热带气旋边界层关键结构研究进展

Research progress on major structures of tropical cyclone boundary layer

边界层的动热力结构在很大程度上决定了热带气旋(TC)的发生发展,首先,TC边界层是触发TC对流的源地,并作为海-陆-气能量交换的主要中介,提供TC发生发展的重要能源;其次,边界层是TC对流发展所需水汽的主要输送通道;第三,TC登陆时,陆地下垫面摩擦直接作用于边界层,加强辐合、对流和湍流输送.对这些特征的了解有利于从根本上掌握TC发展变化的规律,为提高登陆TC分析和预报水平奠定基础,具有重要的科学价值和实际意义.本文在前期TC边界层研究工作的基础上,从热力学和动力学的角度,介绍了近年来国际上关于TC边界层风场、湍流交换、卷涡、能量和水汽输送等关键结构特征研究的主要进展.阐述了边界层入流对于TC能量平衡、水汽输送的重要作用,揭示了边界层超梯度风现象存在的机制和成因,以及边界层卷涡与边界层动量输送和TC强度发展的关系.这些认识有助于加强TC边界层关键结构对TC发展作用的理论认识.在此基础上,指出了目前TC边界层研究中存在的核心难点问题,并建议将TC边界层研究与数值预报方法相结合:除了将边界层观测通过资料同化应用于TC数值模式初始化,还可研究优化与TC涡旋结构相关的边界层参数化方法,实现TC数值模式初始化与边界层物理过程的衔接,探索可切实改进TC预报的有效途径.

The dynamical and thermodynamical structure of Planetary Boundary Layer （PBL） determines the genesis and development of tropical cyclone （TC） to a large extent. First, TC PBL serves as the source layer for the genesis of TC convection. It is also the interface for the exchange of energy among ocean, land, and atmosphere, which provides the energy for TC development. Second, PBL is the major source of moisture required by the growth of convection. Third, as TC making landfall, the increased friction associated with the change of terrain and PBL structure, enhances convergence, convection and turbulence. Knowledge on these characteristics of PBL helps to better understand the mechanism of TC evolution, which is the basis for the analysis and prediction of landfalling TC. Based on previous research on TC PBL, this study reviews the recent progress of research on TC PBL structures, such as, PBL wind, turbulence exchange, PBL rolls, energy, and moisture transportation. Special emphasis is focused on the role of TC PBL inflow in the energy balance and moisture flux, the mechanism and characteristics of supergradient wind, as well as the features of PBL rolls in association with momentum flux and TC intensity change, which extends the knowledge on the role of TC PBL in TC evolution. For the future study, thisstudy suggests appropriate use of PBL theory in TC numerical prediction. Besides the data assimilation of PBL observations in numerical model, new approaches are requested to be developed to optimize PBL parameterization schemes associated with TC vortex structure based on better understanding of TC model initialization and PBL physics, which is Believed to he an efficient engine for the improvement of TC prediction.