Evaluating the Performance of BCC-CSM2-MR Model in Simulating the Land Surface Processes in China

Abstract

This study compares the CMIP6 （Coupled Model Intercomparison Project Phase 6） historical experiment results of BCC-CSM2-MR （Beijing Climate Center-Climate System Model-Medium Reslution） with GLDAS （Global Land Data Assimilation System） dataset and site-observed data to systematically evaluate the performance of BCC-CSM2-MR in simulating the land surface variables， such as surface soil temperature， upper soil moisture and surface energy balance components in China.And the causes of the model biases are also deeply discussed.The spatial correlation coefficient， temporal correlation coefficient， Taylor score and root mean square error between the observed data and GLDAS data and the model data are calculated to quantitatively analyze the simulation ability of BCC-CSM2-MR to land surface variables.The results show that the model can well simulate the spatial distribution and variability of land surface variables， but the model biases in quantity are still obvious.The spatial correlation coefficient and Taylor score between the simulated land surface soil temperature， upward net long wave radiation flux and surface upward latent heat flux by BCC-CSM2-MR and GLDAS are above 0.8 in each season， and it shows that the simulation performance of above variables is relatively great.Compared with GLDAS data， the model overestimates the summer surface soil temperature over southeastern China， but it tends to underestimate the surface soil temperature over most China in all seasons with much larger underestimation over the Qinghai-Xizang plateau in winter and spring.From the model error analysis， it can be concluded that the precipitation underestimated by the model leads to the overestimated surface downward shortwave radiation over southeastern China in summer， which leads to the overestimated surface soil temperature there.The surface albedo overestimated by the model results in the underestimated surface net downward shortwave radiation over the Qinghai-Xizang plateau， which further leads to the underestimated surface soil temperature， obviously in winter and spring.In addition， the model seriously underestimates （overestimates） the upper soil moisture over southeastern China in all seasons （Qinghai-Xizang plateau in winter and spring）， and the simulation effect of the characteristics of time evolution of deep soil time is better than that of upper soil， this is mainly resulted from the biases in the modeled precipitation.Meanwhile， the overestimation of upper soil moisture and 10m wind speed leads to the overestimated surface upward latent heat flux over Qinghai-Xizang Plateau in the winter and spring.After the model evaluation， it can be found that the simulation performance of BCC-CSM2-MR to land surface variables still needs to be improved and the causes of the model biases are complicated.

Keywords

• qinghai-xizang plateau
• bcc-csm2-mr
• model evaluation
• land surface process
• china