Use of real-time high frequency radar observations to estimate winds that can be used as part of on-line objective analyses in California coastal regions

The research to be described synthesizes several ongoing activities: 1) Remote radar sensing and real-time WWW display of ocean surface currents over Monterey Bay, 2) Multi-Channel, high frequency Radar (MCR) observations of near-surface ocean currents and shear over Monterey Bay, 3) Development of a statistical methodology for deriving winds from the MCR observations of near-surface current shear, and 4) Real time, web based objective wind analyses over both the Monterey and San Francisco Bay regions. The fact that current shear is largely the result of wind stresses suggests that for wind speeds above approximately 3 m/s the information necessary for estimating wind speed and direction should be available in the MCR observations. In principle, the friction velocity in the water can be determined from the current shear and related to the atmospheric friction velocity and winds. In practice, the direct approach has proven quite difficult, but statistical methods have given promising results. This paper will describe the most promising statistical approach, non-linear least-squares regression, and how the results obtained have been integrated into an objective wind analysis scheme to produce and display wind analyses over a region that includes both Monterey and San Francisco Bays. The analyses are performed on a grid with 1-km spacing and displayed with 3-km resolution. This extends existing analyses covering the two Bays (Monterey and San Francisco) separately, and adds the information gleaned from radar current measurements. The integration of data from different sources will be described. The radar and statistical methodologies will be discussed, along with their effect on the wind field analyses.