Evolution toward increasing aridity in Algeria: analysis of dry and wet periods from 1981 to 2100

Climate change has increasingly disrupted rainfall patterns worldwide, and Algeria is particularly vulnerable because of chronic water scarcity. This study investigates the evolution of dry and wet periods across five climatic zones, from Mediterranean to desert regions. Observed CHIRPS daily precipitation data for 1981–2020 were combined with projections from 33 CMIP6 models extending to 2100 under SSP245 and SSP585 scenarios. All datasets were regridded to 0.25° × 0.25°, and model biases were corrected using the CDF-t method. Consecutive Dry Days (CDD) and Consecutive Wet Days (CWD) were then calculated. Historical results indicate a slight decrease in dry spells in Mediterranean and desert zones, with no clear trend elsewhere. Future projections show increasing CDD in all regions, reaching about 39 additional days in northern Algeria during 2050–2075 under SSP245. CWD is expected to decline overall, especially in Mediterranean areas, with reductions of up to 2.5 days by 2075–2100 across the country.