未来半个世纪江淮流域夏季降水变化趋势的数值模拟结果分析

基于政府间气候变化委员会(IPCC)排放情景特别报告(SRES)A2和B2温室气体排放方案下全球海气耦合模式模拟结果,分析了未来半个世纪中国江淮流域夏季降水变化趋势,发现江淮流域在经历21世纪开始10年降水偏多时期后,从2010年开始该地区将经历一段降水偏少的时期,在温室气体和SO2排放量较多的A2方案下,该时期将维持较长时间.这些地区夏季降水的减少与夏季西北太平洋副热带高压环流的减弱东撤有关,由此伴随这些地区夏季风和对流层中大气上升运动的减弱,而西北太平洋副热带高压环流的减弱东撤与北太平洋海表面南高北低的温度梯度的减小有关.

A Numerical Study of Summer Precipitation in the Changjiang River and the Huaihe River Valleys Within Coming Half Century

The precipitation change in the future over the Changjiang River and the Huaihe River valleys of China in response to the global climate change has been of great concern.However the results from different research would be controversial.Different model used and different scenarios of greenhouse gas concerned would lead to different conclusions.In this study,based on the output of the GFDL R30 coupled climate model under the latest scenarios forcing of A2 and B2 released by the United Nation's Intergovernmental Panel on Climate Change(IPCC) Special Report on Emission Scenarios(SRES),the simulated current climatological state of precipitation over the Changjiang River and the Huaihe River valleys and the general circulation over East Asia and northern West Pacific are proved reasonable,and then the long-term trend of precipitation in the Changjiang River and the Huaihe River valleys within coming half century are assessed.It is revealed that after experiencing more precipitation in the first ten years of this century,there will be a long period with less precipitation in summer over this area after the year of 2010.The range of this period will be longer till the end of the 2050s of this century with a normal state period in the 2020s under the A2 scenario in which there is more greenhouse gas and SO_(2)extricated into atmosphere.Comparatively,a less precipitation period will end at the middle 2020s under the B2 scenario with less greenhouse gas and SO_(2)extricated into atmosphere.The reduced precipitation over this area results from the weaker and eastward retreating subtropical high over the northern West Pacific in summer,accompanying by weaker summer monsoon and weaker upward motion of air in the troposphere.The weakening and eastward retreating subtropical high is related to the decreasing of sea surface temperature gradient between the tropical and middle-latitude North Pacific.