Examining spatiotemporal strong signal characteristics of rainfall systems in East Africa

Abstract

East Africa is dependent on rain, and experiences two major rainy seasons from March to May and October to December. The main objective is to investigate the strong signal characteristics of rainfall systems and variability of wind patterns using the empirical orthogonal function (EOF) Mode 1 across different pressure levels over East Africa. This study utilized multiple datasets to analyze rainfall variability over East Africa, using monthly rainfall data from the Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) and others from 1991 to 2020. EOF analysis, the North test, and assessments of variance and correlation were analyzed using MATLAB R2023a. The result revealed that the northern regions demonstrated pronounced variability influenced by seasonal monsoons and jet streams, while the southern regions exhibited unique wind patterns. The vertical velocity analysis in EOF1 interactions between atmospheric dynamics in baroclinic and barotropic zones shows that temperature gradients drive notable vertical motions of rising and sinking air. The vertical cross-sectional analysis during EOF1 emphasized the importance of water vapor below 850 hPa, with specific humidity of 10 g/kg, which is essential for rainfall formation. Eastward water vapor condensation was associated with decreased precipitation, while higher humidity from the south led to increased rainfall. These findings underscore the need for regional circulation system monitoring to improve seasonal weather forecasts and future research.