Study On Spatial-temporal Characteristics And Trend Of Extreme Rainfall In The Jianghuai Region

Based on the daily precipitation data for 72 effective meteorological stations from 1960~2014 in the Jianghuai Region,and selects 10 extreme precipitation indexes,using inverse distance weighted interpolation,anomaly and cumulative anomaly,5 years moving average,climate trend rate,correlation coefficient,Mann-Kendall and other analytical methods,makes a detailed analysis of the spatial distribution characteristics,time series variation characteristics and trend changes about Jianghuai Region in the past half century.The results indicate that:(1)The annual,seasonal and interdecadal spatial distribution of the extreme precipitation indexes in Jianghuai Region are obviously difference,and most of the indexes follows the stepwise decreasing from Southeast to Northwest.The high value areas of annual,seasonal and interdecadal space of most of the indexes are all in the northeast of Jiangxi and the south of Mount Huangshan in Anhui,while the south area of Huai River basin is not only located in the low value area in the most of indexes' spatial distribution,but also the annual drought is longer than a month.However,in the 00 years of twenty-first Century,the precipitation intensity of Huai River basin was abnormal,and its precipitation intensity was as high as 15.45mm/d.The extreme heavy rainfall(R95p?RX1day?RX3day)in the southeastern coastal area of Zhejiang Province is more abundant,and most of indexes in autumn are all in the high value areas.The trend spatial distribution of the indexes in Jianghuai Region is significant different,and the distribution of positive and negative sites is also difference.The sites of SDII with rising trend change(65)and those with passing the significance test(19)are the most,and the southeast coastal region is still located in the positive and high value area in the trend spatial distribution of most indexes.Every index is greatly influenced by meridian and latitude,and the best correlation with latitude which all passed 99% correlation test.Every index has a good indicator for the extreme precipitation in the Jianghuai Region's spacial,and except for CDD,the other indexes are all positively correlated with PT(p<0.01).(2)The inter-annual variation of the indexes in the Jianghuai Region are obvious,each index has one or more abnormal years about anomaly.In 1978,multiple indices showed negative anomalies and annual minimums.In the curve of 5 years moving average,index changes are mostly in 2a cycles.Multiple indices(except R10,CWD,and CDD)had a mutation in 1961 and appeared a trough in 1978.The interdecadal characteristics of the indexes are different,but overall,the age value of highest and lowest,the annual value of maximum and minimum,which were respectively appear in the 90 s and the 70s;In the trend change,the trend of R10,CWD and CDD was not significantly reduced,while the other indexes showed an increasing trend,and the indexes of R95 p,R50 and SDII not only showed a significantly increasing trend(p<0.05),but also passed the 95% significance test of MK after the mid-90 s.During the year,most of the indexes(except CWD and CDD)showed a single peak change at the peak of June,while the bimodal distribution of CWD and CDD which their peaks respectively appeared in March,June and December,January.In all indexes,the duration indexes are more uniform,while the other indexes are significant differences in the distribution during the year.The R50 and R95 p are the main types in June and September,and R10 is the main sources in October and March,R20 is the main source in April and May.The distribution of extreme precipitation in the four seasons is extremely uneven.The abundance and duration of extreme precipitation are mainly concentrated in the summer,among them,the summer extreme precipitation of R50 and R95 p accounted for more than 60% of the whole year.While the winter is not only relatively dry,but also the CDD are long,moreover the autumn and winter show a tendency of persistent drought intensification.In addition,extreme precipitation indexes all showed a downward trend in autumn,and in spring,they also showed a downward trend except for R50 and CDD,overall,extreme precipitation in spring and autumn showed a decreasing trend.