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郑永光, 黄振强, 陈炯, 王美慧. 2024. 对流风暴大气不稳定机制研究的若干问题[J]. 暴雨灾害, 43(3): 266-275. DOI: 10.12406/byzh.2024-030
引用本文: 郑永光, 黄振强, 陈炯, 王美慧. 2024. 对流风暴大气不稳定机制研究的若干问题[J]. 暴雨灾害, 43(3): 266-275. DOI: 10.12406/byzh.2024-030
ZHENG Yongguang, HUANG Zhenqiang, CHEN Jiong, WANG Meihui. 2024. Some issues in studies on the atmospheric instability of convective storms[J]. Torrential Rain and Disasters, 43(3): 266-275. DOI: 10.12406/byzh.2024-030
Citation: ZHENG Yongguang, HUANG Zhenqiang, CHEN Jiong, WANG Meihui. 2024. Some issues in studies on the atmospheric instability of convective storms[J]. Torrential Rain and Disasters, 43(3): 266-275. DOI: 10.12406/byzh.2024-030

对流风暴大气不稳定机制研究的若干问题

Some issues in studies on the atmospheric instability of convective storms

  • 摘要: 大气不稳定是强对流天气发生的必要条件之一,具有复杂性。首先简要回顾了气块假设,给出了该假设的应用局限性,比如气块在对流风暴中的强上升运动必然会导致环境大气气压和涡度的变化等;然后梳理了大气的静力不稳定、对称不稳定以及其他多种类型不稳定的概念,重点总结了条件不稳定、湿绝对不稳定和条件对称不稳定的判据及其与对流风暴发生发展的关系,同时澄清了一些错误认识。判别条件不稳定最有效的方法是对气块作有限虚拟位移、使用对流有效位能(CAPE)来判别。CAPE和对流抑制能量的计算对抬升气块的温湿状况较为敏感,并需要进行虚温订正;最优CAPE值较地表CAPE具有更好的代表性。在强垂直风切变、低CAPE环境中,由于旋转导致的动力扰动气压梯度的加速作用对强对流风暴的发展至关重要;对流不稳定不一定对应于条件不稳定。条件对称不稳定的方便判别方法是使用饱和湿地转位势涡度,文中进一步总结了该不稳定所致的中尺度雨带特征。

     

    Abstract: Atmospheric instability is one of the necessary conditions for the occurrence of severe convective weather, which is characterized by its intricacies. This paper first briefly reviews the air parcel theory and points out its limitations in application, for example, changes in pressure and vorticity of the environmental atmosphere inevitably caused by the strong upward motion of parcels in convective storms. Then, the concepts of static instability, symmetric instability, and other types of instability are reviewed. A special focus is given to summarizing the conditions for conditional instability, moist absolute instability, and conditional symmetric instability, as well as their relationship with the occurrence and development of convective storms, with some misunderstandings being clarified. The most effective method for determining conditional instability is to make a finite virtual displacement of the parcel and then use convective available potential energy (CAPE) for identification. However, the calculation of CAPE and convective inhibition is sensitive to the temperature and moisture of the parcel, and they should be computed and corrected using virtual temperature. The optimal CAPE value has better representativeness than that of the surface-based CAPE. In strong vertical wind shear and low CAPE environments, the acceleration effect of dynamic disturbance pressure gradient caused by rotation is crucial for the development of severe convective storms. Convective instability does not necessarily correspond to conditional instability. A straightforward method for distinguishing conditional symmetric instability is to use saturated equivalent geostrophic potential vorticity. We further summarize the mesoscale rainband characteristics caused by this type of instability.

     

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