Characterization of Synthetic Aperture Radar Image Features of the Ocean as a Function of Wind Speed and High Frequency Radar Products
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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Assessment of coastal ocean conditions is valuable for both military and civilian operations. Remote sensing of those conditions can be even more valuable, particularly in the case of all-weather sensor types. The potential for better understanding of ocean conditions through the combination of remote sensing results was recognized here with the focus on SAR imagery and High Frequency HF radar-derived surface currents. The hypothesis that combining remote sensing products may improve results was tested using SAR imagery and available HF radar surface current maps along central California. Data were obtained from 2007-2010 when the network of HF radar stations was operating relatively continuously. Over the same time period, 780 archived SAR images were identified and, of those, 31 images were chosen for detailed assessment by identifying representative images under weak, moderate, and strong wind conditions. As expected, wind strength played a dominant role in determining the physical processes visible in the SAR imagery. Moderate wind speed of 2-4 ms exhibited the most obvious ocean-related processes and the best correlation with features in the HF radar surface current maps. Surprising is the discovery that oceanographic features in the SAR imagery represent recent history of tracer advection over hours to days. As such, individual hourly, surface-current snapshots are not, perhaps, the best product for comparing with those features. Features in the daily-average currents, for example, appear more highly correlated with features in SAR imagery under moderate wind conditions.
- Active and Passive Radar Detection and Equipment