Stability of Precipitation Resources in Huang-Huai-Hai River Area and Its Surrounding Area

Based on the 1951—1982 monthly and daily precipitation data at 43 stations, the three indices, i. e. mean anomaly percentage, mean interannual change percentage, and mean anomalies of mean interval days with daily precipitation greater than 5, 10 and 20 mm, are presented to study the stability of precipitation resources in Huang-Huai-Hai river area and its surrounding area. It can be divided into three types: northern, southern and southwestern. Meanwhile, the characteristics of the stability in temporal and spatial distributions are also discussed for each type and each season