Coastal Radar Observations of Wind Induced Vortices in Microtidal Regimes
Abstract
The coastal radar represents a new means of autonomous observation which comes as a complement to the traditional measures, and which allows to obtain maps of the surface circulation of the ocean. Two examples of radar campaign in the North Western Mediterranean are presented: in the Gulf of La Spezia (Ligurian coast, coverage 20km, resolution 300m) with a VHF radar and in the Gulf of Lions with a HF-radar (French coast, coverage 100km, resolution 3km). While the coastal circulation of the North-Western Mediterranean Sea is dominated by the cyclonic large Northern current, the microtidal onshelf circulation is mostly driven by intense forcings, i.e. strong wind conditions and river discharge. The sensitivity of the coastal flow to the wind forcing both of mesoscale and sub-mesoscale (Rossby radius scale) has been investigated using surface currents measurements and process oriented modelling. In the experiment in the Gulf of La Spezia, a comparison is made between the radar observations and data from surface drifter clusters, and a preliminary study of the circulation based on the analysis of the atmospheric forcing is presented. The results are highly encouraging for practical applications regarding transport and tracer spreading (biological or pollutant releases). In the Gulf of Lions case, the generation and driving mechanisms of observed sub-mesoscale eddies are analysed by means of a numerical model (Ifremer MARS3D) , from an idealized to a more realistic configuration. The relative influences and interaction of various possible forcings are analysed: wind, onshelf intrusion of the Northern slope current, Rhone river plume front, complex bathymetry and freshwater buoyancy effects.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFMOS31E..03M
- Keywords:
-
- 4255 Numerical modeling (0545;
- 0560);
- 4262 Ocean observing systems;
- 4512 Currents;
- 4520 Eddies and mesoscale processes