Multifrequency HF radar observations of surface currents: measurements from different systems and environments

The authors present three aspects of current HF radar research. First, they examine the consistency of measurements by HF ground wave radars with different designs, but operating on the same physical principles. This is done using data from the commercially available SeaSonde (Codar Ocean Systems) and from the Multifrequency Coastal Radar (MCR), which is a research system. Data from the two systems are compared for co-located units at Santa Cruz and Moss Landing CA on Monterey Bay. They conclude that the two systems make current-vector-field measurements that are consistent to an accuracy of better than 10 cm/s and that the data from two such systems can be integrated to form reliable composite current maps. Second, they present results from an air-sea interaction investigation using the MCR systems on Monterey Bay during 1997 and 2000. We show that near surface currents are correlated with the wind with correlation coefficients 0.6 and are rotated 35 to 45/spl deg/ with respect to the wind in the sense of the Ekman spiral. They also show results of near shore observations on Lake Michigan during the EEGLE campaign of 2000. These measurements show the capability of HF radars to operate over fresh water.