Abstract:
Based on the daily meteorological data from 8 representative weather stations in the middle of Shandong province during 1980 to 2014,a cumulative frequency method was adopted to correct the thresholds of five drought indices.The temporal-spatial variation characteristics of drought and the applicability of each drought index in the studied area were analyzed.The results show that mean annual drought days calculated using the five indexes are about 92 to 106 days.It has a decreasing trend with decadal decreasing rates ranging between 2 and 6 days per decade.The center of drought area is located in the middle part of the central Shandong province.The compound drought index is the best indicator among the five indices for recognizing severe and long-duration drought years.The suitable drought index varies with seasons in the research area.Drought days in spring,summer and winter are declining during the 35 years and spatial change characteristics of drought days are different among four seasons.In addition,the most and the least droughts occurs respectively in May and August.Annual pattern of monthly drought days appears to be an approximate cosine rule.Besides,the drought indices which work most effectively in recognizing drought days vary from one month to another.