我国西南地区1963年-2012年降水集中指数的变化特征

Characteristics of Precipitation Concentration Index Variations in Southwest China from 1963 to 2012

本文选取1963年-2012年我国西南地区102个站点的日降水资料,计算了各站点50年降水集中指数(Precipitation Concentration Index,PCI),分析了西南地区PCI变化趋势及时空分布特征.结果表明:西南地区的PCI大值分布在西南-东北一线,逐渐向西北、东南递减,川东北和四川盆地降水集中最明显;西南地区西北部的PCI值50年内呈下降趋势,东部和南部呈上升趋势,西南地区PCI大值区的范围在扩大,川东北降水集中趋势最明显;西南地区降水量总体呈减少趋势,在降水集中度增大的同时,旱涝灾害风险也增大,这一变化特征自本世纪以来尤为突出;PCI和PCI距平的空间分布都存在明显的年代际变化特征,西南地区60年代、70年代、80年代和90年代、本世纪初的PCI距平总体呈正-负-正-负的变化.典型站点巴中年降水量和PCI均增大,与近年来洪涝灾害多发相吻合.

Based on the daily precipitation data at 102 stations from 1963 to 2012in southwest regions of China,the PCI of each station in the past 50 years was calculated.Besides,the variation tendency and the time-space distribution features of PCI at southwest regions were analyzed.The results indicate that,the maximum value of PCI in southwest regions distributed from southwest to northeast and decreased progressively toward the northwest and southeast.Precipitation in Northeast of Sichuan and Sichuan basin was the most obvious.The PCI of northwest in southwest regions was on a declining curve during 50 years,while the PCI of east and south areas was on the increase.In the southwest region,the range of the PCI maximum value was enlarged,and in the northeast of Sichuan province,the precipitation concentration trend is the most obvious.The overall trend of precipitation in the southeast was decreasing.The precipitation concentration degree was increasing,as the same time the more risk of drought and flood disaster took place.And this characteristic of PCI variation was particularly prominent in this century.The space distribution of PCI and PCI anomaly shows an obvious inter-decadal variation characteristic.The variation of PCI anomaly experiences positive-negative-positive-negative process from the sixties to early this century.Annual precipitation and PCI value were enlarged in Bazhong which was one of typical stations,corresponding to frequent flood disasters in the recent years.