Optimizing WRF as a regional climate Downscaling Tool for Hydro-climatological Applications in the Eastern Nile Basin

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Authors

Mahmoud Osman , George Zittis, Mohammed AbouElHaggag, Ahmad W. Abdeldayem, Jos Lelieveld

Abstract

Most of the Nile water inflow at High Aswan Dam (HAD), Egypt, originates from the Ethiopian plateau, providing the main source of water for the Eastern Nile (EN) basin. The Weather Research and Forecasting (WRF) model using ARW (Advanced Research WRF) dynamical core is configured for a domain centered over the EN with a parent domain defined for the Middle East – North Africa (MENA) by the CORDEX. WRF physics parameterization sensitivity experiments are carried out to select an optimum combination of physics schemes to reproduce observed climate conditions. The model skill is also examined by downscaling the ERA-Interim reanalysis dataset from 1980 to 2009 over the EN basin domain.
The WRF performance is assessed using gridded observational datasets for precipitation, temperature and evapotranspiration. The model is tested for four different configurations in two-year simulations to determine the optimal combination of physics parameterizations prior to the 30-year downscaling experiment. The results indicate accurately modelled temperature and evapotranspiration fields, however, with significant positive precipitation biases, especially over the highlands. The bias-corrected precipitation data is coupled to the semi-distributed hydrological rainfall-runoff model (SWAT) model, previously configured for the Baro-Akobo-Sobat sub-basin. The simulated flow hydrograph based on bias-corrected WRF simulations yields high correlations and Nash-Sutcliffe Efficiency coefficients for the observed flow hydrographs. Results indicate that the simulated precipitation fields from WRF should be subject to bias correction prior to use in hydrological models especially for impact studies.

DOI

https://doi.org/10.31223/osf.io/fx7aw

Subjects

Civil and Environmental Engineering, Climate, Earth Sciences, Engineering, Hydrology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Keywords

bias correction, WRF, Dynamic downscaling, Eastern Nile Basin, Precipitation patterns

Dates

Published: 2019-06-18 10:16

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License

CC BY Attribution 4.0 International

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