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  • 1
    Unknown
    Basel, Boston, Berlin : Birkhäuser
    Keywords: chemical composition of dew ; fog microphysics ; fog simulations ; remote sensing ; temporal and spatial variation of fog
    Description / Table of Contents: This topical issue of the Journal of Pure and Applied Geophysics focuses on research related to dew and various types of fog occurring around the globe which was presented on July 25-30, 2010, at the 5th International Conference on Fog, Fog Collection, and Dew in Münster, Germany. The areas of knowledge in this field include surface in-situ and remote sensing observations of fog, dew, fog collection, applications of the various fog models (such as 1D, 2D, and 3D fog and forecasting models), microphysical parameterizations, and climatology. This volume gives a very good review of the existing knowledge and highlights the remaining difficulties in predicting and measuring fog at various scales of time and space. It also represents an important step in the direction of addressing new scientific challenges in fog and dew related research, teaching, and operational applications. Students as well as researchers, who are interested either in fog, in association with cloud physics, physical meteorology, aviation meteorology, climatology, weather forecasting and nowcasting, or in other adjacent disciplines like hydrometeorology, environment, and agriculture, will benefit from consulting and reading this topical issue. This publication was significantly supported by the Canadian National Search And Rescue (SAR) Secretariat by funding the Fog Remote Sensing and Modeling (FRAM) Project led by Dr. Ismail Gultepe since 2005.
    Pages: Online-Ressource (VI, 408 Seiten)
    ISBN: 9783034804561
    Language: English
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  • 2
    Publication Date: 2019-07-17
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: This paper presents results of 1 year (from March 25, 2003 to March 24, 2004, 366 days) of continuous measurements of net ecosystem CO2 exchange (NEE) above a steppe in Mongolia using the eddy covariance technique. The steppe, typical of central Mongolia, is dominated by C3 plants adapted to the continental climate. The following two questions are addressed: (1) how do NEE and its components: gross ecosystem production (GEP) and total ecosystem respiration (Reco) vary seasonally? (2) how do NEE, GEP, and Reco respond to biotic and abiotic factors? The hourly minimal NEE and the hourly maximal Reco were −3.6 and 1.2 μmol m−2 s−1, respectively (negative values denoting net carbon uptake by the canopy from the atmosphere). Peak daily sums of NEE, GEP, and Reco were −2.3, 3.5, and 1.5 g C m−2 day−1, respectively. The annual sums of GEP, Reco, and NEE were 179, 138, and −41 g C m−2, respectively. The carbon removal by sheep was estimated to range between 10 and 82 g C m−2 yr−1 using four different approaches. Including these estimates in the overall carbon budget yielded net ecosystem productivity of −23 to +20 g C m−2 yr−1. Thus, within the remaining experimental uncertainty the carbon budget at this steppe site can be considered to be balanced. For the growing period (from April 23 to October 21, 2003), 26% and 53% of the variation in daily NEE and GEP, respectively, could be explained by the changes in leaf area index. Seasonality of GEP, Reco, and NEE was closely associated with precipitation, especially in the peak growing season when GEP and Reco were largest. Water stress was observed in late July to early August, which switched the steppe from a carbon sink to a carbon source. For the entire growing period, the light response curves of daytime NEE showed a rather low apparent quantum yield (α=−0.0047 μmol CO2 μmol−1 photons of photosynthetically active radiation). However, the α values varied with air temperature (Ta), vapor pressure deficit, and soil water content.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3 °C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3–6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50–80% higher evapotranspiration, and therefore only 30–50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming.Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These discrepancies relate more strongly to the approach and assumptions for extrapolation than to inconsistencies in the underlying data. Inverse modelling from atmospheric CO2 concentrations suggests that high latitudes are neutral or net sinks for atmospheric CO2, whereas field measurements suggest that high latitudes are neutral or a net CO2 source. Both approaches rely on assumptions that are difficult to verify. The most parsimonious explanation of the available data is that drying in tundra and disturbance in boreal forest enhance CO2 efflux. Nevertheless, many areas of both tundra and boreal forests remain net sinks due to regional variation in climate and local variation in topographically determined soil moisture. Improved understanding of the role of high-latitude ecosystems in the climate system requires a concerted research effort that focuses on geographical variation in the processes controlling land–atmosphere exchange, species composition, and ecosystem structure. Future studies must be conducted over a long enough time-period to detect and quantify ecosystem feedbacks.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Studies and models of trace-gas flux in the Arctic consider temperature and moisture to be the dominant controls over land–atmosphere exchange,, with little attention having been paid to the effects of different substrates. Likewise, current Arctic vegetation maps for models of vegetation ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Boundary layer meteorology 74 (1995), S. 321-340 
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A correction model for eddy correlation flux measurements is developed and applied to nitrogen dioxide flux measurements obtained from a SOLENT sonic anemometer and a Scintrex Luminox LMA-3 analyser for NO2. Four field campaigns were carried out near the village of Merenschwand in Central Switzerland from which two were selected for further analysis in this paper. The need for the correction of measured eddy covariance fluxes arises due to the damping loss of the NO2 analyser at high frequencies. This damping loss is described by an analogy to inductance in an electronical alternating current circuit. The independent variables in the correction model are:z (measuring height above zero-plane displacement), $$\bar u$$ (mean horizontal wind speed), ζ (Monin-Obukhov stability parameter),f (natural frequency) and inductanceL. The value for inductanceL can be derived from spectral and cospectral analysis. The theoretical cospectrum of an ideal measurement is taken from Kaimalet al. (1972) and extended with a damping term in order to describe the real measurements of the cospectrum. The inductanceL of the LMA-3 with a 0.6 cm teflon aspiration tube of 5 m length lies in the order of 0.30 to 0.35 for the dataset from Merenschwand. With this inductance, a correction factor of 1.17 in August/September 1992 and of 1.18 in May 1993 was determined for the NO2 flux maxima during daytime. The range of the correction factor is 1.05 to 1.31 for the mean daily cycles of both datasets.
    Type of Medium: Electronic Resource
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  • 7
  • 8
    Publication Date: 1995-06-01
    Print ISSN: 0006-8314
    Electronic ISSN: 1573-1472
    Topics: Geosciences , Physics
    Published by Springer
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  • 9
    Publication Date: 2020-03-01
    Description: Understanding the mechanisms underlying net ecosystem CO2 exchange (NEE) in mountain grasslands is important to quantify their relevance in the global carbon budget. However, complex interactions between environmental variables and vegetation on NEE remain unclear; and there is a lack of empirical data, especially from the high elevations and the Mediterranean region. A chamber-based survey of CO2 exchange measurements was carried out in two climatically contrasted grasslands (montane v. subalpine) of the Pyrenees; assessing the relative contribution of phenology and environmental variables on CO2 exchange at the seasonal scale, and the influence of plant functional type dominance (grasses, forbs and legumes) on the NEE light response. Results show that phenology plays a crucial role as a CO2 exchange driver, suggesting a differential behaviour of the vegetation community depending on the environment. The subalpine grassland had a more delayed phenology compared to the montane, being more temperature than water constrained. However, temperature increased net CO2 uptake at a higher rate in the subalpine than in the montane grassland. During the peak biomass, productivity (+74%) and net CO2 uptake (NEE +48%) were higher in the subalpine grassland than in the montane grassland. The delayed phenology at the subalpine grassland reduced vegetation's sensitivity to summer dryness, and CO2 exchange fluxes were less constrained by low soil water content. The NEE light response suggested that legume dominated plots had higher net CO2 uptake per unit of biomass than grasses. Detailed information on phenology and vegetation composition is essential to understand elevation and climatic differences in CO2 exchange.
    Print ISSN: 0021-8596
    Electronic ISSN: 1469-5146
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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  • 10
    Publication Date: 2006-03-19
    Print ISSN: 1385-0237
    Electronic ISSN: 1573-5052
    Topics: Biology
    Published by Springer
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