HR: 1330h
AN: OS32B-0245    [PDF]
TI: Modeling wetting and drying process in San Francisco Bay using the Princeton Ocean Model
AU: * Uchiyama, Y
EM: uchiyama@ce.berkeley.edu
AF: University of California at Berkeley, 631 Davis Hall, Berkeley, CA 94720 United States
AB: Wetting and drying scheme (WDS) is developped to incorporate into the Princeton Ocean Model (POM, Blumberg and Mellor, 1987), which is based upon a sigma-coordinate system. Using a length scale D to characterize the bed topography or the roughness height, WDS scans each grid cell every 2DH external mode time step. If the depth at the center of each grid cell becomes less than D, the cell is considered potentially dry. This grid cell is effectively dry if the depths of all four adjacent cells are also less than D, and subsequently removed from the computational domain. The water elevation retained on the grid cell is set to the corresponding value at the end of the time step, and used for next flooding. If at least one water depth around the four sides of the grid cell is still greater than D, the cell is left in the computational domain to be scanned again by WDS at the next time step. Although WDS seems simplistic, it guarantees mass conservation and works well for an idealized estuarine intertidal basin with a uniform bed slope of about 1:4200. It is realistic that the onshore front of water body immediately runs up the slope during flood to inundate the dried cells in response to tide. This phase speed is relatively faster than that for ebb and accordingly it reproduces the tidal asymmetry. The model is next applied to South San Francisco Bay, California, which is often described as "a tidally oscillating lagoon with density-driven exchanges with the northern reach". The simulation does not include density effect, thus corresponds to summer condition when freshwater input is minimal. Sinusoidal semi-diurnal tide with amplitude of 1.2 m induces wetting and drying processes (WDP) effectively. The number of simultaneously dried-up grid cells varies with time, reaching up to 271 cells. The depth-integrated and 3D surface residual current velocities show that there exists intense horizontal mixing between shallower and deeper regions. Further examination such as detailed hydrodynamics according to WDP, results from a harmonic analysis and particle trackings, etc., will also be presented at the conference.
DE: 4235 Estuarine processes
DE: 4255 Numerical modeling
DE: 4546 Nearshore processes
DE: 4560 Surface waves and tides (1255)
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting