doi:  10.3878/j.issn.1006-9895.1808.18152
广东省大冰雹事件的层结特征与融化效应

Characteristics of Atmospheric Stratification and Melting Effect of Heavy Hail Events in Guangdong Province
摘要点击 472  全文点击 278  投稿时间:2018-04-23  
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基金:  国家自然科学基金项目41175048、41330421
中文关键词:  大冰雹事件  大气层结特征  融化效应  物理参数模型
英文关键词:  Heavy hail events (HHEs)  Characteristics of atmospheric stratification  Melting effect  Physical parameters model
           
作者中文名作者英文名单位
曾智琳ZENG Zhilin成都信息工程大学大气科学学院,成都 610225;国家气象中心,北京 100081
谌芸CHEN Yun国家气象中心,北京 100081;成都信息工程大学大气科学学院,成都 610225
朱克云ZHU Keyun成都信息工程大学大气科学学院,成都 610225
李晟祺and LI Shengqi南京信息工程大学,南京 210044
引用:曾智琳,谌芸,朱克云,李晟祺.2019.广东省大冰雹事件的层结特征与融化效应[J].大气科学,43(3):598-617,doi:10.3878/j.issn.1006-9895.1808.18152.
Citation:ZENG Zhilin,CHEN Yun,ZHU Keyun,and LI Shengqi.2019.Characteristics of Atmospheric Stratification and Melting Effect of Heavy Hail Events in Guangdong Province[J].Chinese Journal of Atmospheric Sciences (in Chinese),43(3):598-617,doi:10.3878/j.issn.1006-9895.1808.18152.
中文摘要:
      本文主要利用L波段常规探空数据、华南区域加密自动站资料以及ERA-Interim 0.125°×0.125°逐6 h再分析资料,依据我国冰雹等级划分标准(GB/T 27957-2011)筛选了2004~2017年发生在广东的23个大冰雹事件(直径≥20 mm),重点分析其大气层结状态与结构特征,定量诊断了大冰雹的融化效应,并建立了判别大冰雹的物理参数模型。结果表明:(1)大冰雹事件“上干下湿”比非大冰雹(直径≥5 mm且<20 mm)事件更加清晰,产生大冰雹所需的对流(位势)不稳定建立更依赖于“上干下湿”而不是“上冷下暖”。(2)H/H+(冷云和暖云厚度比值)对于区分大冰雹与非大冰雹具有较好的指示效果,H/H+高于1.6/1对判别产生大冰雹有参考价值。(3)相比于非大冰雹事件,大冰雹事件最大热浮力高度高于−5℃层,有利于托举雹胚进入有效增长层(−10℃~−30℃),促使雹胚生长为大冰雹。最大热浮力强度≥4℃可作为判别大冰雹与非大冰雹的关键阀值。(4)热传递与对流交换()对大冰雹融化起主要作用,其贡献率与DBZ(冻结层高度)、(环境平均温度)呈反比关系;冰雹表层水膜因蒸发或重新凝结消耗潜热()对大冰雹融化影响表现在DBZ高度上的冰雹直径越小、融化贡献率越大,大冰雹融化程度越大。高空的干层向下延伸到较低高度有利于大冰雹不被或少被融化,也是大冰雹事件WBZ(湿球零度层高度)显著低于DBZ的重要原因。(5)基于全文统计内容与对比分析,构建了一个判别大冰雹的物理参数模型,大气层结满足ΔTd85(850 hPa与500 hPa的露点差)≥46℃、500 hPa的T−Td≥15℃、1000~700 hPa最小的T−Td≤2℃、H/H+≥1.6/1,最大热浮力强度≥4℃、最大热浮力高度高于−5℃层时,有利于产生大冰雹。
Abstract:
      Based on conventional L-band soundings, automatic weather station data and ERA-Interim 0.125°×0.125° reanalysis data at 6-hour intervals, we investigate 23 heavy hail events (HHEs, hail diameter ≥20 mm) that occurred in Guangdong province from 2004 to 2017. The 23 hail events are selected according to the Hail Classification Standard in China (GB/T 27957-2011). Characteristics of atmospheric stratification during these events and melting effects of hails are quantitatively analyzed, and a model of physical parameters is established to distinguish heavy hails. The results are as follows. (1) The upper-dry and lower-moist characteristic of vertical stratification is more evident for HHEs than for small hail events (SHEs, hail diameter ≥5 mm and <20 mm), and the convective (potential) instability is more dependent on the upper-dry and lower-moist stratification rather than that of the upper-cold and lower-warm. (2) The ratio of H/H+ (cold cloud/warm cloud) can be used to distinguish HHEs from SHEs, and the ratio above 1.6/1 is one reference criterion for the forecast of heavy hails. (3) Compared with SHEs, the height of maximum thermal buoyancy of HHEs is higher than the isothermal layer of −5℃, which helps the hail embryos to enter efficient growth layer (−10℃-−30℃) and thus drives heavy hail growth. The maximum thermal buoyancy ≥4℃ is a key threshold to distinguish HHEs from SHEs. (4) Thermal conduction and convection transport () play a main role in the melting process of heavy hails, and there is an anti-correlation relationship of with DBZ level (dry bulb zero level) and (average environmental temperature). Impacts of latent heat caused by vaporization and re-condensation of water resulted from hail melting process are reflected in the fact that the smaller the hail diameter over the DBZ level is, the larger the latent heat consume or release, originated from evaporation of water surrounding hail (), and the greater the large hails will melt. The downward extension of the dry layer in the mid-troposphere inhibits the melting of large-size hails. (5) Based on statistical and comparative analyses of this paper, a model of physical parameters is established for prediction of heavy hails. These physical parameters include ΔTd85≥46℃, T−Td≥15℃ at 500 hPa, the minimum T−Td≤2℃ between 700 hPa and 1000 hPa, H/H+≥1.6/1, the intensity of maximum thermal buoyancy≥4℃, and the height of maximum thermal buoyancy higher than the height of −5℃. The above conditions are favorable for the generation of heavy hails.
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