武威市雨日的变化趋势及特征分析

为了更好地开发利用气候资源，合理指导各行业生产，科学利用水资源和保护生态环境，利用1961—2013年武威市5个观测站的逐日降水资料，运用线性趋势系数法系统分析武威市雨日的时空分布特征。结果表明：武威市年总雨日及各量级雨日的空间分布从西南向东北呈递减趋势。武威市月雨日的变化比较一致，高峰值在7月，低谷值在11—12月；除古浪外，全市及各地各季节雨日总体上呈减少趋势。年及年代雨日也呈减少趋势，年雨日时间序列存在4~5年的准周期变化。小雨是武威市降水的主体，小雨日出现的几率占总雨日的92.7%~96.9%，随着降雨量级的增大，雨日迅速减少。雨量为 0.0 mm的小雨日均呈减少趋势，雨量大于0.0 mm的小雨日和雨量大于10.0 mm的中雨及以上的降雨日全市及各地变化趋势不太一致。

Variation Trend and Characteristic Analysis of Rain Days in Wuwei City

The paper aims to better develop and use climate resources, reasonably guide the production of various industries and scientifically use water resources and protect ecological environment. Using daily precipitation data of 5 meteorological stations in Wuwei City during 1961-2013, space-time distribution characteristics on rain days were systematically analyzed with linear trend coefficient method. The result showed that: space distributions of annual and various magnitudes rain days had a trend of decreasing from the southwest to the northeast in Wuwei City. Monthly variation of rain days was more consistent, one obvious peak was in July and one obvious trough was in November to December. Rain days of various regions of Wuwei except Gulang had a decreasing trend in all four seasons. Rain days of the year and time also had a decreasing trend, time series of annual rain days had 4-5 years quasi-periodic variation. Light rain was the main form of precipitation in Wuwei City, and it probability was 92.7% to 96.9% of the total rain days. Rain days decreased rapidly with the increasing of rainfall magnitude. Light rain days of rainfall 0.0 mm all had a decreasing trend. Variation trends of light rain days of rainfall more than 0.0 mm and rain days of rainfall over 10.0 mm were inconsistent in the whole city and various regions.