Aircraft measurements of turbulent fluxes of momentum, sensible heat, and moisture were used to calculate bulk aerodynamic coefficients over the northern California coastal shelf during wintertime (Shelf MIxed Layer Experiment, SMILE) and summertime (Coastal Ocean Dynamics Experiment, CODE). Low-level (30 m) data from 15 SMILE flights and 15 CODE flights with varying stability conditions, wind directions, and intensities were reduced to the standard reference height of 10 m using diabatic flux-profile relations following Monin-Obukhov similarity theory. The fluxes were parameterized by bulk aerodynamic formulas after reduction to neutral stability. Results for summer and winter were in reasonably good agreement if the bulk coefficients are averaged over intervals of 1 m s-1 and linear regression with speed is performed using the averaged values. The neutral drag coefficient showed a statistically significant linear dependence on wind speed at 10-m height, while the neutral Stanton and Dalton numbers (the heat and moisture transfer coefficients) were independent of wind speed and were not significantly different from each other. The response of the ocean to the atmospheric forcing and the feedback of the resulting ocean circulation on the wind forcing were studied using a vertically resolved numerical model of coastal upwelling. The model was run using buoy observations of wind speed, air temperature, atmospheric pressure, and relative humidity from SMILE and CODE. The resulting coastal upwelling produced a negative feedback through decreased sea surface temperature at the coast and increased atmospheric stability which decreased the effective drag coefficient (and hence the wind stress) by at most 30% near the coast, with an average decrease of about 12% within 100 km from the coast. The effect of this decrease in wind stress, however, produced an insignificant change in the sea surface temperature field, which indicates that parameterization of coastal drag coefficients for modeling coastal upwelling can be done without taking into account surface temperature feedback.¿ 1997 American Geophysical Union