Projecting the Potential Evapotranspiration of Egypt using a high-resolution regional climate model (RegCM4)

This study aims to use the regional climate model (RegCM4) to examine the influence of climate change on potential evapotranspiration (PET) of Egypt under two future scenarios. To address such a topic, the calculated PET is first corrected in the historical period with respect to the long-term gridded PET data (Climate Research Unit; CRU) using a linear regression model (LRM) between RegCM4 and CRU. After that, the LRM is used to correct the two future scenarios Representative Concentration Pathways (RCP4.5 and 8.5) of the period 2006-2100. The RegCM4 was downscaled by the medium resolution of the Earth System Model of the Max Planck Institute (MPI-ESM-MR) with 50 km horizontal grid spacing over Middle East and North Africa (MENA) and then nested over Egypt with 20 km horizontal grid spacing. The results showed that the RegCM4 is able to capture the monthly variability of PET with respect to the CRU; furthermore the RegCM4 overestimates/underestimates the PET depending on the location under consideration. Also, the simulated PET was notably improved when the LRM was used. Such improvement is indicated by a low mean bias and a high standard deviation ratio (close to unity) between the corrected PET and CRU. In addition, the future PET projects a strong increased trend under the RCP8.5 scenario; meanwhile the future PET projects a weak increased trend under the RCP4.5 scenario.