Using Multifrequency HF Radar to Estimate Ocean Wind Fields

See also ADM001850. Presented at the IEEE International Geoscience and Remote Sensing Symposium (25th) (IGARSS 2005), held in Seoul, Korea on 25-29 Jul 2005. Published in the Proceedings of the IEEE International Geoscience and Remote Sensing Symposium (25th) (IGARSS 2005), 2005. Prepared in cooperation with Stanford University, Stanford, CA, and University of Michigan, Ann Arbor, MI. Prepared in collaboration with Naval Postgraduate School, Monterey, CA. Sponsored in part by National Oceanic and Atmospheric Administration (NOAA) under grant no. NA-160C2936. The original document contains color images.

As indicated by growing deployments world wide, HF radar is an increasingly important tool for mapping coastal surface currents. It has been used to determine wind direction. We report further on the ability of multifrequency HF radar to measure the vector wind field and the impact that such measurements have on the measurement of wind fields over coastal land and sea. In this study, we use a year-long 2000-2001 data set collected over Monterey Bay, California. Our Multifrequency Coastal Radars (MCRs) operated at 4.8, 6.8, 13.4 and 21.8 MHz, measuring currents at effective depths of about 2.5, 1.8, 0.9 and 0.6 m respectively. For training and validation we use the M-1 buoy deployed by Francisco Chavez at the Monterey Bay Aquarium Research Institute. Validation results over the year time span indicate standard errors of prediction of 1.7 m/s for wind speed and 25 for direction with biases of 0.1 m/s and 0.3 respectively. We discuss limitations of this technique at low wind speeds. Finally, we present a regional wind field assimilating HF radar estimates and demonstrate the beneficial impact of multifrequency HF radar, wind field measurements, on estimation of the coastal wind field over both land and sea.