AN ASSESSMENT OF OCEANIC LARGE SCALE VERTICAL VELOCITIES IN THE TROPICAL ATLANTIC : AN ANALYSIS OF THE VORTICITY BUDGET
Event: 2020 Ocean Surface Topography Science Team Meeting (virtual)
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Forum only
Contribution: PDF file
The linear vorticity balance (LVB), βv = f∂w/∂z is used to know to what extent it can describe the large-scale dynamics of the vertical velocity of the Atlantic thermocline, in simulations of regional simulations NEMO general circulation ocean model averaged over a period of 25 years (1980-2004). The balance dominates the circulation at the scale greater than a few degrees, away from the coasts and the mixing layer, in the thermocline of the subtropical and tropical gyres. The LVB is valid there with less than 10% error. The non-linearities in the dynamics are important in specific regions of the western and eastern boundary currents and invalidate the LVB. For example, advection of vorticity is always strong there, and the terms of torsion, horizontal and vertical diffusion are regionaly important. The reconstruction of the vertical velocity (w) by integration of the LVB from 1000 meter depth upwards (w(1000m)=0) gives satisfactory results in regions where the LVB was verified.