Numerical modeling of seasonal and mesoscale hydrography and circulation in the Mexican Central Pacific

Based on results from a ROMS numerical model, the dynamics of the Mexican Central Pacific was studied during three years (2003-2005). The model reproduces the mean and seasonal variability of sea surface temperature, as well as mesoscale eddies and meanders from satellite observations. The model adequately represents the main currents in the region: California Current, Mexican Coastal Current, and Gulf of California currents. The Gulf of California currents are linked to the intensification of the Mexican Coastal Current and interact in such a way that the lateral shear generates eddies at the entrance to the Gulf of California. The mesoscale eddies were found to have a depth of 200 m. The eddies generated in the area (internal Rossby radius of deformation, Rd = 40 km) had a diameter L of 300 km, an orbital speed of 20-30 cm s(-1), and a westward translation speed of similar to 4 cm s(-1). Eddies are considered from intermediate to big (L approximate to 7.5 Rd, Ro << 1), show geostrophic dynamics, and present a westward drift due to Coriolis variation with latitude (beta effect). The size of the eddies seems to be related to the weakening of the meridional component of wind stress during the North American monsoon.