Numerical Simulation of the Indian Monsoon Climate using the WRF Regional Climate Model

Abstract

Abstract Climate studies are essential in understanding the Earth's climate system and its dynamics. Numerical models play a significant role in these studies by simulating the behaviour of the atmosphere and providing insights into future climate scenarios. In the recent years, the Weather Research and Forecasting (WRF) model has emerged as a widely used tool for studying climate on regional scales. In the present study, we simulated the mean features of the Indian summer monsoon (June through September) climate using the WRF regional climate model. The WRF model with a horizontal resolution of 25 km is driven by the Community Climate System Model version4 (CCSM4) for the period 2006-2021 which is a part of the fifth generation of Coupled Model Inter comparison Project (CMIP5) using the Representative Concentration Pathway 6.0 (RCP6.0) over the South Asia Coordinated Regional Downscaling Experiment (SA-CORDEX) domain. The model is simulated on a continuous mode throughout its annual cycle for the period of integration. But for the presentation of results, the summer monsoon months of JJAS for the period 2007 to 2021 are only analysed. The performance of the model was assessed through the study of the spatial distribution of Air temperature (2m), Winds, Pressure, Rainfall, and the Vertical Integrated Moisture flux convergence (VIMFC). The simulated parameters were compared to those in ERA5 reanalysis and the India Meteorological Department (IMD) gridded rainfall. The performance of the WRF model was evaluated for simulating the regional scale precipitation over 5 homogenous rainfall zones of India. The WRF model accurately reproduces the Tropospheric Temperature Gradient (TTG) between the southern and northern regions. The sub-regional scale analysis of the simulated 2m temperature and precipitation for 30 meteorological subdivisions of India reveals that the WRF model performs better than the CCSM4 model. Results indicate that the model is able to capture the mean climatological features of the monsoon viz. monsoon onset, low-level Jet and the upper-level tropical easterly jet.