对流云和层云系统在热带气旋生成过程中的动力和热力作用

Previous studies have examined the large-scale background condition favorable for tropical cyclone (TC) formation. Within the favorable environment, the scattered and random convective cells may merge and be organized into mesoscale convective systems (MCSs), and eventually form a self-sustaining TC protovortex. Though some theoretical hypotheses have been proposed, the physical process on TC genesis isn’t well understood yet due to the lack of observational validation. Especially, the dynamic and thermodynamic roles of convective and stratiform clouds in TC genesis remain unclear. In this project, based on the satellite observational data, idealized and real TC numerical simulation, the temporal-spatial distribution and evolution of convective and stratiform clouds are examined during the period of TC genesis. heir respective contribution to the enhancement of lower-level circulation, the moisture of atmosphere and the formation of warm core are investigated during the development of MCSs. Through the sensitivity experiments, the TC formation process in response to the diabatic heating with distinct magnitude in these two cloud systems is revealed, which can further understand the dynamic and thermodynamic roles acted by the convective and stratiform clouds during the early stage of TC genesis. This project can not only advance the understanding of the mechanism of TC formation, but also provide a practical guide for the prediction of tropical cyclogenesis.

以往大量的研究已经揭示了有利于热带气旋（TC）生成的大尺度环流背景条件。在这些有利环境场中，零星随机的对流单体可能合并组织成中尺度对流系统（MCS），并最终发展生成可以自维持的TC雏形涡旋。尽管目前已经提出了一些科学理论假说，但由于实际观测的缺乏，对于这一物理过程还缺少深入的认识，特别是不同降水云系在此过程中分别起到了怎样的动力和热力作用还不是很清楚。本项目通过卫星观测资料的分析，理想和实际个例的数值模拟，系统考察对流云和层云系统在TC生成初期的时空分布和演变特征；揭示在MCS发展阶段，它们对于加强低层环流、加湿大气以及形成涡旋暖核结构的相对贡献；并通过敏感性数值试验，了解TC生成过程对于主要云系加热强度的响应，从而更进一步揭示了对流云和层云在TC生成初期所承担的动力和热力角色。本项目的研究不仅有助于深入理解西北太平洋TC生成的物理过程，而且也可以为TC生成的预报提供科学的理论指导。