ALBERT

Description: A method for predicting the factor of safety of an infinite slope based on the depth ratio of the wetting front induced by rainfall infiltration Natural Hazards and Earth System Science, 15, 1835-1849, 2015 Author(s): B.-G. Chae, J.-H. Lee, H.-J. Park, and J. Choi Most landslides in Korea are classified as shallow landslides with an average depth of less than 2 m. These shallow landslides are associated with the advance of a wetting front in the unsaturated soil due to rainfall infiltration, which results in an increase in water content and a reduction in the matric suction in the soil. Therefore, this study presents a modified equation of infinite slope stability analysis based on the concept of the saturation depth ratio to analyze the slope stability change associated with the rainfall on a slope. A rainfall infiltration test in unsaturated soil was performed using a column to develop an understanding of the effect of the saturation depth ratio following rainfall infiltration. The results indicated that the rainfall infiltration velocity due to the increase in rainfall in the soil layer was faster when the rainfall intensity increased. In addition, the rainfall infiltration velocity tends to decrease with increases in the unit weight of soil. The proposed model was applied to assess its feasibility and to develop a regional landslide susceptibility map using a geographic information system (GIS). For that purpose, spatial databases for input parameters were constructed and landslide locations were obtained. In order to validate the proposed approach, the results of the proposed approach were compared with the landslide inventory using a ROC (receiver operating characteristics) graph. In addition, the results of the proposed approach were compared with the previous approach used: a steady-state hydrological model. Consequently, the approach proposed in this study displayed satisfactory performance in classifying landslide susceptibility and showed better performance than the steady-state approach.

Description: Regional trends and controlling factors of fatal landslides in Latin America and the Caribbean Natural Hazards and Earth System Science, 15, 1821-1833, 2015 Author(s): S. A. Sepúlveda and D. N. Petley A new data set of landslides that caused loss of life in Latin America and the Caribbean in the 10-year period from 2004 and 2013 inclusive has been compiled, providing new insight into the impact of landslides in this key part of the world. This data set indicates that in the 10-year period a total of 11 631 people lost their lives across the region in 611 landslides. The geographical distribution of the landslides is highly heterogeneous, with areas of high incidence in parts of the Caribbean (most notably Haiti), Central America, Colombia, and southeast Brazil. There is significant interannual variation in the number of landslides, with the El Niño/La Niña cycle emerging as a key control. Our analysis suggests that on a continental scale the mapped factors that best explain the observed distribution are topography, annual precipitation and population density. On a national basis we have compared the occurrence of fatality-inducing landslide occurrence with the production of locally authored research articles, demonstrating that there is a landslide research deficit in Latin America and the Caribbean. Understanding better the mechanisms, distribution causes and triggers of landslides in Latin America and the Caribbean must be an essential first step towards managing the hazard.

Description: Spatial scales of temperature and salinity variability estimated from Argo observations Ocean Science Discussions, 12, 1793-1814, 2015 Author(s): F. Ninove, P. Y. Le Traon, E. Remy, and S. Guinehut Argo observations from 2005 to 2013 are used to characterize spatial scales temperature and salinity variations from the surface down to 1500 m. Simulations are first performed to analyze the sensitivity of results to Argo sampling; they show that several years of Argo observations are required to estimate the spatial scales of ocean variability over 20° × 20° boxes. Spatial scales are then computed over several large scale areas. Zonal and meridional spatial scales ( Lx and Ly which are also zero crossing of covariance functions) vary as expected with latitudes. Scales are of about 100 km at high latitudes and more of 700 km in the Indian and Pacific equatorial/tropical regions. Zonal and meridional scales are similar: except in these tropical/equatorial regions where zonal scales are much larger (by a factor of 2 to 3) than meridional scales. Spatial scales are the largest close to the surface and have a general tendency for temperature to increase in deeper layers. There are significant differences between temperature and salinity scales, in particular, in the deep ocean. Results are consistent with previous studies based on sparse in-situ observations or satellite altimetry. They provide, however, for the first time a global description of temperature and salinity scales of variability and a characterization of their variations according to depths.

Description: Evaluation of an operational ocean model configuration at 1/12° spatial resolution for the Indonesian seas – Part 2: Biogeochemistry Geoscientific Model Development Discussions, 8, 6669-6706, 2015 Author(s): E. Gutknecht, G. Reffray, M. Gehlen, I. Triyulianti, D. Berlianty, and P. Gaspar In the framework of the INDESO (Infrastructure evelopment of Space Oceanography) project, an operational ocean forecasting system was developed to monitor the state of the Indonesian seas in terms of circulation, biogeochemistry and fisheries. This forecasting system combines a suite of numerical models connecting physical and biogeochemical variables to population dynamics of large marine predators (tunas). The physical/biogeochemical coupled component (INDO12BIO configuration) covers a large region extending from the western Pacific Ocean to the Eastern Indian Ocean at 1/12° resolution. The OPA/NEMO physical ocean model and the PISCES biogeochemical model are coupled in "on-line" mode without degradation in space and time. The operational global ocean forecasting system (1/4°) operated by Mercator Ocean provides the physical forcing while climatological open boundary conditions are prescribed for the biogeochemistry. This paper describes the skill assessment of the INDO12BIO configuration. Model skill is assessed by evaluating a reference hindcast simulation covering the last 8 years (2007–2014). Model results are compared to satellite, climatological and in situ observations. Diagnostics are performed on chlorophyll a , primary production, mesozooplankton, nutrients and oxygen. Model results reproduce the main characteristics of biogeochemical tracer distributions in space and time. The seasonal cycle of chlorophyll a is in phase with satellite observations. The northern and southern parts of the archipelago present a distinct seasonal cycle, with higher chlorophyll biomass in the southern (northern) part during SE (NW) monsoon. Nutrient and oxygen concentrations are correctly reproduced in terms of horizontal and vertical distributions. The biogeochemical content of water masses entering in the archipelago as well as the water mass transformation across the archipelago conserves realistic vertical distribution in Banda Sea and at the exit of the archipelago.

Description: A numerical study of the early stages of a tropical cyclogenesis in relation to the MJO Natural Hazards and Earth System Sciences Discussions, 3, 4919-4935, 2015 Author(s): J. Guerbette, M. Plu, C. Barthe, and J.-F. Mahfouf The role of an active phase of the Madden–Julian Oscillation (MJO) on the evolution of a mesoscale convective systems (MCS) leading to a tropical depression is investigated in the South-West Indian Ocean during the Dynamics of the Madden–Julian Oscillation (DYNAMO) field experiment, with a numerical limited-area atmospheric model. A mesoscale vortex is followed in the low-troposphere from the initiation of the active MJO phase. It is shown that the interaction of the vortex with the Equatorial jet associated with the MJO plays an important role on the vortex development. As the vortex encounters the southern part of the low-level jet, it undergoes intensification that is explained by the barotropic conversion of kinetic energy from the low-level jet to the vortex.

Description: A semi-analytical model for diffuse reflectance in marine and inland waters Ocean Science Discussions, 12, 1893-1912, 2015 Author(s): J. D. Pravin, P. Shanmugam, and Y.-H. Ahn A semi-analytical model for predicting diffuse reflectance of coastal and oceanic waters is developed based on the water-column optical properties and illumination conditions. Diffuse reflectance ( R ) is an apparent optical property that is related to the Gordon's parameter ( b b /(a+b b ) ) through a proportionality factor " f ". The conventional assumption of " f " as a constant (0.33) yields large errors in case of turbid and productive coastal waters and a predictive model based on this assumption is generally restricted to open-ocean waters (low chlorophyll case). In this paper, we have sorted the dependent factors that influence " f " values in the water column. Here, the parameter " f " is modeled as a function of wavelength, depth, inherent optical properties (IOPs) and illumination conditions. This work eliminates the spectral constants ( K Chl and K SS ) associated with our previous model and constrains the present model to be solely dependent on the IOPs and illumination conditions. Data used for parameterization and validation are obtained from in situ measurements in different waters within coastal environments. Validation shows good agreement between the model R and in situ R values with the overall mean relative error of less than a few percent. The model is valid for a wide range waters within coastal and open-ocean environments.

Description: Impact of variable sea-water conductivity on motional induction simulated with an OGCM Ocean Science Discussions, 12, 1869-1891, 2015 Author(s): C. Irrgang, J. Saynisch, and M. Thomas Carrying high concentrations of dissolved salt, ocean water is a good electrical conductor. As sea-water flows through the Earth's ambient geomagnetic field, electric fields are generated, which in turn induce secondary magnetic fields. In current models for oceanic induced magnetic fields, a realistic consideration of sea-water conductivity is often neglected and the effect on the variability of the oceanic induced magnetic field unknown. To model magnetic fields that are induced by non-tidal global ocean currents, an electromagnetic induction model is implemented into the Ocean Model for Circulation and Tides (OMCT). This provides the opportunity to not only model oceanic induced magnetic signals, but to assess the impact of oceanographic phenomena on the induction process. In this paper, the sensitivity of the induction process due to spatial and temporal variations in sea-water conductivity is investigated. It is shown that assuming an ocean-wide uniform conductivity is insufficient to accurately capture the temporal variability of the magnetic signal. Using instead a realistic global sea-water conductivity distribution increases the temporal variability of the magnetic field up to 45 %. Especially vertical gradients in sea-water conductivity prove to be a key factor for the variability of the oceanic induced magnetic field. However, temporal variations of sea-water conductivity only marginally affect the magnetic signal.

Description: A new model of the global biogeochemical cycle of carbonyl sulfide – Part 2: Use of carbonyl sulfide to constrain gross primary productivity in current vegetation models Atmospheric Chemistry and Physics, 15, 9285-9312, 2015 Author(s): T. Launois, P. Peylin, S. Belviso, and B. Poulter Clear analogies between carbonyl sulfide (OCS) and carbon dioxide (CO 2 ) diffusion pathways through leaves have been revealed by experimental studies, with plant uptake playing an important role for the atmospheric budget of both species. Here we use atmospheric OCS to evaluate the gross primary production (GPP) of three dynamic global vegetation models (Lund–Potsdam–Jena, LPJ; National Center for Atmospheric Research – Community Land Model 4, NCAR-CLM4; and Organising Carbon and Hydrology In Dynamic Ecosystems, ORCHIDEE). Vegetation uptake of OCS is modeled as a linear function of GPP and leaf relative uptake (LRU), the ratio of OCS to CO 2 deposition velocities of plants. New parameterizations for the non-photosynthetic sinks (oxic soils, atmospheric oxidation) and biogenic sources (oceans and anoxic soils) of OCS are also provided. Despite new large oceanic emissions, global OCS budgets created with each vegetation model show exceeding sinks by several hundred Gg S yr −1 . An inversion of the surface fluxes (optimization of a global scalar which accounts for flux uncertainties) led to balanced OCS global budgets, as atmospheric measurements suggest, mainly by drastic reduction (up to −50 %) in soil and vegetation uptakes. The amplitude of variations in atmospheric OCS mixing ratios is mainly dictated by the vegetation sink over the Northern Hemisphere. This allows for bias recognition in the GPP representations of the three selected models. The main bias patterns are (i) the terrestrial GPP of ORCHIDEE at high northern latitudes is currently overestimated, (ii) the seasonal variations of the GPP are out of phase in the NCAR-CLM4 model, showing a maximum carbon uptake too early in spring in the northernmost ecosystems, (iii) the overall amplitude of the seasonal variations of GPP in NCAR-CLM4 is too small, and (iv) for the LPJ model, the GPP is slightly out of phase for the northernmost ecosystems and the respiration fluxes might be too large in summer in the Northern Hemisphere. These results rely on the robustness of the OCS modeling framework and, in particular, the choice of the LRU values (assumed constant in time) and the parameterization of soil OCS uptake with small seasonal variations. Refined optimization with regional-scale and seasonally varying coefficients might help to test some of these hypothesis.

Description: Upper tropospheric water vapour variability at high latitudes – Part 1: Influence of the annular modes Atmospheric Chemistry and Physics Discussions, 15, 22291-22329, 2015 Author(s): C. E. Sioris, J. Zou, D. A. Plummer, C. D. Boone, C. T. McElroy, P. E. Sheese, O. Moeini, and P. F. Bernath Seasonal and monthly zonal medians of water vapour in the upper troposphere and lower stratosphere (UTLS) are calculated for both Atmospheric Chemistry Experiment (ACE) instruments for the northern and southern high-latitude regions (60–90 and 60–90° S). Chosen for the purpose of observing high-latitude processes, the ACE orbit provides sampling of both regions in eight of 12 months of the year, with coverage in all seasons. The ACE water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS) are currently the only satellite instruments that can probe from the lower stratosphere down to the mid-troposphere to study the vertical profile of the response of UTLS water vapour to the annular modes. The Arctic oscillation (AO), also known as the northern annular mode (NAM), explains 64 % ( r = −0.80) of the monthly variability in water vapour at northern high-latitudes observed by ACE-MAESTRO between 5 and 7 km using only winter months (January to March 2004–2013). Using a seasonal timestep and all seasons, 45 % of the variability is explained by the AO at 6.5 ± 0.5 km, similar to the 46 % value obtained for southern high latitudes at 7.5 ± 0.5 km explained by the Antarctic oscillation or southern annular mode (SAM). A large negative AO event in March 2013 produced the largest relative water vapour anomaly at 5.5 km (+70 %) over the ACE record. A similarly large event in the 2010 boreal winter, which was the largest negative AO event in the record (1950–2015), led to 〉 50 % increases in water vapour observed by MAESTRO and ACE-FTS at 7.5 km.

Description: Decadal evaluation of regional climate, air quality, and their interactions using WRF/Chem Version 3.6.1 Geoscientific Model Development Discussions, 8, 6707-6756, 2015 Author(s): K. Yahya, K. Wang, P. Campbell, T. Glotfelty, J. He, and Y. Zhang The Weather Research and Forecasting model with Chemistry (WRF/Chem) v3.6.1 with the Carbon Bond 2005 (CB05) gas-phase mechanism is evaluated for its first decadal application during 2001–2010 using the Representative Concentration Pathway (RCP 8.5) emissions to assess its capability and appropriateness for long-term climatological simulations. The initial and boundary conditions are downscaled from the modified Community Earth System Model/Community Atmosphere Model (CESM/CAM5) v1.2.2. The meteorological initial and boundary conditions are bias-corrected using the National Center for Environmental Protection's Final (FNL) Operational Global Analysis data. Climatological evaluations are carried out for meteorological, chemical, and aerosol-cloud-radiation variables against data from surface networks and satellite retrievals. The model performs very well for the 2 m temperature (T2) for the 10 year period with only a small cold bias of −0.3 °C. Biases in other meteorological variables including relative humidity at 2 m, wind speed at 10 m, and precipitation tend to be site- and season-specific; however, with the exception of T2, consistent annual biases exist for most of the years from 2001 to 2010. Ozone mixing ratios are slightly overpredicted at both urban and rural locations but underpredicted at rural locations. PM 2.5 concentrations are slightly overpredicted at rural sites, but slightly underpredicted at urban/suburban sites. In general, the model performs relatively well for chemical and meteorological variables, and not as well for aerosol-cloud-radiation variables. Cloud-aerosol variables including aerosol optical depth, cloud water path, cloud optical thickness, and cloud droplet number concentration are generally underpredicted on average across the continental US. Overpredictions of several cloud variables over eastern US result in underpredictions of radiation variables and overpredictions of shortwave and longwave cloud forcing which are important climate variables. While the current performance is deemed to be acceptable, improvements to the bias-correction method for CESM downscaling and the model parameterizations of cloud dynamics and thermodynamics, as well as aerosol-cloud interactions can potentially improve model performance for long-term climate simulations.

Description: Retrieving the paleoclimatic signal from the deeper part of the EPICA Dome C ice core The Cryosphere, 9, 1633-1648, 2015 Author(s): J.-L. Tison, M. de Angelis, G. Littot, E. Wolff, H. Fischer, M. Hansson, M. Bigler, R. Udisti, A. Wegner, J. Jouzel, B. Stenni, S. Johnsen, V. Masson-Delmotte, A. Landais, V. Lipenkov, L. Loulergue, J.-M. Barnola, J.-R. Petit, B. Delmonte, G. Dreyfus, D. Dahl-Jensen, G. Durand, B. Bereiter, A. Schilt, R. Spahni, K. Pol, R. Lorrain, R. Souchez, and D. Samyn An important share of paleoclimatic information is buried within the lowermost layers of deep ice cores. Because improving our records further back in time is one of the main challenges in the near future, it is essential to judge how deep these records remain unaltered, since the proximity of the bedrock is likely to interfere both with the recorded temporal sequence and the ice properties. In this paper, we present a multiparametric study (δD-δ 18 O ice , δ 18 O atm , total air content, CO 2 , CH 4 , N 2 O, dust, high-resolution chemistry, ice texture) of the bottom 60 m of the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core from central Antarctica. These bottom layers were subdivided into two distinct facies: the lower 12 m showing visible solid inclusions (basal dispersed ice facies) and the upper 48 m, which we will refer to as the "basal clean ice facies". Some of the data are consistent with a pristine paleoclimatic signal, others show clear anomalies. It is demonstrated that neither large-scale bottom refreezing of subglacial water, nor mixing (be it internal or with a local basal end term from a previous/initial ice sheet configuration) can explain the observed bottom-ice properties. We focus on the high-resolution chemical profiles and on the available remote sensing data on the subglacial topography of the site to propose a mechanism by which relative stretching of the bottom-ice sheet layers is made possible, due to the progressively confining effect of subglacial valley sides. This stress field change, combined with bottom-ice temperature close to the pressure melting point, induces accelerated migration recrystallization, which results in spatial chemical sorting of the impurities, depending on their state (dissolved vs. solid) and if they are involved or not in salt formation. This chemical sorting effect is responsible for the progressive build-up of the visible solid aggregates that therefore mainly originate "from within", and not from incorporation processes of debris from the ice sheet's substrate. We further discuss how the proposed mechanism is compatible with the other ice properties described. We conclude that the paleoclimatic signal is only marginally affected in terms of global ice properties at the bottom of EPICA Dome C, but that the timescale was considerably distorted by mechanical stretching of MIS20 due to the increasing influence of the subglacial topography, a process that might have started well above the bottom ice. A clear paleoclimatic signal can therefore not be inferred from the deeper part of the EPICA Dome C ice core. Our work suggests that the existence of a flat monotonic ice–bedrock interface, extending for several times the ice thickness, would be a crucial factor in choosing a future "oldest ice" drilling location in Antarctica.

Description: Impacts of an unknown daytime HONO source on the mixing ratio and budget of HONO, and hydroxyl, hydroperoxyl, and organic peroxy radicals, in the coastal regions of China Atmospheric Chemistry and Physics, 15, 9381-9398, 2015 Author(s): Y. Tang, J. An, F. Wang, Y. Li, Y. Qu, Y. Chen, and J. Lin Many field experiments have found high nitrous acid (HONO) mixing ratios in both urban and rural areas during daytime, but these high daytime HONO mixing ratios cannot be explained well by gas-phase production, HONO emissions, and nighttime hydrolysis conversion of nitrogen dioxide (NO 2 ) on aerosols, suggesting that an unknown daytime HONO source ( P unknown ) could exist. The formula P unknown ≈ 19.60[NO 2 ] · J (NO 2 ) was obtained using observed data from 13 field experiments across the globe. The three additional HONO sources (i.e., the P unknown , nighttime hydrolysis conversion of NO 2 on aerosols, and HONO emissions) were coupled into the WRF-Chem model (Weather Research and Forecasting model coupled with Chemistry) to assess the P unknown impacts on the concentrations and budgets of HONO and peroxy (hydroxyl, hydroperoxyl, and organic peroxy) radicals (RO x ) (= OH + HO 2 + RO 2 ) in the coastal regions of China. Results indicated that the additional HONO sources produced a significant improvement in HONO and OH simulations, particularly in the daytime. High daytime average P unknown values were found in the coastal regions of China, with a maximum of 2.5 ppb h −1 in the Beijing–Tianjin–Hebei region. The P unknown produced a 60–250 % increase of OH, HO 2 , and RO 2 near the ground in the major cities of the coastal regions of China, and a 5–48 % increase of OH, HO 2 , and RO 2 in the daytime meridional-mean mixing ratios within 1000 m above the ground. When the three additional HONO sources were included, the photolysis of HONO was the second most important source in the OH production rate in Beijing, Shanghai, and Guangzhou before 10:00 LST with a maximum of 3.72 ppb h −1 and a corresponding P unknown contribution of 3.06 ppb h −1 in Beijing, whereas the reaction of HO 2 + NO (nitric oxide) was dominant after 10:00 LST with a maximum of 9.38 ppb h −1 and a corresponding P unknown contribution of 7.23 ppb h −1 in Beijing. The whole RO x cycle was accelerated by the three additional HONO sources, especially the P unknown . The daytime average OH production rate was enhanced by 0.67 due to the three additional HONO sources; [0.64], due to the P unknown , to 4.32 [3.86] ppb h −1 , via the reaction of HO 2 + NO, and by 0.49 [0.47] to 1.86 [1.86] ppb h −1 , via the photolysis of HONO. The OH daytime average loss rate was enhanced by 0.58 [0.55] to 2.03 [1.92] ppb h −1 , via the reaction of OH + NO 2 , and by 0.31 [0.28] to 1.78 [1.64] ppb h −1 , via the reaction of OH + CO (carbon monoxide) in Beijing, Shanghai, and Guangzhou. Similarly, the three additional HONO sources produced an increase of 0.31 [0.28] (with a corresponding P unknown contribution) to 1.78 [1.64] ppb h −1 , via the reaction of OH + CO, and 0.10 [0.09] to 0.63 [0.59] ppb h −1 , via the reaction of CH 3 O 2 (methylperoxy radical) + NO in the daytime average HO 2 production rate, and 0.67 [0.61] to 4.32 [4.27] ppb h −1 , via the reaction of HO 2 + NO in the daytime average HO 2 loss rate in Beijing, Shanghai, and Guangzhou. The above results suggest that the P unknown considerably enhanced the RO x concentrations and accelerated RO x cycles in the coastal regions of China, and could produce significant increases in concentrations of inorganic aerosols and secondary organic aerosols and further aggravate haze events in these regions.

Description: A modification to the standard ionospheric correction method used in GPS radio occultation Atmospheric Measurement Techniques, 8, 3385-3393, 2015 Author(s): S. B. Healy and I. D. Culverwell A modification to the standard bending-angle correction used in GPS radio occultation (GPS-RO) is proposed. The modified approach should reduce systematic residual ionospheric errors in GPS radio occultation climatologies. A new second-order term is introduced in order to account for a known source of systematic error, which is generally neglected. The new term has the form κ(a) × (α L1 (a)-α L2 (a)) 2 , where a is the impact parameter and (α L1 , α L2 ) are the L1 and L2 bending angles, respectively. The variable κ is a weak function of the impact parameter, a , but it does depend on a priori ionospheric information. The theoretical basis of the new term is examined. The sensitivity of κ to the assumed ionospheric parameters is investigated in one-dimensional simulations, and it is shown that κ ≃ 10–20 rad −1 . We note that the current implicit assumption is κ=0, and this is probably adequate for numerical weather prediction applications. However, the uncertainty in κ should be included in the uncertainty estimates for the geophysical climatologies produced from GPS-RO measurements. The limitations of the new ionospheric correction when applied to CHAMP (Challenging Minisatellite Payload) measurements are noted. These arise because of the assumption that the refractive index is unity at the satellite, made when deriving bending angles from the Doppler shift values.

Description: Nitrogen cycling in the subsurface biosphere: nitrate isotopes in porewaters underlying the oligotrophic North Atlantic Biogeosciences Discussions, 12, 13545-13591, 2015 Author(s): S. D. Wankel, C. Buchwald, W. Ziebis, C. B. Wenk, and M. F. Lehmann Nitrogen (N) is a key component of fundamental biomolecules. Hence, the cycling and availability of N is a central factor governing the extent of ecosystems across the Earth. In the organic-lean sediment porewaters underlying the oligotrophic ocean, where low levels of microbial activity persist despite limited organic matter delivery from overlying water, the extent and modes of nitrogen transformations have not been widely investigated. Here we use the N and oxygen (O) isotopic composition of porewater nitrate (NO 3 − ) from a site in the oligotrophic North Atlantic (IODP) to determine the extent and magnitude of microbial nitrate production (via nitrification) and consumption (via denitrification). We find that NO 3 − accumulates far above bottom seawater concentrations (∼ 21 μM) throughout the sediment column (up to ∼ 50 μM) down to the oceanic basement as deep as 90 mbsf, reflecting the predominance of aerobic nitrification/remineralization within the deep marine sediments. Large changes in the δ 15 N and δ 18 O of nitrate, however, reveal variable influence of nitrate respiration across the three sites. We use an inverse porewater diffusion–reaction model, constrained by the N and O isotope systematics of nitrification and denitrification and the porewater NO 3 − isotopic composition, to estimate rates of nitrification and denitrification throughout the sediment column. Results indicate variability of reaction rates across and within the three boreholes that are generally consistent with the differential distribution of dissolved oxygen at this site, though not necessarily with the canonical view of how redox thresholds separate nitrate regeneration from dissimilative consumption spatially. That is, we provide isotope evidence for expanded zones of co-ocurring nitrification and denitrification. The isotope biogeochemical modeling also yielded estimates for the δ 15 N and δ 18 O of newly produced nitrate (δ 15 N NTR and δ 18 O NTR ), as well as the isotope effect for denitrification ( 15 ϵ DNF ), parameters with high relevance to global ocean models of N cycling. Estimated values of δ 15 N NTR were generally lower than previously reported δ 15 N values for sinking PON in this region. We suggest that these values can be related to sedimentary N-fixation and remineralization of the newly fixed organic N. Values of δ 18 O NTR generally ranged between −2.8 and 0.0 ‰, consistent with recent estimates based on lab cultures of nitrifying bacteria. Notably, some δ 18 O NTR values were elevated, suggesting incorporation of 18 O-enriched dissolved oxygen during nitrification, and possibly indicating a tight coupling of NH 4 + and NO 2 − oxidation in this metabolically sluggish environment. Our findings indicate that the production of organic matter by in situ autotrophy (e.g., nitrification, nitrogen fixation) supply a large fraction of the biomass and organic substrate for heterotrophy in these sediments, supplementing the small organic matter pool derived from the overlying euphotic zone. This work sheds new light on an active nitrogen cycle operating, despite exceedingly low carbon inputs, in the deep sedimentary biosphere.

Description: Editorial Note "A novel Whole Air Sample Profiler (WASP) for the quantification of volatile organic compounds in the boundary layer" published in Atmos. Meas. Tech., 6, 2703–2712, 2013 Atmospheric Measurement Techniques, 8, 3405-3406, 2015 Author(s): T. Wagner, H. Harder, J. Joiner, P. Laj, and A. Richter No abstract available.

Description: Spring bloom onset in the Nordic Seas Biogeosciences Discussions, 12, 13631-13673, 2015 Author(s): A. Mignot, R. Ferrari, and K. A. Mork The North Atlantic spring bloom is a massive annual growth event of marine phytoplankton, tiny free-floating algae that form the base of the ocean's food web and generates a large fraction of the global primary production of organic matter. The conditions that trigger the onset of the spring bloom in the Nordic Seas, at the northern edge of the North Atlantic, are studied using in-situ data from five bio-optical floats released above the Arctic Circle. It is often assumed that spring blooms start as soon as phytoplankton cells daily irradiance is sufficiently abundant that division rates exceed losses. The bio-optical float data instead suggest the tantalizing hypothesis that Nordic Seas blooms start when the photoperiod, the number of daily light hours experienced by phytoplankton, exceeds a critical value, independently of division rates. This bloom behavior may be explained by realizing that photosynthesis is impossible during polar nights and phytoplankton enters in a dormant stage in winter, only to be awaken by a photoperiodic trigger. While the first accumulation of biomass recorded by the bio-optical floats is consistent with the photoperiod hypothesis, it is possible that some biomass accumulation started before the critical photoperiod but at levels too low to be detected by the fluorometers. Thus more precise observations are needed to test the photoperiod hypothesis.

Description: A fuzzy intelligent system for land consolidation – a case study in Shunde, China Solid Earth, 6, 997-1006, 2015 Author(s): J. Wang, A. Ge, Y. Hu, C. Li, and L. Wang Traditionally, potential evaluation methods for farmland consolidation have depended mainly on the experts' experiences, statistical computations or subjective adjustments. Some biases usually exist in the results. Thus, computer-aided technology has become essential. In this study, an intelligent evaluation system based on a fuzzy decision tree was established, and this system can deal with numerical data, discrete data and symbolic data. When the original land data are input, the level of potential of the agricultural land for development will be output by this new model. The provision of objective proof for decision-making by authorities in rural management is helpful. Agricultural land data characteristically comprise large volumes, complex varieties and more indexes. In land consolidation, it is very important to construct an effective index system. A group of indexes need to be selected for land consolidation. In this article, a fuzzy measure was adopted to accomplish the selection of specific features. A fuzzy integral based on a fuzzy measure is a type of fusion tool. The optimal solution with the fewest non-zero elements was obtained for the fuzzy measure by solving a fuzzy integral. This algorithm provides a quick and optimal way to identify the land-index system when preparing to conduct land consolidation. This new research was applied to Shunde's "Three Old" consolidation project which provides the data. Our estimation system was compared with a conventional evaluation system that is still accepted by the public. Our results prove to be consistent, and the new model is more automatic and intelligent. The results of this estimation system are significant for informing decision-making in land consolidation.

Description: Impact of debris cover on glacier ablation and atmosphere–glacier feedbacks in the Karakoram The Cryosphere, 9, 1617-1632, 2015 Author(s): E. Collier, F. Maussion, L. I. Nicholson, T. Mölg, W. W. Immerzeel, and A. B. G. Bush The Karakoram range of the Hindu-Kush Himalaya is characterized by both extensive glaciation and a widespread prevalence of surficial debris cover on the glaciers. Surface debris exerts a strong control on glacier surface-energy and mass fluxes and, by modifying surface boundary conditions, has the potential to alter atmosphere–glacier feedbacks. To date, the influence of debris on Karakoram glaciers has only been directly assessed by a small number of glaciological measurements over short periods. Here, we include supraglacial debris in a high-resolution, interactively coupled atmosphere–glacier modeling system. To investigate glaciological and meteorological changes that arise due to the presence of debris, we perform two simulations using the coupled model from 1 May to 1 October 2004: one that treats all glacier surfaces as debris-free and one that introduces a simplified specification for the debris thickness. The basin-averaged impact of debris is a reduction in ablation of ~ 14 %, although the difference exceeds 5 m w.e. on the lowest-altitude glacier tongues. The relatively modest reduction in basin-mean mass loss results in part from non-negligible sub-debris melt rates under thicker covers and from compensating increases in melt under thinner debris, and may help to explain the lack of distinct differences in recent elevation changes between clean and debris-covered ice. The presence of debris also strongly alters the surface boundary condition and thus heat exchanges with the atmosphere; near-surface meteorological fields at lower elevations and their vertical gradients; and the atmospheric boundary layer development. These findings are relevant for glacio-hydrological studies on debris-covered glaciers and contribute towards an improved understanding of glacier behavior in the Karakoram.

Description: Introduction: The Pan-Eurasian Experiment (PEEX) – multi-disciplinary, multi-scale and multi-component research and capacity building initiative Atmospheric Chemistry and Physics Discussions, 15, 22567-22596, 2015 Author(s): M. Kulmala, H. K. Lappalainen, T. Petäjä, T. Kurten, V.-M. Kerminen, Y. Viisanen, P. Hari, V. Bondur, N. Kasimov, V. Kotlyakov, G. Matvienko, A. Baklanov, H. D. Guo, A. Ding, H.-C. Hansson, and S. Zilitinkevich The Pan-Eurasian Experiment (PEEX) is a multi-disciplinary, multi-scale and multi-component research, research infrastructure and capacity building program. PEEX has originated from a bottom-up approach by the science communities, and is aiming at resolving the major uncertainties in Earth System Science and global sustainability issues concerning the Arctic and boreal Pan-Eurasian regions, as well as China. The vision of PEEX is to solve interlinked global grand challenges influencing human well-being and societies in northern Eurasia and China. Such challenges include climate change, air quality, biodiversity loss, urbanization, chemicalization, food and fresh water availability, energy production and use of natural resources by mining, industry, energy production and transport sectors. Our approach is integrative and supra-disciplinary, recognizing the important role of the Arctic and boreal ecosystems in the Earth system. The PEEX vision includes establishing and maintaining long-term, coherent and coordinated research activities as well as continuous, comprehensive research and educational infrastructures and related capacity building across the PEEX domain. In this paper we present the PEEX structure, summarize its motivation, objectives and future outlook.

Description: Particulate organic nitrates observed in an oil and natural gas production region during wintertime Atmospheric Chemistry and Physics, 15, 9313-9325, 2015 Author(s): L. Lee, P. J. Wooldridge, J. deGouw, S. S. Brown, T. S. Bates, P. K. Quinn, and R. C. Cohen Organic nitrates in both gas and condensed (aerosol) phases were measured during the Uintah Basin Winter Ozone Study from January to February in 2012. A high degree of correlation between total aerosol volume at diameters less than 500 nm and the particulate organic nitrate concentration indicates that organic nitrates are a consistent, if not dominant, fraction of fine aerosol mass. In contrast, a similar correlation with sub-2.5 μm aerosol volume is weaker. The C : N atomic ratio inferred from field measurements of PM 2.5 and particulate organic nitrate is 34 : 1. Calculations constrained by the observations indicate that both condensation of gas-phase nitrates and heterogeneous reactions of NO 3 / N 2 O 5 are responsible for introducing organic nitrate functionality into the aerosol and that the source molecules are alkanes. Extrapolating the results to urban aerosol suggests organic nitrate production from alkanes may be a major secondary organic aerosol source.

Description: The influences of mass loading and rapid dilution of secondary organic aerosol on particle volatility Atmospheric Chemistry and Physics, 15, 9327-9343, 2015 Author(s): K. R. Kolesar, C. Chen, D. Johnson, and C. D. Cappa The thermally induced evaporation of secondary organic aerosol (SOA) has been characterized for SOA formed from the dark ozonolysis of α-pinene at initial mass concentrations ranging from 1 to 800 μg m −3 . Temperature-dependent particle size distributions were measured using a thermodenuder and the resulting mass thermograms were compared between the SOA formed at the various SOA mass concentrations. Negligible differences were observed between the mass thermograms for SOA concentrations 〈 300 μg m −3 . At higher SOA concentrations, the observed mass thermograms indicated the SOA was actually slightly less volatile than the SOA at lower concentrations; this is likely an artifact due to either saturation of the gas phase or to recondensation during cooling. The thermograms observed when the SOA was formed at high concentrations (〉 380 μg m −3 ) and then rapidly isothermally diluted to low concentrations (1–20 μg m −3 ) were identical to those for the SOA that was initially formed at low concentrations. The experimental results were compared to a kinetic model that simulates particle evaporation upon heating in a thermodenuder for a given input volatility distribution and particle composition. Three cases were considered: (1) the SOA was composed of semi-volatile monomer species with a volatility distribution based on that derived previously from consideration of SOA growth experiments; (2) the initial SOA was composed almost entirely of non-volatile dimers that decompose upon heating into their semi-volatile monomer units, which can then evaporate; and (3) where a volatility distribution was derived by fitting the model to the observed mass thermograms. It was found that good agreement is obtained between model predictions and the observations when the particle composition is dominated by either compounds of low volatility or by dimers. These same models were used to simulate isothermal evaporation of the SOA and were found to be broadly consistent with literature observations that indicate that SOA evaporation occurs with multiple timescales. The use of the semi-volatile monomer volatility distribution fails to reproduce the observed evaporation. The presence of dimers and larger oligomers in secondary organic aerosol formed from products of the reaction of α-pinene and O 3 has been well established in laboratory studies. However, the timescale and relative importance of the formation of oligomers or low-volatility compounds in the growth and evaporation of SOA has been debated. This study provides further support that low-volatility compounds and oligomers are formed in α-pinene + O 3 in high abundances and suggests that their formation occurs rapidly upon particle formation.

Description: Possible influence of atmospheric circulations on winter hazy pollution in Beijing-Tianjin-Hebei region, northern China Atmospheric Chemistry and Physics Discussions, 15, 22493-22526, 2015 Author(s): Z. Zhang, X. Zhang, D. Gong, S.-J. Kim, R. Mao, and X. Zhao Using the daily records derived from the synoptic weather stations and the NCEP/NCAR and ERA-Interim reanalysis data, the variability of the winter hazy pollutions (indicated by the mean visibility and number of hazy days) in Beijing-Tianjin-Hebei (BTH) region during the period 1981 to 2015 and its relationship to the atmospheric circulations in middle-high latitude were analyzed in this study. The winter hazy pollution in BTH had distinct inter-annual and inter-decadal variabilities without a significant long-term trend. According to the spatial distribution of correlation coefficients, six atmospheric circulation indices ( I 1 to I 6 ) were defined from the key areas in sea level pressure (SLP), zonal and meridional winds at 850 hPa (U850, V850), geopotential height field at 500 hPa (H500), zonal wind at 200 hPa (U200), and air temperature at 200 hPa (T200), respectively. All of the six indices have significant and stable correlations with the winter visibility and number of hazy days in BTH. Both the visibility and number of hazy days can be estimated well by using the six indices and fitting and the cross-validation with leave- N -out method, respectively. The high level of the prediction statistics and the reasonable mechanism suggested that the winter hazy pollutions in BTH can be forecasted or estimated credibly based on the optimized atmospheric circulation indices. However, we also noted that the statistic estimation models would be largely influenced by the artificial control of a pollutant discharge. Thus it is helpful for government decision-making departments to take actions in advance in dealing with probably severe hazy pollutions in BTH indicated by the atmospheric circulation conditions.

Description: The radiative impact of desert dust on orographic rain in the Cevennes–Vivarais area: a case study from HyMeX Atmospheric Chemistry and Physics Discussions, 15, 22451-22492, 2015 Author(s): C. Flamant, J.-P. Chaboureau, P. Chazette, P. Di Girolamo, T. Bourrianne, J. Totems, and M. Cacciani The study is focused on Intensive Observation Period (IOP) 14 of the Hydrology Cycle in the Mediterranean Experiment first Special Observing Period (HyMeX SOP 1) that took place from 17 to 19 October and was dedicated to the study of orographic rain in the Cevennes Vivarais (CV) target area. During this IOP a dense dust plume originating from North Africa (Maghreb and Sahara) was observed to be transported over the Balearic Islands towards the south of France. The plume was characterized by an aerosol optical depth between 0.2 and 0.8 at 550 nm, highly variable in time and space over the Western Mediterranean basin. The impact of this dust plume, the biggest event observed during the 2 month long HyMeX SOP 1, on the precipitation over the CV area has been analyzed using high resolution simulations from the convection permitting mesoscale model Meso-NH validated against measurements obtained from numerous instruments deployed specifically during SOP 1 (ground-based/airborne water vapor and aerosol lidars, airborne microphysics probes) as well as space-borne aerosol products. The 4 day simulation reproduced realistically the temporal and spatial variability (incl. vertical distribution) of the dust. The dust radiative impact led to an average 0.6 K heating at the altitude of the dust layer in the CV area (and up to +3 K locally) and an average 100 J kg -1 increase of most unstable convective available potential energy (and up to +900 J kg -1 locally) with respect to a simulation without prescribed dust aerosols. The rainfall amounts and location were only marginally affected by the dust radiative effect, even after 4 days of simulation. The transient nature of this radiative effect in dynamical environments such as those found in the vicinity of heavy precipitation events in the Mediterranean is not sufficient to impact 24 h accumulated rainfall in the dusty simulation.

Description: Global validation of SCIAMACHY limb ozone data (versions 2.9 and 3.0, IUP Bremen) using ozonesonde measurements Atmospheric Measurement Techniques, 8, 3369-3383, 2015 Author(s): J. Jia, A. Rozanov, A. Ladstätter-Weißenmayer, and J. P. Burrows In this paper, the latest SCIAMACHY limb ozone scientific vertical profiles, namely the current V2.9 and the upcoming V3.0, are extensively compared with ozonesonde data from the World Ozone and Ultraviolet Radiation Data Centre (WOUDC) database. The comparisons are made on a global scale from 2003 to 2011, involving 61 sonde stations. The retrieval processors used to generate V2.9 and V3.0 data sets are briefly introduced. The comparisons are discussed in terms of vertical profiles and stratospheric partial columns. Our results indicate that the V2.9 ozone profile data between 20 and 30 km are in good agreement with ground-based measurements, with less than 5 % relative differences in the latitude range of 90° S–40° N (with the exception of the tropical Pacific region, where an overestimation of more than 10 % is observed), which corresponds to less than 5 DU partial-column differences. In the tropics the differences are within 3 %. However, this data set shows a significant underestimation northwards of 40° N (up to ~ 15 %). The newly developed V3.0 data set reduces this bias to below 10 % while maintaining a good agreement southwards of 40° N with slightly increased relative differences of up to 5 % in the tropics.

Description: Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica Biogeosciences Discussions, 12, 13593-13629, 2015 Author(s): J. Elster, L. Nedbalová, R. Vodrážka, K. Láska, J. Haloda, and J. Komárek The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom eight-nine months per year and their water chemistry is characterized by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial mat is composed of filamentous cyanobacteria and microalgae that are considered to be Antarctic endemic species. The mucilaginous black biofilm is covered by green spots formed by a green microalga and the macroscopic structures are packed together with fine material. Thin sections consist of rock substrate, soft biofilm, calcite spicules and mineral grains originating from different sources. The morphology of the spicules is typical of calcium carbonate monocrystals having a layered structure and worn surface, which reflect growth and degradation processes. The spicules chemical composition and structure correspond to pure calcite. Lakes age, altitude, morphometry, geomorphological and hydrological stability, including low sedimentation rates, together with thermal regime predispose the existence of this community. We hypothesize that the precipitation of calcite is connected with the photosynthetic activity of the green microalgae that were not recorded in any other lake in the region. This study has shown that the unique community producing biogenic calcite spicules is quite different to any yet described.

Description: The GEWEX LandFlux project: evaluation of model evaporation using tower-based and globally-gridded forcing data Geoscientific Model Development Discussions, 8, 6809-6866, 2015 Author(s): M. F. McCabe, A. Ershadi, C. Jimenez, D. G. Miralles, D. Michel, and E. F. Wood Determining the spatial distribution and temporal development of evaporation at regional and global scales is required to improve our understanding of the coupled water and energy cycles and to better monitor any changes in observed trends and variability of linked hydrological processes. With recent international efforts guiding the development of long-term and globally distributed flux estimates, continued product assessments are required to inform upon the selection of suitable model structures and also to establish the appropriateness of these multi-model simulations for global application. In support of the objectives of the GEWEX LandFlux project, four commonly used evaporation models are evaluated against data from tower-based eddy-covariance observations, distributed across a range of biomes and climate zones. The selected schemes include the Surface Energy Balance System (SEBS) approach, the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model, the Penman-Monteith based Mu model (PM-Mu) and the Global Land Evaporation: the Amsterdam Methodology (GLEAM). Here we seek to examine the fidelity of global evaporation simulations by examining the multi-model response to varying sources of forcing data. To do this, we perform parallel and collocated model simulations using tower-based data together with a global-scale grid-based forcing product. Through quantifying the multi-model response to high-quality tower data, a better understanding of the subsequent model response to coarse-scale globally gridded data that underlies the LandFlux product can be obtained, while also providing a relative evaluation and assessment of model performance. Using surface flux observations from forty-five globally distributed eddy-covariance stations as independent metrics of performance, the tower-based analysis indicated that PT-JPL provided the highest overally statistical performance (0.72; 61 W m −2 ; 0.65), followed closely by GLEAM (0.68; 64 W m −2 ; 0.62), with values in parenthesis representing the R 2 , RMSD and Nash-Sutcliffe Efficiency (NSE) and respectively. PM-Mu (0.51; 78 W m −2 ; 0.45) tended to underestimate fluxes, while SEBS (0.72; 101 W m −2 ; 0.24) overestimated values relative to observations. A focused analysis across specific biome types and climate zones showed considerable variability in the performance of all models, with no single model consistently able to outperform any other. Results also indicated that the global gridded data tended to reduce the performance for all of the studied models when compared to the tower data, likely a response to scale mismatch and issues related to forcing quality. Rather than relying on any single model simulation, the spatial and temporal variability at both the tower- and grid-scale highlighted the potential benefits of developing an ensemble or blended evaporation product for global scale LandFlux applications. Challenges related to the robust assessment of the LandFlux product are also discussed.

Description: Drought assessment in the Dongliao River basin: traditional approaches vs. generalized drought assessment index based on water resources systems Natural Hazards and Earth System Science, 15, 1889-1906, 2015 Author(s): B. S. Weng, D. H. Yan, H. Wang, J. H. Liu, Z. Y. Yang, T. L. Qin, and J. Yin Drought is firstly a resource issue, and with its development it evolves into a disaster issue. Drought events usually occur in a determinate but a random manner. Drought has become one of the major factors to affect sustainable socioeconomic development. In this paper, we propose the generalized drought assessment index (GDAI) based on water resources systems for assessing drought events. The GDAI considers water supply and water demand using a distributed hydrological model. We demonstrate the use of the proposed index in the Dongliao River basin in northeastern China. The results simulated by the GDAI are compared to observed drought disaster records in the Dongliao River basin. In addition, the temporal distribution of drought events and the spatial distribution of drought frequency from the GDAI are compared with the traditional approaches in general (i.e., standard precipitation index, Palmer drought severity index and rate of water deficit index). Then, generalized drought times, generalized drought duration, and generalized drought severity were calculated by theory of runs. Application of said runs at various drought levels (i.e., mild drought, moderate drought, severe drought, and extreme drought) during the period 1960–2010 shows that the centers of gravity of them all distribute in the middle reaches of Dongliao River basin, and change with time. The proposed methodology may help water managers in water-stressed regions to quantify the impact of drought, and consequently, to make decisions for coping with drought.

Description: Current model capabilities for simulating black carbon and sulfate concentrations in the Arctic atmosphere: a multi-model evaluation using a comprehensive measurement data set Atmospheric Chemistry and Physics, 15, 9413-9433, 2015 Author(s): S. Eckhardt, B. Quennehen, D. J. L. Olivié, T. K. Berntsen, R. Cherian, J. H. Christensen, W. Collins, S. Crepinsek, N. Daskalakis, M. Flanner, A. Herber, C. Heyes, Ø. Hodnebrog, L. Huang, M. Kanakidou, Z. Klimont, J. Langner, K. S. Law, M. T. Lund, R. Mahmood, A. Massling, S. Myriokefalitakis, I. E. Nielsen, J. K. Nøjgaard, J. Quaas, P. K. Quinn, J.-C. Raut, S. T. Rumbold, M. Schulz, S. Sharma, R. B. Skeie, H. Skov, T. Uttal, K. von Salzen, and A. Stohl The concentrations of sulfate, black carbon (BC) and other aerosols in the Arctic are characterized by high values in late winter and spring (so-called Arctic Haze) and low values in summer. Models have long been struggling to capture this seasonality and especially the high concentrations associated with Arctic Haze. In this study, we evaluate sulfate and BC concentrations from eleven different models driven with the same emission inventory against a comprehensive pan-Arctic measurement data set over a time period of 2 years (2008–2009). The set of models consisted of one Lagrangian particle dispersion model, four chemistry transport models (CTMs), one atmospheric chemistry-weather forecast model and five chemistry climate models (CCMs), of which two were nudged to meteorological analyses and three were running freely. The measurement data set consisted of surface measurements of equivalent BC (eBC) from five stations (Alert, Barrow, Pallas, Tiksi and Zeppelin), elemental carbon (EC) from Station Nord and Alert and aircraft measurements of refractory BC (rBC) from six different campaigns. We find that the models generally captured the measured eBC or rBC and sulfate concentrations quite well, compared to previous comparisons. However, the aerosol seasonality at the surface is still too weak in most models. Concentrations of eBC and sulfate averaged over three surface sites are underestimated in winter/spring in all but one model (model means for January–March underestimated by 59 and 37 % for BC and sulfate, respectively), whereas concentrations in summer are overestimated in the model mean (by 88 and 44 % for July–September), but with overestimates as well as underestimates present in individual models. The most pronounced eBC underestimates, not included in the above multi-site average, are found for the station Tiksi in Siberia where the measured annual mean eBC concentration is 3 times higher than the average annual mean for all other stations. This suggests an underestimate of BC sources in Russia in the emission inventory used. Based on the campaign data, biomass burning was identified as another cause of the modeling problems. For sulfate, very large differences were found in the model ensemble, with an apparent anti-correlation between modeled surface concentrations and total atmospheric columns. There is a strong correlation between observed sulfate and eBC concentrations with consistent sulfate/eBC slopes found for all Arctic stations, indicating that the sources contributing to sulfate and BC are similar throughout the Arctic and that the aerosols are internally mixed and undergo similar removal. However, only three models reproduced this finding, whereas sulfate and BC are weakly correlated in the other models. Overall, no class of models (e.g., CTMs, CCMs) performed better than the others and differences are independent of model resolution.

Description: Investigation of post-depositional processing of nitrate in East Antarctic snow: isotopic constraints on photolytic loss, re-oxidation, and source inputs Atmospheric Chemistry and Physics, 15, 9435-9453, 2015 Author(s): G. Shi, A. M. Buffen, M. G. Hastings, C. Li, H. Ma, Y. Li, B. Sun, C. An, and S. Jiang Snowpits along a traverse from coastal East Antarctica to the summit of the ice sheet (Dome Argus) are used to investigate the post-depositional processing of nitrate (NO 3 − ) in snow. Seven snowpits from sites with accumulation rates between 24 and 172 kg m −2 a −1 were sampled to depths of 150 to 300 cm. At sites from the continental interior (low accumulation, 〈 55 kg m −2 a −1 ), nitrate mass fraction is generally 〉 200 ng g −1 in surface snow and decreases quickly with depth to 〈 50 ng g −1 . Considerably increasing values of δ 15 N of nitrate are also observed (16–461 ‰ vs. air N 2 ), particularly in the top 20 cm, which is consistent with predicted fractionation constants for the photolysis of nitrate. The δ 18 O of nitrate (17–84 ‰ vs. VSMOW (Vienna Standard Mean Ocean Water)), on the other hand, decreases with increasing δ 15 N, suggestive of secondary formation of nitrate in situ (following photolysis) with a low δ 18 O source. Previous studies have suggested that δ 15 N and δ 18 O of nitrate at deeper snow depths should be predictable based upon an exponential change derived near the surface. At deeper depths sampled in this study, however, the relationship between nitrate mass fraction and δ 18 O changes, with increasing δ 18 O of nitrate observed between 100 and 200 cm. Predicting the impact of post-depositional loss, and therefore changes in the isotopes with depth, is highly sensitive to the depth interval over which an exponential change is assumed. In the snowpits collected closer to the coast (accumulation 〉 91 kg m −2 a −1 ), there are no obvious trends detected with depth and instead seasonality in nitrate mass fraction and isotopic composition is found. In comparison to the interior sites, the coastal pits are lower in δ 15 N (−15–71 ‰ vs. air N 2 ) and higher in δ 18 O of nitrate (53–111 ‰ vs. VSMOW). The relationships found amongst mass fraction, δ 15 N, δ 18 O and Δ 17 O (Δ 17 O = δ 17 O–0.52 × δ 18 O) of nitrate cannot be explained by local post-depositional processes alone, and are instead interpreted in the context of a primary atmospheric signal. Consistent with other Antarctic observational and modeling studies, the isotopic results are suggestive of an important influence of stratospheric ozone chemistry on nitrate formation during the cold season and a mix of tropospheric sources and chemistry during the warm season. Overall, the findings in this study speak to the sensitivity of nitrate isotopic composition to post-depositional processing and highlight the strength of combined use of the nitrogen and oxygen isotopes for a mechanistic understanding of this processing.

Description: NO x emission estimates during the 2014 Youth Olympic Games in Nanjing Atmospheric Chemistry and Physics, 15, 9399-9412, 2015 Author(s): J. Ding, R. J. van der A, B. Mijling, P. F. Levelt, and N. Hao The Nanjing Government applied temporary environmental regulations to guarantee good air quality during the Youth Olympic Games (YOG) in 2014. We study the effect of those regulations by applying the emission estimate algorithm DECSO (Daily Emission estimates Constrained by Satellite Observations) to measurements of the Ozone Monitoring Instrument (OMI). We improved DECSO by updating the chemical transport model CHIMERE from v2006 to v2013 and by adding an Observation minus Forecast (OmF) criterion to filter outlying satellite retrievals due to high aerosol concentrations. The comparison of model results with both ground and satellite observations indicates that CHIMERE v2013 is better performing than CHIMERE v2006. After filtering the satellite observations with high aerosol loads that were leading to large OmF values, unrealistic jumps in the emission estimates are removed. Despite the cloudy conditions during the YOG we could still see a decrease of tropospheric NO 2 column concentrations of about 32 % in the OMI observations when compared to the average NO 2 columns from 2005 to 2012. The results of the improved DECSO algorithm for NO x emissions show a reduction of at least 25 % during the YOG period and afterwards. This indicates that air quality regulations taken by the local government have an effect in reducing NO x emissions. The algorithm is also able to detect an emission reduction of 10 % during the Chinese Spring Festival. This study demonstrates the capacity of the DECSO algorithm to capture the change of NO x emissions on a monthly scale. We also show that the observed NO 2 columns and the derived emissions show different patterns that provide complimentary information. For example, the Nanjing smog episode in December 2013 led to a strong increase in NO 2 concentrations without an increase in NO x emissions. Furthermore, DECSO gives us important information on the non-trivial seasonal relation between NO x emissions and NO 2 concentrations on a local scale.

Description: Sensitivity of remotely-sensed trace gas concentrations to polarisation Atmospheric Measurement Techniques Discussions, 8, 8779-8816, 2015 Author(s): D. M. O'Brien, I. N. Polonsky, and J. B. Kumer Current and proposed space missions estimate column-averaged concentrations of trace gases (CO 2 , CH 4 and CO) from high resolution spectra of reflected sunlight in absorption bands of the gases. The radiance leaving the top of the atmosphere is partially polarised by both reflection at the surface and scattering within the atmosphere. Generally the polarisation state is unknown, and could degrade the accuracy of the concentration measurements. The sensitivity to polarisation is modelled for the proposed geoCARB instrument, which will include neither polarisers nor polarisation scramblers to select particular polarisation states from the incident radiation. The radiometric and polarimetric calibrations proposed for geoCARB are outlined, and a model is developed for the polarisation properties of the geoCARB spectrographs. This model depends principally upon the efficiencies of the gratings to polarisations parallel and perpendicular to the rulings of the gratings. Next an ensemble of polarised spectra is simulated for geoCARB observing targets in India, China and Australia from geostationary orbit at longitude 110° E. The spectra are analysed to recover the trace gas concentrations in two modes, the first denied access to the polarimetric calibration and the second with access. The retrieved concentrations using the calibration data are almost identical to those that would be obtained with polarisation scramblers, while the retrievals without calibration data contain outliers that do not meet the accuracies demanded by the mission.

Description: Observations of atmospheric mercury in China: a critical review Atmospheric Chemistry and Physics, 15, 9455-9476, 2015 Author(s): X. W. Fu, H. Zhang, B. Yu, X. Wang, C.-J. Lin, and X. B. Feng China presently contributes the largest amount of anthropogenic mercury (Hg) emission into the atmosphere in the world. Over the past decade, numerous studies have been conducted to characterize the concentration and forms of atmospheric Hg in China, which provide insights into the spatial and temporal distributions of atmospheric Hg through ground-based measurements at widely diverse geographical locations and during cruise and flight campaigns. In this paper, we present a comprehensive review of the state of understanding in atmospheric Hg in China. Gaseous elemental mercury (GEM) and particulate-bound mercury (PBM) measured at the remote sites in China are substantially elevated compared to the background values in the Northern Hemisphere. In Chinese urban areas, the highly elevated GEM, PBM and gaseous oxidized mercury (GOM) were mainly derived from local anthropogenic Hg emissions, whereas regional anthropogenic emissions and long-range transport from domestic source regions are the primary causes of the elevated GEM and PBM concentrations at remote sites. Using 7–9 years of continuous observations at a remote site and an urban site, a slight increase in atmospheric GEM (2.4–2.5 % yr −1 ) was identified (paired samples test: p 〈 0.01), which is in agreement with the increasing domestic anthropogenic emissions. Anthropogenic GEM emission quantity in China estimated through the observed GEM / CO concentration ratios ranged from 632 to 1138 t annually over the past decade, 2–3 times larger than published values using emission activity data. Modeling results and filed measurements show dry deposition is the predominant process for removing Hg from the atmosphere, 2.5–9.0 times larger than wet deposition, due to the elevated atmospheric GEM and PBM concentrations that facilitate dry deposition to terrestrial landscapes. Further studies to reconcile the observed and simulated Hg concentrations, to understand the impact of domestic emission reduction on Hg concentration and deposition and to delineate the role of Hg emission and deposition of China in the global Hg biogeochemical cycle, are needed.

Description: Exploiting the sensitivity of two satellite cloud height retrievals to cloud vertical distribution Atmospheric Measurement Techniques, 8, 3419-3431, 2015 Author(s): C. K. Carbajal Henken, L. Doppler, R. Lindstrot, R. Preusker, and J. Fischer This work presents a study on the sensitivity of two satellite cloud height retrievals to cloud vertical distribution. The difference in sensitivity is exploited by relating the difference in the retrieved cloud heights to cloud vertical extent. The two cloud height retrievals, performed within the Freie Universität Berlin AATSR MERIS Cloud (FAME-C) algorithm, are based on independent measurements and different retrieval techniques. First, cloud-top temperature (CTT) is retrieved from Advanced Along Track Scanning Radiometer (AATSR) measurements in the thermal infrared. Second, cloud-top pressure (CTP) is retrieved from Medium Resolution Imaging Spectrometer (MERIS) measurements in the oxygen-A absorption band and a nearby window channel. Both CTT and CTP are converted to cloud-top height (CTH) using atmospheric profiles from a numerical weather prediction model. First, a sensitivity study using radiative transfer simulations in the near-infrared and thermal infrared was performed to demonstrate, in a quantitative manner, the larger impact of the assumed cloud vertical extinction profile, described in terms of shape and vertical extent, on MERIS than on AATSR top-of-atmosphere measurements. Consequently, cloud vertical extinction profiles will have a larger influence on the MERIS than on the AATSR cloud height retrievals for most cloud types. Second, the difference in retrieved CTH (ΔCTH) from AATSR and MERIS are related to cloud vertical extent (CVE), as observed by ground-based lidar and radar at three ARM sites. To increase the impact of the cloud vertical extinction profile on the MERIS-CTP retrievals, single-layer and geometrically thin clouds are assumed in the forward model. Similarly to previous findings, the MERIS-CTP retrievals appear to be close to pressure levels in the middle of the cloud. Assuming a linear relationship, the ΔCTH multiplied by 2.5 gives an estimate on the CVE for single-layer clouds. The relationship is stronger for single-layer clouds than for multi-layer clouds. Due to large variations of cloud vertical extinction profiles occurring in nature, a quantitative estimate of the cloud vertical extent is accompanied with large uncertainties. Yet, estimates of the CVE provide an additional parameter, next to CTH, that can be obtained from passive imager measurements and can be used to further describe cloud vertical distribution, thus contributing to the characterization of a cloudy scene. To further demonstrate the plausibility of the approach, an estimate of the CVE was applied to a case study. In light of the follow-up mission Sentinel-3 with AATSR and MERIS like instruments, Sea and Land Surface Temperature Radiometer (SLSTR) and (Ocean and Land Colour Instrument) OLCI, respectively, for which the FAME-C algorithm can be easily adapted, a more accurate estimate of the CVE can be expected. OLCI will have three channels in the oxygen-A absorption band, possibly providing enhanced information on cloud vertical distributions.

Description: The electrical self-potential method is a non-intrusive snow-hydrological sensor The Cryosphere Discussions, 9, 4437-4457, 2015 Author(s): S. S. Thompson, B. Kulessa, R. L. H. Essery, and M. P. Lüthi Our ability to measure, quantify and assimilate hydrological properties and processes of snow in operational models is disproportionally poor compared to the significance of seasonal snowmelt as a global water resource and major risk factor in flood and avalanche forecasting. Encouraged by recent theoretical, modelling and laboratory work, we show here that the diurnal evolution of aerially-distributed self-potential magnitudes closely track those of bulk meltwater fluxes in melting in-situ snowpacks at Rhone and Jungfraujoch glaciers, Switzerland. Numerical modelling infers temporally-evolving liquid water contents in the snowpacks on successive days in close agreement with snow-pit measurements. Muting previous concerns, the governing physical and chemical properties of snow and meltwater became temporally invariant for modelling purposes. Because measurement procedure is straightforward and readily automated for continuous monitoring over significant spatial scales, we conclude that the self-potential geophysical method is a highly-promising non-intrusive snow-hydrological sensor for measurement practice, modelling and operational snow forecasting.

Description: Association of the pre-monsoon thermal field over north India and the western Tibetan Plateau with summer monsoon rainfall over India Annales Geophysicae, 33, 1051-1058, 2015 Author(s): S. D. Bansod, S. Fadnavis, and S. P. Ghanekar In this paper, interannual variability of tropospheric air temperatures over the Asian summer monsoon region during the pre-monsoon months is examined in relation to Indian summer monsoon rainfall (ISMR; June to September total rainfall). For this purpose, monthly grid-point temperatures in the entire troposphere over the Asian summer monsoon region and ISMR data for the period 1949–2012 have been used. Spatial correlation patterns are investigated between the temperature field in the lower tropospheric levels during May over the Asian summer monsoon region and ISMR. The results indicate a strong and significant northwest–southeast dipole structure in the spatial correlations over the Indian region, with highly significant positive (negative) correlations over the regions of north India and the western Tibetan Plateau region – region R1 (north Bay of Bengal: region R2). The observed dipole is seen significantly up to a level of 850 hPa and eventually disappears at 700 hPa. Thermal indices evaluated at 850 hPa level, based on average air temperatures over the north India and western Tibetan Plateau region (TI 1 ) and the north Bay of Bengal region (TI 2 ) during May, show a strong, significant relationship with the ISMR. The results are found to be consistent and robust, especially in the case of TI 1 during the period of analysis. A physical mechanism for the relationship between these indices and ISMR is proposed. Finally the composite annual cycle of tropospheric air temperature over R1 during flood/drought years of ISMR is examined. The study brings out the importance of the TI 1 in the prediction of flood/drought conditions over the Indian subcontinent.

Description: A wing pod-based millimeter wavelength airborne cloud radar Geoscientific Instrumentation, Methods and Data Systems, 4, 161-176, 2015 Author(s): J. Vivekanandan, S. Ellis, P. Tsai, E. Loew, W.-C. Lee, J. Emmett, M. Dixon, C. Burghart, and S. Rauenbuehler This paper describes a novel, airborne pod-based millimeter (mm) wavelength radar. Its frequency of operation is 94 GHz (3 mm wavelength). The radar has been designed to fly on the NCAR Gulfstream V HIAPER aircraft; however, it could be deployed on other similarly equipped aircraft. The pod-based configuration occupies minimum cabin space and maximizes scan coverage. The radar system is capable of collecting observations in a staring mode between zenith and nadir or in a scanning mode. Standard pulse-pair estimates of moments and raw time series of backscattered signals are recorded. The radar system design and characteristics as well as techniques for calibrating reflectivity and correcting Doppler velocity for aircraft attitude and motion are described. The radar can alternatively be deployed in a ground-based configuration, housed in the 20 ft shipping container it shares with the High Spectral Resolution Lidar (HSRL). The radar was tested both on the ground and in flight. Preliminary measurements of Doppler and polarization measurements were collected and examples are presented.

Description: A rainfall design method for spatial flood risk assessment: considering multiple flood sources Hydrology and Earth System Sciences Discussions, 12, 8005-8033, 2015 Author(s): X. Jiang and H. Tatano Information about the spatial distribution of flood risk is important for integrated urban flood risk management. Focusing on urban areas, spatial flood risk assessment must reflect all risk information derived from multiple flood sources: rivers, drainage, coastal flooding etc. that may affect the area. However, conventional flood risk assessment deals with each flood source independently, which leads to an underestimation of flood risk in the floodplain. Even in floodplains that have no risk from coastal flooding, flooding from river channels and inundation caused by insufficient drainage capacity should be considered simultaneously. For integrated flood risk management, it is necessary to establish a methodology to estimate flood risk distribution across a floodplain. In this paper, a rainfall design method for spatial flood risk assessment, which considers the joint effects of multiple flood sources, is proposed. The concept of critical rainfall duration determined by the concentration time of flooding is introduced to connect response characteristics of different flood sources with rainfall. A copula method is then adopted to capture the correlation of rainfall amount with different critical rainfall durations. Rainfall events are designed taking advantage of the copula structure of correlation and marginal distribution of rainfall amounts within different critical rainfall durations. A case study in the Otsu River Basin, Osaka prefecture, Japan was conducted to demonstrate this methodology.

Description: Tilt error in cryospheric surface radiation measurements at high latitudes: a model study The Cryosphere Discussions, 9, 4355-4376, 2015 Author(s): W. S. Bogren, J. F. Burkhart, and A. Kylling We have evaluated the magnitude and makeup of error in cryospheric radiation observations due to small sensor misalignment in in-situ measurements of solar irradiance. This error is examined through simulation of diffuse and direct irradiance arriving at a detector with a cosine-response foreoptic. Emphasis is placed on assessing total error over the solar shortwave spectrum from 250 to 4500 nm, as well as supporting investigation over other relevant shortwave spectral ranges. The total measurement error introduced by sensor tilt is dominated by the direct component. For a typical high latitude albedo measurement with a solar zenith angle of 60°, a sensor tilted by 1, 3, and 5° can respectively introduce up to 2.6, 7.7, and 12.8 % error into the measured irradiance and similar errors in the derived albedo. Depending on the daily range of solar azimuth and zenith angles, significant measurement error can persist also in integrated daily irradiance and albedo.

Description: A better understanding of hydroxyl radical photochemical sources in cloud waters collected at the puy de Dôme station – experimental versus modelled formation rates Atmospheric Chemistry and Physics, 15, 9191-9202, 2015 Author(s): A. Bianco, M. Passananti, H. Perroux, G. Voyard, C. Mouchel-Vallon, N. Chaumerliac, G. Mailhot, L. Deguillaume, and M. Brigante The oxidative capacity of the cloud aqueous phase is investigated during three field campaigns from 2013 to 2014 at the top of the puy de Dôme station (PUY) in France. A total of 41 cloud samples are collected and the corresponding air masses are classified as highly marine, marine and continental. Hydroxyl radical (HO•) formation rates (R HO• f ) are determined using a photochemical setup (xenon lamp that can reproduce the solar spectrum) and a chemical probe coupled with spectroscopic analysis that can trap all of the generated radicals for each sample. Using this method, the obtained values correspond to the total formation of HO• without its chemical sinks. These formation rates are correlated with the concentrations of the naturally occurring sources of HO•, including hydrogen peroxide, nitrite, nitrate and iron. The total hydroxyl radical formation rates are measured as ranging from approximately 2 × 10 −11 to 4 × 10 −10 M s −1 , and the hydroxyl radical quantum yield formation (Φ HO• ) is estimated between 10 −4 and 10 −2 . Experimental values are compared with modelled formation rates calculated by the model of multiphase cloud chemistry (M2C2), considering only the chemical sources of the hydroxyl radicals. The comparison between the experimental and the modelled results suggests that the photoreactivity of the iron species as a source of HO• is overestimated by the model, and H 2 O 2 photolysis represents the most important source of this radical (between 70 and 99 %) for the cloud water sampled at the PUY station (primarily marine and continental).

Description: Dust–air pollution dynamics over the eastern Mediterranean Atmospheric Chemistry and Physics, 15, 9173-9189, 2015 Author(s): M. Abdelkader, S. Metzger, R. E. Mamouri, M. Astitha, L. Barrie, Z. Levin, and J. Lelieveld Interactions of desert dust and air pollution over the eastern Mediterranean (EM) have been studied, focusing on two distinct dust transport events on 22 and 28 September 2011. The atmospheric chemistry–climate model EMAC has been used at about 50 km grid spacing, applying an online dust emission scheme and calcium as a proxy for dust reactivity. EMAC includes a detailed tropospheric chemistry mechanism, aerosol microphysics and thermodynamics schemes to describe dust "aging". The model is evaluated using ground-based observations for aerosol concentrations and aerosol optical depth (AOD) as well as satellite observations. Simulation results and back trajectory analysis show that the development of synoptic disturbances over the EM can enhance dust transport from the Sahara and Arabian deserts in frontal systems that also carry air pollution to the EM. The frontal systems are associated with precipitation that controls the dust removal. Our results show the importance of chemical aging of dust, which increases particle size, dust deposition and scavenging efficiency during transport, overall reducing the lifetime relative to non-aged dust particles. The relatively long travel periods of Saharan dust result in more sustained aging compared to Arabian dust. Sensitivity simulations indicate 3 times more dust deposition of aged relative to pristine dust, which significantly decreases the dust lifetime and loading.

Description: Accuracy of retrieving temperature and humidity profiles by ground-based microwave radiometry in truly complex terrain Atmospheric Measurement Techniques, 8, 3355-3367, 2015 Author(s): G. Massaro, I. Stiperski, B. Pospichal, and M. W. Rotach Within the Innsbruck Box project, a ground-based microwave radiometer (RPG-HATPRO) was operated in the Inn Valley (Austria), in very complex terrain, between September 2012 and May 2013 to obtain temperature and humidity vertical profiles of the full troposphere with a specific focus on the valley boundary layer. In order to assess its performance in a deep alpine valley, the profiles obtained by the radiometer with different retrieval algorithms based on different climatologies are compared to local radiosonde data. A retrieval that is improved with respect to the one provided by the manufacturer, based on better resolved data, shows a significantly smaller root mean square error (RMSE), both for the temperature and humidity profiles. The improvement is particularly substantial at the heights close to the mountaintop level and in the upper troposphere. Lower-level inversions, common in an alpine valley, are resolved to a satisfactory degree. On the other hand, upper-level inversions (above 1200 m) still pose a significant challenge for retrieval. For this purpose, specialized retrieval algorithms were developed by classifying the radiosonde climatologies into specialized categories according to different criteria (seasons, daytime, nighttime) and using additional regressors (e.g., measurements from mountain stations). The training and testing on the radiosonde data for these specialized categories suggests that a classification of profiles that reproduces meaningful physical characteristics can yield improved targeted specialized retrievals. A novel and very promising method of improving the profile retrieval in a mountainous region is adding further information in the retrieval, such as the surface temperature at fixed levels along a topographic slope or from nearby mountaintops.

Description: An inkling of the relation between the monofractality of temperatures and pressure anomalies Nonlinear Processes in Geophysics Discussions, 2, 1339-1353, 2015 Author(s): A. Deliège and S. Nicolay We use the discrete "wavelet transform microscope" to study the monofractal nature of surface air temperature signals of weather stations spread across Europe. This method reveals that the information obtained in this way is richer than previous works studying long range correlations in meteorological stations: the approach presented here allows to bind the Hölder exponents with the standard deviation of surface pressure anomalies, while such a link does not appear with methods previously carried out.

Description: Explanation of the values of Hack's drainage basin, river length scaling exponent Nonlinear Processes in Geophysics Discussions, 2, 1355-1361, 2015 Author(s): A. G. Hunt Percolation theory can be used to find water flow paths of least resistance. The application of percolation theory to drainage networks allows identification of the range of exponent values that describe the tortuosity of rivers in real river networks, which is then used to generate the observed scaling between drainage basin area and channel length, a relationship known as Hack's law. Such a theoretical basis for Hack's law allows interpretation of the range of exponent values based on an assessment of the heterogeneity of the substrate.

Description: Spectral diagonal ensemble Kalman filters Nonlinear Processes in Geophysics, 22, 485-497, 2015 Author(s): I. Kasanický, J. Mandel, and M. Vejmelka A new type of ensemble Kalman filter is developed, which is based on replacing the sample covariance in the analysis step by its diagonal in a spectral basis. It is proved that this technique improves the approximation of the covariance when the covariance itself is diagonal in the spectral basis, as is the case, e.g., for a second-order stationary random field and the Fourier basis. The method is extended by wavelets to the case when the state variables are random fields which are not spatially homogeneous. Efficient implementations by the fast Fourier transform (FFT) and discrete wavelet transform (DWT) are presented for several types of observations, including high-dimensional data given on a part of the domain, such as radar and satellite images. Computational experiments confirm that the method performs well on the Lorenz 96 problem and the shallow water equations with very small ensembles and over multiple analysis cycles.

Description: Design and validation of MEDRYS, a Mediterranean Sea reanalysis over 1992–2013 Ocean Science Discussions, 12, 1815-1867, 2015 Author(s): M. Hamon, J. Beuvier, S. Somot, J. M. Lellouche, E. Greiner, G. Jordà, M. N. Bouin, T. Arsouze, K. Béranger, F. Sevault, C. Dubois, M. Drevillon, and Y. Drillet The French research community on the Mediterranean Sea modelling and the French operational ocean forecasting center Mercator Océan have gathered their skill and expertise in physical oceanography, ocean modelling, atmospheric forcings and data assimilation, to carry out a MEDiterranean sea ReanalYsiS (MEDRYS) at high resolution for the period 1992–2013. The ocean model used is NEMOMED12, a Mediterranean configuration of NEMO with a 1/12° (∼ 7 km) horizontal resolution and 75 vertical z levels with partial steps. At the surface, it is forced by a new atmospheric forcing dataset (ALDERA), coming from a dynamical downscaling of the ERA-Interim atmospheric reanalysis by the regional climate model ALADIN-Climate with a 12 km horizontal and 3 h temporal resolutions. This configuration is used to carry a 34 year free simulation over the period 1979–2013 (NM12-FREE) which is the initial state of the reanalysis in October 1992. The first version of MEDRYS uses the existing Mercator Océan data assimilation system SAM that is based on a reduced-order Kalman filter with a 3-D multivariate modal decomposition of the forecast error. Altimeter data, satellite SST and temperature and salinity vertical profiles are jointly assimilated. This paper describes the configuration we used to perform the MEDRYS simulation. We then first validate the skills of the data assimilation system. It is shown that the data assimilation restores a good averaged temperature and salinity in intermediate layers compared to the free simulation. No particular biases are identified in the bottom layers. However, the reanalysis show slight positive biases of 0.02 psu and 0.15 °C above 150 m depth. In the validation stage, it is also shown that the assimilation allows to better reproduce water, heat and salt transports through the Strait of Gibraltar. Finally, the ability of the reanalysis to represent the sea surface high frequency variability is pointed out.

Description: Hydroelastic analysis of ice shelves under long wave excitation Natural Hazards and Earth System Science, 15, 1851-1857, 2015 Author(s): T. K. Papathanasiou, A. E. Karperaki, E. E. Theotokoglou, and K. A. Belibassakis The transient hydroelastic response of an ice shelf under long wave excitation is analysed by means of the finite element method. The simple model, presented in this work, is used for the simulation of the generated kinematic and stress fields in an ice shelf, when the latter interacts with a tsunami wave. The ice shelf, being of large length compared to its thickness, is modelled as an elastic Euler-Bernoulli beam, constrained at the grounding line. The hydrodynamic field is represented by the linearised shallow water equations. The numerical solution is based on the development of a special hydroelastic finite element for the system of governing of equations. Motivated by the 2011 Sulzberger Ice Shelf (SIS) calving event and its correlation with the Honshu Tsunami, the SIS stable configuration is studied. The extreme values of the bending moment distribution in both space and time are examined. Finally, the location of these extrema is investigated for different values of ice shelf thickness and tsunami wave length.

Description: A method for merging nadir-sounding climate records, with an application to the global-mean stratospheric temperature data sets from SSU and AMSU Atmospheric Chemistry and Physics, 15, 9271-9284, 2015 Author(s): C. McLandress, T. G. Shepherd, A. I. Jonsson, T. von Clarmann, and B. Funke A method is proposed for merging different nadir-sounding climate data records using measurements from high-resolution limb sounders to provide a transfer function between the different nadir measurements. The two nadir-sounding records need not be overlapping so long as the limb-sounding record bridges between them. The method is applied to global-mean stratospheric temperatures from the NOAA Climate Data Records based on the Stratospheric Sounding Unit (SSU) and the Advanced Microwave Sounding Unit-A (AMSU), extending the SSU record forward in time to yield a continuous data set from 1979 to present, and providing a simple framework for extending the SSU record into the future using AMSU. SSU and AMSU are bridged using temperature measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), which is of high enough vertical resolution to accurately represent the weighting functions of both SSU and AMSU. For this application, a purely statistical approach is not viable since the different nadir channels are not sufficiently linearly independent, statistically speaking. The near-global-mean linear temperature trends for extended SSU for 1980–2012 are −0.63 ± 0.13, −0.71 ± 0.15 and −0.80 ± 0.17 K decade −1 (95 % confidence) for channels 1, 2 and 3, respectively. The extended SSU temperature changes are in good agreement with those from the Microwave Limb Sounder (MLS) on the Aura satellite, with both exhibiting a cooling trend of ~ 0.6 ± 0.3 K decade −1 in the upper stratosphere from 2004 to 2012. The extended SSU record is found to be in agreement with high-top coupled atmosphere–ocean models over the 1980–2012 period, including the continued cooling over the first decade of the 21st century.

Description: On the potential for regolith control of fluvial terrace formation in semi-arid escarpments Earth Surface Dynamics Discussions, 3, 715-738, 2015 Author(s): K. P. Norton, F. Schlunegger, and C. Litty Cut-fill terraces occur throughout the western Andes where they have been associated with pluvial episodes on the Altiplano. The mechanism relating increased rainfall to sedimentation is however not well understood. Here, we apply a hillslope sediment model and reported cosmogenic nuclide concentrations in terraces to examine terrace formation in semi-arid escarpment environments. We focus on the Rio Pisco system in western Peru in order to determine probable hillslope processes and sediment transport conditions during phases of terrace formation. Specifically, we model steady state and transient hillslope responses to increased precipitation rates. The measured terrace distribution and reconstructed sediment loads measured for the Rio Pisco agree with the transient model predictions, suggesting strong climatic control on the cut-fill sequences in western Peru primarily through large variations in sediment load. Our model suggests that the ultimate control for these terraces is the availability of sediment on the hillslopes with hillslope stripping supplying large sediment loads early in wet periods. At the Rio Pisco, this is manifest as an approximately 4 × increase in erosion rates during pluvial periods. We suggest that this mechanism may also control terrace occurrence in other semi-arid escarpment settings.

Description: Post-Chernobyl surveys of radiocaesium in soil, vegetation, wildlife and fungi in Great Britain Earth System Science Data, 7, 215-221, 2015 Author(s): J. S. Chaplow, N. A. Beresford, and C. L. Barnett The data set "Post Chernobyl surveys of radiocaesium in soil, vegetation, wildlife and fungi in Great Britain" was developed to enable data collected by the Natural Environment Research Council after the Chernobyl accident to be made publicly available. Data for samples collected between May 1986 (immediately after Chernobyl) to spring 1997 are presented. Additional data to radiocaesium concentrations are presented where available. The data have value in trying to assess the contribution of new sources of radiocaesium in the environment, providing baseline data for future planned releases and to aid the development and testing of models. The data are freely available for non-commercial use under Open Government Licence terms and conditions. doi:10.5285/d0a6a8bf-68f0-4935-8b43-4e597c3bf251 . Supporting information to assist with the reuse of this data is available from the Environmental Information Data Centre (EIDC) ( http://eidc.ceh.ac.uk/ ).

Description: Three-dimensional finite element model of the drilling process used for fixation of Salter–Harris type-3 fractures by using a K-wire Mechanical Sciences, 6, 147-154, 2015 Author(s): A. Gok, K. Gok, and M. B. Bilgin In this study, the drilling process was performed with Kirschner wire (K-wire) for stabilization after reduction of Salter–Harris (SH) type-3 epiphyseal fractures of distal femur. The study was investigated both experimentally and numerically. The numerical analyses were performed with finite element method (FEM), using DEFORM-3D software. Some conditions such as friction, material model and load and boundary must be identified exactly while using FEM. At the same time, an analytic model and software were developed, which calculate the process parameters such as drilling power and thrust power, heat transfer coefficients and friction coefficient between tool–chip interface in order to identify the temperature distributions occurring in the K-wire and bone model (Keklikoǧlu Plastik San.) material during the drilling process. Experimental results and analysis results have been found as consistent with each other. The main cutting force, thrust force, bone model temperature and K-wire temperature were measured as 80° N, 120° N, 69 °C and 61 °C for 400 rpm in experimental studies. The main cutting force, thrust force, bone model temperature and K-wire temperature were measured as 65° N, 87° N, 91 °C and 82 °C for 800 rpm in experimental studies. The main cutting force, thrust force, bone model temperature and K-wire temperature were measured as 85° N, 127° N, 72 °C and 67 °C for 400 rpm in analysis studies. The main cutting force, thrust force, bone model temperature and K-wire temperature were measured as 69° N, 98° N, 83 °C and 76 °C for 800 rpm in analysis studies. A good consistency was obtained between experimental results and finite element analysis (FEA) results. This proved the validity of the software and finite element model. Thus, this model can be used reliably in such drilling processes.

Description: Pre-earthquake magnetic pulses Natural Hazards and Earth System Science, 15, 1873-1880, 2015 Author(s): J. Scoville, J. Heraud, and F. Freund A semiconductor model of rocks is shown to describe unipolar magnetic pulses, a phenomenon that has been observed prior to earthquakes. These pulses are suspected to be generated deep in the Earth's crust, in and around the hypocentral volume, days or even weeks before earthquakes. Their extremely long wavelength allows them to pass through kilometers of rock. Interestingly, when the sources of these pulses are triangulated, the locations coincide with the epicenters of future earthquakes. We couple a drift-diffusion semiconductor model to a magnetic field in order to describe the electromagnetic effects associated with electrical currents flowing within rocks. The resulting system of equations is solved numerically and it is seen that a volume of rock may act as a diode that produces transient currents when it switches bias. These unidirectional currents are expected to produce transient unipolar magnetic pulses similar in form, amplitude, and duration to those observed before earthquakes, and this suggests that the pulses could be the result of geophysical semiconductor processes.

Description: Ash iron mobilization through physicochemical processing in volcanic eruption plumes: a numerical modeling approach Atmospheric Chemistry and Physics, 15, 9361-9379, 2015 Author(s): G. A. Hoshyaripour, M. Hort, and B. Langmann It has been shown that volcanic ash fertilizes the Fe-limited areas of the surface ocean through releasing soluble iron. As ash iron is mostly insoluble upon the eruption, it is hypothesized that heterogeneous in-plume and in-cloud processing of the ash promote the iron solubilization. Direct evidences concerning such processes are, however, lacking. In this study, a 1-D numerical model is developed to simulate the physicochemical interactions of the gas–ash–aerosol in volcanic eruption plumes focusing on the iron mobilization processes at temperatures between 600 and 0 °C. Results show that sulfuric acid and water vapor condense at ~ 150 and ~ 50 °C on the ash surface, respectively. This liquid phase then efficiently scavenges the surrounding gases (〉 95 % of HCl, 3–20 % of SO 2 and 12–62 % of HF) forming an extremely acidic coating at the ash surface. The low pH conditions of the aqueous film promote acid-mediated dissolution of the Fe-bearing phases present in the ash material. We estimate that 0.1–33 % of the total iron available at the ash surface is dissolved in the aqueous phase before the freezing point is reached. The efficiency of dissolution is controlled by the halogen content of the erupted gas as well as the mineralogy of the iron at ash surface: elevated halogen concentrations and presence of Fe 2+ -carrying phases lead to the highest dissolution efficiency. Findings of this study are in agreement with the data obtained through leaching experiments.

Description: Seasonal variation of ozone and black carbon observed at Paknajol, an urban site in the Kathmandu Valley, Nepal Atmospheric Chemistry and Physics Discussions, 15, 22527-22566, 2015 Author(s): D. Putero, P. Cristofanelli, A. Marinoni, B. Adhikary, R. Duchi, S. D. Shrestha, G. P. Verza, T. C. Landi, F. Calzolari, M. Busetto, G. Agrillo, F. Biancofiore, P. Di Carlo, A. K. Panday, M. Rupakheti, and P. Bonasoni The Kathmandu Valley in South Asia is considered as one of the global "hot spots" in terms of urban air pollution. It is facing severe air quality problems as a result of rapid urbanization and land use change, socioeconomic transformation and high population growth. In this paper, we present the first full year (February 2013–January 2014) analysis of simultaneous measurements of two short-lived climate forcers/pollutants (SLCF/P), i.e. ozone (O 3 ) and equivalent black carbon (hereinafter noted as BC) and aerosol number concentration at Paknajol, in the center of the Kathmandu metropolitan city. The diurnal behavior of equivalent black carbon (BC) and aerosol number concentration indicated that local pollution sources represent the major contributions to air pollution in this city. In addition to photochemistry, the planetary boundary layer (PBL) and wind play important roles in determining O 3 variability, as suggested by the analysis of seasonal diurnal cycle and correlation with meteorological parameters and aerosol properties. Especially during pre-monsoon, high values of O 3 were found during the afternoon/evening; this could be related to mixing and entrainment processes between upper residual layers and the PBL. The high O 3 concentrations, in particular during pre-monsoon, appeared well related to the impact of major open vegetation fires occurring at regional scale. On a synoptic-scale perspective, westerly and regional atmospheric circulations appeared to be especially conducive for the occurrence of the high BC and O 3 values. The very high values of SLCF/P, detected during the whole measurement period, indicated persisting adverse air quality conditions, dangerous for the health of over 3 million residents of the Kathmandu Valley, and the environment. Consequently, all of this information may be useful for implementing control measures to mitigate the occurrence of acute pollution levels in the Kathmandu Valley and surrounding area.

Description: Methods for automatized detection of rapid changes in lateral boundary condition fields for NWP limited area models Geoscientific Model Development, 8, 2627-2643, 2015 Author(s): M. Tudor Three-hourly temporal resolution of lateral boundary data for limited area models (LAMs) can be too infrequent to resolve rapidly moving storms. This problem is expected to be worse with increasing horizontal resolution. In order to detect intensive disturbances in surface pressure moving rapidly through the model domain, a filtered surface pressure field (MCUF) is computed operationally in the ARPEGE global model of Météo France. The field is distributed in the coupling files along with conventional meteorological fields used for lateral boundary conditions (LBCs) for the operational forecast using limited area model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) in the Meteorological and Hydrological Service of Croatia (DHMZ). Here an analysis is performed of the MCUF field for the LACE coupling domain for the period from 23 January 2006, when it became available, until 15 November 2014. The MCUF field is a good indicator of rapidly moving pressure disturbances (RMPDs). Its spatial and temporal distribution can be associated with the usual cyclone tracks and areas known to be supporting cyclogenesis. An alternative set of coupling files from the IFS operational run in the European Centre for Medium-Range Weather Forecasts (ECMWF) is also available operationally in DHMZ with 3-hourly temporal resolution, but the MCUF field is not available. Here, several methods are tested that detect RMPDs in surface pressure a posteriori from the IFS model fields provided in the coupling files. MCUF is computed by running ALADIN on the coupling files from IFS. The error function is computed using one-time-step integration of ALADIN on the coupling files without initialization, initialized with digital filter initialization (DFI) or scale-selective DFI (SSDFI). Finally, the amplitude of changes in the mean sea level pressure is computed from the fields in the coupling files. The results are compared to the MCUF field of ARPEGE and the results of same methods applied to the coupling files from ARPEGE. Most methods give a signal for the RMPDs, but DFI reduces the storms too much to be detected. The error functions without filtering and amplitude have more noise, but the signal of a RMPD is also stronger. The methods are tested for NWP LAM ALADIN, but could be applied to other LAMs and benefit the performance of climate LAMs.

Description: Technical Note: Could benzalkonium chloride be a suitable alternative to mercuric chloride for preservation of seawater samples? Ocean Science Discussions, 12, 1953-1969, 2015 Author(s): J. Gloël, C. Robinson, G. H. Tilstone, G. Tarran, and J. Kaiser Instrumental equipment unsuitable or unavailable for fieldwork as well as lack of ship space can necessitate the preservation of seawater samples prior to analysis in a shore-based laboratory. Mercuric chloride (HgCl 2 ) is routinely used for such preservation, but its handling and subsequent disposal incur significant risks and expense. Benzalkonium chloride (BAC) has been used previously for freshwater samples. Here, we assess BAC as a less hazardous alternative microbial inhibitor for marine samples prior to the measurement of oxygen-to-argon (O 2 /Ar) ratios, as used for the determination of plankton net community production. BAC at a concentration of 50 mg dm −3 inhibited microbial activity for at least three days in seawater with chlorophyll a (Chl a ) concentrations up to 1 mg m −3 , possibly longer when Chl a concentrations were lower. BAC concentrations of 100 and 200 mg dm −3 were no more effective than 50 mg dm −3 . With fewer risks to human health and the environment, and no requirement for expensive waste disposal, BAC could be a viable alternative to HgCl 2 for short-term preservation of seawater samples, but is not a replacement for HgCl 2 in the case of oxygen triple isotope analysis, which requires storage over weeks to months. In any event, further tests on a case-by-case basis should be undertaken if use of BAC was considered, since its inhibitory activity may depend on concentration and composition of the microbial community.

Description: Characterizing Leaf Area Index (LAI) and Vertical Foliage Profile (VFP) over the United States Biogeosciences Discussions, 12, 13675-13710, 2015 Author(s): H. Tang, S. Ganguly, G. Zhang, M. A. Hofton, R. F. Nelson, and R. Dubayah Leaf area index (LAI) and vertical foliage profile (VFP) are among the important canopy structural variables. Recent advances in lidar remote sensing technology have demonstrated the capability of accurately mapping LAI and VFP over large areas. The primary objective of this study was to derive and validate a LAI and VFP product over the contiguous United States using spaceborne waveform lidar data. This product was derived at the footprint level from the Geoscience Laser Altimeter System (GLAS) using a biophysical model. We validated GLAS derived LAI and VFP across major forest biomes using airborne waveform lidar. The comparison results showed that GLAS retrievals of total LAI were generally accurate with little bias ( r 2 = 0.67, bias = −0.13, RMSE = 0.75). The derivations of GLAS retrievals of VFP within layers was not as accurate overall ( r 2 = 0.36, bias = −0.04, RMSE = 0.26), and these varied as a function of height, increasing from understory to overstory −0 to 5 m layer: r 2 = 0.04, bias = 0.09, RMSE = 0.31; 10 to 15 m layer: r 2 = 0.53, bias = −0.08, RMSE = 0.22; and 15 to 20 m layer: r 2 = 0.66, bias =−0.05, RMSE = 0.20. Significant relationships were also found between GLAS LAI products and different environmental factors, in particular elevation and annual precipitation. In summary, our results provide a unique insight into vertical canopy structure distribution across North American ecosystems. This data set is a first step towards a baseline of canopy structure needed for evaluating climate and land use induced forest changes at continental scale in the future and should help deepen our understanding of the role of vertical canopy structure on terrestrial ecosystem processes across varying scales.

Description: Comparison of ozone retrievals from the Pandora spectrometer system and Dobson spectrophotometer in Boulder, Colorado Atmospheric Measurement Techniques, 8, 3407-3418, 2015 Author(s): J. Herman, R. Evans, A. Cede, N. Abuhassan, I. Petropavlovskikh, and G. McConville A comparison of retrieved total column ozone (TCO) amounts between the Pandora #34 spectrometer system and the Dobson #061 spectrophotometer from direct-sun observations was performed on the roof of the Boulder, Colorado, NOAA building. This paper, part of an ongoing study, covers a 1-year period starting on 17 December 2013. Both the standard Dobson and Pandora TCO retrievals required a correction, TCOcorr = TCO (1 + C(T) ), using a monthly varying effective ozone temperature, T E , derived from a temperature and ozone profile climatology. The correction is used to remove a seasonal difference caused by using a fixed temperature in each retrieval algorithm. The respective corrections C ( T E ) are C Pandora = 0.00333( T E -225) and C Dobson = -0.0013( T E -226.7) per degree K. After the applied corrections removed most of the seasonal retrieval dependence on ozone temperature, TCO agreement between the instruments was within 1 % for clear-sky conditions. For clear-sky observations, both co-located instruments tracked the day-to-day variation in total column ozone amounts with a correlation of r 2 = 0.97 and an average offset of 1.1 ± 5.8 DU. In addition, the Pandora TCO data showed 0.3 % annual average agreement with satellite overpass data from AURA/OMI (Ozone Monitoring Instrument) and 1 % annual average offset with Suomi-NPP/OMPS (Suomi National Polar-orbiting Partnership, the nadir viewing portion of the Ozone Mapper Profiler Suite).

Description: Halogen-based reconstruction of Russian Arctic sea ice area from the Akademii Nauk ice core (Severnaya Zemlya) The Cryosphere Discussions, 9, 4407-4436, 2015 Author(s): A. Spolaor, T. Opel, J. R. McConnell, O. J. Maselli, G. Spreen, C. Varin, T. Kirchgeorg, D. Fritzsche, and P. Vallelonga The role of sea ice in the Earth climate system is still under debate, although it is known to influence albedo, ocean circulation, and atmosphere-ocean heat and gas exchange. Here we present a reconstruction of AD 1950 to 1998 sea ice in the Laptev Sea based on the Akademii Nauk ice core (Severnaya Zemlya, Russian Arctic). The halogens bromine (Br) and iodine (I) are strongly influenced by sea ice processes. Bromine reacts with the sea ice surface in auto-catalyzing "Bromine explosion" events causing an enrichment of the Br / Na ratio and the bromine excess (Br exc ) in snow compared to that in seawater. Iodine is emitted from algal communities growing under sea ice. The results suggest a connection between Br exc and spring sea ice area, as well as a connection between iodine concentration and summer sea ice area. These two halogens are therefore good candidates for extended reconstructions of past sea ice changes in the Arctic.

Description: Effects of vegetation restoration on the aggregate stability and distribution of aggregate-associated organic carbon in a typical karst gorge region Solid Earth Discussions, 7, 2213-2242, 2015 Author(s): F. K. Tang, M. Cui, Q. Lu, Y. G. Liu, H. Y. Guo, and J. X. Zhou Changes in soil utilization significantly affect aggregate stability and aggregate-associated soil organic carbon (SOC). A field investigation and indoor analysis were conducted in order to study the soil aggregate stability and organic carbon distribution in the water-stable aggregates (WSA) of the bare land (BL), grassland (GL), shrubland (SL), and woodland (WL) in a typical karst gorge region. The results indicated that the BL, GL, SL, and WL were dominated by particles with sizes 〉 5 mm under dry sieving treatment, and that the soil aggregate contents of various sizes decreased as the particle size decreased. In addition, the BL, GL, SL, and WL were predominantly comprised of WSA 〈 0.25 mm under wet sieving treatment, and that the WSA contents initially increased, then decreased, and then increased again as the particle size decreased. Furthermore, at a soil depth of 0–60 cm, the mean weight diameter (MWD), geometrical mean diameter (GMD), and fractal dimensions ( D ) of the dry aggregates and water-stable aggregates in the different types of land were ranked, in descending order, as WL 〉 GL 〉 SL 〉 BL. The contents of WSA 〉 0.25 mm, MWD and GMD increased significantly, in that order, and the percentage of aggregate destruction (PAD) and fractal dimensions decreased significantly as the soil aggregate stability improved. The results of this study indicated that, as the SOC contents increased after vegetation restoration, the average SOC content of WL was 2.35, 1.37, and 1.26 times greater than that in the BL, GL, and SL, respectively. The total SOC and SOC associated in WSA of various sizes were the highest at a soil depth of 0–20 cm. In addition, the SOC contents of the WSA increased as the soil aggregate sizes decreased. The SOC contents of the WSA 〈 0.25 mm were highest except in the bare land, and the SOC contents of the aggregates 〈 0.25 mm, which ranged from 18.85 to 41.08 %, comprised the majority of the total aggregate SOC contents. The woodland and grassland facilitated WSA stability and SOC protection, thus, promoting the natural restoration of vegetation by reducing artificial disturbances could effectively restore the ecology of and prevent soil erosion in karst regions.

Description: Application of the 15 N-Gas Flux method for measuring in situ N 2 and N 2 O fluxes due to denitrification in natural and semi-natural terrestrial ecosystems and comparison with the acetylene inhibition technique Biogeosciences Discussions, 12, 12653-12689, 2015 Author(s): F. Sgouridis, S. Ullah, and A. Stott Soil denitrification is considered the most un-constrained process in the global N cycle due to uncertain in situ N 2 flux measurements, particularly in natural and semi-natural terrestrial ecosystems. 15 N tracer approaches can provide in situ measurements of both N 2 and N 2 O simultaneously, but their use has been limited to fertilised agro-ecosystems due to the need for large 15 N additions in order to detect 15 N 2 production against the high atmospheric N 2 . For 15 N-N 2 analyses, we have used an "in house" laboratory designed and manufactured N 2 preparation instrument which can be interfaced to any commercial continuous flow isotope ratio mass spectrometer (CF-IRMS). The N 2 prep unit has gas purification steps, a copper based reduction furnace, and allows the analysis of small gas injection volumes (4 μL) for 15 N-N 2 analysis. For the analysis of N 2 O, an automated Tracegas Pre-concentrator (Isoprime Ltd) coupled to an IRMS was used to measure the 15 N-N 2 O (4 mL gas injection volume). Consequently, the coefficient of variation for the determination of isotope ratios for N 2 in air and in standard N 2 O (0.5 ppm) was better than 0.5 %. The 15 N Gas-Flux method was adapted for application in natural and semi-natural land use types (peatlands, forests and grasslands) by lowering the 15 N tracer application rate to 0.04–0.5 kg 15 N ha −1 . For our chamber design (volume / surface = 8:1) and a 20 h incubation period, the minimum detectable flux rates were 4 μg N m −2 h −1 and 0.2 ng N m −2 h −1 for the N 2 and N 2 O fluxes respectively. The N 2 flux ranged between 2.4 and 416.6 μg N m −2 h −1 , and the grassland soils showed on average 3 and 14 times higher denitrification rates than the woodland and organic soils respectively. The N 2 O flux was on average 20 to 200 times lower than the N 2 flux, while the denitrification product ratio (N 2 O/N 2 + N 2 O) was low, ranging between 0.03 and 13 %. Total denitrification rates measured by the acetylene inhibition technique under the same field conditions correlated ( r = 0.58) with the denitrification rates measured under the 15 N Gas-Flux method but were underestimated by a factor of 4 and this was attributed to the incomplete inhibition of N 2 O reduction to N 2 under relatively high soil moisture content. The results show that the 15 N Gas-Flux method can be used for quantifying N 2 and N 2 O production rates in natural terrestrial ecosystems, thus significantly improving our ability to constrain ecosystem N budgets.

Description: GO2OGS: a versatile workflow to integrate complex geological information with fault data into numerical simulation models Geoscientific Model Development Discussions, 8, 6309-6348, 2015 Author(s): T. Fischer, M. Walther, S. Sattler, D. Naumov, and O. Kolditz We offer a versatile workflow to convert geological models built with the software Paradigm™ GOCAD © into the open-source VTU format for the usage in numerical simulation models. Tackling relevant scientific questions or engineering tasks often involves multidisciplinary approaches. Conversion workflows are needed as a way of communication between the diverse tools of the various disciplines. Our approach offers an open-source, platform independent, robust, and comprehensible method that is potentially useful for a multitude of similar environmental studies. With two application examples in the Thuringian Syncline, we show how a heterogeneous geological GOCAD model including multiple layers and faults can be used for numerical groundwater flow modelling. The presented workflow offers the chance to incorporate increasingly detailed data, utilizing growing availability of computational power to simulate numerical models.

Description: The 9 September 2010 torrential rain and flash flood in the Dragone catchment, Atrani, Amalfi Coast (Southern Italy) Natural Hazards and Earth System Sciences Discussions, 3, 4715-4751, 2015 Author(s): C. Violante, G. Braca, E. Esposito, and G. Tranfaglia In this paper we use a multi-hazard approach to analyse the 9 September 2010 flash-flood occurred in the Dragone basin, a 9 km 2 catchment located along the Amalfi rocky coastal range, Southern Italy. In this area, alluvial-fan-flooding is the most frequent and destructive geologic hazards since Roman time. Sudden torrent of waters (flash flood) are caused by high-intensity and very localized cloudbursts of short duration inducing slope erosion and sediment delivery from slope-to-stream. The elevated bed load transport produces fast-moving hyperconcentrated flows with significant catastrophic implications for communities living at stream mouth. The 9 September 2010 rainstorm event lasted 1 h with an intensity rainfall peak nearly to 120 mm h −1 . High topographic relief of the Amalfi coastal range and positive anomalies of the coastal waters conditioned the character of the convective system. Based on geological data and post-event field evidence and surveys, as well as homemade-videos, and eyewitness accounts the consequent flash-flood mobilized some 25 000 m 3 of materials with a total (water and sediment) peak flow of 80 m 3 s −1 . The estimated peak discharge of only clear water was about 65 m 3 s −1 . This leads to a sediment bulking factor of 1.2 that corresponds to a flow with velocities similar to those of water during a flood.

Description: Concentrations and solubility of trace elements in fine particles at a mountain site, southern China: regional sources and cloud processing Atmospheric Chemistry and Physics, 15, 8987-9002, 2015 Author(s): T. Li, Y. Wang, W. J. Li, J. M. Chen, T. Wang, and W. X. Wang The concentrations and solubility of twelve trace elements in PM 2.5 at Mt. Lushan, southern China, were investigated during the summer of 2011 and the spring of 2012. The average PM 2.5 mass was 55.2 ± 20.1 μg m −3 during the observation period. Temporal variations of all trace elements including total and water-soluble fractions with several dust storm spikes in total fractions of Al and Fe were observed. The enrichment factor (EF) values were 1 order of magnitude higher for the water-soluble fractions versus the total fractions of trace elements. Four major emission sources, namely nonferrous metal mining and smelting (for Cr, As, Ba and parts of Zn), coal combustion (for Pb, Zn, Se, Cu and Mn), crustal materials (for Al and Fe) and municipal solid waste incineration (for Cd and Mo), were classified by principal component analysis (PCA). Trajectory cluster analysis and the potential source contribution function (PSCF) consistently identified the Yangtze River delta (YRD), the Pearl River delta (PRD), and the neighbouring provinces of Mt. Lushan as the major source regions and transport pathways for anthropogenic elements. Northern China was identified as a major source region for crustal elements. It should be noted that apart from the YRD, the area around Mt. Lushan has become the most significant contributor to the solubility of most trace elements. Element solubility can be partially determined by emission sources. However, enhanced solubility of trace elements corresponding to increased concentrations of sulfate after the occurrence of cloud events indicated significant effects of cloud processing on aerosol element dissolution. Metal particles mixed with sulfate in cloud droplet residues were further investigated through transmission electron microscopy (TEM) analysis. Irreversible alteration of particle morphology by cloud processing was confirmed to be highly responsible for the enhancement of trace element solubility. The findings from this study imply an important role of regional anthropogenic pollution and cloud processing in the evolution of aerosol trace element solubility during transport in the troposphere.

Description: Natural variability in the surface ocean carbonate ion concentration Biogeosciences Discussions, 12, 13123-13157, 2015 Author(s): N. S. Lovenduski, M. C. Long, and K. Lindsay We investigate variability in the surface ocean carbonate ion concentration ([CO 3 2− ]) on the basis of a long control simulation with a fully-coupled Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO 2 concentration for 1000 years, permitting investigation of natural [CO 3 2− ] variability on interannual to multi-decadal timescales. We find high interannual variability in surface [CO 3 2− ] in the tropical Pacific and at the boundaries between the subtropical and subpolar gyres in the Northern Hemisphere, and relatively low interannual variability in the centers of the subtropical gyres and in the Southern Ocean. Statistical analysis of modeled [CO 3 2− ] variance and autocorrelation suggests that significant anthropogenic trends in the saturation state of aragonite (Ω aragonite ) are already or nearly detectable at the sustained, open-ocean timeseries sites, whereas several decades of observations are required to detect anthropogenic trends in Ω aragonite in the tropical Pacific, North Pacific, and North Atlantic. The detection timescale for anthropogenic trends in pH is shorter than that for Ω aragonite , due to smaller noise-to-signal ratios and lower autocorrelation in pH. In the tropical Pacific, the leading mode of surface [CO 3 2− ] variability is primarily driven by variations in the vertical advection of dissolved inorganic carbon (DIC) in association with El Niño–Southern Oscillation. In the North Pacific, surface [CO 3 2− ] variability is caused by circulation-driven variations in surface DIC and strongly correlated with the Pacific Decadal Oscillation, with peak spectral power at 20–30 year periods. North Atlantic [CO 3 2− ] variability is also driven by variations in surface DIC, and exhibits weak correlations with both the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. As the scientific community seeks to detect the anthropogenic influence on ocean carbonate chemistry, these results will aid the interpretation of trends calculated from spatially- and temporally-sparse observations.

Description: Palaeoceanographic changes in Hornsund Fjord (Spitsbergen, Svalbard) over the last millennium: new insights from ancient DNA Climate of the Past Discussions, 11, 3665-3698, 2015 Author(s): J. Pawłowska, M. Zajączkowski, M. Łącka, F. Lejzerowicz, P. Esling, and J. Pawlowski This paper presents the reconstruction of climate-driven environmental changes of the last millennium from Hornsund Fjord (Svalbard) based on sedimentological and micropalaeontological records. Our palaeo-investigation was supported by the analysis of foraminiferal ancient DNA (aDNA), focusing on non-fossilised monothalamous species. The main climatic fluctuations over the last millennium were the Medieval Warm Period (MWP, 1000–1600 AD), the Little Ice Age (LIA, 1600–1900 AD), and the Modern Warming (MW, 1900 AD–present). Our study indicated that environmental conditions in Hornsund during the MWP and the early LIA (before ~ 1800 AD) were relatively stable, resulting from the distant position of glaciers. The beginning of the LIA (~ 1600 AD) was poorly evidenced by the micropalaeontological record, but well marked in the aDNA data, by an increased proportion of monothalamous foraminifera, especially Bathysiphon sp. The early LIA (~ 1600– ~ 1800 AD) was marked by the increase in abundance of sequences of Hippocrepinella hirudinea and Cedhagenia saltatus . In the late LIA (after ~ 1800 AD), conditions in the fjord became glacier-proximal, characterised by increased meltwater outflows, high sedimentation and a high calving rate. This coincided with an increase in the percentages of sequences of Micrometula sp. and Vellaria pellucidus . During the MW, major glaciers fronts retreated rapidly to the inner bays, limiting the iceberg discharge to the fjord centre and causing the shift in the foraminiferal community reflected in both fossil and aDNA records. Palaeoceanographic changes in the Hornsund Fjord over the last millennium were driven mainly by the inflow of shelf-originated water masses and glaciers' activity. However, the environmental changes were poorly evidenced in the micropalaeontological record, but well documented in our aDNA data. We considerably increased the number of potential proxy species by including monothalamous foraminifera in the palaeoecological studies.

Description: WRF4G: WRF experiment management made simple Geoscientific Model Development Discussions, 8, 6551-6582, 2015 Author(s): V. Fernández-Quiruelas, J. Fernández, A. S. Cofiño, C. Blanco, M. García-Díez, M. Magariño, L. Fita, and J. M. Gutiérrez This work presents a framework, WRF4G, to manage the experiment workflow of the Weather Research and Forecasting (WRF) modelling system. WRF4G provides a flexible design, execution and monitoring for a general class of scientific experiments. It has been designed with the aim of facilitating the management and reproducibility of complex experiments. Furthermore, the concepts behind the design of this framework can be straightforwardly extended to other models. We describe the user interface and the new concepts required to design parameter-sweep, hindcast and climate simulation experiments. A number of examples are provided, based on the design used for existing (published) WRF experiments. This software is open-source and publicly available http://www.meteo.unican.es/software/wrf4g ).

Description: PISCES-v2: an ocean biogeochemical model for carbon and ecosystem studies Geoscientific Model Development, 8, 2465-2513, 2015 Author(s): O. Aumont, C. Ethé, A. Tagliabue, L. Bopp, and M. Gehlen PISCES-v2 (Pelagic Interactions Scheme for Carbon and Ecosystem Studies volume 2) is a biogeochemical model which simulates the lower trophic levels of marine ecosystems (phytoplankton, microzooplankton and mesozooplankton) and the biogeochemical cycles of carbon and of the main nutrients (P, N, Fe, and Si). The model is intended to be used for both regional and global configurations at high or low spatial resolutions as well as for short-term (seasonal, interannual) and long-term (climate change, paleoceanography) analyses. There are 24 prognostic variables (tracers) including two phytoplankton compartments (diatoms and nanophytoplankton), two zooplankton size classes (microzooplankton and mesozooplankton) and a description of the carbonate chemistry. Formulations in PISCES-v2 are based on a mixed Monod–quota formalism. On the one hand, stoichiometry of C / N / P is fixed and growth rate of phytoplankton is limited by the external availability in N, P and Si. On the other hand, the iron and silicon quotas are variable and the growth rate of phytoplankton is limited by the internal availability in Fe. Various parameterizations can be activated in PISCES-v2, setting, for instance, the complexity of iron chemistry or the description of particulate organic materials. So far, PISCES-v2 has been coupled to the Nucleus for European Modelling of the Ocean (NEMO) and Regional Ocean Modeling System (ROMS) systems. A full description of PISCES-v2 and of its optional functionalities is provided here. The results of a quasi-steady-state simulation are presented and evaluated against diverse observational and satellite-derived data. Finally, some of the new functionalities of PISCES-v2 are tested in a series of sensitivity experiments.

Description: Implementation of the Community Earth System Model (CESM1, version 1.2.1) as a new basemodel into version 2.50 of the MESSy framework Geoscientific Model Development Discussions, 8, 6523-6550, 2015 Author(s): A. J. G. Baumgaertner, P. Jöckel, A. Kerkweg, R. Sander, and H. Tost The Community Earth System Model (CESM1), maintained by the United States National Centre for Atmospheric Research (NCAR) is connected with the Modular Earth Submodel System (MESSy). For the MESSy user community, this offers many new possibilities. The option to use the CESM1(CAM) atmospheric dynamical cores, especially the spectral element (SE) core, as an alternative to the ECHAM5 spectral transform dynamical core will provide scientific and computational advances for atmospheric chemistry and climate modelling with MESSy. The SE dynamical core does not require polar filters since the grid is quasi-uniform. By advecting the surface pressure rather then the logarithm of surface pressure the SE core locally conserves energy and mass. Furthermore, it has the possibility to scale to up to 10 5 compute cores, which is useful for current and future computing architectures. The well-established finite volume core from CESM1(CAM) is also made available. This offers the possibility to compare three different atmospheric dynamical cores within MESSy. Additionally, the CESM1 land, river, sea ice, glaciers and ocean component models can be used in CESM1/MESSy simulations, allowing to use MESSy as a comprehensive Earth System Model. For CESM1/MESSy setups, the MESSy process and diagnostic submodels for atmospheric physics and chemistry are used together with one of the CESM1(CAM) dynamical cores; the generic (infrastructure) submodels support the atmospheric model component. The other CESM1 component models as well as the coupling between them use the original CESM1 infrastructure code and libraries, although in future developments these can also be replaced by the MESSy framework. Here, we describe the structure and capabilities of CESM1/MESSy, document the code changes in CESM1 and MESSy, and introduce several simulations as example applications of the system. The Supplements provide further comparisons with the ECHAM5/MESSy atmospheric chemistry (EMAC) model and document the technical aspects of the connection in detail.

Description: DebrisInterMixing-2.3: a Finite Volume solver for three dimensional debris flow simulations based on a single calibration parameter – Part 2: Model validation Geoscientific Model Development Discussions, 8, 6379-6415, 2015 Author(s): A. von Boetticher, J. M. Turowski, B. W. McArdell, D. Rickenmann, M. Hürlimann, C. Scheidl, and J. W. Kirchner Here we present the validation of the fluid dynamic solver presented in part one of this work (von Boetticher et al., 2015), simulating laboratory-scale and large-scale debris-flow experiments. The material properties of the experiments, including water content, sand content, clay content and its mineral composition, and gravel content and its friction angle, were known. We show that given these measured properties, a single free model parameter is sufficient for calibration, and a range of experiments with different material compositions can be reproduced by the model without recalibration. The model validation focuses on different case studies illustrating the sensitivity of debris flows to water and clay content, channel curvature, channel roughness and the angle of repose of the gravel. We characterize the accuracy of the model using experimental observations of flow head positions, front velocities, run-out patterns and basal pressures.

Description: Modeling global water use for the 21st century: Water Futures and Solutions (WFaS) initiative and its approaches Geoscientific Model Development Discussions, 8, 6417-6521, 2015 Author(s): Y. Wada, M. Flörke, N. Hanasaki, S. Eisner, G. Fischer, S. Tramberend, Y. Satoh, M. T. H. van Vliet, P. Yillia, C. Ringler, and D. Wiberg To sustain growing food demand and increasing standard of living, global water use increased by nearly 6 times during the last 100 years and continues to grow. As water demands get closer and closer to the water availability in many regions, each drop of water becomes increasingly valuable and water must be managed more efficiently and intensively. However, soaring water use worsens water scarcity condition already prevalent in semi-arid and arid regions, increasing uncertainty for sustainable food production and economic development. Planning for future development and investments requires that we prepare water projections for the future. However, estimations are complicated because the future of world's waters will be influenced by a combination of environmental, social, economic, and political factors, and there is only limited knowledge and data available about freshwater resources and how they are being used. The Water Futures and Solutions initiative (WFaS) coordinates its work with other on-going scenario efforts for the sake of establishing a consistent set of new global water scenarios based on the Shared Socioeconomic Pathways (SSPs) and the Representative Concentration Pathways (RCPs). The WFaS "fast-track" assessment uses three global water models, namely H08, PCR-GLOBWB, and WaterGAP. This study assesses the state of the art for estimating and projecting water use regionally and globally in a consistent manner. It provides an overview of different approaches, the uncertainty, strengths and weaknesses of the various estimation methods, types of management and policy decisions for which the current estimation methods are useful. We also discuss additional information most needed to be able to improve water use estimates and be able to assess a greater range of management options across the water-energy-climate nexus.

Description: Technical Note: Testing an improved index for analysing storm nutrient hysteresis Hydrology and Earth System Sciences Discussions, 12, 7875-7892, 2015 Author(s): C. E. M. Lloyd, J. E. Freer, P. J. Johnes, and A. L. Collins Analysis of hydrochemical behaviour in extreme flow events can provide new insights into the process controls on nutrient transport in catchments. The examination of storm behaviours using hysteresis analysis has increased in recent years, partly due to the increased availability of high temporal resolution datasets for discharge and nutrient parameters. A number of these analyses involve the use of an index to describe the characteristics of a hysteresis loop in order to compare different storm behaviours both within and between catchments. This technical note reviews the methods for calculation of the hysteresis index (HI) and explores a new more effective methodology. Each method is systematically tested and the impact of the chosen calculation on the results is examined. Recommendations are made regarding the most effective method of calculating a HI which can be used for comparing data between storms and between different parameters and catchments.

Description: Mediterranean cyclone characteristics related to precipitation occurrence in Crete, Greece Natural Hazards and Earth System Science, 15, 1807-1819, 2015 Author(s): V. Iordanidou, A. G. Koutroulis, and I. K. Tsanis The characteristics of the cyclone tracks that caused precipitation events of variable intensity for the period 1979–2011 over the island of Crete are presented. The data set used for cyclone identification is the 0.5° × 0.5°, 30 years European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim mean sea-level pressure. Cyclone characteristics are calculated with the aid of the Melbourne University algorithm (MS scheme). Daily precipitation data from a dense gauging network over the island of Crete are also used for the classification of the precipitation events in terms of rain accumulation (intensity). Daily precipitation is classified in three categories and the associated cyclones are chosen according to their distance from Crete island. The seasonal and annual cycle of the physical characteristics of the cyclone tracks are investigated with respect to the cyclones' relative position to the island of Crete. It was found that cyclones affecting Crete most frequently approach from the western side of the island and the actual cyclone centers associated with precipitation events are usually located northwest and southeast of the Crete domain. Cyclone-induced rainfall increases in function to cyclones' depth, radius and propagation velocity increase as well as cyclones' pressure decrease. Spring cyclones that affect Crete with rainfall present lower pressures and higher cyclone propagation velocity in contrast to the ones associated with winter and autumn precipitation events. The examination of the relation between cyclone characteristics and precipitation occurrence provides valuable information related to forecasting potential and management of the water resources and the rainfall extremes.

Description: Interactions among drainage flows, gravity waves and turbulence: a BLLAST case study Atmospheric Chemistry and Physics, 15, 9031-9047, 2015 Author(s): C. Román-Cascón, C. Yagüe, L. Mahrt, M. Sastre, G.-J. Steeneveld, E. Pardyjak, A. van de Boer, and O. Hartogensis The interactions among several stable-boundary-layer (SBL) processes occurring just after the evening transition of 2 July 2011 have been analysed using data from instruments deployed over the area of Lannemezan (France) during the Boundary Layer Late Afternoon and Sunset Turbulence (BLLAST) field campaign. The near-calm situation of the afternoon was followed by the formation of local shallow drainage flows (SDFs) of less than 10 m depth at different locations. The SDF stage ended with the arrival of a stronger wind over a deeper layer more associated with the mountain-plain circulation, which caused mixing and destruction of the SDFs. Several gravity-wave-related oscillations were also observed on different time series. Wavelet analyses and wave parameters were calculated from high resolution and accurate surface pressure data of an array of microbarometers. These waves propagated relatively long distances within the SBL. The effects of these phenomena on turbulent parameters (friction velocity and kinematic heat flux) have been studied through multi-resolution flux decomposition methods performed on high frequency data from sonic anemometers deployed at different heights and locations. With this method, we were able to detect the different time-scales involved in each turbulent parameter and separate them from wave contributions, which becomes very important when choosing averaging-windows for surface flux computations using eddy covariance methods. The extensive instrumentation allowed us to highlight in detail the peculiarities of the surface turbulent parameters in the SBL, where several of the noted processes were interacting and producing important variations in turbulence with height and between sites along the sloping terrain.

Description: Spatial and temporal trends in summertime climate and water quality indicators in the coastal embayments of Buzzards Bay, Massachusetts Biogeosciences Discussions, 12, 13159-13192, 2015 Author(s): J. E. Rheuban, S. C. Williamson, J. E. Costa, D. M. Glover, R. W. Jakuba, D. C. McCorkle, C. Neill, T. Williams, and S. C. Doney Degradation of coastal ecosystems by eutrophication is largely defined by nitrogen loading from land via surface and groundwater flows. However, indicators of water quality are highly variable due to a myriad of other drivers, including temperature and precipitation. To evaluate these drivers, we examined spatial and temporal trends in a 22 year record of summer water quality data from 122 stations in 17 embayments within Buzzards Bay, MA (USA), collected through a citizen science monitoring program managed by Buzzards Bay Coalition. To identify spatial patterns across Buzzards Bay's embayments, we used a principle component and factor analysis and found that rotated factor loadings indicated little correlation between inorganic nutrients and organic matter and chlorophyll a (Chl a ) concentration. Factor scores showed that embayment geomorphology in addition to nutrient loading was a strong driver of water quality, where embayments with surface water inputs showed larger biological impacts than embayments dominated by groundwater influx. A linear regression analysis of annual summertime water quality indicators over time revealed that from 1992 to 2013, most embayments (15 of 17) exhibited an increase in temperature (mean rate of 0.082 ± 0.025 (SD) °C yr −1 ) and Chl a (mean rate of 0.0171 ± 0.0088 log 10 (Chl a ; mg m −3 ) yr −1 , equivalent to a 4.0 % increase per year). However, only 7 embayments exhibited an increase in total nitrogen (TN) concentration (mean rate 0.32 ± 0.47 (SD) μM yr −1 ). Average summertime log 10 (TN) and log 10 (Chl a ) were correlated with an indication that yield of Chl a per unit total nitrogen increased with time suggesting the estuarine response to TN may have changed because of other stressors such as warming, altered precipitation patterns, or changing light levels. These findings affirm that nitrogen loading and physical aspects of embayments are essential in explaining observed ecosystem response. However, climate-related stressors may also need to be considered by managers because increased temperature and precipitation may worsen water quality and partially offset benefits achieved by reducing nitrogen loading.

Description: Three-dimensional dust aerosol distribution and extinction climatology over northern Africa simulated with the ALADIN numerical prediction model from 2006 to 2010 Atmospheric Chemistry and Physics, 15, 9063-9082, 2015 Author(s): M. Mokhtari, P. Tulet, C. Fischer, Y. Bouteloup, F. Bouyssel, and O. Brachemi The seasonal cycle and optical properties of mineral dust aerosols in northern Africa were simulated for the period from 2006 to 2010 using the numerical atmospheric model ALADIN (Aire Limitée Adaptation dynamique Développement InterNational) coupled to the surface scheme SURFEX (SURFace EXternalisée). The particularity of the simulations is that the major physical processes responsible for dust emission and transport, as well as radiative effects, are taken into account on short timescales and at mesoscale resolution. The aim of these simulations is to quantify the dust emission and deposition, locate the major areas of dust emission and establish a climatology of aerosol optical properties in northern Africa. The mean monthly aerosol optical thickness (AOT) simulated by ALADIN is compared with the AOTs derived from the standard Dark Target (DT) and Deep Blue (DB) algorithms of the Aqua-MODIS (MODerate resolution Imaging Spectroradiometer) products over northern Africa and with a set of sun photometer measurements located at Banizoumbou, Cinzana, Soroa, Mbour and Cape Verde. The vertical distribution of dust aerosol represented by extinction profiles is also analysed using CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) observations. The annual dust emission simulated by ALADIN over northern Africa is 878 Tg year −1 . The Bodélé Depression appears to be the main area of dust emission in northern Africa, with an average estimate of about 21.6 Tg year −1 . The simulated AOTs are in good agreement with satellite and sun photometer observations. The positions of the maxima of the modelled AOTs over northern Africa match the observed positions, and the ALADIN simulations satisfactorily reproduce the various dust events over the 2006–2010 period. The AOT climatology proposed in this paper provides a solid database of optical properties and consolidates the existing climatology over this region derived from satellites, the AERONET network and regional climate models. Moreover, the 3-D distribution of the simulated AOTs also provides information about the vertical structure of the dust aerosol extinction.

Description: Retrieval and validation of carbon dioxide, methane and water vapor for the Canary Islands IR-laser occultation experiment Atmospheric Measurement Techniques, 8, 3315-3336, 2015 Author(s): V. Proschek, G. Kirchengast, S. Schweitzer, J. S. A. Brooke, P. F. Bernath, C. B. Thomas, J.-G. Wang, K. A. Tereszchuk, G. González Abad, R. J. Hargreaves, C. A. Beale, J. J. Harrison, P. A. Martin, V. L. Kasyutich, C. Gerbig, O. Kolle, and A. Loescher The first ground-based experiment to prove the concept of a novel space-based observation technique for microwave and infrared-laser occultation between low-Earth-orbit satellites was performed in the Canary Islands between La Palma and Tenerife. For two nights from 21 to 22 July 2011 the experiment delivered the infrared-laser differential transmission principle for the measurement of greenhouse gases (GHGs) in the free atmosphere. Such global and long-term stable measurements of GHGs, accompanied also by measurements of thermodynamic parameters and line-of-sight wind in a self-calibrating way, have become very important for climate change monitoring. The experiment delivered promising initial data for demonstrating the new observation concept by retrieving volume mixing ratios of GHGs along a ~144 km signal path at altitudes of ~2.4 km. Here, we present a detailed analysis of the measurements, following a recent publication that introduced the experiment's technical setup and first results for an example retrieval of CO 2 . We present the observational and validation data sets, the latter simultaneously measured at the transmitter and receiver sites; the measurement data handling; and the differential transmission retrieval procedure. We also determine the individual and combined uncertainties influencing the results and present the retrieval results for 12 CO 2 , 13 CO 2 , C 18 OO, H 2 O and CH 4 . The new method is found to have a reliable basis for monitoring of greenhouse gases such as CO 2 , CH 4 , and H 2 O in the free atmosphere.

Description: Soil storage influences climate–evapotranspiration interactions in three western United States catchments Hydrology and Earth System Sciences Discussions, 12, 7893-7931, 2015 Author(s): E. S. Garcia and C. L. Tague In the winter-wet, summer-dry forests of the western United States, total annual evapotranspiration (ET) varies with precipitation and temperature. Geologically mediated drainage and storage properties, however, may strongly influence these relationships between climate and ET. We use a physically based process model to evaluate how soil available water capacity (AWC) and rates of drainage influence model estimates of ET-climate relationships for three snow-dominated, mountainous catchments with differing precipitation regimes. Model estimates show that total annual precipitation is a primary control on inter-annual variation in ET across all catchments and that the timing of recharge is a second order control. Low soil AWC, however, increases the sensitivity of annual ET to these climate drivers by three to five times in our two study basins with drier summers. ET–climate relationships in our Colorado basin receiving summer precipitation are more stable across subsurface drainage and storage characteristics. Climate driver-ET relationships are most sensitive to soil AWC and soil drainage parameters related to lateral redistribution in the relatively dry Sierra site that receives little summer precipitation. Our results demonstrate that uncertainty in geophysically mediated storage and drainage properties can strongly influence model estimates of watershed scale ET responses to climate variation and climate change. This sensitivity to uncertainty in geophysical properties is particularly true for sites receiving little summer precipitation. A parallel interpretation of this parameter sensitivity is that spatial variation in soil properties are likely to lead to substantial within-watershed plot scale differences in forest water use and drought stress.

Description: Turbulence observations in the Gulf of Trieste under moderate wind forcing and different water column stratification Ocean Science Discussions, 12, 1729-1764, 2015 Author(s): F. M. Falcieri, L. Kantha, A. Benetazzo, A. Bergamasco, D. Bonaldo, F. Barbariol, V. Malačič, M. S. Sclavo, and S. Carniel During the oceanographic campaign CARPET2014, between 30 January and 4 February 2014, a total of 478 microstructure profiles (grouped into 145 ensembles) and 38 CTD casts were made in the Gulf of Trieste (Northern Adriatic Sea) under moderate wind forcing (average wind speed 10 m s -1 ) and heat fluxes (net negative heat flux in the range of 150 to 400 W m -2 ). Among the collected profiles, there were three sets of yoyo casts, each lasting for about 12 h for a total of 50 casts. Overall, these represent the first turbulence observations collected in the Gulf of Trieste. Microstructure profiles collected with a free-falling profiler must be taken in enables of repeated casts, with the objective of obtaining more statistically significant values for turbulence parameters. This approach is certainly feasible in shallow waters, but has a down side when the vertical density structure includes strong interfaces that can move up or down between subsequent casts, under the influence of tides and internal waves. In order to minimize the smearing effect of such interfacial displacements on mean quantities, we developed an algorithm to realign, according to the temperature profile, successive microstructure profiles to produce sharper and more meaningful mean profiles of measured turbulence parameters. During CARPET2014, the water column in the Gulf evolved from a well-mixed condition to a stratified one, due to Adriatic waters intruding at the bottom along the Gulf's south-eastern coast. These waters stratified the water column and changed its stability characteristics, which in turn prevented wind driven turbulence from penetrating to the bottom of the water column. In this study, we show that during a warm and relatively dry winter, such as in 2014, the Gulf of Trieste was not completely mixed because of the influence of bottom waters intruding from the open sea, even under moderate wind forcing. Inside the Gulf, two types of water intrusions from the Adriatic Sea were observed during the yoyo casts: one coming from its northern coast (i.e. warmer, saltier and more turbid) and one coming from the open sea in front of the Po Delta (i.e. cooler, fresher and less turbid). Those two intrusions behaved similarly but had a different impact on turbulence kinetic energy dissipation rate profiles. The former, with high turbidity, acted as a barrier to wind-driven turbulence, while the latter, with low sediment concentrations and a smaller density gradient when compared to the rest of the water column, was not able to suppress downward penetration of turbulence from the surface to the same degree.

Description: Monitoring Atlantic overturning circulation variability with GRACE-type ocean bottom pressure observations – a sensitivity study Ocean Science Discussions, 12, 1765-1791, 2015 Author(s): K. Bentel, F. W. Landerer, and C. Boening The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism for large-scale northward heat transport and thus plays an important role for global climate. Relatively warm water is transported northward in the upper layers of the North Atlantic Ocean, and after cooling at subpolar latitudes, sinks down and is transported back south in the deeper limb of the AMOC. The utility of in-situ ocean bottom pressure (OBP) observations to infer AMOC changes at single latitudes has been characterized in recent literature using output from ocean models. We extend the analysis and examine the utility of space-based observations of time-variable gravity and the inversion for ocean bottom pressure to monitor AMOC changes and variability between 20 and 60° N. Consistent with previous results, we find a strong correlation between the AMOC signal and OBP variations, mainly along the western slope of the Atlantic basin. We then use synthetic OBP data – smoothed and filtered to resemble the resolution of the GRACE gravity mission – and reconstruct geostrophic AMOC transport. Due to the coarse resolution of GRACE-like OBP fields, we find that leakage of signal across the step slopes of the ocean basin is a significant challenge at certain latitudes. However, overall, the inter-annual AMOC anomaly time series can be recovered from 20 years of monthly GRACE-like OBP fields with errors less than 1 Sverdrup.

Description: Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mine land SOIL Discussions, 2, 853-870, 2015 Author(s): S. Arnold and E. R. Williams Recolonisation of soil by macrofauna (especially ants and termites) in rehabilitated open-cut mine sites is inevitable. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration and seepage. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end-goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, soil macrofauna are typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions are required to quantify (i) macrofauna – soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

Description: Variability of water vapour in the Arctic stratosphere Atmospheric Chemistry and Physics Discussions, 15, 22013-22045, 2015 Author(s): L. Thölix, L. Backman, R. Kivi, and A. Karpechko This study evaluates the stratospheric water vapour distribution and variability in the Arctic. A FinROSE chemistry climate model simulation covering years 1990–2013 is compared to observations (satellite and frostpoint hygrometer soundings) and the sources of stratospheric water vapour are studied. According to observations and the simulations the water vapour concentration in the Arctic stratosphere started to increase after year 2006, but around 2011 the concentration started to decrease. Model calculations suggest that the increase in water vapour during 2006–2011 (at 56 hPa) is mostly explained by transport related processes, while the photochemically produced water vapour plays a relatively smaller role. The water vapour trend in the stratosphere may have contributed to increased ICE PSC occurrence. The increase of water vapour in the precense of the low winter temperatures in the Arctic stratosphere led to more frequent occurrence of ICE PSCs in the Arctic vortex. The polar vortex was unusually cold in early 2010 and allowed large scale formation of the polar stratospheric clouds. The cold pool in the stratosphere over the Northern polar latitudes was large and stable and a large scale persistent dehydration was observed. Polar stratospheric ice clouds and dehydration were observed at Sodankylä with accurate water vapour soundings in January and February 2010 during the LAPBIAT atmospheric sounding campaign. The observed changes in water vapour were reproduced by the model. Both the observed and simulated decrease of the water vapour in the dehydration layer was up to 1.5 ppm.

Description: Carbon dynamics in highly heterotrophic subarctic thaw ponds Biogeosciences Discussions, 12, 11707-11749, 2015 Author(s): T. Roiha, I. Laurion, and M. Rautio Global warming has accelerated the formation of permafrost thaw ponds in several subarctic and arctic regions. These ponds are net heterotrophic as evidenced by their greenhouse gas (GHG) supersaturation levels (CO 2 and CH 4 ), and generally receive large terrestrial carbon inputs from the thawing and eroding permafrost. We measured seasonal and vertical variations in the concentration and type of dissolved organic matter (DOM) in five subarctic thaw (thermokarst) ponds in northern Quebec, and explored how environmental gradients influenced heterotrophic and phototrophic biomass and productivity. Late winter DOM had low aromaticity indicating reduced inputs of terrestrial carbon, while the high concentration of dissolved organic carbon (DOC) suggests that some production of non-chromophoric dissolved compounds by the microbial food web took place under the ice cover. Summer DOM had a strong terrestrial signature, but was also characterized with significant inputs of algal-derived carbon, especially at the pond surface. During late winter, bacterial production was low (maximum of 0.8 mg C m −3 d −1 ) and was largely based on free-living bacterioplankton (58 %). Bacterial production in summer was high (up to 58 mg C m −3 d −1 ), dominated by particle-attached bacteria (67 %), and strongly correlated to the amount of terrestrial carbon. Primary production was restricted to summer surface waters due to strong light limitation deeper in the water column or in winter. The phototrophic biomass was equal to the heterotrophic biomass, but as the algae were mostly composed of mixotrophic species, most probably they used bacteria rather than solar energy in such shaded ponds. According to the δ 13 C analyses, non-algal carbon supported 51 % of winter and 37 % of summer biomass of the phantom midge larvae, Chaoborus sp., that are at the top of the trophic chain. Our results point to a strong heterotrophic energy pathway in these thaw pond ecosystems, where bacterioplankton dominates the production of new carbon in both summer and winter.

Description: On the use of satellite-derived CH 4 : CO 2 columns in a joint inversion of CH 4 and CO 2 fluxes Atmospheric Chemistry and Physics, 15, 8615-8629, 2015 Author(s): S. Pandey, S. Houweling, M. Krol, I. Aben, and T. Röckmann We present a method for assimilating total column CH 4 : CO 2 ratio measurements from satellites for inverse modeling of CH 4 and CO 2 fluxes using the variational approach. Unlike conventional approaches, in which retrieved CH 4 : CO 2 are multiplied by model-derived total column CO 2 and only the resulting CH 4 is assimilated, our method assimilates the ratio of CH 4 and CO 2 directly and is therefore called the ratio method. It is a dual tracer inversion, in which surface fluxes of CH 4 and CO 2 are optimized simultaneously. The optimization of CO 2 fluxes turns the hard constraint of prescribing model-derived CO 2 fields into a weak constraint on CO 2 , which allows us to account for uncertainties in CO 2 . The method has been successfully tested in a synthetic inversion setup. We show that the ratio method is able to reproduce assumed true CH 4 and CO 2 fluxes starting from a prior, which is derived by perturbing the true fluxes randomly. We compare the performance of the ratio method with that of the traditional proxy approach and the use of only surface measurements for estimating CH 4 fluxes. Our results confirm that the optimized CH 4 fluxes are sensitive to the treatment of CO 2 , and that hard constraints on CO 2 may significantly compromise results that are obtained for CH 4 . We find that the relative performance of ratio and proxy methods have a regional dependence. The ratio method performs better than the proxy method in regions where the CO 2 fluxes are most uncertain. However, both ratio and proxy methods perform better than the surface-measurement-only inversion, confirming the potential of spaceborne measurements for accurately determining fluxes of CH 4 and other greenhouse gases (GHGs).

Description: Relationships between photosynthesis and formaldehyde as a probe of isoprene emission Atmospheric Chemistry and Physics, 15, 8559-8576, 2015 Author(s): Y. Zheng, N. Unger, M. P. Barkley, and X. Yue Atmospheric oxidation of isoprene emission from land plants affects radiative forcing of global climate change. There is an urgent need to understand the factors that control isoprene emission variability on large spatiotemporal scales but such direct observations of isoprene emission do not exist. Two readily available global-scale long-term observation-based data sets hold information about surface isoprene activity: gross primary productivity (GPP) and tropospheric formaldehyde column variability (HCHOv). We analyze multi-year seasonal linear correlations between observed GPP and HCHOv. The observed GPP–HCHOv correlation patterns are used to evaluate a global Earth system model that embeds three alternative leaf-level isoprene emission algorithms. GPP and HCHOv are decoupled in the summertime in the southeast US ( r =−0.03). In the Amazon, GPP and HCHOv are weakly correlated in March-April-May (MAM), correlated in June-July-August (JJA) and weakly anticorrelated in September-October-November (SON). Isoprene emission algorithms that include soil moisture dependence demonstrate greater skill in reproducing the observed interannual seasonal GPP–HCHOv correlations in the southeast US and the Amazon. In isoprene emission models that include soil moisture dependence, isoprene emission is correlated with photosynthesis and anticorrelated with HCHOv. In an isoprene emission model without soil moisture dependence, isoprene emission is anticorrelated with photosynthesis and correlated with HCHOv. Long-term monitoring of isoprene emission, soil moisture and meteorology is required in water-limited ecosystems to improve understanding of the factors controlling isoprene emission and its representation in global Earth system models.

Description: Putting the clouds back in aerosol-cloud interactions Atmospheric Chemistry and Physics Discussions, 15, 20775-20810, 2015 Author(s): A. Gettelman Aerosol Cloud Interactions (ACI) are the consequence of perturbed aerosols affecting cloud drop and crystal number, with corresponding microphysical and radiative effects. ACI are sensitive to both cloud microphysical processes (the "C" in ACI) and aerosol emissions and processes (the "A" in ACI). This work highlights the importance of cloud microphysical processes, using idealized and global tests of a cloud microphysics scheme used for global climate prediction. Uncertainties in cloud microphysical processes cause uncertainties of up to −35 to +50 % in ACI, stronger than uncertainties due to natural aerosol emissions (−20 to +30 %). The different dimensions and sensitivities of ACI to microphysical processes are analyzed in detail, showing that precipitation processes are critical for understanding ACI and that uncertain cloud lifetime effects are 1/3 of simulated ACI. Buffering of different processes is important, as is the mixed phase and coupling of the microphysics to the condensation and turbulence schemes in the model.

Description: Evaluation of VIIRS, GOCI, and MODIS Collection 6 AOD retrievals against ground sunphotometer measurements over East Asia Atmospheric Chemistry and Physics Discussions, 15, 20709-20741, 2015 Author(s): Q. Xiao, H. Zhang, M. Choi, S. Li, S. Kondragunta, J. Kim, B. Holben, R. C. Levy, and Y. Liu Persistent high aerosol loadings together with extremely high population density have raised serious air quality and public health concerns in many urban centers in East Asia. However, ground based air quality monitoring is relatively limited in this area. Recently, satellite retrieved Aerosol Optical Depth (AOD) at high resolution has become a powerful tool to characterize aerosol patterns in space and time. Using ground AOD measurements from the Aerosol Robotic Network (AERONET) and the Distributed Regional Aerosol Gridded Observation Networks (DRAGON)-Asia Campaign, as well as from handheld sunphotometers, we evaluated emerging aerosol products from the Visible Infrared Imaging Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (S-NPP), the Geostationary Ocean Color Imager (GOCI) aboard the Communication, Ocean, and Meteorology Satellite (COMS), and Terra and Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) (Collection 6) in East Asia in 2012 and 2013. In the case study in Beijing, when compared with AOD measured by handheld sunphotometers, 51 % of VIIRS Environmental Data Record (EDR) AOD, 33 % of VIIRS Intermediate Product (IP) AOD, 31 % of GOCI AOD, 26 % of Terra MODIS C6 3 km AOD, and 16 % of Aqua MODIS C6 3 km AOD fell within the reference expected error (EE) envelop (±0.05 ± 0.15 AOD). Comparing against AERONET measurements over the Japan–South Korea region, 64 % of EDR, 37 % of IP, 62 % of GOCI, 39 % of Terra MODIS and 56 % of Aqua MODIS C6 3 km AOD fell within the EE. In general, satellite aerosol products performed better in tracking the day-to-day variability than tracking the spatial variability at high resolutions. The VIIRS EDR and GOCI products provided the most accurate AOD retrievals, while VIIRS IP and MODIS C6 3 km products had positive biases.

Description: Toward enhanced capability for detecting and predicting dust events in the Western United States: the Arizona Case Study Atmospheric Chemistry and Physics Discussions, 15, 20743-20774, 2015 Author(s): M. Huang, D. Tong, P. Lee, L. Pan, Y. Tang, I. Stajner, R. B. Pierce, J. McQueen, and J. Wang Dust aerosols affect human life, ecosystems, atmospheric chemistry and climate in various aspects. Studies have revealed intensified dust activity in the western US during the past decades despite the weaker dust activity in non-US regions. It is important to extend the historical dust records, to better understand their temporal changes, and use such information to improve the daily dust forecasting skill as well as the projection of future dust activity under the changing climate. This study develops dust records in Arizona in 2005–2013 using multiple observation datasets, including in-situ measurements at the surface Air Quality System (AQS) and Interagency Monitoring of Protected Visual Environments (IMPROVE) sites, and level 2 deep blue aerosol product by the Moderate Resolution Imaging Spectroradiometer. The diurnal and inter-annual variability of identified dust events are shown related to observed weather patterns (e.g., wind and soil moisture) and vegetation conditions, suggesting a potential for use of satellite soil moisture and vegetation index products to interpret and predict dust activity. Back-trajectories computed using NOAA's Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model indicate that the Sonoran and Chihuahuan deserts are important dust source regions during identified dust events in Phoenix, Arizona. Finally, we evaluate the performance of the US National Air Quality Forecasting Capability (NAQFC) 12 km CMAQ model during a recent strong dust event in the western US accompanied by stratospheric ozone intrusion. It is shown that the current modeling system well captures the temporal variability and the magnitude of aerosol concentrations during this event, and the usefulness and limitations of different observations in model evaluation are discussed. Directions of integrating observations to further improve dust emission modeling in CMAQ are also suggested.

Description: Effects of urban land expansion on the regional meteorology and air quality of eastern China Atmospheric Chemistry and Physics, 15, 8597-8614, 2015 Author(s): W. Tao, J. Liu, G. A. Ban-Weiss, D. A. Hauglustaine, L. Zhang, Q. Zhang, Y. Cheng, Y. Yu, and S. Tao Rapid urbanization throughout eastern China is imposing an irreversible effect on local climate and air quality. In this paper, we examine the response of a range of meteorological and air quality indicators to urbanization. Our study uses the Weather Research and Forecasting model coupled with chemistry (WRF/Chem) to simulate the climate and air quality impacts of four hypothetical urbanization scenarios with fixed surface pollutant emissions during the month of July from 2008 to 2012. An improved integrated process rate (IPR) analysis scheme is implemented in WRF/Chem to investigate the mechanisms behind the forcing–response relationship at the process level. For all years, as urban land area expands, concentrations of CO, elemental carbon (EC), and particulate matter with aerodynamic diameter less than 2.5 microns (PM 2.5 ) tend to decrease near the surface (below ~ 500 m), but increase at higher altitudes (1–3 km), resulting in a reduced vertical concentration gradient. On the other hand, the O 3 burden, averaged over all newly urbanized grid cells, consistently increases from the surface to a height of about 4 km. Sensitivity tests show that the responses of pollutant concentrations to the spatial extent of urbanization are nearly linear near the surface, but nonlinear at higher altitudes. Over eastern China, each 10 % increase in nearby urban land coverage on average leads to a decrease of approximately 2 % in surface concentrations for CO, EC, and PM 2.5 , while for O 3 an increase of about 1 % is simulated. At 800 hPa, pollutants' concentrations tend to increase even more rapidly with an increase in nearby urban land coverage. This indicates that as large tracts of new urban land emerge, the influence of urban expansion on meteorology and air pollution would be significantly amplified. IPR analysis reveals the contribution of individual atmospheric processes to pollutants' concentration changes. It indicates that, for primary pollutants, the enhanced sink (source) caused by turbulent mixing and vertical advection in the lower (upper) atmosphere could be a key factor in changes to simulated vertical profiles. The evolution of secondary pollutants is further influenced by the upward relocation of precursors that impact gas-phase chemistry for O 3 and aerosol processes for PM 2.5 . Our study indicates that dense urbanization has a moderate dilution effect on surface primary airborne contaminants, but may intensify severe haze and ozone pollution if local emissions are not well controlled.

Description: Probabilistic hurricane-induced storm surge hazard assessment in Guadeloupe, Lesser Antilles Natural Hazards and Earth System Science, 15, 1711-1720, 2015 Author(s): Y. Krien, B. Dudon, J. Roger, and N. Zahibo Current storm surge hazard maps in the French West Indies are essentially based on simple statistical methods using limited historical data and early low-resolution models which do not take the effect of waves into account. In this paper, we infer new 100-year and 1000-year surge levels in Guadeloupe from the numerical modelling of storm surges induced by a large set of synthetic events that are in statistical agreement with features of historical hurricanes in the North Atlantic Basin between 1980 and 2011. Computations are performed using the wave-current coupled model ADCIRC–SWAN with high grid resolutions (up to 40–60 m) in the coastal and wave dissipation areas. This model is validated against observations during past events such as hurricane HUGO (1989). Results are generally found to be in reasonable agreement with past studies in areas where surge is essentially wind-driven, but found to differ significantly in coastal regions where the transfer of momentum from waves to the water column constitutes a non-negligible part of the total surge. The methodology, which can be applied to other islands in the Lesser Antilles, allows storm surge level maps to be obtained that can be of major interest for coastal planners and decision makers in terms of risk management.

Description: Teaching disaster preparedness via a mobile device: a study of Auckland Civil Defence's Smartphone Application Natural Hazards and Earth System Sciences Discussions, 3, 4555-4583, 2015 Author(s): O. Kulemeka This content analysis study examined whether a disaster preparedness education smartphone application created by a New Zealand city matches what experts say are effective ways of teaching disaster preparedness and teaching via an app. The app was assessed to ascertain if it excelled as a platform for learning, communicated effectively, addressed factors that can hinder people from preparing, and provided information for special needs populations. Results show that the app addressed most factors that hinder preparedness, provided information for some special needs populations, excelled as a platform for learning, and communicated effectively. The app's weaknesses include the fact that it lacked targeted information for low-income residents. The findings provide insight on how organizations can effectively use apps to teach disaster preparedness. The author passed away before the publication of this discussion paper. Therefore, a final revised paper is not foreseen.

Description: Improvements in aggregate stability of recently deposited sediments supplemented with tea waste and farmyard manure Solid Earth Discussions, 7, 2037-2053, 2015 Author(s): B. Turgut and B. Köse Organic matter supplement is well-known to influence soil aggregate stability (AS), but the corresponding change in recently deposited fine sediment is not documented well. In this study, improvements in aggregate stability of recently deposited sediment supplemented with the farmyard manure (FYM) and tea waste (TW) during 18-week incubation under controlled conditions. The FYM and TW were applied to recently deposited sediment at different doses (0, 2.5, 5, 7.5, 10, 12.5, and 15 % on weight base). The AS was determined at different times after adding organic matter (2nd, 4th, 6th, 8th, 10th, 14th, and 18th weeks) using wet sieving methods. The results showed that aggregate stability of deposited sediment treated with TW was statistically significantly higher than these of samples treated with FYM. Aggregate stability increased with increasing doses of both FYM and TW. In the FYM applied samples, AS reached the highest value at the end of second week, and declined within the following incubation period. However, in the samples treated with TW, AS reached the highest value at the end of eighth week. The results of this study were clearly indicated that tea waste and farmyard manure applications noticeably increased aggregate stability of recently deposited sediment, therefore it is suggested that TW and FYM could be used for structural stabilization of sediments.

Description: Size distributions of polycyclic aromatic hydrocarbons in urban atmosphere: sorption mechanism and source contributions to respiratory deposition Atmospheric Chemistry and Physics Discussions, 15, 20811-20850, 2015 Author(s): Y. Lv, X. Li, T. T. Xu, T. T. Cheng, X. Yang, J. M. Chen, Y. Linuma, and H. Herrmann Current knowledge on atmospheric particle-phase polycyclic aromatic hydrocarbons (PAHs) size distribution remains incomplete. Information is missing on sorption mechanisms and the influence of the PAHs' sources on their transport in human respiratory system. Here we present the studies systematically investigating the modal distribution characteristics of the size-fractioned PAHs and calculating the source contribution to adverse health effects through inhalation. Aerosol samples with nine size fractions were collected from Shanghai urban air over one year period 2012–2013. A high correlation coefficient existed between measured and predicted values ( R 2 = 0.87), indicated that the data worked very well in current study. Most PAHs were observed on the small particles followed with seasonality differences. When normalized by PAHs across particle diameters, the size distribution of PAHs exhibited bimodal patterns, with a peak (0.4–2.1 μm) in fine mode and another peak (3.3–9.0 μm) in coarse mode, respectively. Along with the increasing ring number of PAHs, the intensity of the fine mode peak increased, while coarse mode peak decreased. Plotting of log(PAH/PM) against log( D p ) showed that all slope values were above −1 with the increase towards less-ring PAHs, suggesting that multiple mechanisms, i.e. adsorption and absorption controlled the PAHs on particles, but adsorption played a much stronger role for 5- and 6-ring than 3- and 4-ring PAHs. The mode distribution behavior of PAHs showed that fine particles were major carriers for the more-ring PAHs. Further calculations using inhaling PAHs data showed the total deposition fluxes in respiratory tract were 8.8 ± 2.0 ng h -1 . Specifically, fine particles contributed 10–40 % of PAHs deposition fluxes to the alveolar region, while coarse particles contributed 80–95 % of ones to the head region. Estimated lifetime cancer risk (LCR) for people exercised in haze days (1.5 × 10 -6 ) was bigger than the cancer risk guideline value (10 -6 ). The largest PAHs contribution for LCR mainly came from the accumulation particles. Based on source apportionment results generated by positive matrix factorization (PMF), it was found that the cancer risk caused in accumulated mode mainly resulted from biomass burning (24 %), coal combustion (25 %) and vehicular emission (27 %). The present results contribute to a mechanistic understanding of PAHs size distribution causing adverse health effects and will help develop some source control strategies or policies by relying on respiratory assessment data.

Description: Improvement of climate predictions and reduction of their uncertainties using learning algorithms Atmospheric Chemistry and Physics, 15, 8631-8641, 2015 Author(s): E. Strobach and G. Bel Simulated climate dynamics, initialized with observed conditions, is expected to be synchronized, for several years, with the actual dynamics. However, the predictions of climate models are not sufficiently accurate. Moreover, there is a large variance between simulations initialized at different times and between different models. One way to improve climate predictions and to reduce the associated uncertainties is to use an ensemble of climate model predictions, weighted according to their past performances. Here, we show that skillful predictions, for a decadal time scale, of the 2 m temperature can be achieved by applying a sequential learning algorithm to an ensemble of decadal climate model simulations. The predictions generated by the learning algorithm are shown to be better than those of each of the models in the ensemble, the better performing simple average and a reference climatology. In addition, the uncertainties associated with the predictions are shown to be reduced relative to those derived from an equally weighted ensemble of bias-corrected predictions. The results show that learning algorithms can help to better assess future climate dynamics.

Description: Phototrophic pigment diversity and picophytoplankton abundance in permafrost thaw lakes Biogeosciences Discussions, 12, 12121-12156, 2015 Author(s): A. Przytulska, J. Comte, S. Crevecoeur, C. Lovejoy, I. Laurion, and W. F. Vincent Permafrost thaw lakes (thermokarst lakes) are widely distributed across the northern landscape, and are known to be biogeochemically active sites that emit large amounts of carbon to the atmosphere as CH 4 and CO 2 . However, the abundance and composition of the photosynthetic communities that consume CO 2 have been little explored in this ecosystem type. In order to identify the major groups of phototrophic organisms and their controlling variables, we sampled 12 permafrost thaw lakes along a permafrost degradation gradient in northern Québec, Canada. Additional samples were taken from 5 rock-basin reference lakes in the region to determine if the thaw waters differed in limnological properties and phototrophs. Phytoplankton community structure was determined by high performance liquid chromatography analysis of their photoprotective and photosynthetic pigments, and autotrophic picoplankton concentrations were assessed by flow cytometry. One of the black colored lakes located in a andscape of rapidly degrading palsas (permafrost mounds) was selected for high-throughput 18S rRNA sequencing to help interpret the pigment and cytometry data. The results showed that the limnological properties of the thaw lakes differed significantly from the reference lakes, and were more highly stratified. However, both waterbody types contained similarly diverse phytoplankton groups, with dominance of the pigment assemblages by fucoxanthin-containing taxa, as well as chlorophytes, cryptophytes and cyanobacteria. Chlorophyll a concentrations (Chl a ) were correlated with total phosphorus (TP), and both were significantly higher in the thaw lakes (overall means of 3.3 μg Chl a L −1 and 34 μg TP L −1 ) relative to the reference lakes (2.0 μg Chl a L −1 and 8.2 μg TP L −1 ). Stepwise multiple regression of Chl a against the other algal pigments showed that it was largely a function of lutein, fucoxanthin and peridinin ( R 2 = 0.78). The bottom waters of two of the thaw lakes also contained high concentrations of bacteriochlorophyll d , showing the presence of green photosynthetic sulphur bacteria. The molecular analyses indicated a relatively minor contribution of diatoms, while chrysophytes, dinoflagellates and chlorophytes were well represented; the heterotrophic eukaryote fraction was dominated by numerous ciliate taxa, and also included Heliozoa, Rhizaria, chytrids and flagellates. Autotrophic picoplankton occurred in cell concentrations up to 8.8 × 10 5 mL −1 (picocyanobacteria) and 4.6 × 10 5 mL −1 (picoeukaryotes). Both groups of picophytoplankton were positively correlated with total phytoplankton abundance, as measured by Chl a ; picocyanobacteria were inversely correlated with dissolved organic carbon, while picoeukaryotes were correlated with conductivity. Despite their net heterotrophic character, subarctic thaw lakes are rich habitats for diverse phototrophic communities.

Description: Groundwater seepage landscapes from distant and local sources in experiments and on Mars Earth Surface Dynamics, 3, 389-408, 2015 Author(s): W. A. Marra, S. J. McLelland, D. R. Parsons, B. J. Murphy, E. Hauber, and M. G. Kleinhans Valleys with theater-shaped heads can form due to the seepage of groundwater and as a result of knickpoint (waterfall) erosion generated by overland flow. This ambiguity in the mechanism of formation hampers the interpretation of such valleys on Mars, particularly since there is limited knowledge of material properties. Moreover, the hydrological implications of a groundwater or surface water origin are important for our understanding of the evolution of surface features on Mars, and a quantification of valley morphologies at the landscape scale may provide diagnostic insights on the formative hydrological conditions. However, flow patterns and the resulting landscapes produced by different sources of groundwater are poorly understood. We aim to improve the understanding of the formation of entire valley landscapes through seepage processes from different groundwater sources that will provide a framework of landscape metrics for the interpretation of such systems. We study groundwater seepage from a distant source of groundwater and from infiltration of local precipitation in a series of sandbox experiments and combine our results with previous experiments and observations of the Martian surface. Key results are that groundwater flow piracy acts on valleys fed by a distant groundwater source and results in a sparsely dissected landscape of many small and a few large valleys. In contrast, valleys fed by a local groundwater source, i.e., nearby infiltration, result in a densely dissected landscape. In addition, valleys fed by a distant groundwater source grow towards that source, while valleys with a local source grow in a broad range of directions and have a strong tendency to bifurcate, particularly on flatter surfaces. We consider these results with respect to two Martian cases: Louros Valles shows properties of seepage by a local source of groundwater and Nirgal Vallis shows evidence of a distant source, which we interpret as groundwater flow from Tharsis.

Description: Influence of grid aspect ratio on planetary boundary layer turbulence in large-eddy simulations Geoscientific Model Development Discussions, 8, 6021-6094, 2015 Author(s): S. Nishizawa, H. Yashiro, Y. Sato, Y. Miyamoto, and H. Tomita We examine the influence of the grid aspect ratio of horizontal to vertical grid spacing on turbulence in the planetary boundary layer (PBL) in a large-eddy simulation (LES). In order to distinguish them as much as possible from other artificial effects caused by numerical schemes, we used a fully compressible meteorological LES model with a fully explicit scheme of temporal integration. The influences are investigated with a series of sensitivity tests with parameter sweeps of spatial resolution and grid aspect ratio. We confirmed that the mixing length of the eddy viscosity and diffusion due to sub-grid scale turbulence plays an essential role in reproducing the theoretical −5/3 slope of the energy spectrum. If we define the filter length in LES modeling based on consideration of the numerical scheme, and introduce a corrective factor for the grid aspect ratio into the mixing length, the theoretical slope of the energy spectrum can be obtained; otherwise, spurious energy piling appears at high wavenumbers. We also found that the grid aspect ratio has influence on the turbulent statistics, especially the skewness of the vertical velocity near the top of the PBL, which becomes spuriously large with large aspect ratio, even if a reasonable spectrum is obtained.

Description: Carbon isotopes in the ocean model of the Community Earth System Model (CESM1) Geoscientific Model Development, 8, 2419-2434, 2015 Author(s): A. Jahn, K. Lindsay, X. Giraud, N. Gruber, B. L. Otto-Bliesner, Z. Liu, and E. C. Brady Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day geochemical ocean tracers. In order to allow a more direct comparison of climate model results with this large and currently underutilized data set, we added a carbon isotope module to the ocean model of the Community Earth System Model (CESM), containing the cycling of the stable isotope 13 C and the radioactive isotope 14 C. We implemented the 14 C tracer in two ways: in the "abiotic" case, the 14 C tracer is only subject to air–sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the 14 C additionally follows the 13 C tracer through all biogeochemical and ecological processes. Thus, the abiotic 14 C tracer can be run without the ecosystem module, requiring significantly fewer computational resources. The carbon isotope module calculates the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate formation, while any subsequent biological process such as remineralization as well as any external inputs are assumed to occur without fractionation. Given the uncertainty associated with the biological fractionation during photosynthesis, we implemented and tested three parameterizations of different complexity. Compared to present-day observations, the model is able to simulate the oceanic 14 C bomb uptake and the 13 C Suess effect reasonably well compared to observations and other model studies. At the same time, the carbon isotopes reveal biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean.

Description: The role of ecosystem function and emergent relationships in the assessment of global marine ecosystem models: a case study with ERSEM Geoscientific Model Development Discussions, 8, 6095-6141, 2015 Author(s): L. de Mora, M. Butenschön, and J. I. Allen Ecosystem models are often assessed using quantitative metrics of absolute ecosystem state, but these model-data comparisons are disproportionately vulnerable to discrepancies in the location of important circulation features. An alternative method is to demonstrate the models capacity to represent ecosystem function; the emergence of a coherent natural relationship in a simulation is a strong indication that the model has a appropriate representation of the ecosystem functions that lead to the emergent relationship. Furthermore, as emergent properties are large scale properties of the system, model validation with emergent properties is possible even when there is very little or no appropriate data for the region under study, or when the hydrodynamic component of the model differs significantly from that observed in nature at the same location and time. A selection of published meta-analyses are used to establish the validity of a complex marine ecosystem model and to demonstrate the power of validation with emergent properties. These relationships include the phytoplankton community structure, the ratio of carbon to chlorophyll in phytoplankton and particulate organic matter, the ratio of particulate organic carbon to particulate organic nitrogen and the stoichiometric balance of the ecosystem. These metrics can also inform aspects of the marine ecosystem model not available from traditional quantitative and qualitative methods. For instance, these emergent properties can be used to validate the design decisions of the model, such as the range of phytoplankton functional types and their behaviour, the stoichiometric flexibility with regards to each nutrient, and the choice of fixed or variable carbon to nitrogen ratios.

Description: Revision of the convective transport module CVTRANS 2.4 in the EMAC atmospheric chemistry–climate model Geoscientific Model Development, 8, 2435-2445, 2015 Author(s): H. G. Ouwersloot, A. Pozzer, B. Steil, H. Tost, and J. Lelieveld The convective transport module, CVTRANS, of the ECHAM/MESSy Atmospheric Chemistry (EMAC) model has been revised to better represent the physical flows and incorporate recent findings on the properties of the convective plumes. The modifications involve (i) applying intermediate time stepping based on a settable criterion, (ii) using an analytic expression to account for the intra-time-step mixing ratio evolution below cloud base, and (iii) implementing a novel expression for the mixing ratios of atmospheric compounds at the base of an updraft. Even when averaged over a year, the predicted mixing ratios of atmospheric compounds are affected considerably by the intermediate time stepping. For example, for an exponentially decaying atmospheric tracer with a lifetime of 1 day, the zonal averages can locally differ by more than a factor of 6 and the induced root mean square deviation from the original code is, weighted by the air mass, higher than 40 % of the average mixing ratio. The other modifications result in smaller differences. However, since they do not require additional computational time, their application is also recommended.

Description: Designing optimal greenhouse gas monitoring networks for Australia Geoscientific Instrumentation, Methods and Data Systems Discussions, 5, 247-283, 2015 Author(s): T. Ziehn, R. M. Law, P. J. Rayner, and G. Roff Atmospheric transport inversion is commonly used to infer greenhouse gas (GHG) flux estimates from concentration measurements. The optimal location of ground based observing stations that supply these measurements can be determined by network design. Here, we use a Lagrangian particle dispersion model (LPDM) in reverse mode together with a Bayesian inverse modelling framework to derive optimal GHG observing networks for Australia. This extends the network design for carbon dioxide (CO 2 ) performed by Ziehn et al. (2014) to also minimize the uncertainty on the flux estimates for methane (CH 4 ) and nitrous oxide (N 2 O), both individually and in a combined network using multiple objectives. Optimal networks are generated by adding up to 5 new stations to the base network, which is defined as two existing stations, Cape Grim and Gunn Point, in southern and northern Australia respectively. The individual networks for CO 2 , CH 4 and N 2 O and the combined observing network show large similarities because the flux uncertainties for each GHG are dominated by regions of biologically productive land. There is little penalty, in terms of flux uncertainty reduction, for the combined network compared to individually designed networks. The location of the stations in the combined network is sensitive to variations in the assumed data uncertainty across locations. A simple assessment of economic costs has been included in our network design approach, considering both establishment and maintenance costs. Our results suggest that while site logistics change the optimal network, there is only a small impact on the flux uncertainty reductions achieved with increasing network size.