|Institution:||Texas Tech University|
|Keywords:||Automated surface observing system; StickNet; Tropical cyclone boundary layer; Velocity azimuth display; Weather surveillance radar-1988 Doppler; Wind speed reduction factor|
|Full text PDF:||http://hdl.handle.net/2346/63660|
Atmospheric scientists and wind engineers have been adjusting tropical cyclone boundary layer (TCBL) lower tropospheric winds to the surface for several decades. Empirical relationships derived from reconnaissance aircraft, Global Positioning System (GPS) dropwindsonde, Stepped Frequency Microwave Radiometer (SFMR), and available moored buoy and ship wind measurements have typically been used to estimate surface wind conditions over the ocean. However, a significant data gap has existed at landfall and the debate over which method is appropriate to adjust TCBL lower tropospheric winds over land is unknown. The coastal network of Weather Surveillance Radar-1988 Doppler (WSR-88D) systems run by the National Weather Service (NWS) provides continuous coverage of tropical cyclones (TC) at landfall (barring power loss) and a unique opportunity to fill in the data gap over land. WSR-88D Velocity Azimuth Display (VAD) wind profiles were generated in landfalling TCs between the years of 1995-2012 to first characterize the vertical evolution of the horizontal, radial, and tangential wind profiles in a storm-relative framework. Azimuthal and radial dependencies were examined along with the influence of onshore versus offshore regimes and site-relative surface terrain on the surface-layer of the VAD wind profiles. Automated Surface Observing System (ASOS) wind measurements collected during VAD analysis periods were retrieved from the National Climatic Data Center (NCDC) and standardized to common reference exposures depending on the upstream fetch. ASOS standardized wind measurements, along with maximum 3-second gust wind speed measurements, were examined relative to the VAD wind profiles. Several wind adjustment techniques were evaluated to test the applicability of conventional methods used in building codes. New empirical wind relationships were also developed in an effort to improve surface wind estimation over land at landfall. The azimuthal and radial prediction accuracy of the newly developed empirical relationships was evaluated using historical Texas Tech University (TTU) StickNet deployments. StickNet wind speed measurements were also standardized to a common measurement height and reference exposure to properly evaluate the empirical wind relationships. Advisors/Committee Members: Smith, Douglas A. (committee member), Kang, Song-Lak (committee member), Lorsolo, Sylvie (committee member), Schroeder, John L. (Committee Chair).