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This paper presents an analysis of a new method for retrieving the parameters of the atmospheric boundary layer in hurricanes. This method is based on the approximation of the upper parabolic part of the wind speed profile and the retrieval of the lower logarithmic part. Based on the logarithmic part, the friction velocity, near-surface wind speed and the aerodynamic drag coefficient are obtained. The obtained data are used for the verification of the modeling data in the WRF-ARW model. The case of the Irma hurricane is studied. Different configurations of the model are tested, which differ in the use of physical parameterizations. The difference of wind profiles in various sectors of the hurricane is studied. [ABSTRACT FROM AUTHOR]

Wind flow and sediment transport across a northern California beach‐foredune system with two adjacent vegetation types are examined for the same incident wind conditions. The invasive Ammophila arenaria was taller (c. 1 m) with denser coverage than the neighbouring Elymus mollis alliance canopy (c. 0.65 m), which consisted of a variety of interspersed native plants. Wind flow was measured with rotating cup and sonic anemometry, while sediment transport was measured using laser particle counters. Wind speed profiles over the two canopies were significantly different because of differing vegetation height, coverage density, and stem stiffness. In both cases, there was a lower zone of semi‐stagnant air (below about 0.3 m) that transitioned upward to a shear zone comprising the upper part of the canopy and immediately above. The shear zone above the Elymus canopy was relatively thin (confined to 0.3–0.5 m above‐ground) whereas the shear zone in the Ammophila canopy was thicker extending from a height of about 0.5h (h is average plant height) to about 1.5h. Vertical profiles of Reynolds shear stress (RSS) and turbulence kinetic energy (TKE) are consistent with the shear layer structure over these two contrasting vegetation canopies. The degree of topographically‐forced and vegetation‐enhanced flow steering was significant, with Ammophila strongly shifting the highly oblique (55°) incident wind to essentially shore‐perpendicular trajectories. In comparison, the shore‐perpendicular steering effect was not as pronounced for the Elymus canopy. Sediment transport intensity on the beach was continuous, but decreased progressively to the dune toe, and then dropped to essentially zero once the vegetation canopy was encountered (on the stoss slope). Overall, the study illustrates the significant differences in wind flow and turbulence conditions that may occur in contrasting plant canopies on foredunes, suggesting that greater attention needs to be placed on vegetation roughness characteristics in models of foredune morphodynamics and sediment transport potential. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of a new method for retrieving the parameters of the atmospheric boundary layer in hurricanes. This method is based on the approximation of the upper parabolic part of the wind speed profile and the retrieval of the lower logarithmic part. Based on the logarithmic part, the friction velocity, near-surface wind speed and the aerodynamic drag coefficient are obtained. The obtained data are used for the verification of the modeling data in the WRF-ARW model. The case of the Irma hurricane is studied. Different configurations of the model are tested, which differ in the use of physical parameterizations. The difference of wind profiles in various sectors of the hurricane is studied.

We generate explicit height-dependent eddy viscosity coefficients in the Ekman layer from convex wind speed profiles. The solutions we obtain are parameterized in terms of the relative deflection angle between the wind directions at the top and bottom of the flow, as well as the geostrophic wind speed and a velocity scale we interpret as the transfer rate of horizontal momentum in the vertical direction. The solutions may be used to infer the thickness of the Ekman layer for a variety of deflection angles different from the deflection angle of the classic Ekman spiral. [ABSTRACT FROM AUTHOR]

The impacts of five factors (wind speed, crack width, crack distance, crack depth and crack orientation (compared to wind direction)), on evaporation from cracked soil under moist soil conditions were investigated experimentally. Experiments were carried out under laboratory conditions in a wind tunnel with a 1 m × 1 m × 2.5 m test section using large‐scale (50 cm diameter, 25 cm depth) samples of natural soils wetted to a soil water content of 0.2 g g−1. To reduce the number of necessary experiments, a 2k factorial experimental design was used. Crack widths, crack distances, crack depths and crack orientations of 5–20 mm, 40–100 mm, 50–200 mm and 0–90°, respectively, were used. Effects of each factor on evaporation rate, individually and by interaction between multiple factors, were subsequently calculated. Results showed that individual effects of all five factors on evaporation rate were significant at the 95% level. Wind speed had the largest impact on evaporation rate, followed by crack width, crack distance, crack depth and crack orientation in that order. Overall, the four crack properties together explained 47% of the variations in evaporation rate. Highlights: Evaporation from cracked, moist soil under windy conditions was investigated.Crack orientation significantly affects wind conditions close to the surface.Both wind speed and crack properties significantly affected evaporation rate.Crack properties together explained 47% of variations in evaporation rate. [ABSTRACT FROM AUTHOR]

The lowest portion of the atmosphere is vital to lives, infrastructure, and activities. It means air quality, air motion and momentum, solar and wind energy, and weather safety measures. Wind speed observations at three different heights for three Libyan coastal sites; Magron, Musrata and Darnah, were documented and analysed. Wind speed profiles were estimated employing the two common methods: logarithmic wind and power law profiles. The seasonal and annual patterns, and atmospheric stability classifications were obtained. The daily wind shear variation and wind velocity profiles were determined at different atmospheric stability conditions, neutral, stable and unstable. The results confirm that the highest wind shear occurs during stable conditions at night and for longer in winter days, and the lowest during unstable and neutral atmospheric conditions near midday specially in summer days. Non-dimensional wind speed profiles were obtained and their behavior was identified and compared. The available wind energy history was evaluated considering the effect of atmospheric stability conditions on the estimated extracted energy for each site.

More than seven years of remote sensing data with high spatial and temporal resolution were investigated in this study. The 20-min moving averaged wind profiles form the acoustic sounding with Scintec MFAS sodar were derived every 10 min. The profiles covered from 30 to 600 m height with vertical resolution of 10 m. The wind speed probability and the Weibull distribution parameters were calculated by the maximum likelihood method at each level and then the profiles of the Weibull scale and shape parameters were analyzed. Diurnal wind speed at heights above 200 m has shown a well-expressed increase in the averaged values during the night hours, while during the day lower wind speeds were observed. The reversal height was explored from spatially and temporally homogenized diurnal wind speed data with applied quadratic functions for better interpretation of the results. In addition, analyses by type of air masses (land or sea air mass) were performed. One of the outcomes of the study was assessment of the internal boundary layer height, which was estimated to 50–80 m at the location of the sodar. The obtained information forms the basis for climatological insights on the vertical structure of the coastal boundary layer and is unique long-term data set important not only for Bulgaria but for coastal meteorology in general.

In the current analysis, an attempt has been made, for the first time in its kind, to perform a comprehensive evaluation of wind resource through employing various statistical approaches. An extensive analysis of 46 probability methods has suggested the Wakeby outperforming other distribution functions in terms of compatibility among the actual and predicted wind data. Another challenging phase of the research was performed with a motivation to study the vertical wind shear profile based on two extrapolation methods, power and logarithmic laws. The estimated wind speed at the 80 m height was ranged from 5.58 to 12.24 m/s with an annual mean wind speed of 7.72 m/s. Through using the power law, the Gumbel distribution function, and Harris algorithm, the probability analysis for extreme wind events at higher altitudes was also performed, which led to the 50-year extreme wind speed being 44.262 m/s indicating a low risk of potential damages from the wind storms in the studied area. Extensive analysis of the wind resource characteristics such as seasonal wind speed profiles, the intensity and direction of regional wind turbulence, together with graphical distribution of wind resource highlighted a strong potential of using wind for power production in the investigated region. [ABSTRACT FROM AUTHOR]

This study presents a new methodology to solve the wind turbine modelling based on doubly‐fed induction generator (DFIG) technology. The proposed solution allows us to simulate simultaneously a significant number of individuals DFIG submitted to different wind‐speed profiles, minimising the computational time costs and avoiding excessive simplifications in comparison with previous solutions. For this proposal, a third‐order induction generator model has been considered by the authors. The rotor current‐control loops have been modelled through standard PI regulators, discussing in detail rotor voltage expressions and values of the parameters. The global non‐linear equation system has been rearranged in state‐space forms, by means of local linearisations and using two different software‐packages that enable symbolic computation in a collaborative manner. The analytical results have been compared facing a traditional discretised solving methodology to assess the suitability of the proposed solution under different wind‐speed conditions. Indeed, simulated and real‐measured wind profiles have been considered for this purpose. Finally, a comparison of computational time costs for different time steps, including the effect of the number of wind turbines, is also included in this study. [ABSTRACT FROM AUTHOR]

More than seven years of remote sensing data with high spatial and temporal resolution were investigated in this study. The 20-min moving averaged wind profiles form the acoustic sounding with Scintec MFAS sodar were derived every 10 min. The profiles covered from 30 to 600 m height with vertical resolution of 10 m. The wind speed probability and the Weibull distribution parameters were calculated by the maximum likelihood method at each level and then the profiles of the Weibull scale and shape parameters were analyzed. Diurnal wind speed at heights above 200 m has shown a well-expressed increase in the averaged values during the night hours, while during the day lower wind speeds were observed. The reversal height was explored from spatially and temporally homogenized diurnal wind speed data with applied quadratic functions for better interpretation of the results. In addition, analyses by type of air masses (land or sea air mass) were performed. One of the outcomes of the study was assessment of the internal boundary layer height, which was estimated to 50–80 m at the location of the sodar. The obtained information forms the basis for climatological insights on the vertical structure of the coastal boundary layer and is unique long-term data set important not only for Bulgaria but for coastal meteorology in general. [ABSTRACT FROM AUTHOR]