Variation in Precipitation for Hexi Region Over 52 Years
河西地区1960年至2011年不同级别降水日数和极端降水事件的变化特征

Located in semiarid northwestern China, and far from any ocean, Hexi belongs to the typical continental climate zone. All kinds of weather conditions can be frequently experienced there, especially extreme precipitation. Socio-economic development, human health and the natural environment have become vulnerable to extreme precipitation events in Hexi. Based on daily precipitation data from 1960 to 2009 at 13 meteorological stations across Hexi, regression analysis, inverse distance weighted, Mann-Kendall, sliding average, correlation analysis, Morlet wavelet analysis and R/S analysis were employed to analyze spatial and temporal variability, and future patterns, of rainy days and extreme precipitation events. We found that drizzle days have decreased and light rain days have increased. Very wet day precipitation, extremely wet day precipitation, annual maximum with 1-day and 5-day precipitation all increased at rates of 3.12, 1.39, 0.505 and 0.868, respectively. Annual total precipitation and precipitation extremes are correlated. Extreme precipitation indices show abrupt change at the 0.05 level. Mutations of extreme precipitation events took place in 1966, and changes increased in tendency after 1966. Different vibration periods were displayed very clearly in extreme precipitation indices and reflects different structures which are more or less in different time scales. Differences in spatial distribution still exist, especially in the southeast where the range of change is largest; the monsoon was the major reason for this change. The Hurst index shows that future light snow days (increasing) and future drizzle days (decreasing) are an obvious trend; future extreme precipitation events showed no obvious future trend.