湘潭低空急流暴雨天气分型及雷达回波特征分析

Classification and Radar Echo Features of Low Level Jet Rain-Storms in Xiangtan City

利用常规气象观测资料、区域自动站、多普勒雷达等实况资料,分析了湘潭2011-2015年10次伴有低空急流的暴雨天气过程,归纳主要降水天气系统所对应的雷达回波特征。结果表明:低槽型急流暴雨常为S-N或NNE-SSW向的带状回波,前沿的强中尺度对流回波带易形成强对流天气,回波带的宽度窄,移动速度较快,难以出现成片的暴雨;冷式切变线型暴雨回波为E-W或ENE-WSW向的积层混合性带状回波,高仰角上存在零度层亮带,降水效率较高,以列车效应方式依次影响测站,几小时可达到暴雨量级,此类降水回波具有对流性;暖式切变线型暴雨以积层混合性带状回波形式出现,有时为块状、絮状,呈NE-SW或E-W走向,暴雨范围较低槽型和冷式切变型小,但强回波形成发展速度快,在极短的时间内可出现暴雨。

Based on the realistic data taken from conventional meteorological observations,regional automatic stations and Doppler radar,the rainstorm weather process in Xiangtan,Hunan Provice from 2011 to 2015 was analyzed,and the radar echo characteristics corresponding to the main precipitation weather system were summarized.Three types of rain-storm systems were classified and investigated.(1)The low-level jet with trough pattern often has a band-like echo of S-N or NNE-SSW.The strong mesoscale convective echoes in the front are easy to form strong convective weather.The width of the echo band is narrow and its moving speed is faster,and thus a sheet of torrential rain is difficult to appear.(2)The cold shear-line rainstorm has the cumulo-stratus mixed band echoof E-W or ENE-WSW.Such precipitation echo is convectiveand has melting-layer(0℃-layer bright band)at the high elevation angle.The rainstorms affect the stations in turn with a train-moving effect mode and with higher precipitation efficiency to achieve heavy rain in a few hours.(3)The warm shear-line rainstorm appears in the form of the cumulo-stratus mixed band-like echo,but sometimes blocky and flocculent,in NE-SW or E-W directions.Its range is usually smaller than that of the through pattern and the cold shear-line rain?storms,but the strong echo is formed and developed rapidly,and may result in heavy rain in a very short time.