Diagnosis of wet and dry events and its associated atmospheric circulation anomaly over Malawi, Southeast Africa

Abstract

This paper presents an analysis of December to February (DJF) season wet and dry events and their associated circulation anomalies during the period of 1978–2010 over Malawi. The study was conducted using meteorological daily observed rainfall datasets during the entire study period. A set of regional wet and dry indices with a scheme of classifying their severity was employed to classify the wet and dry into seven different grades using the Z-Index. The results reveal severe wet during 1997 and 2007 rainfall season, while extreme dry events were observed in 1992 and 2000 season. The wind components (u;v) and velocity potential/divergence analysis revealed that dry years were characterized by divergence at low level and convergence at upper troposphere, especially over region of study, Mozambique, Madagascar as well as North Madagascar. It was observed that there is a pattern of enhancement for vertical velocity (Omega) and Relative humidity during wet years and reduction during dry years. The SST uncovers dry years were manifested with negative anomalies over equatorial western Indian ocean and the eastern equatorial Pacific Ocean. Wet years were characterized by a pool of positive anomaly over the south west and equatorial of Indian Ocean, and a negative anomaly in the equatorial Pacific Ocean.