云南降水的5个统计指标及其空间分布

利用云南29个气象站1960-2014年的日降水数据,计算集中指数(Concentration Index,CI)、降水集中指数(Precipitation Concentration Index,PCI)、降水集中度(Precipitation Concentration Degree,PCD)、降水集中期(Precipitation Concentration Period,PCP)、变差系数(Coefficient of Variation,CV)5个统计指标,分析了各指标之间的关系,并讨论了各指标的空间分布。结果表明:(1)CI介于0.62~0.71之间,平均为0.67,日降水高度集中。CI与年降水量、降水日数的相关系数分别为-0.50、-0.93,具有显著的负相关关系(α=0.05),年降水量和降水日数较少的地区,CI较大。CI与经度的相关系数为0.64,具有显著的正相关关系(α=0.05)。(2)PCI介于11.95~21.48之间,其中,3%的站点降水高度集中,52%的站点降水集中,45%的站点降水中度集中。PCD介于0.30~0.74之间,滇西北和滇东南地区的PCD较小。PCP的分析结果表明,云南降水主要集中在7、8月份。(3)CI和PCI、PCD分别关注降水的等级分布和集中程度,PCP则关注集中的时间段。PCI与PCD的空间分布情况基本上是一致的,且二者的相关系数为0.90,具有显著的正相关关系(α=0.05),故二者在一定程度上可以相互替换。采用CI、PCI和PCP 3种指标可以较好地描述降水的年内等级分布、集中程度和集中时段。(4)CV介于0.11~0.21之间,降水的年际变化随着纬度的减小、年降水量的增多呈减小的趋势,相关系数分别为0.39、-0.74;而年降水量随着海拔和纬度的升高呈下降的趋势,相关系数分别为-0.45、-0.53。

Five Statistical Indicators of Precipitation in Yunnan and Their Spatial Distribution

Based on the daily precipitation data of 29 meteorological stations in Yunnan from 1960 to 2014,five statistical indexes are calculated,including the Concentration Index(CI),Precipitation Concentration Index(PCI),Precipitation Concentration Degree(PCD),Precipitation Concentration Period(PCP)and Coefficient of Variation(CV).The relationship between each index is analyzed,and the spatial distribution of each index is discussed.The results show that①CI ranges from 0.62 to 0.71,with an average of 0.67,and the daily precipitation is highly concentrated.The correlation coefficients between CI and annual precipitation and precipitation days are-0.50 and-0.93,respectively,which have a significant negative correlation(α=0.05).CI is larger in areas with less annual precipitation and precipitation days.The correlation coefficient between CI and longitude is 0.64,which has a significant positive correlation(α=0.05).②PCI ranges from 11.95 to 21.48,in which 3%of the stations are highly concentrated,52%of the stations are concentrated,and 45%of the stations are moderately concentrated.PCD ranges from 0.30 and 0.74,and PCD in northwestern and southeastern Yunnan is smaller than that in other parts of Yunnan.The results of PCP analysis show that the precipitation in Yunnan is mainly concentrated in July and August.③CI,PCI and PCD pay attention to the grade distribution and concentration degree of precipitation respectively,while PCP pays attention to the period of concentration.The spatial distribution of PCI and PCD is basically the same,and the correlation coefficient between the two is 0.90,which has a significant positive correlation(α=0.05),so they can replace each other to some extent.The annual grade distribution,concentration degree and concentration period of precipitation can be well described by using CI,PCI and PCP.④CV is between 0.11 and 0.21,the interannual variation of precipitation decreases with the decrease in latitude and the increase in annual precipitation,the correlation coefficient are 0.39 and-0.74 respectively,while the annual precipitation decreases with the increase of elevation and latitude,the correlation coefficient are-0.45 and-0.53 respectively.