Examining the Characteristics of Historical and Future Rainfall Over the Sudan Rainfall Belt

Abstract

Global warming significantly affects human activities, especially those reliant on rainfall for agriculture. The IPCC's fifth assessment report predicts that extreme weather events like droughts and floods will become more frequent and severe in the 21st century due to rising greenhouse gas emissions. Therefore, the purpose of this study was to investigate how future rainfall patterns in Sudan Rainfall Belt would be influenced by a changing climate. To do this, the study examined the characteristics of historical and future rainfall over Sudan Rainfall Belt based on observed gridded precipitation datasets, verified three GCMs from CMIP6, selected the model that best replicated the current climate, and then used it to assess the future rainfall pattern under SSP2-4.5 and SSP5-8.5 scenarios. The study used CHIRPs v2.0 and CMIP6 datasets to examine characteristics of historical and future rainfall over Sudan’s Rainy Belt. The CHIRPs data period was from 1981 to 2022 and three GCMs from CMIP6 data were from 1981 to 2010 as baseline and from 2030 to 2099 as future projections. The future periods were divided into the near future (2030 – 2059) and the far future (2070 – 2099). The study area was divided into four zones. Mean, Coefficient of Variation, Rainfall Anomaly Index (RAI), and trend analysis were used to determine the spatial and temporal characteristics of observed rainfall. Root Mean Square Error (RMSE), Correlation coefficient, and Bias were used to verify the models. The linear scaling method was used to correct the GCMs output bias, and the projected change in seasonal rainfall was determined across the four zones under SSP2-4.5 and SSP5-8.5. The results showed variations in seasonal rainfall distribution over Sudan, with higher rainfall amounts observed in the southern parts (Zone 4) and portion of central parts (Zone 1, and 3) and decrease as goes northward. All the four zones manifested a significant increasing trend at 95% confidence levels in historical rainfall. The model verification results, MPI-ESM1-2-LR, INM-CM4-8, and BCC-CSM2-MR revealed the lowest RMSE and Bias in the southern parts and higher northward. In terms of correlation coefficients across all zones, the MPI-ESM1-2-LR (MPI) model exhibited superior performance at a 95% confidence level. The overall future changes in seasonal rainfall showed, Under the SSP2-4.5 scenario, a decrease in seasonal rainfall was projected for the near future with an average percentage of change between (-1% and -45%) over the four zones. However, under the more severe SSP5-8.5 scenario, a severe reduction in rainfall was projected across all zones with an average percentage of change between (-51% and -67%) compared to SSP2-4.5. Looking further v into the far future, both scenarios indicated an overall increase in seasonal rainfall with an average percentage of change between (49% and 96 %) for near and far future periods respectively. The study suggests that expected future change is attributed to the influence of climate change that will shift seasonal rainfall patterns. Therefore, this research provides more details on the expected change in seasonal rainfall in each zone of the rainy season and the total rainfall of each year across the four zones. Thereby providing a reasonable basis for agricultural planning, water resource management, and assessing climate change impacts in Sudan particularly in the study area in the future