川北绵阳地区降水量的时空分布特征及变化趋势

选用四川省绵阳地区8个台站1959~2005年日降水资料,采用经验正交函数分解法和连续功率谱分析等方法分析了绵阳地区年降水量的时空分布特征及变化趋势,结果表明,绵阳地区年降水量的空间分布不均匀,局地差异大,主要表现为3种分布型:①区域一致型;②东南—西北型;③中部型。绵阳地区的年降水量呈整体下降趋势,但降水剧烈程度加大,同时东南—西北分布型在加剧;功率谱分析发现,绵阳年降水量的变化具有2.9年和6.7年的显著变化周期;绵阳地区各站的年降水和不同等级降水的降水量和降水日数大致呈不同程度的下降趋势和减少趋势,但不同站点暴雨以上量级的降水量和降水日数变化特征又有所不同;绵阳地区区域平均年降水量呈减少趋势主要是由于雨季降水量和降水日数均出现减少趋势造成的。

Spatial and Temporal Distribution Characteristics and Variation Tendency of Precipitation in Mianyang

Daily precipitation data of 8 stations during the period of 1959-2005 in Mianyang of Sichuan province is used.Empirical orthogonal function and continuous power spectrum method are used to analyze the spatial and temporal distribution and variation tendency of precipitation in Mianyang.The result indicates that the spatial distribution of annual precipitation in Mianyang is not uniform and the local difference is obvious.The spatial distribution can be described as three types:①regional consistent type;②southeast-northwest type;③central type.The annual precipitation shows a decreased tendency all over Mianyang, but the precipitation intensity has increased, and the southeast-northwest type has expanded.The result of power spectrum analysis indicates that the variation of annual precipitation in Mianyang has a significant cycle of 2.9 years and 6.7 years.In addition, annual precipitation and precipitation of different magnitude and days of precipitation at each station in Mianyang also have a declined tendency.However, the characteristics of precipitation and days of precipitation over the storm rainfall of different station are different.The decline tendency of both precipitation and the days of precipitation in wet season is the major cause of the decline tendency of annual precipitation.