Evaluating Radial Current Measurements from CODAR High-Frequency Radars with Moored Current Meters*

Abstract
The performance of a network of five CODAR (Coastal Ocean Dynamics Application Radar) SeaSonde high-frequency (HF) radars, broadcasting near 13 MHz and using the Multiple Signal Classification (MUSIC) algorithm for direction finding, is described based on comparisons with an array of nine moorings in the Santa Barbara Channel and Santa Maria basin deployed between June 1997 and November 1999. Eight of the moorings carried vector-measuring current meters (VMCMs), the ninth had an upward-looking ADCP. Coverage areas of the HF radars and moorings included diverse flow and sea-state regimes. Measurement depths were ∼1 m for the HF radars, 5 m for the VMCMs, and 3.2 m for the ADCP bin nearest to the surface. Comparison of radial current components from 18 HF radar–mooring pairs yielded rms speed differences of 7–19 cm s−1 and correlation coefficients squared (r2) in the range of 0.39–0.77. Spectral analysis showed significant coherence for frequencies below 0.1 cph (periods longer than 10 h). At highe... Abstract The performance of a network of five CODAR (Coastal Ocean Dynamics Application Radar) SeaSonde high-frequency (HF) radars, broadcasting near 13 MHz and using the Multiple Signal Classification (MUSIC) algorithm for direction finding, is described based on comparisons with an array of nine moorings in the Santa Barbara Channel and Santa Maria basin deployed between June 1997 and November 1999. Eight of the moorings carried vector-measuring current meters (VMCMs), the ninth had an upward-looking ADCP. Coverage areas of the HF radars and moorings included diverse flow and sea-state regimes. Measurement depths were ∼1 m for the HF radars, 5 m for the VMCMs, and 3.2 m for the ADCP bin nearest to the surface. Comparison of radial current components from 18 HF radar–mooring pairs yielded rms speed differences of 7–19 cm s−1 and correlation coefficients squared (r2) in the range of 0.39–0.77. Spectral analysis showed significant coherence for frequencies below 0.1 cph (periods longer than 10 h). At highe...