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Wind shear
About: Wind shear is a research topic. Over the lifetime, 8023 publications have been published within this topic receiving 185373 citations.
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01 Jan 2010
TL;DR: In this article, a turbinemounted lidar capability was first achieved in a proof-of-principle experiment in 2003, in which a prototype ZephIR lidar was placed on the nacelle of a Nordex N90 turbine.
Abstract: Introduction Laser anemometry (lidar) is capable of making detailed measurements of the wind field approaching the blades of operational wind turbines. Incorporation of advance wind data into the turbine control system offers the possibility of improved energy yield and load reduction [1]. A turbinemounted lidar capability was first achieved in a proof-ofprinciple experiment in 2003, in which a prototype ZephIR lidar was placed on the nacelle of a Nordex N90 turbine [2].
52 citations
TL;DR: In this paper, the authors investigated the expected performance of short-term wind power prediction systems for offshore sites in the German Bight and at Horns Rev. Despite the special meteorological situation over the North Sea, it is found that the accuracy of wind speed predictions provided by the numerical prediction model of the German weather service is comparable to that of onshore predictions.
Abstract: We investigate the expected performance of short-term wind power prediction systems for offshore sites in the German Bight and at Horns Rev. Despite the special meteorological situation over the North Sea, it is found that the accuracy of wind speed predictions provided by the numerical prediction model of the German weather service is comparable to that of onshore predictions. However, although relative forecast errors look promising, the absolute errors are fairly large, with a root mean square error up to 3 m s−1 for the 48 h forecast. Moreover, vertical wind profiles which are typically needed to calculate the wind speed at hub height are considered at Horns Rev. In all thermal conditions the measured profiles show significant deviations from the expected shapes. The reason for this has to be clarified. Assuming that the deviations are due to the physical processes in the marine boundary layer, we present an alternative approach to derive wind profiles over the ocean which involves the inertial coupling of the Ekman layers of atmosphere and sea via a wave boundary layer with constant shear stress. Profiles calculated by this method are compared with measured profiles, showing rather good agreement. Copyright © 2004 John Wiley & Sons, Ltd.
52 citations
TL;DR: The second Sporadic E Experiment over Kyushu (SEEK-2) was carried out on 3 August 2002, during an active sporadic-E event that also showed quasi-periodic (QP) echoes as discussed by the authors.
Abstract: . The second Sporadic E Experiment over Kyushu (SEEK-2) was carried out on 3 August 2002, during an active sporadic-E event that also showed quasi-periodic (QP) echoes. Two rockets were launched into the event from Kagoshima Space Center in southern Japan 15 min apart. Both carried a suite of instruments, but the second rocket also released a trimethyl aluminum (TMA) trail to measure the neutral winds and turbulence structure. In a number of earlier measurements in similar conditions, large winds and shears that were either unstable or close to instability were observed in the altitude range where the ionization layer occurred. The SEEK-2 wind measurements showed similar vertical structure, but unlike earlier experiments, there was a significant difference between the up-leg and down-leg wind profiles. In addition, wave or billow-like fluctuations were evident in the up-leg portion of the trail, while the lower portion of the down-leg trail was found to have extremely strong turbulence that led to a rapid break-up of the trail. The large east-west gradient in the winds and the strong turbulence have not been observed before. The wind profiles and shears, as well as the qualitative characteristics of the strong turbulence are presented, along with a discussion of the implications of the dynamical features. Keywords. Ionosphere (Mid-latitude ionosphere; Ionospheric irregularities; Electric field and currents)
52 citations
TL;DR: In this paper, the authors used an Ertel potential vorticity framework to test the hypothesis that there is an average tendency for diabatic effects to intensify cyclonic tropopause polar vortices due to enhanced upper-tropospheric radiative cooling.
Abstract: Tropopause polar vortices are coherent circulation features based on the tropopause in polar regions. They are a common feature of the Arctic, with typical radii less than 1500 km and lifetimes that may exceed 1 month. The Arctic is a particularly favorable region for these features due to isolation from the horizontal wind shear associated with the midlatitude jet stream, which may destroy the vortical circulation. Intensification of cyclonic tropopause polar vortices is examined here using an Ertel potential vorticity framework to test the hypothesis that there is an average tendency for diabatic effects to intensify the vortices due to enhanced upper-tropospheric radiative cooling within the vortices. Data for the analysis are derived from numerical simulations of a large sample of observed cyclonic vortices over the Canadian Arctic. Results show that there is on average a net tendency to create potential vorticity in the vortex, and hence intensify cyclones, and that the tendency is radiatively driven. While the effects of latent heating are considerable, they are smaller in magnitude, and all other diabatic processes have a negligible effect on vortex intensity.
52 citations
TL;DR: In this article, an orographic rainband, called the Nagasaki line, was observed extending northeastward from Nagasaki Peninsula in western Kyushu, Japan during a field experiment called X-BAIU-98.
Abstract: On 26 June 1998 during a field experiment called X-BAIU-98, an orographic rainband, called the Nagasaki line in this study, was observed extending northeastward from the Nagasaki Peninsula in western Kyushu, Japan The convective cells in this rainband, which were about 5 km in horizontal scale and 40 min in duration, propagated northeastward at a speed of about 10 m s -1 They were deep in height in a northeastward direction Around the Nagasaki line, a moist convectively unstable atmosphere was observed in the lower layer together with environmental winds that included southerly winds near the surface and southwesterly jet at 3-4 km in height Numerical simulations of the Nagasaki line were conducted using an operational Regional Spectral Model (RSM) of the Japan Meteorological Agency and a Nonhydrostatic Cloud Model (NHM) of the Meteorological Research Institute While the RSM simulated only a weak precipitation area in western Kyushu, the NHM reproduced many characteristics of the observed Nagasaki line Sensitivity experiments for topography, humidity and wind profiles showed that a moist convectively unstable atmosphere, mesoscale convergence, and winds having both a strong southwesterly jet at 3-4 km and a strong vertical wind shear in the lower troposphere are essential for the formation of the Nagasaki line Although small and low, mountains on the Nagasaki Peninsula are capable of forming an organized precipitation band under such environmental fields
52 citations