Analysis of summer monsoon rainfall over Maharashtra and its relation with SSTs

Abstract

This paper is based on the spatio-temporal analysis of daily, monthly and seasonal rainfall variability over Maharashtra state of the Indian region, for the period 1901–2017 during summer monsoon, viz., June through September. This analysis is carried out over Maharashtra’s four sub-divisions, where mean rainfall received for JJAS (1901–2017) is more over Konkan and Goa and east Vidarbha and less over Madhya Maharashtra. Coefficient of variation is considered to understand spatial variability of total rainfall received during JJAS by the state. The percentage of rainy days is found to be more for July and August months compared to June and September months as per the advancement of monsoonal flow noticeable through this study. Hence, contribution to JJAS rainfall more from July month proceeded with August month is considerable. September month contribution is the least; nevertheless its contribution is prominent from south Madhya Maharashtra. Rainfall variability is linked with El Nino and La Nina, by calculating composites of standardized rainfall anomalies and % rainy days during El Nino and La Nina years, which show that monthly and seasonal rainfall, are modulated by variations in SSTs of equatorial central Pacific Ocean. Thus this study aims to analyze the changing pattern of rainfall over Maharashtra and its sub-division as linking El-Nino and La-Nina events with rainfall received over small domain is the need of the hour as each region behaves differently during El-Nino or La-Nina.