Wind speed

About: Wind speed is a research topic. Over the lifetime, 48350 publications have been published within this topic receiving 830486 citations.

Estimation of the remote-sensing reflectance from above-surface measurements.

Abstract: The remote-sensing reflectance Rrs is not directly measurable, and various methodologies have been employed in its estimation. I review the radiative transfer foundations of several commonly used methods for estimating Rrs, and errors associated with estimating Rrs by removal of surface-reflected sky radiance are evaluated using the Hydrolight radiative transfer numerical model. The dependence of the sea surface reflectance factor ρ, which is not an inherent optical property of the surface, on sky conditions, wind speed, solar zenith angle, and viewing geometry is examined. If ρ is not estimated accurately, significant errors can occur in the estimated Rrs for near-zenith Sun positions and for high wind speeds, both of which can give considerable Sun glitter effects. The numerical simulations suggest that a viewing direction of 40 deg from the nadir and 135 deg from the Sun is a reasonable compromise among conflicting requirements. For this viewing direction, a value of ρ ≈ 0.028 is acceptable only for wind speeds less than 5 m s-1. For higher wind speeds, curves are presented for the determination of ρ as a function of solar zenith angle and wind speed. If the sky is overcast, a value of ρ ≈ 0.028 is used at all wind speeds.

Directional spectra of wind-generated waves

Abstract: From observations of wind and of water surface elevation at 14 wave staffs in an array in Lake Ontario and in a large laboratory tank, the directional spectrum of wind-generated waves on deep water is determined by using a modification of Barber's (1963) method. Systematic investigations reveal the following: (a) the frequency spectrum in the rear face is inversely proportional to the fourth power of the frequency $\omega $, with the equilibrium range parameter and the peak enhancement factor clearly dependent on the ratio of wind speed to peak wave speed; (b) the angular spreading $\theta $ of the wave energy is of the form sech$^{2}$ ($\beta \theta $), where $\beta $ is a function of frequency relative to the peak; (c) depending on the gradient of the fetch, the direction of the waves at the spectral peak may differ from the mean wind direction by up to 50 degrees, but this observed difference is predictable by a similarity analysis; (d) under conditions of strong wind forcing, significant effects on the phase velocity caused by amplitude dispersion and the presence of bound harmonics are clearly observed and are in accordance with the Stokes theory, whereas (e) the waves under natural wind conditions show amplitude dispersion, but bound harmonics are too weak to be detected among the background of free waves.

An Economic Dispatch Model Incorporating Wind Power

Abstract: In solving the electrical power systems economic dispatch (ED) problem, the goal is to find the optimal allocation of output power among the various generators available to serve the system load. With the continuing search for alternatives to conventional energy sources, it is necessary to include wind energy conversion system (WECS) generators in the ED problem. This paper develops a model to include the WECS in the ED problem, and in addition to the classic economic dispatch factors, factors to account for both overestimation and underestimation of available wind power are included. With the stochastic wind speed characterization based on the Weibull probability density function, the optimization problem is numerically solved for a scenario involving two conventional and two wind-powered generators. Optimal solutions are presented for various values of the input parameters, and these solutions demonstrate that the allocation of system generation capacity may be influenced by multipliers related to the risk of overestimation and to the cost of underestimation of available wind power.

Boundary Layer Wind Maxima and Their Significance for the Growth of Nocturnal Inversions

Abstract: A sharp maximum is frequently observed at night in the wind speed profile below 3000 ft. The wind speed maximum is usually at the top of the nocturnal inversion, is supergeostrophic, and is often associated with extremely large values of wind shear at low levels. It is shown that the characteristic velocity profile tends to promote an orderly growth of the nocturnal inversion. The supergeostrophic wind speeds suggest that an inertia oscillation is induced when the constraint imposed by the daytime mixing is released by the initiation of an inversion at about the time of sunset.

Review of Drag Coefficients over Oceans and Continents

Abstract: Observations of wind stress and wind profiles over the ocean reported in the literature over the past 10 years are consistent with Charnock's (1955) relation between aerodynamic roughness length (z0) and friction velocity (u*), viz, z0= αu*2/g, with α= 0.0144 and g= 9.81 m s−2. They also imply a von Karman constant = 0.41±0.025. For practical purposes Charnock's relation may he closely approximated in the range 4&