亚洲夏季风对偶极子型人为气溶胶排放变化的响应特征与机理

利用第六次国际耦合模式比较计划（Coupled Model Intercomparison Project Phase 6, CMIP6）中的两组子试验，结合线性斜压模式模拟的结果，研究了近年来亚洲内部出现的东亚减少、南亚增加的偶极子型人为气溶胶排放变化调控亚洲夏季风响应的特征及物理机制。对东亚夏季风而言，在考虑海洋-大气耦合作用的气候系统总响应中，东亚夏季风环流和降水显著地加强；在不考虑海洋调控作用的大气直接响应过程中，东亚人为气溶胶排放减少导致的陆地升温使得海陆温差增大，进而通过引起东亚陆地上的气旋式环流异常加强东亚夏季风环流和降水。对南亚夏季风而言，其在偶极子型人为气溶胶强迫下呈现出更为复杂的变化特征。在大气直接响应过程中，人为气溶胶强迫引起的海陆热力差异变化导致南亚夏季风环流减弱、降水减少。在考虑海洋-大气耦合过程的总响应中，南亚夏季风环流表现出微弱增强，同时印度次大陆的南亚夏季风降水也出现增多的异常变化。这表明，局地和海洋-大气动力耦合过程在区域气候对人为气溶胶强迫的响应中扮演着非常重要的角色。此外，通过线性斜压模式发现，东亚和南亚局地的人为气溶胶强迫导致的大气加热场异常不仅能影响局地的夏季风环流，还可以通过引起大范围的表面气压异常进而调控整个亚洲夏季风环流的变化。

Response of Asian summer monsoon to the dipole pattern of anthropogenic aerosol forcing and its mechanism

This study uses two sets of experiments from the Coupled Model Intercomparison Project Phase 6 (CMIP6), as well as the idealized results from the Linear Baroclinic Model experiments, to investigate the responses of Asian summer monsoon to the dipole pattern of anthropogenic aerosol forcing in Asia and their physical mechanisms. Since the 21st century, the anthropogenic aerosol emission over South Asia has kept its increasement, while it increases in the first decade and then rapidly decreases over East Asia, and this feature will continue in the future. In the coupled climate system considering both the direct atmospheric responses and the sea surface temperature mediated atmospheric responses, the East Asian summer monsoon (EASM) is strengthened by the intensified and westward shifted western Pacific subtropical high, and the precipitation is intensified as well. In the direct atmospheric responses without considering the coupled ocean-atmosphere interaction processes, the declined East Asian anthropogenic aerosol emissions increase the land-sea thermal contrast by inducing an anomalous land warming due to their radiative effect, which also strengthens the EASM and precipitation by generating the cyclonic surface pressure anomaly in the East Asian land regions. For the South Asian summer monsoon (SASM), it shows more complicated responses due to the dipole pattern of anthropogenic aerosol forcing, with weakened SASM and reduced precipitation in the direct atmospheric responses but a gently intensified SASM in the coupled responses with increased precipitation anomalies in the Indian sub-continent. This suggests the important role of the coupled ocean-atmosphere interaction processes in shaping the regional climate responses to anthropogenic aerosol forcing. In addition, by using the Linear Baroclinic Model experiments, it demonstrates that the atmospheric heating anomaly resulted from the anthropogenic aerosol emissions in East Asia and South Asia may not only lead to localized summer monsoon responses, but also can regulate the larger-scale summer monsoon circulation changes by causing the surface pressure anomalies remotely.