Rainfall contribution of North Indian Ocean cyclonic disturbances over India in a warming climate

Abstract

Rainfall associated with cyclonic disturbances (CDs) poses mostly significant threat to the society. Such type of systems and their remnants are capable of producing heavy rainfall, which often produce flash flooding. The trend for annual variation of CD rainfall (CDR) anomaly is decreasing along with CD anomaly during pre-monsoon season. The trend for CDR anomaly is observed to be almost stable while the CD anomaly is decreasing drastically in the post-monsoon season, indicating increased amount of rainfall is contributed by CDs over India in this period. Among eastern coastal states, Andhra Pradesh (AP), Tamil Nadu (TN), Mizoram, and Tripura and among western coastal states, Kerala (KL), Karnataka (KA) and Gujarat (GJ) received most of the accumulated rainfall in pre-monsoon season. During post-monsoon season, Odisha (OD), AP and TN received the highest rainfall contribution from CDs. Jharkhand, KL, KA, parts of Maharashtra (MH) and coastal GJ received significantly higher amount of rainfall in comparison to other interior places. Up to ~70% of rainfall is contributed by CDs over GJ, nearly 20-30% over AP and 15-18% over western Rajasthan during pre-monsoon. During post-monsoon season, considerable rainfall (60% of annual value) contribution is seen over all states. For pre-monsoon, the CD days are low, however the annual average rainfall is high during MJO periods. La-Nina periods contributed second highest annual average CDR during pre-monsoon season. For post-monsoon season, Negative IOD and La-Nina contributed higher CDR and the maximum CD days are also observed to be higher. The WRF simulated CDR are observed to be very low than that observed by IMD, however for the post-monsoon the spatial distribution of CDR is well predicted by the WRF model.