Nowcasting indicators of radar of hail cloud in southern Tianshan Mountains
WANG Yun;LU Pin-rui;WANG Xu;College of Atmospheric Sciences of Lanzhou University;Zhangye Meteorological Bureau;Xinjiang Weather Modification Office;
In this paper,the variation characteristics of hail stone in the range of May to August from 2008 to2017 were analyzed by using the observation records of Kashi meteorological stations on the south side of Tianshan Mountains,Xinjiang,China,the records of artificial hailing,Kashi sounding data at 08: 00 AM and 20: 00 PM and detection data of radars. The radar echo characteristics and the moving path of the hail cloud were studied and forecast index and radar warning index of the hail cloud are determined based on the percentile method. The results showed as follows:( 1) Hail stone appeared on the south side of the Tianshan Mountains in the past 10 years,concentrated on the period from May to August and most appear in Jun,especially at 18: 00 ~ 24: 00 PM and most at20: 00 PM.( 2) The four migration paths of hail cloud were northwest,north,west and southerly. One half of hail cloud origin in the southern Tianshan Mountainous Area,and the other half originated in the plain area in eastern Kashi Prefecture.( 3) The potential forecasting index of hail in the range of May to August is 0 ℃ layer height difference smaller than 4. 6 km,-20 ℃ layer height difference smaller than 7. 5 km,freezing layer thickness is less than 3. 0 km,General index is bigger than 46 ℃,Jefferson index is bigger than 114. 0 ℃,K index is bigger than 21℃ and SI index is smaller than 1. 8 ℃ at 08: 00 AM.( 4) The Radar warning indexes of hail cloud in the range of May-August before hail 15 min are as follows: The echo top height is bigger than 12. 2 km,and the 0 ℃ height difference is bigger than 7. 7 km. The 40,45,50 d BZ echo heights are greater than 9. 4,8. 6,7. 8 km respectively and the 0 ℃ layer height difference is bigger than 4. 9,4. 0,3. 4 km. In addition,combined reflectivity is bigger than 53 dBZ,vertical cumulative liquid water content is bigger than 13 kg·m-2,and thickness of upwind zone in the radial wind field is exceeds 1. 8 km. The Radar warning indexes of hail in the range of May-August before hail30 min are as follows: the echo top height is bigger than 12. 3 km,0 ℃ layer height difference bigger than 7. 8 km.The 40,45,50 d BZ echo heights are greater than 9. 6,8. 1,7. 3 km respectively and the 0 ℃ layer height difference is bigger than 5. 1,3. 5,2. 7 km. Moreover,the combined reflectance is greater than 47 d BZ,vertical cumulative liquid water content is greater than 7 kg·m-2,and thickness of upwind zone in the radial wind field is exceeds 1. 5 km.
【CateGory Index】： P457
【CateGory Index】： P457