Examining observed and projected patterns in seasonal rainfall extremes in Uganda: a case study of the greater Masaka region
Nassuuna, Evalyne Bulega
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Greater Masaka is a vast area located with the cattle corridor regions of Uganda. The region is very susceptible to changes in the rainfall patterns as this affects the nature of economic activities that are carried out in this area. The study main objective was to examine observed and projected patterns in seasonal rainfall extremes in Greater Masaka in Uganda during March to May (MAM) and September to November (SON) seasons. The study used observed daily rainfall for the period 1980-2015 from Kamenyamiggo meteorological station obtained from Uganda National Meteorological Authority (UNMA). This study also used model projected rainfall data under two Representative Concentration Pathways (RCPs) 4.5 and 8.5 for the period 2019-2080. Results from the observed rainfall for the period (1980-2015) showed statistically significant increasing trends during MAM and SON seasons with SON season showing a more moderate increase in the observed rainfall than the MAM season. Results from future changes in rainfall extremes showed significant changes in the mean and that for all indices used, projected increase in the frequency of indices used was significant under scenario RCP4.5 as compared to scenario RCP8.5. The study revealed a statistically significant trend in observed records for Simple Daily Intensity Index (SDII) index for both seasons and no statistically significant trends detected in the other indices. On the other hand, projected future trends for the indices under RCP4.5 results showed statistically significant trends for R10mm, R20mm and R95p indices and no significant trends for SDII. Projected future trends for the indices under RCP8.5 results showed no statistically significant trends with indices SDII and R95p, however, significant trends were observed in R10mm and R20mm. Over all, the indices used generally summarized a general increase in rainfall over the Greater Masaka leading to the rejection of the null hypothesis, thus, there is a significant trend in the frequency and intensity of rainfall extremes in the Greater Masaka.