An assessment of the variability in mam rainfall over Uganda using TRMM satellite information

Abstract

The purpose of this study was to examine the March, April & May seasonal rainfall variability and the extent of deviation of rainfall from the seasonal averages for the years 1998-2019 using statistical techniques. Rainfall records were acquired from the TRMM-3B43 product at 0.25°×0.25° spatial resolution. The TRMM-3B43 product is a combination of data from TRMM data and the Global Precipitation Climatology Centre (GPCC) rain gauge datasets. The daily rainfall totals were summed into monthly totals for the season of March, April and May for the study period. These records were analyzed for the wet season (MAM) for 21 years since 1998. A non-parametric (Mann-Kendall) technique was used to test for the trend significance. The resultant test indicated a decreasing trend in seasonal rainfall in the region and this was at a rate of 6.61mm per year. The trend was insignificant at 95% confidence interval. This was further illustrated by the decreasing trend of the moving average of rainfall for the study region over the years of the study. And for the Maximum and minimum rainfall values, MAM maximum rainfall values show decreasing trends over time with anomalies recorded in the year 2018 where it was extreme high rainfall value of over 530mm. The minimum show rather a gradual increasing trend over time with lowest value recorded in 2017.