Evaluation of a high-resolution regional climate simulation over Greenland

A simulation of the 1991 summer has been performed over south Greenland with a coupled atmosphere–snow regional climate model (RCM) forced by the ECMWF re-analysis. The simulation is evaluated with in-situ coastal and ice-sheet atmospheric and glaciological observations. Modelled air temperature, specific humidity, wind speed and radiative fluxes are in good agreement with the available observations, although uncertainties in the radiative transfer scheme need further investigation to improve the model’s performance. In the sub-surface snow-ice model, surface albedo is calculated from the simulated snow grain shape and size, snow depth, meltwater accumulation, cloudiness and ice albedo. The use of snow metamorphism processes allows a realistic modelling of the temporal variations in the surface albedo during both melting periods and accumulation events. Concerning the surface albedo, the main finding is that an accurate albedo simulation during the melting season strongly depends on a proper initialization of the surface conditions which mainly result from winter accumulation processes. Furthermore, in a sensitivity experiment with a constant 0.8 albedo over the whole ice sheet, the average amount of melt decreased by more than 60%, which highlights the importance of a correctly simulated surface albedo. The use of this coupled atmosphere–snow RCM offers new perspectives in the study of the Greenland surface mass balance due to the represented feedback between the surface climate and the surface albedo, which is the most sensitive parameter in energy-balance-based ablation calculations.Peer reviewe

Urban Heat: Forward-Looking Climate Modeling for Nis, Serbia

We produced actionable data on heat stress in cities to inform analysis and client dialogue on the part of World Bank teams. We applied an urban-scale climate modeling framework to generate datasets describing modeled heat stress exposure for present-day and future conditions under selected climate scenarios (present, SSP1-1.9, SSP3-7.0). The study domain focuses on Nis, Serbia. More details about the dataset: The dataset includes calculations for each indicator across three scenarios (present, SSP1-1.9, SSP3-7.0) and three twenty-year periods (2001-2020, 2021-2040, and 2041-2060). The present period refers to 2001-2020, while the other two periods correspond to the two SSP scenarios. All indicators are available in both NetCDF and GeoTiff formats. The indicators are calculated at a resolution of 150 m, consistent with the UrbClim and WBGT simulations. Additionally, downscaled versions of the indicators are provided at a resolution of 30 m. The UrbClim and WBGT simulations, as well as the postprocessing, are conducted using the regional projection EPSG 32634. The NetCDF and GeoTiff data also adopt this projection. Furthermore, a GeoTiff data file with EPSG 4326 projection is included. All indicators are calculated as yearly averages. Some indicators also have additional calculations for seasonal averages, including Spring (MAM), Summer (JJA), Autumn (SON), and Winter (DJF). Images for quick viewing in png format visualizing the results for each indicator. Present denotes the period 2001-2020; 2030 denotes the period 2021-2040; & 2050 denotes the period 2041-2060. The NetCDF and GeoTiff data can be found in the data.zip; The PNG files for quick viewing can be found in quickview.zip; more information about the dataset, including the methodology, all available data list, contact information, etc. can be found in the Technical_Annex_Nis.doc

Surface mass balance of the Greenland ice sheet simulated with a coupled atmosphere-snow regional model

The 1990 and 1991 ablation seasons over Greenland are simulated with a coupled atmosphere-snow regional climate model with a 25 km horizontal resolution. The simulated snow water content allows a direct comparison with the satellite derived melt signal. The model is forced with 6-hourly ERA-40 reanalysis at its boundaries. An evaluation of the simulated precipitation and a comparison of the modeled melt zone and the surface albedo with remote sensing observations are presented. Both the distribution and quantity of the simulated precipitation agree with observations from coastal weather stations, estimates from other models and the ERA-40 reanalysis. There are overestimations along the steep eastern coast which are most likely due to the "topographic barrier effect". The simulated extent and time evolution of the wet snow zone compare generally well with satellite derived data, except during rainfall events on the ice sheet and because of a bias in the passive microwave retrieved melt signal. Although satellite based surface albedo retrieval is only valid in the case of clear sky, the interpolation and the correction of these data enable us to validate the simulated albedo on the scale of the whole Greenland. These two comparisons highlight a great sensitivity of the remote sensing observations to weather conditions. Our high resolution climate model has been used to improve the retrieval algorithms by taking more fully into account the atmosphere variability. Finally the good agreement of the simulated melting surface with the improved satellite signal allows a detailed estimation of the melting volume from the simulation