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Journal articles on the topic 'Wind spectra'

Author: Grafiati

Published: 4 June 2021

Last updated: 12 February 2022

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1

Li, Qiang, Markus Rapp, Gunter Stober, and Ralph Latteck. "High-resolution vertical velocities and their power spectrum observed with the MAARSY radar – Part 1: frequency spectrum." Annales Geophysicae 36, no. 2 (2018): 577–86. http://dx.doi.org/10.5194/angeo-36-577-2018.

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Abstract. The Middle Atmosphere Alomar Radar System (MAARSY) installed at the island of Andøya has been run for continuous probing of atmospheric winds in the upper troposphere and lower stratosphere (UTLS) region. In the current study, we present high-resolution wind measurements during the period between 2010 and 2013 with MAARSY. The spectral analysis applying the Lomb–Scargle periodogram method has been carried out to determine the frequency spectra of vertical wind velocity. From a total of 522 days of observations, the statistics of the spectral slope have been derived and show a depende

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2

Reid, JS. "Observational evidence of the interaction of ocean wind-sea with swell." Marine and Freshwater Research 46, no. 2 (1995): 419. http://dx.doi.org/10.1071/mf9950419.

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More than 10 000 spectra of ocean wave data were acquired from a series of buoys moored in the Southern Ocean off the west coast of Tasmania for a period of seven years. Spectra were grouped according to the wind speed and whether the wind direction was onshore or offshore and the mean spectrum found for each group. The frequencies of the low frequency cut-offs and of the spectral peaks of the resulting mean spectra were found to be independent of the wind speed in contrast to self-similar standard spectra such as JONSWAP. This property is attributed to the presence of a swell background which

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3

Schafer, Robert, Susan K. Avery, Kenneth S. Gage, Paul E. Johnston, and D. A. Carter. "Improving Wind Profiler–Measured Winds Using Coplanar Spectral Averaging." Journal of Atmospheric and Oceanic Technology 21, no. 11 (2004): 1671–78. http://dx.doi.org/10.1175/jtech1672.1.

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Abstract A method is presented that increases the detectability of weak clear-air signals by averaging Doppler spectra from coplanar wind profiler beams. The method, called coplanar spectral averaging (CSA), is applied to both simulated wind profiler spectra and to 1 yr of archived spectra from a UHF profiler at Christmas Island (1 October 1999–30 September 2000). A collocated 50-MHz wind profiler provides a truth for evaluating the CSA technique. In the absence of precipitation, it was found that CSA, when combined with a fuzzy logic quality control, increases the height coverage of the 1-hou

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4

Jiang, Haoyu, and Lin Mu. "Wave Climate from Spectra and Its Connections with Local and Remote Wind Climate." Journal of Physical Oceanography 49, no. 2 (2019): 543–59. http://dx.doi.org/10.1175/jpo-d-18-0149.1.

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AbstractWind-generated waves can propagate over large distances. Therefore, wave spectra from a fixed point can record information about air–sea interactions in distant areas. In this study, the spectral wave climate for a point in the tropical eastern Pacific Ocean is computed. Several well-defined wave climate systems are observed in the mean wave spectrum. Significant seasonal cycling, long-term trends, and correlations with the Southern Oscillation, the Arctic Oscillation, and the Antarctic Oscillation are observed in the local wave spectra, showing abundant climatic information. Projectio

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Zhang, Shao Dong, Chun Ming Huang, Kai Ming Huang, Ye Hui Zhang, Yun Gong, and Quan Gan. "Vertical wavenumber spectra of three-dimensional winds revealed by radiosonde observations at midlatitude." Annales Geophysicae 35, no. 1 (2017): 107–16. http://dx.doi.org/10.5194/angeo-35-107-2017.

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Abstract. By applying 12-year (1998–2009) radiosonde data over a midlatitude station, we studied the vertical wavenumber spectra of three-dimensional wind fluctuations. The horizontal wind spectra in the lower stratosphere coincide well with the well-known universal spectra, with mean spectral slopes of −2.91 ± 0.09 and −2.99 ± 0.09 for the zonal and meridional wind spectra, respectively, while the mean slopes in the troposphere are −2.64 ± 0.07 and −2.70 ± 0.06, respectively, which are systematically less negative than the canonical slope of −3. In both the troposphere and lower stratosphere,

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6

Gille, Sarah T. "Statistical Characterization of Zonal and Meridional Ocean Wind Stress." Journal of Atmospheric and Oceanic Technology 22, no. 9 (2005): 1353–72. http://dx.doi.org/10.1175/jtech1789.1.

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Abstract Four years of ocean vector wind data are used to evaluate statistics of wind stress over the ocean. Raw swath wind stresses derived from the Quick Scatterometer (QuikSCAT) are compared with five different global gridded wind products, including products based on scatterometer observations, meteorological analysis winds from the European Centre for Medium-Range Weather Forecasts, and reanalysis winds from the National Centers for Environmental Prediction. Buoy winds from a limited number of sites in the Pacific Ocean are also considered. Probability density functions (PDFs) computed fo

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7

HARA, TETSU, and STEPHEN E. BELCHER. "Wind forcing in the equilibrium range of wind-wave spectra." Journal of Fluid Mechanics 470 (October 31, 2002): 223–45. http://dx.doi.org/10.1017/s0022112002001945.

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A new analytical model is developed for the equilibrium range of the spectrum of wind-forced ocean surface gravity waves. We first show that the existing model of Phillips (1985) does not satisfy overall momentum conservation at high winds. This constraint is satisfied by applying recent understanding of the wind forcing of waves. Waves exert a drag on the air flow so that they support a fraction of the applied wind stress, which thus leaves a smaller turbulent stress near the surface to force growth of shorter wavelength waves. Formulation of the momentum budget accounting for this sheltering

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8

Hwang, Paul A., Yalin Fan, Francisco J. Ocampo-Torres, and Héctor García-Nava. "Ocean Surface Wave Spectra inside Tropical Cyclones." Journal of Physical Oceanography 47, no. 10 (2017): 2393–417. http://dx.doi.org/10.1175/jpo-d-17-0066.1.

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AbstractDirectional wave spectra acquired in hurricane reconnaissance missions are compared with wind-wave spectral models. The comparison result is quantified with two indices of model–measurement spectral agreement. In the main region of hurricane coverage, the indices vary sinusoidally with the azimuth angle referenced to the hurricane heading while showing a weak dependence on the radial distance from the hurricane center. The measured spectra agree well with three models evaluated in the back and right quarters, and they are underdeveloped in the front and left quarters. The local wind an

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9

Šafránková, J., Z. Němeček, F. Němec, et al. "SOLAR WIND DENSITY SPECTRA AROUND THE ION SPECTRAL BREAK." Astrophysical Journal 803, no. 2 (2015): 107. http://dx.doi.org/10.1088/0004-637x/803/2/107.

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10

Sinha, Swati, Mary Lourde R., T. V. Chandrasekhar Sarma, J. S. Pillai, and Kushal R. Tuckley. "Spectral Feature-Based Classification of Wind Profiler Power Spectra." IEEE Transactions on Geoscience and Remote Sensing 56, no. 4 (2018): 2138–46. http://dx.doi.org/10.1109/tgrs.2017.2775654.

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11

Qiu, Ye, Ying Sun, and Yue Wu. "Characteristics of Wind Loads on Spherical Shells with Large Rise-Span Ratio." Advanced Materials Research 163-167 (December 2010): 4149–55. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.4149.

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Characteristics of wind pressure distributions over the spherical shell with 3/4 rise-span ratio have been investigated based on the data obtained from a wind tunnel experiment. A discussion of the spectral characteristics including shape of wind pressure spectra, reduced frequency corresponding to the peak spectral amplitude, and spectral slope in high frequency range is also made. The results show that the normalized pressure spectra has a broadband peak at a reduced frequency between 0.15 and 0.50, the slope of Sp( f ) in a high frequency range varies from -1.85 to -0.30 and the reduced pea

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12

Kudritzki, Rolf-Peter. "The Wind Momentum – Luminosity Relationship of Blue Supergiants." International Astronomical Union Colloquium 169 (1999): 405–15. http://dx.doi.org/10.1017/s0252921100072304.

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AbstractThe prediction of the Wind Momentum - Luminosity Relationship (WLR) based on the theory of radiation driven winds is verified by quantitative spectroscopy of winds of A-, B- and O-supergiants. The relationship depends on spectral type. New stellar wind calculations are presented reproducing the observed spectral type dependence. The impact of spectral variability on the WLR is investigated by an analysis of some hundred spectra of the luminous A0Ia-supergiant HD92207 obtained within the Heidelberg Spectral Variability Survey and found to be small.Finally, the WLR is discussed as a tool

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13

Yang, Ke, Wen Hai Shi, and Zheng Nong Li. "Whole Process Wind Characteristics Field Measurements of a Strong Wind." Advanced Materials Research 243-249 (May 2011): 5094–100. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.5094.

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This paper presents field measurement results of boundary layer wind characteristics over typical open country during the passages of typhoon Fung-wong passed by Wenzhou in July 2008. The field data such as wind speed and wind direction were measured from two propeller anemometers placed at the height of about 30m. The measured wind data are analyzed to obtain the information on mean wind speed and direction, turbulence intensity, gust factor, turbulence integral length scale and spectra of wind speed fluctuations. The results clearly demonstrate that the turbulence intensity and gust factor o

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14

Mossoux, E., L. Mahy, and G. Rauw. "The long-period massive binary HD 54662 revisited." Astronomy & Astrophysics 615 (July 2018): A19. http://dx.doi.org/10.1051/0004-6361/201732095.

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Context. HD 54662 is an O-type binary star belonging to the CMa OB1 association. Because of its long-period orbit, this system is an interesting target to test the adiabatic wind shock model. Aims. The goal of this study is to improve our knowledge of the orbital and stellar parameters of HD 54662 and to analyze its X-ray emission to test the theoretical scaling of X-ray emission with orbital separation for adiabatic wind shocks. Methods. We applied a spectral disentangling code to a set of optical spectra to determine the radial velocities and the individual spectra of the primary and seconda

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15

Baath, L. B. "Noise spectra from wind turbines." Renewable Energy 57 (September 2013): 512–19. http://dx.doi.org/10.1016/j.renene.2013.02.007.

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16

Banner, Michael L. "Equilibrium Spectra of Wind Waves." Journal of Physical Oceanography 20, no. 7 (1990): 966–84. http://dx.doi.org/10.1175/1520-0485(1990)020<0966:esoww>2.0.co;2.

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17

Massa, Derek, and Raman K. Prinja. "UV Wind Variability in B Supergiants and its Implications for Wind Structures." International Astronomical Union Colloquium 169 (1999): 214–17. http://dx.doi.org/10.1017/s0252921100072018.

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AbstractWe discuss why B supergiant winds are particularly well suited for wind studies, and present or refer to dynamic spectra which suggest the presence of disks, bifurcated winds, shock formation, rotationally modulated winds and the spontaneous generation of wind enhancements. They underscore the strength and richness of wind variability in B supergiants and the challenges these phenomena present to theoretical studies of stellar winds.

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18

Kudritzki, Rolf-Peter. "Line driven winds, ionizing fluxes and UV-spectra of hot stars at extremely low metalIicity." Symposium - International Astronomical Union 212 (2003): 325–33. http://dx.doi.org/10.1017/s0074180900212394.

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Wind models of very massive stars with metallicities in a range from 10–4-1.0 Z⊙ are presented using a new treatment of radiation driven winds with depth dependent radiative force multipliers and a comprehensive list of more than two million of spectral lines in non-LTE. The models yield mass-loss rates, wind velocities, wind momenta and wind energies as a function of metallicity and can be used to discuss the influence of stellar winds on the evolution of very massive stars in the early universe and on the interstellar medium in the early phases of galaxy formation. It is shown that the norma

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19

Hoffmann, Tadziu L., Adalbert W. A. Pauldrach, and Joachim Puls. "Wind models and synthetic UV spectra for O-type stars." Symposium - International Astronomical Union 212 (2003): 206–7. http://dx.doi.org/10.1017/s0074180900212047.

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Spectral analysis of hot stars requires adequate model atmospheres, which take into account the effects of non-LTE and radiation-driven winds properly. Here we present significant improvements of our approach in constructing detailed atmospheric models and synthetic spectra for O-type stars (model code wm-basic; see Pauldrach, Hoffmann & Lennon 2001). The most important ingredients of these models with regard to a realistic description of stationary winds are: (i) a rigorous treatment of line blocking and blanketing; (ii) a consistent determination of the radiative line acceleration; (iii)

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20

Ewans, K. C., E. M. Bitner-Gregersen, and C. Guedes Soares. "Estimation of Wind-Sea and Swell Components in a Bimodal Sea State." Journal of Offshore Mechanics and Arctic Engineering 128, no. 4 (2004): 265–70. http://dx.doi.org/10.1115/1.2166655.

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Methods for separating the spectral components and describing bimodal wave spectra are evaluated with reference to wave spectra from directional wave measurements made at the Maui location off the west coast of New Zealand. Two methods involve partitioning bimodal wave spectra into wind-sea and swell components and then fitting a spectral function to each component, while the third assigns an average spectral shape based on the integrated spectral parameters. The partitioning methods involve separating the wave spectrum into two frequency bands: a low-frequency peak, the swell component, and a

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21

Xu, Yongsheng, Lee-Lueng Fu, and Ross Tulloch. "The Global Characteristics of the Wavenumber Spectrum of Ocean Surface Wind." Journal of Physical Oceanography 41, no. 8 (2011): 1576–82. http://dx.doi.org/10.1175/jpo-d-11-059.1.

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Abstract The wavenumber spectra of wind kinetic energy over the ocean from Quick Scatterometer (QuikSCAT) observations have revealed complex spatial variability in the wavelength range of 1000–3000 km, with spectral slopes varying from −1.6 to −2.9. Here the authors performed a spectral analysis of QuikSCAT winds over the global ocean and found that (i) the spectral slopes become steeper toward the Poles in the Pacific and in the South Atlantic, and the slopes exhibit minimal longitudinal dependence in the South Pacific; (ii) the steepest slopes are in the tropical Indian Ocean and the shallow

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22

Zickgraf, Franz-Josef. "Disk Winds of B[e] Supergiants." International Astronomical Union Colloquium 169 (1999): 40–48. http://dx.doi.org/10.1017/s025292110007175x.

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AbstractThe class of B[e] supegiants is characterized by a two-component stellar wind consisting of a normal hot star wind in the polar zone and a slow and dense disk-like wind in the equatorial region. The properties of the disk wind are discussed using satellite UV spectra of stars seen edge-on, i.e. through the equatorial disk. These observations show that the disk winds are extremely slow, v∞ ≃ 50 ‒ 90 km s−1, i.e. a factor of ~ 10 slower than expected from the spectral types. Optical emission lines provide a further means to study the disk wind. This is discussed for line profiles of forb

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23

Poulain, Pierre-Marie, Riccardo Gerin, Elena Mauri, and Romain Pennel. "Wind Effects on Drogued and Undrogued Drifters in the Eastern Mediterranean." Journal of Atmospheric and Oceanic Technology 26, no. 6 (2009): 1144–56. http://dx.doi.org/10.1175/2008jtecho618.1.

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Abstract The wind effects on drogued and undrogued drifters are assessed using Coastal Ocean Dynamics Experiment (CODE) and Surface Velocity Program (SVP) drifter datasets and ECMWF wind products in the eastern Mediterranean. Complex and real linear regression models are used to estimate the relative slip of undrogued SVP drifters and to extract the wind-driven currents from the drifter velocities. The frequency response of the wind-driven currents is studied using cross-spectral analysis. By comparing the velocities of cotemporal and nearly collocated undrogued and drogued SVP drifters, it ap

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24

Grewing, Michael. "Wind Features and Wind Velocities." Symposium - International Astronomical Union 131 (1989): 241–50. http://dx.doi.org/10.1017/s0074180900138434.

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Fast winds have been detected in the spectra of many nuclei of planetary nebulae (PNNi). The wind velocities range from about 600 km/s to roughly 4000 km/s. While these winds add little to the mass of the nebular shells they may significantly effect their internal kinematics.By studying the emission from the faint outer envelopes of PNe one can infer also the wind properties of the progenitors of the current nuclei. This will in the end allow to test quantitatively current models of the origin of PNe.

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Flores, Brian L., and D. John Hillier. "Using Shell models to investigate clumping in the wind of the O7Iaf + supergiant AzV83." Monthly Notices of the Royal Astronomical Society 504, no. 1 (2021): 311–25. http://dx.doi.org/10.1093/mnras/stab707.

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ABSTRACT Hot massive stars exhibit strong stellar winds that enrich the surrounding interstellar medium and affect the stars’ evolution. However, the winds are inhomogeneous (clumped) and are difficult to model in radiative transfer codes. To produce more realistic spectra, many codes use a volume-filling factor (VFF) approach to incorporate the effects of clumping. While this approach is convenient, it is simplistic. We introduce an alternative approach to incorporate clumping by assuming the wind is composed of dense spherical shells. Using this approach in the radiative transfer code cmfgen

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26

Unal, Christine. "High-Resolution Raindrop Size Distribution Retrieval Based on the Doppler Spectrum in the Case of Slant Profiling Radar." Journal of Atmospheric and Oceanic Technology 32, no. 6 (2015): 1191–208. http://dx.doi.org/10.1175/jtech-d-13-00225.1.

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AbstractDoppler spectra from vertically profiling radars are usually considered to retrieve the raindrop size distribution (DSD). However, to exploit both fall velocity spectrum and polarimetric measurements, Doppler spectra acquired in slant profiling mode should be explored. Rain DSD samples are obtained from simultaneously measured vertical and slant profile Doppler spectra and evaluated. In particular, the effect of the horizontal wind and the averaging time are investigated.The Doppler spectrum provides a way to retrieve the DSD, the radial wind, and a spectral broadening factor by means

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27

Katsoulis, B. D., and H. D. Kambezidis. "Surface winds and horizontal mesoscale wind spectra in Athens, Greece." Il Nuovo Cimento C 9, no. 6 (1986): 1093–109. http://dx.doi.org/10.1007/bf02507427.

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28

Alexandrova, O. "Solar wind vs magnetosheath turbulence and Alfvén vortices." Nonlinear Processes in Geophysics 15, no. 1 (2008): 95–108. http://dx.doi.org/10.5194/npg-15-95-2008.

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Abstract. In this paper we give firstly a broad review of the space plasma turbulence around the ion characteristic space and temporal scales within two natural laboratories, the solar wind and the Earth magnetosheath. In both regions power law spectra of magnetic fluctuations are observed. In both regions these spectra have a break in the vicinity of the ion cyclotron frequency. A distinctive feature of the magnetosheath turbulence is the presence of Alfvén vortices at scales of the spectral break. The Alfvén vortices are multi-scale nonlinear structures. We give a review of the main theoreti

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29

Witschas, Benjamin, Stephan Rahm, Andreas Dörnbrack, Johannes Wagner, and Markus Rapp. "Airborne Wind Lidar Measurements of Vertical and Horizontal Winds for the Investigation of Orographically Induced Gravity Waves." Journal of Atmospheric and Oceanic Technology 34, no. 6 (2017): 1371–86. http://dx.doi.org/10.1175/jtech-d-17-0021.1.

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AbstractAirborne coherent Doppler wind lidar measurements, acquired during the Gravity Wave Life-Cycle (GW-LCYCLE) I field campaign performed from 2 to 14 December 2013 in Kiruna, Sweden, are used to investigate internal gravity waves (GWs) induced by flow across the Scandinavian Mountains. Vertical wind speed is derived from lidar measurements with a mean bias of less than 0.05 m s−1 and a standard deviation of 0.2 m s−1 by correcting horizontal wind projections onto the line-of-sight direction by means of ECMWF wind data. The horizontal wind speed and direction are retrieved from lidar measu

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30

Treumann, Rudolf A., Wolfgang Baumjohann, and Yasuhito Narita. "On the ion-inertial-range density-power spectra in solar wind turbulence." Annales Geophysicae 37, no. 2 (2019): 183–99. http://dx.doi.org/10.5194/angeo-37-183-2019.

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Abstract. A model-independent first-principle first-order investigation of the shape of turbulent density-power spectra in the ion-inertial range of the solar wind at 1 AU is presented. Demagnetised ions in the ion-inertial range of quasi-neutral plasmas respond to Kolmogorov (K) or Iroshnikov–Kraichnan (IK) inertial-range velocity–turbulence power spectra via the spectrum of the velocity–turbulence-related random-mean-square induction–electric field. Maintenance of electrical quasi-neutrality by the ions causes deformations in the power spectral density of the turbulent density fluctuations.

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31

Yu, J., L. Berger, C. Drews, R. Wimmer-Schweingruber, and A. Taut. "Spectral variation of suprathermal protons associated with stream interaction regions: STEREO A/PLASTIC observations." Astronomy & Astrophysics 615 (July 2018): A126. http://dx.doi.org/10.1051/0004-6361/201732444.

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Context. The observation of power-law spectra of suprathermal particles is typically associated with the occurrence of stream interaction regions (SIRs), indicating that these particles are accelerated close to the observer. However, recent observations have identified the existence of sunwards streaming particles at low suprathermal energies following SIRs. In addition, the observational evidence for turnover spectra in the low suprathermal energies has also been presented, suggesting that these particles might be accelerated at remote shocks and travel back to the Sun along the interplanetar

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32

Deepali, Deepali, and Supratik Banerjee. "Scale-dependent anisotropy of electric field fluctuations in solar wind turbulence." Monthly Notices of the Royal Astronomical Society: Letters 504, no. 1 (2021): L1—L6. http://dx.doi.org/10.1093/mnrasl/slab027.

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ABSTRACT We study the variation of average powers and spectral indices of electric field fluctuations with respect to the angle between average flow direction and the mean magnetic field in solar wind turbulence. Cluster spacecraft data from the years 2002 and 2007 are used for the present analysis. We perform a scale-dependent study with respect to the local mean magnetic field using wavelet analysis technique. Prominent anisotropies are found for both the spectral index and power levels of the electric power spectra. Similar to the magnetic field fluctuations, the parallel (or antiparallel)

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33

Di, Xiao, and Kenneth E. Gilbert. "Approximation of theoretical wind turbulence spectra from wind‐speed measurements." Journal of the Acoustical Society of America 100, no. 4 (1996): 2746. http://dx.doi.org/10.1121/1.416874.

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Frisch, A. S., B. B. Stankov, B. E. Martner, and J. C. Kaimal. "Midtroposphere Wind Speed Spectra from Long-Term Wind Profiler Measurements." Journal of Applied Meteorology 30, no. 12 (1991): 1646–51. http://dx.doi.org/10.1175/1520-0450(1991)030<1646:mwssfl>2.0.co;2.

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35

Zhang, Ying, Qiulong Yang, and Kunde Yang. "Prediction uncertainty of wind-generated noise spectra from wind speed." Journal of the Acoustical Society of America 150, no. 1 (2021): 215–24. http://dx.doi.org/10.1121/10.0005517.

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Hill, Grant M., Anthony F. J. Moffat, Nicole St-Louis, and Peter Bartzakos. "Modeling spectra of WR+O colliding wind systems." Symposium - International Astronomical Union 193 (1999): 360–61. http://dx.doi.org/10.1017/s0074180900205731.

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It is crucial to better understand the winds from massive stars. Not only does their mass loss affect their own evolution but it contributes an amount of energy and momentum to the ISM capable of affecting the chemical and dynamical evolution of their environments. Hot star binaries offer an opportunity to learn more. Colliding winds in such systems might be expected to lead to a bow shock which wraps around the star with the weaker wind. As material flows along the shock, it may give rise to extra line emission. Variations in these emission features may allow the characteristics of the shock

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MORI, Nobuhito, Tsubasa YAMAGUCHI, Sota NAKAJO, Tomohiro YASUDA, and Hajime MASE. "Observations of Wind Wave Directional Spectra." Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 68, no. 2 (2012): I_91—I_95. http://dx.doi.org/10.2208/kaigan.68.i_91.

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38

Jiang, Haoyu. "Wave Climate Patterns from Spatial Tracking of Global Long-Term Ocean Wave Spectra." Journal of Climate 33, no. 8 (2020): 3381–93. http://dx.doi.org/10.1175/jcli-d-19-0729.1.

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AbstractLong-term wave spectral statistics can provide a better description of wave climate than integrated wave parameters because several wave climate systems (WCSs) generated by different wind climate systems can coexist at the same location. In this study, global wave climate patterns are presented by spatially tracking point-wise long-term wave spectra (probability density distributions of wave spectral partitions) from a WAVEWATCH III hindcast, providing new insights into global wave climate. Tens of well-defined WCSs, which are generated in different source regions by different wind sys

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Parkinson, Edward J., Christian Knigge, Knox S. Long, et al. "Accretion disc winds in tidal disruption events: ultraviolet spectral lines as orientation indicators." Monthly Notices of the Royal Astronomical Society 494, no. 4 (2020): 4914–29. http://dx.doi.org/10.1093/mnras/staa1060.

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ABSTRACT Some tidal disruption events (TDEs) exhibit blueshifted broad absorption lines (BALs) in their rest-frame ultraviolet (UV) spectra, while others display broad emission lines (BELs). Similar phenomenology is observed in quasars and accreting white dwarfs, where it can be interpreted as an orientation effect associated with line formation in an accretion disc wind. We propose and explore a similar unification scheme for TDEs. We present synthetic UV spectra for disc and wind-hosting TDEs, produced by a state-of-the-art Monte Carlo ionization and radiative transfer code. Our models cover

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Sapar, L., та A. Sapar. "The stellar wind of χ2 Ori and its variability". Symposium - International Astronomical Union 162 (1994): 534–35. http://dx.doi.org/10.1017/s0074180900215817.

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The resonance spectral lines of high-resolution IUE spectra of χ2 Ori (B2I) have been studied with the aim to determine in more detail the physical status of the stellar wind and its variability due to shell outbursts and clumps superimposed on the isotropic stellar wind. Some general features of resonance spectral line profiles have been studied and explained in physical terms using χ2 Ori as a specimen.

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Hisaki, Yukiharu. "Ocean Wave Directional Spectra Estimation from an HF Ocean Radar with a Single Antenna Array: Methodology." Journal of Atmospheric and Oceanic Technology 23, no. 2 (2006): 268–86. http://dx.doi.org/10.1175/jtech1836.1.

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Abstract A method to estimate ocean wave directional spectra using a high-frequency (HF) ocean radar was developed. The governing equations of wave spectra are integral equations of first- and second-order radar cross sections, the wave energy balance equation, and the continuity equation of surface winds. The parameterization of the source function is the same as that in WAM. Furthermore, the method uses the constraints that wave spectral values are smooth in both wave frequency and direction and that the propagation terms are small. The unknowns to be estimated are surface wind vectors at ra

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Schmidt, J. M. "Spatial transport and spectral transfer of solar wind turbulence composed of Alfvén waves and convective structures II: numerical results." Annales Geophysicae 13, no. 5 (1995): 475–93. http://dx.doi.org/10.1007/s00585-995-0475-3.

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Abstract. This work follows the paper titled "Spatial transport and spectral transfer of solar wind turbulence composed of Alfvén waves and convective structures I: The theoretical model", and deals with the detailed physics and numerical solution of a two-component solar wind model, consisting of small-scale Alfvén waves and convected structures. In particular, we present numerical results which qualitatively reflect many of the observed features of the radial and spectral evolution of the turbulent energies, the residual energy, the cross-helicity and Alfvén-ratio in high-speed solar wind st

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Kobayashi, Takahisa, and Ahoro Adachi. "Retrieval of Arbitrarily Shaped Raindrop Size Distributions from Wind Profiler Measurements." Journal of Atmospheric and Oceanic Technology 22, no. 4 (2005): 433–42. http://dx.doi.org/10.1175/jtech1705.1.

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Abstract An efficient iterative retrieval method for arbitrarily shaped raindrop size distributions (ITRAN) is developed for Doppler spectra measured with a wind profiler. A measured Doppler spectrum is a convolution of the precipitation spectrum and the turbulent spectrum. Deconvolution of the Doppler spectra is achieved through repeated convolutions. The developed method assumes no prior shape of drop size distributions and automatically obtains raindrop size distributions; additionally, it can be applied to large data volumes. Furthermore, it is insensitive to initial values. The method was

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Hauschildt, Peter H., S. Starrfield, E. Baron, and F. Allard. "The Hot Winds of Novae." International Astronomical Union Colloquium 152 (1996): 413–17. http://dx.doi.org/10.1017/s0252921100036319.

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We discuss the physical effects that are important for the formation of the late wind spectra of novae. Nova atmospheres are optically thick, rapidly expanding shells with almost flat density profiles, leading to geometrically very extended atmospheres. We show how the properties of nova spectra can be interpreted in terms of this basic model and discuss some important effects that influence the structure and the emitted spectrum of nova atmospheres, e.g., line blanketing, NLTE effects, and the velocity field. Most of the radiation from hot nova winds is emitted in the spectral range of the EU

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Bahr, Christopher J., and William C. Horne. "Subspace-based background subtraction applied to aeroacoustic wind tunnel testing." International Journal of Aeroacoustics 16, no. 4-5 (2017): 299–325. http://dx.doi.org/10.1177/1475472x17718885.

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A subspace-based form of background subtraction is presented and applied to aeroacoustic wind tunnel data. A variant of this method has seen use in other fields such as climatology and medical imaging. The technique is based on an eigenvalue decomposition of the background noise cross-spectral matrix. Simulated results indicate similar performance to conventional background subtraction when the subtracted spectra are weaker than the true contaminating background levels. Superior performance is observed when the subtracted spectra are stronger than the true contaminating background levels, and

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Arad, Ofir, Assaf Lavi, and Uri Keshet. "Maximally hard radio spectra from Fermi acceleration in pulsar-wind nebulae." Monthly Notices of the Royal Astronomical Society 504, no. 4 (2021): 4952–67. http://dx.doi.org/10.1093/mnras/stab1044.

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ABSTRACT The processes leading to the exceptionally hard radio spectra of pulsar-wind nebulae (PWNe) are not yet understood. Radio photon spectral indices among 29 PWNe from the literature show an approximately normal, α = 0.2 ± 0.2 distribution. We present ∼3σ evidence for a distinct sub-population of PWNe, with a hard spectrum α = 0.01 ± 0.06 near the termination shock and significantly softer elsewhere, possibly due to a recent evacuation of the shock surroundings. Such spectra, especially in the hard sub-population, suggest a Fermi process, such as diffusive shock acceleration (DSA), at it

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Toba, Yoshiaki, Kozo Okada, and Ian S. F. Jones. "The Response of Wind-Wave Spectra to Changing Winds. Part I: Increasing Winds." Journal of Physical Oceanography 18, no. 9 (1988): 1231–40. http://dx.doi.org/10.1175/1520-0485(1988)018<1231:trowws>2.0.co;2.

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Guo, Feng, and David Schlipf. "A Spectral Model of Grid Frequency for Assessing the Impact of Inertia Response on Wind Turbine Dynamics." Energies 14, no. 9 (2021): 2492. http://dx.doi.org/10.3390/en14092492.

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The recent developments in renewable energy have led to a higher proportion of converter-connected power generation sources in the grid. Operating a high renewable energy penetration power system and ensuring the frequency stability could be challenging due to the reduced system inertia, which is usually provided by the conventional synchronous generators. Previous studies have shown the potential of wind turbines to provide an inertia response to the grid based on the measured rate of change of the grid frequency. This is achieved by controlling the kinetic energy extraction from the rotating

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Kelberlau, Felix, and Jakob Mann. "Cross-contamination effect on turbulence spectra from Doppler beam swinging wind lidar." Wind Energy Science 5, no. 2 (2020): 519–41. http://dx.doi.org/10.5194/wes-5-519-2020.

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Abstract. Turbulence velocity spectra are of high importance for the estimation of loads on wind turbines and other built structures, as well as for fitting measured turbulence values to turbulence models. Spectra generated from reconstructed wind vectors of Doppler beam swinging (DBS) wind lidars differ from spectra based on one-point measurements. Profiling wind lidars have several characteristics that cause these deviations, namely cross-contamination between the three velocity components, averaging along the lines of sight and the limited sampling frequency. This study focuses on analyzing

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Xiao, Tian Yin. "Power Spectral Density Model of Torsional Dynamic Wind Loads on Tall Buildings." Applied Mechanics and Materials 164 (April 2012): 433–36. http://dx.doi.org/10.4028/www.scientific.net/amm.164.433.

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9 models of tall buildings with different rectangular cross-sections are tested in a wind tunnel. After processing and analyzing the measured data of fluctuating pressure on the models, the effects of models’height, aspect ratio, side ratio on the power spectra of torsional wind loads are studied. New formulas of power spectral density of torsional wind loads are proposed by curve fitting method. The applicability of the formulas has been verified by the results from the wind tunnel test.

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