Scatterometer and Model Wind and Wind Stress in the Oregon-Northern California Coastal Zone

摘要

Measurements of surface wind stress by the SeaWinds scatterometer on NASA's Quick Scatterometer (QuikSCAT) satellite are analyzed and compared with several different atmospheric model products, from an operational model and two high-resolution nested regional models, during two summer periods, June through September 2000 and 2001, in the coastal region west of Oregon and northern California. The mean summer wind stress had a southward component over the entire region in both years. Orographic intensifications of both the mean and fluctuating wind stress occurred near Cape Blanco, Cape Mendocino, and Point Arena. Substantial differences between the model products are found for the mean, variable, and diurnal wind stress fields. Temporal correlations with the QuikSCAT observations are highest for the operational model, and are not improved by either nested model. The highest-resolution nested model most accurately reproduced the mean observed stress fields, but slightly degrades the temporal correlations due to incoherent high-frequency (0.5-2 cpd) fluctuations. The QuikSCAT data reveal surprisingly strong diurnal fluctuations that extend offshore 150 km or more with magnitudes that are a significant fraction of the mean wind stress. Wind stress curl fields from QuikSCAT and the models show local cyclonic and anticyclonic maxima associated with the orographic wind intensification around the capes. The present results are consistent with the hypothesis of a wind-driven mechanism for coastal jet separation and cold water plume and anticyclonic eddy formation in the California Current System south of Cape Blanco.