Drought is an inevitable part of climate, even in regions of usually ample rainfall. Because of the effects of drought on food supply, long time series of occurrence exist in many parts of the world. Incidence is dominated by the long wave patterns and by weakening of the intertropical convergence zone. There are indistinct regularities, but once established, temporal persistence over several months is marked. There is little tendency for interannual persistence. The consequences of drought for soil erosion, crop production, water supplies, and hydroelectric power generation call for great managerial skills. Drought prediction would help, but the state of the art is highly imperfect. Mismanagement of land resources in semi-arid regions can lead to desert encroachment.
1 Paper presented at the 62nd Annual Meeting of the American Meteorological Society, San Antonio, Tex., on 14 January 1982.