The Annual Cycle of East African Precipitation

• DOI: 10.1175/jcli-d-14-00484.1
• Publication Date: 2014-12-04T18:59:00Z
• Authors: Wenchang Yang; Richard Seager; Mark A. Cane; Bradfield Lyon
• Keywords: Annual cycle; Atmospheric Circulation; Water cycle; Wet season; Atmospheric instability

Abstract East African precipitation is characterized by a dry annual mean climatology compared to other deep tropical land areas and bimodal cycle with the major rainy season during March–May (MAM; often called “long rains”) second October–December (OND; “short rains”). To explore these distinctive features, ERA-Interim data are used analyze associated cycles of atmospheric convective stability, circulation, moisture budget. The atmosphere over Africa found be convectively stable in general year-round but an dominated surface moist static energy (MSE), which phase cycle. Throughout year, circulation pattern convergence near surface, divergence lower troposphere, again at upper levels. Consistently, vertically integrated flux mostly negative across becomes weakly positive two seasons. It suggested that semiarid/arid climate its can explained ventilation mechanism, stability controlled import low MSE air from relatively cool Indian Ocean off coast. During seasons, however, off-coast sea temperature (SST) increases (and warmest long rains season) consequently imported into less stable. This analysis may aid understanding overestimates short commonly coupled models.