STATISTICAL-ANALYSIS OF THE SURFACE CIRCULATION OF THE CALIFORNIA CURRENT

We use a set of mixed-layer drifting buoy trajectories from the Califo rnia Current (20 degrees N-40 degrees N) during 1985-1990 to obtain st atistically reliable estimates of the mean currents, the mean variance field, and the geographically varying. diffusivity, integral timescal es, and integral space scales. Typical values for the diffusivity are 1.1-8.7 x 10(7) cm(2) s(-1), while the timescales and space scales are 2.1-7.1 days and 16-59 km, respectively. The variance field displays a strong westward gradient out to 125 degrees W, and diffusivity shows a tendency to decrease toward the southwest part of the domain. Signi ficant anisotropy is found in the variance field near the coastal boun dary and at 30 degrees N, 130 degrees W, which is the region where the subarctic and northern subtropical fronts approach the California Cur rent. The antisymmetric component of the diffusivity tensor indicates that cyclonic eddies dominate the mesoscale signature of drifters in t his region. We seek simple parameterizations to relate the scales of m otion of the random velocity field to the diffusivity by testing least squares fits to kappa(infinity) proportional to u(0)(2)T and kappa(in finity) proportional to u(0)L, where u(0)(2) is the velocity variance. We found no cases for which these two hypotheses could be distinguish ed. For the meridional component the linear regressions are not succes sful, which suggests that the meridional departure velocities result f rom a flow regime that is significantly organized by, for example, wav es or coherent structures. A subset of the drifters measured temperatu re along their tracks, and we use the resultant data to produce the fi rst direct estimates of the horizontal eddy heat nux divergence based on Lagrangian estimates. In addition, we separately compute the ''eddy diffusivity'' parameterization of the eddy heat flux divergence, del . [u'theta'] = del(kappa del Theta), using our diffusivity estimates a nd a sea surface temperature climatology. The two independent terms ag ree well, which provides a measure of reassurance about the diffusivit y estimates. The eddy heat flux divergence in the California Current i s very small (<5 W m(-2)) and does not appear to be significant in the long-term heat budget of the upper ocean in this region.