PREMONSOON SURFACE PRESSURE AND SUMMER MONSOON RAINFALL OVER INDIA

The relationship between the surface air pressure field during the pre-monsoon months and the Indian summer monsoon rainfall is analysed using climate data from 105 stations situated in Eurasia between 0 degrees-60 degrees N and 20 degrees-100 degrees E. Moreover, grid-point data for the whole northern hemisphere are used. Pressure during April over an area around 50 degrees N and 35 degrees E is found to show a significant negative correlation with the subsequent monsoon rainfall. During May the pressure over a large part of the study area south of 40 degrees N shows a significant correlation with its highest value in the heat low region over Pakistan. It is assumed that monitoring of pressure variations over this region may be useful in predicting monsoon rainfall, particularly the rainfall during the first half of the season. Certain limitations of the climate data in this region are also discussed.