Numerical Study of Time-Dependent Wind Forcing Off the West Coast of Portugal,

摘要

A process-oriented numerical study of time-dependent wind forcing is conductedusing a ten-layer, beta-plane, primitive equation ocean model to provide insight into mesoscale eddy generation and duration off the west coast of Portugal from 1987 to 1988. The wind forcing used was derived from synoptic surface pressure analyses off Lisbon, Portugal. Results obtained show that eddies generated during the coastal upwelling season (generally occurring during the spring and summer) decay during the winter. Only cyclonic eddies form during the 1987 and 1988 upwelling seasons. The eddies are generated through a combination of barotropic and baroclinic instability mechanisms. Since the wind forcing of the five-month-long 1987 upwelling seasons. The eddies are generated through a combination of barotropic and baroclinic instability mechanisms. Since the wind forcing of the five-month-long 1987 upwelling season generates larger and stronger eddies than the wind forcing of the seven-month-long 1988 upwelling season, eddy characteristics appear to be more influenced by the characteristics (e.g., intensity, duration and frequency of occurrence) of the wind forcing than by the total length of the upwelling season. This study affirms the importance of wind stress forcing to the overall surface circulation and eddy generation in the coastal ocean regime off the west coast of Portugal.