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RAFOS float observations collected between 1992 and 2002 were analyzed to identify the seasonal variability of circulation in four geographical boxes which extended along the central and northern California coast and were successively located farther offshore. The mean pressure of the floats was 375 dbar. Poleward flow associated with the California Undercurrent dominated the two boxes closest to shore, extending from the 400‐m isobath to a distance of 190 km offshore. For the box closest to shore, the monthly mean alongshore velocity was maximum (minimum), 5.4 cm/s (1.7 cm/s), in May–June (February), while the eddy kinetic energy (EKE) was minimum was 33 cm2/s2 (21 cm2/s2) in September (December–February). The mean EKE in the coastal region was 28 cm2/s2, increasing to 50 cm2/s2 for the region farthest offshore, a distance of about 400 km. For that region farthest offshore, EKE had a broad maximum from June to November and a minimum in April. Lagrangian correlation and dispersion tensors were estimated for floats that left the coastal region. Three different dispersive regimes of float motion were identified as ballistic transport, normal diffusion, and anomalous sub‐diffusion. Westward sub‐diffusion was induced by Rossby wave‐like structures with a periodicity of 100–120 days.

A discrete wavelet transform was applied to satellite altimetry data for the period 1992–2007 off California to decompose the SSH signal into inter‐annual, annual, semi‐annual and shorter period components. For the lowest frequency (inter‐annual) component, a system of alternating quasi‐zonal jets was detected. The jet system was delineated by a north‐south series of quasi‐zonal bands of co‐rotating eddies; that is, the eddies were embedded in a shearing zonal flow. The direction of eddy rotation alternated between adjacent bands. The temporal behavior of the jet system showed the existence of quasi‐stationary states and transitions between them. Observed non‐linear effects of the evolution of the jets included southward drift at about 0.2 cm sec−1, deviations of the jets from the zonal direction, and re‐forming of the jet system through decay and merging of eddy chains.

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Along-shore wind fluctuations and an equatorially forced coastal Kelvin wave were found to be responsible for the excitation of annual-and semiannual-propagating Rossby waves in the eastern subbasin. These waves are transmitted along a waveguide formed by the African shelf and the MAR. The speed of their propagation varies in magnitude and direction because of bottom topography and irregularity of the coastline. Unstable standing Rossby waves with annual and semiannual periods are shown in both the subbasins. All unstable waves, decaying, radiate shorter free Rossby waves propagating both westward and northwestward, with speeds of up to 10 cm/s. The standing Rossby waves are probably excited by the wind-driven Ekman pumping alone or in combination with linear and nonlinear resonance mechanisms. The additional analysis of subsurface float tracks from

We describe a nontraditional method for processing data derived from quasi-Lagrangian tracers. The approach relies on a representation of the thermohydrodynamic field as a set of a finite number of functions (modes) with the subsequent computation of mode amplitudes from quasi-Lagrangian data. This requires special methods for calculating mode components of the thermohydrodynamic field from Lagrangian observations. Also, because of the quasi-Lagrangian nature of the data there are special problems caused by the need to filter in both space and time and to account for motions unresolved by such observations. The former problem is addressed by a filtering procedure based on a variational criteria and Pontryagin's principle. To handle the latter problem, a subgrid parameterization scheme appropriate for Lagrangian data is proposed. 1.Lagrangian" will be used to designate this setting. Of course, real probes in the surface layer also will respond differently than do generic parcels to accelerations arising from winds and waves. These effects can be quantified and minimized through engineering studies. The emphasis here is on procedures for recovering mesoscale and general circulation features from quasi-Lagrangian data, and so the latter effects will not be addressed.The present approach falls into the third category in that it utilizes the deterministic character of Lagrangian data and is complementary to numerical modeling. It differs, however, from the approach taken by Kitwan et al. [ 1988, 1990] in that no a priori transformation between Eulerian and Lagrangian frames is required. It can also be applied to basin-scale data sets, whereas the Kirwan, et al. methodology is "local." The analysis utilizes mathematical tools that are standard for Eulerian data and models. In doing so, it addresses the important issue of how to filter the trajectory data in a manner consistent with Eulerian data analysis. This is a fundamental problem in oceanography, as Eulerian data lend themselves naturally to discerning time scales while Lagrangian data encapsulate both time and space information.In view of these issues, a detailed airing of the mathematical basis of this approach is appropriate. This is provided in the next three sections. Section 2 gives some background and rationale, section 3 provides the general formulation, and section 4 shows how to obtain the mode structure of the velocity field. In section 5 the mathematical formalisms developed in the previous sections are applied to the problem of obtaining the mode representation of temperature data.Up to this point the mathematical approach is an adaptation of methods from classical theoretical physics. The next two sections (6 and 7) address problems peculiar to quasi-Lagrangian data. Methods based on a variational principle for filtering the observations in both space and time are discussed in section 6. Quasi-Lagrangian data are discrete and subject to aliasing by motions whose scales are less than the sampling rate. Section 7 addresses the issue of parame-9733 V. ...

The capability of the reconstruction scheme developed in Part I is demonstrated here through three practical applications. First, the nonlinear regression model is used to reproduce the upper-layer three-dimensional circulation of the eastern Black Sea from model data distorted by white and red noises. Second, the quasigeostrophic approximation is used to reconstruct the shallow water circulation pattern in an open domain with various sampling strategies. Third, the large-scale circulation in the Southern Ocean is reproduced from the First Global Atmospheric Research Program (GARP) Global Experiment (FGGE) drifter data with noncontrollable noise statistics. All three cases confirm that the theoretical approach is robust to various noise-to-signal ratios, number of observations, and station disposition. Using the simplified open boundary condition for analyzing long-term observational data is recommended because the nonlinear regression procedure requires considerable computer resources.