Given improved wind speed measurements at several elevations for longer averaging times, longer wave records analyzed so as to fit the procedures more readily, and better wave data, the form of the spectra of fully developed wind seas and seas limited by either fetch or duration can be determined to even greater precision than that obtained here.

A composite divided scale model for radar backscatter from the ocean surface is constructed. The primary scattering mechanism is assumed to be Bragg scattering for which the normalized radar backscattering cross section is proportional to the spectral density of the resonant Bragg water waves. The form of the high-wave number equilibrium spectrum is derived on the assumption that the shortwave energy density reflects a balance between direct wind forcing and dissipation due to breaking and to viscosity. This theoretical equilibrium spectrum links the wave spectrum to the wind. This spectrum is then used in a two-scale Bragg-scattering model to link backscattering cross section to the full wave spectrum, which is this high-wave number spectrum plus a gravity wave spectrum for fully developed seas. The effects of tilt and modulation of the Bragg resonant waves by the longer waves are included along with the contribution from specular reflection at low incidence angles. The model is tested against aircraft circle flight K u band radar backscatter measurements with encouraging results for vertical polarization. It is demonstrated that particularly at low wind speeds, scatterometry is sensitive to surface water temperature through its effect on the viscous dissipation of short waves. Also for low wind speeds and low incidence angles (20 ø or so) an additional source of specular backscatter needs to be considered: that due to gravity waves that may be left over from previously higher winds or that enter the area as swell. For high incidence angles and high winds, the two-scale Bragg model yields values that are somewhat low compared with the data for vertical polarization. For horizontal polarization the model is somewhat low for a 40 ø incidence angle and much too low for higher incidence angles by amounts that cannot be explained by a combination of possible wind speed measurement errors and bias errors in the measurement of the backscatter. An explanation for these results is offered in terms of recent studies of backscatter from wedges and spilling breakers for Ku band. The model is then exercised over a much wider wind speed range from L band to K a band. For high wind speeds at anemometer height, except at L band, according to the model, the backscattering cross section becomes less sensitive to wind speed and at very high speeds decreases as the wind speed increases. The wind speed at which this "rollover" occurs is dependent on radar wavelength and incidence angle, being as low as 30 m s-• for K• band for vertical polarization at some incidence angles. The effect of wedges and breakers may overcome the predicted "rollover," especially for horizontal polarization, but there are data to support a tendency toward saturation for vertical polarization at perhaps a somewhat higher wind speed. The two-scale model does not appear to be sensitive to variations in the slopes of the tilting waves that would be present for nonfully developed seas. The number and size of wedges and spilling breakers will be a function of fe...

On the SEASAT-A satellite, a microwave scatterometer was used to determine the vector wind over the world's oceans. The technique is based on the sensitivity of microwave radar backscatter to the centimeter length ocean waves created by the action of the surface wind. This paper describes the algorithm used to convert the scatterometer' s measurements of ocean normalized radar cross section, •, to the neutral stability vector wind at 19.5 m height and the comparison of these winds with high quality surface observations. The wind vector algorithm used an empirical • model function to describe the dependence of the ocean • on the 19.5-m neutral stability wind vector. Two model functions, developed from a limited base of aircraft and satellite o • measurements, were evaluated by using an independent set of in situ surface wind observations from the Joint Air Sea Interaction Experiment (JASIN). Although these model functions were found to have some weaknesses, the results of these comparisons produced better results than the SEASAT specifications of wind speed accuracy of +-2 m/s and wind direction accuracy of +-20 ø over the 0-16 m/s range of winds observed during JASIN. An improved model function was later developed by 'tuning' to these JASIN data so that the remaining biases between the observed surface winds and the scatterometer-derived winds were minimized. Results are presented for this model function compared against other surface wind observations from the Gulf of Alaska SEASAT Experiment and the SEASAT Storms (Hurricane) Experiment. INTRODUCTION On June 28, 1978, •he National Aeronautics and Space Administration (NASA) launched SEASAT, the first satellite dedicated to establishing the utility of microwave sensors for remote sensing of the earth's oceans [Born et al., 1981]. This concept had its beginning in the mid-1960's when a conference called 'On the Feasibility of Conducting Oceanographic Explorations from Aircraft, Manned Orbital and Lunar Laboratories' was held at Woods Hole Oceanographic Institute, Woods Hole, Mass., in August 1964 [Ewing, 1965]. At this conference, the rudiments of many of the remote sensing systems for measuring oceanographic parameters were described that eventually were orbited on Skylab, Geos-3, and SEASAT. A few years later, a second conference sponsored by the National Academy of Sciences at Woods Hole made a broader study of potential areas of activity for NASA, including the study of the oceans. The concepts of high precision radar altimetry and of using radar backscatter to measure the winds both received considerable attention [National Research Council, 1970]. A third conference at Williamstown, Mass. [Kaula, 1970] also investigated the general subject; and ocean and atmospheric scientists postulated that satellite technology could provide the mecha-nism for monitoring the world oceans on a scale appropriate to the requirements of their research communities. Thus came SEASAT with its compliment of four microwave sensors; namely, a radar altimeter, a multifrequency radiom...

The Navier‐Stokes equations for incompressible flow in their Lagrangian form are taken as a starting point. A perturbation technique is then used to obtain first‐ and second‐order sets of equations, and the general procedure for solving the equations to any order is given. The first‐order equations yield interesting two‐ and three‐dimensional motions that have some of the properties of ‘stirring’ ‘eddies’ and ‘turbulence’; it is suggested that various problems in turbulent motion might possibly be re‐examined by means of these equations.

Mesoscale and microscale features of the turbulent winds over the ocean are related to the synoptic xscale winds in terms of published spectral forms for the microscale, a mesoscale valley, and published values of u*, Var u′, Var v′, and z/L, as defined in the text and as obtained for moderate to gale force winds. The frequencies involved correspond to periods longer than 1 hour and extend to the microscale, which starts at a period near 2 min, or so, and continues to the Kolmogorov inertial range. Nondimensional spectra that span both the mesoscale and the microscale are derived as a function of u*,f/(=nz/ū), and z/L, where z is 10 m, L is the Monin‐Obukhov stability length, and ū is evaluated at 10 m. For the same ū, different values of z/L produce a range of values of u* which in turn result in variations of the eddy structure of the mesoscale and microscale spectra. Both conventional anemometer averages and remotely sensed winds contain a random component of the mesoscale wind in their values. These components are differences and not ‘errors’ when winds are compared, and quantitative values for these differences are given. Ways to improve the measurement of the synoptic scale wind by transient ships, data buoys, and scatterometers on future spacecraft are described. These ways are longer averaging times for ships and data buoys, depending on the synoptic conditions, and pooling spacecraft data to form superobservations. Design considerations for future remote sensing systems are given.