This study tried to assess the impact of climate change on water resources of the upper Awash River sub- basin (Ethiopia) using a statistical downscaling model (SDSM). The future climatic parameters (rainfall, maximum and minimum temperatures) were generated by downscaling outputs of HadCM3 (Hadley Centre Coupled Model, ver-sion 3) general circulation model to watershed level for A2a (medium-high) and B2a (medium-low) emission scenarios at representative stations (Addis Ababa, Ginchi and Bishoftu). These SDSM generated climatic data were used to develop current/baseline period (1971–2010) and future climate change scenarios: 2020s (2011–2040), 2050s (2041– 2070) and 2080s (2071–2099). The projected future rainfall and mean monthly potential evapotranspiration at these stations were weighted and fed to HBV hydrological model (Hydrologiska Byråns Vattenbalansavdelning model) for future stream flow simulation. These simulated future daily flow time series were processed to monthly, seasonal and annual time scales and the values were compared with that of base period for impact assessment. The simulation result revealed the possibility for significant mean flow reductions in the future during Summer or “Kiremt” (main rainy season) and apparent increase during “Belg” or winter (dry season). Autumn flow volume showed decreasing trend (2020s), but demonstrated increasing trend at 2050s and 2080s. A mean annual flow reduction (ranging from 13.0 to 29.4%) is also expected in the future for the three studied benchmark periods under both emission scenarios. Generally, the result signals that the water resources of upper Awash River basin will be expected to be severely affected by the changing climate. Therefore, different adaptation options should be carried out in order to reduce the likely impact and ensure water security in the sub-basin.

This paper constitutes the sensitivity study of application the Polar WRF

model to the Svalbard area with testing selected parameterizations, including planetary

boundary layer, radiation and microphysics schemes. The model was configured, using

three one-way nested domains with 27 km, 9 km and 3 km grid cell resolutions. Results

from the innermost domain were presented and compared against measured wind speed

and air temperature at 10 meteorological stations. The study period covers two months:

June 2008 and January 2009. Significant differences between simulations results occurred

for planetary boundary layer (PBL) schemes in January 2009. The Mellor-Yamada-Janjic

(MYJ) planetary boundary layer (PBL) scheme resulted in the lowest errors for air

temperature, according to mean error (ME), mean absolute error (MAE) and correlation

coefficient values, where for wind speed this scheme was the worst from all the PBL

schemes tested. In the case of June 2008, shortwave and longwave radiation schemes

influenced the results the most. Generally, higher correlations were obtained for January,

both for air temperature and wind speed. However, the model performs better for June

in terms of ME and MAE error statistics. The results were also analyzed spatially, to

summarize the uncertainty of the model results related to the analyzed parameterization

schemes groups. Significant variability among simulations was calculated for January

2009 over the northern part of Spitsbergen and fjords for the PBL schemes. Standard

deviations for monthly average simulated values were up to 3.5°C for air temperature

and around 1 m s-1 for wind speed.