对流温度含义阐释及部分示意图隐含悖论成因分析与预报应用

Analysis of the implicit mistakes in the several schematic diagrams for the implication of convective temperature with its application to forecasting

  • 摘要: 分析和预报局地对流时常用到对流温度,对流凝结高度常被用于估计局地对流云的云底高度。对流温度和对流凝结高度用于局地对流分析时存在一定的前提,且其蕴含的物理意义非常丰富。论文剖析了几本较为经典的气象专业书籍中对流温度概念图示,指出其中隐含的悖论,包括与大气稳定度基本常识相悖、违反大气能量学理论、以及与物理量本身含义明显抵触。进一步阐释构图不够严谨、对对流温度含义理解不完全到位是出现这种悖论的根本原因。并构造了物理意义清晰、气象基本理论更为合理的对流温度示意图。利用观测资料,分析了北京夏季对流云的发生频数和生成时间,尝试用对流温度预报局地对流云的生成,用对流凝结高度预报局地对流云云底高度。结果表明,对流温度在局地对流云的预报中具有一定的指示意义,对流凝结高度能在一定程度上反映出局地对流云的云底高度。如果将最高温度不低于对流温度1℃作为判定能否产生对流云的一个标准,临界成功指数达到45%。

     

    Abstract: The convective temperature is commonly used to the analysis and prediction of local convection, while the convective condensation level (CCL) is often used to estimate the base height of local convective cloud. There is certain precondition when the convective temperature and CCL are utilized to analyze local convection, and its inherent physical meaning is abundant. In this paper, thermodynamic diagrams of the convective temperature in the several classical books are analyzed, and some implicit mistakes are pointed out, which includes violating elementary knowledge of the atmospheric stability, opposing to theory of atmospheric energy, and conflicting with its inherent meaning. It is further pointed out that not being strict, and not knowing the inherent meaning of convective temperature thoroughly are the main factors in the process of making convective temperature diagram which cause these mistakes. A new diagram of convective temperature is constructed in this paper, with clearly physical meaning and more correspondingly to the basic meteorological theory. Observation data is employed to analyze the basic characteristics of convective clouds in summer Beijing, including occurrence numbers of convective clouds and occurrence time. Attempt is made to predict both the genesis and base height of convective cloud by using the convective temperature and CCL respectively. The results show that there exists some indicative significance of convective temperature as to local convection, and CCL can reflect the cloud base height of convective cloud to certain extent. The critical success index (CSI) reaches 45% when the difference between the maximum temperature and the convective temperature no more than 1℃ is assigned to be the judgment of local convection development.

     

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