Upper tropospheric circulation and thermal anomalies over Central Asia associated with major droughts and floods in India

Abstract

The composite upper tropospheric (200 hPa) circulation and thermal anomalies during April to June were examined with respect to seven drought years (1965, 1966, 1968, 1972, 1974, 1979 and 1982), three flood years (1961, 1970 and 1975) and twelve normal years (1962, 1963, 1964, 1967, 1969, 1971, 1973, 1976, 1977, 1978, 1980 and 1981) using the upper air data of 21 stations for 22 years (1961-1982). There were significant differences between anomalies during drought and flood years. The anomaly patterns during the normal years were similar to those of flood years, but the anomalies were weaker. It was found that a cyclonic (anticyclonic) anomalous circulation with cold (warm) temperature developed over central Asia near the Caspian Sea during April of drought (flood) years. These anomalies persisted and strengthened during the later months. The cold cyclonic anomalous circulation adversely affects monsoon performances due to excess Eurasian snow cover and the large-scale intrusion of dry westerlies into the Indian region.