Stratospheric zonal wind and temperature in relation to summer monsoon rainfall over India

The interannual variability of the Indian summer monsoon (June-September) r ainfall is examined in relation to the stratospheric zonal wind and tempera ture fluctuations at three stations, widely spaced apart. The data analyzed are for Balboa, Ascension and Singapore, equatorial stations using recent period (1964-1994) data, at each of the 10, 30 and 50hPa levels. The 10hPa zonal wind for Balboa and Ascension during January and the 30hPa zonal wind for Balboa during April are found to be positively correlated with the sub sequent Indian summer monsoon rainfall, whereas the temperature at 10hPa fo r Ascension during May is negatively correlated with Indian summer monsoon rainfall. The relationship with stratospheric temperatures appears to be th e best, and is found to be stable over the period of analysis. Stratospheric temperature is also significantly correlated with the summer monsoon rainfall over a large and coherent region, in the north-west of Ind ia. Thus, the 10hPa temperature for Ascension in May appears to be useful f or forecasting summer monsoon rainfall for not only the whole of India, but also for a smaller region lying to the north-west of India.