PROBABILITIES OF EXCESS AND DEFICIENT SOUTHWEST MONSOON RAINFALL OVERDIFFERENT METEOROLOGICAL SUBDIVISIONS OF INDIA

Temporal distribution of southwest monsoon (June - September) rainfall is very useful for the country's agriculture and food grain productio n. It contributes more than 75% of India's annual rainfall. In view of this, an attempt has been made here to understand the performance of the monthly rainfall for June, July, August and September when the sea sonal rainfall is reported as excess, deficient or normal. To know the dependence of seasonal rainfall on monthly rainfall, the probabilitie s of occurrence of excess, deficient and normal monsoon when June, Jul y, August and also June + July and August + September rainfall is repo rted to be excess or deficient, are worked out using the long homogeno us series of 124 years (1871-1994) data of monthly and seasonal rainfa ll of 29 meteorological sub-divisions of the plain regions of India. I n excess monsoon years, the average percentage contribution of each mo nsoon month to the long term mean (1871-1994) seasonal rainfall (June - September) is more than that of the normal while in the deficient ye ars it is less than normal. This is noticed in all 29 meteorological s ub-divisions. From the probability analysis, it is seen that there, is a rare possibility of occurrence of seasonal rainfall to be excess/de ficient when the monthly rainfall of any month is deficient/excess.