Meteorological Structure of the 1992/93 Drought Over Eastern South Africa From Ecmwf and Satellite Olr Analyses

An analysis of the 1992/93 drought in eastern South Africa is undertaken for various climatic variables from ECMWF data. Increased westerly winds with surface marine lows and continental highs over southern Africa are prominent features that sustained drought during this period. Anomalous low-level divergence and mid-level subsidence were coupled with reduced tropical moist inflows. An area of reduced water vapour flux extended from 15–33°S and 15–35°E. Anticyclonic vorticity and upper level convergence suppressed convection over most parts of South Africa. Mid-latitude winds played a significant role in emphasising the signature of the drought through a northward (southwards) movement of the subpolar (subtropical) jet streams giving rise to a strongly diffluent kinematic forcing over eastern South Africa. Low-level westerly anomalies and upper-level easterly anomalies were prominent over east Africa. A previous characterisation of the 1992/93 drought at antecedent SON and peak summer season and at a larger spatial domain by Dube and Jury (2001) has indicated that the 1992/93 summer carried a non-ENSO signal though a few parameters analysed showed an El Nino-type of influence. This study is a discussion of the circulation structure specific to the eastern parts of South Africa, particularly KwaZulu-Natal.