Future changes in mean and extreme precipitation over North-East Africa and Arabia

This study provides a first analysis of future changes in mean and extreme precipitation over Northeast Africa and the Arabian Peninsula. To this aim, we exploited projections from ten selected CMIP6 models (in part I) under various SSP greenhouse gases emission scenarios for the mid to late 21st century. We found a north-south differentiation in future changes in total precipitation for the JF and MAM seasons, with decreases in the north and moderate increases elsewhere, although model uncertainties are high, particularly for MAM. In contrast, the JJAS and OND seasons show larger positive changes with less model uncertainty. These increases in mean precipitation will be accompanied by an increase in the intensity and frequency of extreme precipitation events. In addition, the JJAS (+6.7%) and OND (+4.5%) seasons will contribute more to cumulative annual precipitation, while the JF (-1.3%) and MAM (-9.9%) seasons will experience a reduction. Over Djibouti, where the selected models are shown to perform well, downscaled and bias-corrected CMIP6 data using the CDF-t method indicate in addition that the return period of intense precipitation events (≥ 80 mm/day) causing documented flooding will decrease from 5 years historically to 1.4 years by the end of the 21st century under the SSP5-8.5 scenario. This robust result indicates the need to strengthen flood adaptation measures in Djibouti. Furthermore, similar downscaling exercises are recommended for other sub-regions in Northeast Africa and Arabia, given the consistent trend towards higher intensity rainfall.