1.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences;2.College of Earth and Planetary Sciences, University of Chinese Academy of Sciences
In this study, based on observation and JRA55 reanalysis data sets, we systematically evaluate the performance of South Asian Summer Monsoon (SASM) simulated by FGOALS-g3 climate system model. We draw attention to the simulated differences between FGOALS-g3 and FGOALS-g2, coupled model and atmospheric model. Results show that compared with FGOALS-g2, the simulation of climatological Indian Ocean trade winds and the sinking branch of the Walker circulation during El Nin ?o are improved in the FGOALS-g3 owing to the change of local sea surface temperature (SST). However, the systematic cold biases in the middle and upper troposphere persist, causing the reduced meridional temperature gradient and weakened SASM, leading to the biases of descend motion and moisture divergence, and the thus still dry biases over the terrestrial monsoon trough in the FGOALS-g3. Meanwhile, the negative correlation between El Nin ?o—Southern Oscillation and Indian summer rainfall captured by FGOALS-g3 stays weaker than observation, resulting from the weaker descending motion caused by SST biases. Furthermore, results also show that the air-sea interaction-induced climatological SST biases compensate the wet biases in the SASM region via the change of atmospheric circulation and water vapor transportation. At interannual timescale, the inclusion of negative feedback process of SST—precipitation—cloud shortwave radiation in the coupled model effectively improve the biases intensity of rainfall and atmospheric circulation simulated by the atmospheric model; however, the westward biases of sinking branch of the Walker Circulation caused by the SST biases in the coupled model lead to greater wet biases in the Indian Peninsula.