Vertical Profiles Of Wind Speed Research Articles

Сопоставление вертикальных профилей скорости и направления ветра, полученных на основе лидарных и аэрологических измерений

Сопоставление вертикальных профилей скорости и направления ветра, полученных на основе лидарных и аэрологических измерений

LiDARによる山岳地形における風速鉛直プロファイル分析

Wind turbines are often constructed in mountainous region in Japan, because mountainous region is account for more than 70 percent of land in Japan. In complex terrains, wind characteristics depend heavily on wind direction with strong locality. Especially the vertical wind profiles are complicated in the complex terrain. So It is necessary to measure the wide-ranging wind conditions from a low altitude to a high altitude. However, wide-ranging wind measurements are difficult for conventional equipment such as meteorological mast. Then, remote sensing devices such as Light Detection and Ranging (LiDAR) are counted on for wind measurements in complex terrain. In this paper, we investigated the effects of terrain configurations on vertical wind speed profiles by wind measurements using LiDAR in mountainous terrain, and we also investigated LiDAR measurements validity by comparison among vertical profiles from three LiDARs that have different wind measurements mechanism. The trends of vertical wind speed profiles from different LiDARs are similar and the wind profiles are different by wind directions (NNW and SE). NNW wind is the flow that do not over a ridge of the mountain and SE wind is the flow that over the ridge. The NNW wind profile is uniform, and the SE wind profile is separated flow. By using LiDAR, it is able to research condition of flow in mountainous terrain such as separated flow.

Validation of farm-scale methane emissions using nocturnal boundary layer budgets

Abstract. This study provides the first experimental validation of Swiss agricultural methane emission estimates at the farm scale. We measured CH4 concentrations at a Swiss farmstead during two intensive field campaigns in August 2011 and July 2012 to (1) quantify the source strength of livestock methane emissions using a tethered balloon system and (2) to validate inventory emission estimates via nocturnal boundary layer (NBL) budgets. Field measurements were performed at a distance of 150 m from the nearest farm buildings with a tethered balloon system in combination with gradient measurements at eight heights on a 10 m tower to better resolve the near-surface concentrations. Vertical profiles of air temperature, relative humidity, CH4 concentration, wind speed, and wind direction showed that the NBL was strongly influenced by local transport processes and by the valley wind system. Methane concentrations showed a pronounced time course, with highest concentrations in the second half of the night. NBL budget flux estimates were obtained via a time–space kriging approach. Main uncertainties of NBL budget flux estimates were associated with nonstationary atmospheric conditions and the estimate of the inversion height zi (top of volume integration). The mean NBL budget fluxes of 1.60 ± 0.31 μg CH4 m-2 s-1 (1.40 ± 0.50 and 1.66 ± 0.20 μg CH4 m-2 s-1 in 2011 and 2012 respectively) were in good agreement with local inventory estimates based on current livestock number and default emission factors, with 1.29 ± 0.47 and 1.74 ± 0.63 μg CH4 m-2 s-1 for 2011 and 2012 respectively. This indicates that emission factors used for the national inventory reports are adequate, and we conclude that the NBL budget approach is a useful tool to validate emission inventory estimates.

An empirical‐analytical model of the vertical wind speed profile above and within an Amazon forest site

ABSTRACTThe present study considers the mean wind velocity profiles measured from a 60 m high tower in the Rebio‐Jarú forest (10 ° 04.7 ′ S, 61 ° 52.0 ′ W), located in the Brazilian northwestern state of Rondônia. The data were collected during the wet season as part of an intensive campaign of the large scale biosphere–atmosphere experiment in Amazonia. Nine cup anemometers were vertically placed to provide a good estimate of the inflection point height of the mean wind velocity profile. The resulting data were used to formulate a mean vertical wind speed profile, ū(z), based on key parameters such as the inflection point height and the leaf area index. The modified hyperbolic tangent function was used to provide a more flexible fit to the experimental data. An exponential term was also added to the ū(z) function, so that it can assume the appropriate ‘s’ shape near the ground. Thus, some parameters were incorporated into the analytical profile function to enable more flexibility. The presented results demonstrate that the profile is a good fit to the experimental data measured above and within the Amazon forest canopy.

Validation of eight atmospheric reanalyses in the Antarctic Peninsula region

AbstractEight atmospheric reanalyses were compared against observed vertical profiles of temperature, specific humidity and wind speed collected by two research aircraft in February–March 2010 in the Antarctic Peninsula region. These data offered a rare possibility to validate reanalyses against independent in situ data which have not been assimilated into the reanalyses. The reanalyses had generally too moist profiles with too low wind speeds, but otherwise the errors in the reanalyses had large spatial differences. On the eastern side of the peninsula, the near‐surface temperatures were largely overestimated. None of the reanalyses outperformed the others in all variables, at all altitudes and on both sides of the peninsula. Generally, NCEP‐CFSR and MERRA had the smallest errors in temperature profiles, JRA‐55 had marginally the most accurate specific humidity profiles and NCEP‐CFSR had the best wind profiles. The reanalyses were coherent, although biased, on the western side of the Antarctic Peninsula, but on the eastern side the spread was large. All the reanalyses underestimated the variability between the individual profiles of temperature and wind speed. The modern reanalyses with a sufficient spatial resolution and an adequate data assimilation method outperformed the others, especially on the eastern side.

Wind Measurements from Arc Scans with Doppler Wind Lidar

AbstractDefining optimal scanning geometries for scanning lidars for wind energy applications remains an active field of research. This paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler wind lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean wind speed and direction. When flow is horizontally uniform, this approach can provide accurate wind measurements required for wind resource assessments in part because of its high resampling rate. Retrieved wind velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal wind speed, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved wind velocity are related to high turbulent wind fluctuation and an inhomogeneous horizontal wind field. The radial velocity variance is found to be a robust measure of the uncertainty of the retrieved wind speed because of its relationship to turbulence properties. It is further shown that the standard error of wind speed estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.

A Case Study of the Weather Research and Forecasting Model Applied to the Joint Urban 2003 Tracer Field Experiment. Part 1: Wind and Turbulence

Numerical-weather-prediction models are often used to supply the mean wind and turbulence fields for atmospheric transport and dispersion plume models as they provide dense horizontally- and vertically-resolved geographic coverage in comparison to typically sparse monitoring networks. Here, the Weather Research and Forecasting (WRF) model was run over the month-long period of the Joint Urban 2003 field campaign conducted in Oklahoma City and the simulated fields important to transport and dispersion models were compared to measurements from a number of sodars, tower-based sonic anemometers, and balloon soundings located in the greater metropolitan area. Time histories of computed wind speed, wind direction, turbulent kinetic energy (e), friction velocity ( $$u_*$$ ), and reciprocal Obukhov length (1 / L) were compared to measurements over the 1-month field campaign. Vertical profiles of wind speed, potential temperature ( $$\theta $$ ), and e were compared during short intensive operating periods. The WRF model was typically able to replicate the measured diurnal variation of the wind fields, but with an average absolute wind direction and speed difference of $$35^\circ $$ and $$1.9\hbox { m s}^{-1}$$ , respectively. Using the Mellor-Yamada-Janjic (MYJ) surface-layer scheme, the WRF model was found to generally underpredict surface-layer TKE but overpredict $$u_*$$ that was observed above a suburban region of Oklahoma City. The TKE-threshold method used by the WRF model’s MYJ surface-layer scheme to compute the boundary-layer height (h) consistently overestimated h derived from a $$\theta $$ gradient method whether using observed or modelled $$\theta $$ profiles.

One Year of Vertical Wind Profiles Measurements at a Mediterranean Coastal Site of South Italy

To exploit wind energy both onshore and offshore in coastal area the effect of the coastal discontinuity is important. The shape of the vertical wind profiles and the related c parameter of the Weibull distribution are impacted by the atmospheric internal boundary layers developing from the coast along the wind direction. Here, we present first results: one year of vertical wind speed and direction profiles, monitoring programme at a South Mediterranean coastal site with a wind Lidar ZephIr (ltd). Daily variation of wind speed and direction vertical profiles, vertical Weibull wind distribution c parameter and wind rose are here showed.

Drone-Based Experimental Investigation of Three-Dimensional Flow Structure of a Multi-Megawatt Wind Turbine in Complex Terrain

The aerodynamic characteristics of wakes in complex terrain have a profound impact on the energy yield of wind farms and on the fatigue loads on wind turbines in the wind farm. In order to detail the spatial variations of the wind speed, wind direction, and turbulent kinetic energy (TKE) in the near-wake, comprehensive drone-based measurements at a multi-megawatt (MW) wind turbine that is located in complex terrain have been conducted. A short-time Fourier transform (STFT)-based analysis method is used to derive time-localized TKE along the drone's trajectory. In upstream and in the near-wake, the vertical profiles of wind speed, wind direction, and TKE are detailed. There is an increase in the TKE from upstream to downstream of the wind turbine, and whereas, the characteristic microscale length scales increase with increasing height above the ground upstream of the turbine, in the near-wake the microscale lengths are of constant, smaller magnitude. The first-ever measurements of the pressure field across a multi-MW wind turbines rotor plane and of the tip vortices in the near-wake are also reported. It is shown that the pitch between subsequent tip vortices, which are shed from the wind turbines blades, increases in the near-wake as the wake evolves. These details of the near-wake can have an important effect on the subsequent evolution of the wake and must be incorporated into the three-dimensional (3D) field wake models that are currently under intensive development.

Land-Atmosphere Transfer Parameters in the Brazilian Pantanal during the Dry Season

The Brazilian region of Pantanal is one of the largest wetlands in the world, characterized by a wet season, in which it is covered by a shallow water layer, and a dry season, in which the water layer disappears. The aim of this study is the estimation of the main parameters (drag coefficients and surface scale lengths) involved in modelling the surface atmosphere transfer of momentum, heat and water vapor from the dataset of the second Interdisciplinary Pantanal Experiment (IPE2). The roughness parameters and the stability correction parameters have been estimated in the framework of the similarity theory for the vertical profiles of wind speed and temperature. Thus, a previously-developed methodology was adapted to the available dataset from the IPE2 five-level mast. The results are in reasonable agreement with the available literature. An attempt to obtain the scalar transfer parameters for water vapor has been performed by a Penman–Monteith approach using a two-component surface resistance in parallel between a vegetation and a bare soil part. The parameters of the model have been calibrated using a non-linear regression method. The scalar drag coefficient retrieved in this way is in agreement with that calculated by the flux-gradient approach for the sensible heat flux. Eventually, an evaluation of the vegetation contribution to the total vapor flux is given.

Methodical assessment of the differences between the QNSE and MYJ PBL schemes for stable conditions

The increasing number of physics parametrization schemes adopted in numerical weather forecasting models has resulted in a proliferation of intercomparison studies in recent years. Many of these studies concentrated on determining which parametrization yields results closest to observations rather than analyzing the reasons underlying the differences. In this work, we study the performance of two 1.5‐order boundary layer parameterizations, the quasi‐normal scale elimination (QNSE) and Mellor–Yamada–Janjić (MYJ) schemes, in the weather research and forecasting model. Our objectives are to isolate the effect of stability functions on the near‐surface values and vertical profiles of virtual temperature, mixing ratio and wind speed. The results demonstrate that the QNSE stability functions yield better error statistics for 2 m virtual temperature but higher up the errors related to QNSE are slightly larger for virtual temperature and mixing ratio. A surprising finding is the sensitivity of the model results to the choice of the turbulent Prandtl number for neutral stratification (Prt0): in the Monin–Obukhov similarity function for heat, the choice of Prt0 is sometimes more important than the functional form of the similarity function itself. There is a stability‐related dependence to this sensitivity: with increasing near‐surface stability, the relative importance of the functional form increases. In near‐neutral conditions, QNSE exhibits too strong vertical mixing attributed to the applied turbulent kinetic energy subroutine and the stability functions, including the effect of Prt0.

Concept of Spinsonde for Multi-Cycle Measurement of Vertical Wind Profile of Tropical Cyclones

Tropical cyclones and cyclogenesis are active areas of research. Chute-operated dropsondes are capable of acquiring high resolution vertical wind profile of tropical cyclones. This work proposes a chute-free vertical retardation technique (termed as spinsonde) that can accurately measure vertical wind speed profile. Unlike the expendable dropsondes, the spinsonde allows multi-cycle measurement to be performed within a single flight. Proof of principle is demonstrated via simulation and results indicate that the ground speed correlates with the wind speeds to within ±5 km·h-1. This technique reduces flying weight and increases payload capacity by eliminating bulky chutes. Maximum cruising speed (VH) achieved by the spinsonde UAV is 368 km·h-1.

Analysis on Turbulent Flows using Large-eddy Simulation on the Seaside Complex Terrain

The purpose of this study is the Large-eddy Simulation (LES) of the turbulent wind on the complex terrain, and the first results of the simulation are described. The authors tried to apply the LES code, which was developed as an atmospheric simulator in Japan Agency for the Marine-Earth Science and Technology (JAMSTEC), to the wind prediction for the wind energy. On the wind simulation, the highest problem would be the boundary conditions, and the case in this paper was simplified one. The case study in this paper is the west wind on a complex terrain site, which is the wind from sea for the site. The steady flow was employed for the inlet condition, because the wind on the sea is the low turbulent wind, and almost all the turbulence would be generated by the roughness of the ground surface. The wall function was employed as the surface condition on the ground surface. The computational domain size was about 8 × 3 × 2.5 km3, and the minimum cell size was about 10 × 10 × 3 m3. The computational results, the vertical profile of the averaged wind speed and the turbulence intensity, agreed with the measurement by the meteorological masts. Moreover, the authors tried the analysis of the turbulence characteristics. The power spectrum density model, and the cross spectrum analyses gave the knowledge of the turbulent characteristics on the complex terrain and the hints for the domain and grid of the numerical analysis.

Control of Variable Speed Variable Pitch Wind Turbine at Above and Below Rated Wind Speed

The paper presents a nonlinear approach to wind turbine (WT) using two-mass model. The main aim of the controller in the WT is to maximize the energy output at varying wind speed. In this work, a combination of linear and nonlinear controllers is adapted to variable speed variable pitch wind turbines (VSVPWT) system. The major operating regions of the WT are below (region 2) and above rated (region 3) wind speed. In these regions, generator torque control (region 2) and pitch control (region 3) are used. The controllers in WT are tested for below and above rated wind speed for step and vertical wind speed profile. The performances of the controllers are analyzed with nonlinear FAST (Fatigue, Aerodynamics, Structures, and Turbulence) WT dynamic simulation. In this paper, two nonlinear controllers, that is, sliding mode control (SMC) and integral sliding mode control (ISMC), have been applied for region 2, whereas for pitch control in region 3 conventional PI control is used. In ISMC, the sliding manifold makes use of an integral action to show effective qualities of control in terms of the control level reduction and sliding mode switching control minimization.

Unexpected vertical wind speed profiles in the boundary layer over the southern North Sea

Shallow atmospheric internal boundary layers over the southern part of the North Sea are common. Analysis of one year of meteorological data from the FINO1 research platform in the German Bight reveals that vertical wind speed profiles frequently do not conform to the expected modified logarithmic profile of Monin–Obukhov similarity theory. The wind profiles are mostly characterized by local maxima or kinks within the first 100m over the sea surface. The data reveals the most frequent occurrence of a single maximum, but multiple maxima are often present, and there are sometimes even reversed profiles with the wind speed decreasing with height. The expected modified logarithmic profile occurs for a minority of cases. The evidence suggests the frequent presence of internal boundary layers that propagate from coastal land masses that surround the North Sea. A census of vertical wind speed profiles is presented that shows how different inflection states are linked with wind speed and atmospheric stability. The kinks are most prevalent in the upper part of the measurement range near the 100m hub height of modern offshore the wind turbines, so that internal boundary layers represent a possible concern for the offshore wind energy industry in the North Sea region.

Profiles of Wind and Turbulence in the Coastal Atmospheric Boundary Layer of Lake Erie

Prediction of wind resource in coastal zones is difficult due to the complexity of flow in the coastal atmospheric boundary layer (CABL). A three week campaign was conducted over Lake Erie in May 2013 to investigate wind characteristics and improve model parameterizations in the CABL. Vertical profiles of wind speed up to 200 m were measured onshore and offshore by lidar wind profilers, and horizontal gradients of wind speed by a 3-D scanning lidar. Turbulence data were collected from sonic anemometers deployed onshore and offshore. Numerical simulations were conducted with the Weather Research Forecasting (WRF) model with 2 nested domains down to a resolution of 1-km over the lake. Initial data analyses presented in this paper investigate complex flow patterns across the coast. Acceleration was observed up to 200 m above the surface for flow coming from the land to the water. However, by 7 km off the coast the wind field had not yet reached equilibrium with the new surface (water) conditions. The surface turbulence parameters over the water derived from the sonic data could not predict wind profiles observed by the ZephlR lidar located offshore. Horizontal wind speed gradients near the coast show the influence of atmospheric stability on flow dynamics. Wind profiles retrieved from the 3-D scanning lidar show evidence of nocturnal low level jets (LLJs). The WRF model was able to capture the occurrence of LLJ events, but its performance varied in predicting their intensity, duration, and the location of the jet core.

Weibull-k Revisited: “Tall” Profiles and Height Variation of Wind Statistics

The Weibull distribution is commonly used to describe climatological wind-speed distributions in the atmospheric boundary layer. While vertical profiles of mean wind speed in the atmospheric boundary layer have received significant attention, the variation of the shape of the wind distribution with height is less understood. Previously we derived a proba- bilistic model based on similarity theory for calculating the effects of stability and planetary boundary-layer depth upon long-term mean wind profiles. However, some applications (e.g. wind energy estimation) require the Weibull shape parameter (k), as well as mean wind speed. Towards the aim of improving predictions of the Weibull-k profile, we develop expres- sions for the profile of long-term variance of wind speed, including a method extending our probabilistic wind-profile theory; together these two profiles lead to a profile of Weibull- shape parameter. Further, an alternate model for the vertical profile of Weibull shape para- meter is made, improving upon a basis set forth by Wieringa (Boundary-Layer Meteorol, 1989, Vol. 47, 85-110), and connecting with a newly-corrected corollary of the perturbed geostrophic-drag theory of Troen and Petersen (European Wind Atlas, 1989, Riso National Laboratory, Roskilde). Comparing the models for Weibull-k profiles, a new interpretation and explanation is given for the vertical variation of the shape of wind-speed distributions. Results of the modelling are shown for a number of sites, with a discussion of the mod- els' efficacy and applicability. The latter includes a comparative evaluation of Wieringa-type empirical models and perturbed-geostrophic forms with regard to surface-layer behaviour, as well as for heights where climatological wind-speed variability is not dominated by surface effects.

Streamwise Versus Spanwise Spacing of Obstacle Arrays: Parametrization of the Effects on Drag and Turbulence

A Reynolds-averaged Navier–Stokes model is used to investigate the evolution of the sectional drag coefficient and turbulent length scales with the layouts of aligned arrays of cubes. Results show that the sectional drag coefficient is determined by the non-dimensional streamwise distance (sheltering parameter), and the non-dimensional spanwise distance (channelling parameter) between obstacles. This is different than previous approaches that consider only plan area density \((\lambda _\mathrm{p})\). On the other hand, turbulent length scales behave similarly to the staggered case (e. g. they are function of \(\lambda _\mathrm{p}\) only). Analytical formulae are proposed for the length scales and for the sectional drag coefficient as a function of sheltering and channelling parameters, and implemented in a column model. This approach demonstrates good skill in the prediction of vertical profiles of the spatially-averaged horizontal wind speed.

Global distribution and seasonal variability of coastal low-level jets derived from ERA-Interim reanalysis

A low-level wind maximum is often found over the oceans near many coasts around the world. These Coastal Low-Level Jets (CLLJs) play an important role in the coastal weather and have significant impacts on regional climate and ecology as well as on a number of human activities. The presence of CLLJs is related to various local circumstances such as land-sea temperature contrasts, upwelling, coastal terrain, orientation of the coast, and so on, but also to the large-scale atmospheric dynamics. This makes studies of CLLJs not only interesting but also challenging. In this study, based on ERA-Interim reanalysis data, the global distribution, spatio-temporal structure and the seasonal variability of CLLJs are documented. Seasonal data from 1980 to 2011 are used to identify areas where CLLJs are frequently found in the lowest 2 km, following criteria based on the vertical profiles of wind speed and temperature. The results are analysed to highlight the fundamental aspects and distinctive features of the CLLJs across the globe, including their occurrence rate, jet height, maximum wind speed and horizontal extent. Global maps of CLLJs are constructed for the summer and winter seasons. The west coasts of North America, the Iberian Peninsula, north-western Africa and the south-eastern coast of the Arabian Peninsula make up the Northern Hemispheric CLLJ regions, while the west coasts of South America, Australia, and southern Africa comprise the South Hemispheric equivalents. The existence and characteristics of CLLJs along the southern coast of Oman and the western coast of the Iberian Peninsula regions are also discussed, not fully envisaged before in the context of CLLJs. The highest occurrence of CLLJs is found during the summer in both hemispheres, and the coast of Oman has the globally highest CLLJ frequency, with also the highest maximum wind speeds. The most commonly found CLLJ has a maximum wind speed between 9 and 15 m s−1, and occurs at heights between 500 and 700 m a.s.l.

Wind profiles of tropical cyclones as observed by Doppler wind profiler and anemometer

This paper investigates the vertical profiles of horizontal mean wind speed and direction based on the synchronized measurements from a Doppler radar profiler and an anemometer during 16 tropical cyclones at a coastal site in Hong Kong. The speed profiles with both open sea and hilly exposures were found to follow the log-law below a height of 500 m. Above this height, there was an additional wind speed shear in the profile for hilly upwind terrain. The fitting parameters with both the power-law and the log-law varied with wind strength. The direction profiles were also sensitive to local terrain setups and surrounding topographic features. For a uniform open sea terrain, wind direction veered logarithmically with height from the surface level up to the free atmospheric altitude of about 1200 m. The accumulated veering angle within the whole boundary layer was observed to be 30o. Mean wind direction under other terrain conditions also increased logarithmically with height above 500 m with a trend of rougher exposures corresponding to lager veering angles. A number of empirical parameters for engineering applications were presented, including the speed adjustment factors, power exponents of speed profiles, and veering angle, etc. The objective of this study aims to provide useful information on boundary layer wind characteristics for wind-resistant design of high-rise structures in coastal areas.