Tropical Cyclone Convection and Tropical Cyclogenesis

建议的项目旨在提高我们对热带气旋形成过程的认识。我们知道，深对流云（雷暴）在形成过程中起着重要作用，但这些云如何组织和加强初期扰动的确切细节还没有得到很好的理解。对于中等深度的云层在气旋形成中的作用，以及对流层上层冰云的作用，人们知之甚少，而冰云是深对流的副产品。我们知道深对流云和中等深对流云都会局部放大初始扰动的旋转，但我们不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生成的理想化数值模式模拟来解决上述知识差距。这些分析将包括调查在模拟风暴的不同区域发展的深对流系统的结构和演变，以及这些对流系统引起低对流层流入的能力，这是涡旋强化的一个已知要求。我们将研究冰云的作用，通过比较一个模拟与冰过程中，包括一个排除，我们还计划检查在模拟风暴的形成过程中的深和中等深度的对流云的统计数据，并与对流携带的空气向上的质量上升的空气，因为它离开近地面的摩擦层，通常1公里深的物理特性。我们最近的工作表明，涡的强化以一种微妙的方式取决于深对流的能力，以消除空气流向涡中心在这个摩擦层。

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.