青藏高原增暖对东亚夏季风的影响——大气环流模式数值模拟研究

20世纪50年代以来，随着全球海表面温度年代际变化和全球变暖现象的出现，东亚夏季风降水和环流场也出现相应的年代际变化。是什么原因引起这个长期的变化趋势？研究表明青藏高原增暖可能是导致东亚夏季风年代际变化的重要因子之一。为了能够更好地理解青藏高原地表状况对下游东亚季风的影响，作者使用德国马普气象研究所大气环流模式（ECHAM）进行一系列数值试验。在两组敏感性试验中，通过改变高原上的地表反照率从而达到改变地表温度的目的。数值试验结果表明:青藏高原增暖有助于增强对流层上层的南亚高压、高原北侧西风急流和高原南侧东风急流以及印度低空西南季风；与此同时，东亚地区低层西南气流水汽输送增强。高原增暖后降水场的变化表现为:印度西北部季风降水增加，长江中下游以及朝鲜半岛梅雨降水增多；在太平洋副热带高压控制下的西北太平洋地区和孟加拉湾东北部，季风降水减少。对数值模拟结果的初步诊断分析表明:在感热加热和对流引起的潜热加热相互作用下，南亚高压强度加强，东亚夏季低层西南季风增大、梅雨锋降水增强，高原东部对流层上层的副热带气旋性环流增加，以及对流层低层的西太平洋副热带高压增强。另外，在青藏高原增暖的背景下，孟加拉湾地区季风降水减弱。本项研究有助于更好地理解东亚夏季风年代际变化特征和未来气候变化趋势。

The Impact of the Tibetan Plateau Warming on the East Asian Summer Monsoon——A Study of Numerical Simulation

East Asian monsoon precipitation and circulation have experienced an interdecadal change in the last 50 years that was concurrent with the changes in global SST and recent global warming.What gives rise to this long term change has been an outstanding issue.One possible cause is the change over the Tibetan Plateau.To understand the possible impact of the Tibetan Plateau surface conditions on the downstream East Asian monsoon,a suite of sensitivity experiments were performed with Hamburg's atmospheric general circulation model(ECHAM).The land surface albedo was changed in two sets of sensitivity tests so that the Tibetan Plateau land surface temperature was changed accordingly.The results show that a warmer condition over the Tibetan Plateau tends to enhance the upper tropospheric South Asia high and the westerly jet stream to its north and the Indian monsoon to its south,meanwhile the moisture transport toward East Asia increases.The changes in the precipitation pattern are featured by increasing rainfall over northwestern India and Meiyu and decreasing rainfall in the regions under the control of Pacific subtropical high and the Bay of Bengal.Preliminary diagnostic analysis suggests that the plateau warming has initially increased sensible heating and convective heating locally,which then enhanced the low-level southwest monsoon transport toward down stream of the plateau,resulting in increased precipitation and latent heat release in eastern China.The changes in the overall diabatic heating strengthen the upper-tropospheric South Asia high and downstream subtropical trough.This result may have meaningful implications for understanding the interdecadal change and future change of the East Asian summer monsoon.