Characteristics of Spatial Temporal Variation of Abrupt Alternation of Drought and Flood in Guizhou Province during Midsummer from 1981 to 2017

In order to objectively judge the abrupt of drought and flood in Guizhou Province during midsummer,using the monthly precipitation data of 78 stations in Guizhou Province from 1981 to 2017 to calculate and analyze the characteristics of spatial temporal variation of abrupt alternation of drought-flood abrupt alternation index. The results show that the changing trend of drought-flood abrupt alternation index in Guizhou Province from 1981 to 2017 is not obvious,but the interdecadal change characteristics are obvious. Using the drought-flood abrupt alternation index alone to determine the typical year is not completely accurate. The definition standard of the typical year of drought-flood abrupt alternation is: the absolute value of drought-flood abrupt alternation index is greater than 1,and the absolute value of the precipitation anomaly percentage in July and August is above 15%,and the absolute value of the percentage difference between July and August is above 50%. The large-value areas of the frequency of flood to drought abrupt alternation are located in the south of Zunyi and the north of Qiandongnan,which indicating that the area is prone to flood to drought abrupt alternation events. And the large-value areas of the frequency of drought to flood abrupt alternation are located in the north of Zunyi and the east of Anshun and the north of Qiandongnan,which indicating that the area is prone to drought to flood abrupt alternation events.