The Stokes drift velocity for random surface gravity waves is given in. terms of the directional energy spectrum. The drift velocity is evaluated for empirical forms of the spectrum for fully developed seas. The result is that the surface drift velocity increases linearly with increasing wind speed and the ratio of surface drift speed to wind speed at 19.5 meters is between 1.6 and 3.6%. The stokes drift velocity may therefore contribute significantly to the total mean surface currents in the ocean. Introduction.The modified form of the Stokes drift velocity [Stokes, 1847] for a random sea is briefly considered. For a statistically stationary and horizontally homogeneous wave field, the total wave drift is the sum of the drifts of the individual wave components. The expression for the Stokes drift, given here in terms of the full two-dimensionM energy spectrum for arbitrary constant mean depth, is more general than expressions given by Chang [1969] and Bye [1967]. Stokes, G. G., On the theory of oscillatory waves, Trans. Cambridge Phil. Soc., 8, 441-455, 1847. Tomczak, G., Investigations with drift cards to determine the influence of the wind on surface currents, in In Studies on Oceanography, edited by K.
The field of wind-generated ocean surface gravity waves is reviewed for the period covering the last fifteen years. Theories and observations relevant to understanding the physics of wind waves are discussed, as well as techniques for measuring and forecasting waves.It is found that although a great deal of recent progress has been made on certain aspects of the wind wave problem, there are still important aspects which are poorly understood. I n particular, the central problem of how the wind generates waves in the ocean has not yet been solved; the primary physical mechanism(s) by which the wind makes waves has not been found. When the wind blows how much energy and momentum goes into waves and how much goes into currents? At the present time it is not possible to give a very definite answer to this important question. However, wave generation theories are available which perhaps can be modified to give better agreement with observations than they do now. New wave measuring techniques developed recently and/or under development now may provide the badly needed field observations necessary for future advances in understanding wind waves.Very little is known about the dissipation of wind waves, either in the open ocean or near coastal boundaries. Relevant theories and observations are not sufficient for understanding wave dissipation at present. Relatively little work has been done in the general area of the interaction of wind waves with currents. Some preliminary theoretical work suggests that this interaction could be quite important in the particular problem of the propagation of wind waves into major ocean currents, but an experimental test of the theory is lacking.Present methods of wave forecasting incorporate more physics than the earlier empirical methods. However, these methods still require a set of 'engineering approximations' in order to produce decent forecasts. With proper tuning the numerical forecast models produce good estimates of the one-dimensional wave spectrum.
The densities of 124 samples of seawater from stations at 35°N in the Pacific Ocean have been measured with a vibrating flow densimeter at 25°C. The measured densities were compared with those calculated from the equation of state of Millero et al. (1976b), derived for seawaters of constant relative composition. Values for the excess density Δd(excess) = d(meas) ‐ d(calc) were found to be ±3.8 ± 3.0 × 10−6 g cm−3 from 0 to 490m, 12.5 ±4.2 × 10−6g cm−3 from 490 to 1000 m,; and 17.6 ± 2.6 × 10−6g cm−3 from 1000 to 5834 m. The excess densities for the deep waters are in good agreement with our earlier measurements: 16.1 ± 3.6 × 10−6g cm−3 (Millero et al., 1976c). The values of Δd(excess) predicted by correcting for the increase of alkalinity (ΔAT), total carbon dioxide (ΣCO2), and dissolved silica (ΔSiO2) and nitrate (ΔNO3) in the deep waters (Brewer and Bradshaw, 1975; Millero et al., 1976c) agree with the measured values on the average to ±5.2 × 10−6 g cm−3. In the deep waters the measured values of Δd(excess) are ∼6 × 10−6 g cm−3 higher than the predicted values. The values of Δd(excess) were also calculated by assuming that the changes in salinity due to the added solids affect the density by the same amount as changes in weight‐diluted standard seawater: 106Δd = 757ΔS(‰). The values of Δd(excess) calculated from 106Δd(excess) = 37.9ΔAT + 72.8ΔSiO2 + 47.7ΔNO3 agree with the measured values on the average to ±4.3 × 10−6 g cm−3, independent of the depth. These results indicate that the density changes due to small changes in the composition of deep ocean waters can be accounted for by changes in the salinity due to the mass of added dissolved solids (ΔS(‰) = ΣMi Δni, where Mi is the equivalent or molecular weight and Δni is the change in the equivalents or moles of solute i in 1 kg of seawater).
The volume transport associated with the Stokes drift for a fully developed surface-gravitywave field is calculated from an empirical ocean energy spectrum to increase as the cube of the wind speed and to have the magnitudes 0.3-2.5 m•/sec for the wind speeds 10-20 m/sec. The vertical velocity beneath the wave boundary layer induced by the horizontal div•ergence of the Stokes drift over a fetch of 1000 km is estimated to be 0.3-2.5 X 10-' cm/sec for the same wind speed range.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.