ON EDDY CHARACTERISTICS, EDDY TRANSPORTS, AND MEAN FLOW PROPERTIES

Estimates of eddy energy and eddy scales obtained previously from TOPE X/POSEIDON (T/P) altimeter data are interpreted in the context of a ba roclinically unstable flow held. From the observations an integral tim escale T-alt can be defined that-combined with estimates of the eddy k inetic energy-sets a mixing length scale. Results are compared with th eories of a baroclinically unstable flow field. For such conditions, t he Eady theory predicts a timescale T-bc = root Ri/f from the mean-flo w Richardson number Ri, which shows some qualitative agreement with T/ P results in terms of a geographical distribution. A factor of 2 diffe rence between the timescales can be explained in terms of a systematic difference between the specific definition of scale estimates. Althou gh transfer length and velocity scales emerging out of scaling argumen ts lack resemblance with observations, a transfer length scale based o n T-bc and the observed eddy kinetic energy is strikingly consistent w ith observed eddy scales. Primarily independent of the energetic stale of the ocean, they are to first order largest in low latitudes and de crease toward high latitudes. Invoking a ''mixing length'' hypothesis, an eddy transfer kappa for a scaler tracer in the ocean can be estima ted from eddy statistics as a function of geographical position. Two d ifferent estimates of K can be obtained from altimetric data: (i) kapp a = alpha root KELbc and (ii) kappa = alpha'(g/f)sigma(SSH), where alp ha and alpha' are scaling factors, and sigma(zeta) is the films sea-su rface height variability estimated from T/P data. The approaches lead to similar estimates of a meridional eddy-induced heat and salt flux i nferred from climatological meridional temperature and salinity gradie nt F-T = -c(p) kappa (T) over bar/delta/delta y and F-S = -kappa delta (S) over bar/delta y. Results are consistent with previous knowledge but, because estimates are based on mean meridional gradients, they ha ve to be considered a lower bound on instantaneous eddy transports in the ocean.