IPCC耦合模式对我国夏季降水的未来变化预估

【作者】 陈活泼； 孙建奇； 王会军；

【机构】 中国科学院大气物理研究所竺可桢-南森国际研究中心； 中国科学院气候变化研究中心； 中国科学院研究生院；

【摘要】 本文利用第四次政府间气候变化专门委员会(IPCCAR4)的15个耦合气候模式在不同排放情景下的模拟结果,对我国夏季降水及相关环流场的未来时空变化特征与不确定性作了研究。结果表明,在全球变暖背景下,我国夏季降水表现出较强的局地特征。其中,我国东部和高原地区的降水在21世纪表现出明显的增加趋势,而且这种趋势随着变暖的加剧而增强,同时模式模拟结果之间的一致性也更好,表示这一结果的可信度较高。在全球变暖背景下,我国新疆南部地区表现为持续的降水减少趋势,而我国西南地区夏季降水的变化则呈现出先减少(21世纪初)后增加的特征,不同模式对降水这些局地特征的模拟也都表现出较好的一致性。其他地区夏季降水在21世纪的变化不大,同时模式模拟的一致性也较差。多模式模拟的我国未来百年夏季降水的这些变化特征在温室气体高、中、低不同排放情景下基本一致,A2情景预估结果变化最大,A1B次之,B1相对最小。另外,从这15个耦合模式中挑选出对我国夏季降水现状模拟最好的3个模式,并利用这3个模式模拟结果对我国未来夏季降水变化进行了预估,其结果与15个模式的预估结果基本一致。东亚夏季环流场的预估结果显示,在全球变暖的背景下,大部分模式的模拟结果都表明,东亚夏季风环流有所增强,从而使得由低纬度大洋和南海地区向我国大陆的水汽输送增加,造成该地区大气含水量的增多,从而为我国东部地区夏季降水的增加提供有利条件。此外,随着全球变暖的加剧,西太平洋副热带高压持续增强,其变化对我国东部地区夏季降水的影响程度和范围也明显增大。这些环流场及其不确定性的分析结果,进一步加强了我国夏季降水未来变化预估结果的可信度。更多还原

【Abstract】 Monthly data from climate change simulations using the 15 coupled climate system models in IPCC SRES A2,A1B,and B1 scenarios are analyzed for potential future changes in summer precipitation characteristics and its associated atmospheric circulation,and the uncertainties of these results from models are also investigated.The results demonstrate that the projected summer precipitation in China shows distinctly regional characteristics.The summer precipitation in the regions of eastern China and Tibetan Plateau are projected to significant increase in 21st century.These increasing linear trends and the models’ consistency are also intensified with the increase of air temperature,which indicates that the projections become much more believable in these regions.However,persistent decrease of summer precipitation is projected in south of Xinjiang region,and most models show decreased precipitation in the earlier period of 21st century and then increased in Southwest China.No obvious changes are projected in the other regions of China and the uncertainties are also large in these regions.The high confidence level of the multiple models ensemble results in IPCC three scenarios implies much more believable of the projected summer precipitation changes in China,with the larger projection in A2,then in A1B,and smaller in B1.Additionally,three "best" models that have the well performance in simulating the summer mean precipitation in China are selected and their projections show similar results with the 15 coupled models.Most models demonstrate that the East Asian summer monsoon will be significantly intensified under global warming,which induces more water vapor transport from the South China Sea and the tropical oceans.Thus,more water vapor content will be in the local region that provides a benefit background for the increasing summer precipitation in eastern China.Meanwhile,the western Pacific subtropical high is also projected to be significantly intensified and the impacts on the summer precipitation in eastern China are also obviously increased.These results from the analysis on the atmospheric circulation and its corresponding uncertainties of models further increase the confidence level of the projected summer precipitation change in China.更多还原