未来全球气候变暖情景下华东地区极端降水变化的数值模拟研究

将公用气候系统模式与区域气候模式单向嵌套(CCSM3-RegCM3),分别对1950—1999年和2000—2099年进行大气温室气体中等排放情景(A1B)下中国区域高分辨率连续数值模拟试验,以分析其对我国华东降水量时空变化的模拟能力,探讨未来华东地区极端降水的可能变化。与CRU、CMAP实际降水观测及NCEP再分析资料驱动的RegCM3模拟结果的对比显示,模式系统较好地重现了我国华东降水水平分布、日变化以及极端降水指数变化特征。在此基础上,分析了A1B情景下21世纪中期和后期降水以及东亚夏季风的可能变化。(1)未来中国长江中下游及其以北地区降水普遍增加,以南沿海地区降水相对变化不明显甚至减少,21世纪末期相对21世纪中期更为明显;(2)极端降水指数显示未来长江中下游及其以北地区极端降水增加10%～15%,干旱程度减弱,而南部沿海地区小范围极端降水减少,最大持续无雨期天数增加最大可达30%;(3)未来东亚夏季风偏强,尤其是西南气流加强,致使夏季风明显北推,这是导致长江中下游及其以北地区降水显著增加的主要原因。

NUMERICAL SIMULATIONS OF EXTREME PRECIPITATION IN EASTERN CHINA UNDER A1B SCENARIO

The regional climate model(RegCM3) developed by the Abdus Salam International Centre for Theoretical Physics(ICTP) nested in one-way mode within the latest version of Community Climate System Model(CCSM3) from the National Center for Atmospheric Research(NCAR) is used to conduct a set of experiments to examine its capability of climate simulation for the past 50 years and to explore possible changes in extreme precipitation(EP) the next 100 years under the A1B scenario.Compared with the observation from the Climate Research Unit(CRU) at the University of East Anglia and CPC Merged Analysis of Precipitation(CMAP),RegCM3 reasonably reproduces the spatiotemporal distributions of precipitation and EP in eastern China.Based on the present-day analysis,this study examines the changes in monsoonal precipitation over eastern China in mid-and-late 21st century relative to the reference period of 1970—1999.It is found that the precipitation will increase over the middle and lower reaches of the Yangtze river and areas to its north,and decrease over coastal areas to its south,especially in late-21st century.The various indices reflecting extreme events showed that the EP will enhance 10%～15% over the middle and lower reaches of the Yangtze River and areas to its north,and weaken over the areas to its south.The summer monsoon will strengthen and shift northwards e under SERS A1B,bringing more water vapor and energy from the Indian Ocean and South China Sea for precipitation and eventually more precipitation over northern China.