Investigation of the role of model integration time step size in numerical simulation of Kerala heavy rainfall events in a cloud resolving scale

This study examines the effects of planetary boundary layer (PBL) and integration time step size (TSS) schemes on high-resolution WRF simulations of two extreme rainfall events that occurred over Kerala in 2018 and 2019. GPM IMERG data were used to compare 16 experiments with two PBL schemes and four TSS values. The BouLac scheme, with a 30s TSS, best simulated the observed 24-hour rainfall during the 2018 Kerala flood, whereas MYNN2 more accurately depicted the vertical moisture and convective structure. Although the shorter time step didn’t reproduce the peak rainfall in the synoptic-driven 2019 event, it did improve the spatial structure in both cases. The simulated results was influenced by both TSS and the PBL scheme, and synoptic conditions changes was limited to finer TSS. The results suggest that a high-resolution model setup, support a better forecasting of extreme rainfall for disaster preparedness.