Dynamics and Predictability of Extratropical Vortices

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Tropopause vortices are ubiquitous features at high latitudes. While some of these vortices, such as cut-off cyclones, are related to extratropical cyclogenesis and Rossby wave breaking, others appear to occur independently of these processes. In particular, over the arctic, vortices occur poleward of the extratropical jet streams and are a defining characteristic of the interior of the larger circumpolar vortex. Explanations for arctic vortex origination and intensification are lacking, and these issues form the basis for the research. A second thrust of the research concerns the predictability of the larger-scale flows that contain these vortices. Key hypotheses regarding vortex intensity changes will be tested using both observational and modeling approaches and these are: (1) radiative cooling is responsible for saturating the core of arctic vortices, and that this process is important for the vortex dynamics; (2) weaker stability near the tropopause may allow the level of maximum latent heating associated with condensation to move up closer to the dynamical tropopause; and (3) radiation may dominate latent heating for very cold vortices, and latent heating may dominate for warmer vortices. Modeling strategy will be applied to systematically test the hypotheses regarding the feedbacks of radiation and latent heating on tropopause vortex dynamics. Intellectual Merit: The PI will (1) test key hypotheses regarding vortex intensity changes using both observational and modeling approaches; (2) use observational work to determine the large-scale patterns associated with vortex intensity changes for a large sample of cases; and (3) will examine individual cases using numerical model simulations and ensemble-based state estimation techniques. Broader Impacts: The research will improve our understanding of the polar vortices and also increases the predictability of mid-latitude weather. A graduate and undergraduate student will be trained in the observational and modeling analysis of polar vortices.