Modeling the impacts of the energy closure degree over the arid and semiarid areas of China on the East Asian regional climate

Abstract

Arid and semiarid areas are extremely sensitive to climate change. The atmospheric boundary layer in these areas acts as a major factor of matter exchange and energy transport for the land–atmosphere interactions. In this study, two turbulent transfer parameterization schemes respectively with surface energy closure and unclosure based on the Lanzhou university Semi-Arid Climate Observatory and Laboratory (SACOL) station are coupled into a regional climate model RegCM4.5 (referred to as Exp-BALANCE and Exp-IMBALANCE) to explore the effects of the surface energy closure degree on the East Asian summer monsoon simulations. The results show that the surface soil temperature simulated by Exp-BALANCE is lower than that simulated by Exp-IMBALANCE because energy transferred from the underlying surface increases so that the energy retained in the underlying surface decreases in Exp-BALANCE, which weakens sensible heat transport and decreases the surface air temperature in the case of Exp-BALANCE. This is because the net radiation absorbed by the underlying surface for Exp-BALANCE is in agreement with Exp-IMBALANCE, while the soil temperature simulated by Exp-BALANCE is lower than that of Exp-IMBALANCE. Compared with Exp-IMBALANCE, Exp-BALANCE can contribute to increasing the atmospheric energy, and more upward air flow begins to diverge as the anticyclonic circulation strengthens in the middle and upper tropospheres over the arid and semiarid regions. Consequently, the subtropical high moving to the northward is hindered, the rain belt stays in the South China for a long time, and the precipitation in Northeast China is reduced, but in the south of the Yangtze River, it is enhanced in the case of Exp-BALANCE.