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Academic literature on the topic 'Wind shear'
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Journal articles on the topic "Wind shear"
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Kim, Hyeon-Gi, Byeong-Min Kim, Jin-Han Kim, In-Su Paek, and Neung-Soo Yoo. "Prediction of Wind Shear Exponent in Complex Terrain." Journal of the Korean Solar Energy Society 32, no. 2 (2012): 87–94. http://dx.doi.org/10.7836/kses.2012.32.2.087.
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Goodrich, Robert K., Corrinne S. Morse, Larry B. Cornman, and Stephen A. Cohn. "A Horizontal Wind and Wind Confidence Algorithm for Doppler Wind Profilers." Journal of Atmospheric and Oceanic Technology 19, no. 3 (2002): 257–73. http://dx.doi.org/10.1175/1520-0426-19.3.257.
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Abstract Boundary layer wind profilers are increasingly being used in applications that require high-quality, rapidly updated winds. An example of this type of application is an airport wind hazard warning system. Wind shear can be a hazard to flight operations and is also associated with the production of turbulence. A method for calculating wind and wind shear using a linear wind field assumption is presented. This method, applied to four- or five-beam profilers, allows for the explicit accounting of the measurable shear terms. An error analysis demonstrates why some shears are more readily estimated than others, and the expected magnitudes of the variance for the wind and wind shear estimates are given. A method for computing a quality control index, or confidence, for the calculated wind is also presented. This confidence calculation is based on an assessment of the validity of the assumptions made in the calculations. Confidence values can be used as a quality control metric for the calculated wind and can also be used in generating a confidence-weighted average wind value from the rapid update values. Results are presented that show that errors in the wind estimates are reduced after removing values with low confidence. The wind and confidence methods are implemented in the NCAR Wind and Confidence Algorithm (NWCA), and have been used with the NCAR Improved Moments Algorithm (NIMA) method for calculating moments and associated moment confidence from Doppler spectra. However, NWCA may be used with any moment algorithm that also computes a first moment confidence. For example, a very simple confidence algorithm can be defined in terms of the signal-to-noise ratio.
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Long, Chi, Tao Yu, Jian Zhang, et al. "Sub-Hourly Variations of Wind Shear in the Mesosphere-Lower Thermosphere as Observed by the China Meteor Radar Chain." Remote Sensing 16, no. 7 (2024): 1291. http://dx.doi.org/10.3390/rs16071291.
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Wind shear has important implications for Kelvin–Helmholtz instability (KHI) and gravity waves (GWs) in the mesosphere–lower thermosphere (MLT) region where its momentum transport process is dominated by short-period (<1 h) GWs. However, the sub-hourly variation in wind shear is still not well quantified. This study aims to improve current understanding of vertical wind shear by analyzing multi-year meteor radar measurements at the Mohe (MH, 53.5°N, 122.3°E), Beijing (BJ, 40.3°N, 116.2°E), Wuhan (WH, 30.5°N, 114.6°E), and Fuke (FK, 19.5°N, 109.1°E) stations in China. The wind field is estimated by a new algorithm, e.g., the damped least squares fitting. Taking the wind shear estimated by normal products as a criterion, the shear produced by the new algorithm has more statistical convergence as compared to the traditional algorithm, e.g., the least squares fitting. Therefore, we argue that the 10 min DLSA wind probably produces a more reasonable vertical shear. Both intensive wind shears and GW kinetic energy can be simultaneously captured during the 0600–1600 UTs of May at MH and during the 1300–2400 UTs of March at FK, possibly implying that the up-propagation of GWs could contribute to the production of large wind shears. The sub-hourly variation in wind shears is potentially valuable for understanding the interrelationship between shear (or KHI) and GWs.
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Markowski, Paul, and Yvette Richardson. "On the Classification of Vertical Wind Shear as Directional Shear versus Speed Shear." Weather and Forecasting 21, no. 2 (2006): 242–47. http://dx.doi.org/10.1175/waf897.1.
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Abstract Vertical wind shear is commonly classified as “directional” or “speed” shear. In this note, these classifications are reviewed and their relevance discussed with respect to the dynamics of convective storms. In the absence of surface drag, storm morphology and evolution only depend on the shape and length of a hodograph, on which the storm-relative winds depend; that is, storm characteristics are independent of the translation and rotation of a hodograph. Therefore, traditional definitions of directional and speed shear are most relevant when applied to the storm-relative wind profile.
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SURESH, R. "An account of low level wind shear over Chennai airport - Part II : Turbulence and eddy dissipation." MAUSAM 60, no. 3 (2021): 325–42. http://dx.doi.org/10.54302/mausam.v60i3.1104.
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In-flight reports on Low Level Wind Shear (LLWS) received from aircrafts are used to issue wind shear alerts for all subsequent landing aircrafts as per standing guidelines of International Civil Aviation Organisation (ICAO). In this paper, winds reported by aircrafts at 1000 and 1800 ft. are used to validate the wind estimated from DWR measured radial wind data employing standard algorithms. Turbulence indices and parameters have been computed independently using conventional (RS/RW) upper air data, aircraft measured winds and DWR estimated winds and compared these with wind shear induced turbulence reported by aircrews. Mean power law (wind escalation law) profiles in the boundary layer have been arrived at for unstable and stable atmospheric conditions.
 
 Three dimensional shear (3DS) upto 600 m a.g.l. has been worked out from DWR measured radial velocity data and compared with wind shear computed from RS/RW and aircraft measured winds and DWR estimated winds. It is found that 3DS values of more than 16 * 10-3 s-1 predict well the occurrence of moderate turbulence. Contrary to the general belief that wind shear is a short lived phenomenon which may last for a few minutes only, it has been observed that incidences of LLWS and induced moderate turbulence lasting more than 10 hrs are not at all uncommon over Chennai aircraft.
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Madougou, Saïdou, Frederique Saïd, Bernard Campistron, and Fadel Kebe Cheikh. "Low Level Jet Wind Shear in the Sahel." International Journal of Engineering Research in Africa 11 (October 2013): 1–10. http://dx.doi.org/10.4028/www.scientific.net/jera.11.1.
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In the Sahel, a vertical wind shear appears in the dry and in the wet seasons. In Niamey, Niger, during the dry season, the period of strong shears is clearly linked to the Nocturnal Low Level Jet (LLJ) since it occurs in a narrow time period around 06H00 UTC at 60% of the cases reach shears which require an alert to the pilots (higher than 4 ms-1 per 100 m). The majority of cases occur during the night with a wind shear direction between 90 and 150° per 100 m, which is shown that it is dangerous for aircraft. In Bamako, Mali, high wind shears represent (higher than 4 ms-1 per 100 m) only 16-22% of the cases and can occur at any time of the day. There are, however, 8% of the cases, the whole day long, when the wind shear can reach more than 6 ms-1 per 100 m. Most of the wind shear directions are also between 0 and 90° per 100 m during the night. This is why the Agency for the safety of aircraft navigation in Africa and Madagascar (ASECNA) has put in 2004 at Bamako airport an UHF wind profiler radar for monitoring nocturnal strong Low Level Jet wind shear which occur regularly in this airport.
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Velden, Christopher S., and John Sears. "Computing Deep-Tropospheric Vertical Wind Shear Analyses for Tropical Cyclone Applications: Does the Methodology Matter?" Weather and Forecasting 29, no. 5 (2014): 1169–80. http://dx.doi.org/10.1175/waf-d-13-00147.1.
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Abstract Vertical wind shear is well known in the tropical cyclone (TC) forecasting community as an important environmental influence on storm structure and intensity change. The traditional way to define deep-tropospheric vertical wind shear in most prior research studies, and in operational forecast applications, is to simply use the vector difference of the 200- and 850-hPa wind fields based on global model analyses. However, is this rather basic approach to approximate vertical wind shear adequate for most TC applications? In this study, the traditional approach is compared to a different methodology for generating fields of vertical wind shear as produced by the University of Wisconsin Cooperative Institute for Meteorological Satellite Studies (CIMSS). The CIMSS fields are derived with heavy analysis weight given to available high-density satellite-derived winds. The resultant isobaric analyses are then used to create two mass-weighted layer-mean wind fields, one upper and one lower tropospheric, which are then differenced to produce the deep-tropospheric vertical wind shear field. The principal novelty of this approach is that it does not rely simply on the analyzed winds at two discrete levels, but instead attempts to account for some of the variable vertical wind structure in the calculation. It will be shown how the resultant vertical wind shear fields derived by the two approaches can diverge significantly in certain situations; the results also suggest that in many cases it is superior in depicting the wind structure's impact on TCs than the simple two-level differential that serves as the common contemporary vertical wind shear approximation.
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Han, Ying, and Boualem Khouider. "Convectively Coupled Waves in a Sheared Environment." Journal of the Atmospheric Sciences 67, no. 9 (2010): 2913–42. http://dx.doi.org/10.1175/2010jas3335.1.
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Abstract A linear stability analysis, about a radiative–convective equilibrium in a sheared environment, on an equatorial beta plane, for a simple multicloud model for organized tropical convection is presented here. Both vertical/baroclinic and meridional/barotropic zonal wind shears are considered separately in a parameter regime for which the shear-free multicloud model exhibits synoptic-scale instability of Kelvin and n = 0 eastward inertio-gravity [eastward mixed Rossby–gravity (MRG)] waves only, with moderate growth rates. The maximum growth rates appear to increase significantly with the strength of the background wind shear, and new wave instabilities appear and/or disappear depending on the strength and type of the wind shear. It is found here that both high- and low-level vertical shears have a strong impact on the stability of convectively coupled waves (CCWs), consistent with the fact that the multicloud instability mechanism is controlled by both stratiform heating and low-level moisture and congestus heating. Typically, vertical shears with high-level easterly wind destabilize westward moving waves and stabilize eastward waves, whereas westerly winds aloft and on bottom tend to destabilize eastward moving and stabilize westward moving waves. In the mixed situation of high-level easterlies and low-level westerlies both eastward and westward waves are unstable, while in the case of high-level westerlies and low-level easterlies only eastward waves are unstable. In the presence of a barotropic/meridional shear, synoptic-scale convectively coupled westward MRG and Rossby waves emerge, when the shear strength is large enough, due essentially to pure shear instability of the dry dynamics. The meridional shear has also an important impact on the horizontal structure of the waves. Owing to the meridional shear, the Kelvin wave displays a nonzero meridional velocity that induces a significant contribution toward the horizontal convergence. The two-day waves adopt a crescentlike shape while the westward MRG, and somewhat the Rossby waves, become less trapped in the vicinity of the equator.
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Khalid, Mahmood. "Crosswise Wind Shear Represented as a Ramped Velocity Profile Impacting a Forward-Moving Aircraft." International Journal of Aerospace Engineering 2019 (August 18, 2019): 1–18. http://dx.doi.org/10.1155/2019/7594737.
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Abrupt changes in wind velocities over small distances in a lateral or vertical direction can produce wind shear which is known to have serious effects upon the performance of an aircraft. Brought about by large-scale changes in the atmospheric conditions, it is a three-dimensional flow phenomenon imposing severe velocity gradients on an aircraft from all possible directions. While it would be difficult to model an instantaneous velocity gradient in a lateral plane, a vortical flow impinging from the sides which represents a wind shear in a vertical direction is imposed on a forward-moving aircraft to investigate the effect on the aerodynamic performance. The maximum shear wind speed from the side was fixed at 0.3 times the forward velocity. After due validations under no-wind shear conditions on simpler half-reflection plane models, a BGK airfoil-based full 3D wing and the ONERA M6 3D wing model were selected for preliminary studies. The investigation was concluded using the ARA M100 wing-fuselage model.
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SURESH, R. "On nowcasting wind shear induced turbulence over Chennai air field." MAUSAM 55, no. 1 (2022): 103–18. http://dx.doi.org/10.54302/mausam.v55i1.933.
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With the newly installed Doppler Weather Radar at Cyclone Detection Radar station, Chennai during October 2001, it has been made possible to analyse the meteorological conditions conducive for the wind shear induced turbulence experienced by the pilots in the approach runway at the time of landing and take-off. The radar has been put into operation w.e.f. 21 February, 2002. Wind shears reported during February – October 2002, have been critically analysed in this study. The three dimensional shear (3DS), a combination of radial, azimuthal and elevation shears, gives a first hand information atleast half an hour before the occurrence of shear induced moderate turbulence when its value exceeds 16mps/km. The 3DS of more than 20mps/km is normally associated with turbulence experienced by the pilots. With the availability of sophisticated and vast computing power, it is now possible to delineate the layer at which the shear is active within 3-5 minutes from the receipt of the radar measured volume data by quickly computing elevation / vertical / radial / azimuthal shear etc. However, to arrive at a meaningful conclusion on the threshold values of shears that are conducive for wind shear induced turbulence and to make use of this information to alert the pilots, feed back from the pilots to build a detailed data base is absolutely inevitable. Monitoring of passage of sea breeze front may also be useful to issue wind shear warnings. The time tested Richardson number has also been verified for its ‘outlook predictability’ of the shear induced turbulence around the airport, though it can not pinpoint the exact location and the time at which turbulence is active. It is hoped that with precise, accurate and timely in-flight report about the wind shear experienced by the pilots and based on the experience gained in analyzing such information, it will be possible to issue probable ‘wind shear alert / warning’ in the near future.