| ABSTRACT | Abstract "Validation of multiple reanalysis data against Egyptian Meteorological Stations" The main objective of this work is to analyze the observational seasonal temperature of Egypt over the period 1968-2020. This period is divided to two segments: the first one is integrated from 1968 until 1995, while the second one starts at 1996 and it ends at 2020. Trend of the temperature extreme indices is calculated over the period 1968-2020 using Egyptian Meteorological (EMA) daily data for minimum and maximum temperatures. Thirteen extreme temperature indices are investigated; such as summer days, warmest and coldest days. Also, the amount of hot days, heat wave and cold wave numbers are computed for five stations: Dabaa, Matrouh, Cairo, Aswan and Hurghada. Furthermore, ERA5 reanalysis is validated with respect to EMA observed daily maximum and minimum data for the five stations over the period 1981 to 2020. The results show that increasing in the mean minimum seasonal temperature is greater than increasing in the mean maximum seasonal temperature. Also, it shows that the trend of the amount of hot days, heat wave numbers for all stations is significantly positive; meanwhile the trend of the amount of cold days, cold spell duration indicator, cold wave numbers for the same stations is significantly negative. In addition, the ERA5 reanalysis product shows a good performance for simulating the daily maximum temperature for all stations except for Matrouh station in Autumn, Spring and Summer Seasons. Regarding daily minimum temperature, ERA5 data shows a good fit with respect to station data in all seasons except for the winter Season. Future projection of extreme temperature indices is conducted by using two regional climate models: 1) COSMO-CLM - downscaled by the EC-Earth CMIP6 global climate model – under the ssps-8.5 scenario and 2) RegCM4 - downscaled by MPI-ESM-MR global climate model - under the two representative concentration pathway scenarios: RCP4.5, RCP8.5. COSMO-CLM and RegCM4 outputs are validated in comparison with EMA observed daily maximum and minimum temperature (for the base period 1985-2005). Results show that COSMO-CLM performs better than RegCM4 in simulating the daily minimum temperature particularly during the summer season, but there is no model performs better than the other regarding the daily maximum temperature. Regarding the future projection, RegCM4 model shows: 1) a significant increase in the number of heat wave numbers more than the COSMO-CLM under the RCP4.5 and RCP8.5 and 2) shows a significant decrease in the cold wave numbers under the RCP4.5 scenario more than the RCP8.5 and COSMO-CLM. Keywords: COSMO; Egypt; Extreme indices; Future scenario; RegCM4; Validation |