Monsoon Low-Pressure Systems in Monsoon Mission Climate Forecast System Version 2

Abstract

Synoptic-scale systems, such as monsoon low-pressure systems (LPSs), contribute significantly to seasonal mean monsoon rainfall. Therefore, realistic simulation of characteristics (i.e., intensity, frequency and propagation) of LPSs is crucial for reducing the dry rainfall biases in general circulation models. Recent studies have argued that the generation and propagation of LPSs are strongly modulated by the narrow coastal sea surface temperature (SST) fronts over the Bay of Bengal (BoB). Therefore, the present study addresses the improvement in LPS characteristics in a coupled model through better representation of coastal SST fronts over the BoB. LPSs over the Indian regions are tracked through the Tempest Extreme v2.1 tracking algorithm. Through a comparative analysis, the present study demonstrates that the recently developed coupled model, that is, the Monsoon Mission Climate Forecast System (MMCFS) version 2 (v2), simulates a higher number of LPSs generated with larger inland propagation as compared to the previous generation model (MMCFSv1). Correct location of positive vorticity anomaly, a larger extent of positive vorticity and circulation anomalies into the landmass and the stronger temporal evolution of sea level pressure or vorticity anomalies are a few of the favourable conditions that support the improved LPS characteristics in MMCFSv2.