风廓线雷达和地基微波辐射计在冰雹天气监测中的应用

Monitoring Application of Hailstorm Event with the Observation of Wind Profile Radar and Ground-Based Microwave Radiometer

利用风廓线雷达和地基微波辐射计观测资料,对2010年4月12日发生在湖北咸宁的一次冰雹过程进行了分析,探讨这两种资料在冰雹天气监测预警中的应用。结果表明:(1)这次冰雹过程中,850~700 h Pa之间低槽约在降雹前1 h过境,850 h Pa以下低槽约在降雹前2 h过境。在降雹前约0.5h,0~4 km垂直速度大小随高度的波动明显增大。0~6 km始终存在较深厚的垂直风切变,每200 m高度的水平风垂直切变在2~2.5 km的正中心与冰雹发生相对应。(2)降雹前,0~10 km整层相对湿度垂直廓线大体呈5~10 km小、0~5 km大的"上干下湿"2层结构。降雹前约0.5 h,相对湿度呈"上下湿、中间干"的3层结构,大气液态水总含量ILW、大气水汽总含量IWV都呈波动快速增长,冰雹发生在ILW和IWV的波峰上。(3)在降雹前约6 h,K指数超过35℃,在降雹前CAPE平均值约为627 J·kg-1,0℃,-10℃和-20℃层高度分别在5 km、6 km和7.5 km。

The evolution characteristics of hail potential conditions,such as mesoscale weather system,wind shear,w ater vapor,vertical velocity and unstable stratification at Xianning City in Hubei Province on 12 April2010 w ere analyzed with wind profiler radar data and ground- based microw ave radiometer that w ere applied to monitoring of hail fall process. Results show that:( 1) The hail- fall process initiated during the process of low trough moving eastw ardly and cold air moving southw ardly. The mesoscale weather system such as southw est jet at middle and low levels,the shear line on 850 h Pa,moist tongue and cold front at the ground afforded dynamic,thermal and w ater vapor conditions. The deep vertical wind shear from 0 to 6 km and the zero elevation at 3. 5km afforded circumstance condition for hail fall.( 2) The passage of the low trough betw een 850 h Pa and 700 h Pa is about 0. 5 hour earlier than hail- fall process. And the influence of the cold front near the ground w as 2 hours earlier than low trough on 850 h Pa. And the temperature advection betw een 1400 m to 5000 m changed from positive to zero,then to negative. The w arm and w et flow follow ed air of higher temperature and greater humidity. Cold advection at middle level w as beneficial to the development of convectively un- stability.( 3) The fluctuation of vertical velocity increased with the height from 0 to 4 km 0. 5 hour earlier of hail fall process. The maximum vertical velocity difference could reach 11 m ·s- 1. It show s that the thermal and dynamical structure in the atmosphere w ere very different at different level at the convective storm.( 4) There existed deep wind shear at the vertical direction all the time from 0 km to 6 km before hail fall. And it w as positive and stable calculated every 200 m. At the same time,the maximum appeared about 1. 5 hour earlier w hich w as significant to the monitoring and prediction of hail- fall.( 5) The relative humidity w as less and drier betw een 5 km to 10 km w hile it w as greater and w etter betw een 0 km to 5 km before the hail-fall process. It show ed three- layer distribution of 'w et at high and low levels,dry at middle level'. ILW and IWV increased rapidly from 4 mm to about 15 mm and from 40 mm to more than 60 mm respectively. When ILW and IWV reached maximum,the hail- fall initiated.( 6) The K index exceeded 35℃ about 6 hours earlier than hail- fall process. The averaged value of CAPE w as about 627 J·kg- 1before hail- fall process. Heights of 0℃,- 10℃ and- 20℃ w ere at 5km,6 km,7. 5 km respectively. The indexes evolution could show the unstability of atmospheric stratification to some extent.