smaller slopes than the DHS method (0.64 o ). A similar trend was observed in stream buffers, with greatest slope differences (Δ S ) between methods within 20-m buffers when the 1-m LiDAR-based DEM was used (Δ S = 1.12 o ). In contrast to these results, ANS-calculated slopes along mapped streams were generally larger than those calculated with the DHS method for LiDAR-based DEMs (Δ S = 0.81 o ). Results from this study signal the need for caution when estimating slopes along streams from high-accuracy, LiDAR-generated DEMs. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 87
    facet.materialart.
    Unknown
    Report from the international permafrost association: A new strategy and structure for the international permafrost association (2011)
    Wiley
    Details
    Publication Date: 2011-06-14
    Print ISSN: 1045-6740
    Electronic ISSN: 1099-1530
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 88
    facet.materialart.
    Unknown
    Simulations of the London urban heat island (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: We present simulations of London's meteorology using the Met Office Unified Model with a new, sophisticated surface energy-balance scheme to represent the urban surfaces, called MORUSES. Simulations are performed with the urban surfaces represented and with the urban surfaces replaced with grass in order to calculate the urban increment on the local meteorology. The local urban effects were moderated to some extent by the passage of an onshore flow that propagated up the Thames estuary and across the city, cooling London slightly in the afternoon. Validations of screen-level temperature show encouraging agreement to within 1–2 K, when the urban increment is up to 5 K. The model results are then used to examine factors shaping the spatial and temporal structure of London's atmospheric boundary layer. The simulations reconcile the differences in the temporal evolution of the urban heat island (UHI) shown in various studies and demonstrate that the variation of UHI with time depends strongly on the urban fetch. The UHI at a location downwind of the city centre shows a decrease in UHI during the night, while the UHI at the city centre stays constant. Finally, the UHI at a location upwind of the city centre increases continuously. The magnitude of the UHI by the time of the evening transition increases with urban fetch. The urban increments are largest at night, when the boundary layer is shallow. The boundary layer experiences continued warming after sunset, as the heat from the urban fabric is released, and a weakly convective boundary layer develops across the city. The urban land-use fraction is the dominant control on the spatial structure in the sensible heat flux and the resulting urban increment, although even the weak advection present in this case study is sufficient to advect the peak temperature increments downwind of the most built-up areas. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, the Met Office
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 89
    facet.materialart.
    Unknown
    Airborne lidar observations in the inflow region of a warm conveyor belt (2011)
    Wiley
    Details
    Publication Date: 2011-06-15
    Description: Warm conveyor belts (WCBs) are key flow structures associated with extratropical cyclones. They transport moist air from the cyclone's warm sector poleward and upward close to the tropopause level, leading to the formation of elongated cloud bands, intense latent heating and surface precipitation. In this study a comprehensive dataset of airborne lidar observations of moisture and wind from different campaigns has been investigated with a trajectory-based approach to identify ‘lucky encounters’ with WCBs. On 19 July 2007, an upstream flight over the Iberian Peninsula during the European THORPEX Regional Campaign (ETReC 2007) in Central Europe intersected two WCBs: one in the upper tropospheric outflow region about 3 days after starting the ascent, and the other one in the boundary layer inflow region over Spain just prior to the strong ascent. Comparison of the lidar humidity measurements with analysis fields from the European Centre for Medium-Range Weather Forecasts (ECMWF) reveals significant positive deviations, equivalent to an overestimation of the modelled humidity, in this low-tropospheric WCB inflow region (of about 1 g kg −1 (14%) on average and with peak deviations up to 7 g kg −1 ). It is noteworthy that this substantial bias occurs in a potentially dynamically highly relevant air mass that will be subsequently lifted within a WCB to the upper troposphere. A Lagrangian moisture source diagnostic reveals that these large moisture deviations occur within air masses that, according to the ECMWF analyses, are coherently transported from the western Mediterranean towards Spain and experience intense moisture uptake over the Ebro valley. It is suggested that inaccuracies in surface evapotranspiration, horizontal moisture advection, and turbulent vertical transport of moisture in the atmospheric boundary layer potentially contribute to the erroneous low-tropospheric humidity in the inflow region of this particular summertime WCB over Spain in the ECMWF analyses. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 90
    facet.materialart.
    Unknown
    Climate variability in West Greenland during the past 1500 years: evidence from a high-resolution marine palynological record from Disko Bay (2011)
    Wiley
    In: Boreas
    Details
    Publication Date: 2011-06-16
    Description: Ribeiro, S., Moros, M., Ellegaard, M. & Kuijpers, A. 2011: Climate variability in West Greenland during the past 1500 years: evidence from a high-resolution marine palynological record from Disko Bay. Boreas , 10.1111/j.1502-3885.2011.00216.x. ISSN 0300-9483. Here we document late-Holocene climate variability in West Greenland as inferred from a marine sediment record from the outer Disko Bay. Organic-walled dinoflagellate cysts and other palynomorphs were used to reconstruct environmental changes in the area through the last c. 1500 years at 30–40 years resolution. Sea ice cover and primary productivity were identified as the two main factors driving dinoflagellate cyst community changes through time. Our data provide evidence for an opposite climate trend in West Greenland relative to the NE Atlantic region from c . AD 500 to 1050. For the same period, sea-surface temperatures in Disko Bay are out-of-phase with Greenland ice-core reconstructed temperatures and marine proxy data from South and East Greenland. This is probably governed by an NAO-type pattern, which results in warmer sea-surface conditions with less extensive sea ice in the area for the later part of the Dark Ages cold period ( c . AD 500 to 750) and cooler conditions with extensive sea ice inferred for the first part of the Medieval Climate Anomaly (MCA) ( c . AD 750 to 1050). After c . AD 1050, the marine climate in Disko Bay becomes in-phase with trends described for the NE Atlantic, reflected in the warmer interval for the remainder of the MCA ( c . AD 1050–1250), followed by cooling towards the onset of the Little Ice Age at c . AD 1400. The inferred scenario of climate deterioration and extensive sea ice is concomitant with the collapse of the Norse Western Settlement in Greenland at c . AD 1350.
    Print ISSN: 0300-9483
    Electronic ISSN: 1502-3885
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 91
    facet.materialart.
    Unknown
    Methane and soil CO2 production from current-season photosynthates in a rice paddy exposed to elevated CO2 concentration and soil temperature (2011)
    Wiley
    Details
    Publication Date: 2011-06-16
    Description: Quantification of rhizodeposition (root exudates and root turnover) represents a major challenge for understanding the links between above-ground assimilation and below-ground anoxic decomposition of organic carbon in rice paddy ecosystems. Free-air CO 2 enrichment (FACE) fumigating depleted 13 CO 2 in a rice paddy resulted in a smaller 13 C/ 12 C ratio in plant assimilated carbon, providing a unique measure by which we partitioned the sources of decomposed gases (CO 2 and CH 4 ) into current-season photosynthates (new C) and soil organic matter (old C). Additionally, we imposed a soil warming treatment nested within the CO 2 treatments to assess whether the carbon source was sensitive to warming. Compared with the ambient CO 2 treatment, the FACE treatment decreased the 13 C/ 12 C ratio not only in the rice-plant carbon but also in the soil CO 2 and CH 4 . The estimated new C contribution to dissolved CO 2 was minor (~20%) at the tillering stage, increased with rice growth and was about 50% from the panicle formation stage onwards. For CH4, the contribution of new C was greater than for heterotrophic CO2 production; approximately 40–60% of season-total CH 4 production originated from new C with a tendency toward even larger new C contribution with soil warming, presumably because enhanced root decay provided substrates for greater CH 4 production. The results suggest a fast and close coupling between photosynthesis and anoxic decomposition in soil, and further indicate a positive feedback of global warming by enhanced CH 4 emission through greater rhizodeposition.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 92
    facet.materialart.
    Unknown
    A generalized grid connectivity–based parameterization for subsurface flow model calibration (2011)
    Wiley
    Details
    Publication Date: 2011-06-17
    Description: We develop a novel method of parameterization for spatial hydraulic property characterization to mitigate the challenges associated with the nonlinear inverse problem of subsurface flow model calibration. The parameterization is performed by the projection of the estimable hydraulic property field onto an orthonormal basis derived from the grid connectivity structure. The basis functions represent the modal shapes or harmonics of the grid, are defined by a modal frequency, and converge to special cases of the discrete Fourier series under certain grid geometries and boundary assumptions; therefore, hydraulic property updates are performed in the spectral domain and merge with Fourier analysis in ideal cases. Dependence on the grid alone implies that the basis may characterize any grid geometry, including corner point and unstructured, is model independent, and is constructed off-line and only once prior to flow data assimilation. We apply the parameterization in an adaptive multiscale model calibration workflow for three subsurface flow models. Several different grid geometries are considered. In each case the prior hydraulic property model is updated using a parameterized multiplier field that is superimposed onto the grid and assigned an initial value of unity at each cell. The special case corresponding to a constant multiplier is always applied through the constant basis function. Higher modes are adaptively employed during minimization of data misfit to resolve multiscale heterogeneity in the geomodel. The parameterization demonstrates selective updating of heterogeneity at locations and spatial scales sensitive to the available data, otherwise leaving the prior model unchanged as desired.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 93
    facet.materialart.
    Unknown
    The impact of deep convection on the West African summer monsoon climate: a regional climate model sensitivity study (2011)
    Wiley
    Details
    Publication Date: 2011-06-18
    Description: The role of the representation of deep convection on key elements of the West African summer monsoon climate is addressed using the Regional Climate Model RegCM3. Two simulations in which a scheme of deep convection is activated and then turned off are performed and intercompared. Results show that the presence of deep convective heating along the intertropical convergence zone sustains increased lower-level baroclinicity favoring intensification of the jet core and leading to a more realistic African easterly jet. In addition, although the isentropic potential vorticity (IPV) is lower when the convection scheme is switched off, African easterly waves (AEWs) are still generated and propagate westwards but they dissipate around the west coast. Substantial differences between the two simulations occur mainly at the 6- to 9-day time-scale over land, when much weaker activity is simulated in the absence of convection. This indicates that orographic friction and low-level large-scale moisture convergence, generating high values of latent heat and IPV, may play the dominant role in the genesis and growth of AEWs and that deep convection acts to strengthen the overall wave activity and to favor their west coast development. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 94
    facet.materialart.
    Unknown
    Experimental assimilation of DIAL water vapour observations in the ECMWF global model (2011)
    Wiley
    Details
    Publication Date: 2011-06-18
    Description: A unique airborne differential absorption lidar (DIAL) for water vapour observations was developed at the Deutsches Zentrum für Luft- und Raumfahrt (DLR). Installed on board the DLR Falcon 20 aircraft, the system measured a dataset of about 3900 water vapour profiles during the T-PARC field campaign. These high-resolution humidity observations were assimilated into the European Centre for Medium-Range Weather Forecasts (ECMWF) global model using a version of the operational four-dimensional variational data assimilation system. The assimilation system is able to extract the information for DIAL observations, and verification with independent dropsonde observations shows a reduction in the analysis error when DIAL water vapour observations are assimilated. The forecast influence of the humidity observations is found to be small in most cases, but the observations are able to affect the forecast considerably under certain conditions. Systematic errors are investigated by comparison between humidity model fields, DIAL and dropsonde observations. Overall, DIAL observations are roughly 7–10% drier than model fields throughout the troposphere. Comparison with dropsonde observations suggests that the DIAL observations are too dry in the lower troposphere but not above it. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 95
    facet.materialart.
    Unknown
    Multi-sensor satellite remote sensing of dust aerosols over North Africa during GERBILS (2011)
    Wiley
    Details
    Publication Date: 2011-06-18
    Description: In this paper we provide an overview of various satellite products over the Sahara Desert that were available during the GERBILS field campaign. Our results indicate that all mid-visible satellite aerosol optical depth (AOD) products match well with AERONET retrievals. For low AOD (AOD 〈 1), the satellite AODs compare well with aircraft AOD values but they tend to underestimate at high AOD values. We then assessed the satellite products in 0.5 × 0.5 degree grids for the entire study region (10–30°N and 20°W–10°E). If we use a multi-angle imaging spectroradiometer (MISR) as a benchmark for AOD retrievals over bright targets, the estimated AOD derived from the ozone-monitoring instrument aerosol index–MISR relationship performs best when compared with MISR for the entire study region. Although differences exist among satellite products, the advancement in satellite retrieval techniques now provide AOD retrievals over bright targets such as deserts, which are useful for numerical modeling simulation comparisons and other studies. Furthermore, the in situ information from aircraft and the ground continue to provide valuable information for validating satellite products and for assessing their strengths and weaknesses. Copyright © 2011 Royal Meteorological Society and British Crown Copyright, theMet Office
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 96
    facet.materialart.
    Unknown
    Long-term morphological impacts of the opening of a new inlet on a multiple inlet system (2011)
    Wiley
    Details
    Publication Date: 2011-06-22
    Description: In this study, the artificial opening of a new tidal inlet in an existing multiple inlet system is shown to significantly modify the adjacent nearshore and backbarrier morphology, as well as both updrift and downdrift shorelines. The study focuses on the dominant Faro-Olhão and Armona inlets in the Ria Formosa barrier island system of southern Portugal. The equilibrium state and future evolution of the system are inferred using a range of morphological and hydrodynamic indicators, including the evolution of the inlet cross-section, changes in tidal prism, and changes in the dimensions (length and area) of barrier islands. The results reveal how the morphology of an inter-connected two-inlet bay system and the adjacent coastlines has evolved following the artificial opening and stabilisation of Faro-Olhão inlet since 1929. A clear relationship between barrier island size, inlet cross-section/width, and tidal prism is demonstrated. Decadal time-scale changes in the tidal prism of the two inter-connected inlets are shown to be the main mechanism responsible for morphological change, and have resulted in the remobilisation of ebb-tidal delta sediments deposited during previous hydraulic configurations. These changes, in turn, have contributed to a narrowing of Armona inlet and an increase in the size of Culatra Island. The work highlights the importance of ebb-tidal deltas both as sand reservoirs and as conduits through which sand exchange between estuaries or lagoons and the open coast is regulated. It also shows the pivotal role of ebb-tidal deltas in trapping longshore-transported sediment and releasing it again during periods of increased wave activity. The findings have implications regarding the accurate assessment of the stability of multiple inlet systems. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 97
    facet.materialart.
    Unknown
    Reduced diurnal temperature range does not change warming impacts on ecosystem carbon balance of Mediterranean grassland mesocosms (2011)
    Wiley
    Details
    Publication Date: 2011-06-24
    Description: ABSTRACT Daily minimum temperature (T min ) has increased faster than daily maximum temperature (T max ) in many parts of the world, leading to decreases in diurnal temperature range (DTR). Projections suggest these trends are likely to continue in many regions, particularly northern latitudes and in arid regions. Despite wide speculation that asymmetric warming has different impacts on plant and ecosystem production than equal-night-and-day warming, there has been little direct comparison of these scenarios. Reduced DTR has also been widely misinterpreted as a result of night-only warming, when in fact T min occurs near dawn, indicating higher morning as well as night temperatures. We report on the first experiment to examine ecosystem-scale impacts of faster increases in T min than T max, using precise temperature controls to create realistic diurnal temperature profiles with gradual day-night temperature transitions and elevated early morning as well as night temperatures. Studying a constructed grassland ecosystem containing species native to Oregon, USA, we found the ecosystem lost more carbon at elevated than ambient temperatures, but was unaffected by the 3°C difference in DTR between symmetric warming (constantly ambient +3.5°C) and asymmetric warming (dawn T min =ambient +5°C, afternoon T max = ambient +2°C). Reducing DTR had no apparent effect on photosynthesis, likely because temperatures were most different in the morning and late afternoon when light was low. Respiration was also similar in both warming treatments, because respiration temperature sensitivity was not sufficient to respond to the limited temperature differences between asymmetric and symmetric warming. We concluded that changes in daily mean temperatures, rather than changes in T min /T max , were sufficient for predicting ecosystem carbon fluxes in this reconstructed Mediterranean grassland system.
    Print ISSN: 1354-1013
    Electronic ISSN: 1365-2486
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 98
    facet.materialart.
    Unknown
    Using terrigenic 4He to identify and quantify regional groundwater discharge to streams (2011)
    Wiley
    Details
    Publication Date: 2011-06-28
    Description: We present a new technique for identifying and quantifying the discharge of long residence time, regional groundwater to rivers using naturally occurring tracers measured within the river. Terrigenic 4He and 222Rn, synoptically sampled along a 100 km reach in the Fitzroy River in northern Western Australia, are used to identify areas of groundwater inflow to the river and to distinguish shallow, local and deep, regional groundwater. Models of tracer transport in the river can be numerically optimized to calculate total groundwater discharge and to separate regional and local discharge fractions. Discharge of regional groundwater composes close to 15% of the total groundwater discharge along the entire reach, varying spatially along the reach from 0% to 100% of total groundwater discharge. This method should be applicable in river systems where groundwater with elevated terrigenic helium could be discharging to the river. The ability to separate locally from regionally derived groundwater discharge has significant implications for calculating catchment water budgets, for predicting catchment response to changes in precipitation, and for sustainable management of the catchment.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 99
    facet.materialart.
    Unknown
    Increase in sediment transport associated with disturbance by crayfish (2011)
    Wiley
    Details
    Publication Date: 2011-06-29
    Description: There is growing acknowledgement of the interaction between animals and the river bed on which they live and the implications of biological activity for geomorphic processes. It has been observed that signal crayfish ( Pacifastacus leniusculus ) disturb gravel substrates, potentially promoting sediment transport and impacting ecological communities. However, the mechanisms involved and the extent of their impact remain poorly understood, especially in relation to other processes that affect grain mobility in gravel-bed rivers. A series of flume experiments, using loose and water-worked gravel beds of narrowly-graded grain sizes that were exposed to six hours of crayfish activity under low-velocity flows, showed a substantial increase in the number of grains entrained by subsequent higher-velocity flows when compared with control runs in which crayfish were never introduced. Crayfish alter the topography of their substrate by constructing pits and mounds, which affect grain protrusion. When walking and foraging, they also alter gravel fabric by reorienting and changing the friction angle of surface grains. In water-worked surfaces, this fabric rearrangement is shown to lead to a statistically significant, partial reversal of the structuring that had been achieved by antecedent flow. For these previously water-worked surfaces, the increase in entrainment arising from disturbance by crayfish was statistically significant, with grain transport nearly twice as great. This suggests that signal crayfish, an increasingly widespread invasive species in temperate latitudes beyond their native NW North America, have the potential to enhance coarse-grained bedload flux by altering the surface structure of gravel river beds and reducing the stability of surface grains. This study illustrates further the importance of acknowledging the impact of mobile organisms in conditioning the river bed when assessing sediment entrainment mechanics in the context of predicting bedload flux. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 0197-9337
    Electronic ISSN: 1096-9837
    Topics: Geography , Geosciences
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 100
    facet.materialart.
    Unknown
    Upscale feedback of high-frequency winds to ENSO (2011)
    Wiley
    Details
    Publication Date: 2011-05-11
    Description: The impact of the high-frequency (HF, 〈90 days) variability on low-frequency (LF) interannual sea surface temperature (SST) variations associated with the El Niño-Southern Oscillation (ENSO) is investigated by conducting a series of oceanic general circulation model experiments. Two nonlinear rectification mechanisms are examined. The first is the internal oceanic nonlinear dynamics and the second is the nonlinear rectification of the LF surface wind stress by the HF wind. Numerical simulations show that the latter is dominant in modulating the LF SST variability. The HF wind increases both the amplitude and skewness of the LF wind stress anomaly. As a result, it increases both the amplitude and skewness of the SST anomaly (SSTA) in the eastern equatorial Pacific. For strong El Niño events in 1982/83 and 1997/98, such a nonlinear rectification effect may result in a SSTA increase of 1°C. A mixed-layer heat budget analysis reveals that whereas meridional and vertical advections primarily contribute to the strengthening of the warm and cold episodes, the nonlinear zonal advection is responsible for the increase of the SSTA skewness. Including the nonlinear rectification of the HF wind on both the surface wind stress and heat flux anomalies leads to a positively (negatively) skewed SSTA in the eastern (central) Pacific. Thus the combined dynamic and thermodynamic effect reshapes the ENSO zonal structure in such a way that it makes the maximum SSTA confined further to the eastern equatorial Pacific. Copyright © 2011 Royal Meteorological Society
    Print ISSN: 0035-9009
    Electronic ISSN: 1477-870X
    Topics: Geography , Physics
    Published by Wiley
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...