基于CCSM4.0长期积分试验评估不同辐射强迫对中国干旱半干旱区降水的影响

本文基于气候系统模式CESM4.0长期积分试验，分析评估了工业革命前（1850年）及当前（2000年）两种辐射强迫作用（分别为太阳活动和温室气体）对中国北方干旱半干旱区降水的影响。结果表明，模拟结果与观测之间尽管存在一定的偏差，但仍能再现降水气候态的空间分布以及季节变化特征；两种辐射强迫下的降水长期变化均无明显趋势，但二者的差异却呈现出70~100年的准周期振荡；由人类活动引起的当前辐射强迫作用对降水的多年际变率幅度有一定影响，造成极端强降水事件出现的概率增多，而由太阳活动引起的辐射强迫作用主要对降水多年代际周期具有一定的调制作用。进一步分析表明，两种辐射强迫下中国北方干旱半干旱区降水年多年代际变率的主要模态基本一致，但人类活动引起的辐射强迫作用会影响降水多年代际变率与热带海温异常的相互作用的强度，从而改变降水多年代际变率的幅度。

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.