人为气溶胶强迫可能是20世纪下半叶东亚夏季风年代际尺度减弱最重要的贡献因子。究其原因，以往研究普遍认为人为气溶胶排放增加导致东亚季风区海-陆表面热力对比减弱，从而减弱了东亚夏季风。但是，这些研究忽略了海洋对气溶胶强迫的慢响应对对流层上层热力结构的影响在气溶胶强迫驱动季风环流变化中所起的作用。本项目拟利用新一代全球气候模式比较计划（Coupled Model Intercomparison Project phase 5, CMIP5）中多模式开展的海-气耦合历史模拟和固定气候态海温的模拟结果以及一个气溶胶/大气化学-气候双向耦合模式，并结合再分析和探空观测数据，研究人为气溶胶强迫对东亚夏季对流层上层温度的影响及其与季风环流变化之间的联系，特别是揭示海洋对气溶胶强迫的慢响应影响对流层温度和季风环流的物理机制。本项目对于深入认识东亚夏季风变化的机理具有重要的意义。

Anthropogenic aerosol forcing is likely the most important contributor to the interdecadal weakening of the East Asian summer monsoon (EASM) circulation during the second half of the 20th century. The previous general conclusion was that the increases in anthropogenic aerosol emissions decrease the land-sea surface thermal contrast, thus weakening the EASM. However, those studies have overlooked the role of the effect of ocean response to aerosol forcing on upper-tropospheric thermodynamic structure in driving the change of the EASM circulation. In this proposal, we will investigate the impact of anthropogenic aerosol forcing on summer upper-tropospheric temperature over East Asia as well as its relation with the change of the EASM circulation using the coupled historical multi-model ensemble simulations and simulations with fixed sea surface temperature from the Coupled Model Intercomparison Program phase 5 and an aerosol/atmospheric chemistry-climate online coupled model, in combination with the reanalysis and radiosonde data. In particular, we will reveal the physical mechanisms of the effects of ocean response to aerosol forcing on tropospheric temperature and the EASM, The implementing of this project has significant implications for a further understanding on the mechanism of the EASM change.