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Highly Temporal-Spatail Coastal Current Measurements by DBF-VHF Radar


The escalating interest in the coastal ocean has created a requirement for the acquisition of high-quality surface current data to improve the understanding of surface circulation, and to study their impact on a broad spectrum of societal and environmental issues. These environmental issues relating to the coastal ocean are increasingly difficult to manage with respect to water quality over large areas, which is directly related to submesoscale to mesoscale variability in the spatially-evolving surface current fields. Inference of these spatial patterns is difficult from single-point measurements such as moorings or drifters, which propagate away from divergent flow regimes. One approach that effectively measures spatially-evolving surface current fields in near-real time is the VHF/HF Doppler radar technique, providing spatial context. A promising method that has evolved over the past four decades is the Doppler radar technique originally described by Crombie (1955), who observed that the echo Doppler spectrum consisted of distinct peaks symmetrically positioned about the radar frequency. The concept is based on the premise that pulses of electro-magnetic radiation are backscattered from the moving ocean surface by resonant surface waves at one-half of the radar wavelength or "Bragg waves". Stewart and Joy (1974) showed that the displacement of the Doppler peaks from their expected positions is related to the underlying current flow modifying the phase speed of the surface waves.

This project develops new type of VHF radar and analyzing algorithms for providing useful coastal information.

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Shinichi Takumi Sakai, Masafumi Matsuyama, Takaki Tbono, Takao Shimizu, CRIEPI