Adjustment of the marine atmospheric boundary layer to the large-scale bend in the California coast

Observations of the surface wind field off the U.S. West Coast were made from satellite by the Sea Surface Microwave/Imager (SSM/I) during June 1994 and June 1996. The coast bends inward 28° at 40° N latitude. Northerly wind speeds are high within a region that extends far south and offshore of this bend, bounded on the east by the California coast. On average, the high‐speed wind zone extends ∼250 km from shore and 800 km alongcoast. Long coast‐perpendicular aircraft transects show that moving onshore, the depth of the MABL decreases, the northerly wind speed increases, and the Froude number increases. A network of oceanographic buoys records the surface wind speed, direction, and pressure. From six buoy pressure measurements, the geostrophic wind vector was computed to represent the synoptic flow over the Oregon‐northern California coastal waters. The satellite surface wind fields were composited by the direction of the buoy geostrophic background wind. The predominant direction is 210°–180°. A high‐speed region extends south of the bend for directions in the 0°–180° range (moving counterclockwise), which corresponds to a downcoast component of the pressure gradient. For directions between 180° and 0°, flow splits at the bend and the region of highest winds is found to its north and offshore. A high‐speed region south of the bend was present in 65% of the satellite wind maps as well as in the June averages. The flow's response to coastal promontories such as Point Arena is nested within this broad zone of fast, thin, likely supercritical flow.