Understanding Forced Asian Monsoon Changes in Observations and Coupled Model Intercomparison Project - Phase 5 (CMIP5) Models

亚洲季风覆盖了印度、东南亚和中国的大部分地区，是世界上大部分人口的主要水源。该区域还产生了世界上很大一部分人为气溶胶，一些研究表明，气溶胶与温室气体以及人类土地利用和土地覆盖(LULC)的变化相结合，对亚洲季风降雨有重大影响。这项研究的目的是通过对观测资料的分析以及来自耦合模式比较项目第5版(CMIP5)的模式模拟来确定亚洲季风对人为强迫的响应。这项工作包括对模型模拟的检查，包括由个别人为因素(例如，仅限于气溶胶或仅限于温室气体增加)强制进行的模拟，以确定不同人类驱动因素对季风变化的相对贡献。进一步的工作包括使用两个大气环流模式进行模拟，以测试季风降雨对包括LULC变化在内的因素的响应，并确定遥远的海面温度变化的单独影响。由于季风降雨变化的巨大社会影响，特别是考虑到有研究表明，到2050年，由于气候变化，该地区可能会经历农业生产的大幅减少，这项工作具有更广泛的影响。在此开展的工作旨在确定导致季风变化的潜在物理机制，并确定模式模拟中发生的季风变化是否与观测证据一致。因此，这项工作试图为21世纪季风降雨量可能的变化提供更好的指导。

The Asian monsoon covers a region including India, Southeast Asia, and much of China, and is the primary source of water for a large portion of the world's population. The region also produces a large share of the anthropogenic aerosols worldwide, and several studies have suggested that aerosols, in combination with greenhouse gases and human land use and land cover (LULC) change, have a significant effect on Asian monsoon rainfall. The objective of this study is to determine the Asian monsoon response to anthropogenic forcing through the analysis of observations as well as model simulations from the Coupled Model Intercomparison Project version 5 (CMIP5). The work includes an examination of model simulations, including simulations forced by individual anthropogenic factors (for instance only aerosols or only greenhouse gas increases), to determine the relative contributions of the different human drivers of monsoon change. Further work includes simulations with two atmospheric general circulation models to test the monsoon rainfall response to factors including LULC change, and to identify the separate effect of remote sea surface temperature variations.The work has broader impacts due to the large societal impact of changes in monsoon rainfall, particularly given studies which suggest that the region could experience a substantial reduction in agricultural production by 2050 due to climate change. Work conducted here seeks to identify the underlying physical mechanisms which lead to monsoon change, and determine whether monsoon change occurring in model simulations is consistent with observational evidence. The work thus seeks to provide better guidance on likely changes in monsoon rainfall over the 21st century.