RELATIONSHIPS BETWEEN CIRCULATION AND RAINFALL OVER INDIA DURING THE SOUTHWEST MONSOON SEASON .1. SURFACE PRESSURE

Rainfall over India during the southwest monsoon season exhibits large intraseasonal fluctuations. The surface pressure fields illustrate the important circulation changes and the general conditions of active and break monsoon situations. We have studied the relationship between these two successive fields at daily to monthly time scales using montly data, from July through September for an 11 year period (1966-1976). Lag relationships were also investigated to ascertain the nature of evolutionary patterns through which pressure affects rainfall and so assess the potential for predicting rainfall with the use of pressure fields. Finally, the relationship between pressure and rainfall (linear or non-linear) was examined with the use of quartile plots.