Frequency and tracks of anticyclones and their effect on rainfall patterns over Zimbabwe

Summary A frequency analysis of anticyclones over Southern Africa and the surrounding oceans is presented during drought and wet years. It is shown that the incidence of anticylones tends to be higher over the Atlantic Ocean during drought years. Wet years show an increased frequency of anticyclonic centres off the south-east coast of South Africa. An outbreak of cold air tends to be associated with the mobile anticyclones which move round the South African coast into the Indian Ocean. These cold air outbreaks are mostly characterized by an abrupt drop in temperature over Zimbabwe and a marked intensification of the prevalent low level south-easterly flow. Tropical convection associated with quasi-stationary systems within the ITCZ tends to intensify on the arrival of the surge winds. This enhancement of convection continues until the arrival of cold air which stabilizes the tropical atmosphere.With 10 Figures