Sensitivity of runoff parameterization schemes in regional climate simulation of Indian summer monsoon

Abstract

In this study, we examine the sensitivity of the Indian Summer Monsoon (ISM) to runoff parameterizations in a non-hydrostatic Regional Climate Model (RegCM) for the period from 1982 to 2018. The experiments comprise parameterizations namely SIMTOP control (CTL) scheme and Variable Infiltration Capacity (VIC) scheme. Both simulations were forced with ERA interim analysis and evaluated with respect to observation and reanalysis products. The results revealed that the VIC simulated rainfall exhibiting a good agreement with India Meteorological Department (IMD) gridded rainfall as compared to the CTL experiments. The temperature features also were simulated relatively well in VIC than CTL especially over the monsoon core region. Similarly, spatial characteristics of soil moisture, relative humidity, total cloud cover, surface net radiation, sensible heat flux, and latent heat flux were also performing better with VIC with respect to ECMWF Reanalysis fifth version (ERA5) products. Further, the extreme monsoon rainfall seasons are better simulated with VIC driven experiment. The interannual variations of rainfall, soil moisture, sensible heat flux, and latent heat flux explained the dominance of VIC simulations over CTL which further lies in alignment with the aforesaid findings. However, these have been validated with statistical skill score named Nash-Sutcliffe coefficient and mean absolute error. The statistical analyses further corroborated the ISM simulations are better performed with VIC runoff parameterization than the CTL.