Collaborative Research: Global Aspects of Tropical Cyclogenesis

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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.