Tropical Cyclone Convection and Tropical Cyclogenesis

拟议的项目旨在提高我们对热带气旋形成过程的理解。我们知道，深层对流云（雷暴）在形成过程中起着重要的作用，但这些云如何组织和加强初期扰动的精确细节还不是很清楚。中等深度云在气旋形成过程中的作用，以及对流层上层冰云的作用，人们都知之甚少，后者是深层对流的副产品。我们知道，深层和中等深度的对流云都会在局部放大初生扰动的旋转，但我们并不确切地知道这种旋转对热带气旋的形成有多重要。我们建议通过进一步分析热带气旋形成的理想数值模式模拟来解决上述知识上的空白。这些分析将包括研究在模拟风暴的不同区域发展的深层对流系统的结构和演变，以及这些对流系统诱导对流层低层流入的能力，这是涡旋增强的已知条件。我们将通过比较包含冰过程的模拟和不包含冰过程的模拟来研究冰云的作用。我们还计划研究模拟风暴形成过程中深层和中等深层对流云的统计数据，并将对流携带的向上的空气质量与上升空气离开近地表摩擦层（通常为1公里深）时的热力学特性联系起来。我们最近的工作表明，涡旋的增强以一种微妙的方式依赖于深层对流的能力，这种能力可以去除摩擦层内流向涡旋中心的空气。

The proposed project aims to improve our understanding of the processes by which tropical cyclones form. We know that deep convective clouds (thunderstorms) play an important role in the formation process, but the precise details of how these clouds operate to organize and intensify an incipient disturbance is not well understood. The role of moderately deep clouds in the formation of a cyclone is poorly understood as is the role of upper tropospheric ice clouds, which are a byproduct of deep convection. We know that both deep and moderately deep convective clouds locally amplify the rotation of an incipient disturbance, but we do not know precisely how important this rotation is for the formation of a tropical cyclone. We propose to address the foregoing gaps in knowledge by further analyses of idealized numerical model simulations of tropical cyclogenesis. These analyses will include an investigation of the structure and evolution of deep convective systems that develop in different regions of the simulated storms and the ability of these convective systems to induce lower tropospheric inflow, a known requirement for vortex intensification. We will investigate the role of ice clouds by comparing a simulation with ice processes included with one in which they are excluded.We plan also to examine the statistics of deep and moderately deep convective clouds during the formation of simulated storms and to relate the upward mass of air carried by the convection to the thermodynamical properties of the rising air as it leaves the near-surface friction layer, typically 1 km deep. Our recent work has shown that vortex intensification depends in a delicate way on the ability of deep convection to remove the air that is flowing towards the vortex centre within this friction layer.