The spatiotemporal distribution of rainfall anomaly index (RAI) in Iraq

Abstract

The patterns and distributions of rainfall systems determine the prevailing climate patterns for any region of the world. In this study, the spatiotemporal distribution of the rainfall anomaly index was revealed based on data from the Coupled Model Intercomparison Project (CMIP6) for daily rainfall amounts in twenty-four geographically and climatically diverse regions in Iraq for the time series (2016-2050) of the SSP2.5 simulation scenario projections. Overall, these results concluded that rainfall distribution varies temporally and spatially depending on the nature of the climate region and its geographical characteristics. Zakho station in Duhok Governorate within the Kurdistan Region recorded the highest total rainy cases, followed by Baghdad Governorate in the central region, and finally, Diwaniya station in the south, leading these stations in the temporal and spatial variability of the rainfall anomaly index. The spatial variance amplitude of the total rainy days was approximately 10% among all stations. The non-parametric Mann-Kendall analysis of general rainfall anomaly trends showed clear temporal variability among the stations, with five stations showing a positive trend, seven stations showing a non-significant negative trend, and the remaining stations showing a neutral trend at the significance level (α=0.05). The analysis indicated that only Mosul station in the northwest had a significant negative trend, indicating a clear anomaly in the rainfall systems characteristic of Iraq's climate.