Eddy Detection in HF Radar-Derived Surface Currents in the Gulf of Naples

Abstract

Submesoscale eddies play an important role in the energy transfer from the mesoscale down to the dissipative range, as well as in tracer transport. They carry inorganic matter, nutrients and biomass; in addition, they may act as pollutant conveyors. However, synoptic observations of these features need high resolution sampling, in both time and space, making their identification challenging. Therefore, HF coastal radar were and are successfully used to accurately identify, track and describe them. In this paper we tested two already existing algorithms for the automated detection of submesoscale eddies. We applied these algorithms to HF radar velocity fields measured by a network of three radar systems operating in the Gulf of Naples. Both methods showed shortcomings, due to the high non-geostrophy of the observed currents. For this reason we developed a third, novel algorithm that proved to be able to detect highly asymmetrical eddies, often not properly identified by the previous ones. We used the results of the application of this algorithm to estimate the eddy boundary profiles and the eddy spatial distribution.

Wind Direction Data from a Coastal HF Radar System in the Gulf of Naples (Central Mediterranean Sea)

“…HFrs are currently recognized as powerful monitoring systems due to their ability to provide simultaneous measurements of currents, waves and wind directions [63,64]. The skill of these systems to resolve the surface current and wave field is well proven [6,7,[26][27][28][29][30][31][32][33][34], and this has been pivotal in the implementation of observation systems [2] and in operational applications [1,65]. However, the use of backscattered echoes to determine the direction of wind blowing over the sea surface is relatively underexplored for SeaSonde systems [20,21].…”

“…HFr measurements are provided by a CODAR network managed by the Department of Science and Technologies of University Parthenope [26]. Previous works were focused on the validation and application of surface currents [27][28][29][30] and wave data [31][32][33][34]. The GoN is located in a complex coastal area with very peculiar local factors influencing the wind field, among which an intricate coastline and a complex geomorphology [35,36].…”

Editorial for the Special Issue “Remote Sensing of the Oceans: Blue Economy and Marine Pollution”

“…Detection of targets such as marine raft aquaculture, moving vessels, and the shoreline [1][2][3]; • Observation of spatio-temporal pattern of oil spills and coastal marine litter [4][5][6]; • Study of natural sea processes, including typhoon-induced storm surges, sub-mesoscale eddies and migration of the along-slope counter-flow [7][8][9]; • Analysis of scattering and spectral properties of the sea surface [10,11].…”

“…Most of the study exploited satellite data, including microwave-synthetic aperture radar (SAR) imagery collected in single-, dual-and quad-polarimetric imaging modes, radar altimeters [1][2][3][4][5]7,11], and optical-spin-scanning radiometers and spectroradiometers [7,8]. Other studies used airborne or shore-based sensors, including UAV cameras and high-frequency (HF) coastal radars [6,9]. Numerical tools and simulations were also considered in [3,4,[8][9][10], while in-situ information was exploited in [5,7,8].…”

“…Other studies used airborne or shore-based sensors, including UAV cameras and high-frequency (HF) coastal radars [6,9]. Numerical tools and simulations were also considered in [3,4,[8][9][10], while in-situ information was exploited in [5,7,8].…”