新疆图木舒克市冰雹天气的环流背景和判识指标分析

Analysis of the Circulation Background and Identifying Indicators of Hail in Tumxuk City, Xinjiang

摘要: 根据新疆图木舒克市及其辖区内2012~2019年近8a来区域自动气象站常规资料、NCEP/NCAR 1˚ × 1˚再分析资料，总结分析了新疆图木舒克市及其辖区内冰雹天气的影响系统和环流形势；并利用CINRAD/CC型雷达图像产品对该区域近8a 23个冰雹天气个例进行了统计分析，归纳出新疆图木舒克市及其辖区内冰雹天气的雷达图像产品判识指标。结果表明：(1) 新疆图木舒克市冰雹天气的3类影响系统和环流形势有：巴尔喀什湖低槽型、中亚低槽(涡)型、锋区短波槽型。(2) 当满足K ≧ 23℃、T850 hPa-T500 hPa ≧ 32℃，假相当位温 ≧ 330℃，具有一定的对流有效位能(CAPE值)，适宜的0℃层和−20℃层高度，可作为判断该区域是否出现冰雹的环境场条件。(3) 新疆图木舒克市及其辖区内冰雹天气的雷达图像产品判识指标为：组合反射率因子(CR) ≥ 50 dBZ以上，强回波中心(45~50 dBZ)的高度 ≥ 7 km；6~8月冰雹云的回波顶高(ET) 10~12 km；径向速度场V常伴有逆风区，逆风区平均厚度4000米，具有风暴顶辐散特征；径向速度垂直剖面(RCS)出现垂悬回波、有界弱回波区(BWER)等特征回波；垂直风廓线产品(VWP)从低层到中高层出现风向、风速的垂直切变特征；云体垂直累积液态水含量5月VIL ≧ 20 kg∙m⁻²，6~8月VIL ≧ 30 kg∙m⁻²，且VIL在测站降雹前具有跃增增长现象；冰雹指数产品(HI)至少持续5个体扫出现实心大三角标识。

Abstract: The effect systems and circulation patterns of hail in Tumxuk City, Xinjiang and the area under its jurisdiction were summarized and analyzed according to daily data in the nearly 8 years from 2012 to 2019 from the regional automatic weather station and the NCEP/NCAR 1˚ × 1˚ reanalysis data. Then, a CINRAD/CC radar image product was used for a statistic analysis of 23 hail cases collected from the region during the 8 years. The results show that (1) there are three hail effect systems and circulation patterns in Tumxuk: a Balkhash Lake low trough, Central Asia low trough (vortex), and frontal zone short-wave trough. (2) With K ≧ 23˚C, T850 hPa-T500 hPa ≧ 32°C, and pseudo-equivalent potential temperature ≧ 330˚C, there is certain convective available potential energy (CAPE) between the 0˚C height and −20˚C height, and it is practical to judge that the region is an environment field for hail. (3) The following are the identifying indicators in the radar image product for hail in Tumxuk and the area under its jurisdiction: composite reflectivity factor (CR) ≥ 50 dBZ, strong echo center (45 - 50 dBZ) height ≥ 7 km; the echo top (ET) of hail clouds from June to August is 10 - 12 km; the radial velocity field V is often accompanied by an adverse wind zone whose average thickness is 4,000 m and which is characterized by storm top divergence; characteristic echoes, such as overhang echoes and bounded weak echo regions (BWER), appear on the radar cross-section (RCS); the vertical wind profile (VWP) is characterized by vertical shear and velocity from the lower layer to the middle and upper layers; the vertically integrated liquid water content VIL ≧ 20 kg∙m⁻² in May and VIL ≧ 30 kg∙m⁻² in June to August. Moreover, the VIL tends to jump strongly before hail appears at the survey station; a large, solid triangle identifier appears in at least 5 sweep volumes of the hail index (HI).