Characterization of ocean surface current properties from single site HF/VHF radar

Abstract

Surface current mapping from HF/VHF coastal radars traditionally requires at least two distant sites. Vector velocities are estimated by combining the radial velocity components measured by the radars. In many circumstances (e.g., failures, interferences, logistics constraints), such a combination is not possible by lack of data from one station. Two methods are evaluated to get information on surface circulation from a single site radar: the Vectorial Reconstruction Method (VRM) for current vector mapping and the Vortex Identification Method (VIM) for detecting eddy-like structures. The VRM assumes a non-divergent horizontal surface current, and the VIM analyzes radial velocities and their radial and orthoradial gradients. These two methods are tested on modeled and measured data sets in the Northwestern Mediterranean Sea where both high-resolution ocean circulation model and radar campaigns are available. The VRM performance is strongly limited by the divergence-free hypothesis which was not satisfied in our real data. The VIM succeeded in detection of vortex in the Gulf of Lions and from an operating single site radar located on the Provence coasts in summer

Assimilation of HF radar surface currents to optimize forcing in the northwestern Mediterranean Sea

“…By convention its sign is positive (negative) for velocity going toward (away from) the station. High positive values in the PEY radial component are a distinct signature of the coastal current (Marmain et al, 2011). The model clearly underestimates the intensity of the current radial components, and the position of the maximum seems slightly shifted off-shore.…”

Construction of sea surface current vectors using a single HF radar: A theoretical study

“…Marmain et al. 23 proposed a vortex structure identification method (VIM) by directly establishing an empirical relationship between an idealized vortex symmetry model and radial current. While the VIM can directly calculate the structure of the vortex flow field from the radial current, however, it uses an idealized empirical model, and the estimated current vector field differs significantly from the actual field.…”

The multistatic oceanographic HF radar network in Toulon

“…The Mediterranean Institute of Oceanography (MIO) and the University of Toulon have been operating for one decade a network of HF radar systems (manufactured by WERA Helzel Messtecknik) for the daily monitoring of surface currents in the coastal area of Toulon (e.g. [1], [2]). This network is being currently upgraded in the framework of the EU Interreg Maritimo program SICOMAR-PLUS and, as of January 1st, 2019, it is maintained operational by the company Degréane Horizon.…”