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The validation of aeroelastic load models used for load calculations on wind turbines substantially increases the confidence in the accuracy and correctness of these models. In this contribution, we introduce a framework for the validation of these models, integrating a normalized area metric as an objective, quantifiable validation metric that considers the entire statistical distribution of a model and a benchmark and additionally enables a comparison of model accuracy between sensors of different physical units. The framework is applied to test cases that evaluate varying synthetic turbulent wind fields. Two test cases with a focus on turbulence parameters and abnormal shear conditions based on comprehensive wind measurements at the Testfeld Bremerhaven are used to demonstrate the workflow with four different members using IEC-compliant and measurement-derived wind field parameters, respectively. Along with these measurements, an uncertainty model for synthetic wind fields is introduced to quantify propagated wind measurement uncertainties associated with the measured boundary conditions during a validation campaign. The framework is presented as a straightforward and concise methodology to not only find but also quantify mismatches of load models. Major mismatches are found for wind fields associated with larger uncertainties in the mean wind field due to a reduced spatial resolution of measurements. [ABSTRACT FROM AUTHOR]

The validation of aeroelastic load models used for load calculations on wind turbines substantially increases the confidence in the accuracy and correctness of these models. In this contribution, we introduce a framework for the validation of these models, integrating a normalized area metric as an objective, quantifiable validation metric that considers the entire statistical distribution of a model and a benchmark and additionally enables a comparison of model accuracy between sensors of different physical units. The framework is applied to test cases that evaluate varying synthetic turbulent wind fields. Two test cases with a focus on turbulence parameters and abnormal shear conditions based on comprehensive wind measurements at the Testfeld Bremerhaven are used to demonstrate the workflow with four different members using IEC-compliant and measurement-derived wind field parameters, respectively. Along with these measurements, an uncertainty model for synthetic wind fields is introduced to quantify propagated wind measurement uncertainties associated with the measured boundary conditions during a validation campaign. The framework is presented as a straightforward and concise methodology to not only find but also quantify mismatches of load models. Major mismatches are found for wind fields associated with larger uncertainties in the mean wind field due to a reduced spatial resolution of measurements.

Minimizing and quantifying the uncertainty of wind simulations are essential for the wind energy industry during the planning phase of wind farm projects and for financial considerations. Measurements at 118 sites onshore and offshore in Germany are analyzed and used for the verification of wind simulations with the mesoscale model WRF. In order to minimize the difference between simulations and observations a correction of the annual cycle is applied and a remodeling approach is developed which allows for a correction of the simulated wind speed time series. The remodeling methodology is based on a linear regression analysis of simulated and observed wind speed time series accounting for sub‑grid variations of orography and roughness. Averaging the regression parameter for 26 measurement sites results in an overall global parameter set which is applied to the wind atlas data. While the “raw” data (without optimization) before any correction showed differences of up to 30 % with respect to the annual mean wind speed the remodeling process reduced the bias to below 5 % for the majority of measurements. When being compared with data from the NEWA wind atlas and the EMD‑WRF Europe+ data set an overall bias between 0.6 m/s and 0.8 m/s is found for the NEWA, EMD‑WRF Europe+ and anemos “raw” data. This bias is reduced to zero with a small standard deviation when the remodeling process and the site-specific adaptation are applied.

Strong winds are one of the major causes of structural damage inflicted by thunderstorms. Specialized agencies and research groups regularly provide post-disaster damage assessment reports after a severe thunderstorm has passed over an area. If the observed structural damage was caused by severe winds, an assessment of the characteristic wind gust is provided based on the wind engineering analysis of the damage. Given that high-frequency anemometer measurements of wind speed are practically never available at or close to the observed damage, this study investigates the following question: What would an anemometer measure during the storm if it was installed at the location of the observed damage? This paper presents two models for thunderstorm wind time series reconstruction based on the observed damage. One model is a simple analytical equation that provides a closed-form solution to relate the estimated wind gust that caused damage to the mean wind speed and instantaneous peak during the storm. Another model is uses constrained stochastic simulations that are based on power spectral density of turbulent winds to reproduce a thunderstorm wind record that is in statistical sense indistinguishable from a measured wind. The constrain in the stochastic model is the value of the reported dameging wind gust. The models are validated against measured thunderstorm wind records and used to reconstruct thunderstorm wind time series from the damage data. • Deterministic and stochastic models developed using information about damaging gust. • First constrained stochastic model of turbulent thunderstorm winds. • Stochastic model validated against high-frequency anemometer measurements. • Models used to reconstruct time histories of winds that caused damage to structures. [ABSTRACT FROM AUTHOR]

A yearlong wind and wave dataset derived from a cost-effective GPS wave buoy (Spotter) is compared to waves obtained from an accelerometer wave buoy (Datawell) and winds obtained from a collocated meteorological buoy. Overall, there was a strong correlation in bulk wave parameters obtained from the Spotter buoy and the Datawell buoy (RMSE of 0.06 m, 0.27 s, and 21.89° for significant wave height, mean wave period, and peak wave direction, respectively). Similarly, the bulk characteristics compared well when separating the directional wave spectra into sea and swell components with more scatter in mean wave periods for lower frequencies. Measurements of mean directional spread from the Spotter buoy were 7.51° larger than the Datawell, spreading more wave energy across different directions outside the peak direction. Additional analysis indicates that the increased directional spreading arises from a bias in the a1 and b1 spectral moments. Using the equilibrium frequency range of the wave energy spectrum, the Spotter buoy can derive wind speed and direction. This study found the Spotter buoy can report wind speed and direction with reasonable accuracy but underestimates wind speeds less than 4 m/s and greater than 8 m/s and was less accurate reporting wind directions oriented offshore. A comparison with a Spotter buoy in deeper water revealed the Spotter buoy further offshore was most accurate in reporting wind directions indicating this proxy-based measurement of wind speed and wind direction may be significantly influenced by fetch and local geography (e.g., large-scale cuspate coastlines).

To investigate the complex phenomenon of bird migration, researchers rely on sophisticated methods for tracking long‐distant migrants. While large birds can be equipped with satellite tags, these are too heavy for many species. Instead, researchers often use light‐level geolocation for tracking individual small migratory birds. Unfortunately, light‐level geolocation is often coarse and unreliable, with positioning errors of anything up to hundreds of kilometres. Recent Bayesian models try to constrain the route to plausible corridors: they couple light‐level measurements with information about the bird's likely movement. While these models improve inference, they still lack information on weather conditions, specifically the impact of wind. For example, birds might encounter tailwinds—considerably increasing their (ground) speed and making longer routes more likely, or headwinds—having the opposite effect.Miniaturised multi‐sensor tags allow monitoring not only light but also acceleration and air pressure. These measurements provide essential additional information about the exact timing of flight activity and the corresponding flight altitudes. This article proposes a Bayesian model for inferring bird migration. The model integrates air pressure to estimate flight altitudes and considers wind data to calculate the most likely flight trajectory. The model constrains the migratory routes to those likely given by the winds en route and the observed timing of flight activity.We apply the model to infer the migration of European Hoopoes Upupa epops. Adding wind data for route inference excludes flight trajectories with unrealistic high airspeeds, decreases the uncertainty of the position estimates and returns more plausible migratory routes.Faithful reconstruction of migratory routes helps unravel the influence of physiological and environmental factors on bird migration. This is crucial for habitat protection where limited resources need to be allocated to relevant areas. [ABSTRACT FROM AUTHOR]

Abstract The Australian Government Bureau of Meteorology completed the installation of a network of 9 new wind profiling radars across mainland Australia in 2017, which complement an existing network of 5 profilers and 5 research systems. This results in a network of 14 operational, and 19 total, profilers across Australia and Davis Station in Antarctica. Four of the new profilers are higher power stratospheric tropospheric systems, designed to measure winds from near ground level to the tropopause, and maintain the upper air network in Australia where sonde launches are no longer available. Wind measurements in the near field of the radar are demonstrated to be both possible and accurate by comparison with co-located radiosondes. Quality control procedures producing winds of sufficient accuracy for presentation to forecasters and ingestion into global numerical weather prediction models are described. The Australian network data are available on the global telecommunications system and are currently being ingested into all major models. First results from impact studies on forecast error reduction in the Australian Community Climate and Earth Systems Simulator show remote stations have the greatest impact.

• Horizontal winds were measured by five meteor radars distributed from 13°E to 178°E in the middle and high-latitudes. • We studied planetary wave propagation during October 2017 – February 2018. • Planetary scale oscillations in the meridional wind are organized in groups. • Each group successively propagates from one site to another one. • Each group is observed at one site and almost disappears at the previous one. We present results of wind measurements near the mesopause carried out with meteor radars (MRs) at Collm (51°N, 13°E), Obninsk (55°N, 37°E), Kazan (56°N, 49°E), Angarsk (52°N, 104°E) and Anadyr (65°N, 178°E) from October 1, 2017 till March 31, 2018. The Collm and Kazan MRs are SKiYMET radars with vertical transmission and radio echo height finding, while the other radars operate with horizontal transmission and without height finding. We paid particular attention to the meridional wind variability with periods of 4–6 days and 9–11 days. The waves with these periods are seen as spots of the wave activity in the wavelet spectra and include oscillations with different periods and different discrete zonal wavenumbers. These wave packets successively propagate as a group of waves from one site to another one in such a way that they are observed at one site and almost disappear at the previous one. The 4–6 wave group includes planetary-scale oscillations (individual spectral components) which have eastward phase velocities and mostly zonal wavenumbers 2 and 3, and the vertical wavelength exceeds 70 km at middle latitudes. The source of the oscillations is the polar jet instability. The wave group itself propagates westward, and the amplitudes of wind oscillations are approximately 5–6 m/s as obtained from the wind data averaged over the meteor zone. The 9–11 day wave set propagates westward as a group and mainly consists of spectral components which have westward phase velocity and zonal wavenumber 1. Amplitudes of these wind perturbations strongly vary from station to station and can reach, approximately, 8 m/s. The vertical wavenumber is 0.014 km−1 as taken from the Kazan and 0.05 km−1 according to the Collm data. We obtained a global view on the waves by using the AURA MLS geopotential data. We found a good correspondence between wave features obtained from the MR wind measurements and the MLS data. To our knowledge, such a wave propagation of planetary wave in the mesosphere/lower thermosphere (MLT) region has so far not obtained much attention. [ABSTRACT FROM AUTHOR]

LiDARs (Light Detection and Ranging) are becoming important tools for wind resource assessments in all kinds of terrain. Compared to mast measurements, mobility and flexibility are their greatest benefits. However, care needs to be taken when setting up a measurement campaign. The influence of complex terrain on the wind leads to inhomogeneous flow. This can cause considerable errors in ground based mono-static LiDAR measurements due to their measurement principle and simplifying assumptions.Within this work, wind measurements from Fraunhofer IWES’s 200 m research mast in complex terrain at “Rödeser Berg” in Kassel, Germany, and a pulsed Doppler LiDAR (Leosphere windcube), located at the mast, are compared. The relative deviation between the measurements of the horizontal wind speed by the LiDAR and the mast (LiDAR-mast deviations) varies with wind direction and height. It ranges from about −4 % underestimation to +2.5 % overestimation by the LiDAR - for heights between 120 and 200 m. Two steady-state Reynolds-Averaged-Navier-Stokes (RANS) Computational Fluid Dynamics (CFD)-models and a model based on linearized Navier-Stokes Equations were used to estimate the LiDAR error from a flow simulation. Model results were evaluated depending on model parameterisation such as forest height and density. Given the right parameterisations – especially for the forest model – the CFD-models showed a good performance when compared to the observed LiDAR-mast deviations. These simulations can thus be used to correct the LiDAR error induced by the complex flow.To demonstrate variations of LiDAR errors due to choice of measurement location, one of the models was run to calculate the wind flow in an area of 2×2km2$2\times2\,\text{km}^{2}$ around the 200 m measurement mast. This allows the visualization of the estimated LiDAR errors to characterize measurement locations. Results showed the significant variation of measurement errors due to the location.

We demonstrate a method for incorporating wind velocity measurements from multiple-point scanning lidars into three-dimensional wind turbulence time series serving as input to wind turbine load simulations. Simulated lidar scanning patterns are implemented by imposing constraints on randomly generated Gaussian turbulence fields in compliance with the Mann model for neutral stability. The expected efficiency of various scanning patterns is estimated by means of the explained variance associated with the constrained field. A numerical study is made using the hawc2 aeroelastic software, whereby the constrained turbulence wind time series serves as input to load simulations on a 10 MW wind turbine model using scanning patterns simulating different lidar technologies-pulsed lidar with one or multiple beams-and continuous-wave lidars scanning in three different revolving patterns. Based on the results of this study, we assess the influence of the proposed method on the statistical uncertainty in wind turbine extreme and fatigue loads. The main conclusion is that introducing lidar measurements as turbulence constraints in load simulations may bring significant reduction in load and energy production uncertainty, not accounting for any additional uncertainty from real measurements. The constrained turbulence method is most efficient for prediction of energy production and loads governed by the turbulence intensity and the thrust force, while for other load components such as tower base side-to-side moment, the achieved reduction in uncertainty is minimal. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The mobile Rayleigh Doppler lidar based on a Fabry-Perot etalon is developed for wind measurement. The structure and technical parameters of this lidar system are described in brief. The 1740 wind profiles from 8 to 40 km altitudes by the lidar in Xinjiang, China, were obtained in 2010 and 2011, and were used to analyze the characteristics and variations of wind. The results shown that the wind velocity is within a three-layer structure: westerly jet layer (9-14 km), quasi-zero velocity layer (18-22 km) and gale layer (22-40 km). In August and September, the wind direction is within a three-layer structure: zonal westerly wind layer (5-18 km) where wind direction is west, zonal wind reverse layer (18-22 km) where wind direction is unstable and easterly wind layer (22-40 km) where wind direction is east. In October, wind direction is west (8-40 km). Wind observations by lidar are a realistic offset to the rawins. [ABSTRACT FROM AUTHOR]

The wind potential around an intensely mountainous area has been studied and an experimental analysis is presented the output of which could be used in the wind farm planning procedure aiming at maximization of the wind power production output of an area. The wind speed of a chosen site of Central Greece was studied based on field measurements around a large mountainous area of Central Greece. Understanding flow in the foothills and the wider area of the mountains is of great importance for estimating wind resource in rough terrain. In this article, special focus was given to the speed-up effect and forced air flow around mountainous masses. [ABSTRACT FROM AUTHOR]

Installation of dedicated offshore meteorological tower is very expensive due to the water depth and in some locations, icing conditions. However, many port cities have existing offshore structures such as water intake facilities or historical coastal defense structures that could be utilized as a low-cost alternative for wind resource assessment studies. Such a study was conducted using the city of Cleveland's Water Division water intake facility located 3.5 miles offshore of downtown Cleveland in Lake Erie. Lake Erie is the smallest of the Great Lakes and as such can completely ice over during the winter. The water intake crib was installed in 1904 and has a small building on top of the water intake pipe. In 2005, a meteorological tower was installed on top of this building and has been recording wind measurements at 30, 40, and 50 m above the nominal water level. The influence of this structure on the recorded wind measurements was assessed using a computational fluid dynamics model. The assessment was conducted across the eight cardinal and ordinal directions and evaluated as a function of incoming wind profile. The model assumed a neutral boundary condition and the standard power law equation was used to predict the true mean wind speeds and wind shear coefficients. Input wind profiles with programmed wind shear coefficients of 0.0, 0.1, and 0.2 were found to be reduced above the crib structure and resulted in wind shear coefficients of -0.07, 0.05, and 0.17, respectively, at the locations of the cup anemometer measurements. This reduction of wind shear coefficient values was found to be caused by an increase in the wind speed above the building, which affected the lower height measurements more than the upper height measurements. The relationship between the known programmed wind shear coefficients and the lower resultant wind shear coefficients predicted from the computational fluid dynamics model was then used to adjust the experimental measurements to correct historical data. The corrected mean wind speeds occurring during a 2-year period beginning in October 2005 at 30, 40, and 50 m are 6.79, 7.02, and 7.16 m s-1, respectively, as compared to the previously reported values of 7.14, 7.25, and 7.34 at 30, 40, and 50 m, respectively. These values represented the wind speeds which would have been measured using an isolated 50 m meteorological mast positioned directly on the water's surface rather than atop the offshore water intake building. The wind shear coefficient averaged over the corrected wind speeds was 0.1038 as compared to the previously reported value of 0.0541. [ABSTRACT FROM AUTHOR]

Operational since 2004, the National Centre for Wind Turbines at Høvsøre, Denmark has become a reference research site for wind-power meteorology. In this study, we review the site, its instrumentation, observations, and main research programs. The programs comprise activities on, inter alia, remote sensing, where measurements from lidars have been compared extensively with those from traditional instrumentation on masts. In addition, with regard to wind-power meteorology, wind-resource methodologies for wind climate extrapolation have been evaluated and improved. Further, special attention has been given to research on boundary-layer flow, where parametrizations of the length scale and wind profile have been developed and evaluated. Atmospheric turbulence studies are continuously conducted at Høvsøre, where spectral tensor models have been evaluated and extended to account for atmospheric stability, and experiments using microscale and mesoscale numerical modelling. [ABSTRACT FROM AUTHOR]

This paper describes a method that was applied as a part of the creation of a wind map for the Czech Republic. The method (abbreviated VAS/WindAtlas) combines an interpolation method (VAS) with the Wind Atlas methodology applied by using the microscale model WAsP. While WAsP eliminates the site-specific effects around measurement sites to provide generalised wind conditions (GWC), VAS interpolates the GWC over the entire domain and takes into account the general increase of wind speed with altitude. As a result, an altitude-dependent generalised wind map is provided. Then, a final high-resolution calculation is performed by WAsP. The VAS/WindAtlas method is considerably more simplified and less computationally demanding than approaches employing more complex numerical models, but it requires a sufficiently dense network of wind measurements, a thorough data quality evaluation and careful corrections that compensate for the known limitations of the applied data and methods. A comparison of the original wind map with new independent wind measurements, which were obtained after the wind map calculation, was performed with a detailed analysis of the expected errors and uncertainties at the validation sites. The presented VAS/WindAtlas method proved to be good solution to estimate wind resources of Czech Republic. [ABSTRACT FROM AUTHOR]

The annual and diurnal behaviours of near surface wind speed, temperature, and the radiative budget at Concordia Station (Dome C) in different seasons are shown. The wind speed was lowest in summer when a daily cycle was also observed. The largest mean values were concurrent with boundary layer growth in the afternoon. In winter and spring the wind speed reached the highest mean values. Perturbations in the wind flow were due to warming events which occurred periodically at Dome C. The lowest temperatures were in April and at the end of August. The coreless winter behaviour was perturbed by warming events which in many cases produced an increase in temperature of c. 20°C. The average temperature profiles show permanent thermal inversion, with the exception of a few hours in the afternoons during the summer. The strongest ground-based thermal inversions were observed in the polar winter. The largest potential temperature gradients were limited to a 30–40 m deep layer close to the surface. The net radiation was negative almost all the time with the exception of the period from mid-December to mid-January. [ABSTRACT FROM AUTHOR]

A detailed analysis of wind measurements from ground stations and upper air soundings leads to a description of the four-dimensional wind field during one day of the intensive observational phase of POLLUMET, July 5th, 1991. With a weather situation producing a countercurrent in the Swiss plateau and a high pressure situation allowing thermally induced winds to develop in the Alpine valleys, the questions of wind shear heights and overlapping of several wind regimes are analysed. An objective analysis for the regional scale wind field is supplemented by process models in order to fill the gap of knowledge at locations, where simple interpolation does not hold. The wind field obtained is validated with measurements not used as input and with constant pressure balloon flights. The identification of air masses then is realized by specifying the air mass origin for some special cases using the calculated wind field for back trajectory determination. Moreover the wind field is used to compute diurnal courses of trace gas fluxes through selected valley intersects near the entrance to the upper Reuss valley. This quantitatively specifies the exchange of air masses and their constituents between the Reuss valley and the adjacent region.

SUMMARY The paper reviews some of the most recent aspects involved in the dynamic testing and continuous monitoring of bridges. This includes a discussion of testing techniques, instrumentation, modal identification and damage detection. On the basis of their experience, the authors described several case studies in which some of the most recent developments have been used to accomplish different purposes: the Millau Viaduct, in France, the Pedro e Inês footbridge and the Infante D. Henrique Bridge, in Portugal, and the Grande Ravine Viaduct, at the Reunion Island. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Utilizations of wind energy quickly spread around the world which results in growing number of wind measurements but not only in near-surface region (10 m) also higher altitude are able to provide datasets. The SODAR (Sound Detection And Ranging) represents terrestrial remote sensing techniques which are becoming more and more popular tools today to exploring wind conditions of a few hundred meters thick atmosphere. The Department of Meteorology at University of Debrecen purchased a PCS. 2000-24 type phase - array, monostatic Doppler SODAR equipment which give an unique possibility to carry out 3D wind monitoring in Debrecen. We collect information about properties of wind profile between 20 and 400 m height above surface, parameters and process of planetary boundary layer in order to accomplish objectives of REGENERG HURO project. Our main objective was to discover geographical distribution of wind speed in Hajdú-Bihar and Bihor County in order to promote wind energy in this region. In research we adapted a well-known CFD based numerical model to mapping wind regime, and we used SODAR dataset to make verification of modelled results. The implementation of the research project is supported by HURO/0802/ 083_AF REGENERG. [ABSTRACT FROM AUTHOR]

Expectations towards small scale urban wind based electricity generation are rather high. The vendors promise high production rates and high returns on the investment. In this paper we describe our practical measurement experiment of one horizontal and three vertical axis turbines. The result shows that the performance of the turbines does not meet the expectations and the urban wind blow is really far from being optimal in energy production. [ABSTRACT FROM AUTHOR]

Abstract: Wind energy resource assessment applications require accurate wind measurements. Most of the published studies used data from existing weather station network operated by meteorological departments. Due to relatively high cost of weather stations the resolution of the weather station network is coarse for wind energy applications. Typically, meteorological departments install weather stations at specific locations such as airports, ports and areas with high density population. Typically, these locations are avoided during wind farms siting. According to WMO regulations, weather stations provide measurements for different weather elements at specific altitudes such as 2m for air temperature and 10m for wind measurements. For wind energy resource assessment applications, minimum of one year of wind measurements is required to build wind climatology for a certain site. Therefore data collected from a certain site cannot be used before one year of operation. Due to these limitations, wind energy resource assessment application needs to use data from different sources. Recently, wind assessment studies were conducted using data generated by Numerical Weather Prediction models. This paper reviews the use of the Numerical Weather Prediction data for wind energy resource assessment. It gives a general overview of NWP models and how they overcome the limitations in the classical wind measurements. [Copyright &y& Elsevier]

Information concerning the average wind speed and the variances of lateral and longitudinal wind velocity fluctuations is required by dispersion models to characterise turbulence in the atmospheric boundary layer. When the winds are weak, the scalar average wind speed and the vector average wind speed need to be clearly distinguished and both lateral and longitudinal wind velocity fluctuations assume equal importance in dispersion calculations. We examine commonly-used methods of estimating these variances from wind-speed and wind-direction statistics measured separately, for example, by a cup anemometer and a wind vane, and evaluate the implied relationship between the scalar and vector wind speeds, using measurements taken under low-wind stable conditions. We highlight several inconsistencies inherent in the existing formulations and show that the widely-used assumption that the lateral velocity variance is equal to the longitudinal velocity variance is not necessarily true. We derive improved relations for the two variances, and although data under stable stratification are considered for comparison, our analysis is applicable more generally. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the key results from a ten-year data set for Lake IJssel and Lake Sloten in The Netherlands, containing information on wind, storm surges and waves, supplemented with SWAN 40.51 wave model results. The wind speeds U 10, effective fetches x and water depths d for the data set ranged from 0–24 m s− 1, 0.8–25 km and 1.2–6 m respectively. For locations with non-sloping bottoms, the range in non-dimensional fetch x⁎ (= g x U 10 − 2) was about 25–80,000, while the range in dimensionless depth d⁎ (= g d U 10 − 2) was about 0.03–1.7. Land–water wind speed differences were much smaller than the roughness differences would suggest. Part of this seems due to thermal stability effects, which even play a role during near-gale force winds. For storm surges, a spectral response analysis showed that Lake IJssel has several resonant peaks at time scales of order 1 h. As for the waves, wave steepnesses and dimensionless wave heights H⁎ (= g H m0 U 10 − 2) agreed reasonably well with parametric growth curves, although there is no single curve to which the present data fit best for all cases. For strongly depth-limited waves, the extreme values of d⁎ (0.03) and H m0 / d (0.44) at the 1.7 m deep Lake Sloten were very close to the extremes found in Lake George, Australia. For the 5 m deep Lake IJssel, values of H m0 / d were higher than the depth-limited asymptotes of parametric wave growth curves. The wave model test cases of this study demonstrated that SWAN underestimates H m0 for depth-limited waves and that spectral details (enhanced peak, secondary humps) were not well reproduced from H m0 / d =0.2–0.3 on. SWAN also underestimated the quick wave response (within 0.3–1 h) to sudden wind increases. For the remaining cases, the new [Van der Westhuysen, A.J., Zijlema, M., and Battjes, J.A., 2007. Nonlinear saturation-based whitecapping dissipation in SWAN for deep and shallow water, Coast. Eng., 54, 151–170] SWAN physics yielded better results than the standard physics of Komen, G.J., Hasselmann, S., Hasselmann, K., 1984. On the existence of a fully developed wind-sea spectrum. J. Phys. Oceanogr. 14, 1271–1285, except for persistent overestimations that were found for short fetches. The present data set contains many interesting cases for detailed model validation and for further studies into the evolution of wind waves in shallow lakes. [Copyright &y& Elsevier]

Abstract: The Sotavento wind farm is an experimental wind farm which has different types of wind turbines. It is located in an area whose topography is moderately complex, and where wake effects can be significant. One of the objectives of Sotavento wind farm is to compare the performances of the different machines; particularly regarding power production, maintenance and failures. However, because of wakes and topography, the different machines are not working under identical conditions. Two linearized codes have been used to estimate topography effects: UPMORO and WAsP. For wind directions in which topography is abrupt, the non-linear flow equations have been solved with the commercial code FLUENT, although the results are only qualitatively used. For wake effects, the UPMPARK code has been applied. As a result, the incident velocity over each wind turbine is obtained, and the power production is estimated by means of the power curve of each machine. Experimental measurements give simultaneously the wind characteristics at the measuring stations, the wind velocity, at the nacelle anemometer, and the power production of each wind turbine. These experimental results are employed to validate the numerical predictions. The main objective of this work is to deduce and validate a relationship between the wind characteristics measured in the anemometers and the wind velocity and the power output in each machine. [Copyright &y& Elsevier]

A preliminary analysis of the compatibility of wind properties obtained from continuous high-resolution recordings at automatic stations and traditional wind data (obtained by means of averaging the wind speed over a 10-minute interval and the wind direction over a 2-minute interval once in every 3 hours) has been carried out. Both wind speed data sets represent the same data population. The distribution of the differences between individual wind speed observations is non- Gaussian. The difference of estimates of the average wind speed is negligible for time scales of several weeks or longer. The shape parameter of the Weibull distribution for wind speeds is found to depend on the threshold for calm situations; it is close to 2 when wind speeds under 0.5 m/s are treated as calm. This choice also leads to a reasonable match of the corresponding wind roses. [ABSTRACT FROM AUTHOR]

Abstract: Fluctuations of lower ionospheric drifts in the virtual height range 85–110km at 52.1°N, 13.2°E during 1984–2003 are presented. These fluctuations may be partly owing to neutral atmosphere gravity waves in the period window 0.7–3h. The results show maximum wave activity in the mesosphere in summer, with a shift to equinoxes at higher altitudes. Maximum gravity wave amplitudes are found near the regions of strongest vertical mean wind shear. The propagation direction is generally close to E–W, however, during winter at lower heights a more South-Easterly direction is preferred, while at greater heights during summer a North-Easterly direction is visible. Time series of seasonal (3-monthly) mean zonal drift variances show maximum amplitudes around years 1989–1991 and 2000–2002, when maxima of solar activity within the 11-year solar cycle occurred. We interpret the results in terms of gravity wave activity although additional influences like ionospheric perturbations also may lead to possible wind fluctuations correlated with solar activity. Therefore, the conclusions are partly qualitative and require further experimental verification. [Copyright &y& Elsevier]

Abstract: We have combined differential absorption lidar (DIAL) measurements of mercury concentrations downwind of a chlor-alkali plant (Rosignano Solvay) with measurements of wind profiles made with a Doppler Lidar based on modern fibre-optic technology. Since the flux of pollutant is equal to the cross-wind integral of the product of concentration and wind speed, this should permit us to make a more precise estimate of the fugitive emission of mercury from the plant than could be obtained by using anemometer measurements of the wind. The flux was estimated to be 54gHgh−1 using an anemometer on the plant building; 49gHgh−1 using an anemometer on a nearby 10m mast; and 48gHgh−1 using wind speed corrections estimated from the Doppler Lidar measurements. Because of difficulties with the range resolution of the Doppler Lidar, the precision of this estimate was not as good as it should have been, though the difference from the rooftop anemometer remains statistically significant. Corrections of this magnitude are irrelevant to the Rosignano plant, where the emission rate varies strongly with the meteorological conditions. Where a precise estimate of a steady flux is required, however, reliable measurements of the wind profile in the wake of the source are essential. Doppler Lidar provides a possible method for acquiring such measurements. [Copyright &y& Elsevier]

Abstract: Using the D1 method in the LF range, monthly mean zonal and meridional winds in the mesosphere/lower thermosphere height range are measured continuously at Collm, Germany. The wind data are accompanied by reference height measurements since 1983, allowing the construction of an empirical long-term climatology of mean winds and tidal amplitudes and phases at 52N, 15E, which covers the height range of 80–110 km in winter, and about 83–107 km in summer. The climatology includes the time interval from 1983 to date, thus covering nearly two solar cycles. Vertical wind parameter profiles can also be constructed for individual years, so that from the time series interannual variability and long-term trends can be deduced. Here, we present the results for 2003 in comparison with the climatological means. [Copyright &y& Elsevier]

The studies of turbulence decay were based in the past on measurements carried out in neutrally stratified wind tunnels and, more recently, on large-eddy simulation runs. Here the atmospheric turbulence decay process during the solar total eclipse of 11 August 1999 is examined. Thus a rapid transition from convective boundary-layer turbulence to that of a neutral or slightly stable one is considered. A u-v-w propeller anemometer and a fast response temperature sensor located in northern France on top of a 9-m mast recorded the turbulence observations. The measurements, in terms of turbulent kinetic energy decay with time, were found to be in good agreement with those prescribed by a theoretical model of turbulence decay recently proposed. In particular, it was found that the exponent of the power law describing the decay process has the value -2. [ABSTRACT FROM AUTHOR]

The paper investigates the local topographic effect on the mean and integral flow characteristics recorded by sonic anemometers mounted on tall masts near the shoreline of three different Norwegian fjords. Two years of measurements are analysed, using data from 25 three-dimensional sonic anemometers mounted at heights from 12 ​m to 95 ​m above the ground. The goal is to explore the potential and challenges of using wind measurements from the masts located on the shores of the fjords in the design of planned bridge crossings. Therefore, the study explores the deviations of the mean and turbulent flow characteristics from the traditional case of flat and homogeneous terrain. Only records with mean wind speeds of 12 ​m ​s−1 and above at all elevations above the ground are considered due to their relevance in buffeting response, which led to the identification of a limited number of sectors representative of strong wind conditions. Mean incidence angles with absolute values above 6° and low mean wind shear are measured in several of the selected sectors. This highlights the major influence of the local terrain and vegetation around the masts on the wind conditions at the mast locations. Nevertheless, non-dimensional variance and covariance estimates of the velocity components are found to be consistent with values previously measured from bridge decks crossing narrow fjords. The paper explores also an alternative approach to compute the friction velocity, the estimation of which is challenging in a fjord-like topography. This first part of the paper focuses on integral flow characteristics, a second follow-on part will investigate in details which eddy wave-numbers are most affected by the local terrain, based on the analysis of the spectra of the velocity fluctuations. • Integral wind velocity characteristics are analysed in three Norwegian fjords. • Two years of data, from 25 sonic anemometers mounted on tall masts are used. • The study is valuable for future fjord-crossing long-span bridges. • The three-dimensional flow is heavily affected by the local terrain. • The flow characteristics are sometimes consistent with those from other fjord-crossing bridges. [ABSTRACT FROM AUTHOR]

Speed range is an important specification of coherent Doppler wind lidar (CDWL). However, it is difficult to identify the lower speed bound of CDWL, because the Doppler signal is often overlapped or covered by relative intensity noise (RIN) at the low-frequency end of the spectrum. Therefore, how to distinguish the Doppler signal and the RIN at the low frequency is always an important issue. In the optical information processing, Rayleigh criterion specifies the spatial resolution limit, which is the minimum distance between the two distinguishable Airy disks. Due to the rigorous one-to-one correspondence between optical signals and electrical signals in photoelectric conversion, Rayleigh criterion can be extended to the electrical signal processing. We mapped the Doppler signal and RIN into the Airy disk profile and used the generalized Rayleigh criterion to study the signal resolution limit to define the lower speed bound of the system. The comparative experiments were carried out and the results were consistent with the generalized Rayleigh criterion. It shows that the generalized Rayleigh criterion is available and effective and can be used as a new method for the signal resolution on coherent Doppler wind measurements. [ABSTRACT FROM AUTHOR]