Rainfall Variability in Western Uganda

Authors: Hae Seung Sung*, Graduate Student, Georgia State University, Jeremy E Diem, Professor, Georgia State University
Topics: Climatology and Meteorology, Geographic Information Science and Systems, Africa
Keywords: rainfall variability, tropics, Equatorial Africa, satellite-based estimates, atmospheric reanalysis
Session Type: Poster
Day: 4/4/2019
Start / End Time: 8:00 AM / 9:40 AM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded

It is widely believed from previous studies that equatorial Africa has experienced a drying trend over the past several decades. But those studies have not always relied on the best available rainfall data, and there now exist high-resolution, multi-decadal data to assess rainfall variability and trends in the region. Using multiple datasets for the 1983-2017 period, this study examines rainfall variability and the atmospheric controls of rainfall days in western Uganda. Daily rainfall estimates were extracted from two satellite-based rainfall databases, and daily atmospheric data were extracted from two global reanalysis databases. There are two rainy seasons in western Uganda, from March to May and from August to November, except the northernmost region which shows a unimodal rainy season from late March to mid-November. The typical atmospheric conditions during the rainy seasons are characterized by decreased downward motion in the middle troposphere, westerly-wind anomalies in the lower troposphere, and high specific humidity in both the lower and middle troposphere. The temporal analysis of each rainy season revealed that the rainy seasons have started earlier– and thus increased in duration – over the past 35 years. The earlier season onset is caused by significantly increased rainfall in the weeks just prior to the typical start of the rainy seasons. These results run counter to the prevailing view – based on analyses of inappropriate rainfall data – of western Uganda that the rainy seasons have been getting shorter and annual rainfall has decreased over the past several decades.

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