Wave-induced velocities and turbulent reynolds stresses above an air-water interface

The progressive, sinusoidal (1.0 Hz) water-wave-induced perturbations in a turbulent air flow above an air-water interface were studied in a large laboratory facility. The velocity field was measured in both fixed and wave-following reference frames with a cross hot-film probe. Both the magnitude and phase of the wave-induced velocities and turbulent Reynolds stresses were obtained across the turbulent boundary layer for different free stream velocities.     

A random process for earthquake simulation

Some existing models for the simulation of earthquake acceleration show the difficulties in determining the involved parameters and in describing frequency content. A non-stationary modulated random process obtained as the product of a time envelope function and a stationary random function is used to simulate earthquake acceleration. The parameters and the distribution of frequencies of the simulation process are obtainable from past earthquake records. This simple and realistic model is suggested for use as the input process in aseismic design of structures.     

Torsional spectrum for earthquake motions

A computational scheme is presented to construct torsional spectra due to the rotational component of seismic ground motions. The rotational component of ground motion is estimated from the measured earthquake acceleration records. In contrast to previous studies, no differentiation of acceleration records is involved in the present scheme. The torsional spectrum of the 1940 El Centro earthquake is computed and compared with previous results. An average and a mean plus one standard deviation torsional spectrum is presented for design purposes. These spectra are results based on four historical records (1934 El Centre, 1940 El Centro, 1949 Olympia and 1952 Taft) normalized to the 1940 El Centro intensity.     

An operational forecasting model for the variation of mean maximum mixing heights across the coastal zone

Variation exists in the maximum mixing height (MMH) across the coastal zone because of major differences in heat capacity between land and sea. By assuming that synoptic and microscale effects are all small as compared to the contribution from mesoscale temperature differences, a model is proposed to explain this variation. The model states that the variation of the MMH across the coastal zone is due primarily and is linearly proportional to the difference in maximum temperature between land and sea. Since the MMH is one of the most important parameters in the computation of distribution and concentration of aerosols, water vapor, and pollutants, a simple equation is also provided for the operational forecasting of the MMH or the mixing height over the sea. All inputs into the equation are routinely available. The model has been verified by available data and a relevant field experiment.     

Measurements of the height of the convective surface boundary layer over an arid coast on the Red Sea

The height of the convective boundary layer over an arid coast on the Red Sea was measured by high-resolution radiosondes. These measurements can be used to compute sensible heat flux by the method devised by Danard (1981). The average heat flux computed is in good agreement with results obtained independently by both the energy balance method and the free-convection equation.     

Positron annihilation lifetime spectral changes on dehydration of natural beryls and cordierites

The effect on positron annihilation lifetime spectra, measured at room temperature, of the dehydration of single crystals of beryl and cordierite was studied. In each case, the spectra were satisfactorily fitted to three lifetime components. For the beryls, the dehydration considerably enhanced the intensity of the intermediate-lifetime component (I ₂) and reduced the intensity of the longest-lived component (I ₃). I ₂ is attributed to positron annihilation in the empty cages in the channels of the beryl structure and I ₃ to annihilation by a pick-off process via unknown foreign molecules. However, for the cordierites, the main effect of the dehydration was a slight (～10%) increase in the lifetime of the intermediate component, τ₂. Here I ₂ was relatively high both before and after dehydration and the increase in τ₂ is attributed to Si-Al ordering. No changes in the lifetime spectra were produced by γ irradiation.     

Boundary-layer trade-wind profile and stress on a tropical windward coast

Under persistent onshore trade-wind conditions, the wind profile was measured in the surface layer on a mud flat of the tidal stream of Estero de Data, Gulf of Guayaquil, Ecuador. It was found that the logarithmic wind relation fitted the observations very well and that the inferred shear velocity was a linear function of wind speed in the range of wind velocity studied.     

Recent Advances in Air–Sea Interaction Studies Applied to Overwater Air Quality Modeling: A Review

— Air quality modeling in the marine environment requires a better understanding of air–sea interaction. The behavior of the sea is different from that of the land, particularly with respect to the aerodynamic roughness parameter which changes temporally and spatially as a function of wind-generated wave characteristics. Recent improved understanding in air–sea interaction as applied to topics in air quality modeling are discussed. They include stability characteristics, variation of the wind speed with height, mixing height, standard deviation of crosswind and vertical wind, and the eddy diffusion. These topics are synthesized for scientists and engineers who need to improve the air quality modeling for overwater applications.