Waves and shallow water

About: Waves and shallow water is a research topic. Over the lifetime, 5833 publications have been published within this topic receiving 108413 citations.

Large-Scale Dynamical Fields Associated with Convectively Coupled Equatorial Waves

Abstract: Convectively coupled equatorial waves, as previously detected in studies of wavenumber-frequency spectra of tropical clouds, are studied in more detail. Composite dynamical structures of the waves are obtained using linear regression between selectively filtered satellite-observed outgoing longwave radiation (OLR) data, and various fields from a global reanalysis dataset. The selective filtering of the OLR was designed to isolate the convective variations contributing to spectral peaks that lie along the equatorial wave dispersion curves for equivalent depths in the range of 12–50 m. The waves studied are the Kelvin, n = 1 equatorial Rossby (ER), mixed Rossby–gravity, n = 0 eastward inertio–gravity, n = 1 westward inertio–gravity (WIG), and n = 2 WIG waves. The horizontal structures of the dynamical fields associated with the waves are all generally consistent with those calculated from inviscid equatorial β-plane shallow water theory. In the vertical, there are statistically significant structur...

Motion of Waves in Shallow Water, Interaction between Waves and Sand Bottoms (1946)

Abstract: The loss of energy of a travelling water wave, due to the mechanism of the formation of sand ripples and water vortices on a sandy bed, becomes of practical importance when models are used to predict full-scale foreshore movements. On the assumption that the bottom-water oscillation is nearly simply harmonic, the mechanism was studied by oscillating a section of bed through still water. The pitch, p, of the sand ripple formed was found to vary as the square root of the grain diameter, independently of the speed and of the grain density, for amplitudes, R, of water motion exceeding this pitch. But for smaller amplitudes the pitch shortens with decreasing amplitude of movement. The mean drag coefficient, k, in the case of artificial rigid ripples, was measured directly. For R/p less than unity, k remains constant. For R/p greater than unity, k was found to vary as (R/p)-0.75. These results are compared with the case of steady flow. The critical water speeds and amplitudes for first disturbance of grains on a smoothed surface was also measured, over a wide range of grain diameters and densities. The results conform closely to a simple empirical expression.

Variation with depth in shallow and deep water marine sediments of porosity, density and the velocities of compressional and shear waves

Abstract: In a study of the dependence of the velocity of compressional waves in marine sediments upon the thickness of overburden, the velocity‐depth relationship in shelf sediments is shown to be distinctly different from that in deep basin sediments. The difference between the two cases may be illustrated by comparing the straight lines that best represent the data. These are V=1.70Z+1.70, shallow water, V=0.43Z+1.83, deep water where V is in km/sec and Z is in kilometers. Shallow and deep water are defined arbitrarily to be under 100 fathoms and over 1,500 fathoms respectively. The observed variation of average compressional velocity in the shallow and deep water sediments, taken together with the known limited range of variation of velocity for a given porosity, yields limits in turn upon the porosity‐depth dependence in the two environments. It is shown that at the same depth of overburden porosity is much greater in deep water sediments than in shallow. A physical argument is presented to show that there is ...

Diffuse reflectance of oceanic shallow waters: influence of water depth and bottom albedo

Abstract: We used simplifying assumptions to derive analytical formulae expressing the reflectance of shallow waters as a function of observation depth and of bottom depth and albedo. These formulae also involve two apparent optical properties of the water body: a mean diffise attenuation coefficient and a hypothetical reflectance which would be observed if the bottom was infinitely deep. The validity of these approximate formulae was tested by comparing their outputs with accurate solutions of the radiative transfer obtained under the same boundary conditions by Monte Carlo simulations. These approximations were also checked by comparing the reflectance spectra for varying bottom depths and compositions determined in coastal lagoons with those predicted by the formulae. These predictions were based on separate determinations of the spectral albedos of typical materials covering the floor, such as coral sand and various green or brown algae. The simple analytical expressions are accurate enough for most practical applications and also allow quantitative discussion of the limitations of remote-sensing techniques for bottom recognition and bathymetry. As early as 1944, Duntley used a spectrograph mounted in a glass-bottomed boat or flown in an airplane to analyze radiances emerging from the ocean and shallow waters. He evidenced the influence of the water depth on the spectral composition of the upward flux (Duntley 1963). Using a Monte Carlo technique, Plass and Kattawar (1972) calculated the radiative field in the atmosphere+cean system and in particular examined the dependence of the upward flux on the albedo of the ocean floor. Gordon and Brown (1974) studied the diffuse reflectance of a shallow ocean using Monte Carlo simulations and a probabilistic approach. Gordon and Brown provided an analysis based on photon history of the light field as modified by the presence of a reflecting bottom. In, addition, Ackleson and Klemas (1986) developed a two-flow model that simulated the light field within a canopy of bottom-adhering plants. A single scattering approximation for irradiance reflectance was also

Motion of Waves in Shallow Water. Interaction between Waves and Sand Bottoms

Abstract: The loss of energy of a travelling water wave, due to the mechanism of the formation of sand ripples and water vortices on a sandy bed, becomes of practical importance when models are used to predict full-scale foreshore movements. On the assumption that the bottom-water oscillation is nearly simply harmonic, the mechanism was studied by oscillating a section of bed through still water. The pitch, p, of the sand ripple formed was found to vary as the square root of the grain diameter, independently of the speed and of the grain density, for amplitudes, R, of water motion exceeding this pitch. But for smaller amplitudes the pitch shortens with decreasing amplitude of movement. The mean drag coefficient, k, in the case of artificial rigid ripples, was measured directly. For R/p less than unity, k remains constant. For R/p greater than unity, k was found to vary as (R/p)-0$^{\cdot}$75. These results are compared with the case of steady flow. The critical water speeds and amplitudes for first disturbance of grains on a smoothed surface was also measured, over a wide range of grain diameters and densities. The results conform closely to a simple empirical expression.