Thesis (M.Sc.)-Cairo University,2022.

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The main objective of this work is to analyze the observational seasonal temperature of Egypt over the period 1968-2020. This period is divided in to two segments: the first one is from 1968 until 1995, while the second one starts at 1996 and ends at 2020. The trend of the temperature extreme indices is calculated over the period 1968-2020 using the Egyptian Meteorological Authority (EMA)‟s daily data for minimum and maximum temperatures. Thirteen extreme temperature indices were investigated, such as summer days, and warmest and coldest days. Also, the number of hot days, heatwave number, and cold wave number were analyzed for five stations, namely, Dabaa, Matrouh, Cairo, Aswan, and Hurghada. Furthermore, ERA5 reanalysis is validated with respect to EMA‟s observed daily maximum and minimum data for the five stations over the period 1981- 2020. The results show that there is the increase in the mean minimum seasonal temperature is greater than that in the mean maximum seasonal temperature. Also, they show that the trend of the number of hot days and heatwave number in all stations is significantly positive, while the trend of the number of cold days, cold spell duration indicator, cold wave numbers for the same stations is significantly negative. In addition, the ERA5 reanalysis product showed a good performance for simulating the daily maximum temperature in all stations except for Matrouh station in autumn, spring, and summer seasons. In regard to the daily minimum temperature, ERA5 data showed a good fit with respect to station data in all seasons except for the winter season. Future projection of extreme temperature indices were 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 and RCP8.5. COSMO-CLM and RegCM4 outputs were validated by comparison with EMA observed daily maximum and minimum temperature for the base period (1985-2005). Results showed that COSMO-CLM performs better than RegCM4 in simulating the daily minimum temperature particularly during the summer season, but no model performs better than the other regarding the daily maximum temperature. In terms of the future projection, RegCM4 model showed a significant increase in the number of heatwave numbers more than the COSMO-CLM under the RCP4.5 and RCP8.5 and a significant decrease in the cold wave numbers under the RCP4.5 scenario more than the RCP8.5 and COSMO-CLM.