风廓线雷达资料在乌鲁木齐一次大暴雪过程分析中的应用

利用常规观测、自动站逐时降水量、乌鲁木齐市风廓线雷达及ECMWF1°×1°再分析等资料,对2018年10月17—18日乌鲁木齐雨夹雪转大暴雪过程进行分析。结果表明,大暴雪是在低空西北气流与中高层西南急流叠加并维持的有利环流背景下,由700～850 hPa风切变、风速辐合、地面冷锋及地形强迫抬升等多尺度系统共同作用造成的。强降雪时雷达探测高度维持较高达7500 m,随着降雪结束探测高度明显降低。水平风场表明低空西北急流与中高层偏南急流形成的垂直风切变廓线的维持,是强降雪持续的动力条件。大气折射率结构常数C_n~2、垂直速度的大小与雨雪的开始、结束时间有较好的对应关系,且低层较强偏北风与C_n~2大值区相对应,降雪时低层垂直速度为0.8～1.2 m·s~(-1),雨或雨夹雪时垂直速度为1.8～2.5 m·s~(-1)。因此,水平风向风速、C_n~2和垂直速度的垂直变化对暴雪短临预报有很好的参考价值。

The Application of Wind Profile Radar products in A Rain and Snow Mixed to Heavy Snowfall in Urumqi

Using the wind profiler radar products in Urumqi, it analyzed a process of short-time drill to rain and snow mixed to heavy snowfall on October 17-18, 2018 in Urumqi. The results indicate: before the precipitation the detect height is lifted nearly 5km, the detect height obviously reduces at the end of the precipitation; The horizontal wind field showed that the cold air first wedged from the bottom and the warm air is forced to rise; There is a strong southwest jet stream download at high altitude, the southwest jet stream lasts during the rain and snow period, the high altitude rapid disappears at the snowfall end. The vertical velocity can not only reflect the beginning and end time of precipitation, but also reflect different phase state of precipitation. The atmospheric refractive index structure constant (CN2) shows the large value area corresponding to the snowfall period. It is visible that the wind profile radar data can not only reflect the evolution of the meso-and micro-scale system, but also reflect the characteristics of large-scale flow field changes, which can accurately capture the continuous atmospheric changes over the station. It has a high application value for short-term weather forecasting and catastrophic weather warning.