A Satellite and Model Study of the Circulation in the SE Pacific

P. TED STRUB; RICARDO P. MATANO; ELBIO D. PALMA; CORINNE JAMES

Wrest Point, Hobart, Tasmania, Australia

Congreso; NASA 2007 Ocean Surface Topography Science Team; 2007

NASA

Aspects of the surface circulation of the SE Pacific are described using two primary typesof satellite data: sea surface temperature (SST) fields from the Pathfinder (1985-2003)and Reynolds (1982-2005) data sets; and sea surface height (SSH) fields from the JPLalongtrack SLA and the gridded AVISO SSH and velocity data sets (1993-2003). Resultsfrom the satellite analyses are compared to results from numerical simulations of thecirculation. These are higher-resolution regional numerical simulations, nested within alower-resolution global model. Two versions of the regional models are analyzed, onewith boundary conditions forced by the global model and another with only regionalwind forcing. This allows us to investigate the effect of the equatorial dynamics on thecirculation off Peru and Chile. The time scales of interest include both the seasonal cycleand the interannual variability, which is dominated by the ENSO phenomenon. Thealtimeter data reveal both annual and semiannual periodicity in the seasonal cycle, alongwith a strong El Niño SSH signal along Peru and Chile. The model data also show bothannual and semiannual periodicities in SSH, with a nearshore annual signal contributedprimarily by the distant equatorial signal. Subsurface model fields indicate a deepdisplacement of isotherms in July and a shallow displacement in January, both due todistant equatorial forcing. Further differences in the response to distant and regionalforcing will be presented.