Effects of Radiative Forcing on Precipitation over Arid and Semi-arid Region in China Based on CCSM4.0 Simulation

Based on long-term simulations of the Community Climate System Model version 4.0 (CCSM4.0) forced by preindustrial (1850) and present (2000) radiative factors (e.g., greenhouse gases and aerosols, solar, and volcanic aerosols), effects of radiative forcing on precipitation over the arid and semi-arid region in China are investigated. The result shows that the model simulations can well capture the spatial pattern and seasonal variation of long-term mean precipitation despite certain biases in the simulations. There exists little difference in long-term precipitation trend between the simulations forced by the preindustrial and present radiations; however, regional mean difference in precipitation between the two simulations shows a 70-100-year quasi-periodic change. The simulation with present radiative forcing displays large amplitude in multi-decadal precipitation variation and obvious increases in the frequency of heavy and extreme precipitation. In contrast, the simulation with preindustrial radiative forcing shows a roughly 100-year quasi-periodic variation that is likely related to the solar magnetic activity cycle. Further analysis shows that the leading modes of multi-decadal precipitation variability forced by the preindustrial radiation are nearly consistent with those forced by the present radiation, while the present radiative forcing related to human activities can affect the interaction between the multi-decadal precipitation variability and tropical sea surface temperature (SST) anomaly, which in turn modulates the amplitude of the multi-decadal precipitation variability over the arid and semi-arid region in China.