HF Remote Sensing - The CORI System

High quality currents data are required in order to provide reliable results in a variety of oceanographic applications, such as ocean circulation models, prediction of the movement of contaminants (oil spills), sea rescue operations, prediction of the stress due to currents and wave action on coastal and near-shore structures, ships navigation, commercial and recreational fishery. High frequency radar (HF radar) systems are by now a well-tested technique to provide accuracy surface current maps in near coastal environments. HF radars are capable of producing current vector maps of the coastal zone over spatial scales ranging from hundreds of meters to hundreds of kilometres and on time intervals from tens of minutes to days. The measurement is based on the fact that electromagnetic radiation in the 3- to 30-MHz range scatters strongly (Bragg scattering) from ocean surface gravity waves. The returned energy spectrum thus indicates movement of ocean surface gravity waves with a wavelength of half the radar-transmitted wavelength in directions either toward or away from the HF radar site. Subtraction of the theoretical phase velocity of the ocean waves gives radial current velocities (hereafter referred to as radials). Multiple radars are typically deployed so there is enough angular separation to resolve both the north–south and east–west velocity components.

In the framework of the CORI (Prevention and Management of Sea Originated Risks to the Coastal Zone) INTEREG IIIB ARCHIMED 2000-2006 programme, monitoring of the surface currents on the east coast of Limnos Island began in 2009. It uses a WERA HF Remote Sensing system (Helzel Messtechnik GmbH, Germany ) transmitting electromagnetic waves in the range of 6 - 30 MHz to measure surface current velocities and optionally ocean wave height and wind. The shore-based antennas provide continuous temporal and broad spatial surface current observations, facilitating the delivery of data in near real-time and in high spatial and temporal resolution.

HF radar data are available, with some data gaps, from November 2009 till the present here.

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