Observations and Simulation of a Bottom Ekman Layer on a Continental Shelf

A numerical model was used to simulate the bottom Ekman layer of a continental shelf region. The basis for the model was the Mellor and Yamada level 2« turbulence closure scheme. Conservation equations for momentum, turbulent kinetic energy, and turbulent length scale were utilized in the model. The model was used to simulate data taken from a Cyclesonde mooring on the Peruvian continental shelf in May 1976 as part of the Joint II Coastal Upwelling Ecosystems Analysis program. The Cyclesonde provided mean horizontal velocity, temperature, salinity, and pressure data. An intense poleward undercurrent drove the bottom flow regime. The most striking feature of the data was the clockwise Ekman veering of velocity vectors as the bottom was approached. A 48-hour period was chosen for the model simulations. The vertical profile of speed (48 hours mean) simulated by the model fell within the error bars of the data. The corresponding Ekman spiral display of the model results also showed good agreement with the observati. ons.