The sensitivity of the Indian summer monsoon to a global warming of 2°C with respect to pre-industrial times
The sensitivity of the Indian summer monsoon to a global warming of 2°C with respect to pre-industrial times
复制标题
DOI：
10.1007/s00382-010-0942-8
复制
发表时间：
2011-11
期刊：
影响因子：
4.6
通讯作者：
W. May
中科院分区：
文献类型：
--
作者：
W. May
在这项研究中，评估了与工业化前时期相比全球变暖 2°C 相关的印度夏季风不同方面的未来潜在变化，重点关注导致这些变化的不同机制的作用。此外，这些变化以及潜在机制与明显更强的全球变暖超过 4.5°C 相关的相应变化进行了比较，与广泛使用的 SRES A1B 情景相关。该研究基于 ECHAM5/MPI-OM 耦合气候模型的两组四个集合模拟，每个模拟都从不同的初始条件开始。在一组模拟（2020-2200）中，温室气体浓度和硫酸盐气溶胶负荷的规定使得模拟的全球变暖相对于工业化前时期不超过 2°C。在另一组模拟中（1860-2200年），温室气体浓度和硫酸盐气溶胶负荷是根据2000年之前的观测数据和2000年后的SRES A1B情景来规定的。该研究揭示了与工业化前条件相比全球变暖2°C相关的印度夏季风的显着变化，即尽管大规模降水减弱，但夏季风降水却增强。季风环流。季风降雨的增加与多种不同的机制有关，其中印度地区大气水汽输送的加剧是最重要的机制。大范围季风环流的减弱主要是由于印度洋和中东部太平洋对流活动增强、热带西太平洋对流活动减少，导致印度洋上对流层低（上）层沃克环流出现大规模辐散（辐合）变化。沃克环流的这些变化导致印度地区低（高）层出现西（东）风异常。与全球变暖4.5°C相关的印度夏季风变化的比较表明，在全球变暖2°C的情景下，季风降水的加强和大范围季风环流（特别是对流层低层）的减弱都相对较强（相对于两种情景到20世纪末全球变暖的预测幅度）。季风降雨的较强增强与阿拉伯海和孟加拉湾蒸发量的较强增加有关，而印度洋与北部陆地之间经向温度梯度的较弱放大则导致了季风大范围流量的较大幅度减少。
In this study the potential future changes in different aspects of the Indian summer monsoon associated with a global warming of 2°C with respect to pre-industrial times are assessed, focussing on the role of the different mechanisms leading to these changes. In addition, these changes as well as the underlying mechanisms are compared to the corresponding changes associated with a markedly stronger global warming exceeding 4.5°C, associated with the widely used SRES A1B scenario. The study is based on two sets of four ensemble simulations with the ECHAM5/MPI-OM coupled climate model, each starting from different initial conditions. In one set of simulations (2020–2200), greenhouse gas concentrations and sulphate aerosol load have been prescribed in such a way that the simulated global warming dioes not exceed 2°C with respect to pre-industrial times. In the other set of simulations (1860–2200), greenhouse gas concentrations and sulphate aerosol load have been prescribed according to observations until 2000 and according to the SRES A1B scenario after 2000. The study reveals marked changes in the Indian summer monsoon associated with a global warming of 2°C with respect to pre-industrial conditions, namely an intensification of the summer monsoon precipitation despite a weakening of the large-scale monsoon circulation. The increase in the monsoon rainfall is related to a variety of different mechanisms, with the intensification of the atmospheric moisture transport into the Indian region as the most important one. The weakening of the large-scale monsoon circulation is mainly caused by changes in the Walker circulation with large-scale divergence (convergence) in the lower (uppper) troposphere over the Indian Ocean in response to enhanced convective activity over the Indian Ocean and the central and eastern Pacific and reduced convective activity over the western tropical Pacific. These changes in the Walker circulation induce westerly (easterly) wind anomalies at lower (upper) level in the Indian region. The comparison with the changes in the Indian summer monsoon associated with a global warming of 4.5°C reveals that both the intensification of the monsoon precipitation and the weakening of the large-scale monsoon circulation (particularly in the lower troposphere) are relatively strong (with respect to the magnitude of the projected global warming by the end of the twentieth century for the two scenarios) in the scenario with a global warming of 2°C. The relatively strong intensification of the monsoon rainfall is related to rather strong increases in evaporation over the Arabian Sea and the Bay of Bengal, while a rather weak amplification of the meridional temperature gradient between the Indian Ocean and the land areas to the north contributes to the relatively strong reduction of the large-scale monsoon flow.