Sensitivity of the mean and variability of Indian summer monsoon to land surface schemes in RegCM4: Understanding coupled land‐atmosphere feedbacks

Abstract

A relatively simple land surface model, the Biosphere‐Atmosphere Transfer Scheme (BATS) and the more complex Community Land Model (CLM3.5) coupled to RegCM4 are used to investigate land‐atmosphere feedback processes during the Indian summer monsoon. Model simulations for 27 years show that the mean and interannual variability of rainfall and surface air temperature are affected significantly due to differences in the formulation of evapotranspiration and hydrological processes between BATS and CLM3.5, prescribed land use, land cover data and changes in net radiation. RegCM4 with CLM3.5 (RCLM) shows a reduction in surface moisture flux and precipitation but an increase in surface air temperature over most parts of India as compared to RegCM4 with BATS (RBAT). In terms of the mean and interannual variability of rainfall over central India, RBAT performs better than RCLM. Evapotranspiration over central India is found to be less (more) sensitive to soil wetness variations in RCLM (RBAT) compared to the multimodel estimate from the Global Soil Wetness Project, that is mainly attributed to the differences in ground evaporation and transpiration. Changes in evaporation efficiency between the models also lead to a reduction in the land‐atmosphere coupling strength for precipitation in RCLM. Furthermore, such changes decrease the convective instability over central and eastern India in RCLM leading to weakened convection, reduced large‐scale moisture convergence and precipitation over land. Observations of soil moisture, surface fluxes, and radiation are needed for better understanding and improvement of coupled land‐atmosphere feedbacks in models during the Indian summer monsoon.

Comparison of convective parameterizations in RegCM4 experiments over China with CLM as the land surface model

“…The magnitude of the cold bias generally varies within 1993), which had been used solely for many years in the model. A brief introduction to BATS and CLM in RegCM4 can be found in Giorgi et al (2012) and Halder, Dirmeyer, and Saha (2015).…”

“…Gao et al 2012). Furthermore, while CLM offers improvements in terms of land-atmosphere exchanges of moisture and energy and associated surface climate feedbacks compared with BATS (Steiner et al 2009), its use may lead to a poorer performance of RegCM compared with the relatively simple land-surface model of BATS; for example, over India, as reported by Halder, Dirmeyer, and Saha (2015). Thus, the performance of RegCM4 when using CLM (RegCM4-CLM) needs to be evaluated before its further application in climate and climate change simulations.…”

Investigating the impact of land-use land-cover change on Indian summer monsoon daily rainfall and temperature during 1951–2005 using a regional climate model

“…The dynamical core of RegCM4 is from the NCAR -Pennsylvania State University (PSU) Mesoscale Model version 4 (MM4), which is a compressible, finite difference model with hydrostatic balance and vertical σ coordinates. The NCAR CCM3 radiation scheme (Kiehl et al, 1996) and a planetary boundary layer scheme based on a non-local diffusion concept (Holtslag et al, 1999) are used for our simulations. We have also used the parameterization scheme of Zeng and Beljaars (2005) that allows for a realistic representation of the diurnal variation of sea surface skin temperature.…”

Coupled Land‐Atmosphere Regional Model Reduces Dry Bias in Indian Summer Monsoon Rainfall Simulated by CFSv2

“…Here we use a regional climate model, the Weather Research and Forecasting model (WRF) coupled to two land surface models, Community Land Model (CLM) and Noah land surface model (Noah), driven by CFSv2 boundary conditions (Halder et al, ; Maharana & Dimri, ; Pattnayak et al, ; Singh et al, ; Srinivas et al, , ; Unnikrishnan et al, ). We aim to understand the impact of land surface processes in the dry bias over Central India, specifically over the Ganga basin region.…”