基于阈值方法原理的江淮地区降水特性研究

Characteristic Analysis of Precipitation over Yangtze-Huaihe Region Based on Threshold Method

利用江淮地区20个代表站点雨量计连续30年(1980—2009年)的逐日降水资料,基于阈值方法原理对该地区降水特性进行了研究,主要讨论了月平均日降水量与阈值为0.1,1.0,5.0,10.0,24.0,48.0mm/d时降水日数占该月天数比例之间的关系。研究结果表明:各站点及江淮整体月平均日降水量与超过某一阈值降水日数占该月天数的比例之间存在着高度的线性相关关系,相关性随着阈值的不同而变化,在阈值为24.0mm/d时相关性最好,相关系数普遍超过0.97。低阈值时存在着非线性相关。阈值方法具有很多方面的应用,例如能更好地理解降水的形成机制;寻求更好的估测降水的算法;发展更优的数值预报模式的参数化方案;检验各种数值预报模式降水产品等。

Based on the principle of threshold method with daily precipitation data from 1980to 2009, observed by 20 rain gauges over the Yangtze-Huaihe region,a investigation is conducted on the characteristics of precipitation over the Yangtze-Huaihe region,with emphasis on the highly correlative relation between the monthly mean daily rainfall and the ratio of the number of rainy days with rainfall exceeding a certain threshold to the number of days of the month when the rainfall thresholds being 0.1, 1.0,5.0,10.0,24.0,and 48.0mm/d,respectively.A high correlation is found between the monthly mean daily rainfall and the ratio of the number of rainy days with rainfall exceeding a certain threshold to the number of days of the month.The correlation coefficient varies with rainfall thresholds,higher than 0.97for all 20stations,peaking at a threshold of 24.0mm/d.The rain rate and fractional rain day were nonlinearly related at low rain-rate thresholds.The threshold method can be applied widely,for examples, to achieve a better understanding of the forming mechanics of precipitation,to seek better algorithms for the estimation of precipitation,to develop better parameterization schemes for numerical forecasting models,and to validate the outputs of various numerical weather models,and so on.