Interaction Between Landfalling Hurricanes and the Atmospheric Boundary Layer Using Ensemble-based Data Assimilation

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Accurate forecasts of the intensity and structure of a hurricane at landfall can save lives and mitigate social impacts. However, among recent efforts in hurricane forecast improvements, few studies have focused on landfalling hurricanes. This reflects the complexity of predicting hurricane landfalls and the uncertainties in representing the atmospheric boundary layer conditions in numerical weather prediction (NWP) models. The aim of this study is to investigate the interaction between landfalling hurricanes and the atmospheric boundary layer using ensemble-based data assimilation.The study is based on two hypotheses: 1) the interaction between the hurricane and atmospheric boundary layer is an essential factor that controls the intensity and structure changes of landfalling hurricanes; and 2) the ensemble assimilation of surface mesonet and WSR-88D Doppler radar observations will improve the representation of near surface and boundary layer atmospheric conditions that interact with the landfalling hurricanes. Therefore, the research will incorporate the surface mesonet and Doppler radar observations with other available conventional and satellite data into an ensemble data assimilation system with the community mesoscale weather research and forecasting (WRF) model. The following four scientific questions will be addressed:1. How does a hurricane's structure evolve during its landfall?2. How, and to what extent, do atmospheric boundary layer environmental conditions influence the intensity and structure of landfalling hurricanes?3. How do the hurricane vortex and secondary circulation interact with the atmospheric boundary layer environmental conditions? 4. What are the processes that control the intensity and structural changes of landfalling hurricanes?Intellectual Merit: The research represents the first comprehensive study of the interaction between landfalling hurricanes and the atmospheric boundary layer as well as the predictability of landfalling hurricanes using ensemble-based data assimilation. Results from this study are expected to enhance our understanding of landfalling hurricanes and also contribute to the overall goals of our scientific community in improving hurricane intensity forecasts.Broader Impacts: Results from this study will facilitate the accurate prediction of hurricanes at landfall as well as their associated extreme winds and flooding rainfall events that have devastating effects on society and the environment in U.S. coastal regions. The broader impacts will also extend to educational goals, as graduate students will be trained during this research.