章丽娜,周小刚,徐丽娅. 2017. 从能量角度对条件性不稳定相关问题的讨论[J]. 气象学报, ():-, doi:10.11676/qxxb2017.036
从能量角度对条件性不稳定相关问题的讨论
Discussions on some questions related to conditional instability from energy perspective
投稿时间:2016-10-27  最后修改时间:2016-12-28
DOI:10.11676/qxxb2017.036
中文关键词:  条件性不稳定,不稳定能量,CAPE,湿静力能
英文关键词:conditional instability, unstable energy, CAPE, moist static energy
基金项目:
作者单位E-mail
章丽娜 中国气象局气象干部培训学院 zhangln@mail.iap.ac.cn 
周小刚 中国气象局气象干部培训学院 zhouxgang@sina.com 
徐丽娅 中国气象局气象干部培训学院湖北分院 wmccp@163.com 
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中文摘要:
      大多数深厚的局地对流是在条件性不稳定的层结中发生的,这就有必要考虑较厚气层对由底部上升气块所可能产生的总影响。本文从能量角度讨论了条件性不稳定问题中的不稳定能量和对流有效位能(CAPE),还利用观测资料、结合实例分析了单站地面湿静力能与条件性不稳定中不稳定能量之间的关系。主要结论如下:(1)从能量观点,本文对对流有效位能的两种定义进行了讨论,认为对流有效位能定义为正、负不稳定能量之差时,其与动能相联系的表达式中包含了低层抬升速度,可以更全面地用于强对流天气预报,尤其是我国南方暖季的强对流预报。(2)气块从底层上升时,无论经历的是干绝热还是湿绝热过程,湿静力能守恒,所以总能量的变化就是动能的变化,等于外界合力对气块作功大小,不存在湿静力能向动能的转换。(3)从本质上来说,单站低层湿静力能的时序变化用于对流预报的意义在于预示着正、负不稳定能量的改变,从而影响不稳定能量的值。这可以弥补由于高空探测时间分辨率较粗,不能计算逐小时正、负不稳定能量的不足。
英文摘要:
      Most local deep convections are initiated in conditional unstable stratifications, so it’s necessary to consider the influence of deep air layer to the air parcel which is lifted from the base level. Some questions related to conditional instability, such as unstable energy, convective available potential energy (CAPE), are discussed from energy perspective. Besides, the relationship between the moist static energy of a single surface station and the unstable energy in conditional unstable stratifications are analyzed using a case study. The main results are as follows. (1) From energy perspective, the original definition of CAPE should be followed. That means CAPE equals the difference between positive and negative unstable energy. The lifting velocity in lower level associated with kinetic energy is implied in the formulation of original CAPE, which helps to forecast severe convective weather, especially in Southern China in warm season. (2) The moist static energy remains constant when the air parcel is lifted from low to high level, no matter during the dry adiabatic or moist adiabatic process. That indicates that the variation of total energy is only related to the variation of kinetic energy which is caused by the work of external force, not by the transformation from moist static energy. (3) The temporal variations of the moist static energy of a single surface station indicates the variation of positive and negative unstable energy, which is closely related to the calculation of unstable energy. Using such temporal variations help to make up for the coarse resolution of soundings and the deficiency of hourly data of positive and negative unstable energy.
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