SPATIAL AND TEMPORAL RELATIONSHIPS BETWEEN GLOBAL LAND-SURFACE AIR-TEMPERATURE ANOMALIES AND INDIAN-SUMMER MONSOON RAINFALL

Using the 60 year period (1931-1990) gridded land surface air temperat ure anomalies data, the spatial and temporal relationships between Ind ian summer monsoon rainfall and temperature anomalies were examined. C omposite temperature anomalies were prepared in respect of 11 deficien t monsoon years and 9 excess monsoon years. Statistical tests were car ried out to examine the significance of the composites. In addition, c orrelation coefficients between the temperature anomalies and Indian s ummer monsoon rainfall were also calculated to examine the teleconnect ion patterns. There were statistically significant differences in the composite of temperature anomaly patterns between excess and deficient monsoon years over north Europe, central Asia and north America durin g January and May, over NW India during May, over central parts of Afr ica during May and July and over Indian sub-continent and eastern part s of Asia during July. It has been also found that temperature anomali es over NW Europe, central parts of Africa and NW India during January and May were positively correlated with Indian summer monsoon rainfal l. Similarly temperature anomalies over central Asia during January an d temperature anomalies over central Africa and Indian region during J uly were negatively correlated. There were secular variations in the s trength of relationships between temperature anomalies and Indian summ er monsoon rainfall. In general, temperature anomalies over NW Europe and NW India showed stronger correlations during the recent years. It has been also found that during excess (deficient) monsoon years tempe rature gradient over Eurasian land mass from sub-tropics to higher lat itudes was directed equatowards (polewards) indicating strong (weak) z onal flow. This temperature anomaly gradient index was found to be a u seful predictor for long range forecasting of Indian summer monsoon ra infall.