湿位涡、热力学参数C_D与涡度、散度演化

The Effects of Moist Potential Vorticity and Thermodynamic Parameter C_D on Evolution of Vorticity and Divergence

从湿斜压原始方程出发,将热力学方程引入散度方程,导出了显示包含热力学参数CD影响的散度方程。在此基础上,结合湿位涡方程,分析了湿斜压大气中湿位涡水平分量MPV2及其热力学参数CD的动力学性质,揭示了由热力学参数CD表征的斜压动力过程激发对流层中低层涡、散场演变的动力机制,阐明了应用热力学参数CD诊断暴雨中尺度系统发生发展和预报暴雨的理论依据。

Torrential rain and flood are the main disasters of meteorology in China in summer. So meteorology workers pay close attention to the causes of torrential rain and the forecast of it. Our level of understanding heavy rain process is low because of the complex nature of heavy rain formation. It is imperative to enhance research on occurrence mechanism of heavy rainfall. According to the occurrence and development of torrential rain relating closely to convergence increase in low and middle layer of troposphere, making further research on divergence equation and its application is conductive to reveal physical mechanics of the evolution of torrential rain process. In this paper, divergence equation explicitly including effects of thermodynamic parameter CD on divergence evolution is deduced from complete set of primitive equation system. Dynamic property of thermodynamic parameter CD and horizontal component of moist potential vorticity MPV2 is analyzed on basis of divergence equation and moist potential vorticity equation. Relationship between the evolution of divergence and vorticity and thermodynamic parameter CD is revealed. Coupling forces between dynamic and thermodynamic fields are able to excite the increase of convergence and positive vorticity in low and middle layer of troposphere while CD〉0; conversely, they contribute the increase of divergence and negative vorticity. This paper provide theoretic basis for the thermodynamic parameter CD employed in diagnosis of generation and development of mesoscale heavy rain systems.