杭州短时强降水特征分析及预报研究

The Analysis of Short-time Hard Rain Characteristics and Its Prediction Methods Study in Hangzhou

利用杭州市近20年的1h雨量资料,分析了杭州短时强降水的发生规律,包括短时强降水的极值分布、年发生次数、月际分布、时段分布等气候特征。短时强降水雨量极值大多出现在台汛期间。杭州市短时强降水年发生次数的多年平均值为9.6次。杭州发生短时强降水的高峰期为7～8月。短时强降水容易发生在凌晨及午后两个时段。产生短时强降水的天气系统有:梅雨锋、西风带低槽、热带气旋、副高边缘西风急流、局地强对流系统等。本研究通过MM5模式产品得到各大气对流参数场及单点探空曲线,为预报短时强降水提供了新的思路。通过个例分析发现,在强对流天气发生前,各个大气对流参数场中心与短时强降水中心对应较好,杭州探空曲线反映了大气层结不稳定,有利于强对流天气发生。但是预报仅停留在定性和人工分析阶段,做出客观定量预报,并确定短时强降水的落区还有待进一步研究。

Nearly twenty-year one-hour rainfall data in Hangzhou are analyzed in this article. Some useful conclusions are obtained. These conclusions are about the regularity of the short-time hard rain occurrence including the extreme value distribution,yearly mean occurring times,monthly distribution ,hourly distribution and other climatical characteris- tics. The extreme value of the short-time hard rain mostly takes place during the typhoon influencing period . The yearly mean occurring times is 9.6. It is mostly inclined to accur in July and August. There are two pieces of highly occurring period in a day , which are wee hours and afternoon. The front during the plum rains period, the trough in the westerlies, tropical cyclone ,the west jet stream anear the subtropical high and the local convective system all can activize short-time hard rain. The thermodynamic and kinematic severe weather parameters and the SkewT-logp plot are obtained through the outputs of mm5. This can provided some new methods for predicting the short-time hard rain. Several examples are analyzed. And we find that before the severe weather happen, the centers of each parameter field are well corresponding with the center of the short-time hard rain. And the skew-T thermodynamic diagram reflects the unsteadibility of atmo- spheric layer upon Hangzhou. Some signs indicate that the severe weather will occur in the near future. But the prediction is only settled in the period of qualitative and manual phrase. More study is needed to get objective , automatic prediction.