scispace - formally typeset
Search or ask a question
Topic

Wind shear

About: Wind shear is a research topic. Over the lifetime, 8023 publications have been published within this topic receiving 185373 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the role of the atmospheric wind in determining the height at which volcanic plumes spread in the atmosphere and the relationship between source mass flux and plume height in a wind field is discussed.
Abstract: [1] Estimates of volcanic source mass flux, currently deduced from observations of plume height, are crucial for ash dispersion models for aviation and population hazard. This study addresses the role of the atmospheric wind in determining the height at which volcanic plumes spread in the atmosphere and the relationship between source mass flux and plume height in a wind field. We present a predictive model of volcanic plumes that describes the bending over of the plume trajectory in a crosswind and show that model predictions are in accord with a dataset of historic eruptions if the profile of atmospheric wind shear is described. The wind restricts the rise height of volcanic plumes such that obtaining equivalent rise heights for a plume in a windy environment would require an order of magnitude increase in the source mass flux over a plume in a quiescent environment. Our model calculations are used to calibrate a semi-empirical relationship between the plume height and the source mass flux that explicitly includes the atmospheric wind speed. We demonstrate that the model can account for the variations in plume height observed during the first explosive phase of the 2010 Eyjafjallajokull eruption using independently measured wind speeds and show that changes in the observed plume height are better explained by changing meteorology than abrupt changes in the source mass flux. This study shows that unless the wind is properly accounted for, estimates of the source mass flux during an explosive eruption are likely to be very significant underpredictions of the volcanic source conditions.

159 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the active dry microburst days during the 1982 JAWS (Joint Airport Weather Studies) Project in Colorado and examined the common characteristics of the environments on these days.
Abstract: The active dry microburst days during the 1982 JAWS (Joint Airport Weather Studies) Project in Colorado are examined for common characteristics. The environments on these days are shown to have similar thermodynamic structures in the vertical. In the morning, a shallow radiation inversion is capped by a deep, dry-adiabatic boundary layer. Moisture is present at midlevels. By evening the radiation inversion has been replaced by a superadiabatic layer at the surface. Solar heating of the boundary layer is shown to be important for producing an environment favorable for dry microbursts. A model is proposed that can be used by forecasters to issue a “wind shear watch” to the general public and aviation community. Peak downdraft speeds associated with dry microbursts appear to be a result of negative buoyancy, owing to the evaporation of precipitation during the descent below cloud base. These downward velocities are of the same magnitude as the horizontal wind speeds. Entrainment of subcloud air into...

158 citations

Journal ArticleDOI
01 Feb 1996
TL;DR: Coherent lidar/laser radar systems have been used for the remote measurement of atmospheric wind velocity since 1966 as discussed by the authors and have been applied to detection and tracking of aircraft wake vortices, measurement of airborne wind fields during the space shuttle takeoff and landing, airborne wind shear detection, ground-based airport microburst windshear monitoring, meteorological research, and environmental monitoring.
Abstract: Coherent lidar/laser radar systems have been used for the remote measurement of atmospheric wind velocity since 1966. Both CW and pulsed coherent lidars have been developed and applied to a variety of ground-based and airborne applications. In recent years, most efforts have concentrated on pulsed CO/sub 2/ and solid-state Doppler lidars for the remote measurement of atmospheric wind velocities. Issues associated with the design and application of coherent lidars to atmospheric wind measurement are discussed. Coherent lidar/laser radar systems have been applied to detection and tracking of aircraft wake vortices, measurement of atmospheric wind fields during the space shuttle takeoff and landing, airborne windshear detection, ground-based airport microburst windshear monitoring, meteorological research, and environmental monitoring. Numerous examples of measurement results are presented. An assessment of the status of coherent lidar technology as practical devices for operational and research uses is addressed.

158 citations

Journal ArticleDOI
TL;DR: In this paper, simulations of wind turbine loads for the NREL 5 MW reference wind turbine under diabatic conditions are performed, and the authors 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.
Abstract: Simulations 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.

158 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present evidence showing the likelihood that the influence of the wind waves can also be large over the oceans and propose an alternative expression for flow over growing wind waves, which are in local equilibrium with the wind, given by a form including the wind-wave spectral peak frequency explicity.
Abstract: Distribution of the wind stress over the oceans is usually estimated by using a bulk formula. It contains the squared 10-m wind speed multiplied by the drag coefficient, which has been assumed in many cases to be a weak function of the 10-m wind speed. Over land the important role of thermal stratification has been clearly recognized, but over the sea the influence of wind waves is less well documented. This paper presents evidence showing the likelihood that the influence of the wind waves can also be large. Charnock proposed an expression for the marine atmospheric boundary layer roughness parameter, z0, which depended only on the wind friction velocity, u☆ and the acceleration of gravity, g. Toba and Koga have recently proposed an alternative expression for flow over growing wind waves, which are in local equilibrium with the wind, given by a form including the wind-wave spectral peak frequency explicity. The criterion for local equilibrium of the wave field with the wind is its consistency wi...

158 citations


Network Information
Related Topics (5)
Wind speed
48.3K papers, 830.4K citations
90% related
Sea surface temperature
21.2K papers, 874.7K citations
87% related
Climate model
22.2K papers, 1.1M citations
85% related
Precipitation
32.8K papers, 990.4K citations
84% related
Boundary layer
64.9K papers, 1.4M citations
83% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023155
2022347
2021165
2020157
2019187
2018165