Collaborative Research: The Relationships between Sheared Convective Clouds and Tropical Cyclone Evolution

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Despite improving observational and computational resources, the forecasting of tropical cyclone (TC) structural and intensity evolution is still a significant challenge. The limits of predictability relate to the nonlinear interactions between a TC's multi-scale dynamics and its environment. Recent research underscores how TC evolution is influenced strongly by the details of latent heating. As such, properly accounting for convective processes in TCs is a key step towards a more complete physical understanding of TCs and improved prediction. Yet, potentially essential aspects of convective-scale dynamics remain unresolved. The detailed structure of kinematic and thermodynamic properties found within TCs can provide a broad spectrum of distinct local environments resulting in a variety of convective and mesoscale cloud morphologies. Each convective mode may have unique impacts on TC evolution.Intellectual merit:To advance the understanding of convective-scale processes in TCs, this multi-framework study will investigate the interactions of vertical and horizontal wind shear with both isolated convective clouds and more organized rainbands. Through this research effort, the following questions will be examined:1. How do strong horizontal wind shear and background absolute vertical vorticity impact isolated convective clouds and rainbands?2. What are the primary interactions that occur between horizontal and vertical shears and convection?3. How does the response of convection to three-dimensional shear vary given the variations of ambient thermodynamic conditions within TCs?4. What are the implications of the various convective modes resulting from kinematic and thermodynamic variability on overall TC dynamics?The multiple frameworks for this study will include an idealized cloud model, high-resolution flight-level Doppler radar and in situ observations of TCs, and two full-physics TC simulations. Sensitivity experiments with a cloud model will be used to understand how three-dimensional wind shear and thermodynamic variability within TCs govern isolated convective clouds and convective systems. The impacts of sheared convection on the mean flow will also be documented in the cloud model. The observational analyses and TC simulations will provide realistic settings to evaluate the idealized cloud modeling results and to deduce feedbacks and relationships between the various sheared convective modes, rainbands, and TC dynamics. Vorticity, potential vorticity, and thermodynamic budgets and general statistical analysis of cloud, precipitation, and cold pool properties will be the primary tools of analysis for elucidating open questions related to sheared TC convection.Broader impacts:The research will shed new light into basic internal dynamical processes related to TC intensity and structure change and it will have more general theoretical impacts outside of TC research. The resulting peer-reviewed publications will provide both applied and theoretical contexts in which both researchers and forecasters can interpret convective scale processes in TCs. Improvement in forecasting TCs and convective-scale processes in TCs will in turn be beneficial to society. The research team will work with the Center for Hurricane Intensification and Landfall Investigation and talented and motivated undergraduate/graduate students who will contribute to significant aspects of the research and subsequent, peer-reviewed publications. A webpage containing animations of key experimental results will supplement research articles and will also aid in college classroom instruction and other outreach efforts such as scientific high school workshops.