Improving HF Radar Estimates of Surface Currents Using Signal Quality Metrics, with Application to the MVCO High-Resolution Radar System

Abstract

Estimates of surface currents over the continental shelf are now regularly made using high-frequency radar (HFR) systems along much of the U.S. coastline. The recently deployed HFR system at the Martha's Vineyard Coastal Observatory (MVCO) is a unique addition to these systems, focusing on high spatial resolution over a relatively small coastal ocean domain with high accuracy. However, initial results from the system showed sizable errors and biased estimates of M 2 tidal currents, prompting an examination of new methods to improve the quality of radar-based velocity data. The analysis described here utilizes the radial metric output of CODAR Ocean Systems' version 7 release of the SeaSonde Radial Site Software Suite to examine both the characteristics of the received signal and the output of the direction-finding algorithm to provide data quality controls on the estimated radial currents that are independent of the estimated velocity. Additionally, the effect of weighting spatial averages of radials falling within the same range and azimuthal bin is examined to account for differences in signal quality. Applied to two month-long datasets from the MVCO high-resolution system, these new methods are found to improve the rms difference comparisons with in situ current measurements by up to 2 cm s 21 , as well as reduce or eliminate observed biases of tidal ellipses estimated using standard methods.

HF Radar Activity in European Coastal Seas: Next Steps toward a Pan-European HF Radar Network

“…A number of previous works have focused on defining optimum threshold levels (e.g., Lorente et al, 2014Lorente et al, , 2015a but there is still no worldwide consensus. Current initiatives intend to use non-velocity-based metrics related to the characteristics of the received signal (radial and total coverage analysis, hardware status, quality of the received signal) in order to implement advanced quality controls (Kirincich et al, 2012).…”

Physical controls on copepod aggregations in the Gulf of Maine

“…Autonomous gliders and other AUVs are able to map three-dimensional physical and biological fields rapidly in time and space (Rudnick et al (2004), Baumgartner and Fratantoni (2008)). Surface currents can be mapped from shore by high-frequency radar on scales smaller than 1km (Kirincich et al (2012)). Moving forward, using this new technology may be the best way to solve this important problem.…”

Some considerations about coastal ocean observing systems

“…Used together or with additional sensors such as HF radar, winds, and so forth, satellite SSTs and chlorophyll can be used for a wide array of applications in the coastal oceans. Representative studies include understanding the coupling of coastal SSTs with wind stress (Chelton, Schlax, and Samelson 2007), approximating nutrient fluxes into sensitive coastal areas (e.g., Beman, Arrigo, and Matson 2005), or estimating fluxes of heat across the inner part of the continental shelf (Kirincich, de Paolo, and Terrill 2012). Access to daily or higher-frequency estimates on spatial scales as small as 1 km make both SST and chlorophyll an immensely useful data product for coastal studies.…”

“…Typical radars report results on time intervals of 0.25-1 hour, again [75, 3 depending on operating frequencies. Estimates of velocity accuracy vary widely (Emery et al 2004;Ullman and Codiga 2004;Kohut et al 2006;Paduan et al 2006), but it appears, based on very careful analysis, that perhaps 6 cm s −1 , as a root mean square difference relative to in situ ADCP (Acoustic Doppler Current Profiler) near-surface current estimates, might be a realistic minimum with current capabilities (Ohlmann et al 2007;Kirincich, de Paolo, and Terrill 2012). HF radar systems have reached a point where they are routinely employed to monitor coastal circulation around highly populated areas (e.g., Harlan et al 2010).…”