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Log wind profile

About: Log wind profile is a research topic. Over the lifetime, 1499 publications have been published within this topic receiving 45027 citations. The topic is also known as: logarithmic wind shear law.


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Journal ArticleDOI
TL;DR: In this paper, wind and air-minus-sea temperatures are calculated in a form suitable for determining stress by any bulk aerodynamics model in which the drag coefficient can be represented by six or less coefficients of a second-degree polynomial in wind speed and stability.
Abstract: Over 35 million surface observations covering the world ocean from 1870–1976 have been processed for the purpose of calculating monthly normals and standard errors of the eastward and northward components of the wind stress and work done by the winds in the lower 10 m of the atmosphere. The fields are intended to serve as boundary conditions for models of the ocean circulation. Wind and air-minus-sea temperatures are calculated in a form suitable for determining stress by any bulk aerodynamics model in which the drag coefficient can be represented by six or less coefficients of a second-degree polynomial in wind speed and stability. The particular case of the wind speed and stability dependent drag coefficient discussed by Bunker is selected for analysis. January and July charts of wind stress, curl of the wind stress, mass transport stream-function, divergence of the Ekman transport and the rate of mechanical energy transfer are illustrated and discussed.

1,872 citations

Journal ArticleDOI
TL;DR: In this paper, the vertical distribution of horizontal mean wind in the lowest 8 metres over a reservoir (1·6 km × 1 km) has been measured using sensitive anemometers freely exposed from a fixed mast in water 16 m deep, the fetch being more than 1 km.
Abstract: The vertical distribution of horizontal mean wind in the lowest 8 metres over a reservoir (1·6 km × 1 km) has been measured using sensitive anemometers freely exposed from a fixed mast in water 16 m deep, the fetch being more than 1 km. The resulting profiles are closely logarithmic, the small differences being systematic and possibly due to the thermal instability which existed when the measurements were made. The usual law for wind profiles in neutral stability is where u is the wind speed at height z, k is von Karman's constant, log z (0) the intercept on the log z axis, and u* the so-called friction velocity defined by τ0 = pu, τ0 being the surface drag and rH the density of the air. To characterize the profiles u*/k, their slope, was plotted in relation to z (0), their intercept; this allowed a direct comparison with other profiles, in particular those recently measured in a laboratory channel by Sibul. The agreement was better than expected and indicated that z (0) was comparatively independent of fetch and stability but was largely determined by u*. The relation between u* and z (0) agreed roughly with the simplest non-dimensional relation between them, gz (0)/u = constant, so that one is led to a generalized wind profile for flow over a water surface which specifies the drag, given the wind at one known height. An approximate value of the constant is 12·5. This expression can be compared with earlier work. The better wind-profile observations show rough agreement; the experimental scatter is necessarily large since a water surface is aerodynamically much smoother than most land surfaces, precision anemometry in difficult circumstances being required to provide sufficiently precise values. Oceanographic measurements of the tilt of water surfaces are in fair agreement at high wind speeds but at low wind speeds the data are conflicting. The early results which imply that the drag-coefficient (u/u2) increases with decreasing wind speed in light winds are thought to be in error; some support for this belief comes from recent estimates of drag using a modified ageostrophic technique, which agree roughly among themselves and with the general expression.

1,792 citations

Journal ArticleDOI
TL;DR: In this article, analytical expressions which specify non-dimensionalized wind speed and potential temperature gradients as functions of stability are integrated with Swinhank's wind and temperature profiles measured at Kerang, Australia.
Abstract: Analytical expressions which specify non-dimensionalized wind speed and potential temperature gradients as functions of stability are integrated. The integrated equations are tested against Swinhank's wind and temperature profiles measured at Kerang, Australia. It is found that a representation suggested independently by Businger and by Dyer gives the best fit to temperature profiles and describes the wind profiles equally as well as a relation suggested by Panofsky et al.

1,713 citations

Journal ArticleDOI
20 Mar 2003-Nature
TL;DR: It is found that surface momentum flux levels off as the wind speeds increase above hurricane force, contrary to surface flux parameterizations that are currently used in a variety of modelling applications, including hurricane risk assessment and prediction of storm motion, intensity, waves and storm surges.
Abstract: The transfer of momentum between the atmosphere and the ocean is described in terms of the variation of wind speed with height and a drag coefficient that increases with sea surface roughness and wind speed. But direct measurements have only been available for weak winds; momentum transfer under extreme wind conditions has therefore been extrapolated from these field measurements. Global Positioning System sondes have been used since 1997 to measure the profiles of the strong winds in the marine boundary layer associated with tropical cyclones. Here we present an analysis of these data, which show a logarithmic increase in mean wind speed with height in the lowest 200 m, maximum wind speed at 500 m and a gradual weakening up to a height of 3 km. By determining surface stress, roughness length and neutral stability drag coefficient, we find that surface momentum flux levels off as the wind speeds increase above hurricane force. This behaviour is contrary to surface flux parameterizations that are currently used in a variety of modelling applications, including hurricane risk assessment and prediction of storm motion, intensity, waves and storm surges.

1,314 citations

Journal ArticleDOI
TL;DR: In this article, surface layer coefficients for wind profiles, wind stress, and heat flux in typical open sea conditions are briefly reviewed, and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data.
Abstract: Surface layer coefficients for wind profiles, wind stress, and heat flux in typical open sea conditions are briefly reviewed. Businger-Dyer flux-gradient relationships and a Charnock wind stress formula fit the empirical data and are dimensionally consistent. These have been solved by an iterative method, and the results are presented in a tabular form suitable for climatological calculations from marine wind and temperature data.

1,101 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202312
202242
20211
20202
20191
20183