Sensitivity of South Asian summer monsoon simulation to land surface schemes in Weather Research and Forecasting model

Abstract

AbstractThe land surface scheme is crucial for the performance of regional climate models in dynamic downscaling application. In this study, we explore the sensitivity of the simulation with 10‐km resolution Weather Research and Forecasting (WRF) model to the land surface schemes in simulating South Asian summer monsoon. The WRF simulations for 19 summers from 2000 to 2018 are conducted with four different land surface schemes including Exp‐CLM4, Exp‐Noah‐MP, Exp‐PX, and Exp‐SSiB, with that the initial and boundary conditions for the WRF model simulations are provided from the NCEP‐FNL data. The ERAI reanalysis data, GHCN‐CAMS, and CRU gridded data are used to comprehensively evaluate the WRF simulations. Compared with verification data, the WRF model can reasonably capture the spatial patterns of summer mean large‐scale atmospheric circulation, 2‐m temperature and precipitation. The simulation results, however, are sensitive to the option of land surface scheme. The performance of Exp‐CLM4 and Exp‐SSiB is better than that of Exp‐Noah‐MP and Exp‐PX assessed by multivariable integrated evaluation (MVIE) method. To explore the dynamic and physical mechanisms behind the WRF model sensitivity to land surface schemes, the differences in the surface energy balance between the ensemble means Ens‐CLM4‐SSiB and Ens‐NoanMP‐PX are analysed in detail. The results illustrate that the intensity of the simulated sensible heat flux over South Asia is weaker in Ens‐CLM4‐SSiB than that in Ens‐NoahMP‐PX. The simulated wind fields are influenced due to the geostrophic adjustment process caused by large differences in geopotential height; thus, the simulations of 2‐m temperature and precipitation are all affected.