Upwelling systems at (sub)mesoscale resolution

X. Capet (IO, Universidade of Sao Paulo)
J.C. McWilliams (IGPP,University of California, Los Angeles)

Fronts and eddies seen in satellite imagery attest to the turbulent behavior of upwelling systems and have received widespread attention because they exert a significant influence on the mean state of their respective systems. Sigma-coordinate regional models are a priori well-suited tools to quantify this influence. However they pose a challenge in terms of diagnostics because horizontal and vertical tracer fluxes are difficult to disentangle from each other. In particular, it has proven difficult to estimate vertical buoyancy fluxes (wb, mean and eddy) and their divergence in configurations with realistic bathymetry. wb are key quantities because they provides insight into the origin of turbulent activity (they represent conversion term between potential and kinetic energy) and restratification processes (through their z-derivative).

In this talk we propose and evaluate a new method for accurately computing wb-type terms. Results are discussed in the context of the seasonal variability of the California Current System.