Radar Observation Study on the Evolution Characteristics of Hail Cloud in Weining,Guizhou Province
Based on two hailstorm processes on May 17,2018 and April 27,2019,combined with the radar echo evolution characteristics of the single hail-cloud cells,the characteristics of the polarization parameters such as Zh,Zdr,φdp,and ρhv of the single hail_cloud cells are analyzed.Moreover,the corresponding relationship between the distribution of precipitation particles in different phases and the ambient condition of temperature formation are also investigated.The analysis results show that:(1)If the 45 dBz echo height is above the 0 ℃ layer height,the echo intensity Z≥55 dBz and VIL≥20 kg·m-2 are used as hail identification indicators,the body scanning observation time will be 1～3 times earlier than the hail fallout time and the advance of hail warning time is 6～18 minutes.(2)The Zdr of the non-spherical large particle area is between 2.8～5.4 dB,φdp is between 179～191°and ρhv is between 0.85～0.99,which corresponds to the strong echo area where there are mainly large raindrop particles.The Zdr of the approximately spherical large particle area is between-2.3～1.2 dB,φdp is between 180～235° and ρhv is between 0.54～0.90,with spherical particles such as graupel or hail mainly distributed.(3)When approximately spherical particles(hail)are located on the front side of non-spherical particles(raindrops)and there are positive and negative central areas of Zdr,the drag effects of wind direction and speed make the large raindrop cluster move slowly while graupel or small hails move faster in the direction of the wind,which is the result of their staying at the front of the strong echo zone.(4)The particle identification and classification algorithm in this study does not consider the temperature and ambient conditions of hydrometeor particles,so there exist solid precipitation particles such as wet snow(WS)and ice crystals(CR)in warm clouds,and there is a lack of graupel particle classification and identification products.Therefore,the hydrometeor particle classification and identification algorithm needs to be improved.
hail cloudevolution characteristicspolarization parametersparticle identificationwarning time
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万方数据
