. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography tion patterns for wavelengths greater than 50 m over swath widths of up to 100 km on a selected basis; it does so with a near-all- weather capability \ Brown et <;/., 19761. Figure 4 shows a surface wave field as obtained from the synthetic aperture imaging radar and a digital Fourier transform, which ap- pears to yield a wave slope spectrum I Brown vt «/., 19761. Currents and Vertical Motions Ocean currents are driven by wind stress, by tidal fo
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography tion patterns for wavelengths greater than 50 m over swath widths of up to 100 km on a selected basis; it does so with a near-all- weather capability \ Brown et <;/., 19761. Figure 4 shows a surface wave field as obtained from the synthetic aperture imaging radar and a digital Fourier transform, which ap- pears to yield a wave slope spectrum I Brown vt «/., 19761. Currents and Vertical Motions Ocean currents are driven by wind stress, by tidal forces, and by uneven temperature and salinity distributions in the body of the sea. On the rotating earth a moving fluid tilts its surface relative to the geoid with a slope proportional to the fluid velocity; this is called geostrophic flow. In the case of western bound- ary currents, , the Gulf Stream, the slopes are of order 10 ~r' or less; the resultant topographic elevations across the stream, measured with respect to the geoid, are about 1 m or less. Upwellings and downwellings are slow vertical flows usually brought about by wind stress and coastal topography. Upwellings in particu- lar are of interest because the cold subsurface water often has a high nutrient level that may lead to a plankton bloom and ultimately an enhanced fish population. From the standpoint of spacecraft data the speed of the current in an upwelling is not observable, but rather the timely identification and location of the event are possible. In order to determine the com- plete dynamical current velocity field, one must measure speed and direction as a function of position and time. In addition, the vertical distribution of current velocity throughout the water column is needed for measuring total transports of water, dissolved chemicals, nutrients, etc. This is ob- viously impossible from satellites, and therefore to any surface current measurements made from spacecraft must be appended sub-
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