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 Severe Hail Events in Guangdong Province
摘要点击 130  全文点击 44  投稿时间:2018-04-23  修订日期:2018-06-26
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基金:  
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, Characteristics of atmospheric stratifications, 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
谌芸Chen Yun国家气象中心
引用:曾智琳,谌芸.2019.广东省大冰雹事件的层结特征与融化效应[J].大气科学
Citation:Zeng zhilin,Chen Yun.2019.Characteristics of Atmospheric Stratification and Melting Effect of Severe Hail Events in Guangdong Province[J].Chinese Journal of Atmospheric Sciences (in Chinese)
中文摘要:
      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6h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≥20mm),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≥5mm且<20mm)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(Q_cc)对大冰雹融化起主要作用,其贡献率与DBZ(冻结层高度)、t_ave(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(Q_es)对大冰雹融化影响表现在DBZ高度上的冰雹直径越小、Q_es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△Td85(850hPa与500hPa的露点差)≥46℃、500hPa的T-Td≥15℃、1000hPa~700hPa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:
      Abstract Based on conventional L-band sounding, automatic weather station data and ERA-Interim 0.125°×0.125° 6h reanalysis data, we researched 23 heavy hail events (hail diameter ≥ 20mm ) selected according the grade of hail in China (GB/T 27957-2011) and occurring in Guangdong province from 2004 to 2017, mainly analyzed its characteristics of atmospheric stratifications, melting effect quantificationally, and set up a physical parameters model to distinguish heavy hail. The results are as follows: (1) vertical stratification of heavy hail events with characteristic of upper dry and lower moist is more evident than that of small hail (hail diameter ≥ 5mm and <20mm) events, and vertical potential instability is mainly triggered by upper dry and lower moist rather than upper cold and lower warm. (2) The ratio of H-/H+ (cold could/warm could) can be used to distinguish heavy hail and small hail, and the ratio above 1.6/1 is one of the conditions to forecast heavy hail. (3) Compared with small hail events, the height of maximum thermal buoyancy of heavy hail is higher than the height of -5℃, which helps hail embryo enter efficient growth layer (-10℃~-30℃), driving heavy hail growth. The maximum thermal buoyancy ≥4℃ is a key threshold to distinguish heavy hail and small hail. (4) Thermal conduction and convection transport (Q_cc) play a main role in melting process of heavy hail, and there is an anti-correlation between Q_cc and DBZ level (Dry bulb zero level) as well as t_ave (average temperature of environment). Latent heat consumed by vaporization and re-condensation of water firm resulted from hail melting process has an impact upon consequence that the smaller the hail diameter over DBZ level is, the larger the Q_es is, the greater the hail diameter will melt. Dry layer existed in mid-troposphere extends downward to lower troposphere, which helps to reduce the melting diameter of heavy hail. (5) based on statistics and comparative analysis of this paper, a physical parameters model was set up, including △Td85 ≥46℃, T-Td≥15℃ at 500hPa, the minimum T-Td≤2℃ between 700hPa and 1000hPa, H-/H+≥1.6/1, the intensity of maximum thermal buoyancy ≥ 4℃, and the height of maximum thermal buoyancy > the height of -5℃, which favor heavy hail generation.
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