| The purpose of this dissertation research is to determine the utility of using a multi-frequency high frequency (BF) radar operating at decameter wavelengths to obtain estimates of the friction velocity in the sea and to relate these estimates to measurements obtained on the air side of the interface. This is accomplished through the detection of changes in the phase velocity of surface gravity waves induced by flow in the water.; In situ measurements of this sort are difficult to obtain due to the harsh environment which exists at the air-sea interface, and are usually restricted to point measurements obtained at moored instrument platforms or onboard ships. The use of the HF radar to obtain such information bypasses these difficulties and provides synoptic coverage in near real time.; In this work, the Levenberg-Marquardt method of non-linear least squares is used to determine the near surface current profile based on a theoretical model of the effect of the current on the phase velocity of a surface gravity wave. The results of this analysis are compared to in situ measurements of wind velocity and calculations of friction velocity obtained by the Innovative Coastal-ocean Observing Network group as part of the Monterey Bay Aquarium Research Institute (MBARI) Ocean Observing System Upper-water-column Science Experiment over Monterey Bay, California. In particular, a comparison is made with the Flux buoy measurements and calculations of the Boundary Layer Studies Group of the Naval Postgraduate School and the MBARI M1 buoy measurements. In addition, several methods to determine the variance in the HF data are tested to ensure data quality, and the adequacy of the HF frequencies for friction velocity retrieval are evaluated.; The results show that our estimates of the friction velocity compare well with in situ measurements during moderate wind conditions, in excess of about 5 m/s and less than about 12 m/s. Further evaluation of the present method for obtaining friction velocities under higher wind conditions is warranted. In addition, development of a higher order wave-current interaction theory and/or wave boundary layer flow theory would enhance this capability. |
