Diabatic Wind Research Articles

First-Order Scaling Law for Potential Vorticity Extraction due to Wind

AbstractSurface sources and sinks of potential vorticity (PV) have been examined recently in various publications. These are normally identified as the mechanical and buoyant PV fluxes with the former scaled according to wind stress and the latter from buoyancy flux. The authors here examine a PV source that is often overlooked: namely, the diabatically forced source due to wind-driven deepening.Based on an idealized model of the mixed layer, the rate of deepening of the mixed layer due to wind is translated into PV extraction. The authors propose the first-order scaling law as an estimate of the net PV flux due to diabatic wind effects in the absence of other buoyancy effects. This law is verified and calibrated in several numerical experiments. Then, the authors compare the magnitude of the PV extraction due to wind to the other factors responsible for PV input/output: namely, air–sea heat flux, freshwater flux, and Ekman wind-driven currents. Finally, to illustrate the impact of the mixing induced by wind, the authors conclude with a global air–sea PV budget in the North Atlantic basin. The wind-driven diabatic PV flux is found to be comparable to all other sources in all cases and is distinguished by acting only to extract PV.

Influence of atmospheric stability on wind turbine loads

ABSTRACTSimulations of wind turbine loads for the NREL 5 MW reference wind turbine under diabatic conditions are performed. The diabatic conditions are incorporated in the input wind field in the form of wind profile and turbulence. The simulations are carried out for mean wind speeds between 3 and 16 m s − 1 at the turbine hub height. The loads are quantified as the cumulative sum of the damage equivalent load for different wind speeds that are weighted according to the wind speed and stability distribution. Four sites with a different wind speed and stability distribution are used for comparison. The turbulence and wind profile from only one site is used in the load calculations, which are then weighted according to wind speed and stability distributions at different sites. It is observed that atmospheric stability influences the tower and rotor loads. The difference in the calculated tower loads using diabatic wind conditions and those obtained assuming neutral conditions only is up to 17%, whereas the difference for the rotor loads is up to 13%. The blade loads are hardly influenced by atmospheric stability, where the difference between the calculated loads using diabatic and neutral input wind conditions is up to 3% only. The wind profiles and turbulence under diabatic conditions have contrasting influences on the loads; for example, under stable conditions, loads induced by the wind profile are larger because of increased wind shear, whereas those induced by turbulence are lower because of less turbulent energy. The tower base loads are mainly influenced by diabatic turbulence, whereas the rotor loads are influenced by diabatic wind profiles. The blade loads are influenced by both, diabatic wind profile and turbulence, that leads to nullifying the contrasting influences on the loads. The importance of using a detailed boundary‐layer wind profile model is also demonstrated. The difference in the calculated blade and rotor loads is up to 6% and 8%, respectively, when only the surface‐layer wind profile model is used in comparison with those obtained using a boundary‐layer wind profile model. Finally, a comparison of the calculated loads obtained using site‐specific and International Electrotechnical Commission (IEC) wind conditions is carried out. It is observed that the IEC loads are up to 96% larger than those obtained using site‐specific wind conditions.Copyright © 2012 John Wiley & Sons, Ltd.

Comparing mixing-length models of the diabatic wind profile over homogeneous terrain

Models of the diabatic wind profile over homogeneous terrain for the entire atmospheric boundary layer are developed using mixing-length theory and are compared to wind speed observations up to 300 m at the National Test Station for Wind Turbines at Hovsore, Denmark. The measurements are performed within a wide range of atmospheric stability conditions, which allows a comparison of the models with the average wind profile computed in seven stability classes, showing a better agreement than compared to the traditional surface-layer wind profile. The wind profile is measured by combining cup anemometer and lidar observations, showing good agreement at the overlapping heights. The height of the boundary layer, a parameter required for the wind profile models, is estimated under neutral and stable conditions using surface-layer turbulence measurements, and under unstable conditions based on the aerosol backscatter profile from ceilometer observations.

Comparison of mesospheric and lower thermospheric residual wind with High Resolution Doppler Imager, medium frequency, and meteor radar winds

The objective of this study is to compare observed mean meridional winds with those deduced from theory. The diabatic circulation is computed from High Resolution Dopper Imager (HRDI) mesospheric and lower thermospheric temperatures during January and July conditions. The meridional wind component is compared with HRDI Eulerian mean meridional winds near 95 km and with seasonal averages of meridional winds at a number of radar medium‐frequency (MF) and meteor wind (MW) sites. The diabatic wind is directed from the summer toward the winter hemisphere. Peak values exceed 20 m s−1 and are observed at 105 km near 20° in the summer hemisphere. A secondary maximum of about 10 m s−1 is observed in the wintertime lower mesosphere during the July case. The diabatic wind is qualitatively consistent with HRDI 95‐km mean meridional winds at latitudes equatorward of 50°. Time‐averaged summertime radar winds are consistent with HRDI and diabatic winds between 50°S and 20°N. At winter midlatitudes, MF radar winds are directed oppositely to the diabatic wind, while one available MW measurement is directed with the diabatic wind. The zonal acceleration implied by the diabatic wind is about 150–200 m s−1 d−1 in the midlatitude summer lower thermosphere.

Analysis of wind speed observations over the North Sea

Abstract Wind speed observations of three offshore platforms over the period 1985–1992 have been analysed. These platforms located in the southern North Sea off the Dutch coast, are: K13 Platform (K13), Euro Platform (EPF) and Measuring Post Noordwijk (MPN). First, a statistical analysis of the data was performed, including calculation of mean wind speeds, availability of data, annual and diurnal variations, the Weibull parameters and the distribution by wind direction. Then, in order to compare the wind speeds of the platforms measured at different heights, Monin-Obukhov similarity theory was applied. Therefore, air and seawater temperature data were used from observations on the platforms (if available) or from Voluntary Observing Ships. The seawater temperatures were fitted to a sine function. Although, on a yearly average, (very) unstable conditions prevail, the calculated wind profiles showed hardly any difference between the logarithmic and the diabatic wind profile. On a seasonal basis, however, the logarithmic and diabatic wind profile differ significantly, for the spring season in particular. Wind speeds increased with increasing distance from the coast.

Sensitivity of calculated odd nitrogen distributions to the diabatic wind fields

Two‐dimensional and three‐dimensional model calculations are known to give stratospheric total odd nitrogen (NOy = N + NO + NO2 + 2 × N2O5 + HNO3 + HNO4 + ClONO2) mixing ratios which are significantly smaller than values inferred using measurements obtained from the limb infrared monitor of the stratosphere (LIMS) instrument. We examine NOy distributions calculated with two different advective transport fields, one derived from reported climatological data and one derived from LIMS T, O3, and H2O data. Specifically, it is of interest to see if the use of the advective fields derived from the LIMS data leads to a reconciliation of the inferred and calculated NOy distributions. Calculations with the advective field derived from climatological data show stronger poleward and downward motion in the winter season compared to the advective field derived from LIMS data. This leads to NOy mixing ratios in the lower stratosphere that are about 20% larger in the polar regions of both hemispheres and approximately 40% higher in the equatorial region for climatological transport fields compared to those derived from LIMS data. As a consequence, the NOy distributions calculated in the present model with the LIMS advective field show worse agreement with NOy values inferred from the LIMS measurements than similar results obtained with the climatological wind field. Ozone levels in the lower stratosphere calculated with the climatological wind field are smaller than those computed with the LIMS wind field, which is most likely an indirect chemical effect associated with the larger NOy values.

Diabatic wind speed profiles in coastal regions: Comparison of an internal boundary layer (IBL) model with observations

A model is presented to transform wind speed observations at a single height over sea or near the coast to any possible location and height in a topographic flat coastal region (up to distances of about 5 km from the coast and up to heights of 100 m). Only moderate and strong winds from the sea are considered, which are particularly important for wind energy applications. The model, called ‘diabatic coast model’, which is based on the well known internal boundary layer (IBL) concept and Monin-Obukhov similarity theory, describes the effects of the roughness transition from sea to land as well as the effect of stability on the shape of the profiles and the IBL growth. The predicted IBL heights are compared with published data.

Diabatic wind and temperature profiles obtained from a 100 m tower: A statistical comparison of model performances

More than 8000 10-min profiles of wind and temperature obtained during an extensive field experiment have been analyzed. The study was carried out in the environs of Valladolid (Spain) where a 100-m and a 6-m meteorological tower are located. Less than 20% of data were discarded due to equipment failure. Because of its exceptional flatness, the site is almost ideal for model performance comparisons. Predicted profiles of wind speed and potential temperature at 12, 26, 51, and 100 m heights were obtained using the methods proposed by Berkowicz and Prahm (1982) and San Jose (1983) based on values observed on a 6 m tower. Statistical t, F, and R tests were used to determine bias, scatter and correlation. The data were classified according to atmospheric stratification and height above ground. Finally, a determination was made of the predicted wind speeds and potential temperatures that fell within the 1 and 20% confidence ranges centered at the measured value. San Jose's method performed better than did that of Berkowicz and Prahm for the temperature profiles in both unstable and stable conditions. However, no significant differences were found for the wind speed profiles.

Estimates of diabatic wind speed profiles from near-surface weather observations

In this paper we analyse diabatic wind profiles observed at the 213 m meteorological tower at Cabauw, the Netherlands. It is shown that the wind speed profiles agree with the well-known similarity functions of the atmospheric surface layer, when we substitute an effective roughness length. For very unstable conditions, the agreement is good up to at least 200 m or z/L≃−7(z is height, L is Obukhov length scale). For stable conditions, the agreement is good up to z/L≃1. For stronger stability, a semi-empirical extension is given of the log-linear profile, which gives acceptable estimates up to ~ 100 m. A scheme is used for the derivation of the Obukhov length scale from single wind speed, total cloud cover and air temperature. With the latter scheme and the similarity functions, wind speed profiles can be estimated from near-surface weather data only. The results for wind speed depend on height and stability. Up to 80 m, the rms difference with observations Σ is on average ≃1.1 m s−1. At 200 m, Σ ≃ 0.8 m s−1 for very unstable conditions increasing to Σ ≃ 2.1 m s−1 for very stable conditions. The proposed methods simulate the diurnal variation of the 80 m wind speed very well. Also the simulated frequency distribution of the 80 m wind speed agrees well with the observed one. It is concluded that the proposed methods are applicable up to at least 100 m in generally level terrain.

Diabatic wind profile and its relation to the scale of turbulence

Wind profiles observed at various locations are used to examine the diabatic wind profile formulation of Yokoyama [31] on the basis of the similarity theory and scale of turbulence. It is shown that theory and observations agree well for various thermal stratification conditions. In conditions of very high stability, a linear profileom = 5.3z/L is suggested. In quasi-neutral conditions, a log-linear formulation (om ≃ 1 + 4z/L) is found to give an adequate description of the wind profile. In free convection conditions, a profile of the formom = 0.5 ( |z/L|)−1/3 is found to be appropriate. Nomograms relatingom, ψ andz/L are presented for stable and unstable conditions takingγ equal to 3, 9 and 15.

Average Bowen-ratio methods of calculating evapotranspiration applied to a Douglas fir forest

Daily evapotranspiration from a Douglas fir forest was calculated using Webb's average Bowen-ratio method. Webb's method is generalized to include the effects of the diabatic wind profile. Over a 17-day period characterized by light winds, the modified Webb method agreed with the daily totals of half-hour energy balance calculations to within 1 1/2 % on the average, while Webb's method overestimated by 26 % on the average.

An investigation of the diabatic wind profile of the atmospheric boundary layer

Over 2800 mean wind profiles (data from two mobile micrometeorological stations near Dallas, Texas) were analyzed to test the Monin-Obukhov similarity hypothesis as expressed by the log-linear wind profile. Wind speed and temperature data for eight levels between 25 cm and 32 m were averaged for 5- and 25-min periods. The Monin-Obukhov parameter α′, which is the coefficient of the linear term in the profile, was found to be a function of stability varying from 0.2 to 3.0 in lapse conditions and from 9 to 3 during inversion conditions. However, practical values of α′ for lapse (0.6) and inversions (5.0) conditions are suggested for forecasting mean diabatic wind profiles. The Obukhov ‘gradient length’ L' was found to be a function of height above the ground; therefore, it does not possess complete dynamic similarity. The broad applicability of the log-linear profile is shown by calculating residual variances for each profile as a function of height, wind speed, and stability. An empirical log-power profile was also tested. The preferred power for the diabatic term was unity (or larger) for inversion conditions and approximately 0.5 for lapse conditions. Since the standard error of estimate of the wind speed based on the log-linear profiles was not significantly greater than that based on log-power for the latter case, the log-linear profile appears to be adequate for all stability regimes.

Determination of stress from wind and temperature measurements

AbstractAn integrated form of the diabatic wind profile based on similarity theory is used to estimate surface stress from measured winds and temperatures. It is shown that excellent estimates of stress can be made, given the roughness length, an estimate of the Richardson number and an accurate wind at one level. The theory can further be applied to estimate the roughness length from relatively few observations of wind and temperature not necessarily under neutral conditions.Suggestions by Taylor and Deacon for the determination of surface stress from autocovariance functions are tested on O'Neill observations. The results show that fair stress estimates can be made if instrumental response is taken into account.

A Simplified Derivation of the Diabatic Wind Profile

An expression for the diabatic wind profile is derived using dimensional analysis and the assumption that the turbulent exchange coefficient for momentum can be partitioned into two parts, one associated with forced convection and the other with natural convection. The limitation of the profile to neutral or unstable conditions is stressed.

非断熱大気の風速分布の方程式の矛盾と修正についで

非断熱大気の風速分布の方程式の矛盾と修正についで

On the relation between the spectrum of turbulence and the diabatic wind profile

A simple model of the spectrum of atmospheric turbulence using Kovasznay's transfer mechanism in wave-number space leads to a diabatic wind profile which fits the observations well and gives some insight into the origin of the rather large empirical coefficient in the interpolation formulas as given by Ellison, Yamamoto, and Panofsky and by Blackadar and McVehil.

An alternative derivation of the diabatic wind profile

Quarterly Journal of the Royal Meteorological SocietyVolume 87, Issue 373 p. 437-438 Correspondence An alternative derivation of the diabatic wind profile C. H. B. Priestley, C. H. B. Priestley C.S.I.R.O., Division of Meteorological Physics, Station Street, Aspendale, S.13, Victoria, AustraliaSearch for more papers by this authorHans A. Panofsky, Hans A. Panofsky University of Minnesota, School of Physics, Institute of Technology, Minneapolis, 14Search for more papers by this author C. H. B. Priestley, C. H. B. Priestley C.S.I.R.O., Division of Meteorological Physics, Station Street, Aspendale, S.13, Victoria, AustraliaSearch for more papers by this authorHans A. Panofsky, Hans A. Panofsky University of Minnesota, School of Physics, Institute of Technology, Minneapolis, 14Search for more papers by this author First published: July 1961 https://doi.org/10.1002/qj.49708737317Citations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume87, Issue373July 1961Pages 437-438 RelatedInformation

An alternative derivation of the diabatic wind profile

AbstractEllison's wind profile is re‐derived under the assumption that in neutral and unstable air the distance from the ground determines the eddy structure.

A GENERALIZATION OF THE MIXING-LENGTH CONCEPT

Abstract A concept for the mixing length in diabatic conditions is introduced and elaborated. The basic idea is that convective energy has effect on the mixing length but not on the size of the largest eddies. The theory developed on this concept of the mixing length for the diabatic wind profile gives satisfactory agreement with observations over a wide stability range.

A comparison of some approaches to the diabatic wind profile

Several expressions for the wind profile in diabatic flow were compared with each other. Although the forms compared appear quite different, it was found that a great deal of similarity existed among them. It was concluded that accuracy of wind observations will have to be improved before it can be stated conclusively that one expression best describes the observed profiles.