Collaborative Research: Dynamic and Thermodynamic Control of Tropical Cyclone Intensity in Sheared Environments

在这项合作研究工作中，首席调查员将对热带气旋与切变气流之间的相互作用进行全面的物理调查，重点是动力和热力学过程的相互作用。他们假设，热带气旋是通过涡旋和环境切变流之间的相互作用而激发的涡旋Rossby波向涡核注入低熵的中层空气而减弱的。研究的重点(动力学和热力学过程的相互重要性)与以往的大多数研究不同，以前的研究几乎完全集中在直接动力学效应上。这项研究将直接通过改进业务预报模式来改进热带气旋的预测。研究的起点是两个在过去十年中成熟的关键理论发展：飓风强度的热力学控制的定量理论，以及控制涡旋Rossby波的产生、行为和波/平均流相互作用的理论。从这些观点出发，首席研究人员将发展一个扩展的理论，作为涡旋和环境切变流动之间相互作用的结果，产生和维持涡旋Rossby波，以及这些波流入和流出涡核区域的被动示踪剂的速率。这一理论将被用来指导修改热力学循环，以解释涡旋Rossby波在中层注入的干空气。在开发了这一理论框架之后，首席研究人员将使用一套模型对其进行测试，重点是使用非静力模型进行高分辨率的全三维模拟。预计将根据这些试验的结果对该理论进行修正。最后，研究人员将利用这一理论开发一个用于轴对称模式的Rossby波诱导的低熵空气通量的参数化，包括前述的业务预报模式。该项目的智力优势：热带气旋与环境风场之间相互作用的本质多年来一直是个谜。以前理解和量化这种相互作用的努力几乎完全集中在动态上。在这个项目中，研究人员将把相互作用的热力学和动力学方面结合起来，以创建对该过程的全面和完整的描述。该项目的更广泛的影响：尽管风暴路径预测技术取得了实质性进展，但飓风强度预测的技术仍然很差。热带气旋强度的研究是美国气象研究计划的优先事项。这项研究很可能导致对环境切变对飓风强度影响的高级理解；这种高级理解将直接纳入现有的飓风强度预测模型，从而在本奖项的时间范围内直接导致改进飓风强度预测。在进行这项研究的过程中，首席调查员将对高级研究生进行飓风科学和飓风预测方面的培训，从而帮助培养新一代的研究人员和预报员。

In this collaborative research effort, the Principal Investigators will undertake a comprehensive investigation of the physics of the interaction between tropical cyclones and sheared flow in which they are embedded, focusing on the mutual operation of dynamic and thermodynamic processes. They hypothesize that tropical cyclones are weakened by the injection of low-entropy, middle level air into the vortex core by vortex Rossby waves excited by the interaction between the vortex and environmental shear flow. The research emphasis (mutual importance of dynamical and thermodynamical processes) departs from most previous investigations, which have focused almost exclusively on direct dynamical effects. The research will have a direct path to improved prediction of tropical cyclones through the improvement of an operational forecast model.The starting point of the research is two key theoretical developments that have matured over the previous decade: the quantitative theory of thermodynamic control of hurricane intensity, and the theory governing the generation, behavior and wave/mean flow interaction of vortex Rossby waves. From these points, the Principal Investigators will develop an extended theory for the generation and maintenance of vortex Rossby waves as a consequence of the interaction between vortices and ambient shear flow, addressing as well the rate at which these waves flux passive tracers in and out of the vortex core region. This theory will be used as guidance in modifying the thermodynamic cycle to account for dry air injection at middle levels by vortex Rossby waves. Having developed this theoretical framework, the Principal Investigators will test it using a suite of models, focusing on fully three dimensional simulations at high resolution using a nonhydrostatic model. It is expected that the theory will be modified based on the results of these tests. Finally, the researchers will use this theory to develop a parameterization of Rossby wave-induced fluxes of low entropy air, for use in axisymmetric models, including the aforementioned operational forecast model.The intellectual merit of the project: The nature of the interactions between tropical cyclones and the ambient wind field has remained enigmatic for many years. Previous efforts to understand and quantify this interaction have focused almost exclusively on the dynamics. In this project, the researchers will marry thermodynamic and dynamic aspects of the interaction to create a general and complete description of the process.The broader impacts of the project: The skill of hurricane intensity forecasts remains poor in spite of substantial advances in the skill of storm track forecasts. Research on tropical cyclone intensity is a high priority under the U.S. Weather Research Program. This research may well lead to an advanced understanding of the effect of environmental shear on hurricane intensity; such advanced understanding will be directly incorporated into an existing hurricane intensity prediction model, thereby leading directly, and within the time frame of this award, to improved hurricane intensity forecasts. In the process of carrying out this research, the Principal Investigators will train advanced graduate students in the science of hurricanes and hurricane prediction, thereby helping to foster a new generation of researchers and forecasters.