On the linkage between extreme rainfall and the Madden-Julian Oscillation over the Indian region

The relationship between extreme rainfall events (ERE) and the Madden-Julian Oscillation (MJO) over the Indian Subcontinent is intriguing. In this regard, the study investigates in detail the association between the ERE and the MJO. Daily Tropical Rainfall Measuring Mission (TRMM) data were used for the period 1998-2015. The real-time multivariate MJO index was applied to classify active and suppressed phases of the MJO. The percentile-based threshold indices, change in probability, logistic regression models and composite analysis were used to understand the statistical and atmospheric circulation features. The results suggest that the frequency and rainfall contribution of the ERE were found to be higher during the active phases of the MJO across the seasons over the geographically distinct regions. The profound influence of the MJO on the ERE was found during the post-monsoon over the southern Indian peninsula and Bay of Bengal regions. During the Indian Summer Monsoon (ISM), the prominent signals of the MJO are limited to the south of 20 degrees N. The logistic regression and cumulative probability changes affirm the above results. The composite analysis of various diagnostic parameters reveals the background synoptic conditions during the post-monsoon and the propagation of the Rossby convective lobe during the ISM might facilitate the occurrences of the ERE during the active phases of the MJO. The study highlights the space-time evolution of the ERE and the relative influence of the MJO across the seasons. Besides, its insights have practical implications for the understanding and prediction of sub-seasonal rainfall extremes over the Indian Subcontinent.