Mesoscale data assimilation studies in the Middle Adriatic Sea

Abstract

In this paper we describe a mesoscale data assimilation experiment in the Middle Adriatic Sea. In order to perform dynamical forecasts we provide a quasigeostrophic numerical model with a set of initial fields regularly gridded via an objective analysis technique. Maps of this initial condition show a surface intensified jet meandering around a cyclonic eddy at the thermocline and deep levels. We dynamically forecasted the flow evolution for 30 days after initialization. The time scale of the variability is of the order of a few weeks and the cyclonic vortex seems to be locked to the topography. A set of numerical experiments with different initial bottom boundary conditions, with and without topography, are made to explore the influence of the topographic constraint on the mesoscale flow evolution. As expected the influence of the topography on the dynamical evolution of the flow is very strong and it confines the jet-cyclone along the bathymetric contours, strengthening the flow. On the other hand the flow is not sensitive to changes in the density bottom initial condition. Finally we analyze the energy and vorticity fields of the 1-month dynamical forecast experiment. It is concluded that a local frontogenetic process consisting of jet strengthening and cyclone development occurs and that available gravitational energy is converted into kinetic energy during the process.