云南省红河下游暴雨特征分析:以河口县为例

Analysis of rainstorm characteristics in the lower reaches of Honghe River in Yunnan province: Taking Hekou county as an example

云南省是暴雨多发的地区,但是由于气候条件、地理环境复杂,不同地区暴雨特征差异显著;因此,进行小区域的暴雨特征研究有助于预防暴雨灾害。红河下游的河口县是云南省6大暴雨中心之一,是暴雨多发区。本文基于河口县近年来177场暴雨数据,利用K-均值聚类方法研究了河口县暴雨雨型、特征以及暴雨危险性。结果表明:河口县暴雨具有明显的季节性,主要发生在4—9月,暴雨以P24(连续24 h降雨量> 50 mm的降雨)为主;河口县暴雨可分为前期降雨(Ⅰ)型、中期降雨(Ⅱ)型、后期降雨(Ⅲ)型、均匀降雨(Ⅳ)型4种雨型,其中前期降雨型的次数占暴雨总次数的2/3以上,是该地区主要的暴雨类型。该类暴雨历时以7～12 h为主,80%暴雨量和平均降雨强度较大值发生在前0. 4累计降雨历时内,即大概4 h以内,短历时强降雨危害较大,且多发生在夜间;因此需要引起高度重视。河口县暴雨黄色预警及以上级别的暴雨占暴雨预警总场次的80%左右,危险等级较高,可能会引起山洪、泥石流等灾害,应提前做好预防和治理措施。

[ Background ] Yunnan province is a storm-prone region. Due to the climatic and complex geographical environment, characteristics of rainstorm are various a lot in different regions. A study of the characteristics of the rainstorm in small region is helpful for the prevention of rainstorm damages. The lower reach of the Honghe River is located at Honghe region where rainstorms occur frequently. In addition, it is easy to cause flooding, landslides and debris flows and other geological disasters when amount of daily rainfall is over 25 mm. Hekou county is located in the lower reach of the Honghe River and is one of the six major rainstorm centers in Yunnan. This paper takes Hekou county as an example to study the characteristics of rainstorm types in this region.[ Methods ] Based on 177 rainstorms occurring in this region, K-means clustering was used to study type, characteristics and risk of rainstorms in Hekou county.[ Results ] The results show that the rainstorm is obviously seasonal, mainly from April to September, and dominated by P 24 in Hekou county. The types of rainstorms in Hekou county can be divided into four which are the previous rainfall (Ⅰ) type, medium-term rainfall (Ⅱ) type, late-rainfall (Ⅲ) type, and even rainfall (Ⅳ) type. The type Ⅰ accounts for more than 2/3 of the total rainstorm and is the main type of rainstorm in this area. 80% precipitation of rainstorm and the larger value of average rainfall intensity generally occur within the first 0.4 cumulative rainfall duration, the first 4 hours in a day. Since this type rainstorm will cause very serious damage, it should be paid highly attention to;According to the national grade of rainstorm warning, the rainstorms are dominated by orange and yellow warnings, which accounting for 42% and 32% of the total number of rainstorm warnings respectively. In this case, the risk of hazard level is higher, which may cause mountain torrents and mudslides in Hekou county. The warning and control measures of rainstorm should be made in advance.[ Conclusions ] This study discusses the characteristics of rainstorm in Hekou county, clarifies the types of rainstorm and duration, rainfall precipitation, rainfall intensity, warning level of each type, which are helpful to the prevention of rainstorm damages in this region.