全球变暖与亚洲夏季风北边缘带：CO_2增倍的数值模拟

Global Warming and North Edge of Asian Summer Monsoon:Numerical Experiment with Doubled CO_2

利用NCAR CAM3全球大气环流模式(包含CLM陆面模式)进行了20年(1998-2017年)CO2增倍的数值试验,并通过计算海陆热力差异,分析了环流形势、雨带分布和云量特征等物理量,研究了全球变暖对东亚夏季风北边缘带的影响。结果表明,CAM3大气环流模式能较好地描述东亚地区大尺度环流的季节变化特征,当CO2含量成倍增长后,将对亚洲经度范围内的夏季风北边缘的位置产生不同的影响,具体表现为100°～123°E地区北边缘位置偏北明显,100°E以西略偏北,123°～132°E略偏北幅度很小,132°E以东呈现出一定的偏北趋势。其原因可能是由于陆地增温有利于青藏高原低层气旋性环流的加强以及北半球纬向海陆热力差异的增加,从而导致我国西南和东南方向向北的水汽输送明显增加。研究表明,南北半球的海陆热力差异无明显变化,南北半球间的相互作用与北半球夏季风增强无明显的联系,两者的关系还有待进一步研究。

The change of north edge of the Asian summer monsoon under the global warming is investigated using the NCAR CAM3 global atmospheric circulation model through numerical experiment of doubled CO2.The overall large-scale features of the eastern Asian monsoon are captured rather well by the Control_run and doubled CO2 experiment.In doubled CO2 concentration experiment,the north edge is more northward,which indicates a stronger monsoon.The analysis demonstrates that the surface temperature increasing from enhanced radiative force makes the cyclonic circulation in the lower level of Qinghai-Xizang Plateau stronger,which further strengthens the zonal thermal contrast between sea and land;moreover the moisture content is remarkably increased in the North China.Furthermore,it is shown that the thermal difference between the Northern and Southern Hemispheres hardly changes comparing with the Control_run.Those imply that the interaction of both Hemispheres has a relatively small impact on the intensification of the Asian summer monsoon activity.