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

在这项合作研究中，两位首席研究员将全面研究热带气旋及其所在的剪切气流之间相互作用的物理原理，重点研究动力和热力学过程的相互作用。他们假设，在涡旋与环境切变流相互作用的激励下，涡旋罗斯比波将低熵的中层空气注入涡旋核心，从而削弱了热带气旋。研究的重点（动力过程和热力学过程的相互重要性）与大多数以前的研究不同，这些研究几乎完全集中在直接的动力效应上。这项研究将有一条直接途径，通过改进一个业务预报模式来改进热带气旋的预报。研究的出发点是近十年来已经成熟的两个关键理论发展：飓风强度的热力学控制定量理论和涡旋罗斯比波的产生、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理论，用于涡旋和周围剪切流之间相互作用导致涡旋罗斯比波的产生和维持，以及这些波通量被动示踪剂进出涡旋核心区域的速率。这一理论将作为修正热力学循环的指导，以解释涡罗斯比波在中层注入干空气的原因。在开发了这一理论框架后，首席研究员将使用一套模型对其进行测试，重点是使用非流体静力模型在高分辨率下进行全三维模拟。预计该理论将根据这些测试的结果进行修正。最后，研究人员将利用这一理论开发低熵空气的罗斯比波诱导通量的参数化，用于轴对称模型，包括上述业务预报模型。该项目的知识价值：热带气旋与周围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力学上。在这个项目中，研究人员将结合相互作用的热力学和动力学方面来创建一个过程的一般和完整的描述。该项目的更广泛影响：尽管风暴路径预测技术取得了实质性进展，但飓风强度预测技术仍然很差。对热带气旋强度的研究是美国天气研究计划的重中之重。这一研究很可能有助于进一步了解环境切变对飓风强度的影响；这种先进的理解将直接纳入现有的飓风强度预测模型，从而直接导致，并在本合同的时间框架内，改进飓风强度预测。在进行这项研究的过程中，主要研究人员将培养飓风和飓风预测科学方面的高级研究生，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.