Effects of Wind Stress and Wind Stress Curl Variability on Coastal Upwelling

Abstract

Abstract Aircraft measurements during the winter 1989 Shelf Mixed Layer Experiment (SMILE) and summer 1982 Coastal Ocean Dynamics Experiment (CODE) were used to characterize the spatial variation of the low-level wind and wind stress over the northern California shelf. The curl of the wind stress was calculated from directly measured turbulent stress components. The accuracy of the computed curl was estimated to be adequate to map the spatial structure. Wintertime measurements showed a concentration of large positive curl [over 1 Pa (100 km)−1] west of Point Arena, regardless of wind direction, due to the effects of the coastal topography on the wind fields. Results from summertime measurements showed a similar local maximum of positive curl west of Point Arena. Larger curl values [over 3.5 Pa (100 km)−1], however, were observed across a hydraulic jump propagating from Stewarts Point for highly supercritical marine boundary-layer flow. A two-layer, vertically integrated numerical model of coastal upwellin...