The influence of tropical cyclones on intraseasonal rainfall variability over Uganda: case study of the Lake Victoria basin

Abstract

This study investigated the influence of tropical cyclones (TCs) on intra-seasonal rainfall variability over the Lake Victoria Basin, Uganda. The region experiences significant rainfall fluctuations especially during the March-April-May (MAM) season, impacting agriculture, water resources, and socioeconomic development. This research aimed at (1) assessing trends in intraseasonal rainfall characteristics during MAM; (2) analyzing tropical cyclone climatology over the Southwest Tropical Indian Ocean (SWTIO); and (3) examining the relationship between the intraseasonal rainfall characteristics and TC activity. The study employed a mixed-method approach using observational and reanalysis datasets. Daily rainfall data from meteorological stations within the Lake Victoria Basin (1991–2020) were analyzed using the Pentad approach to identify trends in onset, cessation, and dry spell lengths. Tropical cyclone data (1990–2020) were sourced from the International Best Track Archive for Climate Stewardship (IBTrACS) and analyzed for frequency, intensity, and spatial distribution during the MAM season. Results show that the northern, western and southern parts of Lake Victoria basin had a decreasing trend on the onset dates while the Eastern part had an increasing trend in the onset dates. The southern and northern parts had an increasing trend while the western had a decreasing trend in the cessation dates. There was a decreasing trend in dry spell over the northern and southern parts. The dry spell frequency and the Tc distance land showed positive correlation in the southern, eastern and northern areas respectively. There is need of investing in advanced weather stations and modeling systems to improve rainfall predictions and early warning systems for extreme weather events for example tropical cyclones.