WorldWideScience

Sample records for wind-generated gravity waves

  1. Phase spectral composition of wind generated ocean surface waves

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    A study of the composition of the phase spectra of wind generated ocean surface waves is carried out using wave records collected employing a ship borne wave recorder. It is found that the raw phase spectral estimates could be fitted by the Uniform...

  2. Interpretation of nonlinearity in wind generated ocean surface waves

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    This study attempts to resolve a mix-up between a physical process and its mathematical interpretation in the context of wind waves on ocean surface. Wind generated wave systems, are conventionally interpreted as a result of interaction of a number...

  3. Simulation of an Underwater Acoustic Communication Channel Characterized by Wind-Generated Surface Waves and Bubbles

    NARCIS (Netherlands)

    Dol, H.S.; Colin, M.E.G.D.; Ainslie, M.A.; Walree, P.A. van; Janmaat, J.

    2013-01-01

    Abstract—Sea-surface scattering by wind-generated waves and bubbles is regarded to be the main nonplatform related cause of the time variability of shallow acoustic communication channels. Simulations for predicting the quality of acoustic communication links in such channels thus require adequate

  4. Simulation of an Underwater Acoustic Communication Channel Characterized by Wind-Generated Surface Waves and Bubbles

    NARCIS (Netherlands)

    Dol, H.S.; Ainslie, M.A.; Colin, M.E.G.D.; Janmaat, J.

    2012-01-01

    Sea surface scattering by wind-generated waves and bubbles is regarded to be the main nonplatform-related cause of the time variability of shallow acoustic communication channels. Simulations for predicting the quality of acoustic communication links in such channels thus require adequate modelling

  5. An experimental study of the surface elevation probability distribution and statistics of wind-generated waves

    Science.gov (United States)

    Huang, N. E.; Long, S. R.

    1980-01-01

    Laboratory experiments were performed to measure the surface elevation probability density function and associated statistical properties for a wind-generated wave field. The laboratory data along with some limited field data were compared. The statistical properties of the surface elevation were processed for comparison with the results derived from the Longuet-Higgins (1963) theory. It is found that, even for the highly non-Gaussian cases, the distribution function proposed by Longuet-Higgins still gives good approximations.

  6. Surfing surface gravity waves

    Science.gov (United States)

    Pizzo, Nick

    2017-11-01

    A simple criterion for water particles to surf an underlying surface gravity wave is presented. It is found that particles travelling near the phase speed of the wave, in a geometrically confined region on the forward face of the crest, increase in speed. The criterion is derived using the equation of John (Commun. Pure Appl. Maths, vol. 6, 1953, pp. 497-503) for the motion of a zero-stress free surface under the action of gravity. As an example, a breaking water wave is theoretically and numerically examined. Implications for upper-ocean processes, for both shallow- and deep-water waves, are discussed.

  7. GEODYNAMIC WAVES AND GRAVITY

    Directory of Open Access Journals (Sweden)

    A. V. Vikulin

    2014-01-01

    Full Text Available  Gravity phenomena related to the Earth movements in the Solar System and through the Galaxy are reviewed. Such movements are manifested by geological processes on the Earth and correlate with geophysical fields of the Earth. It is concluded that geodynamic processes and the gravity phenomena (including those of cosmic nature are related.  The state of the geomedium composed of blocks is determined by stresses with force moment and by slow rotational waves that are considered as a new type of movements [Vikulin, 2008, 2010]. It is shown that the geomedium has typical rheid properties [Carey, 1954], specifically an ability to flow while being in the solid state [Leonov, 2008]. Within the framework of the rotational model with a symmetric stress tensor, which is developed by the authors [Vikulin, Ivanchin, 1998; Vikulin et al., 2012a, 2013], such movement of the geomedium may explain the energy-saturated state of the geomedium and a possibility of its movements in the form of vortex geological structures [Lee, 1928]. The article discusses the gravity wave detection method based on the concept of interactions between gravity waves and crustal blocks [Braginsky et al., 1985]. It is concluded that gravity waves can be recorded by the proposed technique that detects slow rotational waves. It is shown that geo-gravitational movements can be described by both the concept of potential with account of gravitational energy of bodies [Kondratyev, 2003] and the nonlinear physical acoustics [Gurbatov et al., 2008]. Based on the combined description of geophysical and gravitational wave movements, the authors suggest a hypothesis about the nature of spin, i.e. own moment as a demonstration of the space-time ‘vortex’ properties.  

  8. Laser Source for Atomic Gravity Wave Detector

    Data.gov (United States)

    National Aeronautics and Space Administration — The Atom Interferometry (AI) Technology for Gravity Wave Measurements demonstrates new matter wave Interferometric sensor technology for precise detection and...

  9. Wind Generated Ocean Waves

    DEFF Research Database (Denmark)

    Frigaard, Peter

    2001-01-01

    Book review: I. R. Young, Elsevier Ocean Engineering Series, Vol 2. Elsevier Science, Oxford, UK, 1999, 306 pages, hardbound, ISBN 0-08-043317-0, Dfl. 275,00 (US$ 139.50)......Book review: I. R. Young, Elsevier Ocean Engineering Series, Vol 2. Elsevier Science, Oxford, UK, 1999, 306 pages, hardbound, ISBN 0-08-043317-0, Dfl. 275,00 (US$ 139.50)...

  10. Gravity waves from relativistic binaries

    OpenAIRE

    Levin, Janna; O'Reilly, Rachel; Copeland, E. J.

    1999-01-01

    The stability of binary orbits can significantly shape the gravity wave signal which future Earth-based interferometers hope to detect. The inner most stable circular orbit has been of interest as it marks the transition from the late inspiral to final plunge. We consider purely relativistic orbits beyond the circular assumption. Homoclinic orbits are of particular importance to the question of stability as they lie on the boundary between dynamical stability and instability. We identify thes...

  11. Gravity induced wave function collapse

    Science.gov (United States)

    Gasbarri, G.; Toroš, M.; Donadi, S.; Bassi, A.

    2017-11-01

    Starting from an idea of S. L. Adler [in Quantum Nonlocality and Reality: 50 Years of Bell's Theorem, edited by M. Bell and S. Gao (Cambridge University Press, Cambridge, England 2016)], we develop a novel model of gravity induced spontaneous wave function collapse. The collapse is driven by complex stochastic fluctuations of the spacetime metric. After deriving the fundamental equations, we prove the collapse and amplification mechanism, the two most important features of a consistent collapse model. Under reasonable simplifying assumptions, we constrain the strength ξ of the complex metric fluctuations with available experimental data. We show that ξ ≥10-26 in order for the model to guarantee classicality of macro-objects, and at the same time ξ ≤10-20 in order not to contradict experimental evidence. As a comparison, in the recent discovery of gravitational waves in the frequency range 35 to 250 Hz, the (real) metric fluctuations reach a peak of ξ ˜10-21.

  12. The sources of atmospheric gravity waves

    International Nuclear Information System (INIS)

    Nagpal, O.P.

    1979-01-01

    The gravity wave theory has been very successful in the interpretation of various upper atmospheric phenomena. This article offers a review of the present state of knowledge about the various sources of atmospheric gravity waves, particularly those which give rise to different types of travelling ionospheric disturbance. Some specific case studies are discussed. (author)

  13. An introduction to atmospheric gravity waves

    CERN Document Server

    Nappo, Carmen J

    2012-01-01

    Gravity waves exist in all types of geophysical fluids, such as lakes, oceans, and atmospheres. They play an important role in redistributing energy at disturbances, such as mountains or seamounts and they are routinely studied in meteorology and oceanography, particularly simulation models, atmospheric weather models, turbulence, air pollution, and climate research. An Introduction to Atmospheric Gravity Waves provides readers with a working background of the fundamental physics and mathematics of gravity waves, and introduces a wide variety of applications and numerous recent advances. Nappo provides a concise volume on gravity waves with a lucid discussion of current observational techniques and instrumentation.An accompanying website contains real data, computer codes for data analysis, and linear gravity wave models to further enhance the reader's understanding of the book's material. Companion web site features animations and streaming video Foreword by George Chimonas, a renowned expert on the interac...

  14. Techniques for studying gravity waves and turbulence

    Science.gov (United States)

    Geller, M. A.

    1983-01-01

    Gravity waves and their associated breaking into turbulence are very important in producing the overall picture of middle atmosphere global dynamics and associated transport. It is shown in this research that MST radars represent a most powerful technique for obtaining the needed parameters for gravity-wave-induced drag and diffusion effects as well as measuring wave accelerations and diffusion directly. A mathematical solution to this problem is that of radiative equilibrium with a balanced thermal wind.

  15. On resonant coupling of acoustic waves and gravity waves

    Science.gov (United States)

    Millet, Christophe

    2017-11-01

    Acoustic propagation in the atmosphere is often modeled using modes that are confined within waveguides causing the sound to propagate through multiple paths to the receiver. On the other hand, direct observations in the lower stratosphere show that the gravity wave field is intermittent, and is often dominated by rather well defined large-amplitude wave packets. In the present work, we use normal modes to describe both the gravity wave field and the acoustic field. The gravity wave spectrum is obtained by launching few monochromatic waves whose properties are chosen stochastically to mimic the intermittency. Owing to the disparity of the gravity and acoustic length scales, the interactions between the gravity wave field and each of the acoustic modes can be described using a multiple-scale analysis. The appropriate amplitude evolution equation for the acoustic field involves certain random terms that can be directly related to the gravity wave sources. We will show that the cumulative effect of gravity wave breakings makes the sensitivity of ground-based acoustic signals large, in that small changes in the gravity wave parameterization can create or destroy specific acoustic features.

  16. Dense Gravity Currents with Breaking Internal Waves

    Science.gov (United States)

    Tanimoto, Yukinobu; Hogg, Charlie; Ouellette, Nicholas; Koseff, Jeffrey

    2017-11-01

    Shoaling and breaking internal waves along a pycnocline may lead to mixing and dilution of dense gravity currents, such as cold river inflows into lakes or brine effluent from desalination plants in near-coastal environments. In order to explore the interaction between gravity currents and breaking interfacial waves a series of laboratory experiments was performed in which a sequence of internal waves impinge upon a shelf-slope gravity current. The waves are generated in a two-layer thin-interface ambient water column under a variety of conditions characterizing both the waves and the gravity currents. The mixing of the gravity current is measured through both intrusive (CTD probe) and nonintrusive (Planar-laser inducted fluorescence) techniques. We will present results over a full range of Froude number (characterizing the waves) and Richardson number (characterizing the gravity current) conditions, and will discuss the mechanisms by which the gravity current is mixed into the ambient environment including the role of turbulence in the process. National Science Foundation.

  17. Gravity Wave Modeling and Airglow Applications

    National Research Council Canada - National Science Library

    Fritts, David

    1999-01-01

    This AASERT supplemental grant supported numerical, theoretical, and observational studies of gravity wave and shear instability processes in the atmosphere and their impact on airglow layers near the mesopause...

  18. Tidal and gravity waves study from the airglow measurements at ...

    Indian Academy of Sciences (India)

    The other waves may be the upward propagating gravity waves or waves resulting from the interaction of inter-mode tidal oscillations, interaction of tidal waves with planetary waves and gravity waves. Some times, the second harmonic wave has higher vertical velocity than the corresponding fundamental wave. Application ...

  19. A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

    Science.gov (United States)

    2015-09-30

    Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves Lian Shen St. Anthony Falls Laboratory and Department of Mechanical...on studying surface gravity wave evolution and spectrum in the presence of surface currents caused by strongly nonlinear internal solitary waves...interaction of surface and internal gravity waves in the South China Sea. We will seek answers to the following questions: 1) How does the wind-wave

  20. Considerations and Optimization of Time-Resolved PIV Measurements near Complex Wind-Generated Air-Water Wave Interface

    Science.gov (United States)

    Stegmeir, Matthew; Markfort, Corey

    2017-11-01

    Time Resolved PIV measurements are applied on both sides of air-water interface in order to study the coupling between air and fluid motion. The multi-scale and 3-dimensional nature of the wave structure poses several unique considerations to generate optimal-quality data very near the fluid interface. High resolution and dynamic range in space and time are required to resolve relevant flow scales along a complex and ever-changing interface. Characterizing the two-way coupling across the air-water interface provide unique challenges for optical measurement techniques. Approaches to obtain near-boundary measurement on both sides of interface are discussed, including optimal flow seeding procedures, illumination, data analysis, and interface tracking. Techniques are applied to the IIHR Boundary-Layer Wind-Wave Tunnel and example results presented for both sides of the interface. The facility combines a 30m long recirculating water channel with an open-return boundary layer wind tunnel, allowing for the study of boundary layer turbulence interacting with a wind-driven wave field.

  1. The physics of orographic gravity wave drag

    Directory of Open Access Journals (Sweden)

    Miguel A C Teixeira

    2014-07-01

    Full Text Available The drag and momentum fluxes produced by gravity waves generated in flow over orography are reviewed, focusing on adiabatic conditions without phase transitions or radiation effects, and steady mean incoming flow. The orographic gravity wave drag is first introduced in its simplest possible form, for inviscid, linearized, non-rotating flow with the Boussinesq and hydrostatic approximations, and constant wind and static stability. Subsequently, the contributions made by previous authors (primarily using theory and numerical simulations to elucidate how the drag is affected by additional physical processes are surveyed. These include the effect of orography anisotropy, vertical wind shear, total and partial critical levels, vertical wave reflection and resonance, non-hydrostatic effects and trapped lee waves, rotation and nonlinearity. Frictional and boundary layer effects are also briefly mentioned. A better understanding of all of these aspects is important for guiding the improvement of drag parametrization schemes.

  2. Laser Source for Atomic Gravity Wave Detector Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The Atom Interferometry (AI) Technology for Gravity Wave Measurements demonstrates new matter wave Interferometric sensor technology for precise detection and...

  3. Gravity's kiss the detection of gravitational waves

    CERN Document Server

    Collins, Harry

    2017-01-01

    Scientists have been trying to confirm the existence of gravitational waves for fifty years. Then, in September 2015, came a "very interesting event" (as the cautious subject line in a physicist's email read) that proved to be the first detection of gravitational waves. In Gravity's Kiss, Harry Collins -- who has been watching the science of gravitational wave detection for forty-three of those fifty years and has written three previous books about it -- offers a final, fascinating account, written in real time, of the unfolding of one of the most remarkable scientific discoveries ever made. Predicted by Einstein in his theory of general relativity, gravitational waves carry energy from the collision or explosion of stars. Dying binary stars, for example, rotate faster and faster around each other until they merge, emitting a burst of gravitational waves. It is only with the development of extraordinarily sensitive, highly sophisticated detectors that physicists can now confirm Einstein's prediction. This is...

  4. Toward An Internal Gravity Wave Spectrum In Global Ocean Models

    Science.gov (United States)

    2015-05-14

    Toward an internal gravity wave spectrum in global ocean models Malte Müller1,2, Brian K. Arbic3, James G. Richman4, Jay F. Shriver4, Eric L. Kunze5...fields and tides are beginning to display realistic internal gravity wave spectra, especially as model resolution increases. This paper examines...able to simulate the internal gravity wave spectrum and the extent to which nonlinear internal wave-wave interactions contribute to the simulated

  5. Wind Generators and Market Power

    DEFF Research Database (Denmark)

    Misir, Nihat

    Electricity production from wind generators holds significant importance in European Union’s 20% renewable energy target by 2020. In this paper, I show that ownership of wind generators affects market outcomes by using both a Cournot oligopoly model and a real options model. In the Cournot...... oligopoly model, ownership of the wind generators by owners of fossil-fueled (peakload) generators decreases total peakload production and increases the market price. These effects increase with total wind generation and aggregate wind generator ownership. In the real options model, start up and shut down...

  6. Gravity the quest for gravitational wave

    CERN Document Server

    Binétruy, Pierre

    2018-01-01

    What force do the Big Bang, the expansion of the Universe, dark matter and dark energy, black holes, and gravitational waves all have in common? This book uncovers gravity as a key to understanding these fascinating phenomena that have so captivated public interest in recent years. Readers will discover the latest findings on how this familiar force in our everyday lives powers the most colossal changes in the Universe. Written by the widely recognized French public scientist and leading astrophysicist Pierre Binetruy, the book also explains the recent experimental confirmation of the existence of gravitational waves.

  7. Nonlinear gravity-capillary water waves

    Science.gov (United States)

    Jiang, Lei

    1997-11-01

    Two-dimensional gravity-capillary water waves are analyzed using a fully-nonlinear Cauchy-integral method with spectral accuracy. Standing waves are generated in experiments by vertical oscillation and measured by a non-intrusive optical system along with a wave probe. Nonlinear resonance of standing waves with non-wetting contact line effects are discussed in detail. Amplitude- dependent wave frequency and damping in a glass rectangular tank suggest a new contact-line model. A new type of sideband resonance due to modulated forcing is discovered and explained by weakly-nonlinear analysis. This analytical solution is verified by our numerical simulations and physical experiments. New standing waveforms with dimpled or sharp crests are observed in experiments and computations. These new waveforms have strong symmetry breaking in time as a result of nonlinear harmonic interaction. With increasing wave steepness, steep standing waves experience period- tripling with three distinct forms: sharp crest, dimpled or flat crest, and round crest. Significant breaking occurs in the sharp-crest mode and the dimpled-crest mode. Using a complex-demodulation technique, I find that these breaking waves are related to the same 1:2 internal resonance (harmonic interaction) that causes the new steep waveforms. Novel approaches are used to estimate the (breaking and non-breaking) wave dissipation in steep and breaking standing waves. The breaking events (spray, air entrainment, and plunging) approximately double the wave dissipation. Weak capillarity significantly affects the limiting wave height and the form of standing waves, as demonstrated by both computations and small-scale Faraday-wave experiments. Capillary ripple generation on traveling waves is shown to be significant even at moderate wave steepness. The ubiquitous horizontal asymmetry of traveling waves is shown to be critical to capillary ripple generation. Two new asymmetric modes are identified and are shown to have an

  8. Gravitational Waves in Viable Modified Gravity Theories

    International Nuclear Information System (INIS)

    Geng, C Q

    2012-01-01

    We review our recent work [1] on gravitational waves in viable f(R) models. We concentrate on the exponential gravity and Starobinsky models. We show that in both cases, the mass of the scalar mode is order of 10 −33 eV when it propagates in vacuum. In the presence of matter density, such as galaxy, the scalar mode can be heavy. In particular, it becomes almost infinity so that the scalar mode of gravitational wave for the exponential model disappears like the ACDM, whereas it can be as low as 10 −24 eV in the Starobinsky model, corresponding to the lowest frequency of 10 −9 Hz, which may be detected by the current and future gravitational wave probes in space.

  9. Wind Generators and Market Power

    DEFF Research Database (Denmark)

    Misir, Nihat

    Electricity production from wind generators holds significant importance in European Union’s 20% renewable energy target by 2020. In this paper, I show that ownership of wind generators affects market outcomes by using both a Cournot oligopoly model and a real options model. In the Cournot...... oligopoly model, ownership of the wind generators by owners of fossil-fueled (peakload) generators decreases total peakload production and increases the market price. These effects increase with total wind generation and aggregate wind generator ownership. In the real options model, start up and shut down...... price thresholds are significantly higher when the monopolist at the peakload level owns both types of generators. Furthermore, when producing electricity with the peakload generator, the monopolist can avoid facing prices below marginal cost by owning a certain share of the wind generators....

  10. Gravity Wave Variances and Propagation Derived from AIRS Radiances

    Science.gov (United States)

    2011-04-15

    even if the waves are initially conservative there. The zonal mean values of N2 at January, 2005 are shown in Fig. 1. The input 2-D wave amplitude A is...Sigmond, M., Vin - cent, R., and Watanabe, S.: Recent developments in gravity-wave effects in climate models and the global distribution of gravity

  11. A case study of gravity waves in noctilucent clouds

    Directory of Open Access Journals (Sweden)

    P. Dalin

    2004-06-01

    Full Text Available We present a case study of a noctilucent cloud (NLC display appearing on 10-11 August 2000 over Northern Sweden. Clear wave structures were visible in the clouds and time-lapse photography was used to derive the parameters characterising the gravity waves which could account for the observed NLC modulation. Using two nearby atmospheric radars, the Esrange MST Radar data and Andoya MF radar, we have identified gravity waves propagating upward from the upper stratosphere to NLC altitudes. The wave parameters derived from the radar measurements support the suggestion that gravity waves are responsible for the observed complex wave dynamics in the NLC.

  12. Shear waves in inhomogeneous, compressible fluids in a gravity field.

    Science.gov (United States)

    Godin, Oleg A

    2014-03-01

    While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere.

  13. Gravity Waves Ripple over Marine Stratocumulus Clouds

    Science.gov (United States)

    2004-01-01

    In this natural-color image from the Multi-angle Imaging SpectroRadiometer (MISR), a fingerprint-like gravity wave feature occurs over a deck of marine stratocumulus clouds. Similar to the ripples that occur when a pebble is thrown into a still pond, such 'gravity waves' sometimes appear when the relatively stable and stratified air masses associated with stratocumulus cloud layers are disturbed by a vertical trigger from the underlying terrain, or by a thunderstorm updraft or some other vertical wind shear. The stratocumulus cellular clouds that underlie the wave feature are associated with sinking air that is strongly cooled at the level of the cloud-tops -- such clouds are common over mid-latitude oceans when the air is unperturbed by cyclonic or frontal activity. This image is centered over the Indian Ocean (at about 38.9o South, 80.6o East), and was acquired on October 29, 2003.The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire globe between 82o north and 82o south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 20545. The image covers an area of 245 kilometers x 378 kilometers, and uses data from blocks 121 to 122 within World Reference System-2 path 134.MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  14. New Gravity Wave Treatments for GISS Climate Models

    Science.gov (United States)

    Geller, Marvin A.; Zhou, Tiehan; Ruedy, Reto; Aleinov, Igor; Nazarenko, Larissa; Tausnev, Nikolai L.; Sun, Shan; Kelley, Maxwell; Cheng, Ye

    2011-01-01

    Previous versions of GISS climate models have either used formulations of Rayleigh drag to represent unresolved gravity wave interactions with the model-resolved flow or have included a rather complicated treatment of unresolved gravity waves that, while being climate interactive, involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive. Here, the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic gravity waves and their interaction with the resolved flow. Comparisons of the GISS model winds and temperatures with no gravity wave parameterization; with only orographic gravity wave parameterization; and with both orographic and nonorographic gravity wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations. The authors also show that the specifications of orographic and nonorographic gravity waves must be different in the Northern and Southern Hemispheres. Then results are presented where the nonorographic gravity wave sources are specified to represent sources from convection in the intertropical convergence zone and spontaneous emission from jet imbalances. Finally, a strategy to include these effects in a climate-dependent manner is suggested.

  15. Gravity waves from tachyonic preheating after hybrid inflation

    Energy Technology Data Exchange (ETDEWEB)

    Dufaux, Jean-Francois [Instituto de Fisica Teorica UAM/CSIC, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Felder, Gary [Department of Physics, Clark Science Center, Smith College, Northampton, MA 01063 (United States); Kofman, Lev [CITA, University of Toronto, 60 St. George Street, Toronto, ON M5S 3H8 (Canada); Navros, Olga, E-mail: jeff.dufaux@uam.es, E-mail: gfelder@email.smith.edu, E-mail: kofman@cita.utoronto.ca, E-mail: navros@email.unc.edu [Department of Mathematics, University of North Carolina Chapel Hill, CB3250 Philips Hall, Chapel Hill, NC 27599 (United States)

    2009-03-15

    We study the stochastic background of gravitational waves produced from preheating in hybrid inflation models. We investigate different dynamical regimes of preheating in these models and we compute the resulting gravity wave spectra using analytical estimates and numerical simulations. We discuss the dependence of the gravity wave frequencies and amplitudes on the various potential parameters. We find that large regions of the parameter space leads to gravity waves that may be observable in upcoming interferometric experiments, including Advanced LIGO, but this generally requires very small coupling constants.

  16. Investigating gravity waves evidences in the Venus upper atmosphere

    Science.gov (United States)

    Migliorini, Alessandra; Altieri, Francesca; Shakun, Alexey; Zasova, Ludmila; Piccioni, Giuseppe; Bellucci, Giancarlo; Grassi, Davide

    2014-05-01

    We present a method to investigate gravity waves properties in the upper mesosphere of Venus, through the O2 nightglow observations acquired with the imaging spectrometer VIRTIS on board Venus Express. Gravity waves are important dynamical features that transport energy and momentum. They are related to the buoyancy force, which lifts air particles. Then, the vertical displacement of air particles produces density changes that cause gravity to act as restoring force. Gravity waves can manifest through fluctuations on temperature and density fields, and hence on airglow intensities. We use the O2 nightglow profiles showing double peaked structures to study the influence of gravity waves in shaping the O2 vertical profiles and infer the waves properties. In analogy to the Earth's and Mars cases, we use a well-known theory to model the O2 nightglow emissions affected by gravity waves propagation. Here we propose a statistical discussion of the gravity waves characteristics, namely vertical wavelength and wave amplitude, with respect to local time and latitude. The method is applied to about 30 profiles showing double peaked structures, and acquired with the VIRTIS/Venus Express spectrometer, during the mission period from 2006-07-05 to 2008-08-15.

  17. Energy density of relic gravity waves from inflation

    International Nuclear Information System (INIS)

    Sahni, V.

    1990-01-01

    We evaluate both the spectral energy density and the total energy density for relic gravity waves produced during the transition from an early inflationary phase to a matter-dominated Friedmann-Robertson-Walker-type expansion: a∼t c (c μν =8πG left-angle T μν right-angle. In the case of power-law and quasiexponential inflation we find that the ratio of the energy density of gravity waves to the background matter density increases with time, as gravity waves with longer wavelengths and larger amplitudes enter the horizon at successively later epochs. This could lead to the energy density of gravity waves becoming comparable to the energy density of matter at late times, if inflation commenced at Planckian energies

  18. Gravity waves from quantum stress tensor fluctuations in inflation

    International Nuclear Information System (INIS)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-01-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  19. Gravity waves from quantum stress tensor fluctuations in inflation

    Science.gov (United States)

    Wu, Chun-Hsien; Hsiang, Jen-Tsung; Ford, L. H.; Ng, Kin-Wang

    2011-11-01

    We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a nonscale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation. This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of trans-Planckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were trans-Planckian at the beginning of inflation.

  20. Bounding the Speed of Gravity with Gravitational Wave Observations.

    Science.gov (United States)

    Cornish, Neil; Blas, Diego; Nardini, Germano

    2017-10-20

    The time delay between gravitational wave signals arriving at widely separated detectors can be used to place upper and lower bounds on the speed of gravitational wave propagation. Using a Bayesian approach that combines the first three gravitational wave detections reported by the LIGO Scientific and Virgo Collaborations we constrain the gravitational waves propagation speed c_{gw} to the 90% credible interval 0.55cLIGO detectors will constrain the speed of gravity to within 20% of the speed of light, while just five detections by the LIGO-Virgo-Kagra network will constrain the speed of gravity to within 1% of the speed of light.

  1. Climatology of gravity wave activity during the West African Monsoon

    Science.gov (United States)

    Kafando, P.; Chane-Ming, F.; Petitdidier, M.

    2008-12-01

    Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001-2006) above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E) and Ouagadougou (12.35° N; 1.51° W). Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density calculated with temperature only supports that observed small-scale temperature and wind perturbations are mostly associated with gravity waves in the lower stratosphere especially for large values during the wet season. Above the two sites, monthly evolution of gravity wave total energy density reveals a maximum intensity of gravity wave activity in July during the West African Monsoon period. Indicators of convective activity such as mean Outgoing Longwave Radiation (OLR) and Tropical Rainfall Measuring Mission (TRMM) rain rates reveal to be adequate monsoon proxies to be compared to gravity wave energy intensity during the West African Monsoon.

  2. Climatology of gravity wave activity during the West African Monsoon

    Directory of Open Access Journals (Sweden)

    P. Kafando

    2008-12-01

    Full Text Available Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001–2006 above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E and Ouagadougou (12.35° N; 1.51° W. Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density calculated with temperature only supports that observed small-scale temperature and wind perturbations are mostly associated with gravity waves in the lower stratosphere especially for large values during the wet season. Above the two sites, monthly evolution of gravity wave total energy density reveals a maximum intensity of gravity wave activity in July during the West African Monsoon period. Indicators of convective activity such as mean Outgoing Longwave Radiation (OLR and Tropical Rainfall Measuring Mission (TRMM rain rates reveal to be adequate monsoon proxies to be compared to gravity wave energy intensity during the West African Monsoon.

  3. No further gravitational wave modes in F(T) gravity

    Energy Technology Data Exchange (ETDEWEB)

    Bamba, Kazuharu, E-mail: bamba@kmi.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Capozziello, Salvatore, E-mail: capozziello@na.infn.it [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Dipartimento di Fisica, Università di Napoli “Federico II” (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); De Laurentis, Mariafelicia, E-mail: felicia@na.infn.it [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Dipartimento di Fisica, Università di Napoli “Federico II” (Italy); INFN Sez. di Napoli, Compl. Univ. di Monte S. Angelo, Edificio G, Via Cinthia, I-80126 Napoli (Italy); Nojiri, Shin' ichi, E-mail: nojiri@phys.nagoya-u.ac.jp [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Department of Physics, Nagoya University, Nagoya 464-8602 (Japan); Sáez-Gómez, Diego, E-mail: diego.saezgomez@uct.ac.za [Kobayashi–Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Astrophysics, Cosmology and Gravity Centre (ACGC) and Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701, Cape Town (South Africa); Fisika Teorikoaren eta Zientziaren Historia Saila, Zientzia eta Teknologia Fakultatea, Euskal Herriko Unibertsitatea, 644 Posta Kutxatila, 48080 Bilbao (Spain)

    2013-11-25

    We explore the possibility of further gravitational wave modes in F(T) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F(T) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F(T). This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F(T) gravity.

  4. No further gravitational wave modes in F(T) gravity

    International Nuclear Information System (INIS)

    Bamba, Kazuharu; Capozziello, Salvatore; De Laurentis, Mariafelicia; Nojiri, Shin'ichi; Sáez-Gómez, Diego

    2013-01-01

    We explore the possibility of further gravitational wave modes in F(T) gravity, where T is the torsion scalar in teleparallelism. It is explicitly demonstrated that gravitational wave modes in F(T) gravity are equivalent to those in General Relativity. This result is achieved by calculating the Minkowskian limit for a class of analytic function of F(T). This consequence is also confirmed by the preservative analysis around the flat background in the weak field limit with the scalar–tensor representation of F(T) gravity

  5. Electromagnetic internal gravity waves in the Earth's ionospheric E-layer

    International Nuclear Information System (INIS)

    Kaladze, T.D.; Tsamalashvili, L.V.; Kaladze, D.T.

    2011-01-01

    In the Earth's ionospheric E-layer existence of the new waves connecting with the electromagnetic nature of internal gravity waves is shown. They represent the mixture of the ordinary internal gravity waves and the new type of dispersive Alfven waves. -- Highlights: ► Existence of electromagnetic internal gravity waves in the ionospheric E-layer is shown. ► Electromagnetic nature of internal gravity waves is described. ► Appearance of the new dispersive Alfven waves is shown.

  6. Middle Atmosphere Dynamics with Gravity Wave Interactions in the Numerical Spectral Model: Tides and Planetary Waves

    Science.gov (United States)

    Mayr, Hans G.; Mengel, J. G.; Chan, K. L.; Huang, F. T.

    2010-01-01

    As Lindzen (1981) had shown, small-scale gravity waves (GW) produce the observed reversals of the zonal-mean circulation and temperature variations in the upper mesosphere. The waves also play a major role in modulating and amplifying the diurnal tides (DT) (e.g., Waltersheid, 1981; Fritts and Vincent, 1987; Fritts, 1995a). We summarize here the modeling studies with the mechanistic numerical spectral model (NSM) with Doppler spread parameterization for GW (Hines, 1997a, b), which describes in the middle atmosphere: (a) migrating and non-migrating DT, (b) planetary waves (PW), and (c) global-scale inertio gravity waves. Numerical experiments are discussed that illuminate the influence of GW filtering and nonlinear interactions between DT, PW, and zonal mean variations. Keywords: Theoretical modeling, Middle atmosphere dynamics, Gravity wave interactions, Migrating and non-migrating tides, Planetary waves, Global-scale inertio gravity waves.

  7. VHF radar observations of gravity waves at a low latitude

    Directory of Open Access Journals (Sweden)

    G. Dutta

    1999-08-01

    Full Text Available Wind observations made at Gadanki (13.5°N by using Indian MST Radar for few days in September, October, December 1995 and January, 1996 have been analyzed to study gravity wave activity in the troposphere and lower stratosphere. Horizontal wind variances have been computed for gravity waves of period (2-6 h from the power spectral density (PSD spectrum. Exponential curves of the form eZ/H have been fitted by least squares technique to these variance values to obtain height variations of the irregular winds upto the height of about 15 km, where Z is the height in kilometers. The value of H, the scale height, as determined from curve fitting is found to be less than the theoretical value of scale height of neutral atmosphere in this region, implying that the waves are gaining energy during their passage in the troposphere. In other words, it indicates that the sources of gravity waves are present in the troposphere. The energy densities of gravity wave fluctuations have been computed. Polynomial fits to the observed values show that wave energy density increases in the troposphere, its source region, and then decreases in the lower stratosphere.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; waves and tides

  8. Gravity Wave Detection through All-sky Imaging of Airglow

    Science.gov (United States)

    Nguyen, T. V.; Martinez, A.; Porat, I.; Hampton, D. L.; Bering, E., III; Wood, L.

    2017-12-01

    Airglow, the faint glow of the atmosphere, is caused by the interaction of air molecules with radiation from the sun. Similarly, the aurora is created by interactions of air molecules with the solar wind. It has been shown that airglow emissions are altered by gravity waves passing through airglow source region (100-110km), making it possible to study gravity waves and their sources through airglow imaging. University of Houston's USIP - Airglow team designed a compact, inexpensive all-sky imager capable of detecting airglow and auroral emissions using a fisheye lens, a simple optical train, a filter wheel with 4 specific filters, and a CMOS camera. This instrument has been used in USIP's scientific campaign in Alaska throughout March 2017. During this period, the imager captured auroral activity in the Fairbanks region. Due to lunar conditions and auroral activity images from the campaign did not yield visible signs of airglow. Currently, the team is trying to detect gravity wave patterns present in the images through numerical analysis. Detected gravity wave patterns will be compared to local weather data, and may be used to make correlations between gravity waves and weather events. Such correlations could provide more data on the relationship between the mesosphere and lower layers of the atmosphere. Practical applications of this research include weather prediction and detection of air turbulence.

  9. Deep Orographic Gravity Wave Dynamics over Subantarctic Islands as Observed and Modeled during the Deep Propagating Gravity Wave Experiment (DEEPWAVE)

    Science.gov (United States)

    Eckermann, S. D.; Broutman, D.; Ma, J.; Doyle, J. D.; Pautet, P. D.; Taylor, M. J.; Bossert, K.; Williams, B. P.; Fritts, D. C.; Smith, R. B.; Kuhl, D.; Hoppel, K.; McCormack, J. P.; Ruston, B. C.; Baker, N. L.; Viner, K.; Whitcomb, T.; Hogan, T. F.; Peng, M.

    2016-12-01

    The Deep Propagating Gravity Wave Experiment (DEEPWAVE) was an international aircraft-based field program to observe and study the end-to-end dynamics of atmospheric gravity waves from 0-100 km altitude and the effects on atmospheric circulations. On 14 July 2014, aircraft remote-sensing instruments detected large-amplitude gravity-wave oscillations within mesospheric airglow and sodium layers downstream of the Auckland Islands, located 1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier gravity wave model are used to investigate the dynamics of this event from the surface to the mesosphere. At 0700 UTC when first observations were made, surface flow across the islands' terrain generated linear three-dimensional wavefields that propagated rapidly to ˜78 km altitude, where intense breaking occurred in a narrow layer beneath a zero-wind region at ˜83 km altitude. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these wavefields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis reproduces the salient aspects of observed wavefields, including horizontal wavelengths, phase orientations, temperature and vertical displacement amplitudes, heights and locations of incipient wave breaking, and momentum fluxes. Wave breaking has huge effects on local circulations, with inferred layer-averaged westward mean-flow accelerations of ˜350 m s-1 hour-1 and dynamical heating rates of ˜8 K hour-1, supporting recent speculation of important impacts of orographic gravity waves from subantarctic islands on the mean circulation and climate of the middle atmosphere during austral winter. We also study deep orographic gravity waves from islands during DEEPWAVE more widely using observations from the Atmospheric Infrared Sounder (AIRS) and high-resolution high

  10. Acoustic-Gravity Waves Interacting with a Rectangular Trench

    Directory of Open Access Journals (Sweden)

    Usama Kadri

    2015-01-01

    Full Text Available A mathematical solution of the two-dimensional linear problem of an acoustic-gravity wave interacting with a rectangular trench, in a compressible ocean, is presented. Expressions for the flow field on both sides of the trench are derived. The dynamic bottom pressure produced by the acoustic-gravity waves on both sides of the trench is measurable, though on the transmission side it decreases with the trench depth. A successful recording of the bottom pressures could assist in the early detection of tsunami.

  11. Active Absorption of Irregular Gravity Waves in BEM-Models

    DEFF Research Database (Denmark)

    Brorsen, Michael; Frigaard, Peter

    1992-01-01

    The boundary element method is applied to the computation of irregular gravity waves. The boundary conditions at the open boundaries are obtained by a digital filtering technique, where the surface elevations in front of the open boundary are filtered numerically yielding the velocity to be presc......The boundary element method is applied to the computation of irregular gravity waves. The boundary conditions at the open boundaries are obtained by a digital filtering technique, where the surface elevations in front of the open boundary are filtered numerically yielding the velocity...

  12. Climatology of gravity wave activity during the West African Monsoon

    OpenAIRE

    Kafando, P.; Chane-Ming, Fabrice; Petitdidier, Monique

    2008-01-01

    Gravity wave activity is analysed in the lower stratosphere using 6 year radiosonde data (2001–2006) above two meteorological stations in the West African tropical region such as Niamey (13.47° N; 2.16° E) and Ouagadougou (12.35° N; 1.51° W). Monthly total energy density of gravity waves is computed with temperature and horizontal wind perturbations to highlight the West African Monsoon period from June to September. Comparison with monthly total energy density...

  13. Conjugate ionospheric signatures of tsunami-generated gravity waves

    Science.gov (United States)

    Makela, J. J.; Grawe, M.; Coisson, P.; Lognonne, P. H.

    2015-12-01

    Over the past decade, it has been shown that gravity waves generated by earthquakes and tsunamis can reach the upper atmosphere, where they can have a measureable effect on the ionosphere. Observations made with networks of Global Positioning System (GPS) receivers as well as airglow imaging systems have been used to study the properties of these waves through the signatures they leave in the electron density and airglow layers, respectively. Using the Naval Research Laboratory first-principles model, SAMI3, coupled to a model of the tsunami-generated gravity waves, it has been suggested that in addition to generating perturbations in the ionospheric electron density, the neutral winds associated with the gravity waves should produce perturbations in the electric field. These electric field perturbations would map along the Earth's magnetic field where they would drive disturbances in the ionosphere, generating a signature in the conjugate hemisphere. We present GPS-derived total electron content data from several tsunami events demonstrating that this effect is, indeed, measurable. Being able to observe the effects of tsunami-generated gravity waves in the conjugate hemisphere increases the number of observations that can be used to study this ion-neutral coupling phenomenon.

  14. An axisymmetric inertia-gravity wave generator

    Science.gov (United States)

    Maurer, P.; Ghaemsaidi, S. J.; Joubaud, S.; Peacock, T.; Odier, P.

    2017-10-01

    There has been a rich interplay between laboratory experimental studies of internal waves and advancing understanding of their role in the ocean and atmosphere. In this study, we present and demonstrate the concept for a new form of laboratory internal wave generator that can excite axisymmetric wave fields of arbitrary radial structure. The construction and operation of the generator are detailed, and its capabilities are demonstrated through a pair of experiments using a Bessel function and a bourrelet (i.e., ring-shaped) configuration. The results of the experiments are compared with the predictions of an accompanying analytical model.

  15. Analysis of gravity-waves produced by intense tropical cyclones

    OpenAIRE

    Chane Ming, F.; Chen, Z.; Roux, F.

    2010-01-01

    International audience; Conventional and wavelet methods are combined to characterize gravity-waves (GWs) produced by two intense tropical cyclones (TCs) in the upper troposphere and lower stratosphere (UT/LS) from GPS winsonde data. Analyses reveal large contribution of GWs induced by TCs to wave energy densities in the UT/LS. An increase in total energy density of about 30% of the climatological energy density in austral summer was estimated in the LS above Tromelin during TC Dina. Four dis...

  16. Field verification of ADCP surface gravity wave elevation spectra

    NARCIS (Netherlands)

    Hoitink, A.J.F.; Peters, H.C.; Schroevers, M.

    2007-01-01

    Acoustic Doppler current profilers (ADCPs) can measure orbital velocities induced by surface gravity waves, yet the ADCP estimates of these velocities are subject to a relatively high noise level. The present paper introduces a linear filtration technique to significantly reduce the influence of

  17. Impulsive gravitational waves in general massive 3D gravity

    Science.gov (United States)

    Baykal, Ahmet; Dereli, Tekin

    2017-10-01

    Impulsive, nondiverging, Petrov-Segre type-N gravitational wave solutions to a general massive three-dimensional gravity in the de Sitter, anti-de Sitter, and flat Minkowski backgrounds are constructed in a unified manner by using the exterior algebra of differential forms.

  18. Atmospheric gravity waves due to the Tohoku-Oki tsunami observed in the thermosphere by GOCE

    NARCIS (Netherlands)

    Garcia, R.F.; Doornbos, E.N.; Bruinsma, S.; Hebert, H.

    2014-01-01

    Oceanic tsunami waves couple with atmospheric gravity waves, as previously observed through ionospheric and airglow perturbations. Aerodynamic velocities and density variations are computed from Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) accelerometer and thruster data during

  19. Dynamics of flexural gravity waves: from sea ice to Hawking radiation and analogue gravity

    Science.gov (United States)

    Das, S.; Sahoo, T.; Meylan, M. H.

    2018-01-01

    The propagation of flexural gravity waves, routinely used to model wave interaction with sea ice, is studied, including the effect of compression and current. A number of significant and surprising properties are shown to exist. The occurrence of blocking above a critical value of compression is illustrated. This is analogous to propagation of surface gravity waves in the presence of opposing current and light wave propagation in the curved space-time near a black hole, therefore providing a novel system for studying analogue gravity. Between the blocking and buckling limit of the compressive force, the dispersion relation possesses three positive real roots, contrary to an earlier observation of having a single positive real root. Negative energy waves, in which the phase and group velocity point in opposite directions, are also shown to exist. In the presence of an opposing current and certain critical ranges of compressive force, the second blocking point shifts from the positive to the negative branch of the dispersion relation. Such a shift is known as the Hawking effect from the analogous behaviour in the theory of relativity which leads to Hawking radiation. The theory we develop is illustrated with simulations of linear waves in the time domain.

  20. Testing strong gravity with gravitational waves and Love numbers

    International Nuclear Information System (INIS)

    Franzin, E; Cardoso, V; Raposo, G; Pani, P

    2017-01-01

    The LIGO observation of GW150914 has inaugurated the gravitational-wave astronomy era and the possibility of testing gravity in extreme regimes. While distorted black holes are the most convincing sources of gravitational waves, similar signals might be produced also by other compact objects. In particular, we discuss what the gravitational-wave ringdown could tell us about the nature of the emitting object, and how measurements of the tidal Love numbers could help us in understanding the internal structure of compact dark objects. (paper)

  1. Testing strong gravity with gravitational waves and Love numbers

    Science.gov (United States)

    Franzin, E.; Cardoso, V.; Pani, P.; Raposo, G.

    2017-05-01

    The LIGO observation of GW150914 has inaugurated the gravitational-wave astronomy era and the possibility of testing gravity in extreme regimes. While distorted black holes are the most convincing sources of gravitational waves, similar signals might be produced also by other compact objects. In particular, we discuss what the gravitational-wave ringdown could tell us about the nature of the emitting object, and how measurements of the tidal Love numbers could help us in understanding the internal structure of compact dark objects.

  2. Techniques for studying gravity waves and turbulence: Horizontal, vertical and temporal resolution needed

    Science.gov (United States)

    Avery, S. K.; Carter, D. A.

    1983-01-01

    One of the most important atmospheric measurements that is needed is a measure of the gravity-wave spectrum. The MST radar has been investigated as means to measure the temporal resolution required to determine gravity-wave oscillations. The required vertical and horizontal resolution is dependent on the particular part of the gravity wave spectrum that is analyzed. Horizontal spacing is also discussed.

  3. A coupling modulation model of capillary waves from gravity waves: Theoretical analysis and experimental validation

    Science.gov (United States)

    Chen, Pengzhen; Wang, Xiaoqing; Liu, Li; Chong, Jinsong

    2016-06-01

    According to Bragg theory, capillary waves are the predominant scatterers of high-frequency band (such as Ka-band) microwave radiation from the surface of the ocean. Therefore, understanding the modulation mechanism of capillary waves is an important foundation for interpreting high-frequency microwave remote sensing images of the surface of the sea. In our experiments, we discovered that modulations of capillary waves are significantly larger than the values predicted by the classical theory. Further, analysis shows that the difference in restoring force results in an inflection point while the phase velocity changes from gravity waves region to capillary waves region, and this results in the capillary waves being able to resonate with gravity waves when the phase velocity of the gravity waves is equal to the group velocity of the capillary waves. Consequently, we propose a coupling modulation model in which the current modulates the capillary wave indirectly by modulating the resonant gravity waves, and the modulation of the former is approximated by that of the latter. This model very effectively explains the results discovered in our experiments. Further, based on Bragg scattering theory and this coupling modulation model, we simulate the modulation of normalized radar cross section (NRCS) of typical internal waves and show that the high-frequency bands are superior to the low-frequency bands because of their greater modulation of NRCS and better radiometric resolution. This result provides new support for choice of radar band for observation of wave-current modulation oceanic phenomena such as internal waves, fronts, and shears.

  4. DESIGN ASPECTS OF A RESIDENTIAL WIND GENERATOR

    Directory of Open Access Journals (Sweden)

    C. BRAD

    2017-03-01

    Full Text Available In this paper we present some aspects about the design of a small permanent magnet wind generator with axial magnetic flux often used in residential wind turbine. There are summarised the main steps of the magnetic and electric calculations with applications to a particular case: 0.6 kVA wind generator. The axial flux wind generator design starts with the characteristics of the rare earths permanent magnet existing on the market.

  5. LAICE CubeSat mission for gravity wave studies

    Science.gov (United States)

    Westerhoff, John; Earle, Gregory; Bishop, Rebecca; Swenson, Gary R.; Vadas, Sharon; Clemmons, James; Davidson, Ryan; Fanelli, Lucy; Fish, Chad; Garg, Vidur; Ghosh, Alex; Jagannatha, Bindu B.; Kroeker, Erik; Marquis, Peter; Martin, Daniel; Noel, Stephen; Orr, Cameron; Robertson, Robert

    2015-10-01

    The Lower Atmosphere/Ionosphere Coupling Experiment (LAICE) CubeSat mission will focus on understanding the interaction of atmospheric gravity waves generated by weather systems in the lower atmosphere with the mesosphere, lower thermosphere, and ionosphere (MLTI). Specifically, LAICE will focus on the energy and momentum delivered by these waves and attempt to connect the wave sources and the wave effects in three widely different altitude ranges, substantially adding to our knowledge of critical coupling processes between disparate atmospheric regions. The LAICE mission consists of a 6U CubeSat with a four-instrument payload. The retarding potential analyzer (RPA) will provide in-situ ion density and temperature measurements. A four-channel photometer will measure density and temperature variations in the mesosphere through observations of O2 (0, 0) Atmospheric band and O2 Herzberg I band airglows. There are two pressure sensors that comprise the Space Pressure Suite (SPS): the Space Neutral Pressure Instrument (SNeuPI) and the LAICE Ionization gauge Neutral Atmosphere Sensor (LINAS). Both will provide neutral density measurements, but SNeuPI is a prototype sensor that will be validated by LINAS. This CubeSat mission, scheduled for launch in early 2016 from the International Space Station, provides a cost-effective approach to measuring low altitude in-situ parameters along with simultaneous imaging that is capable of addressing the fundamental questions of atmospheric gravity wave coupling in the MLTI region.

  6. Resonant excitation of coastal Kelvin waves by inertia-gravity waves

    International Nuclear Information System (INIS)

    Reznik, G.M.; Zeitlin, V.

    2009-01-01

    We reveal a mechanism of resonant excitation of non-dispersive coastal Kelvin waves by pairs of incident/reflected inertia-gravity waves in the rotating stratified fluid. In the simplest rotating shallow water model on the semi-infinite plane we show that the mechanism works for a continuum of incoming waves, and thus should be ubiquitous in the ocean. Subsequent slow evolution of thus excited Kelvin waves is governed by harmonically forced simple-wave equation and leads to nontrivial transport and mixing properties

  7. The nonlinear effects on the characteristics of gravity wave packets: dispersion and polarization relations

    Directory of Open Access Journals (Sweden)

    S.-D. Zhang

    2000-10-01

    Full Text Available By analyzing the results of the numerical simulations of nonlinear propagation of three Gaussian gravity-wave packets in isothermal atmosphere individually, the nonlinear effects on the characteristics of gravity waves are studied quantitatively. The analyses show that during the nonlinear propagation of gravity wave packets the mean flows are accelerated and the vertical wavelengths show clear reduction due to nonlinearity. On the other hand, though nonlinear effects exist, the time variations of the frequencies of gravity wave packets are close to those derived from the dispersion relation and the amplitude and phase relations of wave-associated disturbance components are consistent with the predictions of the polarization relation of gravity waves. This indicates that the dispersion and polarization relations based on the linear gravity wave theory can be applied extensively in the nonlinear region.Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides

  8. A Multiscale Nested Modeling Framework to Simulate the Interaction of Surface Gravity Waves with Nonlinear Internal Gravity Waves

    Science.gov (United States)

    2015-09-30

    by internal wave surface currents, a process that can be validated with both in-situ observations and synthetic aperature radar (SAR) imagery which...spectrum? How does this affect the detectability of ISWs in SAR imagery? 5) How does the seasonal variability of ISW currents impact the surface gravity...LZSNFS for 2014/02/01 00Z. It shows an intrusion of Kuroshio southwest off Taiwan as often obsevered during winter season. RESULTS A 1.5 year-long

  9. On the unstable mode merging of gravity-inertial waves with Rossby waves

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2011-08-01

    Full Text Available We recapitulate the results of the combined theory of gravity-inertial-Rossby waves in a rotating, stratified atmosphere. The system is shown to exhibit a "local" (JWKB instability whenever the phase speed of the low-frequency-long wavelength westward propagating Rossby wave exceeds the phase speed ("Kelvin" speed of the high frequency-short wavelength gravity-inertial wave. This condition ensures that mode merging, leading to instability, takes place in some intermediate band of frequencies and wave numbers. The contention that such an instability is "spurious" is not convincing. The energy source of the instability resides in the background enthalpy which can be released by the action of the gravitational buoyancy force, through the combined wave modes.

  10. ANALYTICAL SOLUTION FOR WAVES IN PLANETS WITH ATMOSPHERIC SUPERROTATION. I. ACOUSTIC AND INERTIA-GRAVITY WAVES

    Energy Technology Data Exchange (ETDEWEB)

    Peralta, J.; López-Valverde, M. A. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía, 18008 Granada (Spain); Imamura, T. [Institute of Space and Astronautical Science-Japan Aerospace Exploration Agency 3-1-1, Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Read, P. L. [Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford (United Kingdom); Luz, D. [Centro de Astronomia e Astrofísica da Universidade de Lisboa (CAAUL), Observatório Astronómico de Lisboa, Tapada da Ajuda, 1349-018 Lisboa (Portugal); Piccialli, A., E-mail: peralta@iaa.es [LATMOS, UVSQ, 11 bd dAlembert, 78280 Guyancourt (France)

    2014-07-01

    This paper is the first of a two-part study devoted to developing tools for a systematic classification of the wide variety of atmospheric waves expected on slowly rotating planets with atmospheric superrotation. Starting with the primitive equations for a cyclostrophic regime, we have deduced the analytical solution for the possible waves, simultaneously including the effect of the metric terms for the centrifugal force and the meridional shear of the background wind. In those cases when the conditions for the method of the multiple scales in height are met, these wave solutions are also valid when vertical shear of the background wind is present. A total of six types of waves have been found and their properties were characterized in terms of the corresponding dispersion relations and wave structures. In this first part, only waves that are direct solutions of the generic dispersion relation are studied—acoustic and inertia-gravity waves. Concerning inertia-gravity waves, we found that in the cases of short horizontal wavelengths, null background wind, or propagation in the equatorial region, only pure gravity waves are possible, while for the limit of large horizontal wavelengths and/or null static stability, the waves are inertial. The correspondence between classical atmospheric approximations and wave filtering has been examined too, and we carried out a classification of the mesoscale waves found in the clouds of Venus at different vertical levels of its atmosphere. Finally, the classification of waves in exoplanets is discussed and we provide a list of possible candidates with cyclostrophic regimes.

  11. Formation of ice supersaturation by mesoscale gravity waves

    Directory of Open Access Journals (Sweden)

    P. Spichtinger

    2005-01-01

    Full Text Available We investigate the formation and evolution of an ice-supersaturated region (ISSR that was detected by means of an operational radiosonde sounding launched from the meteorological station of Lindenberg on 21 March 2000, 00:00 UTC. The supersaturated layer was situated below the local tropopause, between 320 and 408 hPa altitude. Our investigation uses satellite imagery from METEOSAT and the Advanced Very High Resolution Radiometer (AVHRR and analyses of the European Centre for Medium-Range Weather Forecasts (ECMWF. Mesoscale simulations reveal that the ISSR was formed by a temporary vertical uplift of upper tropospheric air parcels by 20 to 40 hPa in 1 to 2 h. This resulted in a significant local increase of the specific humidity by the moisture transport from below. The ascent was triggered by the superposition of two internal gravity waves, a mountain wave induced by flow past the Erzgebirge and Riesengebirge south of Lindenberg, and an inertial gravity wave excited by the anti-cyclonically curved jet stream over the Baltic Sea. The wave-induced ISSR was rather thick with a depth of about 2 km. The wave-induced upward motion causing the supersaturation also triggered the formation of a cirrus cloud. METEOSAT imagery shows that the cirrus cloud got optically thick within two hours. During this period another longer lasting thin but extended cirrus existed just beneath the tropopause. The wave-induced ISSR disappeared after about half a day in accordance with the decaying wave activity.

  12. On the Chemical Mixing Induced by Internal Gravity Waves

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, T. M. [School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne (United Kingdom); McElwaine, J. N. [Planetary Science Institute, Tucson, AZ 85721 (United States)

    2017-10-10

    Detailed modeling of stellar evolution requires a better understanding of the (magneto)hydrodynamic processes that mix chemical elements and transport angular momentum. Understanding these processes is crucial if we are to accurately interpret observations of chemical abundance anomalies, surface rotation measurements, and asteroseismic data. Here, we use two-dimensional hydrodynamic simulations of the generation and propagation of internal gravity waves in an intermediate-mass star to measure the chemical mixing induced by these waves. We show that such mixing can generally be treated as a diffusive process. We then show that the local diffusion coefficient does not depend on the local fluid velocity, but rather on the wave amplitude. We then use these findings to provide a simple parameterization for this diffusion, which can be incorporated into stellar evolution codes and tested against observations.

  13. Sediment gravity flows triggered by remotely generated earthquake waves

    Science.gov (United States)

    Johnson, H. Paul; Gomberg, Joan S.; Hautala, Susan L.; Salmi, Marie S.

    2017-06-01

    Recent great earthquakes and tsunamis around the world have heightened awareness of the inevitability of similar events occurring within the Cascadia Subduction Zone of the Pacific Northwest. We analyzed seafloor temperature, pressure, and seismic signals, and video stills of sediment-enveloped instruments recorded during the 2011-2015 Cascadia Initiative experiment, and seafloor morphology. Our results led us to suggest that thick accretionary prism sediments amplified and extended seismic wave durations from the 11 April 2012 Mw8.6 Indian Ocean earthquake, located more than 13,500 km away. These waves triggered a sequence of small slope failures on the Cascadia margin that led to sediment gravity flows culminating in turbidity currents. Previous studies have related the triggering of sediment-laden gravity flows and turbidite deposition to local earthquakes, but this is the first study in which the originating seismic event is extremely distant (> 10,000 km). The possibility of remotely triggered slope failures that generate sediment-laden gravity flows should be considered in inferences of recurrence intervals of past great Cascadia earthquakes from turbidite sequences. Future similar studies may provide new understanding of submarine slope failures and turbidity currents and the hazards they pose to seafloor infrastructure and tsunami generation in regions both with and without local earthquakes.

  14. Atmospheric gravity waves in the Red Sea: a new hotspot

    KAUST Repository

    Magalhaes, J. M.

    2011-02-03

    The region of the Middle East around the Red Sea (between 32° E and 44° E longitude and 12° N and 28° N latitude) is a currently undocumented hotspot for atmospheric gravity waves (AGWs). Satellite imagery shows evidence that this region is prone to relatively high occurrence of AGWs compared to other areas in the world, and reveals the spatial characteristics of these waves. The favorable conditions for wave propagation in this region are illustrated with three typical cases of AGWs propagating in the lower troposphere over the sea. Using weakly nonlinear long wave theory and the observed characteristic wavelengths we obtain phase speeds which are consistent with those observed and typical for AGWs, with the Korteweg-de Vries theory performing slightly better than Benjamin-Davis-Acrivos-Ono theory as far as phase speeds are concerned. ERS-SAR and Envisat-ASAR satellite data analysis between 1993 and 2008 reveals signatures consistent with horizontally propagating large-scale internal waves. These signatures cover the entire Red Sea and are more frequently observed between April and September, although they also occur during the rest of the year. The region\\'s (seasonal) propagation conditions for AGWs, based upon average vertical atmospheric stratification profiles suggest that many of the signatures identified in the satellite images are atmospheric internal waves. © Author(s) 2011.

  15. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Science.gov (United States)

    Stober, G.; Sommer, S.; Rapp, M.; Latteck, R.

    2013-10-01

    The Middle Atmosphere Alomar Radar System (MAARSY) on the island of Andøya in Northern Norway (69.3° N, 16.0° E) observes polar mesospheric summer echoes (PMSE). These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  16. Investigation of gravity waves using horizontally resolved radial velocity measurements

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-10-01

    Full Text Available The Middle Atmosphere Alomar Radar System (MAARSY on the island of Andøya in Northern Norway (69.3° N, 16.0° E observes polar mesospheric summer echoes (PMSE. These echoes are used as tracers of atmospheric dynamics to investigate the horizontal wind variability at high temporal and spatial resolution. MAARSY has the capability of pulse-to-pulse beam steering allowing for systematic scanning experiments to study the horizontal structure of the backscatterers as well as to measure the radial velocities for each beam direction. Here we present a method to retrieve gravity wave parameters from these horizontally resolved radial wind variations by applying velocity azimuth display and volume velocity processing. Based on the observations a detailed comparison of the two wind analysis techniques is carried out in order to determine the zonal and meridional wind as well as to measure first-order inhomogeneities. Further, we demonstrate the possibility to resolve the horizontal wave properties, e.g., horizontal wavelength, phase velocity and propagation direction. The robustness of the estimated gravity wave parameters is tested by a simple atmospheric model.

  17. MJO-Related Intraseasonal Variation in the Stratosphere: Gravity Waves and Zonal Winds

    Science.gov (United States)

    Alexander, M. J.; Grimsdell, A. W.; Stephan, C. C.; Hoffmann, L.

    2018-01-01

    Previous work has shown eastward migrating regions of enhanced temperature variance due to long-vertical wavelength stratospheric gravity waves that are in sync with intraseasonal precipitation and tropopause wind anomalies associated with the Madden-Julian Oscillation (MJO). Here the origin of these intraseasonal gravity wave variations is investigated with a set of idealized gravity wave-resolving model experiments. The experiments specifically test whether tropopause winds act to control gravity wave propagation into the stratosphere by a critical level filtering mechanism or play a role in gravity wave generation through an obstacle source effect. All experiments use identical convective latent heating variability, but the large-scale horizontal wind profile is varied to investigate relationships between stratospheric gravity waves and zonal winds at different levels. Results show that the observed long vertical wavelength gravity waves are primarily sensitive to stratospheric zonal wind variations, while tropopause wind variations have only a very small effect. Thus, neither the critical level filter mechanism nor the obstacle source play much of a role in the observed intraseasonal gravity wave variations. Instead, the results suggest that the stratospheric waves follow the MJO precipitation sources, and tropopause wind anomalies follow the same sources. We further find evidence of intraseasonal wave drag effects on the stratospheric circulation in reanalyzed winds. The results suggest that waves drive intraseasonal stratospheric zonal wind anomalies that descend in altitude with increasing MJO phases 3 through 7. Eastward anomalies descend farther than westward, suggesting that MJO-related stratospheric waves cause larger eastward drag forces.

  18. A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995

    OpenAIRE

    K. Hocke; K. Schlegel

    1996-01-01

    Recent investigations of atmospheric gravity waves (AGW) and travelling ionospheric disturbances (TID) in the Earth's thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS), the results are presented in the first part of the review. ...

  19. Wind Generation Feasibility Study in Bethel, AK

    Energy Technology Data Exchange (ETDEWEB)

    Tom Humphrey, YKHC; Lance Kincaid, EMCOR Energy & Technologies

    2004-07-31

    This report studies the wind resources in the Yukon-Kuskokwim Health Corporation (YKHC) region, located in southwestern Alaska, and the applicability of wind generation technologies to YKHC facilities.

  20. Three-wave interactions in a gravity-capillary range of wind waves

    Science.gov (United States)

    Kosnik, M.; Dulov, V.; Kudryavtsev, V.

    2009-04-01

    The effects of three-wave interactions on forming of short wind waves spectrum are investigated. Wavenumber spectrum in gravity-capillary and capillary range is found as a result of evolution of initial arbitrary spectrum under the influence of assigned sources of kinetic equation. Three-wave interactions are taken into account using exact collision integral without any additional assumptions simplifying a problem. Model validity is proved by reproducing Zaharov & Filonenko (1967) theoretical spectra describing the "energy equipartition" and "inertial interval" cases. Numerical calculations show that the main role of three-wave interactions consists in energy transfer from short gravity waves to waves of smaller lengths. The prominent feature of most of resulting spectra is a dip on curvature spectrum in the vicinity of phase speed minimum. Wind forcing, viscous dissipation and mechanism of generation of parasitic capillaries are considered in a number of calculations using parameterization for corresponding sources by Kudryavtsev, Makin, Chapron, 1999. The necessity of additional nonlinear dissipation terms in kinetic equation for short gravity and capillary waves is revealed. The results of calculation with this realistic parameterization of kinetic equation sources show that, when accounted, nonlinear dissipation and parasitic capillaries terms play much more significant part in capillary range than wave-wave interactions. The latter are important only in phase speed minimum area where the typical dip remains at the same wavenumber in all numerical experiments. This work was supported by the EU under the projects INTAS 05-1000008-8014, INTAS/ESA 06-1000025-9264 and Contract # SST5 CT 2006 031001 (MONRUK) of FP6.

  1. Mesospheric gravity waves observed near equatorial and low–middle latitude stations: wave characteristics and reverse ray tracing results

    Directory of Open Access Journals (Sweden)

    E. Achmad

    2006-12-01

    Full Text Available Gravity wave signatures were extracted from OH airglow observations using all-sky CCD imagers at four different stations: Cachoeira Paulista (CP (22.7° S, 45° W and São João do Cariri (7.4° S, 36.5° W, Brazil; Tanjungsari (TJS (6.9° S, 107.9° E, Indonesia and Shigaraki (34.9° N, 136° E, Japan. The gravity wave parameters are used as an input in a reverse ray tracing model to study the gravity wave vertical propagation trajectory and to estimate the wave source region. Gravity waves observed near the equator showed a shorter period and a larger phase velocity than those waves observed at low-middle latitudes. The waves ray traced down into the troposphere showed the largest horizontal wavelength and phase speed. The ray tracing results also showed that at CP, Cariri and Shigaraki the majority of the ray paths stopped in the mesosphere due to the condition of m2m2m|→∞, which suggests the presence of ducting waves and/or waves generated in-situ. In the troposphere, the possible gravity wave sources are related to meteorological front activities and cloud convections at CP, while at Cariri and TJS tropical cloud convections near the equator are the most probable gravity wave sources. The tropospheric jet stream and the orography are thought to be the major responsible sources for the waves observed at Shigaraki.

  2. Atmosphere-ionosphere coupling from convectively generated gravity waves

    Science.gov (United States)

    Azeem, Irfan; Barlage, Michael

    2018-04-01

    Ionospheric variability impacts operational performances of a variety of technological systems, such as HF communication, Global Positioning System (GPS) navigation, and radar surveillance. The ionosphere is not only perturbed by geomagnetic inputs but is also influenced by atmospheric tides and other wave disturbances propagating from the troposphere to high altitudes. Atmospheric Gravity Waves (AGWs) excited by meteorological sources are one of the largest sources of mesoscale variability in the ionosphere. In this paper, Total Electron Content (TEC) data from networks of GPS receivers in the United States are analyzed to investigate AGWs in the ionosphere generated by convective thunderstorms. Two case studies of convectively generated gravity waves are presented. On April 4, 2014 two distinct large convective systems in Texas and Arkansas generated two sets of concentric AGWs that were observed in the ionosphere as Traveling Ionospheric Disturbances (TIDs). The period of the observed TIDs was 20.8 min, the horizontal wavelength was 182.4 km, and the horizontal phase speed was 146.4 m/s. The second case study shows TIDs generated from an extended squall line on December 23, 2015 stretching from the Gulf of Mexico to the Great Lakes in North America. Unlike the concentric wave features seen in the first case study, the extended squall line generated TIDs, which exhibited almost plane-parallel phase fronts. The TID period was 20.1 min, its horizontal wavelength was 209.6 km, and the horizontal phase speed was 180.1 m/s. The AGWs generated by both of these meteorological events have large vertical wavelength (>100 km), which are larger than the F2 layer thickness, thus allowing them to be discernible in the TEC dataset.

  3. Internal gravity wave contributions to global sea surface variability

    Science.gov (United States)

    Savage, A.; Arbic, B. K.; Richman, J. G.; Shriver, J. F.; Buijsman, M. C.; Zamudio, L.; Wallcraft, A. J.; Sharma, H.

    2016-02-01

    High-resolution (1/12th and 1/25th degree) 41-layer simulations of the HYbrid Coordinate Ocean Model (HYCOM), forced by both atmospheric fields and the astronomical tidal potential, are used to construct global maps of sea-surface height (SSH). The HYCOM output has been separated into steric, non-steric, and total sea-surface height and the maps display variance in subtidal, tidal, and supertidal bands. Two of the global maps are of particular interest in planning for the upcoming Surface Water and Ocean Topography (SWOT) wide-swath satellite altimeter mission; (1) a map of the nonstationary tidal signal (estimated after removing the stationary tidal signal via harmonic analysis), and (2) a map of the steric supertidal contributions, which are dominated by the internal gravity wave continuum. Both of these maps display signals of order 1 cm2, the target accuracy for the SWOT mission. Therefore, both non-stationary internal tides and non-tidal internal gravity waves are likely to be important sources of "noise" that must be accurately removed before examination of lower-frequency phenomena can take place.

  4. Characteristics of equatorial gravity waves derived from mesospheric airglow imaging observations

    Directory of Open Access Journals (Sweden)

    S. Suzuki

    2009-04-01

    Full Text Available We present the characteristics of small-scale (<100 km gravity waves in the equatorial mesopause region derived from OH airglow imaging observations at Kototabang (100.3° E, 0.2° S, Indonesia, from 2002 to 2005. We adopted a method that could automatically detect gravity waves in the airglow images using two-dimensional cross power spectra of gravity waves. The propagation directions of the waves were likely controlled by zonal filtering due to stratospheric mean winds that show a quasi-biennial oscillation (QBO and the presence of many wave sources in the troposphere.

  5. On the nonlinear shaping mechanism for gravity wave spectrum in the atmosphere

    Directory of Open Access Journals (Sweden)

    I. P. Chunchuzov

    2009-11-01

    Full Text Available The nonlinear mechanism of shaping of a high vertical wave number spectral tail in the field of a few discrete internal gravity waves in the atmosphere is studied in this paper. The effects of advection of fluid parcels by interacting gravity waves are taken strictly into account by calculating wave field in Lagrangian variables, and performing a variable transformation from Lagrangian to Eulerian frame. The vertical profiles and vertical wave number spectra of the Eulerian displacement field are obtained for both the case of resonant and non-resonant wave-wave interactions. The evolution of these spectra with growing parameter of nonlinearity of the internal wave field is studied and compared to that of a broad band spectrum of gravity waves with randomly independent amplitudes and phases. The calculated vertical wave number spectra of the vertical displacements or relative temperature fluctuations are found to be consistent with the observed spectra in the middle atmosphere.

  6. (abstract) Tropospheric Calibration for the Mars Observer Gravity Wave Experiment

    Science.gov (United States)

    Walter, Steven J.; Armstrong, John

    1994-01-01

    In spring 1993, microwave radiometer-based tropospheric calibration was provided for the Mars Observer gravitational wave search. The Doppler shifted X-band radio signals propagating between Earth and the Mars Observer satellite were precisely measured to determine path length variations that might signal passage of gravitational waves. Experimental sensitivity was restricted by competing sources of variability in signal transit time. Principally, fluctuations in the solar wind and ionospheric plasma density combined with fluctions in tropospheric refractivity determined the detection limit. Troposphere-induced path delay fluctions are dominated by refractive changes caused by water vapor inhomogeneities blowing through the signal path. Since passive microwave remote sensing techniques are able to determine atmospheric propagation delays, radiometer-based tropospheric calibration was provided at the Deep Space Network Uranus tracking site (DSS-15). Two microwave water vapor radiometers (WVRs), a microwave temperature profiler (MTP), and a ground based meterological station were deployed to determine line-of-sight vapor content and vertical temperature profile concurrently with Mars Observer tracking measurements. This calibration system provided the capability to correct Mars Observer Doppler data for troposphere-induced path variations. We present preliminary analysis of the Doppler and WVR data sets illustrating the utility of WVRs to calibrate Doppler data. This takes an important step toward realizing the ambitious system required to support future Ka-band Cassini satellite gravity wave tropospheric calibration system.

  7. Analysis of gravity-waves produced by intense tropical cyclones

    Directory of Open Access Journals (Sweden)

    F. Chane Ming

    2010-02-01

    Full Text Available Conventional and wavelet methods are combined to characterize gravity-waves (GWs produced by two intense tropical cyclones (TCs in the upper troposphere and lower stratosphere (UT/LS from GPS winsonde data. Analyses reveal large contribution of GWs induced by TCs to wave energy densities in the UT/LS. An increase in total energy density of about 30% of the climatological energy density in austral summer was estimated in the LS above Tromelin during TC Dina. Four distinct periods in GW activity in relation with TC Faxai stages is observed in the UT. Globally, GWs have periods of 6 h–2.5 days, vertical wavelenghts of 1–3 km and horizontal wavelengths <1000 km in the UT during the evolution of TCs. Horizontal wavelengths are longer in the LS and about 2200 km during TCs. Convective activity over the basin and GW energy density were modulated by mixed equatorial waves of 3–4 days, 6–8 days and 10–13 days confirmed by Hövmöller diagram, Fourier and wavelet analyses of OLR data. Moreover, location of GW sources is below the tropopause height when TCs are intense otherwise varies at lower tropospheric heights depending on the strength of convection. Finally, the maximum surface wind speeds of TCs Dina and Faxai can be linearly estimated with total energy densities.

  8. Analysis of gravity-waves produced by intense tropical cyclones

    Energy Technology Data Exchange (ETDEWEB)

    Chane Ming, F. [La Reunion Univ. (France). Lab. de l' Atmosphere et des Cyclones; Chen, Z. [Chinese Academy of Sciences, Beijing (China). Inst. of Atmospheric; Roux, F. [UMR CNRS Paul Sabatier Univ., Toulouse (France). Lab. d' Aerologie

    2010-07-01

    Conventional and wavelet methods are combined to characterize gravity-waves (GWs) produced by two intense tropical cyclones (TCs) in the upper troposphere and lower stratosphere (UT/LS) from GPS winsonde data. Analyses reveal large contribution of GWs induced by TCs to wave energy densities in the UT/LS. An increase in total energy density of about 30% of the climatological energy density in austral summer was estimated in the LS above Tromelin during TC Dina. Four distinct periods in GW activity in relation with TC Faxai stages is observed in the UT. Globally, GWs have periods of 6 h-2.5 days, vertical wavelengths of 1-3 km and horizontal wavelengths <1000 km in the UT during the evolution of TCs. Horizontal wavelengths are longer in the LS and about 2200 km during TCs. Convective activity over the basin and GW energy density were modulated by mixed equatorial waves of 3-4 days, 6-8 days and 10-13 days confirmed by Hoevmoeller diagram, Fourier and wavelet analyses of OLR data. Moreover, location of GW sources is below the tropopause height when TCs are intense otherwise varies at lower tropospheric heights depending on the strength of convection. Finally, the maximum surface wind speeds of TCs Dina and Faxai can be linearly estimated with total energy densities. (orig.)

  9. Satellite Observations of Stratospheric Gravity Waves Associated With the Intensification of Tropical Cyclones

    Science.gov (United States)

    Hoffmann, Lars; Wu, Xue; Alexander, M. Joan

    2018-02-01

    Forecasting the intensity of tropical cyclones is a challenging problem. Rapid intensification is often preceded by the formation of "hot towers" near the eyewall. Driven by strong release of latent heat, hot towers are high-reaching tropical cumulonimbus clouds that penetrate the tropopause. Hot towers are a potentially important source of stratospheric gravity waves. Using 13.5 years (2002-2016) of Atmospheric Infrared Sounder observations of stratospheric gravity waves and tropical cyclone data from the International Best Track Archive for Climate Stewardship, we found empirical evidence that stratospheric gravity wave activity is associated with the intensification of tropical cyclones. The Atmospheric Infrared Sounder and International Best Track Archive for Climate Stewardship data showed that strong gravity wave events occurred about twice as often for tropical cyclone intensification compared to storm weakening. Observations of stratospheric gravity waves, which are not affected by obscuring tropospheric clouds, may become an important future indicator of storm intensification.

  10. Mesospheric gravity waves observed near equatorial and low-middle latitude stations: wave characteristics and reverse ray tracing results

    Energy Technology Data Exchange (ETDEWEB)

    Wrasse, C.M.; Takahashi, H.; Gobbi, D.; Denardini, C.M.; Fechine, J. [Inst. Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos (Brazil); Nakamura, T. [Inst. for Sustainable Humanosphere (RISH), Kyoto Univ., Uji (Japan); Medeiros, A.F.; Buriti, R.A. [Univ. Federal de Campina Grande (UFCG), Campina Grande (Brazil); Taylor, M.J. [Space Dynamics Lab. and Physics Dept., Logan, UT (United States); Salatun, A.; Suratno; Achmad, E.; Admiranto, A.G. [Space Science Center, National Inst. of Aeronautics and Space, Jakarta (Indonesia)

    2006-07-01

    Gravity wave signatures were extracted from OH airglow observations using all-sky CCD imagers at four different stations: Cachoeira Paulista (CP) (22.7 S, 45 W) and Sao Joao do Cariri (7.4 S, 36.5 W), Brazil; Tanjungsari (TJS) (6.9 S, 107.9 E), Indonesia and Shigaraki (34.9 N, 136 E), Japan. The gravity wave parameters are used as an input in a reverse ray tracing model to study the gravity wave vertical propagation trajectory and to estimate the wave source region. Gravity waves observed near the equator showed a shorter period and a larger phase velocity than those waves observed at low-middle latitudes. The waves ray traced down into the troposphere showed the largest horizontal wavelength and phase speed. The ray tracing results also showed that at CP, Cariri and Shigaraki the majority of the ray paths slopped in the mesosphere due to the condition of m{sup 2} <0, while at TJS most of the waves are traced back into the troposphere. In summer time, most of the back traced waves have their final position stopped in the mesosphere due to m{sup 2}<0 or critical level interactions (vertical stroke m vertical stroke {yields}{infinity}), which suggests the presence of ducting waves and/or waves generated in-situ. In the troposphere, the possible gravity wave sources are related to meteorological front activities and cloud convections at CP, while at Cariri and TJS tropical cloud convections near the equator are the most probable gravity wave sources. The tropospheric jet stream and the orography are thought to be the major responsible sources for the waves observed at Shigaraki. (orig.)

  11. Gravity wave propagation in the realistic atmosphere based on a three-dimensional transfer function model

    Directory of Open Access Journals (Sweden)

    L. Sun

    2007-10-01

    Full Text Available In order to study the filter effect of the background winds on the propagation of gravity waves, a three-dimensional transfer function model is developed on the basis of the complex dispersion relation of internal gravity waves in a stratified dissipative atmosphere with background winds. Our model has successfully represented the main results of the ray tracing method, e.g. the trend of the gravity waves to travel in the anti-windward direction. Furthermore, some interesting characteristics are manifest as follows: (1 The method provides the distribution characteristic of whole wave fields which propagate in the way of the distorted concentric circles at the same altitude under the control of the winds. (2 Through analyzing the frequency and wave number response curve of the transfer function, we find that the gravity waves in a wave band of about 15–30 min periods and of about 200–400 km horizontal wave lengths are most likely to propagate to the 300-km ionospheric height. Furthermore, there is an obvious frequency deviation for gravity waves propagating with winds in the frequency domain. The maximum power of the transfer function with background winds is smaller than that without background winds. (3 The atmospheric winds may act as a directional filter that will permit gravity wave packets propagating against the winds to reach the ionospheric height with minimum energy loss.

  12. A case study of typhoon-induced gravity waves and the orographic impacts related to Typhoon Mindulle (2004) over Taiwan

    OpenAIRE

    Wu, J. F.; Xue, X. H.; Hoffmann, L.; Dou, X. K.; Li, H. M.; Chen, T. D.

    2015-01-01

    Atmospheric gravity waves (GWs) significantly influence global circulation. Deep convection, particularly that associated with typhoons, is believed to be an important source of gravity waves. Stratospheric gravity waves induced by Typhoon Mindulle (2004) were detected by the Atmospheric Infrared Sounder (AIRS). Semicircular GWs with horizontal wavelengths of 100–400 km were found over Taiwan through an inspection of AIRS radiances at 4.3 μm. Characteristics of the stratospheric gravity waves...

  13. Gravity Wave Emission by Spontaneous Imbalance of Baroclinic Waves in the Continuously Stratified Rotating Annulus

    Science.gov (United States)

    Borchert, Sebastian; Achatz, Ulrich; Rieper, Felix; Fruman, Mark

    2013-04-01

    We use a numerical model of the classic differentially heated rotating annulus experiment to study the spontaneous emission of gravity waves (GWs) from jet stream imbalances, which is a major source of these waves in the atmosphere for which no satisfactory parameterization exists. Atmospheric observations are the main tool for the testing and verification of theoretical concepts but have their limitations. Given their specific potential for yielding reproducible data and for studying process dependence on external system parameters, laboratory experiments are an invaluable complementary tool. Experiments with a rotating annulus exhibiting a jet modulated by large-scale waves due to baroclinic instability have already been used to study GWs: Williams et al (2008) observed spontaneously emitted interfacial GWs in a two-layer flow, and Jacoby et al (2011) detected GWs emitted from boundary-layer instabilities in a differentially heated rotating annulus. Employing a finite-volume code for the numerical simulation of a continuously stratified liquid in a differentially heated rotating annulus, we here investigate the GWs in a wide and shallow annulus with relatively large temperature difference between inner and outer cylinder walls. In this atmosphere-like regime where the Brunt-Vaisala frequency is larger than the inertial frequency, various analyses suggest a distinct gravity wave activity. To identify regions of GW emission we decompose the flow into the geostrophic and ageostrophic part through the inversion of the quasi-geostrophic potential vorticity (e.g. Verkley, 2009). The analysis of the geostrophic sources of the ageostrophic flow indicates that, in addition to boundary layer instabilities, spontaneous imbalance in the jet region acts as an important source mechanism. Jacoby, T. N. L., Read, P. L., Williams, P. D. and Young, R. M. B., 2011: Generation of inertia-gravity waves in the rotating thermal annulus by a localised boundary layer instability. Geophys

  14. Particle dispersion and mixing induced by breaking internal gravity waves

    Science.gov (United States)

    Bouruet-Aubertot, Pascale; Koudella, C.; Staquet, C.; Winters, K. B.

    2001-01-01

    The purpose of this paper is to analyze diapycnal mixing induced by the breaking of an internal gravity wave — the primary wave — either standing or propagating. To achieve this aim we apply two different methods. The first method consists of a direct estimate of vertical eddy diffusion from particle dispersion while the second method relies upon potential energy budgets [Winters, K.B., Lombard, P.N., Riley, J.J., D'Asaro, E.A., 1995. J. Fluid Mech. 289, 115-128; Winters, K.B., D'Asaro, E.A., 1996. J. Fluid Mech. 317, 179-193]. The primary wave we consider is of small amplitude and is statically stable, a case for which the breaking process involves two-dimensional instabilities. The dynamics of the waves have been previously analyzed by means of two-dimensional direct numerical simulations [Bouruet-Aubertot, P., Sommeria, J., Staquet, C., 1995. J. Fluid Mech. 285, 265-301; Bouruet-Aubertot, P., Sommeria, J., Staquet, C., 1996. Dyn. Atmos. Oceans 29, 41-63; Koudella, C., Staquet, C., 1998. In: Davis, P. (Ed.), Proceedings of the IMA Conference on Mixing and Dispersion on Stably-stratified Flows, Dundee, September 1996. IMA Publication]. High resolution three-dimensional calculations of the same wave are also reported here [Koudella, C., 1999]. A local estimate of mixing is first inferred from the time evolution of sets of particles released in the flow during the breaking regime. We show that, after an early evolution dominated by shear effects, a diffusion law is reached and the dispersion coefficient is fairly independent of the initial seeding location of the particles in the flow. The eddy diffusion coefficient, K, is then estimated from the diapycnal diffusive flux. A good agreement with the value inferred from particle dispersion is obtained. This finding is of particular interest regarding the interpretation of in situ estimates of K inferred either from tracer dispersion or from microstructure measurements. Computation of the Cox number, equal to the

  15. Activity of convective tropical gravity-waves above the south west indian ocean

    Science.gov (United States)

    Evan, S.; Chane-Ming, F.; Keckhut, P.

    Tropical gravity waves play an important role in the dynamics of the middle atmosphere Such small-scale waves can transport energy and momentum vertically as well as horizontally from the troposphere to the middle and upper atmosphere affecting the global circulation Recent studies have focused on the characterization of gravity-waves from local and global observation to improve numerical modelling in terms of parameterisation and comparison for more realistic outputs Many studies have used high-resolution radiosoundings but first climatologies concern continental regions such as Australia and the US Allen and Vincent 1995 Wang and Geller 2003 In the tropics and over ocean and especially in the South-West Indian Ocean measurements are scarce and little is known about the activity of the gravity-waves except using satellite data for large-scale gravity waves above the lower stratosphere In this study a climatology and spatial distribution of the gravity-wave activity for the South West Indian Ocean is produced The dataset includes measurements of daily soundings in the South-West Indian Ocean located between 4oS-30oS and 30oE-56oE Waves parameters energy spatial and temporal scales of waves direction of horizontal wave propagation are analyzed from January 1998 to November 2005 in the troposphere and lower stratosphere A daily activity and wave sources tropical cyclones QBO convection are also investigated

  16. Internal Gravity Waves in the Magnetized Solar Atmosphere. I. Magnetic Field Effects

    Energy Technology Data Exchange (ETDEWEB)

    Vigeesh, G.; Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstrasse 6, D-79104 Freiburg (Germany); Jackiewicz, J., E-mail: vigeesh@leibniz-kis.de [New Mexico State University, Department of Astronomy, P.O. Box 30001, MSC 4500, Las Cruces, NM 88003 (United States)

    2017-02-01

    Observations of the solar atmosphere show that internal gravity waves are generated by overshooting convection, but are suppressed at locations of magnetic flux, which is thought to be the result of mode conversion into magnetoacoustic waves. Here, we present a study of the acoustic-gravity wave spectrum emerging from a realistic, self-consistent simulation of solar (magneto)convection. A magnetic field free, hydrodynamic simulation and a magnetohydrodynamic (MHD) simulation with an initial, vertical, homogeneous field of 50 G flux density were carried out and compared with each other to highlight the effect of magnetic fields on the internal gravity wave propagation in the Sun’s atmosphere. We find that the internal gravity waves are absent or partially reflected back into the lower layers in the presence of magnetic fields and argue that the suppression is due to the coupling of internal gravity waves to slow magnetoacoustic waves still within the high- β region of the upper photosphere. The conversion to Alfvén waves is highly unlikely in our model because there is no strongly inclined magnetic field present. We argue that the suppression of internal waves observed within magnetic flux concentrations may also be due to nonlinear breaking of internal waves due to vortex flows that are ubiquitously present in the upper photosphere and the chromosphere.

  17. Spontaneous development of rotating inertial gravity wave inside the cylindrical tank with combined in- and outflow

    Science.gov (United States)

    Fedorchenko, A. I.; Stachiv, I.; Trávníček, Z.

    2013-06-01

    A new phenomenon of the spontaneous development of the rotating inertial gravity wave inside the rigid cylindrical tank has been observed. The experimental set-up combines both the inflow and outflow. Three regimes of the flow inside the tank have been disclosed for the fixed rate of the liquid height change: a) nonrotating flow, b) nonrotating flow with the ripple localized to the tank's wall, and c) emergence of the rotating inertial gravity wave. The rotating inertial gravity wave forces the fluid to rotate in the opposite direction. Each of these regimes is realized in some ranges of the outlet diameters and liquid heights, and the maps of these regimes are established.

  18. Comparison of Global Distributions of Zonal-Mean Gravity Wave Variance Inferred from Different Satellite Instruments

    Science.gov (United States)

    Preusse, Peter; Eckermann, Stephen D.; Offermann, Dirk; Jackman, Charles H. (Technical Monitor)

    2000-01-01

    Gravity wave temperature fluctuations acquired by the CRISTA instrument are compared to previous estimates of zonal-mean gravity wave temperature variance inferred from the LIMS, MLS and GPS/MET satellite instruments during northern winter. Careful attention is paid to the range of vertical wavelengths resolved by each instrument. Good agreement between CRISTA data and previously published results from LIMS, MLS and GPS/MET are found. Key latitudinal features in these variances are consistent with previous findings from ground-based measurements and some simple models. We conclude that all four satellite instruments provide reliable global data on zonal-mean gravity wave temperature fluctuations throughout the middle atmosphere.

  19. Gravity waves as a probe of the Hubble expansion rate during an electroweak scale phase transition

    International Nuclear Information System (INIS)

    Chung, Daniel J. H.; Zhou Peng

    2010-01-01

    Just as big bang nucleosynthesis allows us to probe the expansion rate when the temperature of the Universe was around 1 MeV, the measurement of gravity waves from electroweak scale first order phase transitions may allow us to probe the expansion rate when the temperature of the Universe was at the electroweak scale. We compute the simple transformation rule for the gravity wave spectrum under the scaling transformation of the Hubble expansion rate. We then apply this directly to the scenario of quintessence kination domination and show how gravity wave spectra would shift relative to Laser Interferometer Space Antenna and Big Bang Observer projected sensitivities.

  20. Internal Gravity Wave Interactions with Double-Diffusive Instabilities

    Science.gov (United States)

    Brown, Justin; Radko, Timour

    2017-04-01

    In this study, we focus on the phenomenon of oscillatory double-diffusive convection, which occurs when cool fresh water is stratified above warm salty water, as commonly observed in the Arctic Ocean. In the Arctic, these regions are generally stable to the development of oscillatory double-diffusive instabilities; despite this, observations show the presence of staircases, i.e., the well-defined structures consisting of a series of homogeneous layers separated by thin high-gradient interfaces. Recent studies have shown that an instability can develop in such circumstances if weak static shear is present even when the shear and double-diffusion are themselves individually stable. However, the impact of oscillating shear, associated with the ubiquitous presence of internal gravity waves, has not yet been addressed for the diffusive case. Through two-dimensional simulations of diffusive convection, we have investigated the impact of magnitude and frequency of externally forced internal waves on the double-diffusive shear instability. The analysis is focused on the parameter regime in which the flow is individually stable with respect to double-diffusion and Kelvin-Helmholtz instabilities, but could be susceptible to the combined thermohaline-shear instability. We have illustrated that rapid oscillation inhibits the development of this instability if the dominant period is shorter than four hours for the oceanographically relevant parameters; otherwise, models with static shear adequately reproduce our results. If the dominant period is shorter than four hours but still significantly exceeds the buoyancy period, the instability range is much reduced to the low Richardson number regime. Some of these simulations show the saturated system developing into structures reminiscent of double-diffusive staircases whose thickness is given by the wavelength of the forced shear. Finally, preliminary three-dimensional simulations show no major differences in the growth rate of

  1. Mesospheric gravity wave momentum flux estimation using hybrid Doppler interferometry

    Directory of Open Access Journals (Sweden)

    A. J. Spargo

    2017-06-01

    Full Text Available Mesospheric gravity wave (GW momentum flux estimates using data from multibeam Buckland Park MF radar (34.6° S, 138.5° E experiments (conducted from July 1997 to June 1998 are presented. On transmission, five Doppler beams were symmetrically steered about the zenith (one zenith beam and four off-zenith beams in the cardinal directions. The received beams were analysed with hybrid Doppler interferometry (HDI (Holdsworth and Reid, 1998, principally to determine the radial velocities of the effective scattering centres illuminated by the radar. The methodology of Thorsen et al. (1997, later re-introduced by Hocking (2005 and since extensively applied to meteor radar returns, was used to estimate components of Reynolds stress due to propagating GWs and/or turbulence in the radar resolution volume. Physically reasonable momentum flux estimates are derived from the Reynolds stress components, which are also verified using a simple radar model incorporating GW-induced wind perturbations. On the basis of these results, we recommend the intercomparison of momentum flux estimates between co-located meteor radars and vertical-beam interferometric MF radars. It is envisaged that such intercomparisons will assist with the clarification of recent concerns (e.g. Vincent et al., 2010 of the accuracy of the meteor radar technique.

  2. Tropical Gravity Wave Momentum Fluxes and Latent Heating Distributions

    Science.gov (United States)

    Geller, Marvin A.; Zhou, Tiehan; Love, Peter T.

    2015-01-01

    Recent satellite determinations of global distributions of absolute gravity wave (GW) momentum fluxes in the lower stratosphere show maxima over the summer subtropical continents and little evidence of GW momentum fluxes associated with the intertropical convergence zone (ITCZ). This seems to be at odds with parameterizations forGWmomentum fluxes, where the source is a function of latent heating rates, which are largest in the region of the ITCZ in terms of monthly averages. The authors have examined global distributions of atmospheric latent heating, cloud-top-pressure altitudes, and lower-stratosphere absolute GW momentum fluxes and have found that monthly averages of the lower-stratosphere GW momentum fluxes more closely resemble the monthly mean cloud-top altitudes rather than the monthly mean rates of latent heating. These regions of highest cloud-top altitudes occur when rates of latent heating are largest on the time scale of cloud growth. This, plus previously published studies, suggests that convective sources for stratospheric GW momentum fluxes, being a function of the rate of latent heating, will require either a climate model to correctly model this rate of latent heating or some ad hoc adjustments to account for shortcomings in a climate model's land-sea differences in convective latent heating.

  3. A global climatology of stratospheric gravity waves from Atmospheric Infrared Sounder observations

    Science.gov (United States)

    Hoffmann, Lars; Xue, Xianghui; Alexander, M. Joan

    2014-05-01

    We present the results of a new study that aims on the detection and classification of `hotspots' of stratospheric gravity waves on a global scale. The analysis is based on a nine-year record (2003 to 2011) of radiance measurements by the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite. We detect the presence of stratospheric gravity waves based on 4.3 micron brightness temperature variances. Our method is optimized for peak events, i.e., strong gravity wave events for which the local variance considerably exceeds background levels. We estimated the occurrence frequencies of these peak events for different seasons and time of day and used the results to find local maxima of gravity wave activity. In addition, we use AIRS radiances at 8.1 micron to simultaneously detect convective events, including deep convection in the tropics and mesoscale convective systems at mid latitudes. We classified the gravity waves according to their sources, based on seasonal occurrence frequencies for convection and by means of topographic data. Our study reproduces well-known hotspots of gravity waves, e.g., the mountain wave hotspots at the Andes and the Antarctic Peninsula or the convective hotspot during the thunderstorm season over the North American Great Plains. However, the high horizontal resolution of the AIRS observations also helped us to locate several smaller hotspots, which were partly unknown or poorly studied so far. Most of these smaller hotspots are found near orographic features like small mountain ranges, in coastal regions, in desert areas, or near isolated islands. This new study will help to select the most promising regions and seasons for future observational studies of gravity waves. Reference: Hoffmann, L., X. Xue, and M. J. Alexander, A global view of stratospheric gravity wave hotspots located with Atmospheric Infrared Sounder observations, J. Geophys. Res., 118, 416-434, doi:10.1029/2012JD018658, 2013.

  4. Detection of traveling ionospheric disturbances induced by atmospheric gravity waves using the global positioning system

    Science.gov (United States)

    Bassiri, Sassan; Hajj, George A.

    1993-01-01

    Natural and man-made events like earthquakes and nuclear explosions launch atmospheric gravity waves (AGW) into the atmosphere. Since the particle density decreases exponentially with height, the gravity waves increase exponentially in amplitude as they propagate toward the upper atmosphere and ionosphere. As atmospheric gravity waves approach the ionospheric heights, the neutral particles carried by gravity waves collide with electrons and ions, setting these particles in motion. This motion of charged particles manifests itself by wave-like fluctuations and disturbances that are known as traveling ionospheric disturbances (TID). The perturbation in the total electron content due to TID's is derived analytically from first principles. Using the tilted dipole magnetic field approximation and a Chapman layer distribution for the electron density, the variations of the total electron content versus the line-of-sight direction are numerically analyzed. The temporal variation associated with the total electron content measurements due to AGW's can be used as a means of detecting characteristics of the gravity waves. As an example, detection of tsunami generated earthquakes from their associated atmospheric gravity waves using the Global Positioning System is simulated.

  5. Thermal effect on gravity waves in a compressible liquid layer over a ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the influence of initial compressive hydrostatic stress. When the temperature of the.

  6. Thermal effect on gravity waves in a compressible liquid layer over a ...

    Indian Academy of Sciences (India)

    This paper deals with the effect of temperature on gravity waves in a compressible liquid layer over a solid half-space. It has been assumed that the liquid layer is under the action of gravity, while the solid half-space is under the influence of initial compressive hydrostatic stress. When the temperature of the half-space is ...

  7. Ultra-Low Noise Quad Photoreceiver for Space Based Laser Interferometric Gravity Wave Detection, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Gravity wave detection using space-based long-baseline laser interferometric sensors imposes stringent noise requirements on the system components, including the...

  8. Gravity wave characteristics over Tromelin Island during the passage of cyclone Hudah

    Science.gov (United States)

    Chane-Ming, Fabrice; Roff, Greg; Robert, Laurent; Leveau, Jean

    2002-03-01

    The time and spatial evolution of gravity-wave characteristics are analysed using wavelets in vertical profiles of temperature and winds at Tromelin Island (15.53°S, 54.31°E) during the passage of the intense tropical cyclone Hudah in the Southern Ocean Indian Basin in 2000. Inertia-gravity waves were observed in the upper troposphere and the lower stratosphere with dominant vertical wavelengths of 1.5-3 km, horizontal wavelengths <2000 km and periods of 0.6-1.6 days. Large amounts of gravity-wave energy were detected during landfalls of the tropical cyclone. The distribution of total energy indicates that mesoscale convective structures such as tropical cyclones are important gravity-wave sources in the upper troposphere.

  9. Evaluation of methods for gravity wave extraction from middle-atmospheric lidar temperature measurements

    Directory of Open Access Journals (Sweden)

    B. Ehard

    2015-11-01

    Full Text Available This study evaluates commonly used methods of extracting gravity-wave-induced temperature perturbations from lidar measurements. The spectral response of these methods is characterized with the help of a synthetic data set with known temperature perturbations added to a realistic background temperature profile. The simulations are carried out with the background temperature being either constant or varying in time to evaluate the sensitivity to temperature perturbations not caused by gravity waves. The different methods are applied to lidar measurements over New Zealand, and the performance of the algorithms is evaluated. We find that the Butterworth filter performs best if gravity waves over a wide range of periods are to be extracted from lidar temperature measurements. The running mean method gives good results if only gravity waves with short periods are to be analyzed.

  10. A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995

    Directory of Open Access Journals (Sweden)

    K. Hocke

    1996-09-01

    Full Text Available Recent investigations of atmospheric gravity waves (AGW and travelling ionospheric disturbances (TID in the Earth\\'s thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS, the results are presented in the first part of the review. The second part describes the progress towards understanding the AGW/TID characteristics. It points to the AGW/TID relationship which has been recently revealed with the aid of model-data comparisons and by the application of new inversion techniques. We describe the morphology and climatology of gravity waves and their ionospheric manifestations, TIDs, from numerous new observations.

  11. A review of atmospheric gravity waves and travelling ionospheric disturbances: 1982-1995

    Directory of Open Access Journals (Sweden)

    K. Hocke

    Full Text Available Recent investigations of atmospheric gravity waves (AGW and travelling ionospheric disturbances (TID in the Earth's thermosphere and ionosphere are reviewed. In the past decade, the generation of gravity waves at high latitudes and their subsequent propagation to low latitudes have been studied by several global model simulations and coordinated observation campaigns such as the Worldwide Atmospheric Gravity-wave Study (WAGS, the results are presented in the first part of the review. The second part describes the progress towards understanding the AGW/TID characteristics. It points to the AGW/TID relationship which has been recently revealed with the aid of model-data comparisons and by the application of new inversion techniques. We describe the morphology and climatology of gravity waves and their ionospheric manifestations, TIDs, from numerous new observations.

  12. Observation and Modeling of Tsunami-Generated Gravity Waves in the Earth’s Upper Atmosphere

    Science.gov (United States)

    2015-10-08

    Observation and modeling of tsunami-generated gravity waves in the earth’s upper atmosphere 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6... perturbations caused by the GWs) as a function of space and time at the altitudes z=200-300 km. These perturbations will then be given to Dr. Makela to...for public release; distribution is unlimited. Observation and modeling of tsunami-generated gravity waves in the earth’s upper atmosphere Sharon

  13. Gravitational Wave Polarizations in f (R Gravity and Scalar-Tensor Theory

    Directory of Open Access Journals (Sweden)

    Gong Yungui

    2018-01-01

    Full Text Available The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity. We investigate the polarizations of gravitational waves in f (R gravity and Horndeski theory, both containing scalar modes. These theories predict that in addition to the familiar + and × polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state. It would be very difficult to detect the longitudinal polarization by interferometers, while pulsar timing array may be the better tool to detect the longitudinal polarization.

  14. Gravitational Wave Polarizations in f (R) Gravity and Scalar-Tensor Theory

    Science.gov (United States)

    Gong, Yungui; Hou, Shaoqi

    2018-01-01

    The detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory opens a new era to use gravitational waves to test alternative theories of gravity. We investigate the polarizations of gravitational waves in f (R) gravity and Horndeski theory, both containing scalar modes. These theories predict that in addition to the familiar + and × polarizations, there are transverse breathing and longitudinal polarizations excited by the massive scalar mode and the new polarization is a single mixed state. It would be very difficult to detect the longitudinal polarization by interferometers, while pulsar timing array may be the better tool to detect the longitudinal polarization.

  15. Complexity-action duality of the shock wave geometry in a massive gravity theory

    Science.gov (United States)

    Miao, Yan-Gang; Zhao, Long

    2018-01-01

    On the holographic complexity dual to the bulk action, we investigate the action growth for a shock wave geometry in a massive gravity theory within the Wheeler-DeWitt (WDW) patch at the late time limit. For a global shock wave, the graviton mass does not affect the action growth in the bulk, i.e., the complexity on the boundary, showing that the action growth (complexity) is the same for both the Einstein gravity and the massive gravity. Nevertheless, for a local shock wave that depends on transverse coordinates, the action growth (complexity) caused by the boundary disturbance (perturbation) is proportional to the butterfly velocity for the two gravity theories, but the butterfly velocity of the massive gravity theory is smaller than that of the Einstein gravity theory, indicating that the action growth (complexity) of the massive gravity is depressed by the graviton mass. In addition, we extend the black hole thermodynamics of the massive gravity and obtain the right Smarr formula.

  16. Atmospheric gravity waves observed by an international network of micro-barographs

    International Nuclear Information System (INIS)

    Marty, Julien

    2010-01-01

    The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) manages an international network of forty-two operational infra-sound stations recording the pressure fluctuations produced at the ground surface by infrasonic waves. This thesis demonstrates that most of these stations also accurately detect the pressure fluctuations in the entire gravity wave band. This work includes carrying out and analyzing several metrological laboratory experiments and a field campaign (M2008) in Mongolia in 2008. The layout of the experiments as well as the interpretation of their results gave rise to the development of a new linear spectral numerical model able to simulate the generation and propagation of gravity waves. This model was used to quantify the gravity waves produced by the atmospheric cooling that occurs during solar eclipses. The pressure fluctuations expected at ground level were estimated and compared to the data recorded during the 1 August 2008 solar eclipse by the CTBTO and M2008 stations. A detailed data analysis reveals two waves with similar time-frequency characteristics to those simulated for a stratospheric and tropospheric cooling. This constitutes, to our knowledge, a unique result. The validation of worldwide and pluri-annual pressure measurements in the entire gravity wave band allowed the statistical study of gravity wave spectra and atmospheric tides. The work presented throughout this thesis has led to the publication of two articles. A third one is in the drafting process. (author)

  17. Numerical Study of Balearic Meteotsunami Generation and Propagation under Synthetic Gravity Wave Forcing

    Science.gov (United States)

    Licer, Matjaz; Mourre, Baptiste; Troupin, Charles; Krietemeyer, Andreas; Tintoré, Joaquín

    2017-04-01

    A high resolution nested ocean modelling system forced by synthetic atmospheric gravity waves is used to investigate meteotsunami generation, amplification and propagation properties over the Mallorca-Menorca shelf (Balearic Islands, Western Mediterranean Sea). We determine how meteotsunami amplitude outside and inside of the Balearic port of Ciutadella depends on forcing gravity wave direction, speed and trajectory. Contributions of Mallorca shelves and Menorca Channel are quantified for different gravity wave forcing angles and speeds. Results indicate that the Channel is the key build-up region and that Northern and Southern Mallorca shelves do not significantly contribute to the amplitude of substantial harbour oscillations in Ciutadella. This fact seriously reduces early-warning alert times in cases of locally generated pressure perturbations. Tracking meteotsunami propagation paths in the Menorca Channel for several forcing velocities, we show that the Channel bathymetry serves as a focusing lens for meteotsunami waves whose paths are constrained by the forcing direction. Faster meteotsunamis are shown to propagate over deeper ocean regions, as required by the Proudman resonance. Meteotsunami speed under sub- and supercritical forcing is estimated and a first order estimate of its magnitude is derived. Meteotsunamis generated by the supercritical gravity waves are found to propagate with a velocity which is equal to an arithmetic mean of the gravity wave speed and local ocean barotropic wave speed.

  18. On weakly singular and fully nonlinear travelling shallow capillary–gravity waves in the critical regime

    Energy Technology Data Exchange (ETDEWEB)

    Mitsotakis, Dimitrios, E-mail: dmitsot@gmail.com [Victoria University of Wellington, School of Mathematics, Statistics and Operations Research, PO Box 600, Wellington 6140 (New Zealand); Dutykh, Denys, E-mail: Denys.Dutykh@univ-savoie.fr [LAMA, UMR 5127 CNRS, Université Savoie Mont Blanc, Campus Scientifique, F-73376 Le Bourget-du-Lac Cedex (France); Assylbekuly, Aydar, E-mail: asylbekuly@mail.ru [Khoja Akhmet Yassawi International Kazakh–Turkish University, Faculty of Natural Science, Department of Mathematics, 161200 Turkestan (Kazakhstan); Zhakebayev, Dauren, E-mail: daurjaz@mail.ru [Al-Farabi Kazakh National University, Faculty of Mechanics and Mathematics, Department of Mathematical and Computer Modelling, 050000 Almaty (Kazakhstan)

    2017-05-25

    In this Letter we consider long capillary–gravity waves described by a fully nonlinear weakly dispersive model. First, using the phase space analysis methods we describe all possible types of localized travelling waves. Then, we especially focus on the critical regime, where the surface tension is exactly balanced by the gravity force. We show that our long wave model with a critical Bond number admits stable travelling wave solutions with a singular crest. These solutions are usually referred to in the literature as peakons or peaked solitary waves. They satisfy the usual speed-amplitude relation, which coincides with Scott–Russel's empirical formula for solitary waves, while their decay rate is the same regardless their amplitude. Moreover, they can be of depression or elevation type independent of their speed. The dynamics of these solutions are studied as well. - Highlights: • A model for long capillary–gravity weakly dispersive and fully nonlinear water waves is derived. • Shallow capillary–gravity waves are classified using phase plane analysis. • Peaked travelling waves are found in the critical regime. • The dynamics of peakons in Serre–Green–Naghdi equations is studied numerically.

  19. Simultaneous airglow, lidar, and radar measurements of mesospheric gravity waves over Japan

    Science.gov (United States)

    Suzuki, Shin; Nakamura, Takuji; Ejiri, Mitsumu K.; Tsutsumi, Masaki; Shiokawa, Kazuo; Kawahara, Takuya D.

    In order to investigate the gravity wave dynamics in the mesosphere and lower thermosphere (MLT) region, we have conducted coordinated observations of mesospheric gravity waves during the ANDON campaign at midlatitude. Two all-sky airglow imagers (ASIs) were used in this campaign to derive two-dimensional structure of the gravity waves: one has been operated by Nagoya university as a part of the optical mesosphere thermosphere imagers (OMTIS) at the MU observatory in Shigaraki (34.9N, 136.1E), and the other imager, named ANDON, developed by Kyoto University is newly installed at the DYNIC Astropark Observatory in Taga (35.2N, 136.3E). Simultaneous horizontal winds and temperatures in the MLT region are provided by meteor-mode observations of the MU radar at Shigaraki and a sodium lidar at Uji (34.9N, 135.8E), respectively. On 2 October 2008, gravity waves with a horizontal wavelength of 180 km and wave period of 1 h propagating northeastward at 50 m/s were observed in the airglow keograms. We also found that similar wave structures were observed in the time-series of the meteor wind and lidar temperature, and their phase relations with the airglow intensity variations were consistent with the linear theory of gravity wave. The phase speed estimated from the MU radar and the momentum fluxes of the wave were also in good agreements with the airglow measurements. These results show that, for the first time, a comprehensive structure of mesospheric gravity waves (wave-induced airglow intensities, horizontal wind, and temperature perturbations) was observed.

  20. Characteristics of two gravity wave sources in the US high vertical-resolution radiosonde data

    Science.gov (United States)

    Gong, Jie

    Understanding gravity wave sources is essential to gravity wave research, and has profound effect on improving general circulation models (GCMs). My Ph.D. work is to analyze, diagnose and simulate the source behaviors of gravity waves that are observed in the US high vertical-resolution radiosonde data. Two sources---convection and jet imbalance---are of the major interest. I used a ray-tracing gravity wave model GROGRAT to characterize the "mean" source spectrum of gravity waves in the lower stratosphere that are observed from US high vertical-resolution radiosonde profiles on a monthly scale. With a fixed source spectral function, one can get "best-fits" for most of the stations. A universal source function is found to be most powerful in capturing the major features of the variations, while another, which represents the convection source, works better for tropical stations. "Fits" are generally better for winter than for summer, indicating possible jet-related sources. I furthermore examined the perturbation field of the ascent rate that is likely to be representative of higher-frequency gravity waves that are generated from the convection sources. The newly defined variable, VE, as well as the apparent dominant vertical wavelength analyzed from the ascent rate fluctuations turned out to be collocated very well with moist convection in the troposphere, especially during warm seasons. The waves tend to have higher frequencies, and this seems consistent with theory. Forcing terms associated with the jet imbalance source are analyzed on a climatological basis. The derived forcings reveal some characteristics of the jet imbalance source, which we can sometimes see in the radiosonde profiles. GROGRAT and a linear forcing-response model are used to study a specific case, which sheds some light on parameterizations of gravity wave drag associated with the jet imbalance.

  1. Universal power law of the gravity wave manifestation in the AIM CIPS polar mesospheric cloud images

    Directory of Open Access Journals (Sweden)

    P. Rong

    2018-01-01

    Full Text Available We aim to extract a universal law that governs the gravity wave manifestation in polar mesospheric clouds (PMCs. Gravity wave morphology and the clarity level of display vary throughout the wave population manifested by the PMC albedo data. Higher clarity refers to more distinct exhibition of the features, which often correspond to larger variances and a better-organized nature. A gravity wave tracking algorithm based on the continuous Morlet wavelet transform is applied to the PMC albedo data at 83 km altitude taken by the Aeronomy of Ice in the Mesosphere (AIM Cloud Imaging and Particle Size (CIPS instrument to obtain a large ensemble of the gravity wave detections. The horizontal wavelengths in the range of  ∼ 20–60 km are the focus of the study. It shows that the albedo (wave power statistically increases as the background gets brighter. We resample the wave detections to conform to a normal distribution to examine the wave morphology and display clarity beyond the cloud brightness impact. Sample cases are selected at the two tails and the peak of the normal distribution to represent the full set of wave detections. For these cases the albedo power spectra follow exponential decay toward smaller scales. The high-albedo-power category has the most rapid decay (i.e., exponent  =  −3.2 and corresponds to the most distinct wave display. The wave display becomes increasingly blurrier for the medium- and low-power categories, which hold the monotonically decreasing spectral exponents of −2.9 and −2.5, respectively. The majority of waves are straight waves whose clarity levels can collapse between the different brightness levels, but in the brighter background the wave signatures seem to exhibit mildly turbulent-like behavior.

  2. Universal power law of the gravity wave manifestation in the AIM CIPS polar mesospheric cloud images

    Science.gov (United States)

    Rong, Pingping; Yue, Jia; Russell, James M., III; Siskind, David E.; Randall, Cora E.

    2018-01-01

    We aim to extract a universal law that governs the gravity wave manifestation in polar mesospheric clouds (PMCs). Gravity wave morphology and the clarity level of display vary throughout the wave population manifested by the PMC albedo data. Higher clarity refers to more distinct exhibition of the features, which often correspond to larger variances and a better-organized nature. A gravity wave tracking algorithm based on the continuous Morlet wavelet transform is applied to the PMC albedo data at 83 km altitude taken by the Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument to obtain a large ensemble of the gravity wave detections. The horizontal wavelengths in the range of ˜ 20-60 km are the focus of the study. It shows that the albedo (wave) power statistically increases as the background gets brighter. We resample the wave detections to conform to a normal distribution to examine the wave morphology and display clarity beyond the cloud brightness impact. Sample cases are selected at the two tails and the peak of the normal distribution to represent the full set of wave detections. For these cases the albedo power spectra follow exponential decay toward smaller scales. The high-albedo-power category has the most rapid decay (i.e., exponent = -3.2) and corresponds to the most distinct wave display. The wave display becomes increasingly blurrier for the medium- and low-power categories, which hold the monotonically decreasing spectral exponents of -2.9 and -2.5, respectively. The majority of waves are straight waves whose clarity levels can collapse between the different brightness levels, but in the brighter background the wave signatures seem to exhibit mildly turbulent-like behavior.

  3. The role of linear wave interaction in facilitating the upward propagation of ducted small-scale gravity waves.

    Science.gov (United States)

    Heale, C. J.; Snively, J. B.

    2014-12-01

    Short-period (~5-15 minute), small-scale (10s of km) gravity waves propagating through the middle atmosphere will encounter and interact with other atmospheric waves and flows, which can vary horizontally, vertically, and temporally across a wide range of scales. Simulations of gravity wave impacts over global scales generally consider vertical propagation and atmospheric variations, and neglect small scale wave reflection and interactions between waves of different scales and the time dependent background atmosphere [e.g., Fritts and Alexander, Rev. Geo., 41, 1, 2003, and references cited therein]. Short period gravity waves , which are often subject to reflection, nevertheless carry significant momentum through the atmosphere [Hines, 1997, J. Atmos. Sol. Terr. Phys., 59].
Prior studies have investigated gravity wave propagation through horizontally sheared winds [e.g., Basovich and Tsimring, J. Fluid. Mech., 142, 1984], or in altitude and time varying backgrounds [e.g., Broutman and Young, J. Fluid. Mech., 166, 1986]. Senf and Achatz [JGR, 116, D24, 2011, and references cited therein] have also considered propagation through vertically, horizontally, and temporally varying background winds, finding significant reduction of dissipation by critical levels. We here use a combination of 2D numerical simulations and ray-tracing to study the effects of medium scale background wave wind fields on the upward propagation of small-scale, short-period waves. In particular, we consider cases where the short-period waves would be classically reflected or ducted in static realistic background temperature and wind structures. Results suggest an important role for medium-scale temporal and spatial atmospheric variability in reducing the strength of reflections and facilitating the upward propagation of small-scale waves.

  4. The influence of solar wind on extratropical cyclones – Part 2: A link mediated by auroral atmospheric gravity waves?

    Directory of Open Access Journals (Sweden)

    P. Prikryl

    2009-01-01

    Full Text Available Cases of mesoscale cloud bands in extratropical cyclones are observed a few hours after atmospheric gravity waves (AGWs are launched from the auroral ionosphere. It is suggested that the solar-wind-generated auroral AGWs contribute to processes that release instabilities and initiate slantwise convection thus leading to cloud bands and growth of extratropical cyclones. Also, if the AGWs are ducted to low latitudes, they could influence the development of tropical cyclones. The gravity-wave-induced vertical lift may modulate the slantwise convection by releasing the moist symmetric instability at near-threshold conditions in the warm frontal zone of extratropical cyclones. Latent heat release associated with the mesoscale slantwise convection has been linked to explosive cyclogenesis and severe weather. The circumstantial and statistical evidence of the solar wind influence on extratropical cyclones is further supported by a statistical analysis of high-level clouds (<440 mb extracted from the International Satellite Cloud Climatology Project (ISCCP D1 dataset. A statistically significant response of the high-level cloud area index (HCAI to fast solar wind from coronal holes is found in mid-to-high latitudes during autumn-winter and in low latitudes during spring-summer. In the extratropics, this response of the HCAI to solar wind forcing is consistent with the effect on tropospheric vorticity found by Wilcox et al. (1974 and verified by Prikryl et al. (2009. In the tropics, the observed HCAI response, namely a decrease in HCAI at the arrival of solar wind stream followed by an increase a few days later, is similar to that in the northern and southern mid-to-high latitudes. The amplitude of the response nearly doubles for stream interfaces associated with the interplanetary magnetic field BZ component shifting southward. When the IMF BZ after the stream interface shifts northward, the autumn-winter effect weakens or shifts to lower (mid latitudes

  5. Does Strong Tropospheric Forcing Cause Large-Amplitude Mesospheric Gravity Waves? A DEEPWAVE Case Study

    Science.gov (United States)

    Bramberger, Martina; Dörnbrack, Andreas; Bossert, Katrina; Ehard, Benedikt; Fritts, David C.; Kaifler, Bernd; Mallaun, Christian; Orr, Andrew; Pautet, P.-Dominique; Rapp, Markus; Taylor, Michael J.; Vosper, Simon; Williams, Bifford P.; Witschas, Benjamin

    2017-11-01

    On 4 July 2014, during the Deep Propagating Gravity Wave Experiment (DEEPWAVE), strong low-level horizontal winds of up to 35 m s-1 over the Southern Alps, New Zealand, caused the excitation of gravity waves having the largest vertical energy fluxes of the whole campaign (38 W m-2). At the same time, large-amplitude mesospheric gravity waves were detected by the Temperature Lidar for Middle Atmospheric Research (TELMA) located at Lauder (45.0°S, 169.7°E), New Zealand. The coincidence of these two events leads to the question of whether the mesospheric gravity waves were generated by the strong tropospheric forcing. To answer this, an extensive data set is analyzed, comprising TELMA, in situ aircraft measurements, radiosondes, wind lidar measurements aboard the DLR Falcon as well as Rayleigh lidar and advanced mesospheric temperature mapper measurements aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V. These measurements are further complemented by limited area simulations using a numerical weather prediction model. This unique data set confirms that strong tropospheric forcing can cause large-amplitude gravity waves in the mesosphere, and that three essential ingredients are required to achieve this: first, nearly linear propagation across the tropopause; second, leakage through the stratospheric wind minimum; and third, amplification in the polar night jet. Stationary gravity waves were detected in all atmospheric layers up to the mesosphere with horizontal wavelengths between 20 and 100 km. The complete coverage of our data set from troposphere to mesosphere proved to be valuable to identify the processes involved in deep gravity wave propagation.

  6. Atom Interferometry for detection of Gravity Waves-a

    Data.gov (United States)

    National Aeronautics and Space Administration — Atom interferometers are more sensitive to inertial effects. This is because atoms in their inertial frame are ideal test masses for detection of gravity effects and...

  7. Persistent gravity wave coupling from the stratosphere to the MLT versus secondary wave generation in Antarctica

    Science.gov (United States)

    Zhao, J.; Geraghty, I.; Chu, X.; Vadas, S.; Becker, E.; Harvey, V. L.; Jones, R. M.; Chen, C.; Lu, X.

    2017-12-01

    After Antarctic persistent gravity waves (GWs) in the Mesosphere and Lower Thermosphere (MLT) were discovered from lidar observations [Chen et al., 2013, 2016], secondary wave generation theory was proposed to explain the source. Here we perform a source investigation of such persistent GWs through analyzing both stratospheric and MLT GWs at McMurdo using temperature measurements (30 - 50 km, year 2011 - 2015) obtained by Fe Boltzmann lidar. In the stratosphere, GW vertical wavelengths (λ) and periods exhibit seasonal cycles with winter maxima and summer minima, which linearly correlated with mean zonal wind velocities. GWs dissipate more in winter than in summer due to larger wave amplitudes. The potential energy density (Ep) are anti-correlated with wind rotation angles but positively correlated with surface and stratospheric winds. Critical level filtering, in-situ generation of GWs, and wave saturation changes play roles in Ep seasonal variations (winter maxima and summer minima). The large increase of Ep from summer to winter possibly results from the decrease in critical level filtering. The gradual variations of Ep from Mar to Oct are likely related both to the increased λ towards winter, allowing larger wave amplitudes before saturation, and to in-situ GW generation via geostrophic adjustment, secondary GW generation. Large Ep occur when McMurdo is inside the jet stream core 5-24º poleward from vortex edge. In winter MLT, the persistent GWs cause larger temperature perturbations (± 30 K, compared to ± 10 K in the stratosphere) with longer λ (23.5 km) and larger vertical phase speeds (1.8 m/s). More waves (95.4%) show downward phase progression compared to the stratospheric GWs (70.4%). Since the inferred horizontal wavelength of stratospheric GWs (350 - 450 km) are much shorter than those of the persistent GWs in the MLT (1000 - 2000 km), the dominant stratospheric GWs are not the direct source of the MLT persistent GWs. Secondary wave generation

  8. Study of gravity waves propagation in the thermosphere of Mars based on MAVEN/NGIMS density measurements

    Science.gov (United States)

    Vals, M.

    2017-09-01

    We use MAVEN/NGIMS CO2 density measurements to analyse gravity waves in the thermosphere of Mars. In particular the seasonal/latitudinal variability of their amplitude is studied and interpreted. Key background parameters controlling the activity of gravity waves are analysed with the help of the Mars Climate Database (MCD). Gravity waves activity presents a good anti-correlation to the temperature variability retrieved from the MCD. An analysis at pressure levels is ongoing.

  9. Influence of internal waves on the dispersion and transport of inclined gravity currents

    Science.gov (United States)

    Hogg, C. A. R.; Pietrasz, V. B.; Ouellette, N. T.; Koseff, J. R.

    2016-02-01

    Brine discharge from desalination facilities presents environmental risks, particularly to benthic organisms. High concentrations of salt and chemical additives, which can be toxic to local ecosystems, are typically mitigated by dilution close to the source. Our laboratory experiments investigate how breaking internal tides can help to dilute gravity currents caused by desalination effluents and direct them away from the benthic layer. In laboratory experiments, internal waves at the pycnocline of an ambient stratification were directed towards a sloping shelf, down which ran a gravity current. The breaking internal waves were seen to increase the proportion of the fluid from the gravity current diverted away from the slope into an intrusion along the pycnocline. In a parametric study, increasing the amplitude of the internal wave was seen to increase the amount of dense fluid in the pycnocline intrusion. The amplitude required to divert the gravity current into the intrusion compares well with an analytical theory that equates the incident energy in the internal wave to the potential energy required to dilute the gravity current. These experimental results suggest that sites of breaking internal waves may be good sites for effluent disposal. Effluent diverted into the intrusion avoids the ecologically sensitive benthic layer.

  10. Gravity Waves and Wind-Farm Efficiency in Neutral and Stable Conditions

    Science.gov (United States)

    Allaerts, Dries; Meyers, Johan

    2018-02-01

    We use large-eddy simulations (LES) to investigate the impact of stable stratification on gravity-wave excitation and energy extraction in a large wind farm. To this end, the development of an equilibrium conventionally neutral boundary layer into a stable boundary layer over a period of 8 h is considered, using two different cooling rates. We find that turbulence decay has considerable influence on the energy extraction at the beginning of the boundary-layer transition, but afterwards, energy extraction is dominated by geometrical and jet effects induced by an inertial oscillation. It is further shown that the inertial oscillation enhances gravity-wave excitation. By comparing LES results with a simple one-dimensional model, we show that this is related to an interplay between wind-farm drag, variations in the Froude number and the dispersive effects of vertically-propagating gravity waves. We further find that the pressure gradients induced by gravity waves lead to significant upstream flow deceleration, reducing the average turbine output compared to a turbine in isolated operation. This leads us to the definition of a non-local wind-farm efficiency, next to a more standard wind-farm wake efficiency, and we show that both can be of the same order of magnitude. Finally, an energy flux analysis is performed to further elucidate the effect of gravity waves on the flow in the wind farm.

  11. Seasonal variations in gravity wave activity at three locations in Brazil

    Science.gov (United States)

    Clemesha, B. R.; Batista, P. P.; Buriti da Costa, R. A.; Schuch, N.

    2009-03-01

    Using the variance in meteor radar winds as a measure of gravity wave activity, we investigate the temporal variations in gravity waves at three locations in Brazil: São João do Cariri (7.3° S, 36.4° W), Cachoeira Paulista (22.7° S, 45.0° W) and Santa Maria (29.7° S, 53.7° W). The technique used is that of Hocking (2005) which makes it possible to separate the zonal and meridional components of the fluctuating wind velocity. We find that the seasonal variation of the fluctuating wind is similar to that of the amplitude of the diurnal tide, showing a predominantly semi-annual variation, stronger at Cachoeira Paulista and Santa Maria than at the quasi-equatorial station, Cariri. Both with respect to the seasonal trend and shorter term variations, strong coupling between gravity wave activity and tides is indicated by a remarkably close correlation between the fluctuating velocity and the vertical shear in the tidal winds. It is not clear as to whether this is caused by gravity wave forcing of the tides or whether it results from in situ generation of gravity waves by tidal wind shear.

  12. Seasonal variations in gravity wave activity at three locations in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Clemesha, B.R.; Batista, P.P. [Instituto Nacional de Pesquisas Espaciais Sao Jose dos Campos, SP (Brazil); Buriti da Costa, R.A. [Universidade Federal de Campina Grande, Campina Grande, PB (Brazil); Schuch, N. [Centro Regional Sul de Pesquisas Espaciais-INPE, Santa Maria, RS (Brazil)

    2009-07-01

    Using the variance in meteor radar winds as a measure of gravity wave activity, we investigate the temporal variations in gravity waves at three locations in Brazil: Sao Joao do Cariri (7.3 S,36.4 W), Cachoeira Paulista (22.7 S,45.0 W) and Santa Maria (29.7 S,53.7 W). The technique used is that of Hocking (2005) which makes it possible to separate the zonal and meridional components of the fluctuating wind velocity. We find that the seasonal variation of the fluctuating wind is similar to that of the amplitude of the diurnal tide, showing a predominantly semi-annual variation, stronger at Cachoeira Paulista and Santa Maria than at the quasi-equatorial station, Cariri. Both with respect to the seasonal trend and shorter term variations, strong coupling between gravity wave activity and tides is indicated by a remarkably close correlation between the fluctuating velocity and the vertical shear in the tidal winds. It is not clear as to whether this is caused by gravity wave forcing of the tides or whether it results from in situ generation of gravity waves by tidal wind shear. (orig.)

  13. Improved analysis of all-sky meteor radar measurements of gravity wave variances and momentum fluxes

    Directory of Open Access Journals (Sweden)

    V. F. Andrioli

    2013-05-01

    Full Text Available The advantages of using a composite day analysis for all-sky interferometric meteor radars when measuring mean winds and tides are widely known. On the other hand, problems arise if this technique is applied to Hocking's (2005 gravity wave analysis for all-sky meteor radars. In this paper we describe how a simple change in the procedure makes it possible to use a composite day in Hocking's analysis. Also, we explain how a modified composite day can be constructed to test its ability to measure gravity wave momentum fluxes. Test results for specified mean, tidal, and gravity wave fields, including tidal amplitudes and gravity wave momentum fluxes varying strongly with altitude and/or time, suggest that the modified composite day allows characterization of monthly mean profiles of the gravity wave momentum fluxes, with good accuracy at least at the altitudes where the meteor counts are large (from 89 to 92.5 km. In the present work we also show that the variances measured with Hocking's method are often contaminated by the tidal fields and suggest a method of empirical correction derived from a simple simulation model. The results presented here greatly increase our confidence because they show that our technique is able to remove the tide-induced false variances from Hocking's analysis.

  14. Seasonal variations in gravity wave activity at three locations in Brazil

    Directory of Open Access Journals (Sweden)

    B. R. Clemesha

    2009-03-01

    Full Text Available Using the variance in meteor radar winds as a measure of gravity wave activity, we investigate the temporal variations in gravity waves at three locations in Brazil: São João do Cariri (7.3° S, 36.4° W, Cachoeira Paulista (22.7° S, 45.0° W and Santa Maria (29.7° S, 53.7° W. The technique used is that of Hocking (2005 which makes it possible to separate the zonal and meridional components of the fluctuating wind velocity. We find that the seasonal variation of the fluctuating wind is similar to that of the amplitude of the diurnal tide, showing a predominantly semi-annual variation, stronger at Cachoeira Paulista and Santa Maria than at the quasi-equatorial station, Cariri. Both with respect to the seasonal trend and shorter term variations, strong coupling between gravity wave activity and tides is indicated by a remarkably close correlation between the fluctuating velocity and the vertical shear in the tidal winds. It is not clear as to whether this is caused by gravity wave forcing of the tides or whether it results from in situ generation of gravity waves by tidal wind shear.

  15. Behavior of flexural gravity waves on ice shelves: Application to the Ross Ice Shelf

    Science.gov (United States)

    Sergienko, O. V.

    2017-08-01

    Ocean waves continuously impact floating ice shelves and affect their stress regime. Low-frequency, long-period (75-400 s), ocean waves are able to reach ice-shelf cavities from distant sources and excite flexural gravity waves that represent coupled motion in the water of the cavity and the ice covering above. Analytic treatment of simplified geometric configuration and three-dimensional numerical simulations of these flexural gravity waves applied to the Ross Ice Shelf show that propagation and ice-shelf flexural stresses are strongly controlled by the geometry of the system, bathymetry of the ice-shelf cavity, and ice-shelf cavity thickness. The derived dispersion relationships, group and phase velocities of these waves can be used to infer poorly constrained characteristics of ice shelves from field observations. The results of numerical simulations show that the flexural gravity waves propagate as beams. The orientation of these beams is determined by the direction of the open ocean waves incident on the ice-shelf front. The higher frequency ocean waves cause larger flexural stresses, while lower frequency waves can propagate farther away from the ice-shelf front and cause flexural stresses in the vicinity of the grounding line.

  16. Improving GOMOS High Resolution Temperature validation by discriminating atmospheric gravity waves

    Science.gov (United States)

    Quirino Iannone, Rosario; Casadio, Stefano; Saavedra de Miguel, Lidia; De Laurentis, Marta; Brizzi, Gabriele; Dehn, Angelika

    2013-04-01

    Atmospheric gravity waves play an important role in the thermodynamic processes of the atmosphere. The gravity waves, once generated in the upper troposphere and lower stratosphere, propagate upward and deposit their energy and momentum when dissipating. These atmospheric waves can cause strong fluctuations in the thermal structure of the middle and upper atmosphere. The satellite temperature retrievals, together with innovative analysis methods, are often used to provide constraints for model parameterization, which can improve the treatment of these phenomena in climate-prediction models, as the temperature profiles are expected to present wave-like structures due to the global distribution of the gravity-wave momentum flux. The analysis of temperature variability as a function of spatial and temporal separation indicates that gravity wave activity has impacts also on validation study site selection. The aim of this study is to analyse the characteristics of the atmospheric gravity waves detectable in the GOMOS (Global Ozone Monitoring by Occultation of Stars) High Resolution Temperature Profiles (HRTP). These are collected over altitudes ranging from 18 to 35 km, in the 2002 to 2012 time period. The GOMOS instrument is a medium-resolution star-occultation spectrometer operating in the ultraviolet-visible-near-infrared (UV-VIS-NIR) spectral range, onboard of the ESA/ENVISAT platform. The HRTP products are the result of the analysis of the two fast photometer measurements, and the retrieval is based on a GPS-like inversion scheme (Kyrola et al., 2010). Following our new approach, based on the use of the "Morlet" wavelet transform (Torrence and Compo, 1998), it is possible to capture the vertical amplitude and phase of waves of very different size along the temperature profile. The wavy signal is estimated and subtracted to the original profile, thus providing a "wave-free" profile. Comparison of wave-free temperature profiles and gravity wave structures with those

  17. The Effect of the Leeuwin Current on Offshore Surface Gravity Waves in Southwest Western Australia

    Science.gov (United States)

    Wandres, Moritz; Wijeratne, E. M. S.; Cosoli, Simone; Pattiaratchi, Charitha

    2017-11-01

    The knowledge of regional wave regimes is critical for coastal zone planning, protection, and management. In this study, the influence of the offshore current regime on surface gravity waves on the southwest Western Australian (SWWA) continental shelf was examined. This was achieved by coupling the three dimensional, free surface, terrain-following hydrodynamic Regional Ocean Modelling System (ROMS) and the third generation wave model Simulating WAves Nearshore (SWAN) using the Coupled Ocean-Atmosphere-WaveSediment Transport (COAWST) model. Different representative states of the Leeuwin Current (LC), a strong pole-ward flowing boundary current with a persistent eddy field along the SWWA shelf edge were simulated and used to investigate their influence on different large wave events. The coupled wave-current simulations were compared to wave only simulations, which represented scenarios in the absence of a background current field. Results showed that the LC and the eddy field significantly impact SWWA waves. Significant wave heights increased (decreased) when currents were opposing (aligning with) the incoming wave directions. During a fully developed LC system significant wave heights were altered by up to ±25% and wave directions by up to ±20°. The change in wave direction indicates that the LC may modify nearshore wave dynamics and consequently alter sediment patterns. Operational regional wave forecasts and hindcasts may give flawed predictions if wave-current interaction is not properly accounted for.

  18. The Role of Gravity Waves in the Formation and Organization of Clouds during TWPICE

    Energy Technology Data Exchange (ETDEWEB)

    Reeder, Michael J. [Monash University; Lane, Todd P. [University of Melbourne; Hankinson, Mai Chi Nguyen [Monash University

    2013-09-27

    All convective clouds emit gravity waves. While it is certain that convectively-generated waves play important parts in determining the climate, their precise roles remain uncertain and their effects are not (generally) represented in climate models. The work described here focuses mostly on observations and modeling of convectively-generated gravity waves, using the intensive observations from the DoE-sponsored Tropical Warm Pool International Cloud Experiment (TWP-ICE), which took place in Darwin, from 17 January to 13 February 2006. Among other things, the research has implications the part played by convectively-generated gravity waves in the formation of cirrus, in the initiation and organization of further convection, and in the subgrid-scale momentum transport and associated large-scale stresses imposed on the troposphere and stratosphere. The analysis shows two groups of inertia-gravity waves are detected: group L in the middle stratosphere during the suppressed monsoon period, and group S in the lower stratosphere during the monsoon break period. Waves belonging to group L propagate to the south-east with a mean intrinsic period of 35 h, and have vertical and horizontal wavelengths of about 5-6 km and 3000-6000 km, respectively. Ray tracing calculations indicate that these waves originate from a deep convective region near Indonesia. Waves belonging to group S propagate to the south-south-east with an intrinsic period, vertical wavelength and horizontal wavelength of about 45 h, 2 km and 2000-4000 km, respectively. These waves are shown to be associated with shallow convection in the oceanic area within about 1000 km of Darwin. The intrinsic periods of high-frequency waves are estimated to be between 20-40 minutes. The high-frequency wave activity in the stratosphere, defined by mass-weighted variance of the vertical motion of the sonde, has a maximum following the afternoon local convection indicating that these waves are generated by local convection

  19. Stoneley waves in a non-homogeneous orthotropic granular medium under the influence of gravity

    Directory of Open Access Journals (Sweden)

    S. M. Ahmed

    2005-01-01

    Full Text Available The aim of this paper is to investigate the Stoneley waves in a non-homogeneous orthotropic granular medium under the influence of a gravity field. The frequency equation obtained, in the form of a sixth-order determinantal expression, is in agreement with the corresponding result when both media are elastic. The frequency equation when the gravity field is neglected has been deduced as a particular case.

  20. Effects of gravity and planetary waves on the lower ionosphere as obtained from radio wave absorption measurements

    Czech Academy of Sciences Publication Activity Database

    Laštovička, Jan

    2001-01-01

    Roč. 26, 6, Part C (2001), s. 381-386 ISSN 1464-1917 R&D Projects: GA AV ČR IBS3012007; GA AV ČR IAA3042102; GA MŠk OC 271.10 Institutional research plan: CEZ:AV0Z3042911 Keywords : planetary wave * gravity wave * lower ionosphere Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.399, year: 2001

  1. The Atmospheric Waves Experiment (AWE): Quantifying the Impact of Gravity Waves on the Edge of Space

    Science.gov (United States)

    Taylor, M. J.; Forbes, J. M.; Fritts, D. C.; Eckermann, S. D.; Snively, J. B.; Liu, H.; Janches, D.; Syrstad, E. A.; Esplin, R. W.; Pautet, P. D.; Zhao, Y.; Pendleton, W. R.

    2017-12-01

    New theory and modeling now indicate that upward-propagating gravity waves (GWs) originating in the lower atmosphere have profound effects on the variability and mean state of the ionosphere-thermosphere-mesosphere (ITM) system. A major unknown is the spectrum of small-scale ( 30-300 km) GWs entering this system from below. Yet, this part of the spectrum contains most of the waves that will produce the greatest ITM effects. To address this knowledge gap, the Atmospheric Waves Experiment (AWE) plans to deploy a high-resolution imager (based on the successful Utah State University Advanced Mesospheric Temperature Mapper) on the International Space Station (ISS) to gain a transformative set of GW-resolving temperature measurements using the OH nightglow emission (altitude 87 km). The ISS provides the ideal combination of altitude, geographic and local time coverage to accomplish our proposed science objectives, which seeks not only near-global measurements of GW characteristics in the mesopause region, but also quantification of GW momentum and energy fluxes driving the IT from below. Combined with state-of-the-art high-resolution models, the AWE mission will also assess the relative importance of sources versus propagation conditions in explaining the observed spatial and temporal variability of the GWs. The AWE mission was recently selected for a "Phase A" study as part of the NASA 2016 Heliophysics Explorers Mission of Opportunity (MO) Program. In this presentation, we describe the primary goals of this program and introduce our proposed research methods using proven IR instrument technology. AWE's exceptional capabilities are illustrated with recent discoveries in observing GWs from the ground and from aircraft during the NSF DEEPWAVE campaign, promising a major step forward in understanding how troposphere weather translates to space weather.

  2. Investigating Gravity Waves in Polar Mesospheric Clouds Using Tomographic Reconstructions of AIM Satellite Imagery

    Science.gov (United States)

    Hart, V. P.; Taylor, M. J.; Doyle, T. E.; Zhao, Y.; Pautet, P.-D.; Carruth, B. L.; Rusch, D. W.; Russell, J. M.

    2018-01-01

    This research presents the first application of tomographic techniques for investigating gravity wave structures in polar mesospheric clouds (PMCs) imaged by the Cloud Imaging and Particle Size instrument on the NASA AIM satellite. Albedo data comprising consecutive PMC scenes were used to tomographically reconstruct a 3-D layer using the Partially Constrained Algebraic Reconstruction Technique algorithm and a previously developed "fanning" technique. For this pilot study, a large region (760 × 148 km) of the PMC layer (altitude 83 km) was sampled with a 2 km horizontal resolution, and an intensity weighted centroid technique was developed to create novel 2-D surface maps, characterizing the individual gravity waves as well as their altitude variability. Spectral analysis of seven selected wave events observed during the Northern Hemisphere 2007 PMC season exhibited dominant horizontal wavelengths of 60-90 km, consistent with previous studies. These tomographic analyses have enabled a broad range of new investigations. For example, a clear spatial anticorrelation was observed between the PMC albedo and wave-induced altitude changes, with higher-albedo structures aligning well with wave troughs, while low-intensity regions aligned with wave crests. This result appears to be consistent with current theories of PMC development in the mesopause region. This new tomographic imaging technique also provides valuable wave amplitude information enabling further mesospheric gravity wave investigations, including quantitative analysis of their hemispheric and interannual characteristics and variations.

  3. Does strong tropospheric forcing cause large amplitude mesospheric gravity waves? A Deepwave Case Study

    Science.gov (United States)

    Bramberger, Martina; Dörnbrack, Andreas; Ehard, Benedikt; Kaifler, Bernd; Kaifler, Natalie; Rahm, Stephan; Witschas, Benjamin; Rapp, Markus; Vosper, Simon; Orr, Andrew; Williams, Bifford P.; Fritts, David C.; Pautet, P.-Dominique; Taylor, Michael J.; Mallaun, Christian

    2017-04-01

    On 4 July 2014, during the Deep Propagating Gravity Wave Experiment (DEEPWAVE), strong horizontal winds up to 35 ms-1 caused the excitation of gravity waves containing the largest energy fluxes of the complete campaign (38 W m-2). At the same time, large amplitude mesospheric gravity waves were detected by the Temperature Lidar for Middle Atmospheric Research (TELMA) located in Lauder (45.0° S, 169.7° E). This combination lead to the question whether the observed mesospheric gravity waves are generated by the tropospheric forcing. For our study we use an extensive data set which comprises TELMA data, in situ measurements of the two aircraft, radiosondes, wind lidar measurements aboard DLR Falcon as well as Rayleigh lidar and advanced mesospheric temperature mapper (AMTM) measurements aboard the NSF/NCAR GV. To complement the measurements, studies with limited area simulations of the Unified Model are taken into account. This unique data set allows for the observation of the evolution of the gravity waves from the troposphere to the mesosphere. Our investigations revealed a complicated situation where the propagation of mountain waves is influenced by partial reflection at the tropopause, a valve layer in the lower stratosphere filtering a part of the wave spectrum and possibly partial reflection at the polar night jet. Nevertheless stationary waves are found in the AMTM measurements with horizontal wavelengths between 30 and 130 km. Although the measurements comprised all altitudes from the troposphere to the mesosphere, still numerical studies proved to be a valuable asset in order to answer the question raised.

  4. Analysis and modeling of ducted and evanescent gravity waves observed in the Hawaiian airglow

    Directory of Open Access Journals (Sweden)

    D. B. Simkhada

    2009-08-01

    Full Text Available Short-period gravity waves of especially-small horizontal scale have been observed in the Maui, Hawaii airglow. Typical small-scale gravity wave events have been investigated, and intrinsic wave propagation characteristics have been calculated from simultaneous meteor radar wind measurements. Here we report specific cases where wave structure is significantly determined by the local wind structure, and where wave characteristics are consistent with ducted or evanescent waves throughout the mesopause region. Two of the documented events, exhibiting similar airglow signatures but dramatically different propagation conditions, are selected for simple numerical modeling case studies. First, a Doppler-ducted wave trapped within relatively weak wind flow is examined. Model results confirm that the wave is propagating in the 85–95 km region, trapped weakly by evanescence above and below. Second, an evanescent wave in strong wind flow is examined. Model results suggest an opposite case from the first case study, where the wave is instead trapped above or below the mesopause region, with strong evanescence arising in the 85–95 km airglow region. Distinct differences between the characteristics of these visibly-similar wave events demonstrate the need for simultaneous observations of mesopause winds to properly assess local propagation conditions.

  5. Atmospheric gravity wave detection following the 2011 Tohoku earthquakes combining COSMIC occultation and GPS observations

    Science.gov (United States)

    Yan, X.; Tao, Y.; Xia, C.; Qi, Y.; Zuo, X.

    2017-12-01

    Several studies have reported the earthquake-induced atmospheric gravity waves detected by some new technologies such as airglow (Makela et al., 2011), GOCE (Garcia et al., 2013), GRACE (Yang et al., 2014), F3/C radio occultation sounding (Coïsson et al., 2015). In this work, we collected all occultation events on 11 March, and selected four events to analyze at last. The original and filtered podTEC is represented as function of the altitude of the impact parameter and UT of the four events. Then, the travel time diagrams of filtered podTEC derived from the events were analyzed. The occultation signal from one event (marked as No.73) is consistent with the previous results reported by Coïsson. 2015, which is corresponds to the ionospheric signal induced from tsunami gravity wave. What is noticeable, in this work, is that three occultation events of No.403, 77 and 118 revealed a disturbance of atmospheric gravity wave with velocity 300m/s, preceding the tsunami. It would probably be correspond to the gravity waves caused by seismic rupture but not tsunami. In addition, it can be seen that the perturbation height of occultation observation TEC is concentrated at 200-400km, corresponding ionosphere F region. The signals detected above are compared with GPS measurements of TEC from GEONET and IGS. From GPS data, traveling ionospheric disturbances were observed spreading out from the epicenter as a quasi-circular propagation pattern with the time. Exactly, we observed an acoustic wave coupled with Rayleigh wave starting from the epicenter with a speed of 3.0km/s and a superimposed acoustic-gravity wave moving with a speed of 800m/s. The acoustic-gravity wave generated at the epicenter and gradually attenuated 800km away, then it is replaced by a gravity wave coupled with the tsunami that moves with a speed of between 100 and 300m/s. It is necessary to confirm the propagation process of the waves if we attempt to evaluate the use of ionospheric seismology as a

  6. Gravity Waves Activity in Tropical and Equatorial Africa: Climatology and Sources (abstract)

    Science.gov (United States)

    Kafando, P.; Chane-Ming, F.; Petitdidier, M.

    2009-04-01

    Gravity wave activity is studied with six years radio sounding data from some of the African meteorological stations located in the 18° N and 05° S latitude domains. This study focuses on gravity wave parameters (e.g., total energy, kinetic and potential energies, fraction of upward propagating energy) above Bamako, Mali (12°53' N, 07°95' W). Climatology and seasonal variation are analyzed in the lower stratosphere and upper troposphere. Sources and variability are also examined in relation to convection indices and monsoons.

  7. Tidal and gravity waves study from the airglow measurements at ...

    Indian Academy of Sciences (India)

    E) during the period 2004–2007 are analyzed to study the dominant waves present in the 80–100 km altitude region of the atmosphere. The nocturnal intensity variations of different airglow emissions are observed using scanning temperature controlled filter photometers. Waves having period lying between 2 and 12 hours ...

  8. Tidal and gravity waves study from the airglow measurements at ...

    Indian Academy of Sciences (India)

    downward phase propagation both for the first and the second harmonics. In normal condition, down- ward wave propagation is not tenable. Such propa- gation in localized region may be observed due to the strong wind effect or the influence of multi- wave mode coupling. Analysing OI and OH emis- sion data, Fagundes et ...

  9. Geometric controls of the flexural gravity waves on the Ross Ice Shelf

    Science.gov (United States)

    Sergienko, O. V.

    2017-12-01

    Long-period ocean waves, formed locally or at distant sources, can reach sub-ice-shelf cavities and excite coupled motion in the cavity and the ice shelf - flexural gravity waves. Three-dimensional numerical simulations of the flexural gravity waves on the Ross Ice Shelf show that propagation of these waves is strongly controlled by the geometry of the system - the cavity shape, its water-column thickness and the ice-shelf thickness. The results of numerical simulations demonstrate that propagation of the waves is spatially organized in beams, whose orientation is determined by the direction of the of the open ocean waves incident on the ice-shelf front. As a result, depending on the beams orientation, parts of the Ross Ice Shelf experience significantly larger flexural stresses compared to other parts where the flexural gravity beams do not propagate. Very long-period waves can propagate farther away from the ice-shelf front exciting flexural stresses in the vicinity of the grounding line.

  10. On the Dynamics of Two-Dimensional Capillary-Gravity Solitary Waves with a Linear Shear Current

    Directory of Open Access Journals (Sweden)

    Dali Guo

    2014-01-01

    Full Text Available The numerical study of the dynamics of two-dimensional capillary-gravity solitary waves on a linear shear current is presented in this paper. The numerical method is based on the time-dependent conformal mapping. The stability of different kinds of solitary waves is considered. Both depression wave and large amplitude elevation wave are found to be stable, while small amplitude elevation wave is unstable to the small perturbation, and it finally evolves to be a depression wave with tails, which is similar to the irrotational capillary-gravity waves.

  11. Capillary-gravity waves and the Navier-Stokes equation

    International Nuclear Information System (INIS)

    Behroozi, F.; Podolefsky, N.

    2001-01-01

    Water waves are a source of great fascination for undergraduates and thus provide an excellent context for introducing some important topics in fluid dynamics. In this paper we introduce the potential theory for incompressible and inviscid flow and derive the differential equation that governs the behaviour of the velocity potential. Next we obtain the harmonic solutions of the velocity potential by a very general argument. These solutions in turn yield the equations for the velocity and displacement of a water element under the action of a harmonic wave. Finally we obtain the dispersion relation for surface waves by requiring that the harmonic solutions satisfy the Navier-Stokes equation. (author)

  12. Analytical and numerical investigation of nonlinear internal gravity waves

    Directory of Open Access Journals (Sweden)

    S. P. Kshevetskii

    2001-01-01

    Full Text Available The propagation of long, weakly nonlinear internal waves in a stratified gas is studied. Hydrodynamic equations for an ideal fluid with the perfect gas law describe the atmospheric gas behaviour. If we neglect the term Ͽ dw/dt (product of the density and vertical acceleration, we come to a so-called quasistatic model, while we name the full hydro-dynamic model as a nonquasistatic one. Both quasistatic and nonquasistatic models are used for wave simulation and the models are compared among themselves. It is shown that a smooth classical solution of a nonlinear quasistatic problem does not exist for all t because a gradient catastrophe of non-linear internal waves occurs. To overcome this difficulty, we search for the solution of the quasistatic problem in terms of a generalised function theory as a limit of special regularised equations containing some additional dissipation term when the dissipation factor vanishes. It is shown that such solutions of the quasistatic problem qualitatively differ from solutions of a nonquasistatic nature. It is explained by the fact that in a nonquasistatic model the vertical acceleration term plays the role of a regularizator with respect to a quasistatic model, while the solution qualitatively depends on the regularizator used. The numerical models are compared with some analytical results. Within the framework of the analytical model, any internal wave is described as a system of wave modes; each wave mode interacts with others due to equation non-linearity. In the principal order of a perturbation theory, each wave mode is described by some equation of a KdV type. The analytical model reveals that, in a nonquasistatic model, an internal wave should disintegrate into solitons. The time of wave disintegration into solitons, the scales and amount of solitons generated are important characteristics of the non-linear process; they are found with the help of analytical and numerical investigations. Satisfactory

  13. Asymptotic expansions for solitary gravity-capillary waves in two and three dimensions

    International Nuclear Information System (INIS)

    Ablowitz, M J; Haut, T S

    2010-01-01

    High-order asymptotic series are obtained for gravity-capillary solitary waves, where the first term in the series is the well-known sech 2 solution of the KdV equation. The asymptotic series is used, with nine terms included, to investigate the effects of surface tension on the height and energy of large amplitude waves, and waves close to the solitary version of Stokes' extreme wave. In particular, for surface tension below a critical value, the solitary wave with the maximum energy is obtained. For large surface tension, the series is also used to study the energy related to the solitary waves of depression. Energy considerations suggest that, for large enough surface tension, there are solitary waves that can get close to the fluid bottom. Comparisons are also made with recent experiments.

  14. Observations of height-dependent pressure-perturbation structure of a strong mesoscale gravity wave

    Science.gov (United States)

    Starr, David O'C.; Korb, C. L.; Schwemmer, Geary K.; Weng, Chi Y.

    1992-01-01

    Airborne observations using a downward-looking, dual-frequency, near-infrared, differential absorption lidar system provide the first measurements of the height-dependent pressure-perturbation field associated with a strong mesoscale gravity wave. A pressure-perturbation amplitude of 3.5 mb was measured within the lowest 1.6 km of the atmosphere over a 52-km flight line. Corresponding vertical displacements of 250-500 m were inferred from lidar-observed displacement of aerosol layers. Accounting for probable wave orientation, a horizontal wavelength of about 40 km was estimated. Satellite observations reveal wave structure of a comparable scale in concurrent cirrus cloud fields over an extended area. Smaller-scale waves were also observed. Local meteorological soundings are analyzed to confirm the existence of a suitable wave duct. Potential wave-generation mechanisms are examined and discussed. The large pressure-perturbation wave is attributed to rapid amplification or possible wave breaking of a gravity wave as it propagated offshore and interacted with a very stable marine boundary layer capped by a strong shear layer.

  15. Locating the Tohoku-Oki 2011 tsunami source using acoustic-gravity waves

    OpenAIRE

    Andriamiranto Raveloson; Rainer Kind; Xiaohui Yuan; L. Cerana

    2012-01-01

    The giant Tohoku-Oki earthquake of 11 March 2011 in offshore Japan did not only generate tsunami waves in the ocean but also infrasound (or acoustic-gravity) waves in the atmosphere. We indentified ultra-long-period signals (>500s) in the recordings of infrasound stations in northeast Asia, the northwest Pacific, and Alaska. Their source was fond close to the earthquake epicenter. Therefore, we conclude that in general, infrasound observations after a large offshore earthquake are evidence th...

  16. Convective cells of internal gravity waves in the earth's atmosphere with finite temperature gradient

    Directory of Open Access Journals (Sweden)

    O. Onishchenko

    2013-03-01

    Full Text Available In this paper, we have investigated vortex structures (e.g. convective cells of internal gravity waves (IGWs in the earth's atmosphere with a finite vertical temperature gradient. A closed system of nonlinear equations for these waves and the condition for existence of solitary convective cells are obtained. In the atmosphere layers where the temperature decreases with height, the presence of IGW convective cells is shown. The typical parameters of such structures in the earth's atmosphere are discussed.

  17. Horizontal velocities and propagation directions of gravity waves in the ionosphere over the Czech Republic

    Czech Academy of Sciences Publication Activity Database

    Chum, Jaroslav; Šindelářová, Tereza; Laštovička, Jan; Hruška, František; Burešová, Dalia; Baše, Jiří

    2010-01-01

    Roč. 115, - (2010), A11322/1-A11322/13 ISSN 0148-0227 R&D Projects: GA ČR GA205/07/1367; GA ČR GA205/09/1253 Grant - others:AV ČR(CZ) M100420901 Institutional research plan: CEZ:AV0Z30420517 Keywords : Ionosphere * gravity waves * wave propagation * remote sensing Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 3.303, year: 2010

  18. Acoustic–gravity waves during solar eclipses: Detection and characterization using wavelet transforms

    Czech Academy of Sciences Publication Activity Database

    Šauli, Petra; Roux, S. G.; Abry, P.; Boška, Josef

    2007-01-01

    Roč. 69, 17-18 (2007), s. 2465-2484 ISSN 1364-6826 R&D Projects: GA ČR GA205/06/1619; GA AV ČR IAA300420504 Grant - others:CNRS(FR) 18098 Institutional research plan: CEZ:AV0Z30420517 Keywords : Acoustic–gravity wave * Vertical ionospheric sounding * F-layer * Wavelet transform * Wave-packet characterization Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.566, year: 2007

  19. Effects of high-latitude atmospheric gravity wave disturbances on artificial HF radar backscatter

    OpenAIRE

    A. Senior; M. J. Kosch; T. K. Yeoman; M. T. Rietveld; I. W. McCrea

    2006-01-01

    International audience; Observations of HF radar backscatter from artificial field-aligned irregularities in an ionosphere perturbed by travelling disturbances due to atmospheric gravity waves are presented. Some features of the spatio-temporal structure of the artificial radar backscatter can be explained in terms of the distortion of the ionosphere resulting from the travelling disturbances. The distorted ionosphere can allow the HF pump wave to access upper-hybrid resonance at larger dista...

  20. Quantum spreading of a self-gravitating wave-packet in singularity free gravity

    Science.gov (United States)

    Buoninfante, Luca; Lambiase, Gaetano; Mazumdar, Anupam

    2018-01-01

    In this paper we will study for the first time how the wave-packet of a self-gravitating meso-scopic system spreads in theories beyond Einstein's general relativity. In particular, we will consider a ghost-free infinite derivative gravity, which resolves the 1 / r singularity in the potential - such that the gradient of the potential vanishes within the scale of non-locality. We will show that a quantum wave-packet spreads faster for a ghost-free and singularity-free gravity as compared to the Newtonian case, therefore providing us a unique scenario for testing classical and quantum properties of short-distance gravity in a laboratory in the near future.

  1. Cosmic Tsunamis in Modified Gravity: Disruption of Screening Mechanisms from Scalar Waves.

    Science.gov (United States)

    Hagala, R; Llinares, C; Mota, D F

    2017-03-10

    Extending general relativity by adding extra degrees of freedom is a popular approach for explaining the accelerated expansion of the Universe and to build high energy completions of the theory of gravity. The presence of such new degrees of freedom is, however, tightly constrained from several observations and experiments that aim to test general relativity in a wide range of scales. The viability of a given modified theory of gravity, therefore, strongly depends on the existence of a screening mechanism that suppresses the extra degrees of freedom. We perform simulations, and find that waves propagating in the new degrees of freedom can significantly impact the efficiency of some screening mechanisms, thereby threatening the viability of these modified gravity theories. Specifically, we show that the waves produced in the symmetron model can increase the amplitude of the fifth force and the parametrized post Newtonian parameters by several orders of magnitude.

  2. Observations of gravity waves of meteorological origin in the F-region

    Czech Academy of Sciences Publication Activity Database

    Boška, Josef; Šauli, Petra

    2001-01-01

    Roč. 26, č. 6 (2001), s. 425-428 ISSN 1464-1917 R&D Projects: GA ČR GA205/98/0058 Institutional research plan: CEZ:AV0Z3042911 Keywords : ionosphere * acoustic gravity waves * electron density profiles Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.399, year: 2001

  3. Evaluation of methods for gravity wave extraction from middle atmospheric lidar temperature measurements

    OpenAIRE

    Ehard, Benedikt; Kaifler, Bernd; Kaifler, Natalie; Rapp, Markus

    2015-01-01

    This study evaluates commonly used methods of extracting gravity wave induced temperature perturbations from lidar measurements. The spectral response of these methods is characterized with the help of a synthetic dataset with known temperature perturbations added to a realistic background temperature profile. The simulations are carried out with the background temperature being either constant or varying in time to evaluate the sensitivit...

  4. Mixing by internal gravity waves that break at sloping topography

    Science.gov (United States)

    Chalamalla, Vamsi; Sarkar, Sutanu

    2013-11-01

    Direct and large eddy simulations are performed to study the near-bottom mixing that occurs during the interaction of internal waves with a critical slope. The pathway from the input wave energy to the irreversible mixing of density field is explored. Diagnostics such as the turbulent kinetic energy budget and the density variance budget are discussed to explain the phasing of turbulence and associated mixing. Background and available potential energies are utilized to differentiate irreversible mixing from the reversible buoyancy flux. Mixing efficiency in all the simulated cases is found to be much higher than the frequently used value of 0.2 especially during large convective overturns. The ratio of Ozmidov and Thorpe length scales averaged over various sections of a wave cycle is investigated to assess inferences of turbulent dissipation rate from the Thorpe length scale.

  5. Design Optimization and Evaluation of Different Wind Generator Systems

    DEFF Research Database (Denmark)

    Chen, Zhe; Li, Hui

    2008-01-01

    With rapid development of wind power technologies and significant growth of wind power capacity installed worldwide, various wind generator systems have been developed and built. The objective of this paper is to evaluate various wind generator systems by optimization designs and comparisons...... and power electronic converter are presented; design optimizations of the investigated wind generator systems are developed with an improved genetic algorithm. Next, the optimization designs are implemented of various wind generator systems at 0.75-MW, 1.5-MW, 3.0-MW, 5.0-MWand 10MW, respectively....... In this paper, seven variable speed constant frequency (VSCF) wind generator systems are investigated, namely permanent magnet synchronous generators with the direct-driven (PMSG_DD), the single-stage gearbox (PMSG_1G) and three-stage gearbox (PMSG_3G) concepts, doubly fed induction generators with the three...

  6. On the spectrum of vertically propagating gravity waves generated by a transient heat source

    Directory of Open Access Journals (Sweden)

    M. J. Alexander

    2004-01-01

    Full Text Available It is commonly believed that cumulus convection preferentially generates gravity waves with tropospheric vertical wavelengths approximately twice the depth of the convective heating. Individual cumulonimbus, however, act as short term transient heat sources (duration 10 to 30min. Gravity waves generated by such sources have broad frequency spectra and a wide range of vertical scales. The high-frequency components tend to have vertical wavelengths much greater than twice the depth of the heating. Such waves have large vertical group velocities, and are only observed for a short duration and at short horizontal distances from the convective source. At longer times and longer distances from the source the dominant wave components have short vertical wavelengths and much slower group velocities, and thus are more likely to be observed even though their contribution to the momentum flux in the upper stratosphere and mesosphere may be less than that of the high frequency waves. These properties of convectively generated waves are illustrated by a linear numerical model for the wave response to a specified transient heat source. The wave characteristics are documented through Fourier and Wavelet analysis, and implications for observing systems are discussed.

  7. Analysis of Gravity Waves Structures Visible in Noctilucent Cloud Images

    Science.gov (United States)

    2010-01-01

    Instituto de Pesquisa e Desenvolvimento , Universidade do Vale do Paraíba, São José dos Campos SP, Brazil d Computational Physics Inc., Boulder, CO...mesopause region airglow emissions as markers of the waves (e.g., Taylor et al., 1997; Pautet et al., 2005; Nielsen et al., 2009). Since the NLC layer...94 95 96 The small-scale waves, termed ripples or billows, are short-lived (typically few tens of minutes) structures due to localized regions

  8. Unsteady motion of the parasitic capillary ripples on the gravity-capillary waves

    International Nuclear Information System (INIS)

    Seki, K.; Tsuji, Y.; Kukita, Y.

    2001-01-01

    Parasitic capillary ripples generated on the forward face of the gravity-capillary waves are investigated experimentally. Using the optical technique, the slope angle of the wave is measured with sufficient space and time resolution to characterize the small ripple fluctuations. The ripple generation and its steepness is considered from the point of dominant wave asymmetry. The unsteady motion of ripples is analyzed by the two-points optical measurements. Dominant wave has the same phase speed with ripple on average, however the relative distance to the dominant wave fluctuates which can't be negligible comparing with the ripple wavelength. That is, the non-linear interactions with the dominant wave assumed to be essential. (authors)

  9. Meteor Wind Radar Observations of Gravity Wave Momentum Fluxes at Middle and Lower Latitudes at Brazil

    Science.gov (United States)

    Fátima Andrioli, Vânia; Clemesha, Barclay; Prado Batista, Paulo; Schuch, Nelson Jorge; Buriti, Ricardo

    It is well known that the upward propagation of internal gravity waves from the lower atmo-sphere to the mesosphere plays an important role in the dynamics and energy balance of this region. Hocking (2005) developed a technique to calculate gravity wave momentum flux using meteor radar data. This technique is a generalization of the 2-beam technique of Vincent and Reid (1983). Hocking's technique uses radial velocity variances, from 80 to 100 km, which are mainly caused by gravity waves, to determine the gravity wave momentum fluxes. We apply this technique to data from a SKiMET meteor radar located at Santa Maria (29.7S, 53.7o W) during 2005. The data were analyzed in 3-km/2-h bins centered on 82, 85, 88 km etc. and 1, 3, 5 UT etc., generating monthly means. It was found that the meridional variances showed a fairly constant behavior throughout the year, with maximum at around 90 km. The zonal and vertical variances were less consistent. The monthly means of the horizontal momentum flux, uv, showed an oscillatory behavior with phase decreasing with increasing altitude and similar behavior was observed in the v'w' component. Although the behavior of u'w' was observed to be oscillatory, its phase did not show altitude propagation. In order to study the features of gravity wave activity in different latitude these results will be compared with two other radars located at São João do Cariri (7.3S, 36.4W) and Cachoeira Paulista (22.7S, 45.0W) for the a a same period.

  10. Simulation of acoustic-gravity waves from atmospheric pressure variations and their influence on the high atmosphere.

    Science.gov (United States)

    Kurdyaeva, Yuliya; Kshevetskii, Sergey; Gavrilov, Nikolay

    2017-04-01

    The processes of heating/cooling gas during phase transitions of water are one of the most important energy sources of acoustic-gravity waves in the atmosphere. Meteorological wave sources are very diverse and have complex, evolving spatial structure. The available experimental data are usually not enough for a detailed description of these wave sources. Therefore, modeling of acoustic-gravity waves from meteorological sources is challenging. The waves propagated from meteorological sources affect the atmospheric pressure. The atmospheric pressure variations with frequencies of acoustic-gravity wave spectrum are well recorded with microbarographs. It is interesting to use these experimental data, atmospheric pressure variations, for simulation of acoustic-gravity waves in the atmosphere. The hydrodynamic problem of propagation of acoustic-gravity waves from atmospheric pressure variations given on the Earth's surface is set and studied. It is shown that the solution of this boundary problem is completely determined by the pressure field. The numerical method for solving the problem is suggested. The program is tested by comparison of numerical simulations with known analytical solutions. The simulation of acoustic-gravity waves propagated from atmospheric pressure variation experimentally observed with microbarographs is performed. The effects of waves generated by atmospheric pressure variations in the atmosphere are investigated.

  11. Gravity induced corrections to quantum mechanical wave functions

    International Nuclear Information System (INIS)

    Singh, T.P.

    1990-03-01

    We perform a semiclassical expansion in the Wheeler-DeWitt equation, in powers of the gravitational constant. We then show that quantum gravitational fluctuations can provide a correction to the wave-functions which are solutions of the Schroedinger equation for matter. This also implies a correction to the expectation values of quantum mechanical observables. (author). 6 refs

  12. Integration of wind generation forecasts. Volume 2

    International Nuclear Information System (INIS)

    Ahlstrom, M.; Zavadil, B.; Jones, L.

    2005-01-01

    WindLogics is a company that specializes in atmospheric modelling, visualization and fine-scale forecasting systems for the wind power industry. A background of the organization was presented. The complexities of wind modelling were discussed. Issues concerning location and terrain, shear, diurnal and interannual variability were reviewed. It was suggested that wind power producers should aim to be mainstream, and that variability should be considered as intrinsic to fuel supply. Various utility operating impacts were outlined. Details of an Xcel NSP wind integration study were presented, as well as a studies conducted in New York state and Colorado. It was concluded that regulations and load following impacts with wind energy integration are modest. Overall impacts are dominated by costs incurred to accommodate wind generation variability and uncertainty in the day-ahead time frame. Cost impacts can be reduced with adjustments to operating strategies, improvements in wind forecasting and access to real-time markets. Details of WindLogic's wind energy forecast system were presented, as well as examples of day ahead and hour ahead forecasts and wind speed and power forecasts. Screenshots of control room integration, EMS integration and simulations were presented. Details of a utility-scale wind energy forecasting system funded by Xcel Renewable Development Fund (RDF) were also presented. The goal of the system was to optimize the way that wind forecast information is integrated into the control room environment. Project components were outlined. It was concluded that accurate day-ahead forecasting can lead to significant asset optimization. It was recommended that wind plants share data, and aim to resolve issues concerning grid codes and instrumentation. refs., tabs., figs

  13. Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    1998-10-01

    Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

  14. Validation of the CUTLASS HF radar gravity wave observing capability using EISCAT CP-1 data

    Directory of Open Access Journals (Sweden)

    N. F. Arnold

    Full Text Available Quasi-periodic fluctuations in the returned ground-scatter power from the SuperDARN HF radars have been linked to the passage of medium-scale gravity waves. We have applied a technique that extracts the first radar range returns from the F-region to study the spatial extent and characteristics of these waves in the CUTLASS field-of-view. Some ray tracing was carried out to test the applicability of this method. The EISCAT radar facility at Tromsø is well within the CUTLASS field-of-view for these waves and provides a unique opportunity to assess independently the ability of the HF radars to derive gravity wave information. Results from 1st March, 1995, where the EISCAT UHF radar was operating in its CP-1 mode, demonstrate that the radars were in good agreement, especially if one selects the electron density variations measured by EISCAT at around 235 km. CUTLASS and EISCAT gravity wave observations complement each other; the former extends the spatial field of view considerably, whilst the latter provides detailed vertical information about a range of ionospheric parameters.

    Key words. Ionosphere (ionosphere – atmosphere interactions · Meteorology and atmospheric dynamics (thermospheric dynamics · Radio science (ionospheric propagations

  15. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

    A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

  16. Thermal infrared sounding observations of lower atmospheric variances at Mars and their implications for gravity wave activity: a preliminary examination

    Science.gov (United States)

    Heavens, N. G.

    2017-12-01

    It has been recognized for over two decades that the mesoscale statistical variance observed by Earth-observing satellites at temperature-sensitive frequencies above the instrumental noise floor is a measure of gravity wave activity. These types of observation have been made by a variety of satellite instruments have been an important validation tool for gravity wave parameterizations in global and mesoscale models. At Mars, the importance of topographic and non-topographic sources of gravity waves for the general circulation is now widely recognized and the target of recent modeling efforts. However, despite several ingenious studies, gravity wave activity near hypothetical lower atmospheric sources has been poorly and unsystematically characterized, partly because of the difficulty of separating the gravity wave activity from baroclinic wave activity and the thermal tides. Here will be presented a preliminary analysis of calibrated radiance variance at 15.4 microns (635-665 cm-1) from nadir, off-nadir, and limb observations by the Mars Climate Sounder on board Mars Reconnaissance Orbiter. The overarching methodology follows Wu and Waters (1996, 1997). Nadir, off-nadir, and lowest detector limb observations should sample variability with vertical weighting functions centered high in the lower atmosphere (20-30 km altitude) and full width half maximum (FWHM) 20 km but be sensitive to gravity waves with different horizontal wavelengths and slightly different vertical wavelengths. This work is supported by NASA's Mars Data Analysis Program (NNX14AM32G). References Wu, D.L. and J.W. Waters, 1996, Satellite observations of atmospheric variances: A possible indication of gravity waves, GRL, 23, 3631-3634. Wu D.L. and J.W. Waters, 1997, Observations of Gravity Waves with the UARS Microwave Limb Sounder. In: Hamilton K. (eds) Gravity Wave Processes. NATO ASI Series (Series I: Environmental Change), vol 50. Springer, Berlin, Heidelberg.

  17. Gravity wave exclusion circles in background flows modulated by the semidiurnal tide

    Directory of Open Access Journals (Sweden)

    L. Zhong

    Full Text Available In this short paper the exclusion circles and vertical phase locities for gravity waves launched from the ground into a time-varying wind are studied using a ray-tracing technique. It is shown that waves with initial observed phase speeds that should place them within the local temporally varying exclusion circle, are often Doppler shifted outside of the circle. This, and the finite lifetime of some critical levels, allow waves to survive the critical layer and reach higher altitudes. Also, for slower phase-speed waves, the temporally varying wind can shift the observed frequency to negative values, so that the observed phase motions will be opposite (i.e. horizontally reversed and vertically upward, even though the energy still propagates upward. This effect can also cause the phase velocity to move inside the local exclusion circle. Due to the directional filtering of wave sources by the stratospheric wind, the percentage of such reverse-propagating waves will change systematically with local time and height in our simplified but realistic model. These results are related to ground-based systems, optical and radar, which sample the wind field and gravity waves in the middle atmosphere.

  18. Statistical analysis of thermospheric gravity waves from Fabry-Perot Interferometer measurements of atomic oxygen

    Directory of Open Access Journals (Sweden)

    E. A. K. Ford

    2008-02-01

    Full Text Available Data from the Fabry-Perot Interferometers at KEOPS (Sweden, Sodankylä (Finland, and Svalbard (Norway, have been analysed for gravity wave activity on all the clear nights from 2000 to 2006. A total of 249 nights were available from KEOPS, 133 from Sodankylä and 185 from the Svalbard FPI. A Lomb-Scargle analysis was performed on each of these nights to identify the periods of any wave activity during the night. Comparisons between many nights of data allow the general characteristics of the waves that are present in the high latitude upper thermosphere to be determined. Comparisons were made between the different parameters: the atomic oxygen intensities, the thermospheric winds and temperatures, and for each parameter the distribution of frequencies of the waves was determined. No dependence on the number of waves on geomagnetic activity levels, or position in the solar cycle, was found. All the FPIs have had different detectors at various times, producing different time resolutions of the data, so comparisons between the different years, and between data from different sites, showed how the time resolution determines which waves are observed. In addition to the cutoff due to the Nyquist frequency, poor resolution observations significantly reduce the number of short-period waves (<1 h period that may be detected with confidence. The length of the dataset, which is usually determined by the length of the night, was the main factor influencing the number of long period waves (>5 h detected. Comparisons between the number of gravity waves detected at KEOPS and Sodankylä over all the seasons showed a similar proportion of waves to the number of nights used for both sites, as expected since the two sites are at similar latitudes and therefore locations with respect to the auroral oval, confirming this as a likely source region. Svalbard showed fewer waves with short periods than KEOPS data for a season when both had the same time resolution data

  19. Gravity

    CERN Document Server

    Rivera, Andrea

    2017-01-01

    Gravity is all around us. Learn how it is used in art, technology, and engineering. Five easy-to-read chapters explain the science behind gravity, as well as its real-world applications. Vibrant, full-color photos, bolded glossary words, and a key stats section let readers zoom in even deeper. Aligned to Common Core Standards and correlated to state standards. Abdo Zoom is a division of ABDO.

  20. Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

    Directory of Open Access Journals (Sweden)

    Colin C. Triplett

    2017-01-01

    Full Text Available The meteorological control of gravity wave activity through filtering by winds and generation by spontaneous adjustment of unbalanced flows is investigated. This investigation is based on a new analysis of Rayleigh LiDAR measurements of gravity wave activity in the upper stratosphere-lower mesosphere (USLM,40–50kmon 152 nights at Poker Flat Research Range (PFRR, Chatanika, Alaska (65◦ N, 147◦ W, over 13 years between 1998 and 2014. The LiDAR measurements resolve inertia-gravity waves with observed periods between 1 h and 4 h and vertical wavelengths between 2 km and 10 km. The meteorological conditions are defined by reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA. The gravity wave activity shows large night-to-night variability, but a clear annual cycle with a maximum in winter,and systematic interannual variability associated with stratospheric sudden warming events. The USLM gravity wave activity is correlated with the MERRA winds and is controlled by the winds in the lower stratosphere through filtering by critical layer filtering. The USLM gravity wave activity is also correlated with MERRA unbalanced flow as characterized by the residual of the nonlinear balance equation. This correlation with unbalanced flow only appears when the wind conditions are taken into account, indicating that wind filtering is the primary control of the gravity wave activity.

  1. Observation of mesospheric gravity waves at Comandante Ferraz Antarctica Station (62° S

    Directory of Open Access Journals (Sweden)

    P. B. Souza

    2009-06-01

    Full Text Available An airglow all-sky imager was operated at Comandante Ferraz Antarctica Station (62.1° S, 58.4° W, between April and October of 2007. Mesospheric gravity waves were observed using the OH airglow layer during 43 nights with good weather conditions. The waves presented horizontal wavelengths between 10 and 60 km and observed periods mainly distributed between 5 and 20 min. The observed phase speeds range between 5 m/s and 115 m/s; the majority of the wave velocities were between 10 and 60 m/s. The waves showed a preferential propagation direction towards the southwest in winter (May to July, while during spring (August to October there was an anisotropy with a preferential propagation direction towards the northwest. Unusual mesospheric fronts were also observed. The most probable wave source could be associated to orographic forcing, cold fronts or strong cyclonic activity in the Antarctica Peninsula.

  2. Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation.

    Science.gov (United States)

    Tsuda, Toshitaka

    2014-01-01

    The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10-100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50-90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10-50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet.

  3. Chameleon fields, wave function collapse and quantum gravity

    International Nuclear Information System (INIS)

    Zanzi, A

    2015-01-01

    Chameleon fields are quantum (usually scalar) fields, with a density-dependent mass. In a high-density environment, the mass of the chameleon is large. On the contrary, in a small-density environment (e.g. on cosmological distances), the chameleon is very light. A model where the collapse of the wave function is induced by chameleon fields is presented. During this analysis, a Chameleonic Equivalence Principle (CEP) will be formulated: in this model, quantum gravitation is equivalent to a conformal anomaly. Further research efforts are necessary to verify whether this proposal is compatible with phenomeno logical constraints. (paper)

  4. GPS-TEC Observation of Gravity Waves Generated in the Ionosphere During 21 August 2017 Total Solar Eclipse

    Science.gov (United States)

    Nayak, Chinmaya; Yiǧit, Erdal

    2018-01-01

    The present work investigates ionospheric effects of the 21 August 2017 total solar eclipse, particularly targeting eclipse-generated gravity waves in the ionosphere. Ionospheric total electron content (TEC) derived from Global Positioning System (GPS) data obtained from a number of stations located both along and across the path of eclipse totality has been utilized for this purpose. Distinct gravity wave-like signatures with wave periods around 20-90 min (with dominant peak at 25-30 min wave period) have been observed at all locations both in the path of totality and away from it. The observed gravity waves are more intense at locations closer to the path of totality, and the wave amplitudes decrease gradually with increasing distance from the path of totality. Our result highlights the manifestation of eclipse-generated waves in the variability of the terrestrial ionosphere.

  5. The gravitational wave stress–energy (pseudo)-tensor in modified gravity

    Science.gov (United States)

    Saffer, Alexander; Yunes, Nicolás; Yagi, Kent

    2018-03-01

    The recent detections of gravitational waves by the advanced LIGO and Virgo detectors open up new tests of modified gravity theories in the strong-field and dynamical, extreme gravity regime. Such tests rely sensitively on the phase evolution of the gravitational waves, which is controlled by the energy–momentum carried by such waves out of the system. We here study four different methods for finding the gravitational wave stress–energy pseudo-tensor in gravity theories with any combination of scalar, vector, or tensor degrees of freedom. These methods rely on the second variation of the action under short-wavelength averaging, the second perturbation of the field equations in the short-wavelength approximation, the construction of an energy complex leading to a Landau–Lifshitz tensor, and the use of Noether’s theorem in field theories about a flat background. We apply these methods in general relativity, Jordan–Fierz–Brans–Dicky theoy, and Einstein-Æther theory to find the gravitational wave stress–energy pseudo-tensor and calculate the rate at which energy and linear momentum is carried away from the system. The stress–energy tensor and the rate of linear momentum loss in Einstein-Æther theory are presented here for the first time. We find that all methods yield the same rate of energy loss, although the stress–energy pseudo-tensor can be functionally different. We also find that the Noether method yields a stress–energy tensor that is not symmetric or gauge-invariant, and symmetrization via the Belinfante procedure does not fix these problems because this procedure relies on Lorentz invariance, which is spontaneously broken in Einstein-Æther theory. The methods and results found here will be useful for the calculation of predictions in modified gravity theories that can then be contrasted with observations.

  6. Stratospheric gravity wave activities inferred through the GPS radio occultation technique; Ondas de gravidade na estratosfera terrestre inferida atraves da tecnica de radio ocultacao de GPS

    Energy Technology Data Exchange (ETDEWEB)

    Wrasse, Cristiano Max [Universidade do Vale do Paraiba (UNIVAP), Instituto de Pesquisa e Desenvolvimento (IPeD), Sao Jose dos Campos, SP (Brazil); Takahashi, Hisao; Fechine, Joaquim; Denardini, Clezio Marcos [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil); Wickert, Jens, E-mail: cmw@univap.br, E-mail: hisaotak@laser.inpe.br, E-mail: joaquim@laser.inpe.br, E-mail: denardin@dae.inpe.br, E-mail: jens.wickert@gfz-potsdam.de [GeoForschungsZentrum, Potsdam (GFZ), Department of Geodesy and Remote Sensing (Germany)

    2007-07-01

    Stratospheric gravity wave activities were deduced from GPS radio occultation temperature profiles obtained by CHAMP satellite between 2001 and 2005. Potential energy profiles are used to analyze the gravity wave activity over South America. The results showed an inter-annual variation of the potential energy integrated between 24 and 34 km of altitude. The gravity wave activity is more concentrated around the equatorial region. In order to evaluate the seasonal variation of the gravity wave activity, a mean potential energy was determined over (10 deg N-10 deg S) and (100 deg W-20 deg W). The results showed a lower gravity wave activity during winter time, while during spring time the mean potential energy showed an increase in the wave activity. The results of the mean potential energy also showed that the gravity wave activity in the lower stratosphere exhibits a higher wave activity during 2002 and 2004 and a lower wave activity during 2003 and 2005. (author)

  7. Impacts of climate changes on ocean surface gravity waves over the eastern Canadian shelf

    Science.gov (United States)

    Guo, Lanli; Sheng, Jinyu

    2017-05-01

    A numerical study is conducted to investigate the impact of climate changes on ocean surface gravity waves over the eastern Canadian shelf (ECS). The "business-as-usual" climate scenario known as Representative Concentration Pathway RCP8.5 is considered in this study. Changes in the ocean surface gravity waves over the study region for the period 1979-2100 are examined based on 3 hourly ocean waves simulated by the third-generation ocean wave model known as WAVEWATCHIII. The wave model is driven by surface winds and ice conditions produced by the Canadian Regional Climate Model (CanRCM4). The whole study period is divided into the present (1979-2008), near future (2021-2050) and far future (2071-2100) periods to quantify possible future changes of ocean waves over the ECS. In comparison with the present ocean wave conditions, the time-mean significant wave heights ( H s ) are expected to increase over most of the ECS in the near future and decrease over this region in the far future period. The time-means of the annual 5% largest H s are projected to increase over the ECS in both near and far future periods due mainly to the changes in surface winds. The future changes in the time-means of the annual 5% largest H s and 10-m wind speeds are projected to be twice as strong as the changes in annual means. An analysis of inverse wave ages suggests that the occurrence of wind seas is projected to increase over the southern Labrador and central Newfoundland Shelves in the near future period, and occurrence of swells is projected to increase over other areas of the ECS in both the near and far future periods.

  8. Alternative methods of modeling wind generation using production costing models

    International Nuclear Information System (INIS)

    Milligan, M.R.; Pang, C.K.

    1996-08-01

    This paper examines the methods of incorporating wind generation in two production costing models: one is a load duration curve (LDC) based model and the other is a chronological-based model. These two models were used to evaluate the impacts of wind generation on two utility systems using actual collected wind data at two locations with high potential for wind generation. The results are sensitive to the selected wind data and the level of benefits of wind generation is sensitive to the load forecast. The total production cost over a year obtained by the chronological approach does not differ significantly from that of the LDC approach, though the chronological commitment of units is more realistic and more accurate. Chronological models provide the capability of answering important questions about wind resources which are difficult or impossible to address with LDC models

  9. Internal gravity waves in Titan's atmosphere observed by Voyager radio occultation

    Science.gov (United States)

    Hinson, D. P.; Tyler, G. L.

    1983-01-01

    The radio scintillations caused by scattering from small-scale irregularities in Titan's neutral atmosphere during a radio occultation of Voyager 1 by Titan are investigated. Intensity and frequency fluctuations occurred on time scales from about 0.1 to 1.0 sec at 3.6 and 13 cm wavelengths whenever the radio path passed within 90 km of the surface, indicating the presence of variations in refractivity on length scales from a few hundred meters to a few kilometers. Above 25 km, the altitude profile of intensity scintillations closely agrees with the predictions of a simple theory based on the characteristics of internal gravity waves propagating with little or no attenuation through the vertical stratification in Titan's atmosphere. These observations support a hypothesis of stratospheric gravity waves, possibly driven by a cloud-free convective region in the lowest few kilometers of the stratosphere.

  10. Long-Term Observation of Small and Medium-Scale Gravity Waves over the Brazilian Equatorial Region

    Science.gov (United States)

    Essien, Patrick; Buriti, Ricardo; Wrasse, Cristiano M.; Medeiros, Amauri; Paulino, Igo; Takahashi, Hisao; Campos, Jose Andre

    2016-07-01

    This paper reports the long term observations of small and medium-scale gravity waves over Brazilian equatorial region. Coordinated optical and radio measurements were made from OLAP at Sao Joao do Cariri (7.400S, 36.500W) to investigate the occurrences and properties and to characterize the regional mesospheric gravity wave field. All-sky imager measurements were made from the site. for almost 11 consecutive years (September 2000 to November 2010). Most of the waves propagated were characterized as small-scale gravity. The characteristics of the two waves events agreed well with previous gravity wave studies from Brazil and other sites. However, significant differences in the wave propagation headings indicate dissimilar source regions. The observed medium-scale gravity wave events constitute an important new dataset to study their mesospheric properties at equatorial latitudes. These data exhibited similar propagation headings to the short period events, suggesting they originated from the same source regions. It was also observed that some of the medium-scale were capable of propagating into the lower thermosphere where they may have acted directly as seeds for the Rayleigh-Taylor instability development. The wave events were primarily generated by meteorological processes since there was no correlation between the evolution of the wave events and solar cycle F10.7.

  11. Observation and a numerical study of gravity waves during tropical cyclone Ivan~(2008)

    OpenAIRE

    F. Chane Ming; C. Ibrahim; S. Jolivet; P. Keckhut; Y.-A. Liou; Y. Kuleshov

    2013-01-01

    Activity and spectral characteristics of gravity-waves (GWs) are analyzed during tropical cyclone (TC) Ivan (2008) in the troposphere and lower stratosphere using radiosonde and GPS radio occultation data, ECMWF outputs and simulations of French numerical model Meso-NH with vertical resolution varying between 150 m near the surface and 500 m in the lower stratosphere. Conventional methods for GW analysis and signal and image processing tools provide information on a wide spectrum of GW...

  12. Spontaneous development of rotating inertial gravity wave inside the cylindrical tank with combined in- and outflow

    Czech Academy of Sciences Publication Activity Database

    Fedorchenko, Alexander I.; Stachiv, Ivo; Trávníček, Zdeněk

    2013-01-01

    Roč. 20, č. 2 (2013), s. 133-138 ISSN 0869-8643 R&D Projects: GA ČR GAP107/10/0824; GA ČR(CZ) GCP101/11/J019 Institutional research plan: CEZ:AV0Z20760514 Keywords : inertial gravity wave * free surface * rotating flow Subject RIV: BK - Fluid Dynamics Impact factor: 0.295, year: 2013 http://link.springer.com/article/10.1134/S0869864313020017

  13. Destruction of coherence in nondemolition monitoring: quantum 'watchdog effect' in gravity wave detectors

    International Nuclear Information System (INIS)

    Zurek, W.H.

    1984-01-01

    The author shows that nondemolition monitoring of a Weber bar may prevent changes of the number of phonons, and thus influence the sensitivity of quantum-counting gravity wave detectors. This effect is similar to the Watchdog Effect which is predicted to delay decays of the monitored, unstable quantum system. Relations between watchdog effect and Environment-Induced Superselection Rules as well as its connections to the fundamental questions of the quantum theory of measurement are briefly considered. (Auth.)

  14. Second generation diffusion model of interacting gravity waves on the surface of deep fluid

    Directory of Open Access Journals (Sweden)

    A. Pushkarev

    2004-01-01

    Full Text Available We propose a second generation phenomenological model for nonlinear interaction of gravity waves on the surface of deep water. This model takes into account the effects of non-locality of the original Hasselmann diffusion equation still preserving important properties of the first generation model: physically consistent scaling, adherence to conservation laws and the existence of Kolmogorov-Zakharov solutions. Numerical comparison of both models with the original Hasselmann equation shows that the second generation models improves the angular distribution in the evolving wave energy spectrum.

  15. Massive, massless and ghost modes of gravitational waves from higher-order gravity

    DEFF Research Database (Denmark)

    Bogdanos, Charalampos; Capozziello, Salvatore; De Laurentis, Mariafelicia

    , we investigate the possible detectability of such additional polarization modes of a stochastic gravitational wave by ground-based and space interferometric detectors. Finally, we extend the formalism of the cross-correlation analysis, including the additional polarization modes, and calculate...... the detectable energy density of the spectrum for a stochastic background of the relic gravity waves that corresponds to our model. For the situation considered here, we find that these massive modes are certainly of interest for direct detection by the LISA experiment....

  16. Gravitational waves from quasicircular black-hole binaries in dynamical Chern-Simons gravity.

    Science.gov (United States)

    Yagi, Kent; Yunes, Nicolás; Tanaka, Takahiro

    2012-12-21

    Dynamical Chern-Simons gravity cannot be strongly constrained with current experiments because it reduces to general relativity in the weak-field limit. This theory, however, introduces modifications in the nonlinear, dynamical regime, and thus it could be greatly constrained with gravitational waves from the late inspiral of black-hole binaries. We complete the first self-consistent calculation of such gravitational waves in this theory. For favorable spin orientations, advanced ground-based detectors may improve existing solar system constraints by 6 orders of magnitude.

  17. Traveling neutral disturbances. [acoustic-gravity wave coupling to minor species in atmosphere

    Science.gov (United States)

    Gross, S. H.; Eun, H.

    1976-01-01

    The coupling of acoustic-gravity waves in the main atmosphere to acoustic waves characteristic of individual minor species in the atmosphere is postulated. Such coupling would exist as a result of resonances in the response of the minor species, and its likelihood depends on the mass of the atmospheric particle relative to the major species mass, the diffusion of the minor species, and the direction of propagation of the main disturbance. These minor-species disturbances may explain some AE-C measurements in the thermosphere and could possibly play a role in the distribution of minor species and their chemistry in the mesosphere.

  18. Kelvin-Helmholtz billows and their effects on mean state during gravity wave propagation

    Directory of Open Access Journals (Sweden)

    X. Liu

    2009-07-01

    Full Text Available The Kelvin-Helmholtz (KH billows which appear in the process of gravity wave (GW propagation are simulated directly by using a compressible nonlinear two-dimensional gravity wave model. The differences between our model and others include: the background field has no special initial configuration and there is no initial triggering mechanism needed in the mesosphere and lower thermosphere (MLT region to excite the KH billows. However, the initial triggering mechanism is performed in the lower atmosphere through GW, which then propagate into the MLT region and form billows. The braid structures and overturning of KH billows, caused by nonlinear interactions between GWs and mean flow, can be resolved precisely by the model. These results support the findings in airglow studies that GWs propagating from below into the MLT region are important sources of KH billows. The onset of small scale waves and the wave energy transfer induce the shallower vertical wave number power spectral densities (PSD. However, most of the slopes are steeper than the expected kz−3 power law, which indicates that GWs with 10 km vertical wavelength are still a dominant mode. The results also show that the evolution of mean wind vary substantially between the different processes of GWs propagation. Before the KH billows evolve, the mean wind is accelerated greatly by GWs. By contrast, as the KH billows evolve and mix with mean flow, the mean wind and its peak value decrease.

  19. Observations of up- and downward propagating gravity waves in the strato- and mesosphere.

    Science.gov (United States)

    Strelnikova, Irina; Baumgarten, Gerd; Lübken, Franz-Josef; Hildebrand, Jens; Höffner, Josef; Stober, Gunter

    2017-04-01

    Experimental and modeling efforts show that small-scale gravity waves (GW) essentially affect large-scale circulations, thermal states, and dynamics from the surface to the middle atmosphere. In climate modeling and weather-forecasting applications the gravity-wave drag and its interaction with large-scale dynamics are referred to as sub-gridscale, i.e. unresolved processes and are the most uncertain aspect of these models. Advances in lidar measurement techniques allow for experimental studies of GWs at very small spatial and temporal scales, which are not accessible by other means. The state of the art Doppler lidars and radars at the ALOMAR research station located in Northern Norway (69°N, 16°E) provide an observational database of GWs at the edge of the polar vortex connected to global dynamics of the Earth atmosphere. Doppler Rayleigh Iodine System (DoRIS) provides horizontal wind measurements in addition to the temperature observation. The altitude coverage is extended from 30 to 110 km by using the temperature observed by mobile Fe lidar with wind observations taken from meteor radar system. This give us unique possibility to obtain wave propagation direction, intrinsic frequency and horizontal wavelength from the single station. Making use of the advantage of this system, we derive wave parameters more precisely, and under some conditions we observe waves with downward propagating energy. In this paper we will present results of analyses of the GW observations by lidars and radars and discuss implications on atmospheric dynamics.

  20. Gravity wave spectra in the lower stratosphere diagnosed from project loon balloon trajectories

    Science.gov (United States)

    Schoeberl, M. R.; Jensen, E.; Podglajen, A.; Coy, L.; Lodha, C.; Candido, S.; Carver, R.

    2017-08-01

    Project Loon has been launching superpressure balloons since January 2013 to provide worldwide Internet coverage. These balloons typically fly between 18 and 21 km and provide measurements of winds and pressure fluctuations in the lower stratosphere. We divide 1560 Loon flights into 3405 two-day segments for gravity wave analysis. We derive the kinetic energy spectrum from the horizontal balloon motion and estimate the temperature perturbation spectrum (proportional to the potential energy spectrum) from the pressure variations. We fit the temperature (and kinetic energy) data to the functional form T'2 = T'o2[ω/ωο)α, where ω is the wave frequency, ωο is daily frequency, T'o is the base temperature amplitude, and α is the spectral slope. Both the kinetic energy and temperature spectra show -1.9 ± 0.2 power-law dependence in the intrinsic frequency window 3-50 cycles/day. The temperature spectrum slope is weakly anticorrelated with the base temperature amplitude. We also find that the wave base temperature distribution is highly skewed. The tropical modal temperature is 0.77 K. The highest amplitude waves occur over the mountainous regions, the tropics, and the high southern latitudes. Temperature amplitudes show little height variation over our 18-21 km domain. Our results are consistent with other limited superpressure balloon analyses. The modal temperature is higher than the temperature currently used in high-frequency gravity wave parameterizations.

  1. Acoustic Gravity Waves in the Ionosphere and Thermosphere During the 2017 Solar Eclipse

    Science.gov (United States)

    Lin, C. Y. T.; Deng, Y.

    2017-12-01

    During the 2017 solar eclipse, as the sudden cavity of solar radiation created by the lunar shadow moves across the United States on August 21, 2017, decreases in local IT temperature and density are expected. The average velocity of the total solar eclipse across the United States is 700 m/s. The forefront and wake of the lunar shadow are expected to induce acoustic gravity waves according to previous studies of atmosphere waves induced by traveling wave packets moving at different velocities. Meanwhile, moving toward the cross-track direction of the obscuration footprint, weaker transitions will likely create mesoscale to large-scale traveling disturbances. We will use the Global Ionosphere Thermosphere Model, a global circulation model solving for non-hydrostatic equations, with high-resolution settings to investigate the IT responses related to the acoustic-gravity wave perturbations during the 2017 solar eclipse. The simulation will be performed with a sub-degree resolution in longitude and latitude for 3 hours when the atmosphere of the North America sector is mostly obscured. The observable differences between the eclipsed and non-eclipsed scenarios will be examined in detail and be interpreted as consequences from the solar eclipse. We will investigate the evolution of waves during the event and establish a theoretical baseline for further comparisons with observations.

  2. QBO Modulation of the Mesopause Gravity Wave Momentum Flux over Tierra del Fuego

    Science.gov (United States)

    De Wit, R. J.; Janches, D.; Fritts, D. C.; Hibbins, R. E.

    2016-01-01

    The interannual variability of the mesosphere and lower thermosphere (MLT) gravity wave momentum flux over southern mid latitudes (53.7degS) has been studied using more than 7 years of meteor radar observations at Ro Grande, Argentina. A modulation, with periods similar to that of the equatorial stratospheric quasi-biennial oscillation (QBO), is observed in the vertical flux of zonal as well as meridional momentum. The QBO signal is largest in the zonal component during summer and is in phase with the stratospheric QBO at 50 hPa (approx. 21 km). The relation between the stratospheric QBO and the QBO modulation in the MLT gravity wave forcing (derived from the divergence of the momentum flux) was found to be consistent with that expected from the Holton-Tan effect coupled to the interhemispheric coupling mechanism. These results provide the first observational support for the existence of the midlatitude gravity wave forcing anomalies as hypothesized in the interhemispheric coupling mechanism.

  3. Influence of tides and gravity waves on layering processes in the polar summer mesopause region

    Directory of Open Access Journals (Sweden)

    P. Hoffmann

    2008-12-01

    Full Text Available Polar Mesosphere Summer Echoes (PMSE have been studied at Andenes (69° N, 16° E, Norway, using VHF radar observations since 1994. One remarkable feature of these observations is the fact that {during 50% of the time,} the radar echoes occur in the form of two or more distinct layers. In the case of multiple PMSE layers, statistical analysis shows that the lower layer occurs at a mean height of ~83.4 km, which is almost identical to the mean height of noctilucent clouds (NLC derived from observation with the ALOMAR Rayleigh/Mie/Raman lidar at the same site. To investigate the layering processes microphysical model simulations under the influence of tidal and gravity waves were performed. In the presence of long period gravity waves, these model investigations predict an enhanced formation of multiple PMSE layer structures, where the lower layer is a consequence of the occurrence of the largest particles at the bottom of the ice cloud. This explains the coincidence of the lowermost PMSE layers and NLC. During periods with enhanced amplitudes of the semidiurnal tide, the observed NLC and PMSE show pronounced tidal structures comparable to the results of corresponding microphysical simulations. At periods with short period gravity waves there is a tendency for a decreasing occurrence of NLC and for variable weak PMSE structures.

  4. Modeling Volcanic Eruption Parameters by Near-Source Internal Gravity Waves.

    Science.gov (United States)

    Ripepe, M; Barfucci, G; De Angelis, S; Delle Donne, D; Lacanna, G; Marchetti, E

    2016-11-10

    Volcanic explosions release large amounts of hot gas and ash into the atmosphere to form plumes rising several kilometers above eruptive vents, which can pose serious risk on human health and aviation also at several thousands of kilometers from the volcanic source. However the most sophisticate atmospheric models and eruptive plume dynamics require input parameters such as duration of the ejection phase and total mass erupted to constrain the quantity of ash dispersed in the atmosphere and to efficiently evaluate the related hazard. The sudden ejection of this large quantity of ash can perturb the equilibrium of the whole atmosphere triggering oscillations well below the frequencies of acoustic waves, down to much longer periods typical of gravity waves. We show that atmospheric gravity oscillations induced by volcanic eruptions and recorded by pressure sensors can be modeled as a compact source representing the rate of erupted volcanic mass. We demonstrate the feasibility of using gravity waves to derive eruption source parameters such as duration of the injection and total erupted mass with direct application in constraining plume and ash dispersal models.

  5. Observations of gravity waves associated with enhanced auroral activity: GPS, FPI and magnetometer measurements over Svalbard

    Science.gov (United States)

    Katamzi, Z. T.; Habarulema, J. B.; Aruliah, A. L.; Oksavik, K.

    2017-12-01

    Atmospheric gravity waves have been observed as perturbations in the neutral density and temperatures and hence fluctuations of airglow intensity and electron density. Since gravity waves are a dynamical process that transport energy between different atmospheric regions, they are an interesting example of the coupling of the ionosphere from below (e.g. generated through meteorological processes) and from above (e.g. generated through space weather conditions). In this study, gravity waves have been observed using Fabry-Perot Interferometer (FPI) intensity of oxygen red line emission at 630 nm and Global Positioning System (GPS) total electron content (TEC) measurements over Svalbard during enhanced auroral activity associated with substorms on the night of 6-7 Jan 2014. These disturbances have periods ranging between 32 and 58 minutes. Their propagation characteristics at 240 km as measured by the FPI and at 350 km as measured by GPS ground based receivers will be compared in order to gather further insight on the dissipation of energy as they propagate away from their source region.

  6. gravity

    Indian Academy of Sciences (India)

    We study the cosmological dynamics for R p exp( λ R ) gravity theory in the metric formalism, using dynamical systems approach. Considering higher-dimensional FRW geometries in case of an imperfect fluid which has two different scale factors in the normal and extra dimensions, we find the exact solutions, and study its ...

  7. A monochromatic gravity wave observed by the Flatland Atmospheric Observatory

    Science.gov (United States)

    Vanzandt, T. E.; Chun, Hye-Yeong; Clark, W. L.; Einaudi, F.; Nastrom, G. D.; Riddle, A. C.; Warnock, J. M.

    1993-01-01

    On 21 December 1991 from approximately 1300 to approximately 1600 UTC a monochromatic wave train with an 8.2-min period was observed by the suite of instruments at the Flatland Atmospheric Observatory (FAO), located in very flat terrain near Champaign-Urbana, Illinois. A 915-MHz radar measured the vertical wind velocity w every 60 s from 0.55 km MSL (0.34 km AGL) to approximately 3 km with 250-m range gates, and a 50-MHz radar measured the oblique wind in four directions, as well as w, every 130 s from 2.75 to approximately 7.25 km with 750-m range gates. A meteorological ground station measured the surface pressure P, wind speed vector u and azimuth alpha, temperature, solar insolation, etc., every 30 s. P was also measured every 120 s by six digital barograph stations within 30 km of Flatland. Using the hodograph of surface vector u and alpha and the impedance relation, we estimated the azimuthal direction of propagation phi to be 45 deg +/- 15 deg clockwise from north, the intrinsic and apparent horizontal phase speeds C(sub i) and C(sub o), respectively, (which are about equal since the direction of propagation is about normal to the mean wind) to be 21 +/- 5 m/s, and the horizontal wavelength lambda to be 10.0 +/- 2.5 km. The peak-to-peak surface horizontal perturbation velocity varied from approximately 2 to 5 m/s from cycle to cycle.

  8. 2D instabilities of surface gravity waves on a linear shear current

    Science.gov (United States)

    Francius, Marc; Kharif, Christian

    2016-04-01

    instabilities due to resonant four-wave interactions, as well as to study the influence of vorticity and nonlinearity on the characteristics of linear instabilities due to resonant five-wave and six-wave interactions. Depending on the dimensionless depth, superharmonic instabilities due to five-wave interactions can become dominant with increasing positive vorticiy. Acknowledgments: This work was supported by the Direction Générale de l'Armement and funded by the ANR project n°. ANR-13-ASTR-0007. References [1] A. Constantin, Two-dimensionality of gravity water flows of constant non-zero vorticity beneath a surface wave train, Eur. J. Mech. B/Fluids, 2011, 30, 12-16. [2] R. S. Johnson, On the modulation of water waves on shear flows, Proc. Royal Soc. Lond. A., 1976, 347, 537-546. [3] M. Oikawa, K. Chow, D. J. Benney, The propagation of nonlinear wave packets in a shear flow with a free surface, Stud. Appl. Math., 1987, 76, 69-92. [4] A. I Baumstein, Modulation of gravity waves with shear in water, Stud. Appl. Math., 1998, 100, 365-90. [5] R. Thomas, C. Kharif, M. Manna, A nonlinear Schrödinger equation for water waves on finite depth with constant vorticity, Phys. Fluids, 2012, 24, 127102. [6] M. M Rienecker, J. D Fenton, A Fourier approximation method for steady water waves , J. Fluid Mech., 1981, 104, 119-137 [7] M. Francius, C. Kharif, Three-dimensional instabilities of periodic gravity waves in shallow water, J. Fluid Mech., 2006, 561, 417-437

  9. Testing effective quantum gravity with gravitational waves from extreme mass ratio inspirals

    International Nuclear Information System (INIS)

    Yunes, N; Sopuerta, C F

    2010-01-01

    Testing deviation of GR is one of the main goals of the proposed Laser Interferometer Space Antenna. For the first time, we consistently compute the generation of gravitational waves from extreme-mass ratio inspirals (stellar compact objects into supermassive black holes) in a well-motivated alternative theory of gravity, that to date remains weakly constrained by double binary pulsar observations. The theory we concentrate on is Chern-Simons (CS) modified gravity, a 4-D, effective theory that is motivated both from string theory and loop-quantum gravity, and which enhances the Einstein-Hilbert action through the addition of a dynamical scalar field and the parity-violating Pontryagin density. We show that although point particles continue to follow geodesics in the modified theory, the background about which they inspiral is a modification to the Kerr metric, which imprints a CS correction on the gravitational waves emitted. CS modified gravitational waves are sufficiently different from the General Relativistic expectation that they lead to significant dephasing after 3 weeks of evolution, but such dephasing will probably not prevent detection of these signals, but instead lead to a systematic error in the determination of parameters. We end with a study of radiation-reaction in the modified theory and show that, to leading-order, energy-momentum emission is not CS modified, except possibly for the subdominant effect of scalar-field emission. The inclusion of radiation-reaction will allow for tests of CS modified gravity with space-borne detectors that might be two orders of magnitude larger than current binary pulsar bounds.

  10. Joint Optimization of Vertical Component Gravity and Seismic P-wave First Arrivals by Simulated Annealing

    Science.gov (United States)

    Louie, J. N.; Basler-Reeder, K.; Kent, G. M.; Pullammanappallil, S. K.

    2015-12-01

    Simultaneous joint seismic-gravity optimization improves P-wave velocity models in areas with sharp lateral velocity contrasts. Optimization is achieved using simulated annealing, a metaheuristic global optimization algorithm that does not require an accurate initial model. Balancing the seismic-gravity objective function is accomplished by a novel approach based on analysis of Pareto charts. Gravity modeling uses a newly developed convolution algorithm, while seismic modeling utilizes the highly efficient Vidale eikonal equation traveltime generation technique. Synthetic tests show that joint optimization improves velocity model accuracy and provides velocity control below the deepest headwave raypath. Detailed first arrival picking followed by trial velocity modeling remediates inconsistent data. We use a set of highly refined first arrival picks to compare results of a convergent joint seismic-gravity optimization to the Plotrefa™ and SeisOpt® Pro™ velocity modeling packages. Plotrefa™ uses a nonlinear least squares approach that is initial model dependent and produces shallow velocity artifacts. SeisOpt® Pro™ utilizes the simulated annealing algorithm and is limited to depths above the deepest raypath. Joint optimization increases the depth of constrained velocities, improving reflector coherency at depth. Kirchoff prestack depth migrations reveal that joint optimization ameliorates shallow velocity artifacts caused by limitations in refraction ray coverage. Seismic and gravity data from the San Emidio Geothermal field of the northwest Basin and Range province demonstrate that joint optimization changes interpretation outcomes. The prior shallow-valley interpretation gives way to a deep valley model, while shallow antiformal reflectors that could have been interpreted as antiformal folds are flattened. Furthermore, joint optimization provides a clearer image of the rangefront fault. This technique can readily be applied to existing datasets and could

  11. Damping of short gravity-capillary waves due to oil derivatives film on the water surface

    Science.gov (United States)

    Sergievskaya, Irina; Ermakov, Stanislav; Lazareva, Tatyana

    2016-10-01

    In this paper new results of laboratory studies of damping of gravity-capillary waves on the water surface covered by kerosene are presented and compared with our previous analysis of characteristics of crude oil and diesel fuel films. Investigations of kerosene films were carried out in a wide range values of film thicknesses (from some hundreds millimetres to a few millimetres) and in a wide range of surface wave frequencies (from 10 to 27 Hz). The selected frequency range corresponds to the operating wavelengths of microwave, X- to Ka-band radars typically used for the ocean remote sensing. The studied range of film thickness covers typical thicknesses of routine spills in the ocean. It is obtained that characteristics of waves, measured in the presence of oil derivatives films differ from those for crude oil films, in particular, because the volume viscosity of oil derivatives and crude oil is strongly different. To retrieve parameters of kerosene films from the experimental data the surface wave damping was analyzed theoretically in the frame of a model of two-layer fluid. The films are assumed to be soluble, so the elasticity on the upper and lower boundaries is considered as a function of wave frequency. Physical parameters of oil derivative films were estimated when tuning the film parameters to fit theory and experiment. Comparison between wave damping due to crude oil, kerosene and diesel fuel films have shown some capabilities of distinguishing of oil films from remote sensing of short surface waves.

  12. Field investigations on port non-tranquility caused by infra-gravity water waves

    Directory of Open Access Journals (Sweden)

    A. Najafi-Jilani

    2010-03-01

    Full Text Available Field investigations have been carried out in two 60-day stages on the surf beat low frequency waves in Anzali port, one of the main commercial ports in Iran, located in southwest coast of the Caspian Sea. The characteristics of significant water waves were measured at three metering stations in the sea, one at the entrance of the port and three in the basin. The measured data were inspected to investigate the surf beat negative effects on the tranquility of the port. Using field measurements and complementary numerical modeling, the response of the basin to the infra-gravity long waves was inspected for a range of wave frequencies. It was concluded that the water surface fluctuations in the port is strongly related to the incident wave period. The long waves with periods of about 45s were recognized as the worst cases for water surfaceperturbation in the port. For wave periods higher than the mentioned range, the order of fluctuation was generally low.

  13. Gravity Waves and Tidal Measurement Capabilities from a Space-borne Lidar across the Mesopause.

    Science.gov (United States)

    Dawkins, E. C. M.; Gardner, C. S.; Kaifler, B.; Marsh, D. R.; Janches, D.

    2017-12-01

    A new proposed NASA mission, ACaDAMe (Atmospheric Coupling and Dynamics Across the Mesopause region) consists of a space-borne sodium lidar, mounted upon the International Space Station. Combining the advantages of a lidar with the near-global coverage provided by the ISS (orbital inclination: 51.6o, orbital period: 92.7 mins), the ACaDAMe mission has enormous potential to quantify the waves that provide the major momentum and energy forcing of the Ionosphere-Thermosphere-Mesosphere system from below. Specifically, this mission seeks to quantify the dominant wave momentum and energy inputs across the mesopause, and identify the near-global distribution of gravity waves and tides that impact the Thermosphere/Ionosphere and are the terrestrial drivers of Space Weather. Leveraging on existing instrument heritage and expertise, this nadir-pointing narrowband lidar would be tuned to two-frequencies (at the peak of the D2a line, and at the minimum between the D2a and D2b peaks), with a capability to retrieve vertically-resolved [Na] and temperature, T, for both nighttime and daytime conditions. Here we outline the proposed mission, present an error characterization for [Na] and T, and describe the capabilities to estimate gravity waves and tidal features which will provide a crucial role in advancing our understanding of small-scale dynamical processes and coupling across this important atmospheric region.

  14. The Propagation of Tsunami Generated Acoustic-Gravity Waves in the Atmosphere

    Science.gov (United States)

    Wu, Y.; Llewellyn Smith, S.; Rottman, J.; Broutman, D.; Minster, J. B. H.

    2014-12-01

    Tsunami-generated acoustic-gravity waves propagate in the atmosphere up to the ionosphere, where they have been observed to have an impact on the total electron content (TEC). We simulate the propagation of 2D&3D linearized acoustic-gravity waves in the atmosphere by Fourier transforming in the horizontal and solving the vertical structure with a tsunami-perturbed lower boundary and an upper radiation boundary conditions. Starting from the algorithm of Broutman (2013) and the atmospheric profile of the 2004 Sumatra Tsunami, we add compressibility to the atmosphere and extend the calculation to three dimensions. Compressibility is an important feature of the real atmosphere, and we investigate its effect on wave propagation. We obtain the vertical wavenumber as a function of buoyancy frequency, density scale height, sound speed, and background wind velocity. Results show that wind shear and compressibility have a significant impact on wave transmission and reflection. We also investigate the 3D problem to allow variations in the bottom boundary condition and in the background wind profiles. Results are quite similar to the 2D case.

  15. Gravitational waves during inflation from a 5D large-scale repulsive gravity model

    Energy Technology Data Exchange (ETDEWEB)

    Reyes, Luz M., E-mail: luzmarinareyes@gmail.com [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Moreno, Claudia, E-mail: claudia.moreno@cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Madriz Aguilar, Jose Edgar, E-mail: edgar.madriz@red.cucei.udg.mx [Departamento de Matematicas, Centro Universitario de Ciencias Exactas e ingenierias (CUCEI), Universidad de Guadalajara (UdG), Av. Revolucion 1500, S.R. 44430, Guadalajara, Jalisco (Mexico); Bellini, Mauricio, E-mail: mbellini@mdp.edu.ar [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata (UNMdP), Funes 3350, C.P. 7600, Mar del Plata (Argentina); Instituto de Investigaciones Fisicas de Mar del Plata (IFIMAR) - Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) (Argentina)

    2012-10-22

    We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

  16. Gravitational waves during inflation from a 5D large-scale repulsive gravity model

    International Nuclear Information System (INIS)

    Reyes, Luz M.; Moreno, Claudia; Madriz Aguilar, José Edgar; Bellini, Mauricio

    2012-01-01

    We investigate, in the transverse traceless (TT) gauge, the generation of the relic background of gravitational waves, generated during the early inflationary stage, on the framework of a large-scale repulsive gravity model. We calculate the spectrum of the tensor metric fluctuations of an effective 4D Schwarzschild-de Sitter metric on cosmological scales. This metric is obtained after implementing a planar coordinate transformation on a 5D Ricci-flat metric solution, in the context of a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is nearly scale invariant under certain conditions. One interesting aspect of this model is that it is possible to derive the dynamical field equations for the tensor metric fluctuations, valid not just at cosmological scales, but also at astrophysical scales, from the same theoretical model. The astrophysical and cosmological scales are determined by the gravity-antigravity radius, which is a natural length scale of the model, that indicates when gravity becomes repulsive in nature.

  17. Dimensional reduction of gravity and relation between static states, cosmologies, and waves

    Science.gov (United States)

    de Alfaro, V.; Filippov, A. T.

    2007-12-01

    We introduce generalized dimensional reductions of an integrable (1+1)-dimensional dilaton gravity coupled to matter down to one-dimensional static states (black holes in particular), cosmological models, and waves. An unusual feature of these reductions is that the wave solutions depend on two variables: space and time. They are obtained here both by reducing the moduli space (available because of complete integrability) and by a generalized separation of variables (also applicable to nonintegrable models and to higher-dimensional theories). Among these new wavelike solutions, we find a class of solutions for which the matter fields are finite everywhere in space-time, including infinity. These considerations clearly demonstrate that a deep connection exists between static states, cosmologies, and waves. We argue that it should also exist in realistic higher-dimensional theories. Among other things, we also briefly outline the relations existing between the low-dimensional models that we discuss here and the realistic higher-dimensional ones.

  18. Electromagnetic waves in an axion-active relativistic plasma non-minimally coupled to gravity

    International Nuclear Information System (INIS)

    Balakin, Alexander B.; Muharlyamov, Ruslan K.; Zayats, Alexei E.

    2013-01-01

    We consider cosmological applications of a new self-consistent system of equations, accounting for a non-minimal coupling of the gravitational, electromagnetic and pseudoscalar (axion) fields in a relativistic plasma. We focus on dispersion relations for electromagnetic perturbations in an initially isotropic ultrarelativistic plasma coupled to the gravitational and axion fields in the framework of isotropic homogeneous cosmological model of the de Sitter type. We classify the longitudinal and transversal electromagnetic modes in an axionically active plasma and distinguish between waves (damping, instable or running), and nonharmonic perturbations (damping or instable). We show that for the special choice of the guiding model parameters the transversal electromagnetic waves in the axionically active plasma, non-minimally coupled to gravity, can propagate with the phase velocity smaller than the speed of light in vacuum, thus displaying a possibility for a new type of resonant particle-wave interactions. (orig.)

  19. Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

    Directory of Open Access Journals (Sweden)

    Lucas Lombriser

    2017-02-01

    Full Text Available With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar–tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar–tensor modification of gravity.

  20. Challenges to self-acceleration in modified gravity from gravitational waves and large-scale structure

    Science.gov (United States)

    Lombriser, Lucas; Lima, Nelson A.

    2017-02-01

    With the advent of gravitational-wave astronomy marked by the aLIGO GW150914 and GW151226 observations, a measurement of the cosmological speed of gravity will likely soon be realised. We show that a confirmation of equality to the speed of light as indicated by indirect Galactic observations will have important consequences for a very large class of alternative explanations of the late-time accelerated expansion of our Universe. It will break the dark degeneracy of self-accelerated Horndeski scalar-tensor theories in the large-scale structure that currently limits a rigorous discrimination between acceleration from modified gravity and from a cosmological constant or dark energy. Signatures of a self-acceleration must then manifest in the linear, unscreened cosmological structure. We describe the minimal modification required for self-acceleration with standard gravitational-wave speed and show that its maximum likelihood yields a 3σ poorer fit to cosmological observations compared to a cosmological constant. Hence, equality between the speeds challenges the concept of cosmic acceleration from a genuine scalar-tensor modification of gravity.

  1. Simple analytical methods for computing the gravity-wave contribution to the cosmic background radiation anisotropy

    International Nuclear Information System (INIS)

    Wang, Y.

    1996-01-01

    We present two simple analytical methods for computing the gravity-wave contribution to the cosmic background radiation (CBR) anisotropy in inflationary models; one method uses a time-dependent transfer function, the other methods uses an approximate gravity-mode function which is a simple combination of the lowest order spherical Bessel functions. We compare the CBR anisotropy tensor multipole spectrum computed using our methods with the previous result of the highly accurate numerical method, the open-quote open-quote Boltzmann close-quote close-quote method. Our time-dependent transfer function is more accurate than the time-independent transfer function found by Turner, White, and Lindsey; however, we find that the transfer function method is only good for l approx-lt 120. Using our approximate gravity-wave mode function, we obtain much better accuracy; the tensor multipole spectrum we find differs by less than 2% for l approx-lt 50, less than 10% for l approx-lt 120, and less than 20% for l≤300 from the open-quote open-quote Boltzmann close-quote close-quote result. Our approximate graviton mode function should be quite useful in studying tensor perturbations from inflationary models. copyright 1996 The American Physical Society

  2. Regional variations of mesospheric gravity-wave momentum flux over Antarctica

    Directory of Open Access Journals (Sweden)

    P. J. Espy

    2006-03-01

    Full Text Available Images of mesospheric airglow and radar-wind measurements have been combined to estimate the difference in the vertical flux of horizontal momentum carried by high-frequency gravity waves over two dissimilar Antarctic stations. Rothera (67° S, 68° W is situated in the mountains of the Peninsula near the edge of the wintertime polar vortex. In contrast, Halley (76° S, 27° W, some 1658 km to the southeast, is located on an ice sheet at the edge of the Antarctic Plateau and deep within the polar vortex during winter. The cross-correlation coefficients between the vertical and horizontal wind perturbations were calculated from sodium (Na airglow imager data collected during the austral winter seasons of 2002 and 2003 at Rothera for comparison with the 2000 and 2001 results from Halley reported previously (Espy et al., 2004. These cross-correlation coefficients were combined with wind-velocity variances from coincident radar measurements to estimate the daily averaged upper-limit of the vertical flux of horizontal momentum due to gravity waves near the peak emission altitude of the Na nightglow layer, 90km. The resulting momentum flux at both stations displayed a large day-to-day variability and showed a marked seasonal rotation from the northwest to the southwest throughout the winter. However, the magnitude of the flux at Rothera was about 4 times larger than that at Halley, suggesting that the differences in the gravity-wave source functions and filtering by the underlying winds at the two stations create significant regional differences in wave forcing on the scale of the station separation.

  3. Market protocols in ERCOT and their effect on wind generation

    International Nuclear Information System (INIS)

    Sioshansi, Ramteen; Hurlbut, David

    2010-01-01

    Integrating wind generation into power systems and wholesale electricity markets presents unique challenges due to the characteristics of wind power, including its limited dispatchability, variability in generation, difficulty in forecasting resource availability, and the geographic location of wind resources. Texas has had to deal with many of these issues beginning in 2002 when it restructured its electricity industry and introduced aggressive renewable portfolio standards that helped spur major investments in wind generation. In this paper we discuss the issues that have arisen in designing market protocols that take account of these special characteristics of wind generation and survey the regulatory and market rules that have been developed in Texas. We discuss the perverse incentives some of the rules gave wind generators to overschedule generation in order to receive balancing energy payments, and steps that have been taken to mitigate those incentive effects. Finally, we discuss more recent steps taken by the market operator and regulators to ensure transmission capacity is available for new wind generators that are expected to come online in the future. (author)

  4. An investigation of long-distance propagation of gravity waves under CAWSES India Phase II Programme

    Directory of Open Access Journals (Sweden)

    N. Parihar

    2015-05-01

    Full Text Available Coordinated measurements of airglow features from the mesosphere–lower thermosphere (MLT region were performed at Allahabad (25.5° N, 81.9° E and Gadanki (13.5° N, 79.2° E, India to study the propagation of gravity waves in 13–27° N latitude range during the period June 2009 to May 2010 under CAWSES (Climate And Weather of Sun Earth System India Phase II Programme. At Allahabad, imaging observations of OH broadband emissions and OI 557.7 nm emission were made using an all-sky imager, while at Gadanki photometric measurements of OH (6, 2 Meinel band and O2 (0, 1 Atmospheric band emissions were carried out. On many occasions, the nightly observations reveal the presence of similar waves at both locations. Typically, the period of observed similar waves lay in the 2.2–4.5 h range, had large phase speeds (~ 77–331 m s−1 and large wavelengths (~ 1194–2746 km. The images of outgoing long-wave radiation activity of the National Oceanic and Atmospheric Administration (NOAA and the high-resolution infrared images of KALPANA-1 satellite suggest that such waves possibly originated from some nearby convective sources. An analysis of their propagation characteristics in conjunction with SABER/TIMED temperature profiles and Horizontal Wind Model (HWM 2007 wind estimates suggest that the waves propagated over long distances (~ 1200–2000 km in atmospheric ducts.

  5. Horizontal ducting of sound by curved nonlinear internal gravity waves in the continental shelf areas.

    Science.gov (United States)

    Lin, Ying-Tsong; McMahon, Kara G; Lynch, James F; Siegmann, William L

    2013-01-01

    The acoustic ducting effect by curved nonlinear gravity waves in shallow water is studied through idealized models in this paper. The internal wave ducts are three-dimensional, bounded vertically by the sea surface and bottom, and horizontally by aligned wavefronts. Both normal mode and parabolic equation methods are taken to analyze the ducted sound field. Two types of horizontal acoustic modes can be found in the curved internal wave duct. One is a whispering-gallery type formed by the sound energy trapped along the outer and concave boundary of the duct, and the other is a fully bouncing type due to continual reflections from boundaries in the duct. The ducting condition depends on both internal-wave and acoustic-source parameters, and a parametric study is conducted to derive a general pattern. The parabolic equation method provides full-field modeling of the sound field, so it includes other acoustic effects caused by internal waves, such as mode coupling/scattering and horizontal Lloyd's mirror interference. Two examples are provided to present internal wave ducts with constant curvature and meandering wavefronts.

  6. Recent progress in mesospheric gravity wave studies using nightglow imaging system

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Michael J.; Pendleton Junior, William R.; Pautet, Pierre-Dominique; Zhao, Yucheng; Olsen, Chris; Babu, Hema Karnam Surendra [Center for Atmospheric and Space Sciences, Utah State University, Logan, Utah (United States); Medeiros, Amauri F. [Universidade Federal de Campina Grande, Centro de Ciencias e Tecnologia, Unidade Academica de Fisica, Campina Grande, PB (Brazil); Takahashi, Hisao, E-mail: mtaylor@cc.usu.edu, E-mail: wpen@cc.usu.edu, E-mail: dominiquepautet@gmail.com, E-mail: yucheng@cc.usu.edu, E-mail: cmellob@gmail.com, E-mail: hema_sb@rediffmail.com, E-mail: afragoso@df.ufcg.edu.br, E-mail: hisaotak@laser.inpe.br [INPE, Sao Jose dos Campos, SP (Brazil)

    2007-07-01

    A variety of optical remote sensing techniques have now revealed a rich spectrum of wave activity in the upper atmosphere. Many of these perturbations, with periodicities ranging from {approx} 5 min to many hours and horizontal scales of a few tens of km to several thousands km, are due to freely propagating atmospheric gravity waves and forced tidal oscillations. Passive optical observations of the spatial and temporal characteristics of these waves in the mesosphere and lower thermosphere (MLT) region ( {approx} 80-100 km) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art ground-based CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180 deg ) image measurements are used to illustrate the characteristics of small-scale, short period ( < 1 hour) waves and to investigate their seasonal propagation and momentum impact on the MLT region. These results are then contrasted with measurements of mesospheric temperature made using a new temperature mapping imaging system capable of determining induced temperature amplitudes of a large range of wave motions and investigating night-to-night and seasonal variability in mesospheric temperature. (author)

  7. Instability of combined gravity-inertial-Rossby waves in atmospheres and oceans

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2011-06-01

    Full Text Available The properties of the instability of combined gravity-inertial-Rossby waves on a β-plane are investigated. The wave-energy exchange equation shows that there is an exchange of energy with the background stratified medium. The energy source driving the instability lies in the background enthalpy released by the gravitational buoyancy force. It is shown that if the phase speed of the westward propagating low frequency-long wavelength Rossby wave exceeds the Poincaré-Kelvin (or "equivalent" shallow water wave speed, instability arises from the merging of Rossby and Poincaré modes. There are two key parameters in this instability condition; namely, the equatorial/rotational Mach (or Froude number M and the latitude θ0 of the β-plane. In general waves equatorward of a critical latitude for given M can be driven unstable, with corresponding growth rates of the order of a day or so. Although these conclusions may only be safely drawn for short wavelengths corresponding to a JWKB wave packet propagating internally and located far from boundaries, nevertheless such a local instability may play a significant role in atmosphere-ocean dynamics.

  8. Vertical Transport of Momentum by the Inertial-Gravity Internal Waves in a Baroclinic Current

    Directory of Open Access Journals (Sweden)

    A. A. Slepyshev

    2017-08-01

    Full Text Available When the internal waves break, they are one of the sources of small-scale turbulence. Small-scale turbulence causes the vertical exchange in the ocean. However, internal waves with regard to the Earth rotation in the presence of vertically inhomogeneous two-dimensional current are able to contribute to the vertical transport. Free inertial-gravity internal waves in a baroclinic current in a boundless basin of a constant depth are considered in the Bussinesq approximation. Boundary value problem of linear approximation for the vertical velocity amplitude of internal waves has complex coefficients when current velocity component, which is transversal to the wave propagation direction, depends on the vertical coordinate (taking into account the rotation of the Earth. Eigenfunction and wave frequency are complex, and it is shown that a weak wave damping takes place. Dispersive relation and wave damping decrement are calculated in the linear approximation. At a fixed wave number damping decrement of the second mode is larger (in the absolute value than the one of the first mode. The equation for vertical velocity amplitude for real profiles of the Brunt – Vaisala frequency and current velocity are numerically solved according to implicit Adams scheme of the third order of accuracy. The dispersive curves of the first two modes do not reach inertial frequency in the low-frequency area due to the effect of critical layers in which wave frequency of the Doppler shift is equal to the inertial one. Termination of the second mode dispersive curves takes place at higher frequency than the one of the first mode. In the second order of the wave amplitude the Stokes drift speed is determined. It is shown that the Stokes drift speed, which is transversal to the wave propagation direction, differs from zero if the transversal component of current velocity depends on the vertical coordinate. In this case, the Stokes drift speed in the second mode is lower than

  9. Atmospheric Gravity Waves and Turbulent Processes in the Mesopause Region Based on PMSE MAARSY Observations

    Science.gov (United States)

    Gudadze, N.; Chau, J. L.; Stober, G.; Latteck, R.

    2016-12-01

    Mesosphere-lower-thermosphere (MLT) polar dynamics are interesting and important subject for study in atmospheric physic. It is considered that mesopause region is where the main part of the Atmospheric gravity waves breaks and/or dissipates. However this region is difficult to observe. Continuous Observations of the polar summer mesosphere with the Middle Atmosphere Alomar Radar System (MAARSY) and its predecessor the ALOMAR-Wind-Radar (ALWIN) (before 2010), have been used to investigate dynamical structures of well-known phenomenon - Polar Mesosphere Summer Echoes (PMSE) which is an important tracer in the summer polar mesopause region. Signal to Noise Ratio (SNR) and Doppler radial velocity from the PMSE are used to investigate the wave-like motions with periods larger than 5 minutes. Such oscillations are studied in terms of atmospheric gravity waves (AGWs). Processes also connected with AGWs as PMSE layering, are studied in connection with the background conditions of the neutral atmosphere as well. Background winds are obtained from collocated meteor radar (MR). We used local enhancement method for the processing of altitude-time SNR images to detect layers in the PMSEs and characterised them. Our preliminary results indicate that PMSE strength and behaviour is correlated with the meridional wind. Furthermore we found that the spectral width (SW), which is a proxy of turbulence, is most of the time weakly dependent on SNR strength. However, there are some events where SW is highly dependent on SNR intensity indicating that they could be associated to turbulent-dominated events.

  10. Influence of the spatial distribution of gravity wave activity on the middle atmospheric dynamics

    Directory of Open Access Journals (Sweden)

    P. Šácha

    2016-12-01

    Full Text Available Analysing GPS radio occultation density profiles, we have recently pointed out a localised area of enhanced gravity wave (GW activity and breaking in the lower stratosphere of the east Asian–northwestern Pacific (EA/NP region. With a mechanistic model of the middle and upper atmosphere, experiments are performed to study the possible effect of such a localised GW breaking region on large-scale circulation and transport and, more generally, a possible influence of the spatial distribution of gravity wave activity on middle atmospheric dynamics.The results indicate the important role of the spatial distribution of GW activity for polar vortex stability, formation of planetary waves and for the strength and structure of zonal-mean residual circulation. Furthermore, a possible effect of a zonally asymmetric GW breaking in the longitudinal variability of the Brewer–Dobson circulation is analysed. Finally, consequences of our results for a variety of research topics (e.g. sudden stratospheric warming, atmospheric blocking, teleconnection patterns and a compensation mechanism between resolved and unresolved drag are discussed.

  11. Formation and mechanics of granular waves in gravity and shallow overland flow

    Science.gov (United States)

    Römkens, Mathias J. M.; Suryadevara, Madhu R.; Prasad, Shyam N.

    2010-05-01

    Sediment transport in overland flow is a highly complex process involving many properties relative to the flow regime characteristics, soil surface conditions, and type of sediment. From a practical standpoint, most sediment transport studies are concerned with developing relationships of rates of sediment movement under different hydraulic regimes in channel flow for use in soil erosion and sediment transport prediction models. Relatively few studies have focused on the more basic aspects of sediment movement in which particle-to-particle, particle-to-boundary, and particle-to-fluid interactions determine in an important way the nature of the movement. Our experimental work under highly controlled experimental conditions with both gravity flow of granular material (glass beads) in air and sediment transport (sand particles and glass beads) in shallow overland flow have shown that sediment movement is not a simple phenomenon solely determined by flow rates on a proportional basis, but that it is represented by a highly structured and organized regime determined by sedimentary fluid mechanical principles which yield very characteristic waves during transport. In the gravity flow case involving granular chute flow, two-dimensional grain waves developed into the rolling and saltating moving grain mass at certain grain concentrations. This phenomenon appeared to be related to an energy exchange process as a result of collisions between moving grain particles that led to reduced kinetic velocities. As a result, particle concentration differences in the direction of flow developed that were noted as denser zones. In these zones, particles dropped out at the upstream part of these denser zones to resume their accelerating motion once they reached the downstream part of the zone until, during the next collision event, the process is repeated. Thus a periodic granular wave structure evolved. Depending on the addition rate, the granular flow regime may be a fluidized

  12. Generation and Upper Atmospheric Propagation of Acoustic Gravity Waves according to Numerical Modeling and Radio Tomography

    Science.gov (United States)

    Vorontsov, Artem; Andreeva, Elena; Nesterov, Ivan; Padokhin, Artem; Kurbatov, Grigory

    2016-04-01

    The acoustic-gravity waves (AGW) in the upper atmosphere and ionosphere can be generated by a variety of the phenomena in the near-Earth environment and atmosphere as well as by some perturbations of the Earth's ground or ocean surface. For instance, the role of the AGW sources can be played by the earthquakes, explosions, thermal heating, seisches, tsunami waves. We present the examples of AGWs excited by the tsunami waves traveling in the ocean, by seisches, and by ionospheric heating by the high-power radio wave. In the last case, the gravity waves are caused by the pulsed modulation of the heating wave. The AGW propagation in the upper atmosphere induces the variations and irregularities in the electron density distribution of the ionosphere, whose structure can be efficiently reconstructed by the method of the ionospheric radio tomography (RT) based on the data from the global navigational satellite systems (GNSS). The input data for RT diagnostics are composed of the 150/400 MHz radio signals from the low-orbiting (LO) satellites and 1.2-1.5 GHz radio signals from the high-orbiting (HO) satellites with their orbits at ~1000 and ~20000 km above the ground, respectively. These data enable ionospheric imaging on different spatiotemporal scales with different spatiotemporal resolution and coverage, which is suitable, inter alia, for tracking the waves and wave-like features in the ionosphere. In particular, we demonstrate the maps of the ionospheric responses to the tornado at Moore (Oklahoma, USA) of May 20, 2013, which are reconstructed from the HO data. We present the examples of LORT images containing the waves and wavelike disturbances associated with various sources (e.g., auroral precipitation and high-power heating of the ionosphere). We also discuss the results of modeling the AGW generation by the surface and volumetric sources. The millihertz AGW from these sources initiate the ionospheric perturbation with a typical scale of a few hundred km at the

  13. Imaging gravity waves in lower stratospheric AMSU-A radiances, Part 2: Validation case study

    Directory of Open Access Journals (Sweden)

    S. D. Eckermann

    2006-01-01

    , horizontal structure and time evolution that closely match those observed in the AMSU-A data. These comparisons not only verify gravity wave detection and horizontal imaging capabilities for AMSU-A Channel 9, but provide an absolute validation of the anticipated radiance signals for a given three-dimensional gravity wave, based on the modeling of Eckermann and Wu (2006.

  14. Investigating of short period gravity waves using multi-beam experiments above Andenes in the polar summer mesopause

    Science.gov (United States)

    Stober, Gunter; Sommer, Svenja; Chau, Jorge L.; Latteck, Ralph

    2014-05-01

    In summer 2013 the Middle Atmosphere Alomar Radar System (MAARSY) conducted a multi-beam scanning experiment using 65 different beam directions. These systematic scanning experiments are analysed with respect to gravity waves with periods from 4 minutes up to 8 hours using polar mesospheric summer echoes (PMSE) as tracer. The gravity waves are investigated by decomposing the wind field into a mean wind and superimposed tidal components (diurnal, semidiurnal and terdiurnal). After subtracting these mean winds and tides we get a residuum wind dominated by the gravity waves with periods shorter than 8 hours. Using this approach we have been able to identified significant wave burst, with amplitudes as high as 50 m/s and 10-20 m/s for the horizontal and vertical wind components, respectively. In addition, we have identified events that indicate the development of KH-instabilities.

  15. Investigation of surge protective devices operation of a wind generator

    International Nuclear Information System (INIS)

    Dimitrov, D.; Vasileva, M.

    2008-01-01

    The interest to the investments in a wind energetics increases in the last years. The wind energetics is the fastest developing direction in the energetics in global scale. The wind energy is more attractive because its prices are lower in comparison of the other technologies for generating energy. The right choice of the surge protective devices has the important meaning on building and exploitation of the wind generators. The aim of this paper is investigation of the surge protective devices operation when they are installation to a wind generator. (authors)

  16. Environmental Impact Assessment of Wind Generators in the Czech Republic

    Directory of Open Access Journals (Sweden)

    Vladimír Lapčík

    2008-11-01

    Full Text Available The article summarizes author´s experience with environmental impact assessment in branch of wind generators. The introductorypart of paper describes legislative obligations of the Czech Republic in frame of fulfilling the European Union´s limits in branch ofrenewable energy resources utilization. Next part of paper deals with analysis of impacts of wind generators on the environment.The final part of paper deals with experience with implementation of the environmental impact assessment process (pursuant to the ActNo. 100/2001 Coll. in the field of wind power in the Czech Republic.

  17. Simultaneous observations of mesospheric gravity waves and sprites generated by a midwestern thunderstorm

    Science.gov (United States)

    Sentman, D. D.; Wescott, E. M.; Picard, R. H.; Winick, J. R.; Stenbaek-Nielsen, H. C.; Dewan, E. M.; Moudry, D. R.; Sa~O Sabbas, F. T.; Heavner, M. J.; Morrill, J.

    2003-03-01

    The present report investigates using simultaneous observations of coincident gravity waves and sprites to establish an upper limit on sprite-associated thermal energy deposition in the mesosphere. The University of Alaska operated a variety of optical imagers and photometers at two ground sites in support of the NASA Sprites99 balloon campaign. One site was atop a US Forest Service lookout tower on Bear Mt. in the Black Hills, in western South Dakota. On the night of 18 August 1999 we obtained from this site simultaneous images of sprites and OH airglow modulated by gravity waves emanating from a very active sprite producing thunderstorm over Nebraska, to the Southeast of Bear Mt. Using 25s exposures with a bare CCD camera equipped with a red filter, we were able to coincidentally record both short duration (3MR) N2 1PG red emissions from sprites and much weaker (~1kR), but persistent, OH Meinel nightglow emissions. A time lapse movie created from images revealed short period, complete /360° concentric wave structures emanating radially outward from a central excitation region directly above the storm. During the initial stages of the storm outwardly expanding waves possessed a period of τ~10min and wavelength λ~50km. Over a 1h interval the waves gradually changed to longer period τ~11min and shorter wavelength λ~40km. Over the full 2h observation time, about two dozen bright sprites generated by the underlying thunderstorm were recorded near the center of the outwardly radiating gravity wave pattern. No distinctive OH brightness signatures uniquely associated with the sprites were detected at the level of 2% of the ambient background brightness, establishing an associated upper limit of approximately ΔTthe volume of the sprites. The corresponding total thermal energy deposited by the sprite is bounded by these measurements to be less than ~1GJ. This value is well above the total energy deposited into the medium by the sprite, estimated by several

  18. Polarization-Based Tests of Gravity with the Stochastic Gravitational-Wave Background

    Directory of Open Access Journals (Sweden)

    Thomas Callister

    2017-12-01

    Full Text Available The direct observation of gravitational waves with Advanced LIGO and Advanced Virgo offers novel opportunities to test general relativity in strong-field, highly dynamical regimes. One such opportunity is the measurement of gravitational-wave polarizations. While general relativity predicts only two tensor gravitational-wave polarizations, general metric theories of gravity allow for up to four additional vector and scalar modes. The detection of these alternative polarizations would represent a clear violation of general relativity. The LIGO-Virgo detection of the binary black hole merger GW170814 has recently offered the first direct constraints on the polarization of gravitational waves. The current generation of ground-based detectors, however, is limited in its ability to sensitively determine the polarization content of transient gravitational-wave signals. Observation of the stochastic gravitational-wave background, in contrast, offers a means of directly measuring generic gravitational-wave polarizations. The stochastic background, arising from the superposition of many individually unresolvable gravitational-wave signals, may be detectable by Advanced LIGO at design sensitivity. In this paper, we present a Bayesian method with which to detect and characterize the polarization of the stochastic background. We explore prospects for estimating parameters of the background and quantify the limits that Advanced LIGO can place on vector and scalar polarizations in the absence of a detection. Finally, we investigate how the introduction of new terrestrial detectors like Advanced Virgo aid in our ability to detect or constrain alternative polarizations in the stochastic background. We find that, although the addition of Advanced Virgo does not notably improve detection prospects, it may dramatically improve our ability to estimate the parameters of backgrounds of mixed polarization.

  19. Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

    OpenAIRE

    F. Chane-Ming; D. Faduilhe; J. Leveau

    2008-01-01

    Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of total energy density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Stratosphere (LS) from 1992 to 2004 above Mahé (4° S, 55° E), Tromelin (15° S, 54° E) and La Réunion (21° S, 55° E) located in the tropical South-West Indian Ocean. The commonly used spectral index value (p≈5/3) of the i...

  20. Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line

    Directory of Open Access Journals (Sweden)

    E. A. K. Ford

    2006-03-01

    Full Text Available Gravity waves are an important feature of mesosphere - lower thermosphere (MLT dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. It is known that some gravity waves may propagate through the mesopause and reach greater altitudes before eventually "breaking" and depositing energy. The generation, propagation, and breaking of upper thermospheric gravity waves have not been studied directly often. However, their ionospheric counterparts, travelling ionospheric disturbances (TIDs, have been extensively studied in, for example, radar data. At high latitudes, it is believed localised auroral activity may generate gravity waves in-situ. Increases in sensor efficiency of Fabry-Perot Interferometers (FPIs located in northern Scandinavia have provided higher time resolution measurements of the auroral oval and polar cap atomic oxygen red line emission at 630.0 nm. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with periods ranging from a few tens of minutes to several hours. Oscillations are seen in the intensity of the line as well as the temperatures and line of sight winds. Instruments are located in Sodankylä, Finland; Kiruna, Sweden; Skibotn, Norway, and Svalbard in the Arctic Ocean. A case study is presented here, where a wave of 1.8 h period has a phase speed of 250 ms-1 with a propagation angle of 302°, and a horizontal wavelength of 1600 km. All the FPIs are co-located with EISCAT radars, as well as being supplemented by a range of other instrumentation. This allows the waves found in the FPI data to be put in context with the ionosphere and atmosphere system. Consequently, the source region of the gravity waves can be determined.

  1. Thermospheric gravity waves in Fabry-Perot Interferometer measurements of the 630.0nm OI line

    Directory of Open Access Journals (Sweden)

    E. A. K. Ford

    2006-03-01

    Full Text Available Gravity waves are an important feature of mesosphere - lower thermosphere (MLT dynamics, observed using many techniques and providing an important mechanism for energy transfer between atmospheric regions. It is known that some gravity waves may propagate through the mesopause and reach greater altitudes before eventually "breaking" and depositing energy. The generation, propagation, and breaking of upper thermospheric gravity waves have not been studied directly often. However, their ionospheric counterparts, travelling ionospheric disturbances (TIDs, have been extensively studied in, for example, radar data. At high latitudes, it is believed localised auroral activity may generate gravity waves in-situ. Increases in sensor efficiency of Fabry-Perot Interferometers (FPIs located in northern Scandinavia have provided higher time resolution measurements of the auroral oval and polar cap atomic oxygen red line emission at 630.0 nm. A Lomb-Scargle analysis of this data has shown evidence of gravity wave activity with periods ranging from a few tens of minutes to several hours. Oscillations are seen in the intensity of the line as well as the temperatures and line of sight winds. Instruments are located in Sodankylä, Finland; Kiruna, Sweden; Skibotn, Norway, and Svalbard in the Arctic Ocean. A case study is presented here, where a wave of 1.8 h period has a phase speed of 250 ms-1 with a propagation angle of 302°, and a horizontal wavelength of 1600 km. All the FPIs are co-located with EISCAT radars, as well as being supplemented by a range of other instrumentation. This allows the waves found in the FPI data to be put in context with the ionosphere and atmosphere system. Consequently, the source region of the gravity waves can be determined.

  2. MLT gravity wave climatology in the South America equatorial region observed by airglow imager

    Directory of Open Access Journals (Sweden)

    A. F. Medeiros

    2007-03-01

    Full Text Available An all-sky CCD imager for OH, O2 and OI (557.7 nm airglow emission measurements was operated at São João do Cariri (Cariri, Brazil (7° S, 36° W, from October 2000 to December 2004. A large amount of image data, more than 3000 h of observation and around 1000 wave events, makes it possible to classify the gravity wave characteristics, which are statistically significant. The observed waves show a typically short horizontal wavelength (5–45 km and a short period (5–35 min, and horizontal phase speeds of 1 to 80 m/s. In most cases band-type waves (horizontal wavelength between 10 and 60 km showed a clear preference for the horizontal propagation direction from the South American continent to the Atlantic Ocean. Ripples also have similar features but with different anisotropy. In this paper we focus our discussion on the wave characteristics of the bands and ripples and a comparison between them.

  3. Seasonal and nightly variations of gravity-wave energy density in the middle atmosphere measured by the Purple Crow Lidar

    Directory of Open Access Journals (Sweden)

    R. J. Sica

    2007-11-01

    Full Text Available The Purple Crow Lidar (PCL is a large power-aperture product monostatic Rayleigh-Raman-Sodium-resonance-fluorescence lidar, which has been in operation at the Delaware Observatory (42.9° N, 81.4° W, 237 m elevation near the campus of The University of Western Ontario since 1992. Kinetic-energy density has been calculated from the Rayleigh-scatter system measurements of density fluctuations at temporal-spatial scales relevant for gravity waves, e.g. soundings at 288 m height resolution and 9 min temporal resolution in the upper stratosphere and mesosphere. The seasonal averages from 10 years of measurements show in all seasons some loss of gravity-wave energy in the upper stratosphere. During the equinox periods and summer the measurements are consistent with gravity waves growing in height with little saturation, in agreement with the classic picture of the variations in the height at which gravity waves break given by Lindzen (1981. The mean values compare favourably to previous measurements when computed as nightly averages, but the high temporal-spatial resolution measurements show considerable day-to-day variability. The variability over a night is often extremely large, with typical RMS fluctuations of 50 to 100% at all heights and seasons common. These measurements imply that using a daily or nightly-averaged gravity-wave energy density in numerical models may be highly unrealistic.

  4. Secondary gravity waves from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere

    Science.gov (United States)

    Vadas, S.

    2017-12-01

    In this paper, we investigate the generation, propagation and effectsof secondary gravity waves (GWs) from momentum deposition in the stratosphere, mesosphere, thermosphere and ionosphere in high-resolution GW-resolving models and in TEC/lidar/redline data. We show that secondary GWs generated from the dissipation of orographic GWs at McMurdo Station in Antarctica play a dominant role in the wave activity over McMurdo in the wintertime mesosphere. These secondary GWs are created in the stratosphere, and have been identified in models and data via their telltale "fishbone" appearance in z-t plots. We also show that secondary GWs from the dissipation of GWs excited by deep convectiongenerate concentric rings in the F-region ionosphere. These model results and data point to the importance of secondary GWs from momentumdeposition in the Earth's atmosphere and ionosphere.

  5. Studies of Gravity Waves Using Michelson Interferometer Measurements of OH (3-1 Bands

    Directory of Open Access Journals (Sweden)

    Young-In Won

    2001-06-01

    Full Text Available As part of a long-term program for polar upper atmospheric studies, temperatures and intensities of the OH (3-1 bands were derived from spectrometric observations of airglow emissions over King Sejong station (62.22o S, 301.25o E. These measurements were made with a Michelson interferometer to cover wavelength regions between 1000 nm and 2000 nm. A spectral analysis was performed to individual nights of data to acquire information on the waves in the upper mesosphere/lower thermosphere. It is assumed that the measured fluctuations in the intensity and temperature of the OH (3-1 airglow were caused by gravity waves propagating through the emission layer. Correlation of intensity and temperature variation revealed oscillations with periods ranging from 2 to 9 hours. We also calculated Krassovsky's parameter and compared with published values.

  6. Imaging the Chicxulub central crater zone from large scale seismic acoustic wave propagation and gravity modeling

    Science.gov (United States)

    Fucugauchi, J. U.; Ortiz-Aleman, C.; Martin, R.

    2017-12-01

    Large complex craters are characterized by central uplifts that represent large-scale differential movement of deep basement from the transient cavity. Here we investigate the central sector of the large multiring Chicxulub crater, which has been surveyed by an array of marine, aerial and land-borne geophysical methods. Despite high contrasts in physical properties,contrasting results for the central uplift have been obtained, with seismic reflection surveys showing lack of resolution in the central zone. We develop an integrated seismic and gravity model for the main structural elements, imaging the central basement uplift and melt and breccia units. The 3-D velocity model built from interpolation of seismic data is validated using perfectly matched layer seismic acoustic wave propagation modeling, optimized at grazing incidence using shift in the frequency domain. Modeling shows significant lack of illumination in the central sector, masking presence of the central uplift. Seismic energy remains trapped in an upper low velocity zone corresponding to the sedimentary infill, melt/breccias and surrounding faulted blocks. After conversion of seismic velocities into a volume of density values, we use massive parallel forward gravity modeling to constrain the size and shape of the central uplift that lies at 4.5 km depth, providing a high-resolution image of crater structure.The Bouguer anomaly and gravity response of modeled units show asymmetries, corresponding to the crater structure and distribution of post-impact carbonates, breccias, melt and target sediments

  7. High Power Wind Generator Designs with Less or No PMs

    DEFF Research Database (Denmark)

    Boldea, Ion; Tutelea, Lucian; Blaabjerg, Frede

    2014-01-01

    The recent steep increase in high energy permanent magnet (PM) price (above 130$/kg and more) triggered already strong R&D efforts to develop wind generators with less PMs (less weight in NdFeB magnets/kW or the use of ferrite PMs) or fully without PMs. All these by optimizing existing dc excited...

  8. Sprites and mesospheric gravity waves during a summertime mesoscale convective event

    Science.gov (United States)

    Vollmer, D. R.; Sebben, J. E.; Murphy, R. L.; McHarg, M. G.; Harley, J.; Haaland, R. K.; Stenbaek-Nielsen, H. C.

    2017-12-01

    During the night of 22-23 July 2014, a mesoscale convective system containing several severe thunderstorms over western South Dakota and Nebraska produced a large number of sprites, photographed from the Wyoming Infrared Observatory using Phantom high-speed cameras. Several sprites were located in time and space via comparisons with large-amplitude positive cloud-to-ground (CG) flash locations using national Lightning Detection Network (NLDN) data. We analyze radar, NLDN, and satellite data from this event to examine the origin locations of the sprites relative to storm structure and CG lightning distribution. Additionally, one frame per second images obtained from a low-noise Andor Scientific CMOS camera showed regularly-spaced horizontal striations in the airglow both before and during several of the sprite events, suggesting the presence of vertically-propagating gravity waves in the middle atmosphere. Previous work hypothesized that these gravity waves are generated by the convective event itself and have been observed with other sprite events.

  9. Gravity Wave Relations in Density Coordinates and Application to Constant Density Balloon Data

    Science.gov (United States)

    Walterscheid, R. L.; Gelinas, L.; Mechoso, C. R.; Schubert, G.

    2008-12-01

    Super pressure balloons that are constrained to float on constant density surfaces have been used in a number of campaigns for gathering data for studies of stratospheric dynamics. The natural coordinate system for analyzing data from balloons that float at constant density is one where density, rather than geometrical height or pressure is the vertical coordinate. We show the equations of motion derived for constant density coordinates and show the gravity wave relations derived from them. Using these relations, we analyze data from the CNES VORCORE campaign, in which a total of 27 balloons circulated in the Antarctic polar stratospheric vortex during the late summer and spring of 2005. For this campaign, horizontal wind and pressure data were suitable for gravity wave analysis and we give relations for deducing the quantities (e.g., temperature and vertical wind fluctuations) required to calculate the momentum, heat and energy fluxes. We apply these relations to VORCORE data and show the results of flux calculations for balloon trajectories in various regions of the vortex.

  10. Analysis of the Effect of Electron Density Perturbations Generated by Gravity Waves on HF Communication Links

    Science.gov (United States)

    Fagre, M.; Elias, A. G.; Chum, J.; Cabrera, M. A.

    2017-12-01

    In the present work, ray tracing of high frequency (HF) signals in ionospheric disturbed conditions is analyzed, particularly in the presence of electron density perturbations generated by gravity waves (GWs). The three-dimensional numerical ray tracing code by Jones and Stephenson, based on Hamilton's equations, which is commonly used to study radio propagation through the ionosphere, is used. An electron density perturbation model is implemented to this code based upon the consideration of atmospheric GWs generated at a height of 150 km in the thermosphere and propagating up into the ionosphere. The motion of the neutral gas at these altitudes induces disturbances in the background plasma which affects HF signals propagation. To obtain a realistic model of GWs in order to analyze the propagation and dispersion characteristics, a GW ray tracing method with kinematic viscosity and thermal diffusivity was applied. The IRI-2012, HWM14 and NRLMSISE-00 models were incorporated to assess electron density, wind velocities, neutral temperature and total mass density needed for the ray tracing codes. Preliminary results of gravity wave effects on ground range and reflection height are presented for low-mid latitude ionosphere.

  11. Influences of Gravity Waves on Convectively Induced Turbulence (CIT): A Review

    Science.gov (United States)

    Sharman, Robert D.; Trier, S. B.

    2018-03-01

    Thunderstorms are known to produce turbulence. Such turbulence is commonly referred to as convectively induced turbulence or CIT, and can be hazardous to aviation. Although this turbulence can occur both within and outside the convection, out-of-cloud CIT is particularly hazardous, since it occurs in clear air and cannot be seen by eye or onboard radar. Furthermore, due to its small scale and its ties to the underlying convection, it is very difficult to forecast. Guidelines for out-of-cloud CIT avoidance are available, but they are oversimplified and can be misleading. In the search for more appropriate and physically based avoidance guidelines, considerable research has been conducted in recent years on the nature of the phenomenon, and in particular, its connection to gravity waves generated by the convection. This paper reviews the advances in our understanding of out-of-cloud CIT and its relation to convective gravity waves, and provides several detailed examples of observed cases to elucidate some of the underlying dynamics.

  12. Wind generator with electronic variable-speed drives

    Energy Technology Data Exchange (ETDEWEB)

    David, A.; Buchheit, N.; Jakobsen, H.

    1996-12-31

    Variable speed drives have been inserted between the network and the generator on certain recent wind power facilities. They have the following advantages: the drive allows the wind generator to operate at low speed with a significant reduction in acoustic noise, an important point if the facilities are sited near populated areas; the drive optimizes energy transfer, providing a gain of 4 to 10 %; the drive can possibly replace certain mechanical parts (the starting system and it in some cases, the reduction gear); the drive not only provides better transient management in relation to the network for less mechanical stress on the wind generator, it is also able to control reactive power. One commercial drive design sold by several manufacturers has already been installed on several wind generators with outputs of between 150 and 600 kw. In addition, such a solution is extremely well suited to mixed renewable energy systems. This design uses two inverse rectifier type converters and can therefore exchange energy in both directions. The equivalent drive with a single IGBT converter on the motor side and a diode converter on the network side is the solution most widely adopted throughout industry (with more than 50, 000 units installed in France per year). It still remains to be seen whether such a solution could be profitable in wind generator application (since the cost of the drive is quite high). This technical analysis is more destined for the converter-machine assembly specialists and is presented in this document, paying particular attention as it does to the modelling of the `wind energy - generator - drive - network` assembly, the associated drive command and control strategies and the simulations obtained during various transients. A 7.5 kW test bed has been installed in the Laboratoire d`Electronique de Puissance de Clamart, enabling tests to be carried out which emulate the operation of a wind generator.

  13. Directional asymmetry of the nonlinear wave phenomena in a three-dimensional granular phononic crystal under gravity.

    Science.gov (United States)

    Merkel, A; Tournat, V; Gusev, V

    2014-08-01

    We report the experimental observation of the gravity-induced asymmetry for the nonlinear transformation of acoustic waves in a noncohesive granular phononic crystal. Because of the gravity, the contact precompression increases with depth inducing space variations of not only the linear and nonlinear elastic moduli but also of the acoustic wave dissipation. We show experimentally and explain theoretically that, in contrast to symmetric propagation of linear waves, the amplitude of the nonlinearly self-demodulated wave depends on whether the propagation of the waves is in the direction of the gravity or in the opposite direction. Among the observed nonlinear processes, we report frequency mixing of the two transverse-rotational modes belonging to the optical band of vibrations and propagating with negative phase velocities, which results in the excitation of a longitudinal wave belonging to the acoustic band of vibrations and propagating with positive phase velocity. We show that the measurements of the gravity-induced asymmetry in the nonlinear acoustic phenomena can be used to compare the in-depth distributions of the contact nonlinearity and of acoustic absorption.

  14. Spontaneous generation and reversals of mean flows in a convectively-generated internal gravity wave field

    Science.gov (United States)

    Couston, Louis-Alexandre; Lecoanet, Daniel; Favier, Benjamin; Le Bars, Michael

    2017-11-01

    We investigate via direct numerical simulations the spontaneous generation and reversals of mean zonal flows in a stably-stratified fluid layer lying above a turbulent convective fluid. Contrary to the leading idealized theories of mean flow generation by self-interacting internal waves, the emergence of a mean flow in a convectively-generated internal gravity wave field is not always possible because nonlinear interactions of waves of different frequencies can disrupt the mean flow generation mechanism. Strong mean flows thus emerge when the divergence of the Reynolds stress resulting from the nonlinear interactions of internal waves produces a strong enough anti-diffusive acceleration for the mean flow, which, as we will demonstrate, is the case when the Prandtl number is sufficiently low, or when the energy input into the internal wavefield by the convection and density stratification are sufficiently large. Implications for mean zonal flow production as observed in the equatorial stratospheres of the Earth, Saturn and Jupiter, and possibly occurring in other geophysical systems such as planetary and stellar interiors will be briefly discussed. Funding provided by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program through Grant Agreement No. 681835-FLUDYCO-ERC-2015-CoG.

  15. The MaCWAVE program to study gravity wave influences on the polar mesosphere

    Directory of Open Access Journals (Sweden)

    R. A. Goldberg

    2006-07-01

    Full Text Available MaCWAVE (Mountain and Convective Waves Ascending VErtically was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT. The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and a slowing of the formation of polar mesospheric summer echoes (PMSE and noctilucent clouds (NLC. This

  16. Deep water velocities and particle displacements induced by acoustic-gravity waves from submarine earthquakes

    Science.gov (United States)

    Oliveira, T. C. A.; Kadri, U.

    2016-02-01

    An uplift of the ocean bottom caused by a submarine earthquake can generate Acoustic-Gravity Waves (AGW), progressive compression-type waves that travel at near the speed of sound in water. The role of AGW for oceans hydrodynamics has recently became a topic of increasing scientific interest. Kadri [Deep ocean water transport by acoustic-gravity waves, J.Geo. Res. Oceans, 119, (2014)] showed theoretically that AGW can contribute to deep ocean currents and circulation. We analyze and simulate the fundamental AGW modes generated by a submarine earthquake. We consider the first five AGW modes and show that they may all induce comparable temporal variations in water particle velocities at different depths in regions far from the epicenter. Results of temporal variations of horizontal and vertical fluid parcel velocities induced by AGW confirm chaotic flow trajectories at different water depths. A realistic example based on the 2004 Indian Ocean earthquake shows that vertical water particle displacements of O(10-2 ) m can be generated at 1 Km depth in a 4 km water depth ocean. We show that the velocity field depends on the presence of the leading AGW modes. Each AGW mode becomes evanescent at a critical time, at which energy is transferred to the next higher modes. Consequently, the main pattern of the velocity field changes as the leading mode change. As an example, for a reference point located at 1000 Km from the epicenter, the first five AGW become evanescent after 1.6, 4.6, 7.7, 10.8 and 13.8 hours, respectively. Our analysis and simulations shed light on the spatio-temporal evolution of the deep water velocities and particle displacements induced by AGW that radiate during submarine earthquakes. Thus, this work is a contribution to understand the role of high moment magnitude submarine earthquakes in deep water mixing mechanism.

  17. Properties of internal planetary-scale inertio gravity waves in the mesosphere

    Directory of Open Access Journals (Sweden)

    H. G. Mayr

    2004-11-01

    Full Text Available At high latitudes in the upper mesosphere, horizontal wind oscillations have been observed with periods around 10h. Waves with such a period are generated in our Numerical Spectral Model (NSM, and they are identified as planetary-scale inertio gravity waves (IGW. These IGWs have periods between 9 and 11h and appear above 60km in the zonal mean (m=0, as well as in m=1 to 4, propagating eastward and westward. Under the influence of the Coriolis force, the amplitudes of the waves propagating westward are larger at high latitudes than those propagating eastward. The waves grow in magnitude at least up to about 100km and have vertical wavelengths around 25km. Applying a running window of 15 days for spectral analysis, the amplitudes in the wind field are typically between 10 and 20m/s and can reach 30m/s in the westward propagating component for m=1 at the poles. In the temperature perturbations, the wave amplitudes above 100km are typically 5K and as large as 10K for m=0 at the poles. The IGWs are intermittent but reveal systematic seasonal variations, with the largest amplitudes occurring generally in late winter and spring. Numerical experiments show that such waves are also generated without excitation of the migrating tides. The amplitudes and periods then are similar, indicating that the tides are not essential to generate the waves. However, the seasonal variations without tides are significantly different, which leads to the conclusion that non linear interactions between the semidiurnal tide and planetary waves must contribute to the excitation of the IGWs. Directly or indirectly through the planetary waves, the IGWs are apparently excited by the instabilities that arise in the zonal mean circulation. When the solar heating is turned off for m=0, both the PWs and IGWs essentially disappear. That the IGWs and PWs have common roots in their excitation mechanism is also indicated by the striking similarity of their seasonal variations in the

  18. Renewable energy and sustainable communities: Alaska's wind generator experience.

    Science.gov (United States)

    Konkel, R Steven

    2013-01-01

    In 1984, the Alaska Department of Commerce and Economic Development (DCED) issued the State's first inventory/economic assessment of wind generators, documenting installed wind generator capacity and the economics of replacing diesel-fuel-generated electricity. Alaska's wind generation capacity had grown from hundreds of installed kilowatts to over 15.3 megawatts (MW) by January 2012. This article reviews data and conclusions presented in "Alaska's Wind Energy Systems; Inventory and Economic Assessment" (1). (Alaska Department of Commerce and Economic Development, S. Konkel, 1984). It provides a foundation and baseline for understanding the development of this renewable energy source. Today's technologies have evolved at an astonishing pace; a typical generator in an Alaska wind farm now is likely rated at 1.5-MW capacity, compared to the single-kilowatt (kW) machines present in 1984. Installed capacity has mushroomed, illustrated by Unalakleet's 600-kW wind farm dwarfing the original three 10-kW machines included in the 1984 inventory. Kodiak Electric had three 1.5-MW turbines installed at Pillar Mountain in 2009, with three additional turbines of 4.5-MW capacity installed in 2012. Utilities now actively plan for wind generation and compete for state funding. State of Alaska energy policy provides the context for energy project decision-making. Substantial renewable energy fund (REF) awards--$202,000,000 to date for 227 REF projects in the first 5 cycles of funding--along with numerous energy conservation programs--are now in place. Increasing investment in wind is driven by multiple factors. Stakeholders have interests both in public policy and meeting private investment objectives. Wind generator investors should consider project economics and potential impacts of energy decisions on human health. Specifically this article considers: changing environmental conditions in remote Alaska villages, impacts associated with climate change on human health, progress in

  19. Renewable energy and sustainable communities: Alaska's wind generator experience†

    Directory of Open Access Journals (Sweden)

    R. Steven Konkel

    2013-08-01

    Full Text Available Background . In 1984, the Alaska Department of Commerce and Economic Development (DCED issued the State's first inventory/economic assessment of wind generators, documenting installed wind generator capacity and the economics of replacing diesel-fuel-generated electricity. Alaska's wind generation capacity had grown from hundreds of installed kilowatts to over 15.3 megawatts (MW by January 2012. Method . This article reviews data and conclusions presented in “Alaska's Wind Energy Systems; Inventory and Economic Assessment” (1. (Alaska Department of Commerce and Economic Development, S. Konkel, 1984. It provides a foundation and baseline for understanding the development of this renewable energy source. Results . Today's technologies have evolved at an astonishing pace; a typical generator in an Alaska wind farm now is likely rated at 1.5-MW capacity, compared to the single-kilowatt (kW machines present in 1984. Installed capacity has mushroomed, illustrated by Unalakleet's 600-kW wind farm dwarfing the original three 10-kW machines included in the 1984 inventory. Kodiak Electric had three 1.5-MW turbines installed at Pillar Mountain in 2009, with three additional turbines of 4.5-MW capacity installed in 2012. Utilities now actively plan for wind generation and compete for state funding. Discussion . State of Alaska energy policy provides the context for energy project decision-making. Substantial renewable energy fund (REF awards – $202,000,000 to date for 227 REF projects in the first 5 cycles of funding – along with numerous energy conservation programs – are now in place. Increasing investment in wind is driven by multiple factors. Stakeholders have interests both in public policy and meeting private investment objectives. Wind generator investors should consider project economics and potential impacts of energy decisions on human health. Specifically this article considers: a. changing environmental conditions in remote Alaska

  20. Renewable energy and sustainable communities: Alaska's wind generator experience†

    Science.gov (United States)

    Konkel, R. Steven

    2013-01-01

    Background In 1984, the Alaska Department of Commerce and Economic Development (DCED) issued the State's first inventory/economic assessment of wind generators, documenting installed wind generator capacity and the economics of replacing diesel-fuel-generated electricity. Alaska's wind generation capacity had grown from hundreds of installed kilowatts to over 15.3 megawatts (MW) by January 2012. Method This article reviews data and conclusions presented in “Alaska's Wind Energy Systems; Inventory and Economic Assessment” (1). (Alaska Department of Commerce and Economic Development, S. Konkel, 1984). It provides a foundation and baseline for understanding the development of this renewable energy source. Results Today's technologies have evolved at an astonishing pace; a typical generator in an Alaska wind farm now is likely rated at 1.5-MW capacity, compared to the single-kilowatt (kW) machines present in 1984. Installed capacity has mushroomed, illustrated by Unalakleet's 600-kW wind farm dwarfing the original three 10-kW machines included in the 1984 inventory. Kodiak Electric had three 1.5-MW turbines installed at Pillar Mountain in 2009, with three additional turbines of 4.5-MW capacity installed in 2012. Utilities now actively plan for wind generation and compete for state funding. Discussion State of Alaska energy policy provides the context for energy project decision-making. Substantial renewable energy fund (REF) awards – $202,000,000 to date for 227 REF projects in the first 5 cycles of funding – along with numerous energy conservation programs – are now in place. Increasing investment in wind is driven by multiple factors. Stakeholders have interests both in public policy and meeting private investment objectives. Wind generator investors should consider project economics and potential impacts of energy decisions on human health. Specifically this article considers:changing environmental conditions in remote Alaska villages,impacts associated

  1. Frozen-wave instability in near-critical hydrogen subjected to horizontal vibration under various gravity fields.

    Science.gov (United States)

    Gandikota, G; Chatain, D; Amiroudine, S; Lyubimova, T; Beysens, D

    2014-01-01

    The frozen-wave instability which appears at a liquid-vapor interface when a harmonic vibration is applied in a direction tangential to it has been less studied until now. The present paper reports experiments on hydrogen (H2) in order to study this instability when the temperature is varied near its critical point for various gravity levels. Close to the critical point, a liquid-vapor density difference and surface tension can be continuously varied with temperature in a scaled, universal way. The effect of gravity on the height of the frozen waves at the interface is studied by performing the experiments in a magnetic facility where effective gravity that results from the coupling of the Earth's gravity and magnetic forces can be varied. The stability diagram of the instability is obtained. The experiments show a good agreement with an inviscid model [Fluid Dyn. 21 849 (1987)], irrespective of the gravity level. It is observed in the experiments that the height of the frozen waves varies weakly with temperature and increases with a decrease in the gravity level, according to a power law with an exponent of 0.7. It is concluded that the wave height becomes of the order of the cell size as the gravity level is asymptotically decreased to zero. The interface pattern thus appears as a bandlike pattern of alternate liquid and vapor phases, a puzzling phenomenon that was observed with CO2 and H2 near their critical point in weightlessness [Acta Astron. 61 1002 (2007); Europhys. Lett. 86 16003 (2009)].

  2. The effect of breaking gravity waves on the dynamics and chemistry of the mesosphere and lower thermosphere (invited review)

    Science.gov (United States)

    Garcia, R. R.

    1986-01-01

    The influence of breaking gravity waves on the dynamics and chemical composition of the 60 to 110 km region is investigated with a two dimensional model that includes a parameterization of gravity wave momentum deposition and diffusion. The dynamical model is described by Garcia and Solomon (1983) and Solomon and Garcia (1983) and includes a complete chemical scheme for the mesosphere and lower thermosphere. The parameterization of Lindzen (1981) is used to calculate the momentum deposited and the turbulent diffusion produced by the gravity waves. It is found that wave momentum deposition drives a very vigorous mean meridional circulation, produces a very cold summer mesopause and reverse the zonal wind jets above about 85 km. The seasonal variation of the turbulent diffusion coefficient is consistent with the behavior of mesospheric turbulences inferred from MST radar echoes. The large degree of consistency between model results and various types of dynamical and chemical data supports very strongly the hypothesis that breaking gravity waves play a major role in determining the zonally-averaged dynamical and chemical structure of the 60 to 110 km region of the atmosphere.

  3. The MaCWAVE program to study gravity wave influences on the polar mesosphere

    Directory of Open Access Journals (Sweden)

    R. A. Goldberg

    2006-07-01

    Full Text Available MaCWAVE (Mountain and Convective Waves Ascending VErtically was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT. The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and

  4. Gravity wave and neutrino bursts from stellar collapse: A sensitive test of neutrino masses

    International Nuclear Information System (INIS)

    Arnaud, N.; Barsuglia, M.; Bizouard, M.A.; Cavalier, F.; Davier, M.; Hello, P.; Pradier, T.

    2002-01-01

    New methods are proposed with the goal to determine absolute neutrino masses from the simultaneous observation of the bursts of neutrinos and gravitational waves emitted during a stellar collapse. It is shown that the neutronization electron neutrino flash and the maximum amplitude of the gravitational wave signal are tightly synchronized with the bounce occurring at the end of the core collapse on a time scale better than 1 ms. The existing underground neutrino detectors (SuperKamiokande, SNO,...) and the gravity wave antennas soon to operate (LIGO, VIRGO,...) are well matched in their performance for detecting galactic supernovae and for making use of the proposed approach. Several methods are described, which apply to the different scenarios depending on neutrino mixing. Given the present knowledge on neutrino oscillations, the methods proposed are sensitive to a mass range where neutrinos would essentially be mass degenerate. The 95% C.L. upper limit which can be achieved varies from 0.75 eV/c 2 for large ν e survival probabilities to 1.1 eV/c 2 when in practice all ν e 's convert into ν μ 's or ν τ 's. The sensitivity is nearly independent of the supernova distance

  5. Propagation of 3D internal gravity wave beams in a slowly varying stratification

    Science.gov (United States)

    Fan, Boyu; Akylas, T. R.

    2017-11-01

    The time-mean flows induced by internal gravity wave beams (IGWB) with 3D variations have been shown to have dramatic implications for long-term IGWB dynamics. While uniform stratifications are convenient both theoretically and in the laboratory, stratifications in the ocean can vary by more than an order of magnitude over the ocean depth. Here, in view of this fact, we study the propagation of a 3D IGWB in a slowly varying stratification. We assume that the stratification varies slowly relative to the local variations in the wave profile. In the 2D case, the IGWB bends in response to the changing stratification, but nonlinear effects are minor even in the finite amplitude regime. For a 3D IGWB, in addition to bending, we find that nonlinearity results in the transfer of energy from waves to a large-scale time-mean flow associated with the mean potential vorticity, similar to IGWB behavior in a uniform stratification. In a weakly nonlinear setting, we derive coupled evolution equations that govern this process. We also use these equations to determine the stability properties of 2D IGWB to 3D perturbations. These findings indicate that 3D effects may be relevant and possibly fundamental to IGWB dynamics in nature. Supported by NSF Grant DMS-1512925.

  6. Competing s-wave orders from Einstein-Gauss-Bonnet gravity

    Science.gov (United States)

    Li, Zhi-Hong; Fu, Yun-Chang; Nie, Zhang-Yu

    2018-01-01

    In this paper, the holographic superconductor model with two s-wave orders from 4 + 1 dimensional Einstein-Gauss-Bonnet gravity is explored in the probe limit. At different values of the Gauss-Bonnet coefficient α, we study the influence of tuning the mass and charge parameters of the bulk scalar field on the free energy curve of condensed solution with signal s-wave order, and compare the difference of tuning the two different parameters while the changes of the critical temperature are the same. Based on the above results, it is indicated that the two free energy curves of different s-wave orders can have one or two intersection points, where two typical phase transition behaviors of the s + s coexistent phase, including the reentrant phase transition near the Chern-Simons limit α = 0.25, can be found. We also give an explanation to the nontrivial behavior of the Tc- α curves near the Chern-Simons limit, which might be heuristic to understand the origin of the reentrant behavior near the Chern-Simons limit.

  7. Gravity wave amplitudes and momentum fluxes inferred from OH airglow intensities and meteor radar winds during SpreadFEx

    Directory of Open Access Journals (Sweden)

    F. Vargas

    2009-06-01

    Full Text Available We show in this report the momentum flux content input in the mesosphere due to relatively fast and small scale gravity waves (GWs observed through OH airglow images. The acquisition of OH NIR images was carried out in Brazil at Brasilia (14.8° S, 47.6° W and Cariri (7.4° S, 36.5° W from September 2005 to November 2005 during the SpreadFEx Campaign. Horizontal wind information from meteor radar was available in Cariri only. Our findings showed strong wave activity in both sites, mainly in Cariri. High wave directionality was also observed in both sites during SpreadFEx, which have been observed by other investigators using different analysis' techniques and different types of data during the campaign. We discuss also the possibility of plasma bubble seeding by gravity waves presenting spatial and temporal scales estimated with our novel analysis technique during the SpreadFEx campaign.

  8. Modeling and Parameter Estimation of a Small Wind Generation System

    Directory of Open Access Journals (Sweden)

    Carlos A. Ramírez Gómez

    2013-11-01

    Full Text Available The modeling and parameter estimation of a small wind generation system is presented in this paper. The system consists of a wind turbine, a permanent magnet synchronous generator, a three phase rectifier, and a direct current load. In order to estimate the parameters wind speed data are registered in a weather station located in the Fraternidad Campus at ITM. Wind speed data were applied to a reference model programed with PSIM software. From that simulation, variables were registered to estimate the parameters. The wind generation system model together with the estimated parameters is an excellent representation of the detailed model, but the estimated model offers a higher flexibility than the programed model in PSIM software.

  9. Issues and regulatory requirements for the connection of wind generation

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez Alvarez, J.M. [National University of San Juan (Argentina)], E-mail: jgimenez@unsj.edu.ar; Gomez Targarona, J.C. [National University of Rio Cuarto, Cordoba (Argentina). Electric Power Systems Protection Institute (IPSEP)], E-mail: jcgomez@ing.unrc.edu.ar

    2009-07-01

    Pollution problems such as greenhouse effect as well as the high value and volatility of fuel prices have forced and accelerated the development and use of renewable energy sources. In this work a complete revision of wind generation is presented. In the first part a brief history of the wind energy developments is detailed. Next, some commentaries related to the present and future state are made. Then, a revision of the modern structures of wind generation is realized. In fourth place it is included a brief comparison between small and big size turbines. Then, different types of energy storage are mentioned. Finally regulatory aspects are discussed, respect to the treatment of the technical problems. (author)

  10. A doubly-fed induction generator-based wind generation system with quasi-sine rotor injection

    Science.gov (United States)

    Yuvarajan, S.; Fan, Lingling

    Wind generating systems use doubly-fed induction generators (DFIGs) to achieve high conversion efficiency and to reduce the installation cost. The paper proposes and analyzes a simple DFIG-based wind generation system in which the excitation power is obtained from a photovoltaic (PV) panel and battery. The proposed scheme is suitable for small wind power systems for which a complex field orientation control is not justified. It can be used for stand-alone operation and also grid-tied operation. The rotor of the DFIG is applied with a quasi-sine wave instead of a sine wave. The operation and harmonic characteristics of the scheme are established using analysis, simulation, and experimentation. The details of the control circuit are given along with the experimental waveforms of voltages and currents and frequency spectra. The total harmonic distortion in the output current is found to be around 8%.

  11. Exploration of dispatch model integrating wind generators and electric vehicles

    International Nuclear Information System (INIS)

    Haque, A.N.M.M.; Ibn Saif, A.U.N.; Nguyen, P.H.; Torbaghan, S.S.

    2016-01-01

    Highlights: • A novel business model for the BRPs is analyzed. • Imbalance cost of wind generation is considered in the UC-ED model. • Smart charging of EVs is included into the UC-ED problem to mitigate the imbalance cost. • Effects of smart charging on generation cost, CO 2 emissions and total network load are assessed. - Abstract: In recent years, the share of renewable energy sources (RES) in the electricity generation mix has been expanding rapidly. However, limited predictability of the RES poses challenges for traditional scheduling and dispatching mechanisms based on unit commitment (UC) and economic dispatch (ED). This paper presents an advanced UC-ED model to incorporate wind generators as RES-based units alongside conventional centralized generators. In the proposed UC-ED model, an imbalance cost is introduced reflecting the wind generation uncertainty along with the marginal generation cost. The proposed UC-ED model aims to utilize the flexibility of fleets of plug-in electric vehicles (PEVs) to optimally compensate for the wind generation uncertainty. A case study with 15 conventional units and 3 wind farms along with a fixed-sized PEV fleet demonstrates that shifting of PEV fleets charging at times of high wind availability realizes generation cost savings. Nevertheless, the operational cost saving incurred by controlled charging appears to diminish when dispatched wind energy becomes considerably larger than the charging energy of PEV fleets. Further analysis of the results reveals that the effectiveness of PEV control strategy in terms of CO 2 emission reduction is strongly coupled with generation mix and the proposed control strategy is favored in cases where less pollutant-based plants like nuclear and hydro power are profoundly dominant.

  12. Operations model for utilities using wind-generator arrays

    Science.gov (United States)

    Schlueter, R. A.; Park, G. L.; Dorsey, J.; Lotfalian, M.; Shayanfar, A.

    1981-05-01

    The effects that various combinations of wind regime, array configuration and penetrations, and system characteristics have on system variables such as area control error, frequency, interchange power and spinning reserve are discussed. The characteristics of the combinations causing system operating stress or operating problems are denoted and methods for estimating effects on a simplified and on a detailed simulation basis are reported. Methods for reducing operating problems are suggested and involve array configurations, penetration, unit commitment and dispatch changes, and wind generator controls.

  13. A community small-scale wind generation project in Peru

    OpenAIRE

    Ferrer Martí, Laia; Garwood, Anna; Chiroque, José; Escobar, Rafael; Coello, Javier; Castro, Miguel

    2010-01-01

    Electrification systems based on renewable energy have proven to be suitable for providing decentralized electricity to isolated communities. Electricity generated through wind power is one of the technical options available, although infrequently used to date. This article aims to describe the main aspects of technical design, implementation and management of the first small-scale community wind generation project for rural electrification in Peru. This project took place in t...

  14. Gauge/gravity duality for interactions of spherical membranes in 11-dimensional pp-wave

    International Nuclear Information System (INIS)

    Lee, Hok Kong; McLoughlin, Tristan; Wu Xinkai

    2005-01-01

    We investigate the gauge/gravity duality in the interaction between two spherical membranes in the 11-dimensional pp-wave background. On the supergravity side, we find the solution to the field equations at locations close to a spherical source membrane, and use it to obtain the light-cone Lagrangian of a spherical probe membrane very close to the source, i.e., with their separation much smaller than their radii. On the gauge theory side, using the BMN matrix model, we compute the one-loop effective potential between two membrane fuzzy spheres. Perfect agreement is found between the two sides. Moreover, the one-loop effective potential we obtain on the gauge theory side is valid beyond the small-separation approximation, giving the full interpolation between interactions of membrane-like objects and that of graviton-like objects

  15. Some Expressions for Gravity without the Big G and their Possible Wave-Theoretical-Explanation

    Directory of Open Access Journals (Sweden)

    Tank H. K.

    2013-01-01

    Full Text Available This letter presents some new expressions for gravity without the big G and proposes their possible wave-theoretical-explanation. This attempt leads to some insight that: (i We need the proportionality-constant G because we measure masses and distances in our arbitrarily-chosen units of kg and meters; but if we measure “mass” as a fraction of “total-mass of the universe” M 0 and measure distances as a fraction of “radius-of-the- universe” R 0 then there is no need for the proportionality-constant G . However, large uncertainties in the M 0 and R 0 limit the general application of this relation presently. (ii The strength of gravity would be different if the total-mass of the universe were different. Then this possibility is supported with the help of wave-theory. (iii This understanding of G leads to an insight that Plancks-length, Planck-mass and Planck’s unit of time are geometric-mean-values of astrophysical quantities like: total-mass of the universe and the smallest-possible-mass hH 0 = c 2 . (iv There appears a law followed by various systems-of-matter, like: the electron, the proton, the nucleus-of-atom, the globular-clusters, the spiral-galaxies, the galactic-clusters and the whole universe; that their ratio Mass / Radius 2 remains constant. This law seems to be more fundamental than the fundamental-forces because it is obeyed irrespective of the case, whether the system is bound by strong-force, electric-force, or gravitational-force.

  16. Effects of Rotation and Gravity Field on Surface Waves in Fibre-Reinforced Thermoelastic Media under Four Theories

    Directory of Open Access Journals (Sweden)

    A. M. Abd-Alla

    2013-01-01

    Full Text Available Estimation is done to investigate the gravitational and rotational parameters effects on surface waves in fibre-reinforced thermoelastic media. The theory of generalized surface waves has been firstly developed and then it has been employed to investigate particular cases of waves, namely, Stoneley waves, Rayleigh waves, and Love waves. The analytical expressions for surface waves velocity and attenuation coefficient are obtained in the physical domain by using the harmonic vibrations and four thermoelastic theories. The wave velocity equations have been obtained in different cases. The numerical results are given for equation of coupled thermoelastic theory (C-T, Lord-Shulman theory (L-S, Green-Lindsay theory (G-L, and the linearized (G-N theory of type II. Comparison was made with the results obtained in the presence and absence of gravity, rotation, and parameters for fibre-reinforced of the material media. The results obtained are displayed by graphs to clear the phenomena physical meaning. The results indicate that the effect of gravity, rotation, relaxation times, and parameters of fibre-reinforced of the material medium is very pronounced.

  17. Distortion of gravitational-wave packets due to their self-gravity

    International Nuclear Information System (INIS)

    Kocsis, Bence; Loeb, Abraham

    2007-01-01

    When a source emits a gravity-wave (GW) pulse over a short period of time, the leading edge of the GW signal is redshifted more than the inner boundary of the pulse. The GW pulse is distorted by the gravitational effect of the self-energy residing in between these shells. We illustrate this distortion for GW pulses from the final plunge of black hole binaries, leading to the evolution of the GW profile as a function of the radial distance from the source. The distortion depends on the total GW energy released ε and the duration of the emission τ, scaled by the total binary mass M. The effect should be relevant in finite box simulations where the waveforms are extracted within a radius of 2 M. For characteristic emission parameters at the final plunge between binary black holes of arbitrary spins, this effect could distort the simulated GW templates for LIGO and LISA by a fraction of 10 -3 . Accounting for the wave distortion would significantly decrease the waveform extraction errors in numerical simulations

  18. Gravity wave momentum fluxes studies using OH imager, Na Lidar and meteor radar

    Science.gov (United States)

    Andrioli, Vania Fatima; Clemesha, Barclay; Batista, Paulo

    In this paper we have used atmospheric data, from 80 to 100 km altitude, measured by three different equipments for studying gravity wave activity. An OH CCD imager and a meteor radar located at Cachoeira Paulista (22.7 ° S, 45 ° W) were used together with a sodium lidar operating at São José dos Campos (23.1 ° S, 45.9 °W). We have used two years of data from 2007 to 2008 with 28 days of simultaneous data, totalizing 148 hours of observations. In an earlier presentation we inferred mean momentum fluxes and variances by using Hocking’s (2005) analysis of the meteor radar data and compared the variances values with the ones derived from Na lidar temperature profiles. The main objective of the present work is a comparison between the momentum fluxes inferred by using Hocking’s (2005) analysis of the meteor radar data and those derived from imaging data using the Swenson and Gardner (1998) model. This is an analytical model that relates the intensity perturbation of the OH emission to the relative perturbation in the atmospheric density. And then applying the GW polarization relations it is possible to compute the vertical energy and momentum fluxes due to waves seen in the OH emission.This analysis will make possible a comprehensive study of the momentum flux and variance due to GW over this region.

  19. On the influence of zonal gravity wave distributions on the Southern Hemisphere winter circulation

    Directory of Open Access Journals (Sweden)

    F. Lilienthal

    2017-07-01

    Full Text Available A mechanistic global circulation model is used to simulate the Southern Hemisphere stratospheric, mesospheric, and lower thermospheric circulation during austral winter. The model includes a gravity wave (GW parameterization that is initiated by prescribed 2-D fields of GW parameters in the troposphere. These are based on observations of GW potential energy calculated using GPS radio occultations and show enhanced GW activity east of the Andes and around the Antarctic. In order to detect the influence of an observation-based and thus realistic 2-D GW distribution on the middle atmosphere circulation, we perform model experiments with zonal mean and 2-D GW initialization, and additionally with and without forcing of stationary planetary waves (SPWs at the lower boundary of the model. As a result, we find additional forcing of SPWs in the stratosphere, a weaker zonal wind jet in the mesosphere, cooling of the mesosphere and warming near the mesopause above the jet. SPW wavenumber 1 (SPW1 amplitudes are generally increased by about 10 % when GWs are introduced being longitudinally dependent. However, at the upper part of the zonal wind jet, SPW1 in zonal wind and GW acceleration are out of phase, which reduces the amplitudes there.

  20. Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

    Directory of Open Access Journals (Sweden)

    F. Chane-Ming

    2007-01-01

    Full Text Available Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of total energy density of gravity waves (GW in the Upper Troposphere (UT and the Lower Stratosphere (LS from 1992 to 2004 above Mahé (4° S, 55° E, Tromelin (15° S, 54° E and La Réunion (21° S, 55° E located in the tropical South-West Indian Ocean. The commonly used spectral index value (p≈5/3 of the intrinsic frequency spectrum is used for calculating estimated total energy density in the UT and LS. Estimated total energy density provides good estimation of total energy density in the LS but underestimates total energy density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated total energy density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights<23 km above La Réunion.

  1. Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

    Science.gov (United States)

    Chane-Ming, F.; Faduilhe, D.; Leveau, J.

    2007-12-01

    Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of total energy density of gravity waves (GW) in the Upper Troposphere (UT) and the Lower Stratosphere (LS) from 1992 to 2004 above Mahé (4° S, 55° E), Tromelin (15° S, 54° E) and La Réunion (21° S, 55° E) located in the tropical South-West Indian Ocean. The commonly used spectral index value (p≈5/3) of the intrinsic frequency spectrum is used for calculating estimated total energy density in the UT and LS. Estimated total energy density provides good estimation of total energy density in the LS but underestimates total energy density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated total energy density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights<23 km above La Réunion.

  2. Latitudinal and seasonal variability of gravity-wave energy in the South-West Indian Ocean

    Directory of Open Access Journals (Sweden)

    F. Chane-Ming

    2008-01-01

    Full Text Available Vertical temperature profiles obtained by radiosonde and Raman lidar measurements are used to investigate a climatology of total energy density of gravity waves (GW in the Upper Troposphere (UT and the Lower Stratosphere (LS from 1992 to 2004 above Mahé (4° S, 55° E, Tromelin (15° S, 54° E and La Réunion (21° S, 55° E located in the tropical South-West Indian Ocean. The commonly used spectral index value (p≈5/3 of the intrinsic frequency spectrum is used for calculating estimated total energy density in the UT and LS. Estimated total energy density provides good estimation of total energy density in the LS but underestimates total energy density by one half in the UT above Mahé and Tromelin probably due to the activity of near-inertial frequency waves. Estimated total energy density reveals a strong seasonal variability as a function of latitude and convection as an evident active source of GW activity in the LS in austral summer. Above La Réunion, a semi-annual GW activity is observed in the LS with the signature of the subtropical barrier in the UT. Moreover, radiosondes and Raman lidar provide consistent GW surveys in the UT/LS at heights<23 km above La Réunion.

  3. Numerical Simulation of the Field Velocities and Local Disturbances of a Long Gravity Wave Passing above an Immersed Vertical Barrier

    Directory of Open Access Journals (Sweden)

    Laouar Abdelhamid

    2008-01-01

    Full Text Available This work is interested in the study of the passage of a long gravity wave above an immersed vertical barrier. The latter is placed at a right angle in the middle of the occupied fluid domain which is limited vertically by both a free surface and an impermeable horizontal bottom. We want to determine the field velocity and the local disturbances in the vicinity of the barrier. For this, we use the generalized theory of shallow water and complex variables method. For illustration, we consider a solitary wave as an emitted long wave.

  4. Satellite observations of middle atmosphere–thermosphere vertical coupling by gravity waves

    Directory of Open Access Journals (Sweden)

    Q. T. Trinh

    2018-03-01

    Full Text Available Atmospheric gravity waves (GWs are essential for the dynamics of the middle atmosphere. Recent studies have shown that these waves are also important for the thermosphere/ionosphere (T/I system. Via vertical coupling, GWs can significantly influence the mean state of the T/I system. However, the penetration of GWs into the T/I system is not fully understood in modeling as well as observations. In the current study, we analyze the correlation between GW momentum fluxes observed in the middle atmosphere (30–90 km and GW-induced perturbations in the T/I. In the middle atmosphere, GW momentum fluxes are derived from temperature observations of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER satellite instrument. In the T/I, GW-induced perturbations are derived from neutral density measured by instruments on the Gravity field and Ocean Circulation Explorer (GOCE and CHAllenging Minisatellite Payload (CHAMP satellites. We find generally positive correlations between horizontal distributions at low altitudes (i.e., below 90 km and horizontal distributions of GW-induced density fluctuations in the T/I (at 200 km and above. Two coupling mechanisms are likely responsible for these positive correlations: (1 fast GWs generated in the troposphere and lower stratosphere can propagate directly to the T/I and (2 primary GWs with their origins in the lower atmosphere dissipate while propagating upwards and generate secondary GWs, which then penetrate up to the T/I and maintain the spatial patterns of GW distributions in the lower atmosphere. The mountain-wave related hotspot over the Andes and Antarctic Peninsula is found clearly in observations of all instruments used in our analysis. Latitude–longitude variations in the summer midlatitudes are also found in observations of all instruments. These variations and strong positive correlations in the summer midlatitudes suggest that GWs with origins related to convection also

  5. Lidar observation of middle atmospheric gravity wave activity over a southern sub-tropical station, Reunion Island (21°S; 55°E)

    CSIR Research Space (South Africa)

    Sivakumar, V

    2006-07-01

    Full Text Available of the study Instrument used : LiDAR ( System and Specifications ) Data used and Method of analysis Results Gravity Wave characteristics ( Time period, vertical wavelength and potential energy ) Over all mean characteristics Summer and Winter... technique in the height range 30 - 80 km. GW Studies are confined to mid- and high latitudes. Mid- and high latitude results are : Gravity wave activity maximum during winter and minimum during summer. The dominant wave periods range from 2 to 8 hrs...

  6. Simultaneous Antarctic Gravity Wave Observations in PMCs from the AIM Satellite and PMSE Observations from PANSY Radar

    Science.gov (United States)

    Buzanowicz, M. E.; Yue, J.; Russell, J. M., III; Sato, K.; Kohma, M.; Nakamura, T.

    2015-12-01

    Polar mesospheric clouds (PMCs) are high-altitude ice clouds that form in the cold summer mesopause region due to adiabatic cooling caused by an upwelling induced by the global meridional circulation, which is driven by gravity wave dissipation and forcing. Polar mesospheric summer echoes (PMSEs) are strong coherent echoes also observed in the polar summer mesosphere and are considered to be related to ionization and the small-scale structure associated with PMCs, with their origins thought to be strongly related. The peak PMSE height can be located slightly below the summer mesopause temperature minimum but above the PMC altitude. Upward propagating atmospheric gravity waves (AGWs) are usually considered to be the cause of the wave patterns seen in PMCs. Monitoring PMCs and PMSEs will provide important tools in detecting climate change in the upper atmosphere and a better understanding of the earth-climate system. The science goal I plan to accomplish is to investigate the possibility of a connection between gravity wave perturbation characteristics in PMCs from the AIM (Aeronomy of Ice in the Mesosphere) satellite and PMSE structures observed by PANSY (program of the Antarctic Syowa MST/IS radar). Data from the CIPS instrument onboard AIM, PANSY, and AIRS (Atmospheric Infrared Sounder) will be used. AIM provides a two-dimensional horizontal view of the atmosphere dynamics embedded in PMCs, while PANSY provides a vertical view of PMSEs and gravity waves with high temporal resolution. The combination of AIM and PANSY will provide a three-dimensional view of the atmosphere, AGWs, PMCs and PMSEs. AIRS provides information about AGWs in the stratosphere. Wave analysis of the Fast Fourier Transform or a wavelet analysis will be used to complete the science goal. AIRS will be used to examine how lower atmosphere meteorology may impact the PMC and PMSE structures.

  7. Numerical modeling study of the momentum deposition of small amplitude gravity waves in the thermosphere

    Directory of Open Access Journals (Sweden)

    X. Liu

    2013-01-01

    Full Text Available We study the momentum deposition in the thermosphere from the dissipation of small amplitude gravity waves (GWs within a wave packet using a fully nonlinear two-dimensional compressible numerical model. The model solves the nonlinear propagation and dissipation of a GW packet from the stratosphere into the thermosphere with realistic molecular viscosity and thermal diffusivity for various Prandtl numbers. The numerical simulations are performed for GW packets with initial vertical wavelengths (λz ranging from 5 to 50 km. We show that λz decreases in time as a GW packet dissipates in the thermosphere, in agreement with the ray trace results of Vadas and Fritts (2005 (VF05. We also find good agreement for the peak height of the momentum flux (zdiss between our simulations and VF05 for GWs with initial λz ≤ 2π H in an isothermal, windless background, where H is the density scale height. We also confirm that zdiss increases with increasing Prandtl number. We include eddy diffusion in the model, and find that the momentum deposition occurs at lower altitudes and has two separate peaks for GW packets with small initial λz. We also simulate GW packets in a non-isothermal atmosphere. The net λz profile is a competition between its decrease from viscosity and its increase from the increasing background temperature. We find that the wave packet disperses more in the non-isothermal atmosphere, and causes changes to the momentum flux and λz spectra at both early and late times for GW packets with initial λz ≥ 10 km. These effects are caused by the increase in T in the thermosphere, and the decrease in T near the mesopause.

  8. Large-scale dynamical influence of a gravity wave generated over the Antarctic Peninsula – regional modelling and budget analysis

    Directory of Open Access Journals (Sweden)

    JOEL Arnault

    2013-03-01

    Full Text Available The case study of a mountain wave triggered by the Antarctic Peninsula on 6 October 2005, which has already been documented in the literature, is chosen here to quantify the associated gravity wave forcing on the large-scale flow, with a budget analysis of the horizontal wind components and horizontal kinetic energy. In particular, a numerical simulation using the Weather Research and Forecasting (WRF model is compared to a control simulation with flat orography to separate the contribution of the mountain wave from that of other synoptic processes of non-orographic origin. The so-called differential budgets of horizontal wind components and horizontal kinetic energy (after subtracting the results from the simulation without orography are then averaged horizontally and vertically in the inner domain of the simulation to quantify the mountain wave dynamical influence at this scale. This allows for a quantitative analysis of the simulated mountain wave's dynamical influence, including the orographically induced pressure drag, the counterbalancing wave-induced vertical transport of momentum from the flow aloft, the momentum and energy exchanges with the outer flow at the lateral and upper boundaries, the effect of turbulent mixing, the dynamics associated with geostrophic re-adjustment of the inner flow, the deceleration of the inner flow, the secondary generation of an inertia–gravity wave and the so-called baroclinic conversion of energy between potential energy and kinetic energy.

  9. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  10. Instability of coupled gravity-inertial-Rossby waves on a β-plane in solar system atmospheres

    Directory of Open Access Journals (Sweden)

    J. F. McKenzie

    2009-11-01

    Full Text Available This paper provides an analysis of the combined theory of gravity-inertial-Rossby waves on a β-plane in the Boussinesq approximation. The wave equation for the system is fifth order in space and time and demonstrates how gravity-inertial waves on the one hand are coupled to Rossby waves on the other through the combined effects of β, the stratification characterized by the Väisälä-Brunt frequency N, the Coriolis frequency f at a given latitude, and vertical propagation which permits buoyancy modes to interact with westward propagating Rossby waves. The corresponding dispersion equation shows that the frequency of a westward propagating gravity-inertial wave is reduced by the coupling, whereas the frequency of a Rossby wave is increased. If the coupling is sufficiently strong these two modes coalesce giving rise to an instability. The instability condition translates into a curve of critical latitude Θc versus effective equatorial rotational Mach number M, with the region below this curve exhibiting instability. "Supersonic" fast rotators are unstable in a narrow band of latitudes around the equator. For example Θc~12° for Jupiter. On the other hand slow "subsonic" rotators (e.g. Mercury, Venus and the Sun's Corona are unstable at all latitudes except very close to the poles where the β effect vanishes. "Transonic" rotators, such as the Earth and Mars, exhibit instability within latitudes of 34° and 39°, respectively, around the Equator. Similar results pertain to Oceans. In the case of an Earth's Ocean of depth 4km say, purely westward propagating waves are unstable up to 26° about the Equator. The nonlinear evolution of this instability which feeds off rotational energy and gravitational buoyancy may play an important role in atmospheric dynamics.

  11. Surface gravity wave effects in the oceanic boundary layer: large-eddy simulation with vortex force and stochastic breakers

    Science.gov (United States)

    Sullivan, Peter P.; McWilliams, James C.; Melville, W. Kendall

    The wind-driven stably stratified mid-latitude oceanic surface turbulent boundary layer is computationally simulated in the presence of a specified surface gravity-wave field. The gravity waves have broad wavenumber and frequency spectra typical of measured conditions in near-equilibrium with the mean wind speed. The simulation model is based on (i) an asymptotic theory for the conservative dynamical effects of waves on the wave-averaged boundary-layer currents and (ii) a boundary-layer forcing by a stochastic representation of the impulses and energy fluxes in a field of breaking waves. The wave influences are shown to be profound on both the mean current profile and turbulent statistics compared to a simulation without these wave influences and forced by an equivalent mean surface stress. As expected from previous studies with partial combinations of these wave influences, Langmuir circulations due to the wave-averaged vortex force make vertical eddy fluxes of momentum and material concentration much more efficient and non-local (i.e. with negative eddy viscosity near the surface), and they combine with the breakers to increase the turbulent energy and dissipation rate. They also combine in an unexpected positive feedback in which breaker-generated vorticity seeds the creation of a new Langmuir circulation and instigates a deep strong intermittent downwelling jet that penetrates through the boundary layer and increases the material entrainment rate at the base of the layer. These wave effects on the boundary layer are greater for smaller wave ages and higher mean wind speeds.

  12. Improving the realism of gravity waves generated by convection in numerical models

    Science.gov (United States)

    Stephan, Claudia Christine

    Small-scale gravity waves (GWs) with horizontal wavelengths of tens up to several hundred kilometers have demonstrated importance for driving the general circulation of the atmosphere, which affects many climate processes. GWs that propagate vertically from the troposphere into the middle atmosphere eventually dissipate and deposit momentum to the mean flow. Through this process they influence the timing of the transition in springtime from winter westerlies to summer easterlies in the stratosphere. They also play an important role in driving the mean-meridional transport circulation, the Brewer-Dobson circulation, and in the tropics help drive the Quasi-Biennial Oscillation and the Semi-Annual Oscillation. GWs with scales on the order of the size of a model grid box or smaller remain unresolved in Global Circulation Models (GCMs) and therefore need to be parameterized. GWs are generated by a variety of sources including orography, convection, and geostrophic adjustment in regions of baroclinic instability. We focus here in particular on convectively-generated GWs, which are prevalent in the tropics and summer mid-latitudes. Their parameterizations in climate models range in complexity from simple assumptions of uniform sources to more complex methods that relate the spectrum of GWs to properties of convection in the climate model. The parameter settings that must be chosen to apply these GW parameterizations are poorly constrained by observations, so they are instead based largely on cloud-resolving model results. Cloud-resolving model studies themselves use parameterized physics for the microphysics of precipitation particle formation. We first explore the sensitivity of the waves generated in cloud-resolving models to these physics parameterizations and show that knowledge of large-scale storm conditions is sufficient to predict the large-area and time-average spectrum of GW momentum flux above storms, irrespective of the convective details that coarse

  13. Generation Expansion Planning Considering Integrating Large-scale Wind Generation

    DEFF Research Database (Denmark)

    Zhang, Chunyu; Ding, Yi; Østergaard, Jacob

    2013-01-01

    necessitated the inclusion of more innovative and sophisticated approaches in power system investment planning. A bi-level generation expansion planning approach considering large-scale wind generation was proposed in this paper. The first phase is investment decision, while the second phase is production...... optimization decision. A multi-objective PSO (MOPSO) algorithm was introduced to solve this optimization problem, which can accelerate the convergence and guarantee the diversity of Pareto-optimal front set as well. The feasibility and effectiveness of the proposed bi-level planning approach and the MOPSO...

  14. Reactive power management of power networks with wind generation

    CERN Document Server

    Amaris, Hortensia; Ortega, Carlos Alvarez

    2012-01-01

    As the energy sector shifts and changes to focus on renewable technologies, the optimization of wind power becomes a key practical issue. Reactive Power Management of Power Networks with Wind Generation brings into focus the development and application of advanced optimization techniques to the study, characterization, and assessment of voltage stability in power systems. Recent advances on reactive power management are reviewed with particular emphasis on the analysis and control of wind energy conversion systems and FACTS devices. Following an introduction, distinct chapters cover the 5 key

  15. Gravity wave control on ESF day-to-day variability: An empirical approach

    Science.gov (United States)

    Aswathy, R. P.; Manju, G.

    2017-06-01

    The gravity wave control on the daily variation in nighttime ionization irregularity occurrence is studied using ionosonde data for the period 2002-2007 at magnetic equatorial location Trivandrum. Recent studies during low solar activity period have revealed that the seed perturbations should have the threshold amplitude required to trigger equatorial spread F (ESF), at a particular altitude and that this threshold amplitude undergoes seasonal and solar cycle changes. In the present study, the altitude variation of the threshold seed perturbations is examined for autumnal equinox of different years. Thereafter, a unique empirical model, incorporating the electrodynamical effects and the gravity wave modulation, is developed. Using the model the threshold curve for autumnal equinox season of any year may be delineated if the solar flux index (F10.7) is known. The empirical model is validated using the data for high, moderate, and low solar epochs in 2001, 2004, and 1995, respectively. This model has the potential to be developed further, to forecast ESF incidence, if the base height of ionosphere is in the altitude region where electrodynamics controls the occurrence of ESF. ESF irregularities are harmful for communication and navigation systems, and therefore, research is ongoing globally to predict them. In this context, this study is crucial for evolving a methodology to predict communication as well as navigation outages.Plain Language SummaryThe manifestation of nocturnal ionospheric irregularities at magnetic equatorial regions poses a major hazard for communication and navigation systems. It is therefore essential to arrive at prediction methodologies for these irregularities. The present study puts forth a novel empirical model which, using only solar flux index, successfully differentiates between days with and without nocturnal ionization irregularity occurrence. The model-derived curve is obtained such that the days with and without occurrence of

  16. Design of High Performance Permanent-Magnet Synchronous Wind Generators

    Directory of Open Access Journals (Sweden)

    Chun-Yu Hsiao

    2014-11-01

    Full Text Available This paper is devoted to the analysis and design of high performance permanent-magnet synchronous wind generators (PSWGs. A systematic and sequential methodology for the design of PMSGs is proposed with a high performance wind generator as a design model. Aiming at high induced voltage, low harmonic distortion as well as high generator efficiency, optimal generator parameters such as pole-arc to pole-pitch ratio and stator-slot-shoes dimension, etc. are determined with the proposed technique using Maxwell 2-D, Matlab software and the Taguchi method. The proposed double three-phase and six-phase winding configurations, which consist of six windings in the stator, can provide evenly distributed current for versatile applications regarding the voltage and current demands for practical consideration. Specifically, windings are connected in series to increase the output voltage at low wind speed, and in parallel during high wind speed to generate electricity even when either one winding fails, thereby enhancing the reliability as well. A PMSG is designed and implemented based on the proposed method. When the simulation is performed with a 6 Ω load, the output power for the double three-phase winding and six-phase winding are correspondingly 10.64 and 11.13 kW. In addition, 24 Ω load experiments show that the efficiencies of double three-phase winding and six-phase winding are 96.56% and 98.54%, respectively, verifying the proposed high performance operation.

  17. Wind Generation Participation in Power System Frequency Response: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Gevorgian, Vahan; Zhang, Yingchen

    2017-01-01

    The electrical frequency of an interconnected power system must be maintained close its nominal level at all times. Excessive under- and overfrequency excursions can lead to load shedding, instability, machine damage, and even blackouts. There is a rising concern in the electric power industry in recent years about the declining amount of inertia and primary frequency response (PFR) in many interconnections. This decline may continue due to increasing penetrations of inverter-coupled generation and the planned retirements of conventional thermal plants. Inverter-coupled variable wind generation is capable of contributing to PFR and inertia with a response that is different from that of conventional generation. It is not yet entirely understood how such a response will affect the system at different wind power penetration levels. The modeling work presented in this paper evaluates the impact of wind generation's provision of these active power control strategies on a large, synchronous interconnection. All simulations were conducted on the U.S. Western Interconnection with different levels of instantaneous wind power penetrations (up to 80%). The ability of wind power plants to provide PFR - and a combination of synthetic inertial response and PFR - significantly improved the frequency response performance of the system.

  18. A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

    Directory of Open Access Journals (Sweden)

    R. L. Balthazor

    Full Text Available A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs and associated travelling ionospheric disturbances (TIDs originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the 'fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs first interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex effects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic field lines by the neutral air pressure wave.

  19. Evidence for Gravity Wave Seeding of Convective Ionosphere Storms Initiated by Deep Troposphere Convection

    Science.gov (United States)

    Kelley, M. C.; Pfaff, R. F., Jr.; Dao, E. V.; Holzworth, R. H., II

    2014-12-01

    With the increase in solar activity, the Communications/Outage Forecast System satellite (C/NOFS) now goes below the F peak. As such, we now can study the development of Convective Ionospheric Storms (CIS) and, most importantly, large-scale seeding of the low growth-rate Rayleigh-Taylor (R-T) instability. Two mechanisms have been suggested for such seeding: the Collisional Kelvin-Helmholtz Instability (CKHI) and internal atmospheric gravity waves. A number of observations have shown that the spectrum of fully developed topside structures peaks at 600 km and extends to over 1000 km. These structures are exceedingly difficult to explain by CKHI. Here we show that sinusoidal plasma oscillations on the bottomside during daytime develop classical R-T structures on the nightside with the background 600 km structure still apparent. In two case studies, thunderstorm activity was observed east of the sinusoidal features in the two hours preceding the C/NOFS passes. Thus, we argue that convective tropospheric storms are a likely source of these sinusoidal features.

  20. Gravity Wave Dynamics in a Mesospheric Inversion Layer: 2. Instabilities, Turbulence, Fluxes, and Mixing

    Science.gov (United States)

    Fritts, David C.; Wang, Ling; Laughman, Brian; Lund, Thomas S.; Collins, Richard L.

    2018-01-01

    A companion paper by Fritts, Laughman, et al. (2017) employed an anelastic numerical model to explore the dynamics of gravity waves (GWs) encountering a mesospheric inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. That study revealed that MIL responses, including GW transmission, reflection, and instabilities, are sensitive functions of GW parameters. This paper expands on two of the Fritts, Laughman, et al. (2017) simulations to examine GW instability dynamics and turbulence in the MIL; forcing of the mean wind and stability environments by GW, instability, and turbulence fluxes; and associated heat and momentum transports. These direct numerical simulations resolve turbulence inertial-range scales and yield the following results: GW breaking and turbulence in the MIL occur below where they would otherwise, due to enhancements of GW amplitudes and shears in the MIL. 2-D GW and instability heat and momentum fluxes are 20-30 times larger than 3-D instability and turbulence fluxes. Mean fields are driven largely by 2-D GW and instability dynamics rather than 3-D instabilities and turbulence. 2-D and 3-D heat fluxes in regions of strong turbulence yield small departures from initial T(z) and N2(z) profiles, hence do not yield nearly adiabatic "mixed" layers. Our MIL results are consistent with the relation between the turbulent vertical velocity variance and energy dissipation rate proposed by Weinstock (1981) for the limited intervals evaluated.

  1. Electronics for the IBM gravity wave detector. Concept, implementation, and experience

    International Nuclear Information System (INIS)

    Levine, J.L.; Garwin, R.L.

    1975-01-01

    The apparatus - antenna, transducer, signal processor, and calibrator - was designed to settle the question of the existence of gravity waves at 1.7kHz of the numbers and intensities claimed at the time (end-1971). The design criteria were: modest sensitivity, sensitivity independent of signal arrival time and state of excitation of the antenna, absolute calibration with pulsed mechanical excitation of the antenna, full simulation of the apparatus, hands-off computer analysis with every point published. It was recognized that a single bar would ultimately be limited by some Boltzmann distribution of noise at sub-thermal temperature, and that such an ideal antenna would be equivalent to an ideal coincidence pair of antennas, each of half the mass. Transducer, amplifier, signal processor, and programming were all done by the experimenters in order to reduce the cycle time for introducing improvements. Before the antenna and amplifier were ready, the processing algorithms were developed and tested with digitally-simulated antenna output, and many problems avoided. Any excess local noise proved to be sufficiently infrequent so that the single antenna could negate claims by Weber of the detection of gravitational radiation. The computer processing obviated the need for temperature control of the antenna or for tracking of the bar resonant frequency with the reference oscillator

  2. Axisymmetric capillary-gravity waves at the interface of two viscous, immiscible fluids - Initial value problem

    Science.gov (United States)

    Farsoiya, Palas Kumar; Dasgupta, Ratul

    2017-11-01

    When the interface between two radially unbounded, viscous fluids lying vertically in a stable configuration (denser fluid below) at rest, is perturbed, radially propagating capillary-gravity waves are formed which damp out with time. We study this process analytically using a recently developed linearised theory. For small amplitude initial perturbations, the analytical solution to the initial value problem, represented as a linear superposition of Bessel modes at time t = 0 , is found to agree very well with results obtained from direct numerical simulations of the Navier-Stokes equations, for a range of initial conditions. Our study extends the earlier work by John W. Miles who studied this initial value problem analytically, taking into account, a single viscous fluid only. Implications of this study for the mechanistic understanding of droplet impact into a deep pool, will be discussed. Some preliminary, qualitative comparison with experiments will also be presented. We thank SERB Dept. Science & Technology, Govt. of India, Grant No. EMR/2016/000830 for financial support.

  3. Diagnosis of tropical cyclone activity through gravity wave energy density in the southwest Indian Ocean

    Science.gov (United States)

    Ibrahim, C.; Chane-Ming, F.; Barthe, C.; Kuleshov, Y.

    2010-05-01

    Tropical cyclone (TC) activity is diagnosed through convective gravity waves (GWs) observed in the upper troposphere (UT)/lower stratosphere (LS) above Tromelin island (15.53°S, 54.31°E) in the tropical southwest Indian Ocean. Monthly and weekly GW total energy densities derived from daily GPS windsonde data are compared with Outgoing Longwave Radiation (OLR) and TC hours in the vicinity of Tromelin. A relationship between GW energy density and TC activity is observed in the LS, for the TC season 2001/2002. Moreover TCs (local convection) produce GWs with total energy density mostly higher (lower) than 12 J kg-1. A 10-season climatology (1997/1998-2006/2007) confirms that large values of GW total energy density in the LS are associated with weak values of OLR during the TC passage. Monthly total, kinetic and potential GW energy densities within 2000 km radius of Tromelin can be estimated using linear relationships with TC hours for a threshold of above 6 TC days per month. A linear relationship also exists between weekly GW total energy density in the LS and the activity of intense TCs above a threshold of 2 TC days per week within 1000 km radius of Tromelin. GW energy density in the LS could be used as a possible index to investigate TC activity in the UT/LS.

  4. Spectral decomposition of internal gravity wave sea surface height in global models

    Science.gov (United States)

    Savage, Anna C.; Arbic, Brian K.; Alford, Matthew H.; Ansong, Joseph K.; Farrar, J. Thomas; Menemenlis, Dimitris; O'Rourke, Amanda K.; Richman, James G.; Shriver, Jay F.; Voet, Gunnar; Wallcraft, Alan J.; Zamudio, Luis

    2017-10-01

    Two global ocean models ranging in horizontal resolution from 1/12° to 1/48° are used to study the space and time scales of sea surface height (SSH) signals associated with internal gravity waves (IGWs). Frequency-horizontal wavenumber SSH spectral densities are computed over seven regions of the world ocean from two simulations of the HYbrid Coordinate Ocean Model (HYCOM) and three simulations of the Massachusetts Institute of Technology general circulation model (MITgcm). High wavenumber, high-frequency SSH variance follows the predicted IGW linear dispersion curves. The realism of high-frequency motions (>0.87 cpd) in the models is tested through comparison of the frequency spectral density of dynamic height variance computed from the highest-resolution runs of each model (1/25° HYCOM and 1/48° MITgcm) with dynamic height variance frequency spectral density computed from nine in situ profiling instruments. These high-frequency motions are of particular interest because of their contributions to the small-scale SSH variability that will be observed on a global scale in the upcoming Surface Water and Ocean Topography (SWOT) satellite altimetry mission. The variance at supertidal frequencies can be comparable to the tidal and low-frequency variance for high wavenumbers (length scales smaller than ˜50 km), especially in the higher-resolution simulations. In the highest-resolution simulations, the high-frequency variance can be greater than the low-frequency variance at these scales.

  5. Diurnal variation in gravity wave activity at low and middle latitudes

    Directory of Open Access Journals (Sweden)

    V. F. Andrioli

    2013-11-01

    Full Text Available We employ a modified composite day extension of the Hocking (2005 analysis method to study gravity wave (GW activity in the mesosphere and lower thermosphere using 4 meteor radars spanning latitudes from 7° S to 53.6° S. Diurnal and semidiurnal modulations were observed in GW variances over all sites. Semidiurnal modulation with downward phase propagation was observed at lower latitudes mainly near the equinoxes. Diurnal modulations occur mainly near solstice and, except for the zonal component at Cariri (7° S, do not exhibit downward phase propagation. At a higher latitude (SAAMER, 53.6° S these modulations are only observed in the meridional component where we can observe diurnal variation from March to May, and semidiurnal, during January, February, October (above 88 km and November. Some of these modulations with downward phase progression correlate well with wind shear. When the wind shear is well correlated with the maximum of the variances the diurnal tide has its largest amplitudes, i.e., near equinox. Correlations exhibiting variations with tidal phases suggest significant GW-tidal interactions that have different characters depending on the tidal components and possible mean wind shears. Modulations that do not exhibit phase variations could be indicative of diurnal variations in GW sources.

  6. Some characteristics of atmospheric gravity waves observed by radio-interferometry

    Directory of Open Access Journals (Sweden)

    Claude Mercier

    Full Text Available Observations of atmospheric acoustic-gravity waves (AGWs are considered through their effect on the horizontal gradient G of the slant total electron content (slant TEC, which can be directly obtained from two-dimensional radio-interferometric observations of cosmic radio-sources with the Nançay radioheligraph (2.2°E, 47.3°N. Azimuths of propagation can be deduced (modulo 180°. The total database amounts to about 800 h of observations at various elevations, local time and seasons. The main results are:

    a AGWs are partially directive, confirming our previous results.

    b The propagation azimuths considered globally are widely scattered with a preference towards the south.

    c They show a bimodal time distribution with preferential directions towards the SE during daytime and towards the SW during night-time (rather than a clockwise rotation as reported by previous authors.

    d The periods are scattered but are larger during night-time than during daytime by about 60%.

    e The effects observed with the solar radio-sources are significantly stronger than with other radio-sources (particularly at higher elevations, showing the role of the geometry in line of sight-integrated observations.

  7. Frequency variations of gravity waves interacting with a time-varying tide

    Energy Technology Data Exchange (ETDEWEB)

    Huang, C.M.; Zhang, S.D.; Yi, F.; Huang, K.M.; Gan, Q.; Gong, Y. [Wuhan Univ., Hubei (China). School of Electronic Information; Ministry of Education, Wuhan, Hubei (China). Key Lab. of Geospace Environment and Geodesy; State Observatory for Atmospheric Remote Sensing, Wuhan, Hubei (China); Zhang, Y.H. [Nanjing Univ. of Information Science and Technology (China). College of Hydrometeorolgy

    2013-11-01

    Using a nonlinear, 2-D time-dependent numerical model, we simulate the propagation of gravity waves (GWs) in a time-varying tide. Our simulations show that when aGW packet propagates in a time-varying tidal-wind environment, not only its intrinsic frequency but also its ground-based frequency would change significantly. The tidal horizontal-wind acceleration dominates the GW frequency variation. Positive (negative) accelerations induce frequency increases (decreases) with time. More interestingly, tidal-wind acceleration near the critical layers always causes the GW frequency to increase, which may partially explain the observations that high-frequency GW components are more dominant in the middle and upper atmosphere than in the lower atmosphere. The combination of the increased ground-based frequency of propagating GWs in a time-varying tidal-wind field and the transient nature of the critical layer induced by a time-varying tidal zonal wind creates favorable conditions for GWs to penetrate their originally expected critical layers. Consequently, GWs have an impact on the background atmosphere at much higher altitudes than expected, which indicates that the dynamical effects of tidal-GW interactions are more complicated than usually taken into account by GW parameterizations in global models.

  8. Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

    OpenAIRE

    Chane Ming, Fabrice; Vignelles, Damien; Jegou, Fabrice; Berthet, Gwenael; Renard, Jean-Baptiste; Gheusi, François; Kuleshov, Yuriy

    2016-01-01

    International audience; Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC), M10 meteorological global positioning system (GPS) sondes, ozonesondes, and GPS radio occultation data, are examined to identify gravity-wave (GW)-induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx (Chemistry-Aerosol Mediterranean Experiment) campaign. Observations reveal signatures of GWs with short vertical wav...

  9. Planetary and gravity wave signatures in the F region ionosphere with impact on radio propagation predictions and variability

    Czech Academy of Sciences Publication Activity Database

    Altadill, D.; Apostolov, E. M.; Boška, Josef; Laštovička, Jan; Šauli, Petra

    2004-01-01

    Roč. 47, 2/3 (2004), s. 1109-1119 ISSN 1593-5213. [Final Meeting COST271 Action. Effects of the upper atmosphere on terrestrial and Earth- space communications (EACOS). Abingdon, 26.08.2004-27.08.2004] R&D Projects: GA MŠk OC 271.10; GA ČR GA205/01/1071; GA ČR GP205/02/P077 Institutional research plan: CEZ:AV0Z3042911 Keywords : ionosphere * planetary waves * gravity waves Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.413, year: 2004

  10. Wavelet characterisation of ionospheric acoustic and gravity waves occuring during the solar eclipse of August 11, 1999

    Czech Academy of Sciences Publication Activity Database

    Šauli, Petra; Abry, P.; Boška, Josef; Duchayne, L.

    2006-01-01

    Roč. 68, 3-5 (2006), s. 586-598 ISSN 1364-6826 R&D Projects: GA ČR GP205/02/P077; GA ČR(CZ) GA205/01/1071; GA AV ČR(CZ) IAA3042102 Grant - others:CNRS(FR) 18098 Institutional research plan: CEZ:AV0Z30420517 Keywords : Solar eclipse * Acoustic-gravity waves * Vertical ionospheric sounding * Wavelet decomposition * Wave packet characterisation Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.448, year: 2006

  11. Planetary and gravity wave signatures in the F-region ionosphere with impacton radio propagation predictionsand variability

    Directory of Open Access Journals (Sweden)

    P. Sauli

    2004-06-01

    Full Text Available The aim of this work within the WP 3.1 of the COST 271 Action is the characterization of the variability introduced in the F-region ionosphere by -Planetary Wave Signatures- (PWS and -Gravity Wave Signatures- (GWS. Typical patterns of percentage of time occurrence and time duration of PWS, their climatology and main drivers, as well as their vertical and longitudinal structure have been obtained. Despite the above characterization, the spectral distribution of event duration is too broad to allow for a reasonable prediction of PWS from ionospheric measurements themselves. GWS with a regular morning/evening wave bursts and specific GWS events whose arising can be predicted have been evaluated. As above, their typical pattern of occurrence and time duration, and their vertical structure have been obtained. The latter events remain in the ionospheric variability during disturbed days while additional wave enhancements of auroral origin occur. However, both types of disturbances can be distinguished.

  12. Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater

    Science.gov (United States)

    Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

    The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches

  13. The significance of ultra-refracted surface gravity waves on sheltered coasts, with application to San Francisco Bay

    Science.gov (United States)

    Hanes, D.M.; Erikson, L.H.

    2013-01-01

    Ocean surface gravity waves propagating over shallow bathymetry undergo spatial modification of propagation direction and energy density, commonly due to refraction and shoaling. If the bathymetric variations are significant the waves can undergo changes in their direction of propagation (relative to deepwater) greater than 90° over relatively short spatial scales. We refer to this phenomenon as ultra-refraction. Ultra-refracted swell waves can have a powerful influence on coastal areas that otherwise appear to be sheltered from ocean waves. Through a numerical modeling investigation it is shown that San Francisco Bay, one of the earth's largest and most protected natural harbors, is vulnerable to ultra-refracted ocean waves, particularly southwest incident swell. The flux of wave energy into San Francisco Bay results from wave transformation due to the bathymetry and orientation of the large ebb tidal delta, and deep, narrow channel through the Golden Gate. For example, ultra-refracted swell waves play a critical role in the intermittent closure of the entrance to Crissy Field Marsh, a small restored tidal wetland located on the sheltered north-facing coast approximately 1.5 km east of the Golden Gate Bridge.

  14. Output power control of two coupled wind generators

    Directory of Open Access Journals (Sweden)

    A Boukhelifa

    2016-09-01

    Full Text Available In this paper we are interested to the power control of two wind generators coupled to the network through power converters. Every energy chain conversion is composed of a wind turbine, a gearbox, a Double Fed Induction Generator (DFIG, two PWM converters and a DC bus. The power exchange and the DC voltage are controlled by the use of proportional integral correctors. For our study, initially we have modeled all the components of the one system energy conversion, and then we have simulated its behavior using Matlab/Simulink. In another part of this paper we present the analysis of the interaction and the powerflow between the two aerogenerators following a disturbance due to wind speed on every turbine. Also we have considered a connection fault to the DC bus. In each case the assessment of power brought into play is checked. Simulation tests are established.

  15. Transient Stability Enhancement of the Power System with Wind Generation

    Directory of Open Access Journals (Sweden)

    Ashwani Kumar Chandel

    2011-08-01

    Full Text Available Transient stability analysis of a power system with wind generation has been addressed in this paper. The effects of automatic voltage regulators, power system stabilizers, and static synchronous compensators on transient stability of a power system are investigated. Various simulation results show that addition of power system stabilizer and static synchronous compensators reduce the rotor angle oscillations. However, the static synchronous compensator shows better damping characteristics and improves the stability of the wind integrated system. It has been established that the static synchronous compensator damps out the speed oscillations in the shaft of the constant speed wind turbine. A transient impact index has been proposed to prove that the static compensator damps out the rotor oscillations.

  16. Batteries for storage of wind-generated energy

    Science.gov (United States)

    Schwartz, H. J.

    1973-01-01

    Cost effectiveness characteristics of conventional-, metal gas-, and high energy alkali metal-batteries for wind generated energy storage are considered. A lead-acid battery with a power density of 20 to 30 watt/hours per pound is good for about 1500 charge-discharge cycles at a cost of about $80 per kilowatt hour. A zinc-chlorine battery that stores chlorine as solid chlorine hydrate at temperatures below 10 C eliminates the need to handle gaseous chlorine; its raw material cost are low and inexpensive carbon can be used for the chlorine electrode. This system has the best chance to replace lead-acid. Exotic alkali metal batteries are deemed too costly at the present stage of development.

  17. Optimization of Multibrid Permanent-Magnet Wind Generator Systems

    DEFF Research Database (Denmark)

    Chen, Zhe; Li, H.; Polinder, H.

    2009-01-01

    This paper investigates the cost-effective ranges of gearbox ratios and power ratings of multibrid permanent-magnet (PM) wind generator systems by using a design optimization method. First, the analytical model of a multibrid wind turbine concept consisting of a single-stage gearbox and a three......-phase radial-flux PM synchronous generator with a back-to-back power converter is presented. The design optimization is adopted with a genetic algorithm forminimizing generator system cost. To demonstrate the effectiveness of the developed electromagnetic design model, the optimization results of a 500-k......W direct-drive PM generator and a 1.5-MW multibrid PM generator with various gear ratios are, respectively, compared with those from other methods. Then, the optimal design approach is further employed for a range from 750 kW up to 10 MW. The optimization results of PM generator systems including direct...

  18. Interconnector capacity allocation in offshore grids with variable wind generation

    DEFF Research Database (Denmark)

    Schröder, Sascha Thorsten

    2013-01-01

    its generation flows only to the high-price market. Granting the high-price market income for wind generation as the opposite design option reduces congestion rents. Otherwise, compensation measures through support schemes or different balancing responsibilities may be discussed....... with onshore installations to reduce balancing demand. This is not necessarily the case if the interconnector capacity is sold through implicit or explicit auctions. Different design options are discussed and quantified for a number of examples based on Danish, Dutch, German and Norwegian power markets....... It is concluded that treating offshore generation as a single price zone within the interconnector reduces the wind operator’s ability to pool it with other generation. Furthermore, a single offshore price zone between two markets will always receive the lower spot market price of the neighbouring zones, although...

  19. Low cost infrastructure solutions for small embedded wind generators

    Energy Technology Data Exchange (ETDEWEB)

    Robb, C.

    2003-07-01

    This report gives details of a project to demonstrate novel economic solutions to increase the potential for installing small-scale embedded wind generator systems at many UK sites which have so far been dismissed as too difficult. Details are given of the first phase of the study which examined current solutions to infrastructure problems and potential techniques. The use of drilled rock anchor foundations to minimise the need for delivery of ready-mix concrete to wind turbine sites, and the use of a winch and A-frame system for erecting a wind turbine to avoid the use of cranes are discussed. The demonstration of the installation of a 50kW wind turbine on the Isle of Luing in Scotland where there is no access for cranes or larger vehicles in the second phase of the project is described. The potential for the use of these techniques on larger wind turbines is considered.

  20. Inertia-gravity wave radiation from the merging of two co-rotating vortices in the f-plane shallow water system

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, Norihiko, E-mail: nori@phys-h.keio.ac.jp [Department of Physics, Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kouhoku-ku, Yokohama, Kanagawa 223-8521 (Japan)

    2015-12-15

    Inertia-gravity wave radiation from the merging of two co-rotating vortices is investigated numerically in a rotating shallow water system in order to focus on cyclone–anticyclone asymmetry at different values of the Rossby number (Ro). A numerical study is conducted on a model using a spectral method in an unbounded domain to estimate the gravity wave flux with high accuracy. Continuous gravity wave radiation is observed in three stages of vortical flows: co-rotating of the vortices, merging of the vortices, and unsteady motion of the merged vortex. A cyclone–anticyclone asymmetry appears at all stages at smaller Ro (≤20). Gravity waves from anticyclones are always larger than those from cyclones and have a local maximum at smaller Ro (∼2) compared with that for an idealized case of a co-rotating vortex pair with a constant rotation rate. The source originating in the Coriolis acceleration has a key role in cyclone–anticyclone asymmetry in gravity waves. An additional important factor is that at later stages, the merged axisymmetric anticyclone rotates faster than the elliptical cyclone due to the effect of the Rossby deformation radius, since a rotation rate higher than the inertial cutoff frequency is required to radiate gravity waves.

  1. The internal gravity wave spectrum in two high-resolution global ocean models

    Science.gov (United States)

    Arbic, B. K.; Ansong, J. K.; Buijsman, M. C.; Kunze, E. L.; Menemenlis, D.; Müller, M.; Richman, J. G.; Savage, A.; Shriver, J. F.; Wallcraft, A. J.; Zamudio, L.

    2016-02-01

    We examine the internal gravity wave (IGW) spectrum in two sets of high-resolution global ocean simulations that are forced concurrently by atmospheric fields and the astronomical tidal potential. We analyze global 1/12th and 1/25th degree HYCOM simulations, and global 1/12th, 1/24th, and 1/48th degree simulations of the MITgcm. We are motivated by the central role that IGWs play in ocean mixing, by operational considerations of the US Navy, which runs HYCOM as an ocean forecast model, and by the impact of the IGW continuum on the sea surface height (SSH) measurements that will be taken by the planned NASA/CNES SWOT wide-swath altimeter mission. We (1) compute the IGW horizontal wavenumber-frequency spectrum of kinetic energy, and interpret the results with linear dispersion relations computed from the IGW Sturm-Liouville problem, (2) compute and similarly interpret nonlinear spectral kinetic energy transfers in the IGW band, (3) compute and similarly interpret IGW contributions to SSH variance, (4) perform comparisons of modeled IGW kinetic energy frequency spectra with moored current meter observations, and (5) perform comparisons of modeled IGW kinetic energy vertical wavenumber-frequency spectra with moored observations. This presentation builds upon our work in Muller et al. (2015, GRL), who performed tasks (1), (2), and (4) in 1/12th and 1/25th degree HYCOM simulations, for one region of the North Pacific. New for this presentation are tasks (3) and (5), the inclusion of MITgcm solutions, and the analysis of additional ocean regions.

  2. Simulation and Observation of Acoustic-Gravity Waves in the Ionosphere

    Science.gov (United States)

    Kunitsyn, Viacheslav; Andreeva, Elena; Krysanov, Boris; Nesterov, Ivan

    Atmospheric and ionospheric perturbations associated with the acoustic-gravity waves (AGW) with typical frequencies of a few hertz -millihertz are considered. These events may be caused by the influence from space and atmosphere as well as by oscillations of the Earth surface and other near-surface phenomena. The surface sources include long-period oscillations of the Earth's surface, earthquakes, explosions, thermal heating, seisches and tsunami waves. The wavelike phenomena manifest themself as travelling disturbances of air (in the atmosphere) and of electron density (in the ionosphere). Travelling ionospheric disturbances (TIDs) are well detected by radio physical methods. AGW generation by near-surface sources is modeled by the numerical solution of the equation of geophysical fluid dynamics for different sources in two-dimensional non-linear dissipative compressible atmosphere. The numerical calculations are based on the FCT (Flux Corrected Transport) technique of the second order accuracy in time and space. Different scenarios of AGW generation are analyzed. The AGW caused by the surface sources within a few hertz-millihertz frequency band appear at the altitudes of middle atmosphere and ionosphere as the disturbances with typical scales from a few kilometers to several hundreds kilometers. Such structures can be successfully monitored by the methods of satellite radio tomography (RT). For the purposes of RT diagnostics of such disturbances, low-orbiting navigational satellites like Transit and Tsikada and high-orbiting navigation systems GPS/GLONASS are used. The results of numerical modeling of AGW generation by the surface sources are compared with the data of RT sounding. Also, generation of AGW by volumetric sources such as particle precipitation, rocket launching, heating by high-frequency radiation and other are considered. The obtained results proved the capability of RT methods of detecting and distinguishing between TIDs caused by AGW generated by

  3. Vertical structure of pore pressure under surface gravity waves on a steep, megatidal, mixed sand-gravel-cobble beach

    Science.gov (United States)

    Guest, Tristan B.; Hay, Alex E.

    2017-01-01

    The vertical structure of surface gravity wave-induced pore pressure is investigated within the intertidal zone of a natural, steeply sloping, megatidal, mixed sand-gravel-cobble beach. Results from a coherent vertical array of buried pore pressure sensors are presented in terms of signal phase lag and attenuation as functions of oscillatory forcing frequency and burial depth. Comparison of the observations with the predictions of a theoretical poro-elastic bed response model indicates that the large observed phase lags and attenuation are attributable to interstitial trapped air. In addition to the dependence on entrapped air volume, the pore pressure phase and attenuation are shown to be sensitive to the hydraulic conductivity of the sediment, to the changing mean water depth during the tidal cycle, and to the redistribution/rearrangement of beach face material by energetic wave action during storm events. The latter result indicates that the effects on pore pressure of sediment column disturbance during instrument burial can persist for days to weeks, depending upon wave forcing conditions. Taken together, these results raise serious questions as to the practicality of using pore pressure measurements to estimate the kinematic properties of surface gravity waves on steep, mixed sand-gravel beaches.

  4. Analysis of ALOHA-93 Campaign Data in Terms of Gravity and Tidal Wave Modes: Considerations on the Jet Stream as a Gravity-Wave Source

    National Research Council Canada - National Science Library

    Tuan, T

    1999-01-01

    .... The second phenomenon is the simultaneous observation of OH airglow wave structure propagating along an azimuth of 340 deg with a phase speed of 35 m/s, a horizontal wavelength of 80 km remaining...

  5. influence of gravity

    Directory of Open Access Journals (Sweden)

    Animesh Mukherjee

    1991-01-01

    Full Text Available Based upon Biot's [1965] theory of initial stresses of hydrostatic nature produced by the effect of gravity, a study is made of surface waves in higher order visco-elastic media under the influence of gravity. The equation for the wave velocity of Stonely waves in the presence of viscous and gravitational effects is obtained. This is followed by particular cases of surface waves including Rayleigh waves and Love waves in the presence of viscous and gravity effects. In all cases the wave-velocity equations are found to be in perfect agreement with the corresponding classical results when the effects of gravity and viscosity are neglected.

  6. Long-term MST radar observations of vertical wave number spectra of gravity waves in the tropical troposphere over Gadanki (13.5° N, 79.2° E: comparison with model spectra

    Directory of Open Access Journals (Sweden)

    S. Vijaya Bhaskara Rao

    2008-06-01

    Full Text Available The potential utility of Mesosphere-Stratosphere-Troposphere (MST radar measurements of zonal, meridional and vertical winds for divulging the gravity wave vertical wave number spectra is discussed. The data collected during the years 1995–2004 are used to obtain the mean vertical wave number spectra of gravity wave kinetic energy in the tropical troposphere over Gadanki (13.5° N, 79.2° E. First, the climatology of 3-dimensional wind components is developed using ten years of radar observations, for the first time, over this latitude. This climatology brought out the salient features of background tropospheric winds over Gadanki. Further, using the second order polynomial fit as background, the day-to-day wind anomalies are estimated. These wind anomalies in the 4–14 km height regions are used to estimate the profiles of zonal, meridional and vertical kinetic energy per unit mass, which are then used to estimate the height profile of total kinetic energy. Finally, the height profiles of total kinetic energy are subjected to Fourier analysis to obtain the monthly mean vertical wave number spectra of gravity wave kinetic energy. The monthly mean vertical wave number spectra are then compared with a saturation spectrum predicted by gravity wave saturation theory. A slope of 5/3 is used for the model gravity wave spectrum estimation. In general, the agreement is good during all the months. However, it is noticed that the model spectrum overestimates the PSD at lower vertical wave numbers and underestimates it at higher vertical wave numbers, which is consistently observed during all the months. The observed discrepancies are attributed to the differences in the slopes of theoretical and observed gravity wave spectra. The slopes of the observed vertical wave number spectra are estimated and compared with the model spectrum slope, which are in good agreement. The estimated slopes of the observed monthly vertical wave number spectra are in the

  7. Satellite Detection of Orographic Gravity-wave Activity in the Winter Subtropical Stratosphere over Australia and Africa

    Science.gov (United States)

    Eckermann, S. D.; Wu, D. L.

    2012-01-01

    Orographic gravity-wave (OGW) parameterizations in models produce waves over subtropical mountain ranges in Australia and Africa that propagate into the stratosphere during austral winter and deposit momentum, affecting weather and climate. Satellite sensors have measured stratospheric GWs for over a decade, yet find no evidence of these waves. So are parameterizations failing here? Here we argue that the short wavelengths of subtropical OGWs place them near or below the detection limits of satellite sensors. To test this hypothesis, we reanalyze nine years of stratospheric radiances from the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite during austral winter, applying new averaging techniques to maximize signal-to-noise and improve thresholds for OGW detection. Deep climatological enhancements in stratospheric OGW variance over specific mountain ranges in Australia and southern Africa are revealed for the first time, which exhibit temporal and vertical variations consistent with predicted OGW responses to varying background winds.

  8. Wind Generator & Biomass No-draft Gasification Hybrid

    Science.gov (United States)

    Hein, Matthew R.

    The premise of this research is that underutilized but vast intermittent renewable energy resources, such as wind, can become more market competitive by coupling with storable renewable energy sources, like biomass; thereby creating a firm capacity resource. Specifically, the Midwest state of South Dakota has immense wind energy potential that is not used because of economic and logistic barriers of electrical transmission or storage. Coupling the state's intermittent wind resource with another of the state's energy resources, cellulosic non-food biomass, by using a wind generator and no-draft biomass gasification hybrid system will result in a energy source that is both firm and storable. The average energy content of common biomass feedstock was determined, 14.8 MJ/kg (7.153 Btu/lb), along with the assumed typical biomass conversion efficiency of the no-draft gasifier, 65%, so that an average electrical energy round trip efficiency (RTE) of 214% can be expected (i.e. One unit of wind electrical energy can produce 2.14 kWh of electrical energy stored as syngas.) from a wind generator and no-draft biomass gasification system. Wind characteristics are site specific so this analysis utilizes a synthetic wind resource to represent a statistically sound gross representation of South Dakota's wind regime based on data from the Wind Resource Assessment Network (WRAN) locations. A synthetic wind turbine generated from common wind turbine power curves and scaled to 1-MW rated capacity was utilized for this analysis in order to remove equipment bias from the results. A standard 8,760-hour BIN Analysis model was constructed within HOMER, powerful simulation software developed by the National Renewable Energy Laboratory (NREL) to model the performance of renewable power systems. It was found that the optimum configuration on a per-megawatt-transmitted basis required a wind generator (wind farm) rated capacity of 3-MW with an anticipated annual biomass feedstock of 26,132 GJ

  9. Acoustic-gravity waves generated by atmospheric and near-surface sources

    Science.gov (United States)

    Kunitsyn, Viacheslav E.; Kholodov, Alexander S.; Krysanov, Boris Yu.; Andreeva, Elena S.; Nesterov, Ivan A.; Vorontsov, Artem M.

    2013-04-01

    Numerical simulation of the acoustic-gravity waves (AGW) generated by long-period oscillations of the Earth's (oceanic) surface, earthquakes, explosions, thermal heating, seiches, and tsunami is carried out. Wavelike disturbances are quite frequent phenomena in the atmosphere and ionosphere. These events can be caused by the impacts from space and atmosphere, by oscillations of the Earth'as surface and other near-surface events. These wavelike phenomena in the atmosphere and ionosphere appear as the alternating areas of enhanced and depleted density (in the atmosphere) or electron concentration (in the ionosphere). In the paper, AGW with typical frequencies of a few hertz - millihertz are analyzed. AGW are often observed after the atmospheric perturbations, during the earthquakes, and some time (a few days to hours) in advance of the earthquakes. Numerical simulation of the generation of AGW by long-period oscillations of the Earth's and oceanic surface, earthquakes, explosions, thermal heating, seiches, and tsunami is carried out. The AGW generated by the near-surface phenomena within a few hertz-millihertz frequency range build up at the mid-atmospheric and ionospheric altitudes, where they assume their typical spatial scales of the order of a few hundred kilometers. Oscillations of the ionospheric plasma within a few hertz-millihertz frequency range generate electromagnetic waves with corresponding frequencies as well as travelling ionospheric irregularities (TIDs). Such structures can be successfully monitored using satellite radio tomography (RT) techniques. For the purposes of RT diagnostics, 150/400 MHz transmissions from low-orbiting navigational satellites flying in polar orbits at the altitudes of about 1000 km as well as 1.2-1.5 GHz signals form high-orbiting (orbital altitudes about 20000 km) navigation systems like GPS/GLONASS are used. The results of experimental studies on generation of wavelike disturbances by particle precipitation are presented

  10. Three-Dimensional Acoustic Propagation Through Shallow Water Internal, Surface Gravity and Bottom Sediment Waves

    Science.gov (United States)

    2011-09-01

    and large ( sand waves) transverse bedforms [21]. Note that in the literature the term ” sand dunes ” can refer to both sand waves and megaripples...Bottom ripples have wave- lengths of centimeters, whereas the length scales of megaripples and sand waves are tens and even hundreds of meters. The last...number. Full field numerical modeling of low frequency sound propaga- tion through large sand waves located on a sloped bottom was performed using the

  11. Lightweight MgB2 superconducting 10 MW wind generator

    Science.gov (United States)

    Marino, I.; Pujana, A.; Sarmiento, G.; Sanz, S.; Merino, J. M.; Tropeano, M.; Sun, J.; Canosa, T.

    2016-02-01

    The offshore wind market demands a higher power rate and more reliable turbines in order to optimize capital and operational costs. The state-of-the-art shows that both geared and direct-drive conventional generators are difficult to scale up to 10 MW and beyond due to their huge size and weight. Superconducting direct-drive wind generators are considered a promising solution to achieve lighter weight machines. This work presents an innovative 10 MW 8.1 rpm direct-drive partial superconducting generator using MgB2 wire for the field coils. It has a warm iron rotor configuration with the superconducting coils working at 20 K while the rotor core and the armature are at ambient temperature. A cooling system based on cryocoolers installed in the rotor extracts the heat from the superconducting coils by conduction. The generator's main parameters are compared against a permanent magnet reference machine, showing a significant weight and size reduction. The 10 MW superconducting generator concept will be experimentally validated with a small-scale magnetic machine, which has innovative components such as superconducting coils, modular cryostats and cooling systems, and will have similar size and characteristics as the 10 MW generator.

  12. Performance evaluation of stand alone hybrid PV-wind generator

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, M. N. M.; Saharuddin, N. Z.; Sulaima, M. F.; Jali, Mohd Hafiz; Bukhari, W. M.; Bohari, Z. H. [Faculty of Electrical Engineering, Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, 76100 Melaka (Malaysia); Yahaya, M. S. [Faculty of Engineering Technology, Universiti Teknikal Malaysia Melaka (UTeM), Hang Tuah Jaya, 76100 Melaka (Malaysia)

    2015-05-15

    This paper presents the performance evaluation of standalone hybrid system on Photovoltaic (PV)-Wind generator at Faculty of Electrical Engineering (FKE), UTeM. The hybrid PV-Wind in UTeM system is combining wind turbine system with the solar system and the energy capacity of this hybrid system can generate up to charge the battery and supply the LED street lighting load. The purpose of this project is to evaluate the performance of PV-Wind hybrid generator. Solar radiation meter has been used to measure the solar radiation and anemometer has been used to measure the wind speed. The effectiveness of the PV-Wind system is based on the various data that has been collected and compared between them. The result shows that hybrid system has greater reliability. Based on the solar result, the correlation coefficient shows strong relationship between the two variables of radiation and current. The reading output current followed by fluctuate of solar radiation. However, the correlation coefficient is shows moderate relationship between the two variables of wind speed and voltage. Hence, the wind turbine system in FKE show does not operate consistently to produce energy source for this hybrid system compare to PV system. When the wind system does not fully operate due to inconsistent energy source, the other system which is PV will operate and supply the load for equilibrate the extra load demand.

  13. Fuzzy logic based variable speed wind generation system

    Energy Technology Data Exchange (ETDEWEB)

    Simoes, M.G. [Sao Paulo Univ., SP (Brazil). Escola Politecnica. PMC - Mecatronica; Bose, B.K. [Tennessee Univ., Knoxville, TN (United States). Dept. of Electrical Engineering; Spiegel, Ronal J. [Environmental Protection Agency, Research Triangle Park, NC (United States). Air and Energy Engineering Research Lab.

    1996-12-31

    This work demonstrates the successful application of fuzzy logic to enhance the performance and control of a variable speed wind generation system. A maximum power point tracker control is performed with three fuzzy controllers, without wind velocity measurement, and robust to wind vortex and turbine torque ripple. A squirrel cage induction generator feeds the power to a double-sided PWM converter system which pumps the power to a utility grid or supplies to an autonomous system. The fuzzy logic controller FLC-1 searches on-line the generator speed so that the aerodynamic efficiency of the wind turbine is optimized. A second fuzzy controller FLC-2 programs the machine flux by on-line search so as to optimize the machine-converter system wind vortex. Detailed analysis and simulation studies were performed for development of the control strategy and fuzzy algorithms, and a DSP TMS320C30 based hardware with C control software was built for the performance evaluation of a laboratory experimental set-up. The theoretical development was fully validated and the system is ready to be reproduced in a higher power installation. (author) 7 refs., 3 figs., 1 tab.

  14. Performance evaluation of stand alone hybrid PV-wind generator

    Science.gov (United States)

    Nasir, M. N. M.; Saharuddin, N. Z.; Sulaima, M. F.; Jali, Mohd Hafiz; Bukhari, W. M.; Bohari, Z. H.; Yahaya, M. S.

    2015-05-01

    This paper presents the performance evaluation of standalone hybrid system on Photovoltaic (PV)-Wind generator at Faculty of Electrical Engineering (FKE), UTeM. The hybrid PV-Wind in UTeM system is combining wind turbine system with the solar system and the energy capacity of this hybrid system can generate up to charge the battery and supply the LED street lighting load. The purpose of this project is to evaluate the performance of PV-Wind hybrid generator. Solar radiation meter has been used to measure the solar radiation and anemometer has been used to measure the wind speed. The effectiveness of the PV-Wind system is based on the various data that has been collected and compared between them. The result shows that hybrid system has greater reliability. Based on the solar result, the correlation coefficient shows strong relationship between the two variables of radiation and current. The reading output current followed by fluctuate of solar radiation. However, the correlation coefficient is shows moderate relationship between the two variables of wind speed and voltage. Hence, the wind turbine system in FKE show does not operate consistently to produce energy source for this hybrid system compare to PV system. When the wind system does not fully operate due to inconsistent energy source, the other system which is PV will operate and supply the load for equilibrate the extra load demand.

  15. Performance evaluation of stand alone hybrid PV-wind generator

    International Nuclear Information System (INIS)

    Nasir, M. N. M.; Saharuddin, N. Z.; Sulaima, M. F.; Jali, Mohd Hafiz; Bukhari, W. M.; Bohari, Z. H.; Yahaya, M. S.

    2015-01-01

    This paper presents the performance evaluation of standalone hybrid system on Photovoltaic (PV)-Wind generator at Faculty of Electrical Engineering (FKE), UTeM. The hybrid PV-Wind in UTeM system is combining wind turbine system with the solar system and the energy capacity of this hybrid system can generate up to charge the battery and supply the LED street lighting load. The purpose of this project is to evaluate the performance of PV-Wind hybrid generator. Solar radiation meter has been used to measure the solar radiation and anemometer has been used to measure the wind speed. The effectiveness of the PV-Wind system is based on the various data that has been collected and compared between them. The result shows that hybrid system has greater reliability. Based on the solar result, the correlation coefficient shows strong relationship between the two variables of radiation and current. The reading output current followed by fluctuate of solar radiation. However, the correlation coefficient is shows moderate relationship between the two variables of wind speed and voltage. Hence, the wind turbine system in FKE show does not operate consistently to produce energy source for this hybrid system compare to PV system. When the wind system does not fully operate due to inconsistent energy source, the other system which is PV will operate and supply the load for equilibrate the extra load demand

  16. VLP seismicity from resonant modes of acoustic-gravity waves in a conduit-crack system filled with multiphase magma

    Science.gov (United States)

    Liang, C.; Prochnow, B. N.; OReilly, O. J.; Dunham, E. M.; Karlstrom, L.

    2016-12-01

    Oscillation of magma in volcanic conduits connected to cracks (dikes and sills) has been suggested as an explanation for very long period (VLP) seismic signals recorded at active basaltic volcanoes such as. Kilauea, Hawaii, and Erebus, Antarctica. We investigate the VLP seismicity using a linearized model for waves in and associated eigenmodes of a coupled conduit-crack system filled with multiphase magma, an extension of the Karlstrom and Dunham (2016) model for acoustic-gravity waves in volcanic conduits. We find that the long period surface displacement (as recorded on broadband seismometers) is dominated by opening/closing of the crack rather than the deformation of the conduit conduit walls. While the fundamental eigenmode is sensitive to the fluid properties and the geometry of the magma plumbing system, a closer scrutiny of various resonant modes reveals that the surface displacement is often more sensitive to higher modes. Here we present a systematic analysis of various long period acoustic-gravity wave resonant modes of a coupled conduit-crack system that the surface displacement is most sensitive to. We extend our previous work on a quasi-one-dimensional conduit model with inviscid magma to a more general axisymmetric conduit model that properly accounts for viscous boundary layers near the conduit walls, based on the numerical method developed by Prochnow et al. (submitted to Computers and Fluids, 2016). The surface displacement is dominated by either the fundamental or higher eigenmodes, depending on magma properties and the geometry of conduit and crack. An examination of the energetics of these modes reveals the complex interplay of different restoring forces (magma compressibility in the conduit, gravity, and elasticity of the crack) driving the VLP oscillations. Both nonequilibrium bubble growth and resorption and viscosity contribute to the damping of VLP signals. Our models thus provide a means to infer properties of open-vent basaltic volcanoes

  17. Massive gravity and the suppression of anisotropies and gravitational waves in a matter-dominated contracting universe

    Science.gov (United States)

    Lin, Chunshan; Quintin, Jerome; Brandenberger, Robert H.

    2018-01-01

    We consider a modified gravity model with a massive graviton, but which nevertheless only propagates two gravitational degrees of freedom and which is free of ghosts. We show that non-singular bouncing cosmological background solutions can be generated. In addition, the mass term for the graviton prevents anisotropies from blowing up in the contracting phase and also suppresses the spectrum of gravitational waves compared to that of the scalar cosmological perturbations. This addresses two of the main problems of the matter bounce scenario.

  18. UA-ICON - A non-hydrostatic global model for studying gravity waves from the troposphere to the thermosphere

    Science.gov (United States)

    Borchert, Sebastian; Zängl, Günther; Baldauf, Michael; Zhou, Guidi; Schmidt, Hauke; Manzini, Elisa

    2017-04-01

    In numerical weather prediction as well as climate simulations, there are ongoing efforts to raise the upper model lid, acknowledging the possible influence of middle and upper atmosphere dynamics on tropospheric weather and climate. As the momentum deposition of gravity waves (GWs) is responsible for key features of the large scale flow in the middle and upper atmosphere, the upward model extension has put GWs in the focus of atmospheric research needs. The Max Planck Institute for Meteorology (MPI-M) and the German Weather Service (DWD) have been developing jointly the non-hydrostatic global model ICON (Zängl et al, 2015) which features a new dynamical core based on an icosahedral grid. The extension of ICON beyond the mesosphere, where most GWs deposit their momentum, requires, e.g., relaxing the shallow-atmosphere and other traditional approximations as well as implementing additional physical processes that are important to the upper atmosphere. We would like to present aspects of the model development and its evaluation, and first results from a simulation of a period of the DEEPWAVE campaign in New Zealand in 2014 (Fritts et al, 2016) using grid nesting up to a horizontal mesh size of about 1.25 km. This work is part of the research unit: Multi-Scale Dynamics of Gravity Waves (MS-GWaves: sub-project GWING, https://ms-gwaves.iau.uni-frankfurt.de/index.php), funded by the German Research Foundation. Fritts, D.C. and Coauthors, 2016: "The Deep Propagating Gravity Wave Experiment (DEEPWAVE): An airborne and ground-based exploration of gravity wave propagation and effects from their sources throughout the lower and middle atmosphere". Bull. Amer. Meteor. Soc., 97, 425 - 453, doi:10.1175/BAMS-D-14-00269.1 Zängl, G., Reinert, D., Ripodas, P., Baldauf, M., 2015: "The ICON (ICOsahedral Non-hydrostatic) modelling framework of DWD and MPI-M: Description of the non-hydrostatic dynamical core". Quart. J. Roy. Met. Soc., 141, 563 - 579, doi:10.1002/qj.2378

  19. A solution of nonlinear equation for the gravity wave spectra from Adomian decomposition method: a first approach

    Directory of Open Access Journals (Sweden)

    Antonio Gledson Goulart

    2013-12-01

    Full Text Available In this paper, the equation for the gravity wave spectra in mean atmosphere is analytically solved without linearization by the Adomian decomposition method. As a consequence, the nonlinear nature of problem is preserved and the errors found in the results are only due to the parameterization. The results, with the parameterization applied in the simulations, indicate that the linear solution of the equation is a good approximation only for heights shorter than ten kilometers, because the linearization the equation leads to a solution that does not correctly describe the kinetic energy spectra.

  20. DEEPWAVE Initial Investigation of Mesospheric Gravity Wave Signatures Generated by Variable Orographic Forcing Over Lauder Station (45°S). New Zealand

    Science.gov (United States)

    Criddle, N.; Taylor, M. J.; Pautet, P. D.; Zhao, Y.

    2014-12-01

    DEEPWAVE is a new international collaborative research program focused on identifying, characterizing, and predicting the generation and propagation of deeply propagating atmospheric gravity waves from the Earth's surface up to ̴100 km altitude and beyond. An extended series of coordinated airborne and ground-based measurements were recently conducted from New Zealand's South Island to investigate gravity wave forcing during the winter months when strong North-Westerly winds are known to generate gravity waves capable of penetrating well into the stratosphere. As part of this collaborative effort the Atmospheric Imaging Lab at Utah State University (USU) deployed and operated an Advanced Mesospheric Temperature Mapper (AMTM) at the National Institute for Water and Atmosphere (NIWA) Lauder research station, NZ (45°S 169°E). In the lee of the Southern Alps, Lauder is well positioned for measuring a broad spectrum of gravity waves launched from south island orography and from other meteorological sources. The AMTM is uniquely capable of mapping the wave-induced temperature perturbations to investigate the two-dimensional gravity wave field with high temporal ( ̴10 sec) and high temperature precision ( ̴1-2 K in 30 sec). High-quality infrared image measurements of the OH (3,1) band emission layer (altitude ̴ 87 km) were made nightly from May 31 to July 22, 2014. The DEEPWAVE program has been a resounding success and over 42 nights of data were obtained at Lauder with distinct mesospheric mountain wave signatures recorded there in OH intensity, and in temperatures for the first time. In this poster we provide a summary of the AMTM data set from Lauder, complemented by data from coincident airborne over-flights where appropriate, and we present initial results characterizing the mesopause gravity wave field under varying orographic forcings. We thank the NSF for sponsoring this research program.

  1. Dynamical influence of gravity waves generated by the Vestfjella Mountains in Antarctica: radar observations, fine-scale modelling and kinetic energy budget analysis

    Directory of Open Access Journals (Sweden)

    Joel Arnault

    2012-02-01

    Full Text Available Gravity waves generated by the Vestfjella Mountains (in western Droning Maud Land, Antarctica, southwest of the Finnish/Swedish Aboa/Wasa station have been observed with the Moveable atmospheric radar for Antarctica (MARA during the SWEDish Antarctic Research Programme (SWEDARP in December 2007/January 2008. These radar observations are compared with a 2-month Weather Research Forecast (WRF model experiment operated at 2 km horizontal resolution. A control simulation without orography is also operated in order to separate unambiguously the contribution of the mountain waves on the simulated atmospheric flow. This contribution is then quantified with a kinetic energy budget analysis computed in the two simulations. The results of this study confirm that mountain waves reaching lower-stratospheric heights break through convective overturning and generate inertia gravity waves with a smaller vertical wavelength, in association with a brief depletion of kinetic energy through frictional dissipation and negative vertical advection. The kinetic energy budget also shows that gravity waves have a strong influence on the other terms of the budget, i.e. horizontal advection and horizontal work of pressure forces, so evaluating the influence of gravity waves on the mean-flow with the vertical advection term alone is not sufficient, at least in this case. We finally obtain that gravity waves generated by the Vestfjella Mountains reaching lower stratospheric heights generally deplete (create kinetic energy in the lower troposphere (upper troposphere–lower stratosphere, in contradiction with the usual decelerating effect attributed to gravity waves on the zonal circulation in the upper troposphere–lower stratosphere.

  2. Inertia gravity waves in the upper troposphere during the MaCWAVE winter campaign – Part I: Observations with collocated radars

    Directory of Open Access Journals (Sweden)

    R. Goldberg

    2006-11-01

    Full Text Available During the {MaCWAVE} campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andøya Rocket Range (ARR near Andenes and the Swedish Rocket Range (ESRANGE near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHF radar in the upper troposphere/ lower stratosphere at Andenes (69.3° N, 16.0° E and the ESRAD VHF radar near Kiruna (67.9° N, 21.9° E. Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24–26 January 2003 with dominant vertical wavelengths of about 4–5 km as well as with dominant observed periods of about 13–14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of ~200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of ~5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains.

  3. Propagation of short-period gravity waves at high-latitudes during the MaCWAVE winter campaign

    Directory of Open Access Journals (Sweden)

    K. Nielsen

    2006-07-01

    Full Text Available As part of the MaCWAVE (Mountain and Convective Waves Ascending Vertically winter campaign an all-sky monochromatic CCD imager has been used to investigate the properties of short-period mesospheric gravity waves at high northern latitudes. Sequential measurements of several nightglow emissions were made from Esrange, Sweden, during a limited period from 27–31 January 2003. Coincident wind measurements over the altitude range (~80–100 km using two meteor radar systems located at Esrange and Andenes have been used to perform a novel investigation of the intrinsic properties of five distinct wave events observed during this period. Additional lidar and MSIS model temperature data have been used to investigate their nature (i.e. freely propagating or ducted. Four of these extensive wave events were found to be freely propagating with potential source regions to the north of Scandinavia. No evidence was found for strong orographic forcing by short-period waves in the airglow emission layers. The fifth event was most unusual exhibiting an extensive, but much smaller and variable wavelength pattern that appeared to be embedded in the background wind field. Coincident wind measurements indicated the presence of a strong shear suggesting this event was probably due to a large-scale Kelvin-Helmholtz instability.

  4. Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: stability, ringdown, and gravitational-wave emission

    CERN Document Server

    Blázquez-Salcedo, Jose Luis

    2016-01-01

    Gravitational waves emitted by distorted black holes---such as those arising from the coalescence of two neutron stars or black holes---carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory, and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations; (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that...

  5. Gravitational waves and red shifts - A space experiment for testing relativistic gravity using multiple time-correlated radio signals

    Science.gov (United States)

    Smarr, L. L.; Vessot, R. F. C.; Lundquist, C. A.; Decher, R.; Piran, T.

    1983-01-01

    A two-step satellite mission for improving the accuracy of gravitational wave detection and for observing actual gravity waveforms is proposed. The spacecraft would carry both a highly stable hydrogen maser, which would control a transmitter sending signals to earth, and a Doppler transponder operating in the two-way mode. The use of simultaneous one- and two-way Doppler transmissions offers four time records of frequency pulsations, which can reveal gravitational radiation at 1-10 MHz with an amplitude accuracy of a factor of six. The first mission phase would consist of a Shuttle launch into a highly eccentric orbit to obtain measurements of the gravitational redshift using gravitational potentials of different earth regions to establish that gravity is describable by a metric theory. Then, after a boost into a heliocentric orbit at 6 AU, the earth-satellite system could detect gravitational waves in the solar system, as well as bursts emitted by the collisions of supermassive black holes.

  6. Towards New Constraints in Extended Theories of Gravity: Cosmography and Gravitational-Wave Signals from Neutron Stars

    Directory of Open Access Journals (Sweden)

    Álvaro de la Cruz Dombriz

    2018-02-01

    Full Text Available Combined cosmological, astrophysical and numerical tests may shed some light on the viability of theories of gravity beyond Einsteinian relativity. In this letter, we present two different techniques providing complementary ways of testing new physics beyond the Λ CDM cosmological paradigm. First, we shall present some of the latest progress and shortcomings in the cosmographic model-independent approach for several modified gravity theories using supernovae catalogues, baryonic acoustic oscillation data and H ( z differential age compilations. Second, we shall show how once the Einsteinian paradigm is abandoned, the phenomenology of neutron stars changes dramatically since neutron-star masses can be much larger than their General Relativity counterparts. Consequently, the total energy available for radiating gravitational waves could be of the order of several solar masses, and thus a merger of these stars constitutes a privileged wave source. Unfortunately at the present time our persisting lack of understanding in the strong interaction sector does not allow to distinguish the alternative theories from the usual General Relativity predictions.

  7. Traveling Ionospheric Disturbances generated by upward propagating gravity waves simulated by a whole atmosphere-ionosphere coupled Model

    Science.gov (United States)

    Miyoshi, Y.; Jin, H.; Fujiwara, H.; Shinagawa, H.

    2017-12-01

    It has been recognized that gravity waves (GWs) play an important role on the momentum and energy budget in the thermosphere/ionosphere. In this study, using a whole atmosphere-ionosphere coupled model (GAIA), behaviors of Traveling Ionospheric Disturbances (TIDs) generated by upward propagating GWs in the thermosphere are investigated. The horizontal resolution of GAIA is 1 degree longitude by 1 degree latitude, which is adequate to simulate large-scale GWs. The GAIA contains the region from the ground surface to the upper thermosphere, so that we can simulate excitation of gravity waves in the lower atmosphere, their upward propagation to the mesosphere and thermosphere, and their impacts on the thermosphere/ionosphere system. The GAIA can simulate TIDs because interaction processes between the ionosphere and neutral atmosphere are included. We focus on seasonal and longitudinal variations of TIDs and their relation to GW activity in the thermosphere. Our results indicate that many TIDs are generated by upward propagating GWs in the thermosphere, and these TIDs propagate equatorward. TIDs are much stronger in winter than in summer. Moreover, day-to-day variability of GW activity in the stratosphere and mesosphere are examined, and their impacts on temporal variability of TIDs are discussed.

  8. Observations of Upward Propagating Gravity Waves in the Vertical Transport of Aerosols during Daytime Boundary Layer Evolution over Central Himalayan Region

    Science.gov (United States)

    Shukla, K. K.; Phani Kumar, D. V.; Kondapalli, N. K.; Kotamarthi, V. R.; Newsom, R. K.

    2014-12-01

    In this study, we present a case study on 16 October 2011 to show the first observational evidence of the influence of short period gravity waves in aerosol transport during daytime over the central Himalayan region. The Doppler lidar data has been utilized to address the daytime boundary layer evolution and related aerosol dynamics over the site. Mixing layer height is estimated by wavelet covariance transform method and found to be ~ 0.7 km, AGL. Aerosol optical depth observations during daytime revealed an asymmetry showing clear enhancement during afternoon hours as compared to forenoon. Interestingly, Fourier and wavelet analysis of vertical velocity and attenuated backscatter showed similar 50-90 min short period gravity wave signatures during afternoon hours. Moreover, our observations showed that gravity waves are dominant within the boundary layer implying that the daytime boundary layer dynamics is playing a vital role in transporting the aerosols from surface to the top of the boundary layer. Similar modulations are also evident in surface parameters like temperature, relative humidity and wind speed indicating these waves are associated with the dynamical aspects over Himalayan region. Finally, time evolution of range-height indicator snapshots during daytime showed strong upward velocities especially during afternoon hours implying that convective processes through short period gravity waves plays a significant role in transporting aerosols from the nearby valley region to boundary layer top over the site. These observations also establish the importance of wave induced daytime convective boundary layer dynamics in the lower Himalayan region.

  9. Contributions to a fifth-order model equation for steady capillary-gravity waves over a bump

    Science.gov (United States)

    Tsai, Chung-Hsien

    1999-12-01

    The objective of this dissertation is to study the solutions, h(x) , of a nonlinear model equation for steady capillary-gravity waves on an ideal fluid flow over a compact or non-compact bump with the Bond number, a nondimensional surface tension coefficient, close to its critical value 1/3 and the Froude number, a nondimensional wave speed, close to 1. There are nine cases to be discussed according to the eigenvalues of the linearized model equation. First, we study the stability of zero solution which will confirm that the solutions of the model equation will remain bounded when the waves pass the compact bump, [x1,x2] , if it is stable and dhn/dxn| x=x2,n=0,1,2,3 , are sufficiently close to zero solution. Next, we show that there exist periodic solutions, symmetric and unsymmetric solitary wave solutions, bounded solutions and asymptotic solutions in all nine cases with a compact bump. We also show there exist explicit exact solutions for all cases with a special non-compact bump. Finally we carry out numerical computations to verify the theoretical results discussed cussed above.

  10. High penetration wind generation impacts on spot prices in the Australian national electricity market

    International Nuclear Information System (INIS)

    Cutler, Nicholas J.; Boerema, Nicholas D.; MacGill, Iain F.; Outhred, Hugh R.

    2011-01-01

    This paper explores wind power integration issues for the South Australian (SA) region of the Australian National Electricity Market (NEM) by assessing the interaction of regional wind generation, electricity demand and spot prices over 2 recent years of market operation. SA's wind energy penetration has recently surpassed 20% and it has only a limited interconnection with other regions of the NEM. As such, it represents an interesting example of high wind penetration in a gross wholesale pool market electricity industry. Our findings suggest that while electricity demand continues to have the greatest influence on spot prices in SA, wind generation levels have become a significant secondary influence, and there is an inverse relationship between wind generation and price. No clear relationship between wind generation and demand has been identified although some periods of extremely high demand may coincide with lower wind generation. Periods of high wind output are associated with generally lower market prices, and also appear to contribute to extreme negative price events. The results highlight the importance of electricity market and renewable policy design in facilitating economically efficient high wind penetrations. - Highlights: → In South Australia (SA) wind generation is having an influence on market prices. → Little or no correlation is found between wind generation and demand. → Wind farms in SA are receiving a lower average price than in other States. → The results highlight the importance of appropriate electricity market design.

  11. Investigation of fog structure affected by gravity waves and turbulence in the mountainous region of Pyeongchang, Korea, the place for the 2018 Winter Olympics and Paralympics

    Science.gov (United States)

    La, I.; Yum, S. S.; Yeom, J. M.; Gultepe, I.

    2017-12-01

    Since microphysical and dynamical processes of fog are not well-known and have non-linear relationships among processes that are related to fog formation, improving the accuracy of the fog forecasting/nowcasting system is challenging. For these reasons, understanding the fog mechanism is needed to develop the fog forecasting system. So, we focus on understanding fog-turbulence interactions and fog-gravity wave interactions. Many studies noted that turbulence plays important roles in fog. However, a discrepancy between arguments for the effect of turbulent mixing on fog formation exists. Several studies suggested that turbulent mixing suppresses fog formation. Some other studies reported that turbulent mixing contributes to fog formation. On the other hand, several quasi-periodic oscillations of temperature, visibility, and vertical velocity, which have period of 10-20 minutes, were observed to be related to gravity waves in fog; because gravity waves play significant dynamic roles in the atmosphere. Furthermore, a numerical study suggested that gravity waves, simulated near the top of the fog layer, may affect fog microphysics. Thus, we investigate the effects of turbulent mixing on fog formation and the influences of gravity waves on fog microphysics to understand fog structure in Pyeongchang. In these studies, we analyze the data that are obtained from doppler lidar and 3.5 m meteorological observation tower including 3D-ultrasonic anemometer, IR sensor, and fog monitor during ICE-POP (International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games) campaign. In these instruments, doppler lidar is a good instrument to observe the gravity waves near the fog top, while in situ measurements have small spatial coverage. The instruments are installed at the mountainous terrain of Pyeongchang, Korea. More details will be presented at the conference.

  12. Low-Cost Superconducting Wire for Wind Generators: High Performance, Low Cost Superconducting Wires and Coils for High Power Wind Generators

    Energy Technology Data Exchange (ETDEWEB)

    None

    2012-01-01

    REACT Project: The University of Houston will develop a low-cost, high-current superconducting wire that could be used in high-power wind generators. Superconducting wire currently transports 600 times more electric current than a similarly sized copper wire, but is significantly more expensive. The University of Houston’s innovation is based on engineering nanoscale defects in the superconducting film. This could quadruple the current relative to today’s superconducting wires, supporting the same amount of current using 25% of the material. This would make wind generators lighter, more powerful and more efficient. The design could result in a several-fold reduction in wire costs and enable their commercial viability of high-power wind generators for use in offshore applications.

  13. Generalized plane waves in Poincaré gauge theory of gravity

    Science.gov (United States)

    Blagojević, Milutin; Cvetković, Branislav; Obukhov, Yuri N.

    2017-09-01

    A family of exact vacuum solutions, representing generalized plane waves propagating on the (anti-)de Sitter background, is constructed in the framework of Poincaré gauge theory. The wave dynamics is defined by the general Lagrangian that includes all parity even and parity odd invariants up to the second order in the gauge field strength. The structure of the solution shows that the wave metric significantly depends on the spacetime torsion.

  14. Convective gravity wave propagation and breaking in the stratosphere: comparison between WRF model simulations and lidar data

    Directory of Open Access Journals (Sweden)

    L. Costantino

    2015-09-01

    Full Text Available In this work we perform numerical simulations of convective gravity waves (GWs, using the WRF (Weather Research and Forecasting model. We first run an idealized, simplified and highly resolved simulation with model top at 80 km. Below 60 km of altitude, a vertical grid spacing smaller than 1 km is supposed to reliably resolve the effects of GW breaking. An eastward linear wind shear interacts with the GW field generated by a single convective thunderstorm. After 70 min of integration time, averaging within a radius of 300 km from the storm centre, results show that wave breaking in the upper stratosphere is largely dominated by saturation effects, driving an average drag force up to −41 m s−1 day−1. In the lower stratosphere, mean wave drag is positive and equal to 4.4 m s−1 day−1. In a second step, realistic WRF simulations are compared with lidar measurements from the NDACC network (Network for the Detection of Atmospheric Composition Changes of gravity wave potential energy (Ep over OHP (Haute-Provence Observatory, southern France. Using a vertical grid spacing smaller than 1 km below 50 km of altitude, WRF seems to reliably reproduce the effect of GW dynamics and capture qualitative aspects of wave momentum and energy propagation and transfer to background mean flow. Averaging within a radius of 120 km from the storm centre, the resulting drag force for the study case (2 h storm is negative in the higher (−1 m s−1 day−1 and positive in the lower stratosphere (0.23 m s−1 day−1. Vertical structures of simulated potential energy profiles are found to be in good agreement with those measured by lidar. Ep is mostly conserved with altitude in August while, in October, Ep decreases in the upper stratosphere to grow again in the lower mesosphere. On the other hand, the magnitude of simulated wave energy is clearly underestimated with respect to lidar data by about 3–4 times.

  15. Genesis of Twin Tropical Cyclones as Revealed by a Global Mesoscale Model: The Role of Mixed Rossby Gravity Waves

    Science.gov (United States)

    Shen, Bo-Wen; Tao, Wei-Kuo; Lin, Yuh-Lang; Laing, Arlene

    2012-01-01

    In this study, it is proposed that twin tropical cyclones (TCs), Kesiny and 01A, in May 2002 formed in association with the scale interactions of three gyres that appeared as a convectively coupled mixed Rossby gravity (ccMRG) wave during an active phase of the Madden-Julian Oscillation (MJO). This is shown by analyzing observational data, including NCEP reanalysis data and METEOSAT 7 IR satellite imagery, and performing numerical simulations using a global mesoscale model. A 10-day control run is initialized at 0000 UTC 1 May 2002 with grid-scale condensation but no sub-grid cumulus parameterizations. The ccMRG wave was identified as encompassing two developing and one non-developing gyres, the first two of which intensified and evolved into the twin TCs. The control run is able to reproduce the evolution of the ccMRG wave and thus the formation of the twin TCs about two and five days in advance as well as their subsequent intensity evolution and movement within an 8-10 day period. Five additional 10-day sensitivity experiments with different model configurations are conducted to help understand the interaction of the three gyres, leading to the formation of the TCs. These experiments suggest the improved lead time in the control run may be attributed to the realistic simulation of the ccMRG wave with the following processes: (1) wave deepening (intensification) associated with a reduction in wavelength and/or the intensification of individual gyres, (2) poleward movement of gyres that may be associated with boundary layer processes, (3) realistic simulation of moist processes at regional scales in association with each of the gyres, and (4) the vertical phasing of low- and mid-level cyclonic circulations associated with a specific gyre.

  16. Wind-generator influence to the power quality in the coupling point to the distribution network

    Directory of Open Access Journals (Sweden)

    Kostić Branka B.

    2011-01-01

    Full Text Available The paper presents the results of analysis of wind-generator and their influence to the power quality parameters in the coupling point to the distribution network. The specified results should be used as a starting point for distribution system operators (DSO for issuing permit for connecting renewable sources, mainly for wind-generators. As the case study, the results of measurements at the only one wind generator installed in Serbia, near town of Tutin, are used. The cases of wind-generator start and stop during low wind and consequently smaller value of the energy delivered to the network are particularly analyzed. Taking into consideration that law regulations in this field are not yet defined, EU standards and guidelines are used along with the newly adopted Technical recommendation No. 16 of Public Enterprise Electric Power Industry of Serbia.

  17. A topological study of gravity free-surface waves generated by bluff bodies using the method of steepest descents

    Science.gov (United States)

    Trinh, Philippe H.

    2016-07-01

    The standard analytical approach for studying steady gravity free-surface waves generated by a moving body often relies upon a linearization of the physical geometry, where the body is considered asymptotically small in one or several of its dimensions. In this paper, a methodology that avoids any such geometrical simplification is presented for the case of steady-state flows at low speeds. The approach is made possible through a reduction of the water-wave equations to a complex-valued integral equation that can be studied using the method of steepest descents. The main result is a theory that establishes a correspondence between different bluff-bodied free-surface flow configurations, with the topology of the Riemann surface formed by the steepest descent paths. Then, when a geometrical feature of the body is modified, a corresponding change to the Riemann surface is observed, and the resultant effects to the water waves can be derived. This visual procedure is demonstrated for the case of two-dimensional free-surface flow past a surface-piercing ship and over an angled step in a channel.

  18. Influence of the characteristic and installation site of wind generator on quantity of produced energy

    International Nuclear Information System (INIS)

    Palge, V.; Lepa, J.; Tamm, T.

    2002-01-01

    In Estonia, especially in inland the wind speed is rather low. According to the Master thesis of Tonis Tamm the opportunities of use of several types of wind generators are analysed. It is found out, that the wind generator, beginning to produce energy at wind speed 2 m/s can in such conditions produce about four times more electricity energy than such having 'cut-in' wind speed 4 m/s. (author)

  19. Remote Sensing of Gravity Wave Intensity and Temperature Signatures at Mesopause Heights Using the Nightglow Emissions

    National Research Council Canada - National Science Library

    Taylor, M. J; Pendleton, W. R., Jr; Seo, S. H; Picard, R. H

    2003-01-01

    ...) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art ground-based CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180...

  20. ARE660 Wind Generator: Low Wind Speed Technology for Small Turbine Development

    Energy Technology Data Exchange (ETDEWEB)

    Robert W. Preus; DOE Project Officer - Keith Bennett

    2008-04-23

    This project is for the design of a wind turbine that can generate most or all of the net energy required for homes and small businesses in moderately windy areas. The purpose is to expand the current market for residential wind generators by providing cost effective power in a lower wind regime than current technology has made available, as well as reduce noise and improve reliability and safety. Robert W. Preus’ experience designing and/or maintaining residential wind generators of many configurations helped identify the need for an improved experience of safety for the consumer. Current small wind products have unreliable or no method of stopping the wind generator in fault or high wind conditions. Consumers and their neighbors do not want to hear their wind generators. In addition, with current technology, only sites with unusually high wind speeds provide payback times that are acceptable for the on-grid user. Abundant Renewable Energy’s (ARE) basic original concept for the ARE660 was a combination of a stall controlled variable speed small wind generator and automatic fail safe furling for shutdown. The stall control for a small wind generator is not novel, but has not been developed for a variable speed application with a permanent magnet alternator (PMA). The fail safe furling approach for shutdown has not been used to our knowledge.

  1. Modeling ionospheric disturbance features in quasi-vertically incident ionograms using 3-D magnetoionic ray tracing and atmospheric gravity waves

    Science.gov (United States)

    Cervera, M. A.; Harris, T. J.

    2014-01-01

    The Defence Science and Technology Organisation (DSTO) has initiated an experimental program, Spatial Ionospheric Correlation Experiment, utilizing state-of-the-art DSTO-designed high frequency digital receivers. This program seeks to understand ionospheric disturbances at scales < 150 km and temporal resolutions under 1 min through the simultaneous observation and recording of multiple quasi-vertical ionograms (QVI) with closely spaced ionospheric control points. A detailed description of and results from the first campaign conducted in February 2008 were presented by Harris et al. (2012). In this paper we employ a 3-D magnetoionic Hamiltonian ray tracing engine, developed by DSTO, to (1) model the various disturbance features observed on both the O and X polarization modes in our QVI data and (2) understand how they are produced. The ionospheric disturbances which produce the observed features were modeled by perturbing the ionosphere with atmospheric gravity waves.

  2. Local vertical motions and kinetic temperature from AE-C as evidence for aurora-induced gravity waves

    Science.gov (United States)

    Spencer, N. W.; Theis, R. F.; Wharton, L. E.; Carignan, G. R.

    1976-01-01

    In situ measurements of local vertical neutral particle motions have been made using the Neutral Atmosphere Temperature Instrument (NATE) on Atmosphere Explorer-C from observations of the direction of flow of neutral particles into the antechamber of the sensor (mass spectrometer). Values ranging from a few to more than 80 meters per second have been observed. The data show vertical motions greater than a few meters per second to be present most of the time, the magnitude being a function of many factors including magnetic activity, location, and magnetic storm history. In a specific case, it is concluded that the observed vertical motions and kinetic temperature are evidence of a travelling disturbance originating as a gravity wave in the auroral zone.

  3. A climatology of gravity waves and other coherent disturbances at the Boulder Atmospheric Observatory during March-April 1984

    Science.gov (United States)

    Einaudi, F.; Bedard, A. J., Jr.; Finnigan, J. J.

    1989-01-01

    Gravity waves and other coherent disturbances observed at the Boulder Atmospheric Observatory (BAO) during the period between mid-March and mid-April 1984 were studied using data collected by an array of microbarographs located around the 300-m meteorological tower, together with data from the tower. Five passbands were considered in the period range 1-20 min; it was found that, for most of the time, the atmospheric state at these passbands displayed highly coherent structure. For disturbances of up to 5-min periods, a relationship was found between the turbulent kinetic energy measured on the tower and the amplitude of the rms pressure field at the ground, but, for longer periods, no such relationship was found.

  4. Modeling magnetic field and TEC signatures of large-amplitude acoustic and gravity waves generated by natural hazard events

    Science.gov (United States)

    Zettergren, M. D.; Snively, J. B.; Inchin, P.; Komjathy, A.; Verkhoglyadova, O. P.

    2017-12-01

    Ocean and solid earth responses during earthquakes are a significant source of large amplitude acoustic and gravity waves (AGWs) that perturb the overlying ionosphere-thermosphere (IT) system. IT disturbances are routinely detected following large earthquakes (M > 7.0) via GPS total electron content (TEC) observations, which often show acoustic wave ( 3-4 min periods) and gravity wave ( 10-15 min) signatures with amplitudes of 0.05-2 TECU. In cases of very large earthquakes (M > 8.0) the persisting acoustic waves are estimated to have 100-200 m/s compressional velocities in the conducting ionospheric E and F-regions and should generate significant dynamo currents and magnetic field signatures. Indeed, some recent reports (e.g. Hao et al, 2013, JGR, 118, 6) show evidence for magnetic fluctuations, which appear to be related to AGWs, following recent large earthquakes. However, very little quantitative information is available on: (1) the detailed spatial and temporal dependence of these magnetic fluctuations, which are usually observed at a small number of irregularly arranged stations, and (2) the relation of these signatures to TEC perturbations in terms of relative amplitudes, frequency, and timing for different events. This work investigates space- and time-dependent behavior of both TEC and magnetic fluctuations following recent large earthquakes, with the aim to improve physical understanding of these perturbations via detailed, high-resolution, two- and three-dimensional modeling case studies with a coupled neutral atmospheric and ionospheric model, MAGIC-GEMINI (Zettergren and Snively, 2015, JGR, 120, 9). We focus on cases inspired by the large Chilean earthquakes from the past decade (viz., the M > 8.0 earthquakes from 2010 and 2015) to constrain the sources for the model, i.e. size, frequency, amplitude, and timing, based on available information from ocean buoy and seismometer data. TEC data are used to validate source amplitudes and to constrain

  5. Effects of a strong magnetic field on internal gravity waves: trapping, phase mixing, reflection and dynamical chaos

    Science.gov (United States)

    Loi, Shyeh Tjing; Papaloizou, John C. B.

    2018-04-01

    The spectrum of oscillation modes of a star provides information not only about its material properties (e.g. mean density), but also its symmetries. Spherical symmetry can be broken by rotation and/or magnetic fields. It has been postulated that strong magnetic fields in the cores of some red giants are responsible for their anomalously weak dipole mode amplitudes (the "dipole dichotomy" problem), but a detailed understanding of how gravity waves interact with strong fields is thus far lacking. In this work, we attack the problem through a variety of analytical and numerical techniques, applied to a localised region centred on a null line of a confined axisymmetric magnetic field which is approximated as being cylindrically symmetric. We uncover a rich variety of phenomena that manifest when the field strength exceeds a critical value, beyond which the symmetry is drastically broken by the Lorentz force. When this threshold is reached, the spatial structure of the g-modes becomes heavily altered. The dynamics of wave packet propagation transitions from regular to chaotic, which is expected to fundamentally change the organisation of the mode spectrum. In addition, depending on their frequency and the orientation of field lines with respect to the stratification, waves impinging on different parts of the magnetised region are found to undergo either reflection or trapping. Trapping regions provide an avenue for energy loss through Alfvén wave phase mixing. Our results may find application in various astrophysical contexts, including the dipole dichotomy problem, the solar interior, and compact star oscillations.

  6. Near-surface current meter array measurements of internal gravity waves

    Energy Technology Data Exchange (ETDEWEB)

    Jones, H.B.E. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    We have developed various processing algorithms used to estimate the wave forms produced by hydrodynamic Internal Waves. Furthermore, the estimated Internal Waves are used to calculate the Modulation Transfer Function (MTF) which relates the current and strain rate subsurface fields to surface scattering phenomenon imaged by radar. Following a brief discussion of LLNL`s measurement platform (a 10 sensor current meter array) we described the generation of representative current and strain rate space-time images from measured or simulated data. Then, we present how our simulation capability highlighted limitations in estimating strain rate. These limitations spurred the application of beamforming techniques to enhance our estimates, albeit at the expense of collapsing our space-time images to 1-D estimates. Finally, we discuss progress with regard to processing the current meter array data captured during the recent Loch Linnhe field trials.

  7. Numerical modelling of the structure of electromagnetic disturbances generated by acoustic-gravity waves

    International Nuclear Information System (INIS)

    Pogorel'tsev, A.I.; Bidlingmajer, E.R.

    1992-01-01

    A numeric model of electromagnetic field disturbances generated under the interaction of acoustic-gravitational waves with ionospheric plasma is elaborated and vertical structure of the above disturbances is calculated. The estimates shown that electromagnetic disturbances can penetrate into neutral atmosphere and can be recorded through measurements of the variation of magnetic field and electron field vertical component near the earth is surface. A conclusion is made on a feasibility of monitoring of acoustic-gravitational wave activity in the lower thermosphere through land measurements of magnetic and electric field variations

  8. Field investigations on port non-tranquility caused by infra-gravity water waves

    OpenAIRE

    Najafi-Jilani, A.; Rahimi-Maleki, D.

    2010-01-01

    Field investigations have been carried out in two 60-day stages on the surf beat low frequency waves in Anzali port, one of the main commercial ports in Iran, located in southwest coast of the Caspian Sea. The characteristics of significant water waves were measured at three metering stations in the sea, one at the entrance of the port and three in the basin. The measured data were inspected to investigate the surf beat negative effects on the tranquility of the port. Using field measurements...

  9. Effects of eddy viscosity and thermal conduction and Coriolis force in the dynamics of gravity wave driven fluctuations in the OH nightglow

    International Nuclear Information System (INIS)

    Hickey, M.P.

    1988-01-01

    Recently, Walterscheid et al. (1987) have described a dynamical-chemical model of wave-driven fluctuations in the OH nightglow which incorporated a five-reaction photochemical scheme and the dynamics of linearized acoustic-gravity waves in an isothermal, motionless atmosphere. The intensity oscillation (δI) about the time-averaged intensity (I 0 ) and the temperature oscillation (δT) about the time-averaged temperature (T 0 ) were related by means of the complex ratio η triple-bond (δI/I 0 )/(δT/T 0 ). One of the main conclusions of their work was that the inclusion of dynamical effects is absolutely essential for a valid assessment of η at any wave period. In this paper the model of Walterscheid et al. (1987) is modified to include in the gravity wave dynamics the effects of eddy viscosity, eddy thermal conduction, and Coriolis force (with the shallow atmosphere approximation), and calculations are performed for the same nominal case as used by these previous authors (i.e., λ x = 100 km and atmospheric conditions pertinent to 83 km altitude), but only gravity wave periods are considered. It is found that for wave periods greater than some 2 or 3 hours the value of η is greatly modified by the inclusion of eddy thermal conduction. Although when acting alone the eddy viscosity is relatively unimportant, it significantly modifies the results when acting in conjunction with the eddy thermal conduction. The inclusion of the Coriolis force is found to be insignificant at any wave period. Although it is for the longest-period waves that the values of η are most modified by the inclusion of dissipation, this dissipation may be severe enough to place an observational constraint on such waves

  10. Characteristics of gravity waves generated in a convective and a non-convective environment revealed from hourly radiosonde observation under CPEA-II campaign

    Directory of Open Access Journals (Sweden)

    S. K. Dhaka

    2011-12-01

    Full Text Available Analyses of hourly radiosonde data of temperature, wind, and relative humidity during four days (two with convection and two with no convection as a part of an intensive observation period in CPEA-2 campaign over Koto Tabang (100.32° E, 0.20° S, Indonesia, are presented. Characteristics of gravity waves in terms of dominant wave frequencies at different heights and their vertical wavelengths are shown in the lower stratosphere during a convective and non-convective period. Gravity waves with periods ~10 h and ~4–5 h were found dominant near tropopause (a region of high stability on all days of observation. Vertical propagation of gravity waves were seen modified near heights of the three identified strong wind shears (at ~16, 20, and 25 km heights due to wave-mean flow interaction. Between 17 and 21 km heights, meridional wind fluctuations dominated over zonal wind, whereas from 22 to 30 km heights, wave fluctuations with periods ~3–5 h and ~8–10 h in zonal wind and temperature were highly associated, suggesting zonal orientation of wave propagation. Gravity waves from tropopause region to 30 km heights were analyzed. In general, vertical wavelength of 2–5 km dominated in all the mean-removed (~ weekly mean wind and temperature hourly profiles. Computed vertical wavelength spectra are similar, in most of the cases, to the source spectra (1–16 km height except that of zonal wind spectra, which is broad during active convection. Interestingly, during and after convection, gravity waves with short vertical wavelength (~2 km and short period (~2–3 h emerged, which were confined in the close vicinity of tropopause, and were not identified on non-convective days, suggesting convection to be the source for them. Some wave features near strong wind shear (at 25 km height were also observed with short vertical wavelengths in both convective and non-convective days, suggesting wind shear to be the sole cause of generation and seemingly not

  11. Statistical characteristics of gravity wave activities observed by an OH airglow imager at Xinglong, in northern China

    Directory of Open Access Journals (Sweden)

    Q. Li

    2011-08-01

    Full Text Available An all-sky airglow imager (ASAI was installed at Xinglong, in northern China (40.2° N, 117.4° E in November 2009 to study the morphology of atmospheric gravity waves (AGWs in the mesosphere and lower thermosphere (MLT region. Using one year of OH airglow imager data from December 2009 to November 2010, the characteristics of short-period AGWs are investigated and a yearlong AGW climatology in northern China is first ever reported. AGW occurrence frequency in summer and winter is higher than that in equinoctial months. Observed bands mainly have horizontal wavelengths from 10 to 35 km, observed periods from 4 to 14 min and observed horizontal phase speeds in the range of 30 to 60 m s−1. Most of the bands propagate in the meridional direction. The propagation directions of the bands show a strong southwestward preference in winter, while almost all bands propagate northeastward in summer. Although the wind filtering in the middle atmosphere may control AGW propagations in the zonal direction, the non-uniform distribution of wave sources in the lower atmosphere may contribute to the anisotropy in the meridional direction in different seasons. Additionally, as an indication of local instability, the characteristics of ripples are also analyzed. It also shows seasonal variations, occurring more often in summer and winter and mainly moving westward in summer and eastward in winter.

  12. Climatological monthly characteristics of middle atmosphere gravity waves (10 min-10 h during 1979-1993 at Saskatoon

    Directory of Open Access Journals (Sweden)

    N. M. Gavrilov

    Full Text Available Saskatoon (52° N, 107°W medium frequency (MF radar data from 1979 to 1993 have been analyzed to investigate the climatology of irregular wind components in the height region 60-100 km. This component is usually treated in terms of internal gravity waves (IGW. Three different band-pass filters have been used to separate the intensities of IGWs having periods 0.2-2.5; 1.5-6 and 2-10 h, respectively. Height, seasonal and inter-annual variations of IGW intensities, anisotropy and predominant directions of propagation are investigated. Mean over 14 years' seasonal variation of the intensity of long-period IGWs shows a dominant annual component with winter maximum and summer minimum. Seasonal variations of the intensity of short-period waves have a strong semi-annual component as well, which forms a secondary maximum in summer. Predominant azimuths of long-period IGWs are generally zonal, though they vary with season. For short-period IGWs, the predominant azimuth is closer to the meridional direction. Anisotropy of IGW intensity is larger in summer, winter and at lower altitudes. The IGW intensity shows apparent correlation with both solar and geomagnetic activity. In most cases, this correlation appears to be negative. The variations versus solar activity is larger for longer-period IGW. Possible reasons and consequences of the observed climatological variations of IGW intensity are discussed.

  13. Retrieving mesospheric winds and gravity waves using high resolution radar measurements of polar mesospheric summer echoes with MAARSY

    Science.gov (United States)

    Stober, G.; Sommer, S.; Schult, C.; Chau, J. L.; Latteck, R.

    2013-12-01

    The Middle Atmosphere Alomar Radar System (MAARSY) located at the northern Norwegian island of Andøya (69.3 ° N, 16° E) observes polar mesosphere summer echoes (PMSE) on a regular basis. This backscatter turned out to be an ideal tracer of atmospheric dynamics and to investigate the wind field at the mesosphere/lower thermosphere (MLT) at high spatial and temporal scales. MAARSY is dedicated to explore the polar mesosphere at such high resolution and employs an active phased array antenna with the capability to steer the beam on a pulse-to-pulse basis, which permits to perform systematic scanning of PMSE and to investigate the horizontal structure of the backscatter. The radar also uses a 16 channel receiver system for interferometric applications e.g. mean angle of arrival analysis or coherent radar imaging. Here we present measurements using these features of MAARSY to study the wind field at the MLT applying sophisticated wind analysis algorithms such as velocity azimuth display or volume velocity processing to derive gravity wave parameters such as horizontal wave length, phase speed and propagation direction. Further, we compare the interferometrically corrected and uncorrected wind measurements to emphasize the importance to account for likely edge effects using PMSE as tracer of the dynamics. The observations indicate huge deviations from the nominal beam pointing direction at the upper and lower edges of the PMSE altering the wind analysis.

  14. Ion Friction and Quantification of the Geomagnetic Influence on Gravity Wave Propagation and Dissipation in the Thermosphere-Ionosphere

    Science.gov (United States)

    Medvedev, Alexander S.; Yiǧit, Erdal; Hartogh, Paul

    2017-12-01

    Motions of neutrals and ions in the thermosphere-ionosphere (TI) do not, generally, coincide due to the presence of the geomagnetic field and associated electromagnetic forces affecting plasma. Collisions of ions with gravity wave (GW)-induced motions of neutrals impose damping on the latter. We derive a practical formula for the vertical damping rate of GW harmonics that accounts for the geometry of the geomagnetic field and the direction of GW propagation. The formula can be used in parameterizations of GW effects developed for general circulation models extending from the lower atmosphere into the mesosphere and thermosphere. Vertical damping of GW harmonics by ion-neutral interactions in the TI depends on the geometry of the geomagnetic field but not the strength of the latter. The ion damping of harmonics propagating in the meridional direction (in the geomagnetic coordinates) maximizes over the poles and reduces to zero over the equator. Waves propagating in the zonal direction are uniformly affected by ions at all latitudes. Accounting for the anisotropy produces changes in the GW drag in the F region of more than 100 m s-1 d-1, cooling/heating rates of more than 15 K d-1, and in GW temperature variance of disturbances by more than 5 K.

  15. S-wave propagating in an anisotropic inhomogeneous elastic medium under the influence of gravity, initial stress, electric and magnetic field

    Directory of Open Access Journals (Sweden)

    Kakar Rajneesh

    2014-01-01

    Full Text Available The purpose of this paper is to study the effect of gravity, initial stress, non-homogeneity, electric and magnetic field on the propagation of shear waves in an anisotropic incompressible medium. Various graphs are plotted to show the effect of direction of propagation, the anisotropy, magnetic field, electric field, non-homogeneity of the medium and the initial stress on shear waves. The dispersion equations for shear waves are obtained and discussed for different cases. In fact, in the absence of various material parameters, these equations are in agreement with the classical results for isotropic medium.

  16. Seasonal Variations of Mesospheric Gravity Waves Observed with an Airglow All-sky Camera at Mt. Bohyun, Korea (36° N

    Directory of Open Access Journals (Sweden)

    Yong Ha Kim

    2010-09-01

    Full Text Available We have carried out all-sky imaging of OH Meinel, O2 atmospheric and OI 557.7 nm airglow layers in the period from July of 2001 through September of 2005 at Mt. Bohyun, Korea (36.2° N, 128.9° E, Alt = 1,124 m. We analyzed the images observed during a total of 153 clear moonless nights and found 97 events of band-type waves. The characteristics of the observed waves (wavelengths, periods, and phase speeds are consistent with internal gravity waves. The wave occurrence shows an approximately semi-annual variation, with maxima near solstices and minima near equinoxes, which is consistent with other studies of airglow wave observations, but not with those of mesospheric radar/lidar observations. The observed waves tended to propagate westward during fall and winter, and eastward during spring and summer. Our ray tracing study of the observed waves shows that majority of the observed waves seemed to originate from mesospheric altitudes. The preferential directions and the apparent source altitudes can be explained if the observed waves are secondary waves generated from primary waves that have been selected by the filtering process and break up at the mesospheric altitudes.

  17. Drake Antarctic Agile Meteor Radar (DrAAMER) First Results: Configuration and Comparison of Mean and Tidal Wind and Gravity Wave Momentum Flux Measurements with SAAMER

    Science.gov (United States)

    Fritts, D. C.; Janches, D.; Iimura, H.; Hocking, W. K.; Bageston, J. V.; Pene, N. M.

    2011-01-01

    A new-generation meteor radar was installed at the Brazilian Antarctic Comandante Ferraz Base (62.1degS) in March 2010. This paper describes the motivations for the radar location, its measurement capabilities, and comparisons of measured mean winds, tides, and gravity wave momentum fluxes from April to June of 2010 and 2011 with those by a similar radar on Tierra del Fuego (53.8degS). Motivations for the radars include the "hotspot" of small-scale gravity wave activity extending from the troposphere into the mesosphere and lower thermosphere (MLT) centered over the Drake Passage, the maximum of the semidiurnal tide at these latitudes, and the lack of other MLT wind measurements in this latitude band. Mean winds are seen to be strongly modulated at planetary wave and longer periods and to exhibit strong coherence over the two radars at shorter time scales as well as systematic seasonal variations. The semidiurnal tide contribute most to the large-scale winds over both radars, with maximum tidal amplitudes during May and maxima at the highest altitudes varying from approx.20 to >70 m/s. In contrast, the diurnal tide and various planetary waves achieve maximum winds of approx.10 to 20 m/s. Monthly-mean gravity wave momentum fluxes appear to reflect the occurrence of significant sources at lower altitudes, with relatively small zonal fluxes over both radars, but with significant, and opposite, meridional momentum fluxes below approx.85 km. These suggest gravity waves propagating away from the Drake Passage at both sites, and may indicate an important source region accounting in part for this "hotspot".

  18. Evidence at Mesospheric Altitude of Deeply Propagating Atmospheric Gravity Waves Created by Orographic Forcing over the Auckland Islands (50.5ºS) During the Deepwave Project

    Science.gov (United States)

    Pautet, P. D.; Ma, J.; Taylor, M. J.; Bossert, K.; Doyle, J. D.; Eckermann, S. D.; Williams, B. P.; Fritts, D. C.

    2014-12-01

    The DEEPWAVE project recently took place in New Zealand during the months of June and July 2014. This international program focused on investigating the generation and deep propagation of atmospheric gravity waves. A series of instruments was operated at several ground-based locations and on-board the NSF Gulfstream V aircraft. 26 research flights were performed to explore possible wave sources and their effects on the middle and upper atmosphere. On July 14th, a research flight was conducted over the Auckland Islands, a small sub Antarctic archipelago located ~450km south of New Zealand. Moderate southwesterly tropospheric wind (~25m/s) was blowing over the rugged topography of the islands, generating mountain wave signature at the flight altitude. Spectacular small-scale gravity waves were simultaneously observed at the mesopause level using the USU Advanced Mesospheric Temperature Mapper (AMTM). Their similarity with the model-predicted waves was striking. This presentation will describe this remarkable case of deep wave propagation and compare the measurements obtained with the instruments on-board the aircraft with forecasting and wave propagation models.

  19. Theoretical Investigation of the Effects of Atmospheric Gravity Waves on the Hydroxyl Emissions of the Atmosphere.

    Science.gov (United States)

    1979-12-31

    Later, these effects have been observed and analyzed by a number of in- vestigators [e.g. Okuda (1962), Silverman (1962), Barbier (19,: 1965), Weill and...waves on the in- dividual atmospheric constituents which produce the airglow through chemical reactions . There are two cases to be considered. The...Theoretical Formulation We shall assume that the primary mechanism for the pro- duction of OH emissions is given by the reaction H

  20. Impact of wind generation on the operation and development of the UK electricity systems

    International Nuclear Information System (INIS)

    Strbac, Goran; Shakoor, Anser; Pudjianto, Danny; Black, Mary; Bopp, Thomas

    2007-01-01

    Although penetration of wind generation may displace a significant amount of energy produced by large conventional plant, there are issues associated with the extent to which wind generation will be able to replace the capacity and flexibility of conventional generating plant. This is important since wind power is variable, so it will be necessary to retain a significant proportion of conventional plant to ensure security of supply especially under conditions of high demand and low wind. Hence, the capacity value of wind generation will be limited as it will not be possible to displace conventional generation capacity on a ''megawatt for megawatt'' basis. Wind power is variable and not easy to predict, hence various forms of additional reserves will be needed to maintain the balance between supply and demand at all times. Additionally, if the majority of wind generation plant is located in Scotland and the North of England, reinforcement of the transmission network will be needed to accommodate the increases in the north-south flow of electricity. In this paper an assessment of the costs and benefits of wind generation on the UK electricity system is carried out, assuming different levels of wind power capacity. Overall, it is concluded that the system will be able to accommodate significant increases in wind power generation with relatively small increases in overall costs of supply, about 5% of the current domestic electricity price in case of 20% energy produced by wind power. (author)

  1. Gauge gravity duality for d-wave superconductors: prospects and challenges

    CERN Document Server

    Benini, Francesco; Rahman, Rakibur; Yarom, Amos

    2010-01-01

    We write down an action for a charged, massive spin two field in a fixed Einstein background. Despite some technical problems, we argue that in an effective field theory framework and in the context of the AdS/CFT correspondence, this action can be used to study the properties of a superfluid phase transition with a d-wave order parameter in a dual strongly interacting field theory. We investigate the phase diagram and the charge conductivity of the superfluid phase. We also explain how possible couplings between the spin two field and bulk fermions affect the fermion spectral function.

  2. The propagation of orographic gravity waves into the stratosphere. Linear theory, idealized and realistic numerical simulation; Die Ausbreitung orographisch angeregter Schwerewellen in die Stratosphaere. Lineare Theorie, idealisierte und realitaetsnahe numerische Simulation

    Energy Technology Data Exchange (ETDEWEB)

    Leutbecher, M. [DLR Deutsches Zentrum fuer Luft- und Raumfahrt e.V., Wessling (Germany). Inst. fuer Physik der Atmosphaere

    1998-07-01

    Flow over mountains in the stably stratified atmosphere excites gravity waves. The three-dimensional propagation of these waves into the stratosphere is studied using linear theority as well as idealized and realistic numerical simulations. Stagnation, momentum fluxes and temperature anomalies are analyzed for idealized types of flow. Isolated mountains with elliptical contours are considered. The unperturbed atmosphere has constant wind speed and constant static stability or two layers (troposphere/stratosphere) of constant stability each. Real flow over orography is investigated where gravity waves in the stratosphere have been observed. Characteristics of the gravity wave event over the southern tip of Greenland on 6 January 1992 were recorded on a flight of the ER-2 at an altitude of 20 km. In the second case polar stratospheric clouds (PSC) were observed by an airborne Lidar over Northern Scandinavia on 9 January 1997. The PSC were induced by temperature anomalies in orographic gravity waves. (orig.)

  3. Trading wind generation from short-term probabilistic forecasts of wind power

    DEFF Research Database (Denmark)

    Pinson, Pierre; Chevallier, Christophe; Kariniotakis, Georges

    2007-01-01

    Due to the fluctuating nature of the wind resource, a wind power producer participating in a liberalized electricity market is subject to penalties related to regulation costs. Accurate forecasts of wind generation are therefore paramount for reducing such penalties and thus maximizing revenue...... participation. Such strategies permit to further increase revenues and thus enhance competitiveness of wind generation compared to other forms of dispatchable generation. This paper formulates a general methodology for deriving optimal bidding strategies based on probabilistic forecasts of wind generation....... Despite the fact that increasing accuracy in spot forecasts may reduce penalties, this paper shows that, if such forecasts are accompanied with information on their uncertainty, i.e., in the form of predictive distributions, then this can be the basis for defining advanced strategies for market...

  4. Combined hydro-wind generation bids in a pool-based electricity market

    International Nuclear Information System (INIS)

    Angarita, Jorge L.; Usaola, Julio; Martinez-Crespo, Jorge

    2009-01-01

    Present regulatory trends are promoting the direct participation of wind energy in electricity markets. The final result of these markets sets the production scheduling for the operation time, including a power commitment from the wind generators. However, wind resources are uncertain, and the final power delivered usually differs from the initial power committed. This imbalance produces an overcost in the system, which must be paid by those who produce it, e.g., wind generators among others. As a result, wind farm revenue decreases, but it could increase by allowing wind farms to submit their bids to the markets together with a hydro generating unit, which may easily modify its production according to the expected imbalance. This paper presents a stochastic optimization technique that maximizes the joint profit of hydro and wind generators in a pool-based electricity market, taking into account the uncertainty of wind power prediction. (author)

  5. Lidar observations of middle atmospheric gravity wave activity over a low-latitude site (Gadanki, 13.5° N, 79.2° E

    Directory of Open Access Journals (Sweden)

    V. Sivakumar

    2006-05-01

    Full Text Available The low-latitude middle atmospheric gravity wave characteristics are presented using 310 nights of Rayleigh lidar observations made at Gadanki (13.5° N, 79.2° E over the period from March 1998 to December 2002. The gravity wave characteristics are presented in terms of vertical wave number and frequency spectra, along with the estimated potential energy for the four seasons, namely, spring, summer, autumn and winter. The computed wave number spectra for both the stratosphere and the mesosphere are found to differ significantly from a saturated model predicted spectrum. The spectra were found to be shallower at lower wave numbers and steeper at higher wave numbers with transition at ~8.85×10-4 cy/m. The computed frequency spectra seem to follow the model plot with a power law index of -5/3 above a frequency of ~2×10-4 Hz. The estimated potential energy per unit mass increases gradually up to ~60 km and then rather rapidly above this height to reach values of the order of 200J/kg at ~70 km.

  6. Results of Experimental and Theoretical Studies of the Atmospheric Turbulence, Internal Gravity Waves and Sporadic-E Layers by Resonant Scattering of Radio Waves on Artificial Periodic Irregularities

    Science.gov (United States)

    Bakhmetieva, Nataliya V.; Grigoriev; Tolmacheva, Ariadna V.

    Artificial periodic irregularities (API) formed by the powerful standing radio waves in the ionospheric plasma give the good chance for the lower ionosphere comprehensive studies. In this paper we present some applications of the API technique for experimental studies of sporadic E-layers (E _{s}), internal gravity waves and turbulent events in the lower ionosphere. API are formed in the field of the standing radio wave produced by interference of the incident wave and reflected one from the ionosphere (in more details about the API technique one can see in the book Belikovich et al., Ionospheric Research by Means of Artificial Periodic Irregularities - Katlenburg-Lindau, Germany. 2002. Copernicus GmbH. ISBN 3-936586-03-9). The spatial period of the irregular structure is equal to the standing wavelength Lambda or one-half the powerful wavelength lambda/2. API diagnostics are carried out at the API relaxation or decay stage by their sounding of probing radio pulses. Based on the measurement of an amplitude and a phase of the API scattered signal their relaxation time and regular vertical plasma velocity are measured. In the E-region of the ionosphere API are formed as a result of the diffusion redistribution of the non-uniformly heated plasma. The relaxation of the periodic structure is specified by the ambipolar diffusion process. The diffusion time is tau=(K (2) D _{a}) (-1) where K=2pi/Lambda and D _{a} is the ambipolar diffusion rate. The atmospheric turbulence causes reduction of the API relaxation time in comparison the diffusion time. Determination of the turbulent velocity is based on this fact. The vertical plasma velocity is determined by measuring the phase of the scattered signal. Atmospheric waves having the periods from 5-10 minutes to 5-6 hours give the contribution to temporal variations of the velocity. Parameters and effects of atmospheric waves and the turbulence on the API relaxation process are presented. Determination of the masses of the

  7. Revisiting internal gravity waves analysis using GPS RO density profiles: comparison with temperature profiles and application for wave field stability study

    Science.gov (United States)

    Pisoft, Petr; Sacha, Petr; Miksovsky, Jiri; Huszar, Peter; Scherllin-Pirscher, Barbara; Foelsche, Ulrich

    2018-01-01

    We revise selected findings regarding the utilization of Global Positioning System radio occultation (GPS RO) density profiles for the analysis of internal gravity waves (IGW), introduced by Sacha et al. (2014). Using various GPS RO datasets, we show that the differences in the IGW spectra between the dry-temperature and dry-density profiles that were described in the previous study as a general issue are in fact present in one specific data version only. The differences between perturbations in the temperature and density GPS RO profiles do not have any physical origin, and there is not the information loss of IGW activity that was suggested in Sacha et al. (2014). We investigate the previously discussed question of the temperature perturbations character when utilizing GPS RO dry-temperature profiles, derived by integration of the hydrostatic balance. Using radiosonde profiles as a proxy for GPS RO, we provide strong evidence that the differences in IGW perturbations between the real and retrieved temperature profiles (which are based on the assumption of hydrostatic balance) include a significant nonhydrostatic component that is present sporadically and might be either positive or negative. The detected differences in related spectra of IGW temperature perturbations are found to be mostly about ±10 %. The paper also presents a detailed study on the utilization of GPS RO density profiles for the characterization of the wave field stability. We have analyzed selected stability parameters derived from the density profiles together with a study of the vertical rotation of the wind direction. Regarding the Northern Hemisphere the results point to the western border of the Aleutian high, where potential IGW breaking is detected. These findings are also supported by an analysis of temperature and wind velocity profiles. Our results confirm advantages of the utilization of the density profiles for IGW analysis.

  8. Revisiting internal gravity waves analysis using GPS RO density profiles: comparison with temperature profiles and application for wave field stability study

    Directory of Open Access Journals (Sweden)

    P. Pisoft

    2018-01-01

    Full Text Available We revise selected findings regarding the utilization of Global Positioning System radio occultation (GPS RO density profiles for the analysis of internal gravity waves (IGW, introduced by Sacha et al. (2014. Using various GPS RO datasets, we show that the differences in the IGW spectra between the dry-temperature and dry-density profiles that were described in the previous study as a general issue are in fact present in one specific data version only. The differences between perturbations in the temperature and density GPS RO profiles do not have any physical origin, and there is not the information loss of IGW activity that was suggested in Sacha et al. (2014. We investigate the previously discussed question of the temperature perturbations character when utilizing GPS RO dry-temperature profiles, derived by integration of the hydrostatic balance. Using radiosonde profiles as a proxy for GPS RO, we provide strong evidence that the differences in IGW perturbations between the real and retrieved temperature profiles (which are based on the assumption of hydrostatic balance include a significant nonhydrostatic component that is present sporadically and might be either positive or negative. The detected differences in related spectra of IGW temperature perturbations are found to be mostly about ±10 %. The paper also presents a detailed study on the utilization of GPS RO density profiles for the characterization of the wave field stability. We have analyzed selected stability parameters derived from the density profiles together with a study of the vertical rotation of the wind direction. Regarding the Northern Hemisphere the results point to the western border of the Aleutian high, where potential IGW breaking is detected. These findings are also supported by an analysis of temperature and wind velocity profiles. Our results confirm advantages of the utilization of the density profiles for IGW analysis.

  9. Simulation of Gravity Wave Propagation in Free Surface Flows by an Incompressible SPH Algorithm

    International Nuclear Information System (INIS)

    Amanifard, N.; Mahnama, S. M.; Neshaei, S. A. L.; Mehrdad, M. A.; Farahani, M. H.

    2012-01-01

    This paper presents an incompressible smoothed particle hydrodynamics model to simulate wave propagation in a free surface flow. The Navier-Stokes equations are solved in a Lagrangian framework using a three-step fractional method. In the first step, a temporary velocity field is provided according to the relevant body forces. This velocity field is renewed in the second step to include the viscosity effects. A Poisson equation is employed in the third step as an alternative for the equation of state in order to evaluate pressure. This Poisson equation considers a trade-off between density and pressure which is utilized in the third step to impose the incompressibility effect. The computations are compared with the experimental as well as numerical data and a good agreement is observed. In order to validate proposed algorithm, a dam-break problem is solved as a benchmark solution and the computational results are compared with the previous numerical ones.

  10. A case study of gravity wave dissipation in the polar MLT region using sodium LIDAR and radar data

    Directory of Open Access Journals (Sweden)

    T. Takahashi

    2014-10-01

    Full Text Available This paper is primarily concerned with an event observed from 16:30 to 24:30 UT on 29 October 2010 during a very geomagnetically quiet interval (Kp ≤ 1. The sodium LIDAR observations conducted at Tromsø, Norway (69.6° N, 19.2° E captured a clearly discernible gravity wave (GW signature. Derived vertical and horizontal wavelengths, maximum amplitude, apparent and intrinsic period, and horizontal phase velocity were about ~ 11.9 km, ~ 1.38 × 103 km, ~ 15 K, 4 h, ~ 7.7 h, and ~ 96 m s−1, respectively, between a height of 80 and 95 km. Of particular interest is a temporal development of the uppermost altitude that the GW reached. The GW disappeared around 95 km height between 16:30 and 21:00 UT, while after 21:00 UT the GW appeared to propagate to higher altitudes (above 100 km. We have evaluated three mechanisms (critical-level filtering, convective and dynamic instabilities for dissipations using data obtained by the sodium LIDAR and a meteor radar. It is found that critical-level filtering did not occur, and the convective and dynamic instabilities occurred on some occasions. MF radar echo power showed significant enhancements between 18:30 and 21:00 UT, and an overturning feature of the sodium mixing ratio was observed between 18:30 and 21:20 UT above about 95 km. From these results, we have concluded that the GW was dissipated by wave breaking and instabilities before 21:00 UT. We have also investigated the difference of the background atmosphere for the two intervals and would suggest that a probable cause of the change in the GW propagation was due to the difference in the temperature gradient of the background atmosphere above 94 km.

  11. Historical detection of atmospheric impacts by large bolides using acoustic-gravity waves

    Energy Technology Data Exchange (ETDEWEB)

    ReVelle, D.O.

    1995-05-01

    During the period from about 1960 to the early 1980`s a number of large bolides (meteor-fireballs) entered the atmosphere which were sufficiently large to generate blast waves during their drag interaction with the air. For example, the remnant of the blast wave from a single kiloton class event was subsequently detected by up to six ground arrays of microbarographs which were operated by the U.S. Air Force during this pre-satellite period. Data have also been obtained from other sources during this period as well and are also discussed in this summary of the historical data. The Air Force data have been analyzed in terms of their observable properties in order to infer the influx rate of NEO`s (near-Earth objects) in the energy range from 0.2 to 1100 kt. The determined influx is in reasonable agreement with that determined by other methods currently available such as Rabinowitz (1992), Ceplecha, (1992; 1994b) and by Chapman and Morrison (1994) despite the fact that due to sampling deficiencies only a portion of the {open_quotes}true{close_quotes} flux of large bodies has been obtained by this method, i.e., only sources at relatively low elevations have been detected. Thus the weak, fragile cometary bodies which do not penetrate the atmosphere as deeply are less likely to have been sampled by this type of detection system. Future work using the proposed C.T.B.T. (Comprehensive Test Ban Treaty) global scale infrasonic network will be likely to improve upon this early estimate of the global influx of NEO`s considerably.

  12. Estimating the impact of wind generation and wind forecast errors on energy prices and costs in Ireland

    OpenAIRE

    Swinand, Gregory P; O'Mahoney, Amy

    2014-01-01

    This paper studies the impact of wind generation on system costs and prices in Ireland. The need to mitigate climate change, achieve renewables energy targets, and use renewable sources of energy means that many countries are considering greater levels of wind generation in their power generation mix. The overall impact of wind generation on system costs and performance has only been studied recently, and often with limited actual data from power systems with increased wind penetration. The p...

  13. Simulations of large winds and wind shears induced by gravity wave breaking in the mesosphere and lower thermosphere (MLT region

    Directory of Open Access Journals (Sweden)

    X. Liu

    2014-05-01

    Full Text Available Using a fully nonlinear two-dimensional (2-D numerical model, we simulated gravity waves (GWs breaking and their contributions to the formation of large winds and wind shears in the mesosphere and lower thermosphere (MLT. An eddy diffusion coefficient is used in the 2-D numerical model to parameterize realistic turbulent mixing. Our study shows that the momentum deposited by breaking GWs accelerates the mean wind. The resultant large background wind increases the GW's apparent horizontal phase velocity and decreases the GW's intrinsic frequency and vertical wavelength. Both the accelerated mean wind and the decreased GW vertical wavelength contribute to the enhancement of wind shears. This, in turn, creates a background condition that favors the occurrence of GW instability, breaking, and momentum deposition, as well as mean wind acceleration, which further enhances the wind shears. We find that GWs with longer vertical wavelengths and faster horizontal phase velocity can induce larger winds, but they may not necessarily induce larger wind shears. In addition, the background temperature can affect the time and height of GW breaking, thus causing accelerated mean winds and wind shears.

  14. The rate of neutron star binary mergers in the universe - Minimal predictions for gravity wave detectors

    Science.gov (United States)

    Phinney, E. S.

    1991-01-01

    Of the many sources which gravitational wave observatories might see, merging neutron star binaries are the most predictable. Their waveforms at the observable frequencies are easy to calculate. And three systems which will merge in less than a Hubble time have already been observed as binary pulsars: two in the disk of the Galaxy, and one in a globular cluster. From the lifetimes and positions of these, a lower limit to the merger rate in the Galaxy and globular cluster system are inferred with confidence. Taking the merger rate in other galaxies to scale with the star formation rate, the merger rate expected in the local universe is computed. An ultraconservative lower limit to the rate gives three per year within 1 Gpc. The best estimate, still conservative in that it considers only systems like those already observed, gives three per year within 200 Mpc. An upper limit of three mergers per year within 23/h Mpc is set by the rate of Type Ib supernovae. The rates of black hole binary mergers and black hole-neutron star binary mergers are model-dependent, but could be comparable to the given rate of neutron-star binary mergers.

  15. First test of high frequency Gravity Waves from inflation using Advanced LIGO

    International Nuclear Information System (INIS)

    Lopez, Alejandro; Freese, Katherine

    2015-01-01

    Inflation models ending in a first order phase transition produce gravitational waves (GW) via bubble collisions of the true vacuum phase. We demonstrate that these bubble collisions can leave an observable signature in Advanced LIGO, an upcoming ground-based GW experiment. These GW are dependent on two parameters of the inflationary model: ε represents the energy difference between the false vacuum and the true vacuum of the inflaton potential, and χ measures how fast the phase transition ends (χ ∼ the number of e-folds during the actual phase transition). Advanced LIGO will be able to test the validity of single-phase transition models within the parameter space 10 7  GeV∼< ε 1/4  ∼< 10 10  GeV and 0.19 ∼< χ ∼< 1. If inflation occurred through a first order phase transition, then Advanced LIGO could be the first to discover high frequency GW from inflation

  16. Enhanced gravity-wave activity and interhemispheric coupling during the MaCWAVE/MIDAS northern summer program 2002

    Directory of Open Access Journals (Sweden)

    E. Becker

    2006-07-01

    Full Text Available We present new sensitivity experiments that link observed anomalies of the mesosphere and lower thermosphere at high latitudes during the MaCWAVE/MIDAS summer program 2002 to enhanced planetary Rossby-wave activity in the austral winter troposphere.

    We employ the same general concept of a GCM having simplified representations of radiative and latent heating as in a previous study by Becker et al. (2004. In the present version, however, the model includes no gravity wave (GW parameterization. Instead we employ a high vertical and a moderate horizontal resolution in order to describe GW effects explicitly. This is supported by advanced, nonlinear momentum diffusion schemes that allow for a self-consistent generation of inertia and mid-frequency GWs in the lower atmosphere, their vertical propagation into the mesosphere and lower thermosphere, and their subsequent dissipation which is induced by prescribed horizontal and vertical mixing lengths as functions of height.

    The main anomalies in northern summer 2002 consist of higher temperatures than usual above 82 km, an anomalous eastward mean zonal wind between 70 and 90 km, an altered meridional flow, enhanced turbulent dissipation below 80 km, and enhanced temperature variations associated with GWs. These signals are all reasonably described by differences between two long-integration perpetual model runs, one with normal July conditions, and another run with modified latent heating in the tropics and Southern Hemisphere to mimic conditions that correspond to the unusual austral winter 2002. The model response to the enhanced winter hemisphere Rossby-wave activity has resulted in both an interhemispheric coupling through a downward shift of the GW-driven branch of the residual circulation and an increased GW activity at high summer latitudes. Thus a quantitative explanation of the dynamical state of the northern mesosphere and lower

  17. An intercomparison of stratospheric gravity wave potential energy densities from METOP GPS radio occultation measurements and ECMWF model data

    Science.gov (United States)

    Rapp, Markus; Dörnbrack, Andreas; Kaifler, Bernd

    2018-02-01

    Temperature profiles based on radio occultation (RO) measurements with the operational European METOP satellites are used to derive monthly mean global distributions of stratospheric (20-40 km) gravity wave (GW) potential energy densities (EP) for the period July 2014-December 2016. In order to test whether the sampling and data quality of this data set is sufficient for scientific analysis, we investigate to what degree the METOP observations agree quantitatively with ECMWF operational analysis (IFS data) and reanalysis (ERA-Interim) data. A systematic comparison between corresponding monthly mean temperature fields determined for a latitude-longitude-altitude grid of 5° by 10° by 1 km is carried out. This yields very low systematic differences between RO and model data below 30 km (i.e., median temperature differences is between -0.2 and +0.3 K), which increases with height to yield median differences of +1.0 K at 34 km and +2.2 K at 40 km. Comparing EP values for three selected locations at which also ground-based lidar measurements are available yields excellent agreement between RO and IFS data below 35 km. ERA-Interim underestimates EP under conditions of strong local mountain wave forcing over northern Scandinavia which is apparently not resolved by the model. Above 35 km, RO values are consistently much larger than model values, which is likely caused by the model sponge layer, which damps small-scale fluctuations above ˜ 32 km altitude. Another reason is the well-known significant increase of noise in RO measurements above 35 km. The comparison between RO and lidar data reveals very good qualitative agreement in terms of the seasonal variation of EP, but RO values are consistently smaller than lidar values by about a factor of 2. This discrepancy is likely caused by the very different sampling characteristics of RO and lidar observations. Direct comparison of the global data set of RO and model EP fields shows large correlation coefficients (0

  18. Gravity wave generation and propagation during geomagnetic storms over Kiruna (67.8°N, 20.4°E

    Directory of Open Access Journals (Sweden)

    P. R. Fagundes

    Full Text Available Atmospheric gravity waves, detected over Kiruna (67.8°N, 20.4°E during geomagnetic storms, are presented and analysed. The data include direct measurements of the OI 630.0 nm emission line intensity, the x-component of the local geomagnetic field and thermospheric (meridional and zonal wind velocities derived from the OI 630.0 nm Doppler shift observed with an imaging Fabry-Perot interferometer (IFPI. A low pass band filter technique was used to determine short-period variations in the thermospheric meridional wind velocities observed during geomagnetic storms. These short-period variations in the meridional wind velocities, which are identified as due to gravity waves, are compared to the corresponding variations observed in the OI 630.0 nm emission line intensity, x-component of the local geomagnetic field and the location of the auroral electrojet. A cross-correlation analysis was used to calculate the propagation velocities of the observed gravity waves.

  19. Gravity wave generation and propagation during geomagnetic storms over Kiruna (67.8°N, 20.4°E

    Directory of Open Access Journals (Sweden)

    P. R. Fagundes

    1995-04-01

    Full Text Available Atmospheric gravity waves, detected over Kiruna (67.8°N, 20.4°E during geomagnetic storms, are presented and analysed. The data include direct measurements of the OI 630.0 nm emission line intensity, the x-component of the local geomagnetic field and thermospheric (meridional and zonal wind velocities derived from the OI 630.0 nm Doppler shift observed with an imaging Fabry-Perot interferometer (IFPI. A low pass band filter technique was used to determine short-period variations in the thermospheric meridional wind velocities observed during geomagnetic storms. These short-period variations in the meridional wind velocities, which are identified as due to gravity waves, are compared to the corresponding variations observed in the OI 630.0 nm emission line intensity, x-component of the local geomagnetic field and the location of the auroral electrojet. A cross-correlation analysis was used to calculate the propagation velocities of the observed gravity waves.

  20. Power control for direct-driven permanent magnet wind generator system with battery storage.

    Science.gov (United States)

    Guang, Chu Xiao; Ying, Kong

    2014-01-01

    The objective of this paper is to construct a wind generator system (WGS) loss model that addresses the loss of the wind turbine and the generator. It aims to optimize the maximum effective output power and turbine speed. Given that the wind generator system has inertia and is nonlinear, the dynamic model of the wind generator system takes the advantage of the duty of the Buck converter and employs feedback linearization to design the optimized turbine speed tracking controller and the load power controller. According to that, this paper proposes a dual-mode dynamic coordination strategy based on the auxiliary load to reduce the influence of mode conversion on the lifetime of the battery. Optimized speed and power rapid tracking as well as the reduction of redundant power during mode conversion have gone through the test based on a 5 kW wind generator system test platform. The generator output power as the capture target has also been proved to be efficient.

  1. Incorporation of a Wind Generator Model into a Dynamic Power Flow Analysis

    Directory of Open Access Journals (Sweden)

    Angeles-Camacho C.

    2011-07-01

    Full Text Available Wind energy is nowadays one of the most cost-effective and practical options for electric generation from renewable resources. However, increased penetration of wind generation causes the power networks to be more depend on, and vulnerable to, the varying wind speed. Modeling is a tool which can provide valuable information about the interaction between wind farms and the power network to which they are connected. This paper develops a realistic characterization of a wind generator. The wind generator model is incorporated into an algorithm to investigate its contribution to the stability of the power network in the time domain. The tool obtained is termed dynamic power flow. The wind generator model takes on account the wind speed and the reactive power consumption by induction generators. Dynamic power flow analysis is carried-out using real wind data at 10-minute time intervals collected for one meteorological station. The generation injected at one point into the network provides active power locally and is found to reduce global power losses. However, the power supplied is time-varying and causes fluctuations in voltage magnitude and power fl ows in transmission lines.

  2. Wind generator based on cascade connection of two asynchronized synchronous machines

    International Nuclear Information System (INIS)

    Dzhagarov, N.; Dzhagarova, Yu.

    2000-01-01

    A model of a wind generator with two asynchronized synchronous machines presented and different regimes are investigated. The analysis shows that the suggested scheme of a brushless generator works and has more advantages (reliability, easy for operation) in comparison with the known ones

  3. Power Control for Direct-Driven Permanent Magnet Wind Generator System with Battery Storage

    Science.gov (United States)

    Guang, Chu Xiao; Ying, Kong

    2014-01-01

    The objective of this paper is to construct a wind generator system (WGS) loss model that addresses the loss of the wind turbine and the generator. It aims to optimize the maximum effective output power and turbine speed. Given that the wind generator system has inertia and is nonlinear, the dynamic model of the wind generator system takes the advantage of the duty of the Buck converter and employs feedback linearization to design the optimized turbine speed tracking controller and the load power controller. According to that, this paper proposes a dual-mode dynamic coordination strategy based on the auxiliary load to reduce the influence of mode conversion on the lifetime of the battery. Optimized speed and power rapid tracking as well as the reduction of redundant power during mode conversion have gone through the test based on a 5 kW wind generator system test platform. The generator output power as the capture target has also been proved to be efficient. PMID:25050405

  4. FUZZY LOGIC BASED INTELLIGENT CONTROL OF A VARIABLE SPEED CAGE MACHINE WIND GENERATION SYSTEM

    Science.gov (United States)

    The paper describes a variable-speed wind generation system where fuzzy logic principles are used to optimize efficiency and enhance performance control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which either pump...

  5. Statistical characterization of high-to-medium frequency mesoscale gravity waves by lidar-measured vertical winds and temperatures in the MLT

    Science.gov (United States)

    Lu, Xian; Chu, Xinzhao; Li, Haoyu; Chen, Cao; Smith, John A.; Vadas, Sharon L.

    2017-09-01

    We present the first statistical study of gravity waves with periods of 0.3-2.5 h that are persistent and dominant in the vertical winds measured with the University of Colorado STAR Na Doppler lidar in Boulder, CO (40.1°N, 105.2°W). The probability density functions of the wave amplitudes in temperature and vertical wind, ratios of these two amplitudes, phase differences between them, and vertical wavelengths are derived directly from the observations. The intrinsic period and horizontal wavelength of each wave are inferred from its vertical wavelength, amplitude ratio, and a designated eddy viscosity by applying the gravity wave polarization and dispersion relations. The amplitude ratios are positively correlated with the ground-based periods with a coefficient of 0.76. The phase differences between the vertical winds and temperatures (φW -φT) follow a Gaussian distribution with 84.2±26.7°, which has a much larger standard deviation than that predicted for non-dissipative waves ( 3.3°). The deviations of the observed phase differences from their predicted values for non-dissipative waves may indicate wave dissipation. The shorter-vertical-wavelength waves tend to have larger phase difference deviations, implying that the dissipative effects are more significant for shorter waves. The majority of these waves have the vertical wavelengths ranging from 5 to 40 km with a mean and standard deviation of 18.6 and 7.2 km, respectively. For waves with similar periods, multiple peaks in the vertical wavelengths are identified frequently and the ones peaking in the vertical wind are statistically longer than those peaking in the temperature. The horizontal wavelengths range mostly from 50 to 500 km with a mean and median of 180 and 125 km, respectively. Therefore, these waves are mesoscale waves with high-to-medium frequencies. Since they have recently become resolvable in high-resolution general circulation models (GCMs), this statistical study provides an important

  6. Operational performance of the Avispa-IIE wind generator in microhybrid systems

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez Galarza, Raul; Mejia Neri, Fortino [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1997-12-31

    The purpose of this paper is to make a general analysis over the operational performance of the Avispa-IIE wind generator in an Solar-Eolic hybrid installation, at an eco-tourist resort. This work was performed through the monitor of the wind generator and the system itself throughout a year, for the acquisition taking the variables of interest and operational parameters that might allow to characterize and to evaluate the general behavior of the system. Herein are the principals characteristics of the wind generator; its performance curve, the basic configuration of the installation and the control philosophy; Likewise, some technical and human problems which arise during the operation of the system are included, the implementation of improvements in the wind generator and the general results acquired during the time of operation of the wind generator in the cited installations. [Espanol] El proposito de este articulo es el hacer un analisis general del comportamiento operacional del aerogenerador Avispa-IIE en una instalacion hibrida Solar-Eolica en un lugar de veraneo eco-turistico. Este trabajo ha sido llevado a cabo mediante el monitor del aerogenerador y el sistema mismo por espacio de un ano, para la adquisicion de las variables de interes y de los parametros operacionales que pudieran servir para caracterizar y evaluar el comportamiento general del sistema. Aqui se incluyen las caracteristicas principales del aerogenerador; su curva de comportamiento, la configuracion basica de la instalacion y la filosofia del control. De la misma manera se incluyen algunos problemas tecnicos y humanos que se originan durante la operacion del sistema y la puesta en practica de las mejoras del aerogenerador y los resultados generales adquiridos durante el tiempo de operacion del aerogenerador en las instalaciones citadas.

  7. Assessing the value of wind generation in future carbon constrained electricity industries

    International Nuclear Information System (INIS)

    Vithayasrichareon, Peerapat; MacGill, Iain F.

    2013-01-01

    This paper employs a novel Monte-Carlo based generation portfolio assessment tool to explore the implications of increasing wind penetration and carbon prices within future electricity generation portfolios under considerable uncertainty. This tool combines optimal generation mix techniques with Monte Carlo simulation and portfolio analysis methods to determine expected overall generation costs, associated cost uncertainty and expected CO 2 emissions for different possible generation portfolios. A case study of an electricity industry with coal, Combined Cycle Gas Turbines (CCGT), Open Cycle Gas Turbines (OCGT) and wind generation options that faces uncertain future fossil-fuel prices, carbon pricing, electricity demand and plant construction costs is presented to illustrate some of the key issues associated with growing wind penetrations. The case study uses half-hourly demand and wind generation data from South Eastern Australia, and regional estimates of new-build plant costs and characteristics. Results suggest that although wind generation generally increases overall industry costs, it reduces associated cost uncertainties and CO 2 emissions. However, there are some cases in which wind generation can reduce the overall costs of generation portfolios. The extent to which wind penetration affects industry expected costs and uncertainties depends on the level of carbon price and the conventional technology mix in the portfolios. - Highlights: ► A probabilistic portfolio analysis tool to assess generation portfolios with wind power. ► Explore the impacts of wind penetrations and carbon prices under uncertainties. ► Wind generation increases overall portfolio costs but reduces cost risks and emissions. ► The value of wind power depends on the carbon price and the technology mix. ► Complex interactions between wind penetration level and carbon pricing.

  8. Experimental study on the effects of surface gravity waves of different wavelengths on the phase averaged performance characteristics of marine current turbine

    Science.gov (United States)

    Luznik, L.; Lust, E.; Flack, K. A.

    2014-12-01

    There are few studies describing the interaction between marine current turbines and an overlying surface gravity wave field. In this work we present an experimental study on the effects of surface gravity waves of different wavelengths on the wave phase averaged performance characteristics of a marine current turbine model. Measurements are performed with a 1/25 scale (diameter D=0.8m) two bladed horizontal axis turbine towed in the large (116m long) towing tank at the U.S. Naval Academy equipped with a dual-flap, servo-controlled wave maker. Three regular waves with wavelengths of 15.8, 8.8 and 3.9m with wave heights adjusted such that all waveforms have the same energy input per unit width are produced by the wave maker and model turbine is towed into the waves at constant carriage speed of 1.68 m/s. This representing the case of waves travelling in the same direction as the mean current. Thrust and torque developed by the model turbine are measured using a dynamometer mounted in line with the turbine shaft. Shaft rotation speed and blade position are measured using in in-house designed shaft position indexing system. The tip speed ratio (TSR) is adjusted using a hysteresis brake which is attached to the output shaft. Free surface elevation and wave parameters are measured with two optical wave height sensors, one located in the turbine rotor plane and other one diameter upstream of the rotor. All instruments are synchronized in time and data is sampled at a rate of 700 Hz. All measured quantities are conditionally sampled as a function of the measured surface elevation and transformed to wave phase space using the Hilbert Transform. Phenomena observed in earlier experiments with the same turbine such as phase lag in the torque signal and an increase in thrust due to Stokes drift are examined and presented with the present data as well as spectral analysis of the torque and thrust data.

  9. A study of Traveling Ionospheric Disturbances and Atmospheric Gravity Waves using EISCAT Svalbard Radar IPY-data

    Directory of Open Access Journals (Sweden)

    A. Vlasov

    2011-11-01

    Full Text Available We present a statistical study of Traveling Ionospheric Disturbances (TIDs as observed by the EISCAT Svalbard Radar (ESR during the continuous IPY-run (March 2007–February 2008 with field-aligned measurements. We have developed a semi-automatic routine for searching and extracting Atmospheric Gravity Wave (AGW activity. The collected data shows that AGW-TID signatures are common in the high-latitude ionosphere especially in the field-aligned ion velocity data (244 cases of AGW-TID signatures in daily records, but they can be observed also in electron density (26 cases, electron temperature (12 cases and ion temperature (26 cases. During the IPY campaign (in solar minimum conditions AGW-TID events appear more frequently during summer months than during the winter months. It remains still as a topic for future studies whether the observed seasonal variation is natural or caused by seasonal variation in the performance of the observational method that we use (AGW-TID signature may be more pronounced in a dense ionosphere. In our AGW-TID dataset the distribution of the oscillation periods has two peaks, one around 0.5–0.7 h and the other around 1.1–1.3 h. The diurnal occurrence rate has a deep minimum in the region of magnetic midnight, which might be partly explained by irregular auroral activity obscuring the TID signatures from our detection routines. As both the period and horizontal phase speed estimates (as derived from the classical AGW dispersion relation show values typical both for large scale TIDs and mesoscale TIDs it is difficult to distinguish whether the generator for high-latitude AGW-TIDs resides typically in the troposphere or in the near-Earth space. The results of our statistical analysis give anyway some valuable reference information for the future efforts to learn more about the dominating TID source mechanisms in polar cap conditions, and to improve AGW simulations.

  10. Ion layers, tides, gravity waves, and electric fields in the upper atmosphere, inferred from Arecibo incoherent scatter radar measurements

    International Nuclear Information System (INIS)

    Morton, Y.T.

    1991-01-01

    This thesis uses data accumulated during 1980-1989 by the Arecibo incoherent scatter radar to study the behavior and physics of ionization irregularities. Low latitude ionization irregularities, known as sporadic-E and intermediate layers, undergo a regular daily descent, convergence, and dumping of ion layers controlled by the neutral tidal wind. A useful way of studying ion layers and their motion is by ion layer trajectory maps which consist of points representing the altitude and time of ionization layers. Two types of maps were used which assigned either a uniform layer intensity or a gray level/pseudo-color to indicate different layer intensities. Important aspects of layer formation are revealed by map analysis. During January, intermediate layers consistently appeared four times per day instead of the normal twice per day pattern. Simulation of ion trajectories based on the ion momentum equation, which includes both Lorentzian and collisional forces, shows that a combination of diurnal, semidiurnal, and six-hour tides is necessary for such a feature to exist, whereas only diurnal and semidiurnal tides are needed to create the normal pattern. The six-hour period tide has not been previously reported. Extra or irregular layers appear frequently in layer trajectory maps, which can be simulated by the addition of gravity waves to the regular tidal wind system. Electric field effects are normally not a factor in low latitude ion layer formation because they are relatively weak and not commonly observed. Layer configurations during a geomagnetic storm, however, indicate that the electric field played an important role in controlling ion motion

  11. Three essays on the effect of wind generation on power system planning and operations

    Science.gov (United States)

    Davis, Clay Duane

    While the benefits of wind generation are well known, some drawbacks are still being understood as wind power is integrated into the power grid at increasing levels. The primary difference between wind generation and other forms of generation is the intermittent, and somewhat unpredictable, aspect of this resource. The somewhat uncontrollable aspect of wind generation makes it important to consider the relationship between this resource and load, and also how the operation of other non-wind generation resources may be affected. The three essays that comprise this dissertation focus on these and other important issues related to wind generation; leading to an improved understanding of how to better plan for and utilize this resource. The first essay addresses the cost of increased levels of installed wind capacity from both a capacity planning and economic dispatch perspective to arrive at the total system cost of installing a unit of wind capacity. This total includes not only the cost of the wind turbine and associated infrastructure, but also the cost impact an additional unit of wind capacity has on the optimal mix and operation of other generating units in the electricity supply portfolio. The results of the model showed that for all wind expansion scenarios, wind capacity is not cost-effective regardless of the level of the wind production tax credit and carbon prices that were considered. Larger levels of installed wind capacity result in reduced variable cost, but this reduction is not able to offset increases in capital cost, as a unit of installed wind capacity does not result in an equal reduction in other non-wind capacity needs. The second essay develops a methodology to better handle unexpected short term fluctuations in wind generation within the existing power system. The methodology developed in this essay leads to lower expected costs by anticipating and planning for fluctuations in wind generation by focusing on key constraints in the system. The

  12. The Effects of Surface Gravity Waves on Coastal Currents: Implementation, Phenomenological Explanation, and Realistic Simulation with ROMS

    Science.gov (United States)

    2008-05-30

    is a dynamical component of sea surface elevation and h is a local resting depth. The primary-wave-averaged effects, which we call WEC (wave effects on...empirical parameters related to wave breaking, and Hrm, is R.M.S. wave height. A comparative simulation with DUCK 94. The barotropic ROMS with WEC and the...driven by obliquely incident waves to beaches. The barotropic ROMS with WEC and CEW is used to carried out an experiment for reproducing shear waves

  13. Gravity wave intensity and momentum fluxes in the mesosphere over Shigaraki, Japan (35°N, 136°E during 1986-1997

    Directory of Open Access Journals (Sweden)

    N. M. Gavrilov

    Full Text Available Averaged seasonal variations of wind perturbation intensities and vertical flux of horizontal momentum produced by internal gravity waves (IGWs with periods 0.2-1 h and 1-6 h are studied at the altitudes 65-80 km using the MU radar measurement data from the middle and upper atmosphere during 1986-1997 at Shigaraki, Japan (35° N, 136° E. IGW intensity has maxima in winter and summer, winter values having substantial interannual variations. Mean wave momentum flux is directed to the west in winter and to the east in summer, opposite to the mean wind in the middle atmosphere. Major IGW momentum fluxes come to the mesosphere over Shigaraki from the Pacific direction in winter and continental Asia in summer.

    Key words: Meteorology and atmospheric dynamics (middle atmosphere dynamics; waves and tides · Ionosphere (ionospheric disturbances

  14. Improving Low Voltage Ride Through Capability of Wind Generators Using Dynamic Voltage Restorer

    Science.gov (United States)

    Sivasankar, Gangatharan; Suresh Kumar, Velu

    2014-08-01

    The increasing wind power integration with power grid has forced the situation to improve the reliability of wind generators for stable operation. One important problem with induction generator based wind farm is its low ride through capability to the grid voltage disturbance. Any disturbance such as voltage dip may cause wind farm outages. Since wind power contribution is in predominant percentage, such outages may lead to stability problem. The proposed strategy is to use dynamic voltage controller (DVR) to compensate the voltage disturbance. The DVR provides the wind generator the ability to remain connected in grid and improve the reliability. The voltage dips due to symmetrical and unsymmetrical faults are considered for analysis. The vector control scheme is employed for fault compensation which uses software phase locked loop scheme and park dq0 transformation technique. Extensive simulation results are included to illustrate the control and operation of DVR.

  15. Robust optimization-based DC optimal power flow for managing wind generation uncertainty

    Science.gov (United States)

    Boonchuay, Chanwit; Tomsovic, Kevin; Li, Fangxing; Ongsakul, Weerakorn

    2012-11-01

    Integrating wind generation into the wider grid causes a number of challenges to traditional power system operation. Given the relatively large wind forecast errors, congestion management tools based on optimal power flow (OPF) need to be improved. In this paper, a robust optimization (RO)-based DCOPF is proposed to determine the optimal generation dispatch and locational marginal prices (LMPs) for a day-ahead competitive electricity market considering the risk of dispatch cost variation. The basic concept is to use the dispatch to hedge against the possibility of reduced or increased wind generation. The proposed RO-based DCOPF is compared with a stochastic non-linear programming (SNP) approach on a modified PJM 5-bus system. Primary test results show that the proposed DCOPF model can provide lower dispatch cost than the SNP approach.

  16. Models for Numerical Evaluation of Variable Speed Different Wind Generator Systems

    DEFF Research Database (Denmark)

    Li, Hui; Chen, Zhe; Polinder, H.

    2007-01-01

    -effective wind conversion system among the various possible configurations. The aim of this project is to evaluate the suitable cost- effective wind generator systems by using the optimization designs and the numerical comparison. The research report is made of two parts, one focus on the design models......, the analytical models include the wind turbine power characteristics; the single/threestage gearbox and the power electronic converter for possible wind turbine concepts are described. Finally, the electromagnetic design models of the investigated generator topologies are presented, including the squirrel cage...... induction generator (SCIG), the doubly-fed induction generator (DFIG), the electrically excited synchronous generator (EESG) and permanent magnet synchronous generator (PMSG). Numerical evaluation with optimized design and comparison of variable speed wind generator systems by using the presented models...

  17. A comparative investigation of three PM-less MW power range wind generator topologies

    DEFF Research Database (Denmark)

    Bratiloveanu, Catalin-Rauti; Traian Cosmin Anghelus, Dumitru; Boldea, I.

    2012-01-01

    investigates by quasi 2D-FEM two dc stator polarized (to increase machine side PWM converter voltage utilization, that is to reduce peak kVA ratings and costs of the machine side PWM converter) directly-driven switched reluctance generators (one with circumferential field and one with transverse flux (with......-less topology are required before declaring them fit for industrial wind generators....

  18. Rating Requirements of the UPQC to Integrate the FSIG Type Wind Generation to the Grid

    OpenAIRE

    Jayanti, N.; Basu, Malabika; Conlon, Michael; Gaughan, Kevin

    2009-01-01

    The ability of wind generation to remain connected to the grid in the event of system faults and dynamic reactive power compensation are two aspects of grid integration, which have received particular attention. The wind driven, fixed-speed induction generator (FSIG) on its own fails to fulfil these requirements of grid integration. The application of a unified power quality conditioner (UPQC) to overcome the grid integration problems of the FSIG is investigated. The role of the UPQC in enhan...

  19. Small wind generators for battery charging in Peru and Sri Lanka

    Energy Technology Data Exchange (ETDEWEB)

    Dunnett, S. [Intermediate Technology Development Group, Rugby (United Kingdom)

    2000-07-01

    The Intermediate Technology Development Group (ITDG) have developed a small wind generator (SWG) intended primarily for battery charging in Peru and Sri Lanka. The project is funded mainly by the Department for International Development (DfID) and aims to provide rural households and communities who do not have access to mains electricity with a form of electrification. This paper reports on progress to date and is correct at the time of going to press, but subsequent changes to specifications may occur. (Author)

  20. A Fault Diagnostic Method for Position Sensor of Switched Reluctance Wind Generator

    DEFF Research Database (Denmark)

    Wang, Chao; Liu, Xiao; Liu, Hui

    2016-01-01

    Fast and accurate fault diagnosis of the position sensor is of great significance to ensure the reliability as well as sensor fault tolerant operation of the Switched Reluctance Wind Generator (SRWG). This paper presents a fault diagnostic scheme for a SRWG based on the residual between the estim...... conditions. The results provide a feasible theoretical and technical basis for the effective condition monitoring and predictive maintenance of SRWG....

  1. Capacity Value of PV and Wind Generation in the NV Energy System

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Shuai; Diao, Ruisheng; Samaan, Nader A.; Etingov, Pavel V.

    2014-03-21

    Calculation of photovoltaic (PV) and wind power capacity values is important for estimating additional load that can be served by new PV or wind installations in the electrical power system. It also is the basis for assigning capacity credit payments in systems with markets. Because of variability in solar and wind resources, PV and wind generation contribute to power system resource adequacy differently from conventional generation. Many different approaches to calculating PV and wind generation capacity values have been used by utilities and transmission operators. Using the NV Energy system as a study case, this report applies peak-period capacity factor (PPCF) and effective load carrying capability (ELCC) methods to calculate capacity values for renewable energy sources. We show the connection between the PPCF and ELCC methods in the process of deriving a simplified approach that approximates the ELCC method. This simplified approach does not require generation fleet data and provides the theoretical basis for a quick check on capacity value results of PV and wind generation. The diminishing return of capacity benefit as renewable generation increases is conveniently explained using the simplified capacity value approach.

  2. In-situ electron and ion measurements and observed gravity wave effects in the polar mesosphere during the MaCWAVE program

    Directory of Open Access Journals (Sweden)

    C. L. Croskey

    2006-07-01

    Full Text Available Langmuir probe electron and ion measurements from four instrumented rockets flown during the MaCWAVE (Mountain and Convective Waves Ascending VErtically program are reported. Two of the rockets were launched from Andøya Rocket Range, Norway, in the summer of 2002. Electron scavenging by ice particulates produced reductions of the electron density in both sharp narrow (≈1–2 km layers and as a broad (≈13 km depletion. Small-scale irregularities were observed in the altitude regions of both types of electron depletion. The scale of the irregularities extended to wavelengths comparable to those used by ground-based radars in observing PMSE. In regions where ice particles were not present, analysis of the spectral signatures provided reasonable estimates of the energy deposition from breaking gravity waves. Two more instrumented rockets were flown from Esrange, Sweden, in January 2003. Little turbulence or energy deposition was observed during one flight, but relatively large values were observed during the other flight. The altitude distribution of the observed turbulence was consistent with observations of a semidiurnal tide and gravity wave instability effects as determined by ground-based lidar and radar measurements and by falling sphere measurements of the winds and temperatures (Goldberg et al., 2006; Williams et al., 2006.

  3. Gravity-wave effects on tracer gases and stratospheric aerosol concentrations during the 2013 ChArMEx campaign

    Directory of Open Access Journals (Sweden)

    F. Chane Ming

    2016-07-01

    Full Text Available Coupled balloon-borne observations of Light Optical Aerosol Counter (LOAC, M10 meteorological global positioning system (GPS sondes, ozonesondes, and GPS radio occultation data, are examined to identify gravity-wave (GW-induced fluctuations on tracer gases and on the vertical distribution of stratospheric aerosol concentrations during the 2013 ChArMEx (Chemistry-Aerosol Mediterranean Experiment campaign. Observations reveal signatures of GWs with short vertical wavelengths less than 4 km in dynamical parameters and tracer constituents, which are also correlated with the presence of thin layers of strong local enhancements of aerosol concentrations in the upper troposphere and the lower stratosphere. In particular, this is evident from a case study above Ile du Levant (43.02° N, 6.46° E on 26–29 July 2013. Observations show a strong activity of dominant mesoscale inertia GWs with horizontal and vertical wavelengths of 370–510 km and 2–3 km respectively, and periods of 10–13 h propagating southward at altitudes of 13–20 km during 27–28 July. The European Centre for Medium-Range Weather Forecasts (ECMWF analyses also show evidence of mesoscale inertia GWs with similar horizontal characteristics above the eastern part of France. Ray-tracing experiments indicate the jet-front system as the main source of observed GWs. Using a simplified linear GW theory, synthetic vertical profiles of dynamical parameters with large stratospheric vertical wind maximum oscillations of ±40 mms−1 are produced for the dominant mesoscale GW observed at heights of 13–20 km. Parcel advection method reveals signatures of GWs in the ozone mixing ratio and the tropospheric-specific humidity. Simulated vertical wind perturbations of the dominant GWs and small-scale perturbations of aerosol concentration (aerosol size of 0.2–0.7 µm are revealed to be in phase in the lower stratosphere. Present results support the importance of

  4. Investigating the Role of Gravity Wave on Equatorial Ionospheric Irregularities using SABER and C/NOFS Satellites Observations

    Science.gov (United States)

    Nigussie, M.; Damtie, B.; Moldwin, M.; Yizengaw, E.; Tesema, F.; Tebabal, A.

    2017-12-01

    Theoretical simulations have shown that gravity wave (GW) seeded perturbations amplified by Rayleigh-Taylor Instability (RTI) results in ESF (equatorial spread F); however, there have been limited observational studies using simultaneous observations of GW and ionospheric parameters. In this paper, for the fist time, simultaneous atmospheric temperature perturbation profiles that are due to GWs obtained from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on-board the TIMED satellite and equatorial in -situ ion density and vertical plasma drift velocity observations with and without ESF activity obtained from C/NOFS satellites are used to investigate the effect of GW on the generation of ESF. The horizontal and vertical wavelengths of ionospheric oscillations and GWs respectively have been estimated applying wavelet transforms. Cross wavelet analysis has also been applied between two closely observed profiles of temperature perturbations to estimate the horizontal wavelength of the GWs. Moreover, vertically propagating GWs that dissipate energy at the upper atmosphere have been investigated using spectral analysis compared with theoretical results. The analysis show that when the ion density shows strong post sunset irregularity between 20 and 24 LT, vertically upward drift velocities increase between 17 and 19 LT, but it becomes vertically downward when the ion density shows smooth variation. The horizontal wavelengths estimated from C/NOFS and SABER observations show excellent agreement when ion density observations show strong fluctuations; otherwise, they have poor agreement. It is also found that altitude profiles of potential energy of GW increases up to 90 km and then decreases significantly. It is found that the vertical wavelength of GW, corresponding to the dominant spectral power, ranges from about 7 km to 20 km regardless of the situation of the ionosphere; however, GWs with vertical wavelengths between 100 m to 1 km are found to

  5. Techniques for studying gravity waves and turbulence: Vertical wind speed power spectra from the troposphere and stratosphere obtained under light wind conditions

    Science.gov (United States)

    Ecklund, W. L.; Balsley, B. B.; Crochet, M.; Carter, D. A.; Riddle, A. C.; Garello, R.

    1983-01-01

    A joint France/U.S. experiment was conducted near the mouth of the Rhone river in southern France as part of the ALPEX program. This experiment used 3 vertically directed 50 MHz radars separated by 4 to 6 km. The main purpose of this experiment was to study the spatial characteristics of gravity waves. The good height resolution (750 meters) and time resolution (1 minute) and the continuous operation over many weeks have yielded high resolution vertical wind speed power spectra under a variety of synoptic conditions. Vertical spectra obtained during very quiet (low wind) conditions in the troposphere and lower stratosphere from a single site are presented.

  6. Propagation of gravity waves and spread F in the low-latitude ionosphere over Tucumán, Argentina, by continuous Doppler sounding: First results

    Czech Academy of Sciences Publication Activity Database

    Chum, Jaroslav; Bonomi, F. A. M.; Fišer, Jiří; Cabrera, M. A.; Ezquer, R. G.; Burešová, Dalia; Laštovička, Jan; Baše, Jiří; Hruška, František; Molina, M. G.; Ise, J. E.; Cangemi, J. I.; Šindelářová, Tereza

    2014-01-01

    Roč. 119, č. 8 (2014), s. 6954-6965 ISSN 2169-9380 R&D Projects: GA ČR(CZ) GAP209/12/2440; GA ČR GP13-09778P Institutional support: RVO:68378289 Keywords : low latitude ionosphere * Ionospheric irregularities * equatorial spread F * gravity waves * scintillation * remote sensing * Doppler sounding Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 3.426, year : 2014 http://onlinelibrary.wiley.com/doi/10.1002/2014JA020184/abstract

  7. Terrestrial Gravity Fluctuations

    Directory of Open Access Journals (Sweden)

    Jan Harms

    2015-12-01

    Full Text Available Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^–23 Hz^–1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our

  8. Terrestrial Gravity Fluctuations

    Science.gov (United States)

    Harms, Jan

    2015-12-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10-23 Hz-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  9. Joint inversion of ambient noise surface wave and gravity data to image the upper crustal structure of the Tanlu fault zone to the southeast of Hefei, China

    Science.gov (United States)

    Wang, K.; Gu, N.; Zhang, H.; Zhou, G.

    2017-12-01

    The Tanlu fault is a major fault located in the eastern China, which stretches 2400 km long from Tancheng in the north to Lujiang in the south. It is generally believed that the Tanlu fault zone was formed in Proterozoic era and underwent a series of complicated processes since then. To understand the upper crustal structure around the southern segment of the Tanlu fault zone, in 2017 we deployed 53 short period seismic stations around the fault zone to the southeast of Hefei, capital city of Anhui province. The temporary array continuously recorded the data for about one month from 17 March to 26 April 2017. The seismic array spans an area of about 30km x 30Km with an average station spacing of about 5-6km. The vertical component data were used for extracting Rayleigh wave phase and group velocity dispersion data for the period of 0.2 to 5 seconds. To improve imaging the upper crustal structure of the fault zone, we jointly inverted the surface wave dispersion data and the gravity data because they have complementary strengths. To combine surface wave dispersion data and gravity observations into a single inversion framework, we used an empirical relationship between seismic velocity and density of Maceira and Ammon (2009). By finding the optimal relative weighting between two data types, we are able to find a shear wave velocity (Vs) model that fits both data types. The joint inversion can resolve the upper crustal fault zone structure down to about 7 km in depth. The Vs model shows that in this region the Tanlu fault is associated with high velocity anomalies, corresponding well to the Feidong complex seen on the surface. This indicates that the Tanlu fault zone may provide a channel for the intrusion of hot materials.

  10. Characterisation of Large Disturbance Rotor Angle and Voltage Stability in Interconnected Power Networks with Distributed Wind Generation

    OpenAIRE

    Meegahapola, Lasantha; Littler, Timothy

    2015-01-01

    Wind generation in highly interconnected power networks creates local and centralised stability issues based on their proximity to conventional synchronous generators and load centres. This paper examines the large disturbance stability issues (i.e. rotor angle and voltage stability) in power networks with geographically distributed wind resources in the context of a number of dispatch scenarios based on profiles of historical wind generation for a real power network. Stability issues have be...

  11. In-situ electron and ion measurements and observed gravity wave effects in the polar mesosphere during the MaCWAVE program

    Directory of Open Access Journals (Sweden)

    C. L. Croskey

    2006-07-01

    Full Text Available Langmuir probe electron and ion measurements from four instrumented rockets flown during the MaCWAVE (Mountain and Convective Waves Ascending VErtically program are reported. Two of the rockets were launched from Andøya Rocket Range, Norway, in the summer of 2002. Electron scavenging by ice particulates produced reductions of the electron density in both sharp narrow (≈1–2 km layers and as a broad (≈13 km depletion. Small-scale irregularities were observed in the altitude regions of both types of electron depletion. The scale of the irregularities extended to wavelengths comparable to those used by ground-based radars in observing PMSE. In regions where ice particles were not present, analysis of the spectral signatures provided reasonable estimates of the energy deposition from breaking gravity waves.

    Two more instrumented rockets were flown from Esrange, Sweden, in January 2003. Little turbulence or energy deposition was observed during one flight, but relatively large values were observed during the other flight. The altitude distribution of the observed turbulence was consistent with observations of a semidiurnal tide and gravity wave instability effects as determined by ground-based lidar and radar measurements and by falling sphere measurements of the winds and temperatures (Goldberg et al., 2006; Williams et al., 2006.

  12. Potential for increased wind-generated electricity utilization using heat pumps in urban areas

    International Nuclear Information System (INIS)

    Waite, Michael; Modi, Vijay

    2014-01-01

    Highlights: • Large-scale wind power and increased electric heat pumps were evaluated. • A deterministic model of wind power and electricity demand was developed. • Sub-models for space heating and domestic hot water demand were developed. • Increased use of heat pumps can improve the viability of large-scale wind power. • Larger wind power capacity can meet a target utilization rate with more heat pumps. - Abstract: The U.S. has substantial wind power potential, but given wind’s intermittent availability and misalignment with electricity demand profiles, large-scale deployment of wind turbines could result in high electricity costs due to energy storage requirements or low utilization rates. While fuel switching and heat pumps have been proposed as greenhouse gas (GHG) emissions and energy reduction strategies at the building scale, this paper shows that heat pump adoption could have additional system-wide benefits by increasing the utilization of wind-generated electricity. A model was developed to evaluate the effects of coupling large-scale wind power installations in New York State with increased use of electric heat pumps to meet a portion of space heating and domestic hot water (DHW) demands in New York City. The analysis showed significant increases in wind-generated electricity utilization with increased use of heat pumps, allowing for higher installed capacity of wind power. One scenario indicates that 78.5% annual wind-generated electricity utilization can be achieved with 3 GW of installed wind power capacity generated electricity equal to 20% of existing NYC annual electricity demand; if 20% of space heating and DHW demands are provided by heat pumps, the 78.5% utilization rate can be achieved with an increase of total wind power capacity to 5 GW. Therefore, this integrated supply–demand approach could provide additional system-wide emissions reductions

  13. Determining the impact of wind on system costs via the temporal patterns of load and wind generation

    International Nuclear Information System (INIS)

    Davis, Clay D.; Gotham, Douglas J.; Preckel, Paul V.; Liu, Andrew L.

    2013-01-01

    Ambitious targets have been set for expanding electricity generation from renewable sources, including wind. Expanding wind power impacts needs for other electricity generating resources. As states plan for increasing levels of wind generation in their portfolio of generation resources it is important to consider how this intermittent resource impacts the need for other generation resources. A case study for Indiana estimates the value of wind capacity and demonstrates how to optimize its level and the levels of other generation resources. Changes are driven by temporal patterns of wind power output and load. System wide impacts are calculated for energy, capacity, and costs under multiple wind expansion scenarios which highlight the geographic characteristics of a systems portfolio of wind generation. The impacts of carbon prices, as proposed in the Bingaman Bill, are considered. Finally, calculations showing the effect increasing levels of wind generation will have on end use Indiana retail rates are included. - Highlights: • We estimate the value of wind capacity. • We determine wind generation's impact on the optimal mix of non-wind generation. • Optimal levels of wind and non-wind generation are determined. • We consider the impact of a carbon price on the optimal mix of resources. • The impact of additional wind capacity on Indiana residential rates is calculated

  14. Rotor Position Estimation for Switched Reluctance Wind Generator Using Extreme Learning Machine

    DEFF Research Database (Denmark)

    Wang, Chao; Liu, Xiao; Chen, Zhe

    2014-01-01

    Switched reluctance generator (SRG) is becoming more and more attractive in wind energy applications mainly because of its high fault tolerant ability and high reliability. The position sensor is one of the vulnerable points of the SRG when exposed to harsh environments such as offshore where many...... Reluctance Wind Generator (SRWG) based on Extreme Learning Machine (ELM) which could build a nonlinear mapping between flux linkage-current and rotor position. The learning data are derived from magnetization curves of the SRWG which are obtained from Finite Element Analysis (FEA) of an SRG with 8/6 stator...

  15. Loss Minimizing Operation of Doubly Fed Induction Generator Based Wind Generation Systems Considering Reactive Power Provision

    DEFF Research Database (Denmark)

    Baohua, Zhang; Hu, Weihao; Chen, Zhe

    2014-01-01

    The paper deals with control techniques for minimizing the operating loss of doubly fed induction generator based wind generation systems when providing reactive power. The proposed method achieves its goal through controlling the rotor side q-axis current in the synchronous reference frame....... The formula for the control reference is explicitly deduced in this paper considering the losses of the generator, the power electronic devices and the filter. Three control strategies are compared with the proposed method under different wind speeds and different reactive power references. The simulation...

  16. Analytical Derivation of Electrical-Side Maximum Power Line for Wind Generators

    Directory of Open Access Journals (Sweden)

    Sergei Kolesnik

    2017-09-01

    Full Text Available In order to enhance the maximum power point tracking (MPPT speed of solar generators, offline calculated maximum power line (MPL is often used as a feed-forward signal added to the output of MPPT controller. MPL is nonlinear static electrical characteristic of renewable energy generators connecting all the maximum power points for given temperature. In this letter, electrical side MPL is derived for a typical wind turbine generator (WTG. It is shown that MPLs of solar and wind generators possess similar structure, supporting the similarity between the two energy conversion processes.

  17. Coordinated control of wind generation and energy storage for power system frequency regulation

    Science.gov (United States)

    Baone, Chaitanya Ashok

    Large-scale centralized synchronous generators have long been the primary actors in exercising active power and frequency control, and much of the existing grid control framework is predicated upon their dynamic terminal characteristics. Important among these characteristics is the inertia of such generators. These play key roles in determining the electromechanical stability of the electric power grid. Modern wind generator systems are partially or fully connected to the grid through power electronic interfaces, and hence do not present the same level of inertial coupling. The absence of inertial frequency response from modern wind generator systems is a topic of growing concern in power engineering practice, as the penetration of wind generation is expected to grow dramatically in the next few years. Solutions proposed in the literature have sought to address this problem by seeking to mimic the inherent inertial response characteristics of traditional synchronous generators via control loops added to wind generators. Recent literature has raised concerns regarding this approach, and the work here will further examine its shortcomings, motivating approaches that seek to optimally design for the characteristics of the equipment exercising the control, rather than forcing new technologies to mimic the characteristics of synchronous machines. In particular, this work will develop a new approach to power system frequency regulation, with features suited to distributed energy storage devices such as grid-scale batteries and wind turbine speed and blade pitch control. The dynamic characteristics of these new technologies are treated along with existing mechanisms, such as synchronous machine governor control, to develop a comprehensive multi-input control design approach. To make the method practically feasible for geographically distributed power systems, an observer-based distributed control design utilizing phasor measurement unit (PMU) signals along with local

  18. Floating wind generators offshore wind farm: Implications for structural loads and control actions

    International Nuclear Information System (INIS)

    Garcia, E.; Morant F, Quiles E.; Correcher, A.

    2009-01-01

    This paper describes the work currently carried out in the design of floating wind generators and their involvement in the future development of power generation in marine farms in depths exceeding 20 m. We discuss the main issues to be taken into account in the design of floating platforms, including the involvement of structural loads they bear. Also from a standpoint of control engineering are discussed strategies to reduce structural loads such a system to ensure adequate durability and therefore ensuring their economic viability. Finally, the abstract modeling tools for floating wind turbines that can be used in both structural design and the design of appropriate control algorithms

  19. Sensitivity of the Freie Universität Berlin Climate Middle Atmosphere Model (FUB-CMAM to different gravity-wave drag parameterisations

    Directory of Open Access Journals (Sweden)

    P. Mieth

    2004-09-01

    Full Text Available We report the sensitivity of the Berlin Climate Middle Atmosphere Model (CMAM to different gravity-wave (GW parameterisations. We perform five perpetual January experiments: 1 Rayleigh friction (RF (control, 2 non-orographic GWs, 3 orographic GWs, 4 orographic and non-orographic GWs with no background stress, and 5 as for 4 but with background stress. We also repeat experiment 4 but for July conditions. Our main aim is to improve the model climatology by introducing orographic and non-orographic parameterisations and to investigate the individual effect of these schemes in the Berlin CMAM. We compare with an RF control to determine the improvement upon a previously-published model version employing RF. Results are broadly similar to previously-published works. The runs having both orographic and non-orographic GWs produce a statistically-significant warming of 4-8K in the wintertime polar lower stratosphere. These runs also feature a cooling of the warm summer pole in the mesosphere by 10-15K, more in line with observations. This is associated with the non-orographic GW scheme. This scheme is also associated with a heating feature in the winter polar upper stratosphere directly below the peak GW-breaking region. The runs with both orographic and non-orographic GWs feature a statistically-significant deceleration in the polar night jet (PNJ of 10-20ms-1 in the lower stratosphere. Both orographic and non-orographic GWs individually produce some latitudinal tilting of the polar jet with height, although the main effect comes from the non-orographic waves. The resulting degree of tilt, although improved, is nevertheless still weaker than that observed. Accordingly, wintertime variability in the zonal mean wind, which peaks at the edge of the vortex, tends to maximise too far polewards in the model compared with observations. Gravity-planetary wave interaction leads to a decrease in the amplitudes of stationary planetary waves 1 and 2 by up to 50% in

  20. Sensitivity of the Freie Universität Berlin Climate Middle Atmosphere Model (FUB-CMAM to different gravity-wave drag parameterisations

    Directory of Open Access Journals (Sweden)

    P. Mieth

    2004-09-01

    Full Text Available We report the sensitivity of the Berlin Climate Middle Atmosphere Model (CMAM to different gravity-wave (GW parameterisations. We perform five perpetual January experiments: 1 Rayleigh friction (RF (control, 2 non-orographic GWs, 3 orographic GWs, 4 orographic and non-orographic GWs with no background stress, and 5 as for 4 but with background stress. We also repeat experiment 4 but for July conditions. Our main aim is to improve the model climatology by introducing orographic and non-orographic parameterisations and to investigate the individual effect of these schemes in the Berlin CMAM. We compare with an RF control to determine the improvement upon a previously-published model version employing RF. Results are broadly similar to previously-published works. The runs having both orographic and non-orographic GWs produce a statistically-significant warming of 4-8K in the wintertime polar lower stratosphere. These runs also feature a cooling of the warm summer pole in the mesosphere by 10-15K, more in line with observations. This is associated with the non-orographic GW scheme. This scheme is also associated with a heating feature in the winter polar upper stratosphere directly below the peak GW-breaking region. The runs with both orographic and non-orographic GWs feature a statistically-significant deceleration in the polar night jet (PNJ of 10-20ms-1 in the lower stratosphere. Both orographic and non-orographic GWs individually produce some latitudinal tilting of the polar jet with height, although the main effect comes from the non-orographic waves. The resulting degree of tilt, although improved, is nevertheless still weaker than that observed. Accordingly, wintertime variability in the zonal mean wind, which peaks at the edge of the vortex, tends to maximise too far polewards in the model compared with observations. Gravity-planetary wave interaction leads to a decrease in the amplitudes of stationary planetary waves 1 and 2 by

  1. Effect of phase coupling on surface amplitude distribution of wind waves

    Digital Repository Service at National Institute of Oceanography (India)

    Varkey, M.J.

    Nonlinear features of wind generated surface waves are considered here to be caused by nonrandomness (non-Uniform) in the phase spectrum. Nonrandomness in recorded waves, if present, would be generally obscured within the error level of observations...

  2. Observational signatures of unusual outgoing longwave radiation (OLR) and atmospheric gravity waves (AGW) as precursory effects of May 2015 Nepal earthquakes

    Science.gov (United States)

    Chakraborty, Suman; Sasmal, Sudipta; Chakrabarti, Sandip K.; Bhattacharya, Arnab

    2018-01-01

    Earthquake preparation processes may start 1-30 days before its actual occurrence. Measurements of outgoing longwave radiation (OLR) and detection of the presence of atmospheric gravity waves (AGW) in very low frequency (VLF) radio signals can be used as tools to identify such processes. We studied these signals monitored prior to a recent major earthquake that occurred in Nepal at southeast of Kodari on May 12, 2015 at 12:50 pm local time (07:05 UTC) with Richter scale magnitude of M = 7.3 and depth 10 km (6.21 miles). It was preceded by another major earthquake on April 25, 2015 with magnitude M = 7.9. First, to study the effects of seismic events on OLR, we used NOAA/IR daily (two degree gridded) data from April 16 to May 30, 2015 and followed the method of Eddy field calculation mean to find pre-seismic anomalies. We found singularities in Eddy field OLR curves around the earthquake epicenter starting 3 days prior to the earthquake days and disappearance of such singularities after the events. Such singularities can be associated with a large amount of energy released by the earthquakes. Second, we analyzed very low frequency (VLF) data recorded at Ionospheric and Earthquake Research Centre (IERC) of Indian Centre for Space Physics transmitted from JJI (22.2 kHz) station of Japan. We looked for the presence of atmospheric gravity waves in the ionosphere which can be considered as an important factor in finding seismo-ionospheric correlations. We performed both fast Fourier transform (FFT) and wavelet analysis on the signal and found significant presence of such waves (periods of almost 1 h) four days before the earthquake.

  3. Low Voltage Ride-through in DFIG Wind Generators by Controlling the Rotor Current without Crowbars

    Directory of Open Access Journals (Sweden)

    Jaime Rodríguez Arribas

    2014-01-01

    Full Text Available Among all the different types of electric wind generators, those that are based on doubly fed induction generators, or DFIG technology, are the most vulnerable to grid faults such as voltage sags. This paper proposes a new control strategy for this type of wind generator, that allows these devices to withstand the effects of a voltage sag while following the new requirements imposed by grid operators. This new control strategy makes the use of complementary devices such as crowbars unnecessary, as it greatly reduces the value of currents originated by the fault. This ensures less costly designs for the rotor systems as well as a more economic sizing of the necessary power electronics. The strategy described here uses an electric generator model based on space-phasor theory that provides a direct control over the position of the rotor magnetic flux. Controlling the rotor magnetic flux has a direct influence on the rest of the electrical variables enabling the machine to evolve to a desired work point during the transient imposed by the grid disturbance. Simulation studies have been carried out, as well as test bench trials, in order to prove the viability and functionality of the proposed control strategy.

  4. Design and analysis of a flux intensifying permanent magnet embedded salient pole wind generator

    Science.gov (United States)

    Guo, Yujing; Jin, Ping; Lin, Heyun; Yang, Hui; Lyu, Shukang

    2018-05-01

    This paper presents an improved flux intensifying permanent magnet embedded salient pole wind generator (FI-PMESPWG) with mirror symmetrical magnetizing directions permanent magnet (PM) for improving generator's performances. The air-gap flux densities, the output voltage, the cogging torque and the d- and q-axis inductances of FI-PMESPWG are all calculated and analyzed by using the finite element method (FEM). To highlight the advantages of the proposed FI-PMESPWG, an original permanent magnet embedded salient pole wind generator (PMESPWG) model is adopted for comparison under the same operating conditions. The calculating results show that the air-gap flux densities of FI-PMESPWG are intensified with the same magnet amounts because the PMs are set in a form of V shape in each pole. The difference between d-axis inductance and q-axis inductance of the proposed FI-PMESPWG is reduced. Thus, the output power of the proposed FI-PMESPWG reaches a higher value than that of the original PMESPWG at the same current phase angle. The cogging torque is diminished because the flux path is changed. All the analysis results indicate that the electromagnetic characteristics of the proposed FI-PMESPWG are significantly better than that of the original PMESPWG.

  5. Greener corona discharge for enhanced wind generation with a simple dip-coated carbon nanotube decoration

    Science.gov (United States)

    Wu, Yishan; Li, Jun; Ye, Jianchun; Chen, Xiaohong; Li, Huili; Huang, Sumei; Zhao, Ran; Ou-Yang, Wei

    2017-10-01

    Corona discharge-induced wind (CDIW) has been widely utilized in production lines in the food and semiconductor industries and in indoor devices such as electrostatic precipitators. Some ozone is inevitably emitted, posing serious health risks to respiratory system and lung function of a human being. In this work, a greener corona discharge with enhanced wind generation for a needle-to-cylinder discharge structure is demonstrated using a simple dip-coating method to attach carbon nanotubes (CNTs) to the discharge electrode of a stainless steel needle. Compared with a conventional discharge electrode without CNT decoration, the velocity of the CDIW is greatly enhanced, the onset voltage is lowered, the energy conversion efficiency is greatly improved and the concentration of generated ozone is much reduced, making this easy method of CNT decoration a promising candidate for greener corona discharge systems. In addition, several impact factors for improved performance are discussed mathematically and phenomenologically, providing an insight into the corona discharge and wind generation.

  6. The Effects of Surface Gravity Waves on Coastal Currents: Implementation, Phenomenological Explanation, and Realistic Simulation with ROMS

    National Research Council Canada - National Science Library

    McWilliams, James C; Uchiyama, Yusuke

    2008-01-01

    ... (Uchiyama and McWilliams, 2008). An investigation of shear instability due to breaking-wave-driven barotropic littoral currents on a barred beach is being carried out by extending the asymptotic theory appropriate for a strong current regime near surf zones with a parameterized, non-conservative wave breaking (Uchiyama et al., 2008).

  7. Numerical simulation and analysis of impact of non-orographic gravity waves drag of middle atmosphere in framework of a general circulation model

    Science.gov (United States)

    Zhao, J.; Wang, S.

    2017-12-01

    Gravity wave drag (GWD) is among the drivers of meridional overturning in the middle atmosphere, also known as the Brewer-Dobson Circulation, and of the quasi-biennial oscillation (QBO). The small spatial scales and complications due to wave breaking require their effects to be parameterised. GWD parameterizations are usually divided into two parts, orographic and non-orographic. The basic dynamical and physical processes of the middle atmosphere and the mechanism of the interactions between the troposphere and the middle atmosphere were studied in the frame of a general circulation model. The model for the troposphere was expanded to a global model considering middle atmosphere with the capability of describing the basic processes in the middle atmosphere and the troposphere-middle atmosphere interactions. Currently, it is too costly to include full non-hydrostatic and rotational wave dynamics in an operational parameterization. The hydrostatic non-rotational wave dynamics which allow an efficient implementation that is suitably fast for operation. The simplified parameterization of non-orographic GWD follows from the WM96 scheme in which a framework is developed using conservative propagation of gravity waves, critical level filtering, and non-linear dissipation. In order to simulate and analysis the influence of non-orographic GWD on the stratospheric wind and temperature fields, experiments using Stratospheric Sudden Warming (SSW) event case occurred in January 2013 were carried out, and results of objective weather forecast verifications of the two months period were compared in detail. The verification of monthly mean of forecast anomaly correlation (ACC) and root mean square (RMS) errors shows consistently positive impact of non-orographic GWD on skill score of forecasting for the three to eight days, both in the stratosphere and troposphere, and visible positive impact on prediction of the stratospheric wind and temperature fields. Numerical simulation

  8. Analysis of gravity waves in the tropical middle atmosphere over La Reunion Island (21°S, 55°E with lidar using wavelet techniques

    Directory of Open Access Journals (Sweden)

    F. Chane-Ming

    2000-04-01

    Full Text Available The capabilities of the continuous wavelet transform (CWT and the multiresolution analysis (MRA are presented in this work to measure vertical gravity wave characteristics. Wave properties are extracted from the first data set of Rayleigh lidar obtained between heights of 30 km and 60 km over La Reunion Island (21°S, 55°E during the Austral winter in 1994 under subtropical conditions. The altitude-wavelength representations deduced from these methods provide information on the time and spatial evolution of the wave parameters of the observed dominant modes in vertical profiles such as the vertical wavelengths, the vertical phase speeds, the amplitudes of temperature perturbations and the distribution of wave energy. The spectra derived from measurements show the presence of localized quasi-monochromatic structures with vertical wavelengths <10 km. Three methods based on the wavelet techniques show evidence of a downward phase progression. A first climatology of the dominant modes observed during the Austral winter period reveals a dominant night activity of 2 or 3 quasi-monochromatic structures with vertical wavelengths between 1-2 km from the stratopause, 3-4 km and 6-10 km observed between heights of 30 km and 60 km. In addition, it reveals a dominant activity of modes with a vertical phase speed of -0.3 m/s and observed periods peaking at 3-4 h and 9 h. The characteristics of averaged vertical wavelengths appear to be similar to those observed during winter in the southern equatorial region and in the Northern Hemisphere at mid-latitudes.Key words: Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; waves and tides

  9. Analysis of gravity waves in the tropical middle atmosphere over La Reunion Island (21°S, 55°E with lidar using wavelet techniques

    Directory of Open Access Journals (Sweden)

    F. Chane-Ming

    Full Text Available The capabilities of the continuous wavelet transform (CWT and the multiresolution analysis (MRA are presented in this work to measure vertical gravity wave characteristics. Wave properties are extracted from the first data set of Rayleigh lidar obtained between heights of 30 km and 60 km over La Reunion Island (21°S, 55°E during the Austral winter in 1994 under subtropical conditions. The altitude-wavelength representations deduced from these methods provide information on the time and spatial evolution of the wave parameters of the observed dominant modes in vertical profiles such as the vertical wavelengths, the vertical phase speeds, the amplitudes of temperature perturbations and the distribution of wave energy. The spectra derived from measurements show the presence of localized quasi-monochromatic structures with vertical wavelengths <10 km. Three methods based on the wavelet techniques show evidence of a downward phase progression. A first climatology of the dominant modes observed during the Austral winter period reveals a dominant night activity of 2 or 3 quasi-monochromatic structures with vertical wavelengths between 1-2 km from the stratopause, 3-4 km and 6-10 km observed between heights of 30 km and 60 km. In addition, it reveals a dominant activity of modes with a vertical phase speed of -0.3 m/s and observed periods peaking at 3-4 h and 9 h. The characteristics of averaged vertical wavelengths appear to be similar to those observed during winter in the southern equatorial region and in the Northern Hemisphere at mid-latitudes.

    Key words: Meteorology and atmospheric dynamics (climatology; middle atmosphere dynamics; waves and tides

  10. On the interaction of wind and steep gravity wave groups using Miles' and Jeffreys' mechanisms

    Directory of Open Access Journals (Sweden)

    J. Touboul

    2008-12-01

    Full Text Available The interaction of wind and water wave groups is investigated theoretically and numerically. A steep wave train is generated by means of dispersive focusing, using both the linear theory and fully nonlinear equations. The linear theory is based on the Schrödinger equation while the nonlinear approach is developed numerically within the framework of the potential theory. The interaction between the chirped wave packet and wind is described by the Miles' mechanism. The differences between both approaches are discussed, and the influence of nonlinearity is emphasized. Furthermore, a different mechanism is considered, described by the modified Jeffreys' sheltering theory. From comparison between the two mechanisms, it is found that the persistence of the steep wave group depends on the physical model used, and is significantly increased when we use the latter mechanism.

  11. Multi-instrument observations of gravity waves and other disturbances of the middle atmosphere in the framework of the ARISE project

    Science.gov (United States)

    Blanc, E.

    2017-12-01

    The ARISE project combines national and international observation networks including the International infrasound monitoring system developed for the CTBT (Comprehensive nuclear-Test-Ban Treaty) verification, the NDACC (Network for the Detection of Atmospheric Composition Changes) lidar network, European observation infrastructures at mid latitudes (OHP observatory), tropics (OPAR observatory), high latitudes (ALOMAR), the European infrasound stations and networks and satellites. The observation coverage extends from equatorial to Polar Regions and altitude ranges from ground to the lower thermosphere. The main objective is to recover the vertical structure of the middle atmospheric disturbances in broad space and time scales. This paper highlights recent results obtained to better characterize gravity waves and other disturbances such as sudden stratospheric warming events and applications related to weather and climate modelling.

  12. Techno-economic evaluation of hybrid energy storage technologies for a solar–wind generation system

    International Nuclear Information System (INIS)

    Ren, L.; Tang, Y.; Shi, J.; Dou, J.; Zhou, S.; Jin, T.

    2013-01-01

    Highlights: ► The techno-economic feasibility of four ESSs is studied. ► The hybrid ESS applied on a renewable energy generation system is feasible. ► From the technical and economic viewpoint, case 3 is the optimal hybrid ESS. -- Abstract: Huazhong University of Science and Technology is planning to establish a hybrid solar–wind generation dynamic simulation laboratory. Energy storage technologies will be vital to this system for load leveling, power quality control and stable output. In this paper, the technical feasibility of energy storage technologies for renewable intermittent sources like wind and solar generation is analyzed. Furthermore, the different combination modes of energy storage technologies are proposed. The involved energy storage technologies include superconducting magnetic energy storage systems (SMESs), flywheels (FWs), electrochemical super-capacitors (SCs) and redox flow batteries (RFBs). Based on that, the economic analysis of hybrid energy storage technologies is conducted

  13. Comparative study of a small size wind generation system efficiency for battery charging

    Directory of Open Access Journals (Sweden)

    Mayouf Messaoud

    2013-01-01

    Full Text Available This paper presents an energetic comparison between two control strategies of a small size wind generation system for battery charging. The output voltage of the direct drive PMSG is connected to the battery through a switch mode rectifier. A DC-DC boost converter is used to regulate the battery bank current in order to achieve maximum power from the wind. A maximum powertracking algorithm calculates the current command that corresponds to maximum power output of the turbine. The DC-DC converter uses this current to calculate the duty cycle witch is necessary to control the pulse width modulated (PWM active switching device (IGPT. The system overview and modeling are presented including characteristics of wind turbine, generator, batteries, power converter, control system, and supervisory system. A simulation of the system is performed using MATLAB/SIMULINK.

  14. Power Maximization Control of Variable Speed Wind Generation System Using Permanent Magnet Synchronous Generator

    Science.gov (United States)

    Morimoto, Shigeo; Nakamura, Tomohiko; Takeda, Yoji

    This paper proposes the sensorless output power maximization control of the wind generation system. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. The generator torque is suitably controlled according to the generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control method, where the information of wind velocity is not required. Moreover, the maximum available generated power is obtained by the optimum current vector control. The current vector of PMSG is optimally controlled according to the generator speed and the required torque in order to minimize the losses of PMSG considering the voltage and current constraints. The proposed wind power generation system can be achieved without mechanical sensors such as a wind velocity detector and a position sensor. Several experimental results show the effectiveness of the proposed control method.

  15. Analysis of gravity waves in the tropical middle atmosphere over La Reunion Island (21 deg S, 55 deg E) with lidar using wavelet techniques

    Science.gov (United States)

    Chane-Ming, F.; Molinaro, F.; Leveau, J.; Keckhut, P.; Hauchecorne, A.

    2000-04-01

    The capabilities of the continuous wavelet transform (CWT) and the multiresolution analysis (MRA) are presented in this work to measure vertical gravity wave characteristics. Wave properties are extracted from the first data set of Rayleigh lidar obtained between heights of 30 km and 60 km over La Reunion Island (21°S, 55°E) during the Austral winter in 1994 under subtropical conditions. The altitude-wavelength representations deduced from these methods provide information on the time and spatial evolution of the wave parameters of the observed dominant modes in vertical profiles such as the vertical wavelengths, the vertical phase speeds, the amplitudes of temperature perturbations and the distribution of wave energy. The spectra derived from measurements show the presence of localized quasi-monochromatic structures with vertical wavelengths <10 km. Three methods based on the wavelet techniques show evidence of a downward phase progression. A first climatology of the dominant modes observed during the Austral winter period reveals a dominant night activity of 2 or 3 quasi-monochromatic structures with vertical wavelengths between 1-2 km from the stratopause, 3-4 km and 6-10 km observed between heights of 30 km and 60 km. In addition, it reveals a dominant activity of modes with a vertical phase speed of -0.3 m/s and observed periods peaking at 3-4 h and 9 h. The characteristics of averaged vertical wavelengths appear to be similar to those observed during winter in the southern equatorial region and in the Northern Hemisphere at mid-latitudes.

  16. Massive Gravity

    Directory of Open Access Journals (Sweden)

    Claudia de Rham

    2014-08-01

    Full Text Available We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP, cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware–Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alternative and related models of massive gravity such as new massive gravity, Lorentz-violating massive gravity and non-local massive gravity.

  17. Empirical Analysis of the Variability of Wind Generation in India: Implications for Grid Integration

    Energy Technology Data Exchange (ETDEWEB)

    Phadke, Amol; Abhyankar, NIkit; Rao, Poorvi

    2014-06-17

    We analyze variability in load and wind generation in India to assess its implications for grid integration of large scale wind projects using actual wind generation and load data from two states in India, Karnataka and Tamil Nadu. We compare the largest variations in load and net load (load ?wind, i.e., load after integrating wind) that the generation fleet has to meet. In Tamil Nadu, where wind capacity is about 53percent of the peak demand, we find that the additional variation added due to wind over the current variation in load is modest; if wind penetration reaches 15percent and 30percent by energy, the additional hourly variation is less than 0.5percent and 4.5percent of the peak demand respectively for 99percent of the time. For wind penetration of 15percent by energy, Tamil Nadu system is found to be capable of meeting the additional ramping requirement for 98.8percent of the time. Potential higher uncertainty in net load compared to load is found to have limited impact on ramping capability requirements of the system if coal plants can me ramped down to 50percent of their capacity. Load and wind aggregation in Tamil Nadu and Karnataka is found to lower the variation by at least 20percent indicating the benefits geographic diversification. These findings suggest modest additional flexible capacity requirements and costs for absorbing variation in wind power and indicate that the potential capacity support (if wind does not generate enough during peak periods) may be the issue that has more bearing on the economics of integrating wind

  18. The Future of Gravity

    CERN Multimedia

    CERN. Geneva

    2007-01-01

    Of the four fundamental forces, gravity has been studied the longest, yet gravitational physics is one of the most rapidly developing areas of science today. This talk will give a broad brush survey of the past achievements and future prospects of general relativistic gravitational physics. Gravity is a two frontier science being important on both the very largest and smallest length scales considered in contemporary physics. Recent advances and future prospects will be surveyed in precision tests of general relativity, gravitational waves, black holes, cosmology and quantum gravity. The aim will be an overview of a subject that is becoming increasingly integrated with experiment and other branches of physics.

  19. Quantum Gravity Experiments

    Directory of Open Access Journals (Sweden)

    Cahill R. T.

    2015-10-01

    Full Text Available A new quantum gravity experiment is reported with the data confirming the generali- sation of the Schrödinger equation to include the interaction of the wave function with dynamical space. Dynamical space turbulence, via this interaction process, raises and lowers the energy of the electron wave function, which is detected by observing conse- quent variations in the electron quantum barrier tunnelling rate in reverse-biased Zener diodes. This process has previously been reported and enabled the measurement of the speed of the dynamical space flow, which is consistent with numerous other detection experiments. The interaction process is dependent on the angle between the dynamical space flow velocity and the direction of the electron flow in the diode, and this depen- dence is experimentally demonstrated. This interaction process explains gravity as an emergent quantum process, so unifying quantum phenomena and gravity. Gravitational waves are easily detected.

  20. Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

    Directory of Open Access Journals (Sweden)

    C. J. Wright

    2017-07-01

    Full Text Available Gravity waves (GWs transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for developing the next generation of weather forecasting and climate prediction models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60° S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully 3-D method for detecting and characterising GWs in the stratosphere. This method is based around a 3-D Stockwell transform, and can be applied retrospectively to existing observed data. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3-D atmospheric temperature data from AIRS/Aqua over the altitude range 20–60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes (MFs, and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this method over the region around the Southern Andes and Antarctic Peninsula, the largest known sources of GW MFs near the 60° S belt. Our analyses reveal the presence of strongly intermittent highly directionally focused GWs with very high momentum fluxes (∼ 80–100 mPa or more at 30 km altitude. These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity

  1. Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

    Science.gov (United States)

    Wright, Corwin J.; Hindley, Neil P.; Hoffmann, Lars; Alexander, M. Joan; Mitchell, Nicholas J.

    2017-07-01

    Gravity waves (GWs) transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for developing the next generation of weather forecasting and climate prediction models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60° S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully 3-D method for detecting and characterising GWs in the stratosphere. This method is based around a 3-D Stockwell transform, and can be applied retrospectively to existing observed data. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3-D atmospheric temperature data from AIRS/Aqua over the altitude range 20-60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes (MFs), and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this method over the region around the Southern Andes and Antarctic Peninsula, the largest known sources of GW MFs near the 60° S belt. Our analyses reveal the presence of strongly intermittent highly directionally focused GWs with very high momentum fluxes (˜ 80-100 mPa or more at 30 km altitude). These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity vectors show clear observational

  2. On the spatial linear growth of gravity-capillary water waves sheared by a laminar air flow

    NARCIS (Netherlands)

    Tsai, Y.S.; Grass, A.J.; Simons, R.R.

    2005-01-01

    The initial growth of mechanically generated small amplitude water waves below a laminar air stream was examined numerically and experimentally in order to explore the primary growth mechanism, that is, the interfacial instability of coupled laminar air and water flows. Measurements of the laminar

  3. Gravitational waves during inflation in presence of a decaying cosmological parameter from a 5D vacuum theory of gravity

    International Nuclear Information System (INIS)

    Gomez Martinez, Silvina Paola; Madriz Aguilar, Jose Edgar; Bellini, Mauricio

    2007-01-01

    We study gravitational waves generated during the inflationary epoch in presence of a decaying cosmological parameter on a 5D geometrical background which is Riemann flat. Two examples are considered, one with a constant cosmological parameter and the second with a decreasing one

  4. Experimental investigation of effect of surface gravity waves and spray on heat and momentum flux at strong wind conditions

    Science.gov (United States)

    Troitskaya, Yuliya; Sergeev, Daniil; Vdovin, Maxim; Kandaurov, Alexander; Ermakova, Olga; Kazakov, Vassily

    2015-04-01

    The most important characteristics that determine the interaction between atmosphere and ocean are fluxes of momentum, heat and moisture. For their parameterization the dimensionless exchange coefficients (the surface drag coefficient CD and the heat transfer coefficient or the Stanton number CT) are used. Numerous field and laboratory experiments show that CD increases with increasing wind speed at moderate and strong wind, and as it was shows recently CD decreases at hurricane wind speed. Waves are known to increase the sea surface resistance due to enhanced form drag, the sea spray is considered as a possible mechanism of the 'drag reduction' at hurricane conditions. The dependence of heat transfer coefficient CD on the wind speed is not so certain and the role of the mechanism associated with the wave disturbances in the mass transfer is not completely understood. Observations and laboratory data show that this dependence is weaker than for the CD, and there are differences in the character of the dependence in different data sets. The purpose of this paper is investigation of the effect of surface waves on the turbulent exchange of momentum and heat within the laboratory experiment, when wind and wave parameters are maintained and controlled. The effect of spray on turbulent exchange at strong winds is also estimated. A series of experiments to study the processes of turbulent exchange of momentum and heat in a stably stratified temperature turbulent boundary layer air flow over waved water surface were carried out at the Wind - wave stratified flume of IAP RAS, the peculiarity of this experiment was the option to change the surface wave parameters regardless of the speed of the wind flow in the channel. For this purpose a polyethylene net with the variable depth (0.25 mm thick and a cell of 1.6 mm × 1.6mm) has been stretched along the channel. The waves were absent when the net was located at the level of the undisturbed water surface, and had maximum

  5. Incipient Stator Insulation Fault Detection of Permanent Magnet Synchronous Wind Generators Based on Hilbert–Huang Transformation

    DEFF Research Database (Denmark)

    Wang, Chao; Liu, Xiao; Chen, Zhe

    2014-01-01

    Incipient stator winding fault in permanent magnet synchronous wind generators (PMSWGs) is very difficult to be detected as the fault generated variations in terminal electrical parameters are very weak and chaotic. This paper simulates the incipient stator winding faults at different degree...

  6. A Control Approach and Supplementary Controllers for a Stand-Alone System with Predominance of Wind Generation

    Directory of Open Access Journals (Sweden)

    Tiago Lukasievicz

    2018-02-01

    Full Text Available This paper proposes a control approach and supplementary controllers for the operation of a hybrid stand-alone system composed of a wind generation unit and a conventional generation unit based on synchronous generator (CGU. The proposed controllers allow the islanded or isolated operation of small power systems with predominance of wind generation. As an advantage and a paradigm shift, the DC-link voltage of the wind unit is controlled by means of a conventional synchronous generator connected to the AC grid of the system. Two supplementary controllers, added to a diesel generator (DIG and to a DC dump load (DL, are proposed to control the DC-link voltage. The wind generation unit operates in V-f control mode and the DIG operates in PQ control mode, which allows the stand-alone system to operate either in wind-diesel (WD mode or in wind-only (WO mode. The strong influence of the wind turbine speed variations in the DC-link voltage is mitigated by a low-pass filter added to the speed control loop of the wind turbine. The proposed control approach does not require the use battery bank and ultra-capacitor to control the DC-link voltage in wind generation units based on fully rated converter.

  7. Effects of voltage unbalance and system harmonics on the performance of doubly fed induction wind generators

    Science.gov (United States)

    Kiani, Morgan Mozhgan

    Inherent difficulties in management of electric power in the presence of an increasing demand for more energy, non-conventional loads such as digital appliances, and non-sustainable imported fossil fuels has initiated a multi-folded effort by many countries to restructure the way electric energy is generated, dispatched, and consumed. Smart power grid is the manifestation of many technologies that would eventually transforms the existing power grid into a more flexible, fault resilient, and intelligent system. Integration of distributed renewable energy sources plays a central role in successful implementation of this transformation. Among the renewable options, wind energy harvesting offers superior engineering and economical incentives with minimal environmental impacts. Doubly fed induction generators (DFIG) have turned into a serious contender for wind energy generators due to their flexibility in control of active and reactive power with minimal silicon loss. Significant presence of voltage unbalance and system harmonics in finite inertia transmission lines can potentially undermine the reliability of these wind generators. The present dissertation has investigated the impacts of system unbalances and harmonics on the performance of the DFIG. Our investigation indicates that these effects can result in an undesirable undulation in the rotor shaft which can potentially invoke mechanical resonance, thereby causing catastrophic damages to the installations and the power grid. In order to remedy the above issue, a control solution for real time monitoring of the system unbalance and optimal excitation of the three phase rotor currents in a DFIG is offered. The optimal rotor currents will create appropriate components of the magneto-motive force in the airgap that will actively compensate the undesirable magnetic field originated by the stator windings. Due to the iterative nature of the optimization procedure, field reconstruction method has been incorporated

  8. Constraining Nonperturbative Strong-Field Effects in Scalar-Tensor Gravity by Combining Pulsar Timing and Laser-Interferometer Gravitational-Wave Detectors

    Directory of Open Access Journals (Sweden)

    Lijing Shao

    2017-10-01

    Full Text Available Pulsar timing and laser-interferometer gravitational-wave (GW detectors are superb laboratories to study gravity theories in the strong-field regime. Here, we combine these tools to test the mono-scalar-tensor theory of Damour and Esposito-Farèse (DEF, which predicts nonperturbative scalarization phenomena for neutron stars (NSs. First, applying Markov-chain Monte Carlo techniques, we use the absence of dipolar radiation in the pulsar-timing observations of five binary systems composed of a NS and a white dwarf, and eleven equations of state (EOSs for NSs, to derive the most stringent constraints on the two free parameters of the DEF scalar-tensor theory. Since the binary-pulsar bounds depend on the NS mass and the EOS, we find that current pulsar-timing observations leave scalarization windows, i.e., regions of parameter space where scalarization can still be prominent. Then, we investigate if these scalarization windows could be closed and if pulsar-timing constraints could be improved by laser-interferometer GW detectors, when spontaneous (or dynamical scalarization sets in during the early (or late stages of a binary NS (BNS evolution. For the early inspiral of a BNS carrying constant scalar charge, we employ a Fisher-matrix analysis to show that Advanced LIGO can improve pulsar-timing constraints for some EOSs, and next-generation detectors, such as the Cosmic Explorer and Einstein Telescope, will be able to improve those bounds for all eleven EOSs. Using the late inspiral of a BNS, we estimate that for some of the EOSs under consideration, the onset of dynamical scalarization can happen early enough to improve the constraints on the DEF parameters obtained by combining the five binary pulsars. Thus, in the near future, the complementarity of pulsar timing and direct observations of GWs on the ground will be extremely valuable in probing gravity theories in the strong-field regime.

  9. Characteristics of sprite and gravity wave convective sources present in satellite IR images during the SpreadFEx 2005 in Brazil

    Energy Technology Data Exchange (ETDEWEB)

    Sao Sabbas, F.T.; Ramppinelli, V.T.; Santiago, J.; Stamus, P.; Pinto, O. [National Insitute for Space Research-INPE, Sao Jose dos Campos, Sao Paulo (Brazil); Vadas, S.L.; Fritts, D.C. [Northwest Research Associates, CoRA Division, Boulder, CO (United States); Taylor, M.J.; Pautet, P.D. [Utah State University, Logan, Utah (United States); Dolif Neto, G. [Center of Weather Forecast and Climate Studies/INPE, Cachoeira Paulista, Sao Paulo (Brazil)

    2009-07-01

    We developed a technique to identify and estimate the size, intensity, and Tropopause overshoot of thunderstorm convective cores expected to be significant sources of gravity waves. The work was based on GOES IR images of South America on the night of 30 September to 1 October and 25-26 October 2005, as part of the Spread F Experiment (SpreadFEx) in Brazil in 2005. We also characterized, for the first time, the convective activity of three small TLE producing thunderstorms that yielded 11 TLEs on 25-26 October 2005. The campaign occurred during the dry to wet season transition in central Brazil, marked by the presence of extra-tropical cyclogenesis over the Atlantic Ocean, and cold fronts penetrating inland. The Tropopause temperature was typically -76 C with a corresponding altitude of {proportional_to}15200 m. Vigorous convective cores capable of generating strong gravity waves were located in convective regions having areas with cloud top temperatures {<=}-76 C. They had typical cloud-top temperature deficits of {delta}T-2.0 C to -8.0 C from the average surroundings, implying overshoot heights of 200 to 3100 m, which are within the typical range. Fast vertical development and high horizontal growth rates were associated with a large number of simultaneously active vigorous convective cores, indicating that their dynamics may have determined the spatial-temporal development of the thunderstorms analyzed. Moderate convective cores were also present in areas with cloud top -76 C{<=}T{<=}-70 C. They had {delta}T of -1.9 C to -5.3 C producing overshoots between 80-300 m. All convective cores had typical diameters of 5-20 km and their size tended to increase with {delta}T, there was a 57% correlation between the two parameters. Analysis of the relationship of cloud top T with positive and negative cloud-to-ground lightning ({+-}CG) occurrence rate and with peak current showed that lighting activity may provide an independent way to identify convective cores and

  10. High waves in Draupner seas — Part 1 : numerical simulations and characterization of the seas

    NARCIS (Netherlands)

    van Groesen, E.; Turnip, P.; Kurnia, R.

    2017-01-01

    Extreme waves are studied in numerical simulations of the so-called Draupner seas that resemble the wave situation near the observation area of the Draupner wave, an iconic example of a freak, rogue wave. Recent new meteorological insights describe these seas as a substantial wind-generated wave

  11. Model of analysis of maximum loads in wind generators produced by extreme winds

    International Nuclear Information System (INIS)

    Herrera – Sánchez, Omar; Schellong, Wolfgang; González – Fernández, Vladimir

    2010-01-01

    The use of the wind energy by means of the wind turbines in areas of high risk of occurrence of Hurricanes comes being an important challenge for the designers of wind farm at world for some years. The wind generator is not usually designed to support this type of phenomena, for this reason the areas of high incidence of tropical hurricanes of the planning are excluded, that which, in occasions disables the use of this renewable source of energy totally, either because the country is very small, or because it coincides the area of more potential fully with that of high risk. To counteract this situation, a model of analysis of maxims loads has been elaborated taken place the extreme winds in wind turbines of great behavior. This model has the advantage of determining, in a chosen place, for the installation of a wind farm, the micro-areas with higher risk of wind loads above the acceptable for the standard classes of wind turbines. (author)

  12. Smart pitch control strategy for wind generation system using doubly fed induction generator

    Science.gov (United States)

    Raza, Syed Ahmed

    A smart pitch control strategy for a variable speed doubly fed wind generation system is presented in this thesis. A complete dynamic model of DFIG system is developed. The model consists of the generator, wind turbine, aerodynamic and the converter system. The strategy proposed includes the use of adaptive neural network to generate optimized controller gains for pitch control. This involves the generation of controller parameters of pitch controller making use of differential evolution intelligent technique. Training of the back propagation neural network has been carried out for the development of an adaptive neural network. This tunes the weights of the network according to the system states in a variable wind speed environment. Four cases have been taken to test the pitch controller which includes step and sinusoidal changes in wind speeds. The step change is composed of both step up and step down changes in wind speeds. The last case makes use of scaled wind data collected from the wind turbine installed at King Fahd University beach front. Simulation studies show that the differential evolution based adaptive neural network is capable of generating the appropriate control to deliver the maximum possible aerodynamic power available from wind to the generator in an efficient manner by minimizing the transients.

  13. Analysis And Synthesis Of Model Reference Controller For Variable Speed Wind Generators Inertial Support

    Science.gov (United States)

    Bećirović, Elvisa; Osmić, Jakub; Kušljugić, Mirza; Perić, Nedjeljko

    2015-01-01

    Model Reference Controller (MRC) for contribution of Variable Speed Wind Generators (VSWG) in inertial response of Electrical Power System (EPS) is presented and analyzed in this paper. MRC is synthesized based on a model of Generating Unit With non-Reheat Steam Turbine (GUNRST) thus enabling VSWG to emulate GUNRST response during the initial stage of dynamic frequency response ie inertial phase. Very important property of conventional steam generating units is that its contribution to inertial phase response is independent from the initial generating power. By using MRC in VSWG it is accomplished that in most common wind speed region (3-12 m/s) VSWG inertial support is almost independent from wind speed. Since in most EPSs VSWG replaces conventional steam generators, application of MRC algorithm provides that the characteristics of EPS in terms of inertial response are preserved, regardless of the growing trend of introducing VSWG. Evaluation analysis of the proposed MRC is performed on modified nine bus power system when VSWG with MRC is connected to one of the power system buses.

  14. Model simulations of line-of-sight effects in airglow imaging of acoustic and fast gravity waves from ground and space

    Science.gov (United States)

    Aguilar Guerrero, J.; Snively, J. B.

    2017-12-01

    Acoustic waves (AWs) have been predicted to be detectable by imaging systems for the OH airglow layer [Snively, GRL, 40, 2013], and have been identified in spectrometer data [Pilger et al., JASP, 104, 2013]. AWs are weak in the mesopause region, but can attain large amplitudes in the F region [Garcia et al., GRL, 40, 2013] and have local impacts on the thermosphere and ionosphere. Similarly, fast GWs, with phase speeds over 100 m/s, may propagate to the thermosphere and impart significant local body forcing [Vadas and Fritts, JASTP, 66, 2004]. Both have been clearly identified in ionospheric total electron content (TEC), such as following the 2013 Moore, OK, EF5 tornado [Nishioka et al., GRL, 40, 2013] and following the 2011 Tohoku-Oki tsunami [e.g., Galvan et al., RS, 47, 2012, and references therein], but AWs have yet to be unambiguously imaged in MLT data and fast GWs have low amplitudes near the threshold of detection; nevertheless, recent imaging systems have sufficient spatial and temporal resolution and sensitivity to detect both AWs and fast GWs with short periods [e.g., Pautet et al., AO, 53, 2014]. The associated detectability challenges are related to the transient nature of their signatures and to systematic challenges due to line-of-sight (LOS) effects such as enhancements and cancelations due to integration along aligned or oblique wavefronts and geometric intensity enhancements. We employ a simulated airglow imager framework that incorporates 2D and 3D emission rate data and performs the necessary LOS integrations for synthetic imaging from ground- and space-based platforms to assess relative intensity and temperature perturbations. We simulate acoustic and fast gravity wave perturbations to the hydroxyl layer from a nonlinear, compressible model [e.g., Snively, 2013] for different idealized and realistic test cases. The results show clear signal enhancements when acoustic waves are imaged off-zenith or off-nadir and the temporal evolution of these

  15. Convection: the likely source of the medium-scale gravity waves observed in the OH airglow layer near Brasilia, Brazil, during the SpreadFEx campaign

    Directory of Open Access Journals (Sweden)

    S. L. Vadas

    2009-01-01

    Full Text Available Six medium-scale gravity waves (GWs with horizontal wavelengths of λH=60–160 km were detected on four nights by Taylor et al. (2009 in the OH airglow layer near Brasilia, at 15° S, 47° W, during the Spread F Experiment (SpreadFEx in Brazil in 2005. We reverse and forward ray trace these GWs to the tropopause and into the thermosphere using a ray trace model which includes thermospheric dissipation. We identify the convective plumes, convective clusters, and convective regions which may have generated these GWs. We find that deep convection is the highly likely source of four of these GWs. We pinpoint the specific deep convective plumes which likely excited two of these GWs on the nights of 30 September and 1 October. On these nights, the source location/time uncertainties were small and deep convection was sporadic near the modeled source locations. We locate the regions containing deep convective plumes and clusters which likely excited the other two GWs. The last 2 GWs were probably also excited from deep convection; however, they must have been ducted ~500–700 km if so. Two of the GWs were likely downwards-propagating initially (after which they reflected upwards from the Earth's surface, while one of the GWs was likely upwards-propagating initially from the convective plume/cluster. We also estimate the amplitudes and vertical scales of these waves at the tropopause, and compare their scales with those from a simple, linear convection model. Finally, we calculate each GW's dissipation altitude, location, and amplitude. We find that the dissipation altitude depends sensitively on the winds at and above the OH layer. We also find that several of these GWs may have penetrated to high enough altitudes to potentially seed equatorial spread F (ESF if located somewhat farther from the magnetic equator.

  16. Relationship between propagation direction of gravity waves in OH and OI airglow images and VHF radar echo occurrence during the SEEK-2 campaign

    Directory of Open Access Journals (Sweden)

    F. Onoma

    2005-10-01

    Full Text Available We report simultaneous observations of atmospheric gravity waves (AGW in OI (557.7nm and OH airglow images and VHF radar backscatter from field-aligned irregularities (FAI in the E-region during the SEEK-2 (Sporadic-E Experiment over Kyushu 2 campaign period from 29 July to 9 August 2002. An all-sky imager was operated at Nishino-Omote (30.5 N, 130.1 E, Japan. On 14 nights, 17 AGW events were detected in OI and OH airglow images. AGW propagated mostly toward the northeast or southeast. From comparison with the E-region FAI occurrence, which is detected by a nearby VHF radar (31.57MHz, we found that AGW tended to propagate southeastward during FAI events. This result suggests that the interaction between AGW and E-region plasma plays an important role in generating FAI. Furthermore, polarization electric fields generated directly by AGW may contribute to the FAI generation.

    Keywords. Atmospheric composition and structure (Airglow and aurora, Ionosphere (Ionospheric irregularities, Mid-latitude ionosphere

  17. Observation of TEC perturbation associated with medium-scale traveling ionospheric disturbance and possible seeding mechanism of atmospheric gravity wave at a Brazilian sector

    Science.gov (United States)

    Jonah, O. F.; Kherani, E. A.; De Paula, E. R.

    2016-03-01

    In the present study, we document daytime total electron content (TEC) disturbances associated with medium-scale traveling ionospheric disturbances (MSTIDs), on few chosen geomagnetically quiet days over Southern Hemisphere of Brazilian longitude sector. These disturbances are derived from TEC data obtained using Global Navigation Satellite System (GNSS) receiver networks. From the keograms and cross-correlation maps, the TEC disturbances are identified as the MSTIDs that are propagating equatorward-eastward, having most of their average wavelengths longer in latitude than in longitude direction. These are the important outcomes of the present study which suggest that the daytime MSTIDs over Southern Hemisphere are similar to their counterparts in the Northern Hemisphere. Another important outcome is that the occurrence characteristics of these MSTIDs and that of atmospheric gravity wave (AGW) activities in the thermosphere are found to be similar on day-to-day basis. This suggests a possible connection between them, confirming the widely accepted AGW forcing mechanism for the generation of these daytime MSTIDs. The source of this AGW is investigated using the Geostationary Operational Environmental Satellite system (GOES) and Constellation Observing System for Meteorology, Ionosphere, and Climate satellite data. Finally, we provided evidences that AGWs are generated by convection activities from the tropospheric region.

  18. Massive Gravity

    OpenAIRE

    de Rham, Claudia

    2014-01-01

    We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware–Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...

  19. Second- and third-order moment budgets in a turbulent patch resulting from internal gravity wave breaking

    International Nuclear Information System (INIS)

    Yakovenko, S N

    2011-01-01

    To study second- and third-order statistical moments in a quasi-steady turbulent region observed in stratified flows over obstacles after the wave breaking, the direct simulation method developed for variable density fields is used. The data of runs at Re = 4000, F h = 0.6 (based on obstacle height and inflow velocity) are used to obtain time dependence and spatial distributions of Reynolds stress tensor components, turbulent kinetic energy, scalar variance, triple correlations, and terms of budgets of their transport equations. The analysis shows that the global balance for both scalar variance and turbulent kinetic energy is between mean-shear production, advection and dissipation, whereas locally buoyant production and turbulent transport due to third-order moments are significant. For normal Reynolds stresses, the pressure-strain term is important too, providing the redistribution of stress components. The studies allow us not only to explore the turbulent patch by means of statistical moments, but also to examine closure assumptions for separate items and evaluate geophysically interesting quantities produced from the averaged data.

  20. Impact of a simple parameterization of convective gravity-wave drag in a stratosphere-troposphere general circulation model and its sensitivity to vertical resolution

    Directory of Open Access Journals (Sweden)

    C. Bossuet

    1998-02-01

    Full Text Available Systematic westerly biases in the southern hemisphere wintertime flow and easterly equatorial biases are experienced in the Météo-France climate model. These biases are found to be much reduced when a simple parameterization is introduced to take into account the vertical momentum transfer through the gravity waves excited by deep convection. These waves are quasi-stationary in the frame of reference moving with convection and they propagate vertically to higher levels in the atmosphere, where they may exert a significant deceleration of the mean flow at levels where dissipation occurs. Sixty-day experiments have been performed from a multiyear simulation with the standard 31 levels for a summer and a winter month, and with a T42 horizontal resolution. The impact of this parameterization on the integration of the model is found to be generally positive, with a significant deceleration in the westerly stratospheric jet and with a reduction of the easterly equatorial bias. The sensitivity of the Météo-France climate model to vertical resolution is also investigated by increasing the number of vertical levels, without moving the top of the model. The vertical resolution is increased up to 41 levels, using two kinds of level distribution. For the first, the increase in vertical resolution concerns especially the troposphere (with 22 levels in the troposphere, and the second treats the whole atmosphere in a homogeneous way (with 15 levels in the troposphere; the standard version of 31 levels has 10 levels in the troposphere. A comparison is made between the dynamical aspects of the simulations. The zonal wind and precipitation are presented and compared for each resolution. A positive impact is found with the finer tropospheric resolution on the precipitation in the mid-latitudes and on the westerly stratospheric jet, but the general impact on the model climate is weak, the physical parameterizations used appear to be mostly independent to the

  1. Impact of a simple parameterization of convective gravity-wave drag in a stratosphere-troposphere general circulation model and its sensitivity to vertical resolution

    Directory of Open Access Journals (Sweden)

    C. Bossuet

    Full Text Available Systematic westerly biases in the southern hemisphere wintertime flow and easterly equatorial biases are experienced in the Météo-France climate model. These biases are found to be much reduced when a simple parameterization is introduced to take into account the vertical momentum transfer through the gravity waves excited by deep convection. These waves are quasi-stationary in the frame of reference moving with convection and they propagate vertically to higher levels in the atmosphere, where they may exert a significant deceleration of the mean flow at levels where dissipation occurs. Sixty-day experiments have been performed from a multiyear simulation with the standard 31 levels for a summer and a winter month, and with a T42 horizontal resolution. The impact of this parameterization on the integration of the model is found to be generally positive, with a significant deceleration in the westerly stratospheric jet and with a reduction of the easterly equatorial bias. The sensitivity of the Météo-France climate model to vertical resolution is also investigated by increasing the number of vertical levels, without moving the top of the model. The vertical resolution is increased up to 41 levels, using two kinds of level distribution. For the first, the increase in vertical resolution concerns especially the troposphere (with 22 levels in the troposphere, and the second treats the whole atmosphere in a homogeneous way (with 15 levels in the troposphere; the standard version of 31 levels has 10 levels in the troposphere. A comparison is made between the dynamical aspects of the simulations. The zonal wind and precipitation are presented and compared for each resolution. A positive impact is found with the finer tropospheric resolution on the precipitation in the mid-latitudes and on the westerly stratospheric jet, but the general impact on the model climate is weak, the physical parameterizations used appear to be mostly independent to the

  2. Gravitational Waves

    Energy Technology Data Exchange (ETDEWEB)

    Miller, Jonah Maxwell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-18

    This report has slides on Gravitational Waves; Pound and Rebka: A Shocking Fact; Light is a Ruler; Gravity is the Curvature of Spacetime; Gravitational Waves Made Simple; How a Gravitational Wave Affects Stuff Here; LIGO; This Detection: Neutron Stars; What the Gravitational Wave Looks Like; The Sound of Merging Neutron Stars; Neutron Star Mergers: More than GWs; The Radioactive Cloud; The Kilonova; and finally Summary, Multimessenger Astronomy.

  3. Options to Improve the Quality of Wind Generation Output Forecasting with the Use of Available Information as Explanatory Variables

    Directory of Open Access Journals (Sweden)

    Rafał Magulski

    2015-06-01

    Full Text Available Development of wind generation, besides its positive aspects related to the use of renewable energy, is a challenge from the point of view of power systems’ operational security and economy. The uncertain and variable nature of wind generation sources entails the need for the for the TSO to provide adequate reserves of power, necessary to maintain the grid’s stable operation, and the actors involved in the trading of energy from these sources incur additional of balancing unplanned output deviations. The paper presents the results of analyses concerning the options to forecast a selected wind farm’s output exercised by means of different methods of prediction, using a different range of measurement and forecasting data available on the farm and its surroundings. The analyses focused on the evaluation of forecast errors, and selection of input data for forecasting models and assessment of their impact on prediction quality improvement.

  4. Effect of wind generation system types on Micro-Grid (MG) fault performance during both standalone and grid connected modes

    International Nuclear Information System (INIS)

    Kamel, Rashad M.

    2014-01-01

    Highlights: • This paper evaluated the effects of different wind system types on fault performance of Micro-Grid. • Both standalone and grid connected modes are considered. • The MG earthing system configuration is taken in consideration. - Abstract: Recently, there are three wind generation (WG) system types. The first type is called Fixed Speed Wind Generation (FSWG) system, which employs squirrel cage induction generators. Double Fed Induction Generator (DFIG) is utilized in the second type. The third type is called Full Converter Wind Generation (FCWG) system, which is interfaced with Micro-Grid (MG) through a back to back converter. During fault occurrence, each WG has its performance and characteristics which are determined by the generator physical characteristics and the MG earthing system configuration. For some WG types, the fault current depends also on the control algorithm of the power converter. The main target of this paper is to investigate and estimate how the fault performance of MG during both standalone and grid-connected modes is influenced by the type of WG. It is found during standalone mode that the type of the employed WG has a dominant impact on the MG performance under fault disturbance. On the contrary, the type of the employed WG has a negligible effect on the MG fault performance during grid-connected mode. This is because the main grid contributes most of the fault current. Effects of earthing system type on MG performance are highlighted

  5. Multi-year observations of gravity wave momentum fluxes at low and middle latitudes inferred by all-sky meteor radar

    Science.gov (United States)

    Andrioli, V. F.; Batista, P. P.; Clemesha, B. R.; Schuch, N. J.; Buriti, R. A.

    2015-09-01

    We have applied a modified composite day analysis to the Hocking (2005) technique to study gravity wave (GW) momentum fluxes in the mesosphere and lower thermosphere (MLT). Wind measurements from almost continuous meteor radar observations during June 2004-December 2008 over São João do Cariri (Cariri; 7° S, 36° W), April 1999-November 2008 over Cachoeira Paulista (CP; 23° S, 45° W), and February 2005-December 2009 over Santa Maria (SM; 30° S, 54° W) were used to estimate the GW momentum fluxes and variances in the MLT region. Our analysis can provide monthly mean altitude profiles of vertical fluxes of horizontal momentum for short-period (less than 2-3 h) GWs. The averages for each month throughout the entire data series have shown different behavior for the momentum fluxes depending on latitude and component. The meridional component has almost the same behavior at the three sites, being positive (northward), for most part of the year. On the other hand, the zonal component shows different behavior at each location: it is positive for almost half the year at Cariri and SM but predominantly negative over CP. Annual variation in the GW momentum fluxes is present at all sites in the zonal component and also in SM at 89 km in the meridional component. The seasonal analysis has also shown a 4-month oscillation at 92.5 km over SM in the zonal component and over CP at the same altitudes but for the meridional component.

  6. Properties of inertia-gravity waves in the lowermost stratosphere as observed by the PANSY radar over Syowa Station in the Antarctic

    Directory of Open Access Journals (Sweden)

    M. Mihalikova

    2016-05-01

    Full Text Available Inertia-gravity waves (IGWs are an important component for the dynamics of the middle atmosphere. However, observational studies needed to constrain their forcing are still insufficient especially in the remote areas of the Antarctic region. One year of observational data (January to December 2013 by the PANSY radar of the wind components (vertical resolution of 150 m and temporal resolution of 30 min are used to derive statistical analysis of the properties of IGWs with short vertical wavelengths ( ≤ 4 km and ground-based periods longer than 4 h in the lowermost stratosphere (height range 10 to 12 km with the help of the hodograph method. The annual change of the IGWs parameters are inspected but no pronounced year cycle is found. The year is divided into two seasons (summer and winter based on the most prominent difference in the ratio of Coriolis parameter (f to intrinsic frequency (ω^ distribution. Average of f∕ω^  for the winter season is 0.40 and for the summer season 0.45 and the average horizontal wavelengths are 140 and 160 km respectively. Vertical wavelengths have an average of 1.85 km through the year. For both seasons the properties of IGWs with upward and downward propagation of the energy are also derived and compared. The percentage of downward propagating waves is 10.7 and 18.4 % in the summer and winter season respectively. This seasonal change is more than the one previously reported in the studies from mid-latitudes and model-based studies. It is in agreement with the findings of past radiosonde data-based studies from the Antarctic region. In addition, using the so-called dual-beam technique, vertical momentum flux and the variance of the horizontal perturbation velocities of IGWs are examined. Tropospheric disturbances of synoptic-scale are suggested as a source of episodes of IGWs with large variance of horizontal perturbation velocities, and this is shown in a number of cases.

  7. Kepler sheds new and unprecedented light on the variability of a blue supergiant: Gravity waves in the O9.5Iab star HD 188209

    Science.gov (United States)

    Aerts, C.; Símon-Díaz, S.; Bloemen, S.; Debosscher, J.; Pápics, P. I.; Bryson, S.; Still, M.; Moravveji, E.; Williamson, M. H.; Grundahl, F.; Fredslund Andersen, M.; Antoci, V.; Pallé, P. L.; Christensen-Dalsgaard, J.; Rogers, T. M.

    2017-06-01

    Stellar evolution models are most uncertain for evolved massive stars. Asteroseismology based on high-precision uninterrupted space photometry has become a new way to test the outcome of stellar evolution theory and was recently applied to a multitude of stars, but not yet to massive evolved supergiants.Our aim is to detect, analyse and interpret the photospheric and wind variability of the O9.5 Iab star HD 188209 from Kepler space photometry and long-term high-resolution spectroscopy. We used Kepler scattered-light photometry obtained by the nominal mission during 1460 d to deduce the photometric variability of this O-type supergiant. In addition, we assembled and analysed high-resolution high signal-to-noise spectroscopy taken with four spectrographs during some 1800 d to interpret the temporal spectroscopic variability of the star. The variability of this blue supergiant derived from the scattered-light space photometry is in full in agreement with the one found in the ground-based spectroscopy. We find significant low-frequency variability that is consistently detected in all spectral lines of HD 188209. The photospheric variability propagates into the wind, where it has similar frequencies but slightly higher amplitudes. The morphology of the frequency spectra derived from the long-term photometry and spectroscopy points towards a spectrum of travelling waves with frequency values in the range expected for an evolved O-type star. Convectively-driven internal gravity waves excited in the stellar interior offer the most plausible explanation of the detected variability. Based on photometric observations made with the NASA Kepler satellite and on spectroscopic observations made with four telescopes: the Nordic Optical Telescope operated by NOTSA and the Mercator Telescope operated by the Flemish Community, both at the Observatorio del Roque de los Muchachos (La Palma, Spain) of the Instituto de Astrofísica de Canarias, the T13 2.0 m Automatic Spectroscopic

  8. Observations of magnetic field and TEC fluctuations caused by ionospheric responses to acoustic and gravity waves from ground-level, natural hazard sources

    Science.gov (United States)

    Inchin, P.; Zettergren, M. D.; Snively, J. B.; Komjathy, A.; Verkhoglyadova, O. P.

    2017-12-01

    Recent studies have reported magnetic field fluctuations following intense seismic hazard events [e.g. Aoyama et al., EPS, 68, 2016; Toh et al., JGR, 116, 2011]. These perturbations can be associated with ionospheric dynamo phenomena driven by seismically generated acoustic and gravity waves (AGWs). AGW-related dynamo effects can be separated from other sources of magnetic fluctuations (e.g. piezo magnetic effects, magnetospheric forcing or Rayleigh surface waves) based on time delays from event onset (corresponding closely with travel times for AGWs from ground to the ionosphere) and spectral content measured concurrently in total electron content (TEC). Modeling studies aimed at understanding these magnetic field fluctuations have demonstrated the idea that AGWs propagating through the conducting ionosphere can induce current densities sufficient to produce observable magnetic signatures [Zettergren and Snively, JGR, 120, 2017]. Here, we investigate the features of seismic-related magnetic field fluctuations in data and their generation via the effects of seismically-forced AGWs on the ionosphere [Iyemori et al., EPS, 65, 2013; Hasbi et al., JASTP, 71, 2005]. Concurrent magnetic field and TEC data are analyzed for several events: the Chilean earthquakes of 2010 and 2015, Chile's Calbuco volcano eruption and the Sumatran earthquake on March 28, 2005. We investigate the qualitative features of the disturbances as well as quantitative spectral and timing analysis of the data. For Chilean earthquakes, TEC and ground-based magnetometer data reveal fluctuations in magnetic field exhibiting 4-5 mHz frequencies, the same as in TEC. For the Calbuco volcano eruption and Sumatran earthquake both TEC and magnetic field perturbations exhibit frequencies of 4-5 mHz. The results are consistent with previous reports [Aoyama et al., EPS, 68, 2016, Hasbi et al., JASTP, 71, 2005, Iyemori et al., EPS, 65, 2013]. These observations are further interpreted through detailed numerical

  9. Design and construction of the small wind generator called “AR-SF-500” for the ore milling to a laborator y scale

    OpenAIRE

    Romero Baylón, Alfonso; UNMSM; Flores Chávez, Silvana; UNMSM; Pacheco, Werner; UNMSM

    2014-01-01

    The small wind generator called “AR-SFWP- 500” has a dynamo that generated a potency of 500 watts, which characterize for having in its internal structure, the called “permanent magnet” for working with small wind generators, such as employing in rural zones, where there is a lack of electric energy. In this sense, the purpose of the paper, treats explaining the process of design and construction of the Small Wind Generator AR-SFWP- 500, whose principle of functioning is based in transform th...

  10. The influence of waves on the tidal kinetic energy resource at a tidal stream energy site

    International Nuclear Information System (INIS)

    Guillou, Nicolas; Chapalain, Georges; Neill, Simon P.

    2016-01-01

    Highlights: • We model the influence of waves on tidal kinetic energy in the Fromveur Strait. • Numerical results are compared with field data of waves and currents. • The introduction of waves improve predictions of tidal stream power during storm. • Mean spring tidal stream potential is reduced by 12% during extreme wave conditions. • Potential is reduced by 7.8% with waves forces and 5.3% with enhanced friction. - Abstract: Successful deployment of tidal energy converters relies on access to accurate and high resolution numerical assessments of available tidal stream power. However, since suitable tidal stream sites are located in relatively shallow waters of the continental shelf where tidal currents are enhanced, tidal energy converters may experience effects of wind-generated surface-gravity waves. Waves may thus influence tidal currents, and associated kinetic energy, through two non-linear processes: the interaction of wave and current bottom boundary layers, and the generation of wave-induced currents. Here, we develop a three-dimensional tidal circulation model coupled with a phase-averaged wave model to quantify the impact of the waves on the tidal kinetic energy resource of the Fromveur Strait (western Brittany) - a region that has been identified with strong potential for tidal array development. Numerical results are compared with in situ observations of wave parameters (significant wave height, peak period and mean wave direction) and current amplitude and direction 10 m above the seabed (the assumed technology hub height for this region). The introduction of waves is found to improve predictions of tidal stream power at 10 m above the seabed at the measurement site in the Strait, reducing kinetic energy by up to 9% during storm conditions. Synoptic effects of wave radiation stresses and enhanced bottom friction are more specifically identified at the scale of the Strait. Waves contribute to a slight increase in the spatial gradient of

  11. The quantization of gravity

    CERN Document Server

    Gerhardt, Claus

    2018-01-01

    A unified quantum theory incorporating the four fundamental forces of nature is one of the major open problems in physics. The Standard Model combines electro-magnetism, the strong force and the weak force, but ignores gravity. The quantization of gravity is therefore a necessary first step to achieve a unified quantum theory. In this monograph a canonical quantization of gravity has been achieved by quantizing a geometric evolution equation resulting in a gravitational wave equation in a globally hyperbolic spacetime. Applying the technique of separation of variables we obtain eigenvalue problems for temporal and spatial self-adjoint operators where the temporal operator has a pure point spectrum with eigenvalues $\\lambda_i$ and related eigenfunctions, while, for the spatial operator, it is possible to find corresponding eigendistributions for each of the eigenvalues $\\lambda_i$, if the Cauchy hypersurface is asymptotically Euclidean or if the quantized spacetime is a black hole with a negative cosmological ...

  12. Wave

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    2008-01-01

    Estimates for the amount of potential wave energy in the world range from 1-10 TW. The World Energy Council estimates that a potential 2TW of energy is available from the world’s oceans, which is the equivalent of twice the world’s electricity production. Whilst the recoverable resource is many...

  13. The impact of increased interconnection on electricity systems with large penetrations of wind generation: A case study of Ireland and Great Britain

    DEFF Research Database (Denmark)

    Denny, E.; Tuohy, A.; Meibom, Peter

    2010-01-01

    interconnection for the island of Ireland with large penetrations of wind generation. The results suggest that increased interconnection should reduce average prices in Ireland, and the variability of those prices. The simulations also suggest that while increased interconnection may reduce carbon dioxide...... emissions in Ireland, Great Britain would experience an increase in emissions, resulting in total emissions remaining almost unchanged. The studies suggest that increased interconnection would not reduce excess wind generation. This is because under unit commitment techniques which incorporate wind power...

  14. An overview of wind energy, taking into consideration several imporatn issues, including an analisys of regulatory requirements for the connection of wind generation into the power system