EXTREMES OF THE ENSO PHENOMENON AND INDIAN-SUMMER MONSOON RAINFALL

Characterizing every year during the 120 year interval 1871-1990 as a year of El Nino (EN), or Southern Oscillation minimum (SO), or equator ial eastern Pacific sea-surface temperature (SST) warm (W) or cold (C) episode or none (non-events), the corresponding summer monsoon rainfa ll departures for all India and for the 29 meteorological subdivisions were examined. The best relationship for droughts was with unambiguou s ENSOW (El Nino year with SO and W near the middle of the calendar ye ar) and for floods with C (cold SST). The droughts were generally wide spread, although Assam and Bengal might have had normal rainfall or ev en floods when other subdivisions had droughts. In some ENSOW years wh en all India rainfall was normal, the rainfall in subdivisions was eit her normal or mixed (droughts in some subdivisions, floods in others). However, droughts and floods occurred during other types of events al so, and ENSOW or C were neither sufficient nor necessary. Some floods and droughts were associated with incorrect type (floods during El Nin o, etc.), and some occurred during non-events, indicating that factors unrelated to EN, or SO, or W, or C may be more influential in some ye ars. (C) 1998 Royal Meteorological Society.