An assessment is made of the dominant process governing the circulation in a 30x30 area of the coast of Ancona, where surface current velocity vectors have been obtained using an HF Coastal Dynamics Applications Radar (CODAR). Throughout one year of measurements (September 1997 - August 1998) some evidences of the surface dynamics in this area have been analysed. In winter the surface circulation is intensified and mainly concentrated close to the coast (within 15÷20 km from it); in the spring and summer months, surface currents are much weaker, and between summer and autumn, a single cyclonic eddy further offshore often dominates surface circulation. In this paper the CODAR velocity data have been used to compute the surface vorticity and divergence fields offshore Ancona. The vorticity field is shown to have generally well defined patterns that are trackable in time despite the influence of winds and tides. The divergence field tends to be more variable spatially and temporally. However, it is an important descriptor of the irrotational motion and it is used, together with vorticity of the rotational flow, to see the regional dynamics. In order to better visualize the rotary nature of the semidiurnal currents, over the whole first year of working, these are presented in terms of ellipses. The direction of the semi-major axis shows a preferential behaviour parallel to the coastline over all the studied area.
An assessment of surface dynamics observed offshore Ancona with HF Radar
Grilli F;
2002
Abstract
An assessment is made of the dominant process governing the circulation in a 30x30 area of the coast of Ancona, where surface current velocity vectors have been obtained using an HF Coastal Dynamics Applications Radar (CODAR). Throughout one year of measurements (September 1997 - August 1998) some evidences of the surface dynamics in this area have been analysed. In winter the surface circulation is intensified and mainly concentrated close to the coast (within 15÷20 km from it); in the spring and summer months, surface currents are much weaker, and between summer and autumn, a single cyclonic eddy further offshore often dominates surface circulation. In this paper the CODAR velocity data have been used to compute the surface vorticity and divergence fields offshore Ancona. The vorticity field is shown to have generally well defined patterns that are trackable in time despite the influence of winds and tides. The divergence field tends to be more variable spatially and temporally. However, it is an important descriptor of the irrotational motion and it is used, together with vorticity of the rotational flow, to see the regional dynamics. In order to better visualize the rotary nature of the semidiurnal currents, over the whole first year of working, these are presented in terms of ellipses. The direction of the semi-major axis shows a preferential behaviour parallel to the coastline over all the studied area.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
