Variations of the SO Relationship with Summer and Winter Monsoon Rainfall over India: 1872–1993

The lag correlations of the monthly and seasonal pressures at Darwin with the rainfall over India during summer (June–September) and winter (October–December) monsoons and their variations over 29 meteorological subdivisions in India are examined by using long time data for 122 yr (1872–1993). It is found that the summer monsoon rainfall over India has significant (at 5% level) positive correlation with the Darwin pressures during the previous June–August period, and significant negative correlation with the pressures during the concurrent March–May period and with the seasonal pressure tendency from winter to spring (March–May minus December–February). Of these, the correlations with the concurrent May (−0.36) and the winter to spring seasonal pressure tendency (−0.30) are strong. Similarly, the all-India rainfall during winter monsoon is found to have significant negative correlation with the Darwin pressures during the concurrent July and August. In this case, the correlation with the concurrent July pressures is strong (−0.21). During the winter monsoon season, southern peninsular India receives dominant rainfall and this rainfall is found to have only a weak positive correlation (0.17) with the concurrent September pressures at Darwin. The consistency of these relations during the period of study is examined by evaluating the 30-yr sliding window correlation coefficients. The anomaly rainfall patterns of the summer and winter monsoons over India during the years of the low and high values of the corresponding Southern Oscillation index are further examined.