COMPARISON OF OVER-THE-HORIZON RADAR SURFACE-CURRENT MEASUREMENTS IN THE GULF-OF-MEXICO WITH SIMULTANEOUS SEA TRUTH

On June 14, 1995, the U.S. Navy's Relocatable Over-the-Horizon Radar ( ROTHR) west of Corpus Christi, Texas, mapped the radial component of o cean surface current with 15-km resolution over a 230,000-km(2) area i n the Gulf of Mexico. Concurrently, an oceanographic research vessel m easured near-surface currents within part of the area illuminated by t he radar, providing an opportunity to compare radar-derived surface cu rrents with in situ sea truth. The R/V Gyre, operated by Texas A&M Uni versity, twice traversed the Gulf of Mexico Loop Current while measuri ng current vectors with an acoustic Doppler current profiler (ADCP). W e compared radar-derived currents with currents measured in the upperm ost ADCP bin (centered at IO-m depth). Lf only radar data exceeding a quality threshold are considered, the rms difference in the radial cur rents measured by the two techniques is 27 cm s(-1). This difference m ost likely reflects the different sampling employed by these instrumen ts, as well as unremoved ionospheric biases in the radar measurements.