Structure and precursors of the 1992 / 93 drought in KwaZulu-Natal, South Africa from NCEP reanalysis data

Abstract

The historical context and potential causes and structure of the 1992/93 drought in KwaZulu-Natal are analysed using NCEP reanalysis data. The analysis indicates that increased westerly winds with surface marine lows and continental highs prevailed over Southern Africa. Anomalous divergence and subsidence occur over the eastern subcontinent, coupled with reduced tropical moist inflows. Mid-latitude confluence, anticyclonic vorticity and upper level convergence suppressed convection over KwaZulu/Natal. The precipitable water field reflects a SE-NW orientated stationary wave-train pattern over Southern Africa with KwaZulu-Natal anti-phase with the Zambezi valley. A meridional overturning cell is seen as a driving mechanism behind the 1992/93 drought over South Africa. The velocity potential shows a dipole between the Zambezi and the SW Indian Ocean, and it appears that the kinematic structure was more important than the thermodynamic. Impacts include a reduction in crop yield and streamflows, and a slowing of economic activity.


(WaterSA: 2003 29(2): 201-208)