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Description:
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Understanding the structure of the coastal internal boundary layer (IBL ) during the landfall of a tropical cyclone has important ramifications on operational forecasting , structural design , and post -storm damage assessment . Despite these important issues , it is unclear how the structure of the IBL evolves at the coastline on micro - and meso -scales during a landfalling hurricane . Knowledge of the vertical kinematic structure within tropical cyclones over water has improved greatly through aircraft reconnaissance missions and the advent of GPS dropsondes and the Stepped Frequency Microwave Radiometers . Unfortunately , reconnaissance and research aircraft are limited to over -water missions resulting in a poor understanding of vertical kinematic structure near the coastal interface where changes in IBL structure are expected due to changes in coastal geometry and surface roughness . Additionally , IBL structure may evolve due to the passage of convective precipitation and associated downdrafts .
A unique observational dataset was collected from the coastal transition zone in the onshore flow region of Hurricane Frances (2004 ) over Cape Canaveral , FL . Single - and dual -Doppler radar data collected by the Shared Mobile Atmospheric Research and Teaching radars provide the ability to discern horizontal and vertical mean IBL structure over a complex coastal interface while assessing the influence of a variable underlying surface and the passage of transient convective wind gusts . Additional wind speed data were collected by a meso -network of surface towers operated by the Cape Canaveral Air Force Station and Kennedy Space Center along with a portable surface tower deployed by Texas Tech University .
Radar and tower data analyses reveal that IBL mean structure over the Cape Canaveral remains quite consistent during the landfall of Hurricane Frances , though IBL growth is suppressed when compared to empirical growth models . Additionally , transient convective gusts commonly perturb the mean structure at the top of the IBL , though the higher momentum associated with these gusts is typically not able to descend to the surface within an established IBL . |