Spatiotemporal investigation of meteorological drought variability over northern Algeria and its relationship with different atmospheric circulation patterns

This study examines the spatial and temporal variations of meteorological drought over northern Algeria based on the Standardized Precipitation Index (SPI) and Principal Component Analysis (PCA) with Varimax Rotation. It also evaluates the relationship between different atmospheric circulation indices and drought variability at seasonal and annual time scales. The atmospheric circulation indices considered in this assessment are the Southern Oscillation Index (SOI), the North Atlantic Oscillation (NAO) Index, the Westerly Index (WI), the two Mediterranean Oscillation Indices (MOI1) (MOI2), the Western Mediterranean Oscillation Index (WeMOI), the North Sea Caspian Pattern (NCP) Index, the Trans Polar Index (TPI), and the Eastern Mediterranean Pattern (EMP) Index. The obtained results indicate that drought varies widely over the study area, as four Rotated Principal Components (RPCs) were retained for the Varimax Rotation, which divided the study area into four drought sub-regions: the central and eastern coastal regions represented by RPC1, the western regions represented by RPC2, the eastern regions represented by RPC3, and the west-central southern regions represented by RPC4. Drought variability on seasonal basis was successfully associated with different atmospheric circulation indices, mainly with EMP at the eastern part of the study area, which gathers the sub-regions represented by RPC1 and RPC3, and with SOI, NAO, WI, MOI1, and MOI2 in the western part, which gathers the sub-regions represented by RPC2 and RPC4. Drought inter-annual variability was better explained by EMP in RPC1 sub-region, by SOI in RPC2 sub-region, by NCP in RPC3 sub-region, and by MOI1 in RPC4 sub-region. Another important outcome revealed by this study is the prevalence of a general increasing trend in drought conditions over the study area, with more statistically significant trends in the western regions. Overall, this study has resulted in a better understanding of the mechanisms responsible for drought variability over northern Algeria, constituting valuable material for enhancing drought forecasting and water resource planning.