影响伊犁河谷地区冬季降水的主要气象要素 及其与降水率的统计关系

基于2014—2018年逐时降水资料和再分析资料分析了影响伊犁河谷地区冬季降水的主要气象要素及其与降水率的统计关系。结果表明,水汽通量是影响伊犁河谷冬季降水的最主要因素,其与降水率呈正相关;上游风速、水汽通量、弗劳德数和大气可降水量都会对该地区降水产生影响,这四个参数可以通过依赖于水汽通量的多元回归较好地拟合出降水率;静力稳定度与该地区降水没有明显统计关系,但较强的降水更多出现在稳定度较弱的天气;利用T模态斜交主成分分析法将伊犁河谷天气系统分为九类,在有降水时,出现频率较高的天气类型的主要特征是水汽通量大,但不同天气类型下降水空间分布存在区别。当河谷上游气压较低,水汽通量较大时,河谷内降水分布较为均匀;若河谷上游风速较大,但水汽条件略差时,降水强度向河谷内部逐渐增加。

Meteorological factors influencing wintertime precipitation in the Ili River Valley and their statistical correlation with precipitation rate

Using hourly precipitation data and reanalysis data from 2014 to 2018, the meteorological factors influencing wintertime precipitation in the Ili River Valley their statistical correlation with precipitation rate are analyzed. The results show that the vapor flux, which is positively correlated with the precipitation rate, is the major factor that controlling the precipitation in the Ili River Valley. All of the upstream wind speed, vapor flux, Froude number and precipitable water are found to have impacts on the precipitation over the downstream region, and these four parameters can be used to fit the precipitation rate by using a multiple regression in terms of vapor flux. Even though strong precipitation is usually observed in existence with low stability, no obvious statistical relationship between the static stability and precipitation rate is found. The local weather systems are classified into nine types by using T-modal oblique principal component analysis. The main feature of the weather types with higher precipitation occurrence is the large vapor flux, however, the spatial distribution of precipitation varies for different weather types. A relatively uniform distribution of precipitation can be seen if the local weather condition is controlled by low pressure and large vapor flux, and the intensity of precipitation will gradually increases towards the interior of the valley if the weather condition is controlled by strong wind and the relatively low vapor mixing ratio.