江南区域性极端降水长期变化及其可能原因

Long-term Variation of Regional Extreme Precipitation in Jiangnan Area and Its Possible Cause

基于1961~2018年中国地面降水日值0.5°×0.5°格点数据集(V2.0)、NCEP/NCAR再分析数据及中国气象局上海台风研究所(CMA-STI)提供的热带气旋(TC)最佳路径资料,通过百分位阈值法确定江南区域性极端降水事件并根据天气系统对其进行综合分析而归类,结合线性趋势分析、M-K突变检验等方法,分析江南地区不同类型极端降水的长期变化及其可能原因。结果表明:(1)江南地区在1961~2018年间共有790次区域性极端降水事件,包含436次锋面型极端降水事件、135次气旋型极端降水事件和219次其他类型极端降水事件。(2)除其他类型极端降水事件的降水天数、降水量呈下降趋势之外,锋面型和气旋型极端降水事件都呈上升趋势,并且其降水天数、降水量显著上升。所有类型的极端降水强度都呈上升趋势。区域性极端降水天数、极端降水量的增长趋势开始时间晚于锋面型,但其极端降水天数与锋面型同在90年代左右发生突变,极端降水量与气旋型同在80年代左右发生突变。(3)区域性极端降水事件的变化可能是由锋面型、气旋型极端降水事件的变化而导致,而局地经向环流、出现在江南地区的热带气旋数量分别是锋面型与气旋型极端降水事件长期变化的可能原因。

In this paper,the daily precipitation dataset of grid points(0.5°×0.5°)of version 2 during 1961~2018 from China Meteorological Administration,daily reanalysis dataset from NCEP/NCAR and the tropical cyclone(TC)database that’s from the Shanghai Typhoon Institute of China Meteorological Administration(CMA-STI),were used to analyze long-term variation of the regional extreme precipitation and its possible cause in Jiangnan Area.The regional extreme precipitation events were determined by the percentile threshold method and classified according to their weather systems.Then,the linear trend analysis,M-K mutation test and Spearman correlation analysis methods were used for the analysis of the long-term variation of regional extreme precipitation events.The results are as follows:(1)There were 790 regional extreme precipitation events in Jiangnan Area from 1961 to 2018,including 436 frontal extreme precipitation events,135 cyclonic extreme precipitation events and 219 other types of extreme precipitation events.(2)Frontal and cyclonic extreme precipitation events both show an upward trend,and the precipitation days and precipitation amount of them significantly increased.The intensity of all types of extreme precipitation events all had been an upward trend.However,the precipitation days and precipitation amount of other types of regional extreme precipitation events show an downward trend.The upward trend of precipitation days and precipitation amount of regional extreme precipitation events started later than those of frontal type,but the extreme precipitation days of them changed suddenly around in the 1990 s,and the extreme precipitation amount of regional and cyclonic changed suddenly around in the 1980 s.(3)The variation of regional extreme precipitation events may be caused by the variation of frontal and cyclonic extreme precipitation events,while the local meridional circulation and the number of tropic cyclone appearing in the Jiangnan Area are the possible reasons for the long-term variation of frontal and cyclonic extreme precipitation events respectively.