Advanced Ocean Modelling: Using Open-Source Software

4.5 Exercise 18: Coastal Upwelling and Downwelling 117Fig. 4.15 Exercise 18. Downwelling scenario. Snapshots of the density field, and cross-shore andalongshore components of horizontal velocity after 3 days of simulationEkman layer. Notice that the bottom Ekman layer attains a thickness of 10–20 m inthis simulation. During the course of the downwelling event, the coastal sea levelgradually rises by 20 cm (not shown). The resultant barotropic offshore pressuregradient is the principal driver of the geostrophic alongshore jet.4.5.7 Additional Exercise for the ReaderExplore the density structure and flows resulting from oscillatory wind-stress forcing,prescribed by Eq. (4.21), with a period of 4 days for a total simulation time of20 days. Note that the average wind stress is zero, so that, without diffusion effects,the final density distribution should be the same as the initial distribution. Overtime, however, we anticipate that diffusion causes residual lateral density gradientsand associated geostrophic flows.