A comparative investigation of weather anomalies over Africa during the 1972 drought and 1977-1978 wet period

Abstract

In 1972 the African continent experienced severe drought conditions. 'Jh~Sudano-Sahelian drought started in 1968and persisted through 1974. Contrary to 1972, the years 1977 and 1978 received near normal rainfall in most parts of Africa except in East Africa where the rainfall was above normal. Many comparative studies ha.ve+o <latebeen carried out in an attempt to understand the possible causes of the Sudano-Sahelian drought of 1972. In these studies the year 1967 was considered to have received nearnormal rainfall and subsequently was used in the comparative studies (Kanamitsu and Krishnamurti, 1977). Furthermore, downward trend in the Sudano-Sahelian rainfall is believed to have began in the early 1960'S (Nicholson, 1979). Thus the year 1967 may be considered part cf the below normal rainfall period. This study investigates the atmospheric anomalies which leCl.-tQe.bnormally dry weather conditions in 1972 and near normal rainfall in 1977 and 1978 but wet in East Africa. Radiosonde wind observations, temperature and geopotential heigfits have been used over Africa and its neighbourhood for the standard pressuj;elevels of 850mb, 7001,-0,500mb 300mb and 200mb J for wind data/and up to 100mb for temprature and geopotential heights dat. Using mean ,flow pattern, we get out the transient motion systems which are responsible for weather. The transient wind patterns are studied together, wi.t.hw ind flow patterns and divergence patterns of the transient vector and compared to the rainfall and rainfall anomaly levels during the different seasons 'of1972, 1977 and 1978