滇西北局地小冰雹天气分析

ANALYSIS OF LOCAL SMALL HAILSTORM WEATHER IN NORTHWEST YUNNAN

利用NCEP再分析资料和大理多普勒雷达资料对比分析滇西北地区7次局地小冰雹过程的天气背景和雷达产品特征。分析结果表明:小冰雹过程受低压系统影响,多数发生在午后,持续时间短;有较有利的热力条件、不稳定条件和动力条件;冰雹出现时雷达反射率因子一般达50dBz以上,回波顶高达13km以上,45dBz的强回波高度达7km,具有穹窿结构,径向速度低层辐合高层辐散、中层逆风区,但是回波持续时间短,变化较快,面积较小,突发性强。

Using the NCEP reanalysis and Doppler radar data of Dali to compare and analyze the weather background and radar product characteristics of seven local small hailstorm processes in northwest Yunnan.The results show that the processes are affected by the low-pressure system.Most of them occur in the afternoon and of short duration.The small hailstorm processes have favorable thermal conditions,unstable conditions and dynamic conditions.In small hailstorm weather,radar reflectivity factor generally reaches above 50 dBz,and echo top reaches above 13 km.The strong echo height of 45 dBz reaches above 7 km.The dome structure has subsistent.The radial velocity of the low layer is convergent as well as divergent in the high layer.The strong echo center of the middle layer has an upwind zone.But the echo is shorter duration,faster changes,smaller area and stronger sudden.