Investigating the occurrence of rainfall extremes over the mountain Elgon region

Abstract

Global climate models indicate that the intensity of rainfall extremes is likely to increase as the climate warms up which may increase the occurrence of floods and landslides. This study therefore aims at investigating the occurrence of rainfall extremes over the Mt. Elgon region in Uganda. The study applied several statistical methods on the rainfall data obtained from Climate Hazards Group Infra-Red Precipitation with Station (CHIRPS) to achieve objectives of the study. CHIRPS data set is blended from both satellite (CHIRP) and station in-situ observations at 0.050 degree resolution to create gridded rainfall time series for trend analysis. These included the Mann Kendall trend test, simple linear regression, coefficient of Variation, Analysis of Variance and Standardised Precipitation Index. Both Mann Kendall trend test and simple Linear regression showed a significant increasing trend in annual rainfall received over Mt. Elgon region with slopes of 0.721 and 0.802 respectively. Results also indicate that September to December rainfall season recorded a greater increasing rainfall trend with a slope of 1.438 as compared to the March to May rainfall season with a slope of 0.321. Further analysis on the rainfall variation was done considering La Nina, El Nino, and Normal years and results indicate greater variations of CV>30% during El Nino years as compared to other years. SPI results indicated the occurrence of above normal rainfall (SPI>0) between 1987 and 1991, 2006 and 2008, 2010 and 2015, 2018. The results therefore indicate communities in Mt Elgon region are at a high risk of being affected by rainfall induced floods and landslides which calls for policy makers and authorities to intervene.