Analysis of Precipitation Characteristics and Its Causes in Central Yunnan City

HE Ping, LI Jinxiao, FU Yongmei, et al

Abstract Basing on the nearly 50-year precipitation data of 4 major city (Kunming, Qujing, Yuxi, Chuxiong) in urban agglomeration of central Yunnan, this paper analyzes the variation of precipitation in annual, seasonal, and monthly time scale by using methods including the statistical analysis, the wavelet analysis, accumulative leveling method, and the grey relational analysis. The result shows that the average precipitation in past 50 years is 928.1 mm. The trend of precipitation is declining, and a mutation appears in 2009. Besides, precipitation has a dry and wet season in these region, and the wet season is between May and October but the dry season is between November and April of next year, There are more precipitation in the rainy season and less precipitation in dry season. The maximum of precipitation (184.0 mm) appears in July, but the minimum of precipitation (13.8 mm) appears in December. According to the wavelet analysis, the change of annual precipitation is about 22 years, the summer precipitation has a 19-day increase-decrease cycle with more precipitation and smaller variation, and the winter precipitation has a 20-day increase-decrease cycle with less precipitation and larger variation. The grey relational analysis show that the temperature and the specific humidity are dominant natural factors, and the population and the city size are dominant human factors. Besides, the natural factors play greater role than the artificial factors. Key words central Yunnan city; precipitation characteristics; grey relational analysis; natural factor; human factor