Symmetric and Asymmetric Intensification Processes in Tropical Cyclones

热带气旋的发展和增强很大程度上是由围绕风暴中心组织的积雨云对流中凝结潜热的释放驱动的。 对于发展中的风暴，这些对流区域是高度不对称的，并且经常偏离风暴中心。 在以前的工作中，主要研究者已经展示了如何在不对称对流中释放的热能通过一系列不对称然后对称的调整过程转化为轴对称风场的动能。 从以前的工作使用平衡模型的轴对称动力学，它是已知的，这一过程的效率（单位加热的涡流强化量）是相当小的，在5%的顺序，强烈地依赖于对流的位置和结构的气旋本身。 用于这项工作的新模型解决了不对称和对称运动的不平衡，完全非流体静力学动力学。 该项目将进一步分析对称和非对称过程，介导这些能量转移，特别是将记录特定的加热分布和风暴结构的强化过程的效率。 我们亦会研究向外传播的重力波与对称风场的相互作用，沿着探讨重力波与螺旋带形成的可能机制，这项工作将有助我们更好地了解和预测热带气旋的发展和快速增强现象。 用以模拟对称和非对称调整过程的计算机程序将提供给社会各界普遍使用。 该项目还可能为飓风强度预测的新方法奠定基础，这种方法将把联合收割机对降水和对流加热的卫星观测与预测短期强度变化的简单动力学模型结合起来。

Tropical cyclone development and intensification is driven in large part by the release of latent heat of condensation in cumulonimbus convection organized around the center of the storm. For developing storms, these areas of convection are highly asymmetric and often displaced from the storm center. In previous work, the Principal Investigator has shown how the heat energy released in asymmetric convection is converted into kinetic energy of the axisymmetric wind field through a sequence of asymmetric and then symmetric adjustment processes. From previous work using balance models of axisymmetric dynamics, it is already known that the efficiency of this process (the amount of vortex intensification per unit heating) is quite small, on the order of 5%, and depends strongly on both the location of the convection and the structure of the cyclone itself. The new model used for this work resolves the unbalanced, fully nonhydrostatic dynamics of both asymmetric and symmetric motions. This project will further analyze the symmetric and asymmetric processes, which mediate these energy transfers, and in particular will document the efficiency of the intensification process for particular heating distributions and storm structures. The interaction of outward propagating gravity waves with the symmetric wind field also will be examined, along with a new possible mechanism connecting gravity waves to spiral band formation.This work potentially will lead to better understanding and forecasting of tropical cyclone development and rapid intensification phenomena. The computer programs used to simulate the symmetric and asymmetric adjustment processes will be made available to the community for general use. This project may also lay the foundation for a new approach to hurricane intensity forecasting, which would combine satellite observations of precipitation and convective heating with a simple dynamical model to predict short-term intensity change.