区域海气耦合模式对我国极端降水模拟分析

Analysis of Numerical Simulation on Extreme Precipitation in China Using a Coupled Regional Ocean-Atmosphere Model

使用区域海气耦合模式40年的降水模拟结果,采用百分位的方法定义极端降水事件,分析了耦合模式模拟的夏季中国极端降水事件的特征。结果表明,区域海气耦合模式基本能够模拟出气候平均极端降水阈值的空间分布型及极端降水事件在长江中游、西南部分地区和长江下游局部地区的显著增加、增强趋势,在中西部、华北北部和东北局部的显著减少、减弱趋势。EOF分析发现,模式模拟的极端降水事件几个特征量在我国江南地区长江以南与华南沿海及长江以北的呈反位相变化,这一变化以年代际为主要特征。区域耦合模式基本能够模拟出极端降水量、夏季总降水量、极端降水日数两两间的高时空相关关系。

Extreme weather and climate events have received more and more attention in recent years, due to the often large losses of human life as well as a tremendous increase in economic losses caused by them. Based on the 40-year （1958-1997） precipitation data simulated by a coupled regional ocean-atmosphere model system （P-σ RegCMg-POM）, by defining the 90th percentile as the threshold of extreme precipitation for each grid, the characteristics of the summer extreme precipitation events in China simulated by the model are studied. Results show that the coupled regional ocean-atmosphere model system has the ability to produce the spatial distribution of the climatic mean extreme precipitation threshold, which is characterized by several large value centers including south China, the Yangtze-Huaihe River valley, north and part of northeast China. Also the trends in the intensity and frequency of extreme precipitation are captured. The summer extreme precipitation and extreme precipitation days significantly increase in the middle reaches of Yangtze River, some parts of southwest China and the lower reaches of Yangtze River, and ＂decrease significantly in Midwest, some regions of north and northeast China. But they decrease in large part of the lower reaches of Yangtze River, which is opposite to the observational result. This may be caused by the difference in the peak values of the daily precipitation between the first few model years and the later years. Using the EOF （empirical orthogonal function） method, the temporal and spatial variation of the extreme precipitation events is studied. The first EOF pattern exhibits a main feature that the anomalies of the parameters of the extreme precipitation events over the areas south of Yangtze River are opposite to that over the coastal region of south China, and the areas north of Yangtze River; and this variation is featured as an interdecadal variation. While the second pattern shows that the anomalies over northwest and part of southwest China are opposite to that over other regions, and that it changes interannually. The time correlation and space correlation methods are used to investigate the ability of the coupled regional model to capture the properties of extreme precipitation. The analysis shows that the model can basically simulate well the closely correlated relation between each two of the extreme precipitation, the total rainfall in summer, and the extreme precipitation days.