青海东部一次强冰雹的微结构及生长机制研究

Study on the Growth Mechanism and Microstructure of a Heavy Hail in the Eastern Part of Qinghai Province

2004年8月18日青海省东北部大通、互助出现一次强降雹过程,利用多普勒雷达观测资料分析了冰雹云生长过程并利用现场观测的雹谱和收集的雹块进行了冰晶、气泡结构和同位素研究分析。结果表明:雹谱呈双峰型,雹块呈锥状,少数为椭圆体。冰雹切片中,雹胚以霰为主;雹块按生长方式分为四层,中间两层冰晶最长、厚度较大,表明这两个层次是这次降雹雹块的主要生长区,其生长高度较低、温度较高,生长厚度较大。锥形雹块的气泡以径向纹理为主,近似于椭圆形的雹块中的气泡以纬向纹理为主。雹块中的气泡浓度分布皆呈单峰型,气泡谱宽不超过100μm。雹块透明、不透明层气泡浓度不完全一致,有所起伏。对各层氘同位素的测量结果表明,雹块生长温度相应在-10.0^-24.0℃,生长高度相应在4.5~9.0 km(海拔高度),雹块在相对湿融的气层中,上、下翻滚增长,与冰晶分析的结果基本一致。

Using the Doppler radar data to analyse a heavy hail process which appeared in Datong and Huzhu in the northeastern part of Qinghai Province on August 8, 2004, and the observed hail spectrum and collected hailstone, the isotope, bubble structure and ice crystal are analyzed. The results show that the hail spectrum have two peaks and the hailstone appear conical （a few of them show ellipsoidal）. In the hailstone, the main part of hail embryo is the graupel. The hailstone can be divided into four layers accord- ing to its growth mode and the two middle ice crystal layers which are the hail main growth areas are the longest and its thickness are relatively bigger and the growth altitudes of two middle ice crystal layers are lower, temperature are higher and the thickness are bigger. The main texture distribution of conical hail bubble is radial and similar ellipsoidal hail is longitudinal. The distribution of bubble concentration shows single peak in hail and the spectrum width of bubble is less than 100 μm. The bubble concentration of clear or unclear layers in hail is different with small fluctuation. The observation result for each layer isotope shows that the growth temperature of hail lies at 10 - -30℃ and the growth height lies at 4.0-9.0 kin. According to up and down mode the hail grow up in the humid atmosphere. It is consistent with the analytic result of ice crystal.