Ecology, Environment and Conservation Paper

INDIAN SUMMER MONSOON ONSET VARIATIONS AND CONSECUTIVE RAINFALL OVER INDIA

M.V. Subrahmanyam, B. Pushpanjali and K.P.R. Vittal Murthy

Abstract

For an Indian agriculture and economy, summer monsoon plays a vital role. The date of monsoon onset changes in every year, the climatological date of onset of monsoon is on 1st June. In this article, we analyzed the rainfall variations in relation to monsoon onset dates for the period of 1970-2010. With respect to the onset date there is a variation of monsoon rainfall in the monsoons months (JJAS) and also with the average seasonal rainfall. In the study period, we found that monsoon onset delayed for 17 days in 1972 and there is a deficit in monsoon rainfall. On the contrary when the monsoon onset is early for 13 days in 1990, the rainfall is above normal. As it is well known, the global phenomena like El Nino/La Nina also affecting the delay or advance in the monsoon onset and also in subsequent rainfall. Detailed discussions about the onset dates and the consequences rainfall during the monsoon months are given.