Collaborative Research: Global Aspects of Tropical Cyclogenesis

热带气旋（飓风）不会在热带大气中自发出现；相反，它们必须由先前存在的干扰触发。据推测，这些风暴是热带大气的亚临界不稳定性。这意味着触发飓风所需的扰动强度取决于热带大气和海洋的背景状态，而且，至少在理论上，飓风可能在不同的气候中自发出现，这种气候的不稳定参数超过了临界点。亚临界不稳定性的假设将通过一个高分辨率的数值模型来探索，以绘制热带气旋形成的不稳定性图，并揭示该图结构背后的物理过程。从这些实验中获得的物理见解，加上观测数据和更理想模型的实验，将用于开发和完善气旋形成指数。最终，这样一个指数可以提供关于飓风在不同气候条件下形成频率的信息。这项研究的更广泛的影响包括培训一名研究生和一名博士后研究员，以及开发理解和工具，这些理解和工具可能导致对热带气旋活动将如何随着气候变化而变化（无论是自然的还是由于人类影响）的改进预测。

Tropical cyclones (hurricanes) do not appear spontaneously in the tropical atmosphere; instead they must be triggered by a preexisting disturbance. It is hypothesized that these storms are subcritical instabilities of the tropical atmosphere. This implies that the strength of the disturbance necessary to trigger a hurricane depends on the background state of the tropical atmosphere and ocean, and that, at least in theory, hurricanes could appear spontaneously in a different climate, one with instability parameters that exceed a critical point.The hypothesis of subcritical instability will be explored using a high-resolution numerical model to map out the instability diagram for tropical cyclogenesis and to reveal physical processes underlying the structure of this diagram. Physical insights from these experiments, together with observational data and experiments with a more idealized model, will be used to develop and refine a cyclogenesis index. Ultimately such an index can provide information about the frequency with which hurricanes form in different climates.Broader impacts of this research include training a graduate student and a post-doctoral researcher, as well as developing understanding and tools that could lead to improved predictions of how tropical cyclone activity will change as climate changes, either naturally or due to human influence.