Dynamical downscaling with WRF for the Middle-East and North Africa

Abstract:

The Middle-East and North Africa (MENA) experience the highest risk of water stress in the world. This underlines the importance of climate analysis for water resources management and climate change adaptation for this region, particularly in transboundary basins such as the Tigris-Euphrates system. Such analysis, however, is difficult due to a paucity of high quality precipitation data. The network of gauge stations is quite sparse and the data are often available only at monthly time-scale. Satellite-based products, such as the Tropical Rainfall Measuring Mission (TRMM), offer better temporal resolution; however, these data are available only for periods that are short for hydroclimatic analysis, and they often misrepresent precipitation over regions with complex topography or strong convection. To fill this gap, we have implemented the Weather Research and Forecasting (WRF) Model, initialized with the NCEP/NCAR Reanalysis II, to generate high-resolution precipitation estimates for MENA. Several sensitivity analyses have been performed in order to find a set of physics parameters that appropriately captures the annual cycle and year-to-year variability of rainfall over select areas in MENA. The results show that WRF, particularly over highlands, estimates the precipitation more accurately than the satellite products. In addition to these reanalysis-driven simulations, we have performed several simulations using the historical and twenty first century outputs of a select number of GCMs available at the CMIP5 archive. These runs enable us to detect changes in rainfall behavior under different greenhouse gas scenarios and reveal synoptic to mesoscale mechanisms responsible for such changes.