Change in characteristics of Monsoon low pressure systems under a warming climate

The synoptic-scale tropical cyclonic disturbances that form over the monsoon trough region over the Indian subcontinent called monsoon low pressure systems (LPS) are the major rain bearers for the country. They are also known to cause extreme precipitation events leading to multiple catastrophic floods almost every year. Understanding the change in their characteristics under a warming climate is necessary for better preparedness and mitigation of their adverse effect. In this study, we use the Climate Earth System Model (CESM1.2.2) to investigate the impact of climate change on LPS characteristics over India. The model is run at 0.9°×1.25° horizontal resolution, and output is saved at 6-hourly intervals for LPS track analysis. Two experiments are performed: a present-day control simulation (CTRL) and an RCP8.5 simulation (indicating warmer climate) towards the end of the current century. LPS are tracked in the experiments using an Automated Tracking Algorithm using Geopotential Criteria (ATAGC) for a 37-year period in the control simulation and during 2070-2100 in the RCP8.5 scenario. As expected, an increase in mean monsoon precipitation and a decrease in monsoon circulation are simulated over the Indian subcontinent in RCP8.5 compared to CTRL. But the change in the number of LPS is insignificant under a warming climate. A shift is found in the number of LPS genesis over land and ocean, with a larger number of genesis over the land in the RCP8.5 scenario. The trend in precipitation is consistent with mean monsoon precipitation, i.e., an increase in the magnitude of mean and extreme precipitation associated with LPS occurs under a warmer climate. Results from the investigations on the likely causes of the model results will be presented at the meeting.