Lagrangian Coastal Processes With Application Of Remote Sensing Technology

Use of satellite remote sensing technology was conceived to augment the interpretability of the "Eulerian" information arising from the existing network of fixed oceanographic stations at San Onofre Nuclear Generating Station, California. Thermal IR imagery from Tiros-N, NOAA-6 and NOAA-7 was used to view the water mass dynamics, whereas the Coastal Zone Color Scanner (CZCS) imagery from Nimbus-7 was used to define spatial distribution of chlorophyll. The combined "Lagrangian" (satellite imagery) and "Eulerian" (current meter and temperature probe data) approach proved highly fruitful in the monitoring program for the San Onofre Nuclear Generating Station. The coastal fronts, ubiquitous yet not readily visible, were recognized on the thermal IR imagery, with elongated distribution within the cool water on the shore side from the warm water on the offshore side. Frontal zones are regions of high biological productivity; they also affect the dispersion of floatables and buoyant effluent. The CZCS imagery revealed the chlorophyll fronts generally coinciding in location with the coastal fronts, with higher chlorophyll concentrations occurring on the side of cool water. The on- and off-shore displacements of the coastal front were triggered by the coastal upwelling processes in a manner which could only be recognized on satellite imagery. The coastal upwelling occurred at isolated pockets in the lee of coastal headland, and its characteristic location suggested that it was associated with a raised thermocline at the center of a cyclonic gyre driven by the predominant northerly wind. The cool water from the upwelling pockets advected downwind displacing the coastal front seaward. On the other hand, during the lull of the upwelling activity, the front converged shoreward and even virtually attached itself to the shoreline. Comparison with the measurements at the ground stations indicated that the passage of the front might cause a quantum jump in seawater temperature amou- ting to as much as 6\´C, as frequently observed during the height of the upwelling season off San Onofre.