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Sample records for wind ulysses observations

  1. Flow properties of the solar wind obtained from white light data, Ulysses observations and a two-fluid model

    Science.gov (United States)

    Habbal, Shadia Rifai; Esser, Ruth; Guhathakurta, Madhulika; Fisher, Richard

    1995-01-01

    Using the empirical constraints provided by observations in the inner corona and in interplanetary space. we derive the flow properties of the solar wind using a two fluid model. Density and scale height temperatures are derived from White Light coronagraph observations on SPARTAN 201-1 and at Mauna Loa, from 1.16 to 5.5 R, in the two polar coronal holes on 11-12 Apr. 1993. Interplanetary measurements of the flow speed and proton mass flux are taken from the Ulysses south polar passage. By comparing the results of the model computations that fit the empirical constraints in the two coronal hole regions, we show how the effects of the line of sight influence the empirical inferences and subsequently the corresponding numerical results.

  2. Ulysses Observations of Nonlinear Wave-wave Interactions in the ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Astrophysics and Astronomy; Volume 21; Issue 3-4. Ulysses Observations of Nonlinear Wave-wave Interactions in the Source Regions of Type III Solar Radio Bursts. G. Thejappa R. J. MacDowall. Session XI – Solar Wind & Interplanetary Magnetic Fields Volume 21 Issue 3-4 ...

  3. Ulysses observations of latitude gradients in the heliospheric magnetic field

    Science.gov (United States)

    Smith, E. J.; Balogh, A.; Lepping, R. P.; Neugebauer, M.; Phillips, J.; Tsurutani, B. T.

    1995-01-01

    Several parameters measured by Ulysses as it traveled southward to heliographic latitudes of -50 deg are presented and analyzed. The radial component of the magnetic field, averaged over 5 deg latitude increments and extrapolated back to 1 AU, is found to agree with baseline measurements provided by IMP-8. There is little, if any, evidence of a latitude gradient, a result consistent with the dominance of the magnetic field associated with the heliospheric current sheet and with recent models which include the effect of the current sheet as well as of source surface fields. Thus far, the spiral angle agrees with the Parker spiral assuming a rate of rotation of the field lines at the Sun equal to the equatorial value. No evidence is seen of either a change in rotation rate with latitude or an unwinding of the spiral as suggested by a recent analysis. Hourly variances in the field magnitude and in the sum of the variances in the components, normalized to the square of the observed field strenght, show the former to be independent of latitude while the latter shows a strong increase with latitude. These two observations are shown to be associated with Alfven waves that are continuously present at high latitudes. The waves have large amplitudes, extend to long periods, and have important implications for galactic cosmic rays and the solar wind.

  4. Ulysses high energy particle observation of the effects of recurrent high speed streams

    Science.gov (United States)

    Droege, W.; Kunow, H.; Heber, B.; Mueller-Mellin, R.; Sierks, H.; Wibberenz, G.; Raviart, A.; Paizis, C.; Ducros, R.; Ferrando, P.

    1995-01-01

    Since June 1992 The Kiel Electron Telescope on board Ulysses measures variations of more than 10% in the fluxes of high energy H and He showing a periodicity of about 27 days, which are coincident with the passage of corotating interaction refios (CIR). At low energies MeV protons are accelerared at the shocks of the CIRs. These effects were observed up to high southern latitudes, where the signature of time of the conference Ulysses will have passed the solar equator and climbed up to 70 deg N at solar distance of 1.7 AU. In this paper we study the intensity variations with latitude as a function of magnetic rigidity.

  5. (abstract) System Performance of the Joint Galileo/Mars Observer/Ulysses 1993 Gravitational Wave Experiment

    Science.gov (United States)

    Armstrong, J.; Asmar, S.; Caetta, J; Connally, M.; Devereaux, A.; Eshe, P.; Gonzalez, G.; Herrera, R.; Horton, R.; Morabito, D.; hide

    1993-01-01

    From March 21 to April 11, 1993, the Galileo, Mars Observer, and Ulysses spacecraft were tracked almost continuously in a coincidence experiment to search for low-frequency (millihertz) gravitational radiation. We report here a first statistical assessment of the noise characteristics of the data, with particular attention to the performance of the radio science instrumentation itself.

  6. Ulysses Observations of Nonlinear Wave-wave Interactions in the ...

    Indian Academy of Sciences (India)

    tribpo

    Department of Astronomy, University of Maryland, College Park, MD 20742. 2. NASA, Goddard Space Flight Center, Greenbelt, MD 20771. *e-mail: .... power law type energetic electrons present in the solar wind plasmas, provided it is less than the Langmuir wave growth rate γb due to beam plasma instability by an order of ...

  7. Observations of Low-Frequency Magnetic Waves due to Newborn Interstellar Pickup Ions Using ACE, Ulysses, and Voyager Data

    Science.gov (United States)

    Smith, Charles W.; Aggarwal, Poornima; Argall, Matthew R.; Burlaga, Leonard F.; Bzowski, Maciej; Cannon, Bradford E.; Gary, S. Peter; Fisher, Meghan K.; Gilbert, Jason A.; Hollick, Sophia J.; Isenberg, Philip A.; Joyce, Colin J.; Murphy, Neil; Nuno, Raquel G.; Pine, Zackary B.; Richardson, John D.; Schwadron, Nathan A.; Skoug, Ruth M.; Sokół, Justyna M.; Taylor, David K.; Vasquez, Bernard J.

    2017-09-01

    Wave excitation by newborn interstellar pickup ions (PUIs) plays a significant role in theories that attempt to describe IBEX and Voyager observations in the solar wind and heliosheath. The same dynamic processes can be far-reaching and extend into the inner heliosphere to at least 1AU and likely to smaller heliocentric distances. While the high-resolution magnetic field measurements required to study these waves are not yet available in the heliosheath, we have studied a range of available observations and found evidence of waves due to interstellar PUIs using ACE (1998-2015 at 1 AU), Ulysses (1996-2006 at 2 to 5 AU, high and low latitudes) and Voyager (1978-1979 and 2 to 6 AU) observations. Efforts to extend the Voyager observations to 35 AU are ongoing. We have examined these data sets and report on observations of low-frequency waves that result from newborn interstellar pickup H+ and He+ ions. Although not as common as theory originally predicted, we presently have identified 524 independent occurrences. Our conclusion from studying these waves is that they are seen only when the ambient turbulence is sufficiently weak. The instability that generates these waves requires a slow accumulation of wave energy over several to tens of hours to achieve observable wave amplitudes. In regions where the turbulence is moderate to strong, the turbulence absorbs the wave energy before it can reach observable levels and transports the energy to the dissipation scales where it heats the background thermal particles. Only intervals with the weakest turbulence will permit energy accumulation over this time scale. These conditions are most often, but not exclusively, achieved in solar wind rarefaction regions.

  8. ULYSSES comes full circle, before revisiting the Sun's poles

    Science.gov (United States)

    1998-04-01

    slanted orbit took Ulysses to solar latitudes greater than 70 degrees for a total of 234 days -- first in the southern hemisphere and then in the north. Also of great interest was the rapid passage from the south to the north, via the Sun's equatorial region, during which Ulysses covered 160 degrees in solar latitude in less than a year. Nine onboard experiments have gathered data continuously since launch, for international teams totalling 150 scientists. Some instruments detect the outward-blowing solar wind and its magnetic field, which create the heliosphere. Others record cosmic rays coming in from the Galaxy, which are strongly influenced by the solar wind. Ulysses picks up natural radio signals emitted by the Sun, the planets and the heliosphere itself. Innovative techniques identify alien atoms and dust particles infiltrating the heliosphere from interstellar space. Ulysses is also a key member of a network of interplanetary spacecraft making observations of enigmatic bursts of gamma rays originating in the far reaches of the Universe. New facts about the fast solar wind were among Ulysses' most fundamental discoveries. The typical solar wind emerging from the Sun's equatorial zone is variable but relatively slow, at 350-400 kilometres per second. The fast wind blows at a steady 750 kilometres per second. It comes from cool regions of the solar atmosphere called coronal holes which (when the Sun is quiet) are close to the poles and fairly small. Yet Ulysses found the fast wind fanning out to fill two-thirds of the volume of the heliosphere. The boundary between the two windstreams is unexpectedly sharp. The magnetic field of the Sun turns out to be strangely uniform at all latitudes in the heliosphere. Close to the visible surface of the Sun, the magnetic field is strongest over the poles, but this intensification disappears at Ulysses' distance. Apparently magnetic pressure in the solar wind averages out the differences in field strength. On the other hand

  9. Magnetic topology of coronal mass ejection events out of the ecliptic: Ulysses/HI-SCALE energetic particle observations

    Directory of Open Access Journals (Sweden)

    O. E. Malandraki

    Full Text Available Solar energetic particle fluxes (Ee > 38 keV observed by the ULYSSES/HI-SCALE experiment are utilized as diagnostic tracers of the large-scale structure and topology of the Interplanetary Magnetic Field (IMF embedded within two well-identified Interplanetary Coronal Mass Ejections (ICMEs detected at 56° and 62° south heliolatitudes by ULYSSES during the solar maximum southern high-latitude pass. On the basis of the energetic solar particle observations it is concluded that: (A the high-latitude ICME magnetic structure observed in May 2000 causes a depression in the solar energetic electron intensities which can be accounted for by either a detached or an attached magnetic field topology for the ICME; (B during the traversal of the out-of-ecliptic ICME event observed in July 2000 energetic electrons injected at the Sun are channeled by the ICME and propagate freely along the ICME magnetic field lines to 62° S heliolatitude.

    Key words. Interplanetary physics (energetic particles; interplanetary magnetic fields

  10. Magnetic topology of coronal mass ejection events out of the ecliptic: Ulysses/HI-SCALE energetic particle observations

    Directory of Open Access Journals (Sweden)

    O. E. Malandraki

    2003-06-01

    Full Text Available Solar energetic particle fluxes (Ee > 38 keV observed by the ULYSSES/HI-SCALE experiment are utilized as diagnostic tracers of the large-scale structure and topology of the Interplanetary Magnetic Field (IMF embedded within two well-identified Interplanetary Coronal Mass Ejections (ICMEs detected at 56° and 62° south heliolatitudes by ULYSSES during the solar maximum southern high-latitude pass. On the basis of the energetic solar particle observations it is concluded that: (A the high-latitude ICME magnetic structure observed in May 2000 causes a depression in the solar energetic electron intensities which can be accounted for by either a detached or an attached magnetic field topology for the ICME; (B during the traversal of the out-of-ecliptic ICME event observed in July 2000 energetic electrons injected at the Sun are channeled by the ICME and propagate freely along the ICME magnetic field lines to 62° S heliolatitude.Key words. Interplanetary physics (energetic particles; interplanetary magnetic fields

  11. A study of magnetic fluctuations and their anomalous scaling in the solar wind: the Ulysses fast-latitude scan

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    c. Pagel

    2001-01-01

    Full Text Available The solar wind is a highly turbulent and intermittent medium at frequencies between 10-4 and 10-1 Hz. Power spectra are used to look at fluctuations in the components of the magnetic field at high frequencies over a wide range of latitudes. Results show steady turbulence in the polar regions of the Sun and a more varied environment in the equatorial region. The magnetic field fluctuations exhibit anomalous scaling at high frequencies. Various models have been proposed in an attempt to better understand the scaling nature of such fluctuations in neutral fluid turbulence. We have used the Ulysses fast latitude scan data to perform a wide ranging comparison of three such models on the solar wind magnetic field data: the well-known P model, in both its Kolmogorov and Kraichnan forms, the lognormal cascade model and a model adapted from atmospheric physics, the G infinity model. They were tested by using fits to graphs of the structure function exponents g(q, by making a comparison with a non-linear measure of the deviation of g(q from the non-intermittent straight line, and by using extended self similarity technique, over a large range of helio-latitudes. Tests of all three models indicated a high level of intermittency in the fast solar wind, and showed a varied structure in the slow wind, with regions of apparently little intermittency next to regions of high intermittency, implying that the slow wind has no uniform origin. All but one of the models performed well, with the lognormal and Kolmogorov P model performing the best over all the tests, indicating that inhomogeneous energy transfer in the cascade is a good description. The Kraichnan model performed relatively poorly, and the overall results show that the Kraichnan model of turbulence is not well supported over the frequency and distance ranges of our data set. The G infinity model fitted the results surprisingly well and showed that there may very well be important universal geometrical

  12. Ulysses COSPIN observations of cosmic rays and solar energetic particles from the South Pole to the North Pole of the Sun during solar maximum

    Directory of Open Access Journals (Sweden)

    R. B. McKibben

    Full Text Available In 2000–2001 Ulysses passed from the south to the north polar regions of the Sun in the inner heliosphere, providing a snapshot of the latitudinal structure of cosmic ray modulation and solar energetic particle populations during a period near solar maximum.  Observations from the COSPIN suite of energetic charged particle telescopes show that latitude variations in the cosmic ray intensity in the inner heliosphere are nearly non-existent near solar maximum, whereas small but clear latitude gradients were observed during the similar phase of Ulysses’ orbit near the 1994–95 solar minimum. At proton energies above ~10 MeV and extending up to >70 MeV, the intensities are often dominated by Solar Energetic Particles (SEPs accelerated near the Sun in association with intense solar flares and large Coronal Mass Ejections (CMEs. At lower energies the particle intensities are almost constantly enhanced above background, most likely as a result of a mix of SEPs and particles accelerated by interplanetary shocks. Simultaneous high-latitude Ulysses and near-Earth observations show that most events that produce large flux increases near Earth also produce flux increases at Ulysses, even at the highest latitudes attained. Particle anisotropies during particle onsets at Ulysses are typically directed outwards from the Sun, suggesting either acceleration extending to high latitudes or efficient cross-field propagation somewhere inside the orbit of Ulysses. Both cosmic ray and SEP observations are consistent with highly efficient transport of energetic charged particles between the equatorial and polar regions and across the mean interplanetary magnetic fields in the inner heliosphere.

    Key words. Interplanetary physics (cosmic rays – Solar physics, astrophysics and astronomy (energetic particles; flares and mass ejections

  13. Autocorrelation of wind observations

    Science.gov (United States)

    Wylie, D. P.; Hinton, B. B.; Howland, M. R.; Lord, R. J.

    1985-01-01

    Autocorrelation and variance statistics are calculated for cloud motion measurements from four different sources, rawinsonde wind reports, synoptic land station reports, ship reports, aircraft reports, automatic aircraft reports gathered during the Global Weather Experiment, and Seasat scatterometer winds from September 1978. The last of these data sources exhibited the highest autocorrelations and lowest standard deviations over short distances. Structure function plots of autocovariances against separation distance between observations indicated that Seasat was most sensitive to wind field structure by having low autovariance at short distances.

  14. Ulysses reaches maximum latitude over the Sun's northern pole

    Science.gov (United States)

    1995-08-01

    All operations and science experiments continue to go well and NASA's tracking facilities near Madrid and Goldstone, California, are monitoring the spacecraft 24 hours a day as manoeuvres are performed to keep Ulysses' radio antenna pointing toward the Earth. Launched in October 1990 aboard the space shuttle Discovery, the 370-kilogram spacecraft was designed to study the heliosphere - that region of space dominated by the solar wind -at all latitudes above and below the Sun's equatorial plane. These high latitude regions have never been explored before. Named after the legendary adventurer who journeyed to the "hidden" side of the Sun, Ulysses carries nine scientific instruments provided by research institutes in Europe and the United States to make detailed studies of solar wind, magnetic fields, energetic solar and cosmic ray particles, natural radio waves, and interplanetary dust and gas. In addition, a gamma- ray burst detector helps determine the source of the brightest cosmic gamma-ray bursts. In a permanent 6-year orbit about the Sun, the spacecraft is currently travelling at about 90,000 kilometers per hour with respect to the Sun. Having made its greatest northern excursion, Ulysses is now gradually descending in latitude. On 29 September 1995, the spacecraft will complete the northern polar pass and begin to travel back out to the orbit of Jupiter, reaching Jupiter's distance of about 800 million kilometers in April, 1998. Ulysses will then head back on its high latitude trajectory toward the Sun, returning first to the south polar regions in the year 2000, followed by a second flight over the north pole in 2001. Initial results from the climb to high northern latitudes have already confirmed a number of the findings from Ulysses' southern polar pass that took place last year. As expected, once the spacecraft moved away from the equatorial regions heading north, it became permanently immersed in fast solar wind from the northern polar cap. Another

  15. Gamma-ray burst observations with the [ital Compton]/[ital Ulysses]/[ital Pioneer]-[ital Venus] network

    Energy Technology Data Exchange (ETDEWEB)

    Cline, T.L. (NASA/Goddard Space Flight Center, Code 661, Greenbelt, Maryland 20771 (United States)); Hurley, K.C. (University of California, Space Sciences Laboratory, Berkeley, California 94720 (United States)); Sommer, M. (Max-Planck Institut fuer Extraterrestrische Physik, Garching (Germany)); Boer, M.; Niel, M. (Centre d' Etude Spatiale des Rayonnements, Toulouse (France)); Fishman, G.J.; Kouveliotou, C.; Meegan, C.A.; Paciesas, W.S.; Wilson, R.B. (NASA/Marshall Space Flight Center, ES-62, Huntsville, Alabama 35812 (United States)); Fenimore, E.E.; Laros, J.G.; Klebesadel, R.W. (Los Alamos National Laboratory, MS D436, Los Alamos, New Mexico 87545 (United States))

    1993-07-05

    The third and latest interplanetary network for the precise directional analysis of gamma ray bursts consists of the Burst and Transient Source Experiment in [ital Compton] [ital Gamma] [ital Ray] [ital Observatory] and instruments on [ital Pioneer]-[ital Venus] [ital Orbiter] and the deep-space mission [ital Ulysses]. The unsurpassed resolution of the BATSE instrument, the use of refined analysis techniques, and [ital Ulysses]' distance of up to 6 AU all contribute to a potential for greater precision than had been achieved with former networks. Also, the departure of [ital Ulysses] from the ecliptic plane in 1992 avoids any positional alignment of the three instruments that would lessen the source directional accuracy.

  16. Low-energy solar electrons and ions observed at Ulysses February-April, 1991 - The inner heliosphere as a particle reservoir

    Science.gov (United States)

    Roelof, E. C.; Gold, R. E.; Simnett, G. M.; Tappin, S. J.; Armstrong, T. P.; Lanzerotti, L. J.

    1992-01-01

    Ulysses observations at 2.5 AU of 38-315 keV electrons and 61-4752 keV ions during February-April 1991 suggest in several ways that, during periods of sustained high solar activity, the inner heliosphere serves as a 'reservoir' for low-energy solar particles. Particle increases were not associated one-to-one with large X-ray flares because of their poor magnetic connection, yet intensities in March-April remained well above their February levels. The rise phase of the particle event associated with the great flare of 2245UT March 22 lasted most of two days, while throughout the one-week decay phase, the lowest-energy ion fluxes were nearly equal at Ulysses and earth (IMP-8).

  17. Detection of zero anisotropy at 5.2 AU during the November 1998 solar particle event: Ulysses Anisotropy Telescopes observations

    Directory of Open Access Journals (Sweden)

    S. Dalla

    Full Text Available For the first time during the mission, the Anisotropy Telescopes instrument on board the Ulysses spacecraft measured constant zero anisotropy of protons in the 1.3-2.2 MeV energy range, for a period lasting more than three days. This measurement was made during the energetic particle event taking place at Ulysses between 25 November and 15 December 1998, an event characterised by constant high proton fluxes within a region delimited by two interplanetary forward shocks, at a distance of 5.2 AU from the Sun and heliographic latitude of 17°S. We present the ATs results for this event and discuss their possible interpretation and their relevance to the issue of intercalibration of the two telescopes.

    Key words: Interplanetary physics (energetic particles - Solar physics, astrophysics and astronomy (energetic particles - Space plasma physics (instruments and techniques

  18. COOP Wind and Radiation Observations

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind and radiation data from stations in the National Weather Service Cooperative Observers Network. Some precipitation and pressure forms are mistakenly placed in...

  19. Latitudinal and radial variation of >2 GeV/n protons and alpha-particles at solar maximum: ULYSSES COSPIN/KET and neutron monitor network observations

    Directory of Open Access Journals (Sweden)

    A. V. Belov

    2003-06-01

    Full Text Available Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. In 2000/2001 the spacecraft passed from the south to the north polar regions of the Sun in the inner heliosphere. In contrast to the first rapid pole to pole passage in 1994/1995 close to solar minimum, Ulysses experiences now solar maximum conditions. The Kiel Electron Telescope (KET measures also protons and alpha-particles in the energy range from 5 MeV/n to >2 GeV/n. To derive radial and latitudinal gradients for >2 GeV/n protons and alpha-particles, data from the Chicago instrument on board IMP-8 and the neutron monitor network have been used to determine the corresponding time profiles at Earth. We obtain a spatial distribution at solar maximum which differs greatly from the solar minimum distribution. A steady-state approximation, which was characterized by a small radial and significant latitudinal gradient at solar minimum, was interchanged with a highly variable one with a large radial and a small – consistent with zero – latitudinal gradient. A significant deviation from a spherically symmetric cosmic ray distribution following the reversal of the solar magnetic field in 2000/2001 has not been observed yet. A small deviation has only been observed at northern polar regions, showing an excess of particles instead of the expected depression. This indicates that the reconfiguration of the heliospheric magnetic field, caused by the reappearance of the northern polar coronal hole, starts dominating the modulation of galactic cosmic rays already at solar maximum.Key words. Interplanetary physics (cosmic rays; energetic particles – Space plasma physics (charged particle motion and acceleration

  20. Latitudinal and radial variation of >2 GeV/n protons and alpha-particles at solar maximum: ULYSSES COSPIN/KET and neutron monitor network observations

    Directory of Open Access Journals (Sweden)

    A. V. Belov

    Full Text Available Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. In 2000/2001 the spacecraft passed from the south to the north polar regions of the Sun in the inner heliosphere. In contrast to the first rapid pole to pole passage in 1994/1995 close to solar minimum, Ulysses experiences now solar maximum conditions. The Kiel Electron Telescope (KET measures also protons and alpha-particles in the energy range from 5 MeV/n to >2 GeV/n. To derive radial and latitudinal gradients for >2 GeV/n protons and alpha-particles, data from the Chicago instrument on board IMP-8 and the neutron monitor network have been used to determine the corresponding time profiles at Earth. We obtain a spatial distribution at solar maximum which differs greatly from the solar minimum distribution. A steady-state approximation, which was characterized by a small radial and significant latitudinal gradient at solar minimum, was interchanged with a highly variable one with a large radial and a small – consistent with zero – latitudinal gradient. A significant deviation from a spherically symmetric cosmic ray distribution following the reversal of the solar magnetic field in 2000/2001 has not been observed yet. A small deviation has only been observed at northern polar regions, showing an excess of particles instead of the expected depression. This indicates that the reconfiguration of the heliospheric magnetic field, caused by the reappearance of the northern polar coronal hole, starts dominating the modulation of galactic cosmic rays already at solar maximum.

    Key words. Interplanetary physics (cosmic rays; energetic particles – Space plasma physics (charged particle motion and acceleration

  1. The solar wind at solar maximum: comparisons of EISCAT IPS and in situ observations

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    A. R. Breen

    Full Text Available The solar maximum solar wind is highly structured in latitude, longitude and in time. Coronal measurements show a very high degree of variability, with large variations that are less apparent within in situ spacecraft measurements. Interplanetary scintillation (IPS observations from EISCAT, covering distances from 20 to 100 solar radii (RS, are an ideal source of information on the inner solar wind and can be used, therefore, to cast light on its evolution with distance from the Sun. Earlier comparisons of in situ and IPS measurements under solar minimum conditions showed good large-scale agreement, particularly in the fast wind. In this study we attempt a quantitative comparison of measurements made over solar maximum by EISCAT (20–100 RS and the Wind and Ulysses spacecraft (at 215 RS and 300–1000 RS, respectively. The intervals studied were August–September 1999, May 2000, September 2000 and May 2001, the last-named being the period of the second Ulysses fast latitude scan. Both ballistic and – when possible – MHD/ballistic hybrid models were used to relate the data sets, and we compare the results obtained from these two mapping methods. The results of this study suggest that solar wind velocities measured in situ were less variable than those estimated from IPS measurements closer to the Sun, with the greatest divergence between IPS velocities and in situ measurements occurring in regions where steep longitudinal velocity gradients were seen in situ. We suggest that the interaction between streams of solar wind with different velocities leads to "smoothing" of solar wind velocities between 30–60 RS and 1 AU, and that this process continues at greater distances from the Sun.

    Key words. Interplanetary physics (solar wind plasma; sources of the solar wind; instruments and techniques

  2. Kinetic Features Observed in the Solar Wind Electron Distributions

    Science.gov (United States)

    Pierrard, V.; Lazar, M.; Poedts, S.

    2016-12-01

    More than 120 000 of velocity distributions measured by Helios, Cluster and Ulysses in the ecliptic have been analyzed within an extended range of heliocentric distances from 0.3 to over 4 AU. The velocity distribution of electrons reveal a dual structure with a thermal (Maxwellian) core and a suprathermal (Kappa) halo. A detailed observational analysis of these two components provides estimations of their temperatures and temperature anisotropies, and we decode any potential interdependence that their properties may indicate. The core temperature is found to decrease with the radial distance, while the halo temperature slightly increases, clarifying an apparent contradiction in previous observational analysis and providing valuable clues about the temperature of the Kappa-distributed populations. For low values of the power-index kappa, these two components manifest a clear tendency to deviate from isotropy in the same direction, that seems to confirm the existence of mechanisms with similar effects on both components, e.g., the solar wind expansion, or the particle heating by the fluctuations. However, the existence of plasma states with anti-correlated anisotropies of the core and halo populations and the increase of their number for high values of the power-index kappa suggest a dynamic interplay of these components, mediated most probably by the anisotropy-driven instabilities. Estimating the temperature of the solar wind particles and their anisotropies is particularly important for understanding the origin of these deviations from thermal equilibrium as well as their effects.

  3. Charge state evolution in the solar wind. III. Model comparison with observations

    Energy Technology Data Exchange (ETDEWEB)

    Landi, E.; Oran, R.; Lepri, S. T.; Zurbuchen, T. H.; Fisk, L. A.; Van der Holst, B. [Department of Atmospheric, Oceanic and Space Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

    2014-08-01

    We test three theoretical models of the fast solar wind with a set of remote sensing observations and in-situ measurements taken during the minimum of solar cycle 23. First, the model electron density and temperature are compared to SOHO/SUMER spectroscopic measurements. Second, the model electron density, temperature, and wind speed are used to predict the charge state evolution of the wind plasma from the source regions to the freeze-in point. Frozen-in charge states are compared with Ulysses/SWICS measurements at 1 AU, while charge states close to the Sun are combined with the CHIANTI spectral code to calculate the intensities of selected spectral lines, to be compared with SOHO/SUMER observations in the north polar coronal hole. We find that none of the theoretical models are able to completely reproduce all observations; namely, all of them underestimate the charge state distribution of the solar wind everywhere, although the levels of disagreement vary from model to model. We discuss possible causes of the disagreement, namely, uncertainties in the calculation of the charge state evolution and of line intensities, in the atomic data, and in the assumptions on the wind plasma conditions. Last, we discuss the scenario where the wind is accelerated from a region located in the solar corona rather than in the chromosphere as assumed in the three theoretical models, and find that a wind originating from the corona is in much closer agreement with observations.

  4. The solar wind as a turbulence laboratory- some new quantitative points of contact between theory, simulation and solar wind observations

    Science.gov (United States)

    Chapman, S. C.; Gogoberidze, G.; Hnat, B.; Mueller, W.-C.; Turner, A. J.

    2012-04-01

    The solar wind flow has a Reynolds number of order 105. Single point observations suitable for the study of turbulence are on timescales from below ion kinetic scales up to days. Central to the concept of using the solar wind as a test laboratory for plasma turbulence are methods that allow direct quantitative comparison between the predictions of theory and simulation, and the observations. Critically, theoretical predictions, and data analysis methods, must come together in a manner in which uncertainties can be well understood, and thus different theoretical scenarios be distinguished unambiguously. Scaling is a key prediction of theories of infinite range turbulence. Its full characterization requires the scaling exponents of all the moments of the probability density of fluctuations as a function of scale. In practice, only the first few moments are accessible. Most comparisons with theory focus on the second moment scaling, that is, the exponent of the power spectral density (PSD). Solar wind plasma turbulence is anisotropic due to the presence of a background field, so that in general the power spectral density (or correlation) tensor is needed to characterise the turbulence. We focus on the ratios of the PSD tensor terms which are sensitive to the scaling exponent, providing a method for direct observational tests of theories. The reduced PSD tensor accessed by single spacecraft measurements yields ratios of perpendicular terms which we show are robust to uncertainties. These can clearly distinguish turbulence theories as we show for the Goldreich-Sridhar model of MHD turbulence, and the 'slab-2D' solar wind model, which we compare with ULYSSES observations. The comparison between solar wind observations, and 'fly throughs' of DNS of MHD turbulence, is also an informative tool to understand the reduced PSD tensor. We will use this alongside Cluster observations to propose an origin of the observed non-axisymmetry of solar wind turbulence. Properties of the

  5. The Ulysses fast latitude scans: COSPIN/KET results

    Directory of Open Access Journals (Sweden)

    B. Heber

    2003-06-01

    Full Text Available Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in December 1997, and its second fast latitude scan in September 2000. In contrast to the first fast latitude scan in 1994/1995, during the second fast latitude scan solar activity was close to maximum. The solar magnetic field reversed its polarity around July 2000. While the first latitude scan mainly gave a snapshot of the spatial distribution of galactic cosmic rays, the second one is dominated by temporal variations. Solar particle increases are observed at all heliographic latitudes, including events that produce >250 MeV protons and 50 MeV electrons. Using observations from the University of Chicago’s instrument on board IMP8 at Earth, we find that most solar particle events are observed at both high and low latitudes, indicating either acceleration of these particles over a broad latitude range or an efficient latitudinal transport. The latter is supported by "quiet time" variations in the MeV electron background, if interpreted as Jovian electrons. No latitudinal gradient was found for >106 MeV galactic cosmic ray protons, during the solar maximum fast latitude scan. The electron to proton ratio remains constant and has practically the same value as in the previous solar maximum. Both results indicate that drift is of minor importance. It was expected that, with the reversal of the solar magnetic field and in the declining phase of the solar cycle, this ratio should increase. This was, however, not observed, probably because the transition to the new magnetic cycle was not completely terminated within the heliosphere, as indicated by the Ulysses magnetic field and solar wind measurements. We argue that the new A<0-solar magnetic modulation epoch will establish itself once both polar coronal holes have developed.Key words. Interplanetary physics (cosmic rays; energetic particles; interplanetary magnetic fields

  6. [Ulysses contract in psychiatry].

    Science.gov (United States)

    Daverio, Andrea; Piazzi, Gioia; Saya, Anna

    2017-01-01

    Over the last twenty years we have witnessed a growing focus on the rights of the ill people. The debate on informed consent and a new redefinition of the therapeutic relationship is constantly evolving. With this article, we propose a critical literature review of the so-called "Ulysses contract" or "psychiatric advance directives". It refers to the will that a subject expresses in writing, or orally, about the treatments he or she wishes or does not wish to be subject to if the time comes when it may be impossible to express his/her consent. This can especially occur in those with psychiatric disorders with serious clinical involvement and remitting-relapse (typically bipolar disorder, but also chronic delusional disorders and schizophrenia). In this context, the question is whether during intercritical periods the patient may or may not leave instructions to their care-givers. This aspect opens up to a series of interdisciplinary problems. In this article, we want to show the complexity of this debate from a clinical, ethical, legal and psychodynamic point of view, emphasizing the strengths and the major criticisms of the psychiatric advance directives for each area.

  7. Pickup Protons: Comparisons using the Three-Dimensional MHD HHMS-PI model and Ulysses SWICS Measurements

    Science.gov (United States)

    Intriligator, Devrie S.; Detman, Thomas; Gloecker, George; Gloeckler, Christine; Dryer, Murray; Sun, Wei; Intriligator, James; Deehr, Charles

    2012-01-01

    We report the first comparisons of pickup proton simulation results with in situ measurements of pickup protons obtained by the SWICS instrument on Ulysses. Simulations were run using the three dimensional (3D) time-dependent Hybrid Heliospheric Modeling System with Pickup Protons (HHMS-PI). HHMS-PI is an MHD solar wind model, expanded to include the basic physics of pickup protons from neutral hydrogen that drifts into the heliosphere from the local interstellar medium. We use the same model and input data developed by Detman et al. (2011) to now investigate the pickup protons. The simulated interval of 82 days in 2003 2004, includes both quiet solar wind (SW) and also the October November 2003 solar events (the Halloween 2003 solar storms). The HHMS-PI pickup proton simulations generally agree with the SWICS measurements and the HHMS-PI simulated solar wind generally agrees with SWOOPS (also on Ulysses) measurements. Many specific features in the observations are well represented by the model. We simulated twenty specific solar events associated with the Halloween 2003 storm. We give the specific values of the solar input parameters for the HHMS-PI simulations that provide the best combined agreement in the times of arrival of the solar-generated shocks at both ACE and Ulysses. We show graphical comparisons of simulated and observed parameters, and we give quantitative measures of the agreement of simulated with observed parameters. We suggest that some of the variations in the pickup proton density during the Halloween 2003 solar events may be attributed to depletion of the inflowing local interstellar medium (LISM) neutral hydrogen (H) caused by its increased conversion to pickup protons in the immediately preceding shock.

  8. Total lightning observations to wind turbines

    OpenAIRE

    Montañá Puig, Juan; Van der Velde, Oscar Arnoud; Romero Durán, David; March Nomen, Víctor; Solà de Las Fuentes, Gloria; Pineda Ruegg, Nicolau; Hermoso Alameda, Blas; Senosiáin Miquélez, Vicente

    2012-01-01

    In summer 2011 a new VHF Lightning Mapping Array was installed at the northeast of Spain. In that area a VHF interferometer and a VLFILF lightning detection networks are also operative. The close presence of wind farms in the area of the Lightning Mapping Array showed some lightning activity not reported before. This paper describes the observations and discusses the possible effects to the wind turbine lightning protection

  9. Ulysses Data Analysis: Magnetic Topology of Heliospheric Structures

    Science.gov (United States)

    Crooker, Nancy

    2001-01-01

    In this final technical report on research funded by a NASA grant, a project overview is given by way of summaries on nine published papers. Research has included: 1) Using suprathermal electron data to study heliospheric magnetic structures; 2) Analysis of magnetic clouds, coronal mass ejections (CME), and the heliospheric current sheet (HCS); 3) Analysis of the corotating interaction region (CIR) which develop from interactions between solar wind streams of different velocities; 4) Use of Ulysses data in the interpretation of heliospheric events and phenomena.

  10. ULYSSES JUPITER HISCALE DEFLECTED ELECTRONS COUNTS

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of HISCALE Deflected Electron (DE) measurements taken during the Ulysses Jupiter encounter 1991-12-31 to 1992-02-16. This includes 1 hour...

  11. The Influence of Pickup Protons, from Interstellar Neutral Hydrogen, on the Propagation of Interplanetary Shocks from the Halloween 2003 Solar Events to ACE and Ulysses: A 3-D MHD Modeling Study

    Science.gov (United States)

    Detman, T. R.; Intriligator, D. S.; Dryer, M.; Sun, W.; Deehr, C. S.; Intriligator, J.

    2012-01-01

    We describe our 3-D, time ]dependent, MHD solar wind model that we recently modified to include the physics of pickup protons from interstellar neutral hydrogen. The model has a time-dependent lower boundary condition, at 0.1 AU, that is driven by source surface map files through an empirical interface module. We describe the empirical interface and its parameter tuning to maximize model agreement with background (quiet) solar wind observations at ACE. We then give results of a simulation study of the famous Halloween 2003 series of solar events. We began with shock inputs from the Fearless Forecast real ]time shock arrival prediction study, and then we iteratively adjusted input shock speeds to obtain agreement between observed and simulated shock arrival times at ACE. We then extended the model grid to 5.5 AU and compared those simulation results with Ulysses observations at 5.2 AU. Next we undertook the more difficult tuning of shock speeds and locations to get matching shock arrival times at both ACE and Ulysses. Then we ran this last case again with neutral hydrogen density set to zero, to identify the effect of pickup ions. We show that the speed of interplanetary shocks propagating from the Sun to Ulysses is reduced by the effects of pickup protons. We plan to make further improvements to the model as we continue our benchmarking process to 10 AU, comparing our results with Cassini observations, and eventually on to 100 AU, comparing our results with Voyager 1 and 2 observations.

  12. ULYSSES JUPITER EPAC OMNI-DIRECTIONAL ELECTRON FLUX

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains Ulysses Energetic Particle Composition Experiment (EPAC) 1 hour averaged omni-directional electron flux data from the Ulysses Jupiter...

  13. ULYSSES JUPITER SOLAR CORONA EXPER. RANGING DATA 10 MIN AVG

    Data.gov (United States)

    National Aeronautics and Space Administration — The Ulysses spacecraft was occulted by the Io Plasma Torus (IPT) during its Jupiter encounter on 8 February 1992. The Ulysses dual-frequency radio subsystem used by...

  14. Remote sensing observation used in offshore wind energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Pena Diaz, Alfredo; Christiansen, Merete Bruun

    2008-01-01

    Remote sensing observations used in offshore wind energy are described in three parts: ground-based techniques and applications, airborne techniques and applications, and satellite-based techniques and applications. Ground-based remote sensing of winds is relevant, in particular, for new large wind...

  15. Half Sinful Words: Disguised Grief in "Ulysses."

    Science.gov (United States)

    Hobbs, Michael

    As a shrewd technician of the language, A. L. Tennyson rightly understood that words are not controllable; they do not always obey rules. As Tennyson said, words "half reveal and half conceal the soul within." In "Ulysses," the title character's speech to his fellow mariners--where he attempts to explain why he has decided to…

  16. Jovian bremsstrahlung X-rays - A Ulysses prediction

    Science.gov (United States)

    Waite, J. H., Jr.; Boice, D. C.; Hurley, K. C.; Stern, S. A.; Sommer, M.

    1992-01-01

    Modeling results reported here show that precipitating auroral electrons with sufficient energy to be consistent with the Voyager UVS observations produce bremsstrahlung X-rays with sufficient energy and intensity to be detected by the Solar Flare X-ray and Cosmic-Ray-Burst Instrument on board the Ulysses spacecraft. The detection of such bremsstrahlung X-rays at Jupiter would provide strong evidence for the electron-precipitation mechanism, although it does not rule out the possibility of some heavy ion involvement, and thus makes a significant contribution toward solving the mystery of the Jovian aurora.

  17. A Ulysses Detection of Secondary Helium Neutrals

    Science.gov (United States)

    Wood, Brian E.; Müller, Hans-Reinhard; Witte, Manfred

    2017-12-01

    The Interstellar Boundary EXplorer (IBEX) mission has recently studied the flow of interstellar neutral He atoms through the solar system and discovered the existence of a secondary He flow that likely originates in the outer heliosheath. We find evidence for this secondary component in Ulysses data. By coadding hundreds of Ulysses He beam maps together to maximize signal-to-noise ratio, we identify a weak signal that is credibly associated with the secondary component. Assuming a laminar flow from infinity, we infer the following He flow parameters: V=12.8+/- 1.9 km s-1, λ =74\\buildrel{\\circ}\\over{.} 4+/- 1\\buildrel{\\circ}\\over{.} 8, β =-10\\buildrel{\\circ}\\over{.} 5+/- 4\\buildrel{\\circ}\\over{.} 1, and T=3000+/- 1100 K; where λ and β are the ecliptic longitude and latitude direction in J2000 coordinates. The secondary component has a density that is 4.9 ± 0.9% that of the primary component. These measurements are reasonably consistent with measurements from IBEX, with the exception of temperature, where our temperature is much lower than IBEX’s T = 9500 K. Even the higher IBEX temperature is suspiciously low compared to expectactions for the outer heliosheath source region. The implausibly low temperatures are due to the incorrect assumption of a laminar flow instead of a diverging one, given that the flow in the outer heliosheath source region will be deflecting around the heliopause. As for why the IBEX and Ulysses T values are different, difficulties with background subtraction in the Ulysses data are a potential source of concern, but the discrepancy may also be another effect of the improper laminar flow assumption, which could affect the IBEX and Ulysses analyses differently.

  18. Automatic Classification of Offshore Wind Regimes With Weather Radar Observations

    DEFF Research Database (Denmark)

    Trombe, Pierre-Julien; Pinson, Pierre; Madsen, Henrik

    2014-01-01

    Weather radar observations are called to play an important role in offshore wind energy. In particular, they can enable the monitoring of weather conditions in the vicinity of large-scale offshore wind farms and thereby notify the arrival of precipitation systems associated with severe wind...... and amplitude) using reflectivity observations from a single weather radar system. A categorical sequence of most likely wind regimes is estimated from a wind speed time series by combining a Markov-Switching model and a global decoding technique, the Viterbi algorithm. In parallel, attributes of precipitation...... systems are extracted from weather radar images. These attributes describe the global intensity, spatial continuity and motion of precipitation echoes on the images. Finally, a CART classification tree is used to find the broad relationships between precipitation attributes and wind regimes...

  19. Modelling cosmic ray intensities along the Ulysses trajectory

    Directory of Open Access Journals (Sweden)

    D. C. Ndiitwani

    2005-03-01

    Full Text Available Time dependent cosmic ray modulation in the inner heliosphere is studied by comparing results from a 2-D, time-dependent cosmic ray transport model with Ulysses observations. A compound approach, which combines the effects of the global changes in the heliospheric magnetic field magnitude with drifts to establish a realistic time-dependence, in the diffusion and drift coefficients, are used. We show that this model results in realistic cosmic ray modulation from the Ulysses launch (1990 until recently (2004 when compared to 2.5-GV electron and proton and 1.2-GV electron and Helium observations from this spacecraft. This approach is also applied to compute radial gradients present in 2.5-GV cosmic ray electron and protons in the inner heliosphere. The observed latitude dependence for both positive and negative charged particles during both the fast latitude scan periods, corresponding to different solar activity conditions, could also be realistically computed. For this an additional reduction in particle drifts (compared to diffusion toward solar maximum is needed. This results in a realistic charge-sign dependent modulation at solar maximum and the model is also applied to predict charge-sign dependent modulation up to the next expected solar minimum.

  20. COMPARATIVE ANALYSIS OF ULYSSES AND TUTUNAMAYANLAR / ULYSSES ve TUTUNAMAYANLAR’IN KARSILASTIRMALI İNCELEMESİ

    Directory of Open Access Journals (Sweden)

    Dr. Mümtaz SARIÇİÇEK

    2009-01-01

    Full Text Available ‘Modernist novel’ has been flourished with a newaesthetical manner opposite to ‘traditional novel’ sinceends of the 19. century and prepared ‘postmodernistnovel’. Term of the ‘modernist’ also contains politicalmeaning, therefore, it is supposed that modernistnovelists adopt the political modernizm. Whereasmodernist novel was flourished by the antimodernistpolitical writers. That’s way, it is prefered one the terms‘avant-gardist’, ‘pre’, ‘pioner’, ‘early’ ‘postmodernist novel’then ‘modernist novel’.Ulysses, written by James Joyce, is one of themost important of these novels. In Ulysses, James Joyceadopts a new formal and thematically aesthetic andinspires from Homeros’ Odysseia. Thus, he revolutionizedon the novel technique.Turkish novelist Oğuz Atay’s Tutunamayanlarinspires Ulysses, and the same as Ulysses’ effect onworld’s novel, it converted radically Turkish novel. Thisnovel constitutes intertextualite with Ulysses and PaleFire written by Vladimir Nabokov.This article is a study of comparative literatureand, Tutunamayanlar is compared with Ulysses in thisarticle. In addition, it is referred to relationsTutunamayanlar with Solgun Ates and Zafernâme.

  1. Observations and physical interpretations of the solar wind flow properties as obtained from white light coronagraph aboard SPARTAN 201-01

    Science.gov (United States)

    Guhathakurta, Madhulika; Fisher, Richard; Ofman, Leon

    1995-01-01

    The solar corona was observed with an externally occulted White Light Coronagraph (WLC) carried on the SPARTAN 201-1 spacecraft on 11-12 Apr. 1993. With observations from WLC and the ground based Mauna Loa White Light Coronagraph, a large number of polar plumes both in the north and south polar holes were traced from 1.16 to 5.5 Rs. Flow properties of the solar wind in coronal holes have been determined (Habbal et al., 1995) by using a two fluid model constrained by density profiles and scale height temperatures from the white light observations, and interplanetary measurements of the flow speed and proton mass flux from Ulysses' south polar passage. Provisions for acceleration by Alfven waves, as well as electron and proton heating, are included in the momentum and the energy equations respectively. The model computations fit remarkably well the empirical constraints of the two different density structures (plumes and coronal holes) for a range of input parameters. In this study we investigate the physical nature of the heating function used in the two-fluid model. Alfven waves have been suggested as the possible source of heating that accelerates the solar wind (Ofman and Davila, 1995). We utilize the density contrast observed in WLC data in the plume and ambient coronal hole region to estimate the Alfven wave frequencies responsible for heating these structures. The source heating function utilized in the two fluid model of the solar wind acceleration will be compared with the resonant Alfven wave heating function.

  2. Observability of wind power; Observabilite de la production eolienne

    Energy Technology Data Exchange (ETDEWEB)

    Gonot, J.P. [Reseau de Transport d' Electricite, Dir. du Projet IPES, 92 - La Defense (France); Fraisse, J.L. [Electricite Reseau Distribution France (ERDF), Service Raccordement, 92 - Paris la defense (France)

    2009-10-15

    The total installed capacity of wind power grows from a few hundred MW at the beginning of 2005 to 3400 MW at the end of 2008. With such a trend, a total capacity of 7000 MW could be reached by 2010. The natural variability of wind power and the difficulty of its predictability require a change in the traditional way of managing supply/demand balance, day-ahead margins and the control of electrical flows. As a consequence, RTE operators should be informed quickly and reliably of the real time output power of wind farms and of its evolvement some hours or days ahead to ensure the reliability of the French electrical power system. French specificities are that wind farms are largely spread over the territory, that 95 % of wind farms have an output power below 10 MW and that they are connected to the distribution network. In this context, new tools were necessary to acquire as soon as possible data concerning wind power. In two years long, RTE set up an observatory of wind production 'IPES system' enable to get an access to the technical characteristics of the whole wind farms, to observe in real time 75 % of the wind generation and to implement a forecast model related to wind generation. (authors)

  3. Fault tolerant control of wind turbines using unknown input observers

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Stoustrup, Jakob

    2012-01-01

    This paper presents a scheme for accommodating faults in the rotor and generator speed sensors in a wind turbine. These measured values are important both for the wind turbine controller as well as the supervisory control of the wind turbine. The scheme is based on unknown input observers, which ...... are also used to detect and isolate these faults. The scheme is tested on a known benchmark for FDI and FTC of wind turbines. Tests on this benchmark model show a clear potential of the proposed scheme....

  4. Offshore Wind Energy: Wind and Sea Surface Temperature from Satellite Observations

    DEFF Research Database (Denmark)

    Karagali, Ioanna

    available wind speed and direction observations over the ocean and for a better understanding of the marine atmospheric boundary layer (MABL). The sea surface temperature (SST) has a direct impact on the marine atmospheric boundary layer, as the top few meters of the ocean have the same heat capacity...... as the entire atmosphere above. Under conditions of light winds and strong solar insolation, warming of the upper oceanic layer may occur. In this PhD study, remote sensing from satellites is used to obtain information for the near-surface ocean wind and the sea surface temperature over the North Sea...... and the Baltic Sea. The aim is to evaluate their potential use and demonstrate their applicability within the context of offshore wind energy; for the quantication of the wind resources and for the identication of diurnal warming of the sea surface temperature. Space-borne observations of wind are obtained from...

  5. Hourly wind profiler observations of the jet stream - Wind shear and pilot reports of turbulence

    Science.gov (United States)

    Syrett, William J.

    1991-01-01

    Hourly wind profiler observations of the jet stream are reported on the basis of over 400 hr of wind and temperature data taken during two prolonged jet stream passages over western and central Pennsylvania during mid-November 1986 and mid-January 1987. The mean wind speed profile with error bars for the 79 hr that the Crown radar was determined to be 'under' the jet stream is shown. A mean speed of 83 m/s for the period was found. A plot of wind shear for the hours of interest is given. Typically, the shear was at a maximum from 3 to 4 km below the level of maximum wind. Thus, an aircraft would have to fly through potentially rough air to reach the fuel savings and relative smoothness of flight at the jet stream level. A good correlation between pilot reports of turbulence and wind shear was found.

  6. ULYSSES JUPITER EPAC PRTL2 SECTORED PROTON FLUX 1 HR V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set contains Ulysses Energetic Particle Composition Experiment (EPAC) 1 hour averaged sectored proton flux data from the Ulysses Jupiter encounter...

  7. Ice detection on wind turbines using observed power curve

    DEFF Research Database (Denmark)

    Davis, Neil; Byrkjedal, Øyvind; Hahmann, Andrea N.

    2016-01-01

    Icing on the blades of a wind turbine can lead to significant production losses during the winter months for wind parks in cold climate regions. However, there is no standard way of identifying ice-induced power loss. This paper describes three methods for creating power threshold curves that can...... to turbines in four wind parks and compared with each other and to observations of icing on the nacelle of one of the turbines in each park. It is found that setting an ice threshold curve using 0.1 quantile of the observed power data during normal operation with a 2-h minimum duration is the best approach...

  8. Upper wind observing systems used for meteorological operations

    Directory of Open Access Journals (Sweden)

    J. Nash

    Full Text Available Methods of upper wind measurements used in operational meteorology have been reviewed to provide guidance to those developing wind profiler radar systems. The main limitations of the various methods of tracking weather balloons are identified using results from the WMO radiosonde comparisons and additional tests in the United Kingdom. Costs associated with operational balloon measurements are reviewed. The sampling and quality of operational aircraft wind observations are illustrated with examples from the ASDAR system. Measurement errors in horizontal winds are quantified wherever possible. When tracking equipment is functioning correctly, random errors in southerly and westerly wind component measurements from aircraft and weather balloons are usually in the range 0.5-2 m s-1.

  9. STEREO Observations of Turbulent Solar Wind Waveforms

    Science.gov (United States)

    Kellogg, Paul J.; Goetz, Keith; Monson, Steven J.

    2017-04-01

    Studies of solar wind turbulence have heretofore concentrated on Kolmogorov-type studies of the full MHD equations, without regard to the separate modes of the possible solutions. Further understanding of the nonlinear processes of the cascade, and especially transference of wave energy to particles, would seem to depend on more detailed understanding of the waves, their modes and their separate electric and magnetic fields. . A part of the SWAVES experiment on the STEREO spacecraft was designed to study the waves in the dissipation region of the turbulence spectrum. However, compatibility with SECCHI, the optical sensors, required that only monopole antennas could be accommodated, and these respond both to electric fields and to density fluctuations. This seemed to require that one measure four quantities with only three signals. After several years, the response of the antennas to density fluctuations was reduced, due to changes in photoemission coefficients, and measurement of separate electric fields became possible. It is found that sometimes there are short periods when a sinusoidal waveform appears which seems sufficiently pure to represent a single mode. Results of study of the fields of such waves will be presented.

  10. Observed Thermal Impacts of Wind Farms Over Northern Illinois.

    Science.gov (United States)

    Slawsky, Lauren M; Zhou, Liming; Baidya Roy, Somnath; Xia, Geng; Vuille, Mathias; Harris, Ronald A

    2015-06-25

    This paper assesses impacts of three wind farms in northern Illinois using land surface temperature (LST) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments onboard the Terra and Aqua satellites for the period 2003-2013. Changes in LST between two periods (before and after construction of the wind turbines) and between wind farm pixels and nearby non-wind-farm pixels are quantified. An areal mean increase in LST by 0.18-0.39 °C is observed at nighttime over the wind farms, with the geographic distribution of this warming effect generally spatially coupled with the layout of the wind turbines (referred to as the spatial coupling), while there is no apparent impact on daytime LST. The nighttime LST warming effect varies with seasons, with the strongest warming in winter months of December-February, and the tightest spatial coupling in summer months of June-August. Analysis of seasonal variations in wind speed and direction from weather balloon sounding data and Automated Surface Observing System hourly observations from nearby stations suggest stronger winds correspond to seasons with greater warming and larger downwind impacts. The early morning soundings in Illinois are representative of the nighttime boundary layer and exhibit strong temperature inversions across all seasons. The strong and relatively shallow inversion in summer leaves warm air readily available to be mixed down and spatially well coupled with the turbine. Although the warming effect is strongest in winter, the spatial coupling is more erratic and spread out than in summer. These results suggest that the observed warming signal at nighttime is likely due to the net downward transport of heat from warmer air aloft to the surface, caused by the turbulent mixing in the wakes of the spinning turbine rotor blades.

  11. Observed Thermal Impacts of Wind Farms Over Northern Illinois

    Directory of Open Access Journals (Sweden)

    Lauren M. Slawsky

    2015-06-01

    Full Text Available This paper assesses impacts of three wind farms in northern Illinois using land surface temperature (LST data from the Moderate Resolution Imaging Spectroradiometer (MODIS instruments onboard the Terra and Aqua satellites for the period 2003–2013. Changes in LST between two periods (before and after construction of the wind turbines and between wind farm pixels and nearby non-wind-farm pixels are quantified. An areal mean increase in LST by 0.18–0.39 °C is observed at nighttime over the wind farms, with the geographic distribution of this warming effect generally spatially coupled with the layout of the wind turbines (referred to as the spatial coupling, while there is no apparent impact on daytime LST. The nighttime LST warming effect varies with seasons, with the strongest warming in winter months of December-February, and the tightest spatial coupling in summer months of June-August. Analysis of seasonal variations in wind speed and direction from weather balloon sounding data and Automated Surface Observing System hourly observations from nearby stations suggest stronger winds correspond to seasons with greater warming and larger downwind impacts. The early morning soundings in Illinois are representative of the nighttime boundary layer and exhibit strong temperature inversions across all seasons. The strong and relatively shallow inversion in summer leaves warm air readily available to be mixed down and spatially well coupled with the turbine. Although the warming effect is strongest in winter, the spatial coupling is more erratic and spread out than in summer. These results suggest that the observed warming signal at nighttime is likely due to the net downward transport of heat from warmer air aloft to the surface, caused by the turbulent mixing in the wakes of the spinning turbine rotor blades.

  12. Gap Winds and Wakes: SAR Observations and Numerical Simulations.

    Science.gov (United States)

    Pan, Feifei; Smith, Ronald B.

    1999-04-01

    The nature of terrain-induced gap winds and wakes in the atmosphere is examined using surface wind data from synthetic aperture radar (SAR) and the shallow water equations. The shallow water model is used to predict the types of wake-jet wind patterns that might occur behind an idealized pair of bell-shaped hills with a gap between them. A regime diagram is constructed based on the width of the gap and the upstream Froude number. Specific predictions of the model are found to compare moderately well with SAR data from four examples of airflow near Unimak Island in the Aleutian Chain. The model predicts the observed wakes and jets, including jets that exceed the upstream speed. Theoretical analysis considers the relative importance of rising terrain and narrowing valley walls in the acceleration of gap winds. Wind speeds in the wake region are controlled by the Bernoulli function and regional pressure. Gap winds therefore are streams of air that have avoided Bernoulli loss over the terrain by passing through gaps. The speed of gap winds can exceed the upstream speed only in ridgelike situations when the regional leeside pressure is lower than the upstream pressure.

  13. Wind observations by the E-Region Wind Interferometer, ERWIN-2 at Eureka

    Science.gov (United States)

    Kristoffersen, S.; Brown, S.; Ward, W. E.

    2009-05-01

    The E-region wind interferometer, ERWIN, was refurbished and moved from Resolute Bay to the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka (80N) in the winter of 2008. ERWIN is a field widened Michelson interferometer which measures winds in the E-region using Doppler shifts in hydroxyl, oxygen green line and O2 airglow emssions. The referbished instrument is constructed around the old interferometer and includes imaging capabilities using a CCD detector and an optical system which allows simultaneous viewing in four directions and zenith. The instrument operates by seqentially viewing the three emissions. The observation cadence for the three emissions is ~2 minutes making this the fastest wind measuring instrument in the world for the mesopause region. An overview of the instrument operation and results from the first year of observations (including winds during stratospheric warmings) are presented.

  14. Electromagnetic Cyclotron Waves in the Solar Wind: Wind Observation and Wave Dispersion Analysis

    Science.gov (United States)

    Jian, L. K.; Moya, P. S.; Vinas, A. F.; Stevens, M.

    2016-01-01

    Wind observed long-lasting electromagnetic cyclotron waves near the proton cyclotron frequency on 11 March 2005, in the descending part of a fast wind stream. Bi-Maxwellian velocity distributions are fitted for core protons, beam protons, and alpha-particles. Using the fitted plasma parameters we conduct kinetic linear dispersion analysis and find ion cyclotron and/or firehose instabilities grow in six of 10 wave intervals. After Doppler shift, some of the waves have frequency and polarization consistent with observation, thus may be correspondence to the cyclotron waves observed.

  15. Ocean Surface Wind Speed of Hurricane Helene Observed by SAR

    DEFF Research Database (Denmark)

    Xu, Qing; Cheng, Yongcun; Li, Xiaofeng

    2011-01-01

    The hurricanes can be detected by many remote sensors, but synthetic aperture radar (SAR) can yield high-resolution (sub-kilometer) and low-level wind information that cannot be seen below the cloud by other sensors. In this paper, an assessment of SAR capability of monitoring high-resolution hur......The hurricanes can be detected by many remote sensors, but synthetic aperture radar (SAR) can yield high-resolution (sub-kilometer) and low-level wind information that cannot be seen below the cloud by other sensors. In this paper, an assessment of SAR capability of monitoring high......-resolution hurricane was conducted. A case study was carried out to retrieve ocean surface wind field from C-band RADARSAT-1 SAR image which captured the structure of hurricane Helene over the Atlantic Ocean on 20 September, 2006. With wind direction from the outputs of U.S. Navy Operational Global Atmospheric...... Prediction System (NOGAPS) model, C-band geophysical model functions (GMFs) which describe the normalized radar cross section (NRCS) dependence on the wind speed and the geometry of radar observations (i.e., incidence angle and azimuth angle with respect to wind direction) such as CMOD5 and newly developed...

  16. XMM-Newton Observations of Solar Wind Charge Exchange Emission

    Science.gov (United States)

    Snowden, S. L.; Collier, M. R.; Kuntz, K. D.

    2004-01-01

    We present an XMM-Newton spectrum of diffuse X-ray emission from within the solar system. The spectrum is dominated by O VII and O VIII lines at 0.57 keV and 0.65 keV, O VIII (and possibly Fe XVII) lines at approximately 0.8 keV, Ne IX lines at approximately 0.92 keV, and Mg XI lines at approximately 1.35 keV. This spectrum is consistent with what is expected from charge exchange emission between the highly ionized solar wind and either interstellar neutrals in the heliosphere or material from Earth's exosphere. The emission is clearly seen as a low-energy ( E less than 1.5 keV) spectral enhancement in one of a series of observations of the Hubble Deep Field North. The X-ray enhancement is concurrent with an enhancement in the solar wind measured by the ACE satellite. The solar wind enhancement reaches a flux level an order of magnitude more intense than typical fluxes at 1 AU, and has ion ratios with significantly enhanced higher ionization states. Whereas observations of the solar wind plasma made at a single point reflect only local conditions which may only be representative of solar wind properties with spatial scales ranging from less than half of an Earth radii (approximately 10 s) to 100 Earth radii, X-ray observations of solar wind charge exchange are remote sensing measurements which may provide observations which are significantly more global in character. Besides being of interest in its own right for studies of the solar system, this emission can have significant consequences for observations of more cosmological objects. It can provide emission lines at zero redshift which are of particular interest (e.g., O VII and O VIII) in studies of diffuse thermal emission, and which can therefore act as contamination in objects which cover the entire detector field of view. We propose the use of solar wind monitoring data, such as from the ACE and Wind spacecraft, as a diagnostic to screen for such possibilities.

  17. An Examination of the Quality of Wind Observations with Smartphones

    Science.gov (United States)

    Hintz, Kasper; Vedel, Henrik; Muñoz-Gomez, Juan; Woetmann, Niels

    2017-04-01

    Over the last years, the number of devices connected to the internet has increased significantly making it possible for internal and external sensors to communicate via the internet, opening up many possibilities for additional data for use in the atmospheric sciences. Vaavud has manufactured small anemometer devices which can measure wind speed and wind direction when connected to a smartphone. This work examines the quality of such crowdsourced Handheld Wind Observations (HWO). In order to examine the quality of the HWO, multiple idealised measurement sessions were performed at different sites in different atmospheric conditions. In these sessions, a high-precision ultrasonic anemometer was installed to work as a reference measurement. The HWO are extrapolated to 10 m in order to compare these to the reference observations. This allows us to examine the effect of stability correction in the surface layer and the quality of height extrapolated HWO. The height extrapolation is done using the logarithmic wind profile law with and without stability correction. Furthermore, this study examines the optimal ways of using traditional observations and numerical models to validate HWO. In order to do so, a series of numerical reanalysis have been run for a period of 5 months to quantise the effect of including crowdsourced HWO in a traditional observation dataset.

  18. Winds observed in the Northern European seas with wind lidars, meteorological masts and satellite

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Stein, D.; Peña, Alfredo

    2013-01-01

    of them for up to two years when the project campaign ended. The NORSEWInD database on lidar data in total contains around 11 years worth of observations (> 280.000 10 min data). The wind lidars were mounted such that winds were mapped at or very near 100 m above sea level. The lidars provide wind profile...... the thermal effects on the wind profile. In conclusion, the parameters that influence the vertical wind profiles are found to be stability, surface roughness – the sea has changing roughness due to wind-wave interactions - , and boundary layer height, in this order of importance. However, it may be noted...... of overlapping SAR scenes varied from a few hundred to more than 1,400 in the study area. For QuikSCAT and ASCAT the available number of overlapping scenes is around 7000 and 600, respectively. The results are publically available in digital form from GIS, free of charge, through a link at www...

  19. Differential flow between solar wind protons and alpha particles: First WIND observations

    Science.gov (United States)

    Steinberg, J. T.; Lazarus, A. J.; Ogilvie, K. W.; Lepping, R.; Byrnes, J.

    Alpha particle and proton measurements in the solar wind made using the SWE Faraday cup detectors on the WIND spacecraft are reported. Some overall trends observed confirm past observations: the ratios of alpha particle to proton density Nα/NP, thermal speed Wα/WP, as well as the differential velocity Vα-VP (hereafter VαP) are generally correlated with bulk solar wind flow speed. The detailed WIND measurements enable us to investigate instances when the alpha-proton differences deviate from these overall general trends. Occasionally, difference velocities as large as 80 km/s were seen, with the ratio of |VαP| to the Alfvén speed VA near unity, characteristics more typical of observations at solar distances less than 1 AU. An example is presented where |Vα|-|VP| reverses sign while |VαP| stays nearly constant. Comparison of the vector velocities and the magnetic field suggests that the speed reversal is associated with a localized kink in the magnetic field. Finally we show an instance where |VαP| exceeds the observed wave speed for Alfvénic fluctuations (Vwave=B0ΔV/ΔB) resulting in alpha particle velocity fluctuations that anti-correlate with the wave. Though this phenomenon has been previously reported in high-latitude measurements beyond 1 AU, it is shown here to also occur at 1 AU in the ecliptic.

  20. Wind observations of low energy particles within a solar wind reconnection region

    Directory of Open Access Journals (Sweden)

    K. E. J. Huttunen

    2008-09-01

    Full Text Available We report characteristics of thermal particle observations during the encounter of the Wind satellite with the separatrix and the outflow domains of a reconnection event on 22 July 1999 in the solar wind. During the studied event the electrostatic analyzers on Wind were transmitting three-dimensional electron and proton distributions in a burst mode every 3 s, the spin period of the spacecraft. The event was associated with a magnetic shear angle of 114° and a large guide magnetic field. The observations suggest that Wind crossed the separatrix and outflow regions about a thousand of ion skin depths from the X-line. At the leading separator boundary, a strong proton beam was identified that originated from the direction of the X-line. In the separatrix and the outflow regions, the phase space distributions of thermal electrons displayed field aligned bidirectional anisotropy. During the crossings of the current sheets bounding the outflow region, we identified two adjacent layers in which the dominant thermal electron flows were towards the X-line at the inner edges of the current sheets and away from the X-line at the outer edges. Interestingly, simulation studies and observations in the Earth's magnetosphere have revealed that the electron flows are reversed, consistent with the Hall current system.

  1. Wind observations of low energy particles within a solar wind reconnection region

    Directory of Open Access Journals (Sweden)

    K. E. J. Huttunen

    2008-09-01

    Full Text Available We report characteristics of thermal particle observations during the encounter of the Wind satellite with the separatrix and the outflow domains of a reconnection event on 22 July 1999 in the solar wind. During the studied event the electrostatic analyzers on Wind were transmitting three-dimensional electron and proton distributions in a burst mode every 3 s, the spin period of the spacecraft. The event was associated with a magnetic shear angle of 114° and a large guide magnetic field. The observations suggest that Wind crossed the separatrix and outflow regions about a thousand of ion skin depths from the X-line. At the leading separator boundary, a strong proton beam was identified that originated from the direction of the X-line. In the separatrix and the outflow regions, the phase space distributions of thermal electrons displayed field aligned bidirectional anisotropy. During the crossings of the current sheets bounding the outflow region, we identified two adjacent layers in which the dominant thermal electron flows were towards the X-line at the inner edges of the current sheets and away from the X-line at the outer edges. Interestingly, simulation studies and observations in the Earth's magnetosphere have revealed that the electron flows are reversed, consistent with the Hall current system.

  2. Kinetic Theory and Fast Wind Observations of the Electron Strahl

    Science.gov (United States)

    Horaites, Konstantinos; Boldyrev, Stanislav; Wilson, Lynn B., III; Viñas, Adolfo F.; Merka, Jan

    2018-02-01

    We develop a model for the strahl population in the solar wind - a narrow, low-density and high-energy electron beam centred on the magnetic field direction. Our model is based on the solution of the electron drift-kinetic equation at heliospheric distances where the plasma density, temperature and the magnetic field strength decline as power laws of the distance along a magnetic flux tube. Our solution for the strahl depends on a number of parameters that, in the absence of the analytic solution for the full electron velocity distribution function (eVDF), cannot be derived from the theory. We however demonstrate that these parameters can be efficiently found from matching our solution with observations of the eVDF made by the Wind satellite's SWE strahl detector. The model is successful at predicting the angular width (FWHM) of the strahl for the Wind data at 1 au, in particular by predicting how this width scales with particle energy and background density. We find that the strahl distribution is largely determined by the local temperature Knudsen number γ ∼ |T dT/dx|/n, which parametrizes solar wind collisionality. We compute averaged strahl distributions for typical Knudsen numbers observed in the solar wind, and fit our model to these data. The model can be matched quite closely to the eVDFs at 1 au; however, it then overestimates the strahl amplitude at larger heliocentric distances. This indicates that our model may be improved through the inclusion of additional physics, possibly through the introduction of 'anomalous diffusion' of the strahl electrons.

  3. Wind-driven marine phytoplank blooms: Satellite observation and analysis

    Science.gov (United States)

    Tang, DanLing

    2016-07-01

    Algal bloom is defined as a rapid increase or accumulation in biomass in an aquatic system. It not only can increase the primary production but also could result in negative ecological consequence, e.g.,Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actuallythe traditional observation is only sporadic capture to the existence of algal blooms.Taking full advantage of multiple data of satellite remote sensing , this study introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; (2)Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. (3)Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. The proposed "wind-pump" mechanism integrates theoretical system combined "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. These

  4. Observations of the trade wind wakes of Kauai and Oahu

    Science.gov (United States)

    Yang, Yang; Ma, Jian; Xie, Shang-Ping

    2008-02-01

    The Hawaiian islands of Kauai and Oahu stand in the path of the east-northeasterly trade winds, creating wakes in the lee. For the first time, the structure of the wakes and their diurnal cycle were observed on a cruise during 18-20 December 2006. The dynamic wakes, characterized by reduced trades, extend about 1 km in height with strong wind shear at the top. Thermal forcing of these small islands also affects the wake circulations. Sea breezes develop in the afternoon turning the winds into westerly near the shore in the wakes. At night, land breezes advect cool air from the islands, creating a shallow cool layer between the sea surface and a capping inversion. The warming in the wake in the afternoon extends much deeper (1.4 km) than the cool layer (0.5 km) at night. The effect of diurnal changes on cloud formation in the wakes is discussed, and the sharp variations in wind velocity lee of the islands may affect ocean currents, waves and mixing.

  5. Victoria Ocampo and Alfonso Reyes: Ulysses's Malady

    Directory of Open Access Journals (Sweden)

    Doris Meyer

    2000-06-01

    Full Text Available Ocampo (Argentina, 1890-1979 and Reyes (Mexico, 1889-1959 were arguably Latin America's most influential writers and cultural catalysts in the first half of the twentieth century. They met in Argentina in 1927 and their friendship and correspondence lasted until Reyes's death. Over three decades of private and public discourse, they articulated a similar vision of Latin American identity and its future potential. Because they were both internationally known—Ocampo as founder and director of the literary review SUR, and Reyes as a diplomat and intellectual leader—their ideas found resonance in the Americas and Europe. Two dramatic works they wrote before meeting, Ifigenia cruel (Reyes and La laguna de los nenúfares (Ocampo, prefigure their approach to the Latin American condition through the themes of displacement and self-renovation. Ocampo and Reyes believed that it would be the task of an educated elite to lead Latin America toward a transnational cultural synthesis and renewal. Ulysses's malady was their metaphor for the postcolonial condition that enabled Latin American minds to be open to exploration and dialogue in search of an authentic identity.

  6. Characterization of high-altitude winds from infrasound observations

    Science.gov (United States)

    Lalande, J.; Le Pichon, A.; Blanc, E.; Assink, J. D.; Waxler, R.; Blanc-Benon, P.; Sèbe, O.; Landes, M.

    2012-12-01

    Infrasonic waves in the frequency band 0.01-4 Hz are continuously recorded by the International Monitoring System (IMS) designed for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). These waves propagate at long-ranges through atmospheric ducts resulting from the natural stratification of atmospheric properties (temperature, density, winds, ...) and represent a valuable information to understand atmospheric dynamic until the lower thermosphere. Our research focuses on determining the potential of infrasound observations to improve atmospheric specifications. We develop an inverse algorithm in order to estimate atmospheric parameters from infrasonic observations. The forward problem is handled by a ray-tracing algorithm. First-order perturbation equation resulting from perturbation of atmospheric properties, and especially wind parameters, are developped and numerically validated. We then analyse the inverse problem through several numerical experiments in order to show the capabilities and limitations of our algorithm. Results show the suitability of our approach and indicate that infrasonic observations can significantly improve current atmospheric specification at the altitudes of acoustic energy refraction, i.e. around 50 km and between 100 and 120 km. Performances and limitations of infrasound atmospheric sounding methods are finally discussed in details.

  7. Assimilation of wind speed and direction observations: results from real observation experiments

    Directory of Open Access Journals (Sweden)

    Feng Gao

    2015-06-01

    Full Text Available The assimilation of wind observations in the form of speed and direction (asm_sd by the Weather Research and Forecasting Model Data Assimilation System (WRFDA was performed using real data and employing a series of cycling assimilation experiments for a 2-week period, as a follow-up for an idealised post hoc assimilation experiment. The satellite-derived Atmospheric Motion Vectors (AMV and surface dataset in Meteorological Assimilation Data Ingest System (MADIS were assimilated. This new method takes into account the observation errors of both wind speed (spd and direction (dir, and WRFDA background quality control (BKG-QC influences the choice of wind observations, due to data conversions between (u,v and (spd, dir. The impacts of BKG-QC, as well as the new method, on the wind analysis were analysed separately. Because the dir observational errors produced by different platforms are not known or tuned well in WRFDA, a practical method, which uses similar assimilation weights in comparative trials, was employed to estimate the spd and dir observation errors. The asm_sd produces positive impacts on analyses and short-range forecasts of spd and dir with smaller root-mean-square errors than the u,v-based system. The bias of spd analysis decreases by 54.8%. These improvements result partly from BKG-QC screening of spd and dir observations in a direct way, but mainly from the independent impact of spd (dir data assimilation on spd (dir analysis, which is the primary distinction from the standard WRFDA method. The potential impacts of asm_sd on precipitation forecasts were evaluated. Results demonstrate that the asm_sd is able to indirectly improve the precipitation forecasts by improving the prediction accuracies of key wind-related factors leading to precipitation (e.g. warm moist advection and frontogenesis.

  8. Wind Atlas for South Africa (WASA) Observational wind atlas for 10 met. stations in Northern, Western and Eastern Cape provinces

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Hansen, Jens Carsten; Kelly, Mark C.

    Program (WAsP 11). The wind-climatological inputs are the observed wind climates derived from the WAsP Climate Analyst. Topographical inputs are elevation maps constructed from SRTM 3 data and roughness length maps constructed from SWBD data and Google Earth satellite imagery. Summaries are given...

  9. Recent progress in astrophysical plasma turbulence from solar wind observations

    CERN Document Server

    Chen, C H K

    2016-01-01

    This paper summarises some of the recent progress that has been made in understanding astrophysical plasma turbulence in the solar wind, from in situ spacecraft observations. At large scales, where the turbulence is predominantly Alfvenic, measurements of critical balance, residual energy, and 3D structure are discussed, along with comparison to recent models of strong Alfvenic turbulence. At these scales, a few percent of the energy is also in compressive fluctuations, and their nature, anisotropy, and relation to the Alfvenic component is described. In the small scale kinetic range, below the ion gyroscale, the turbulence becomes predominantly kinetic Alfven in nature, and measurements of the spectra, anisotropy, and intermittency of this turbulence are discussed with respect to recent cascade models. One of the major remaining questions is how the turbulent energy is dissipated, and some recent work on this question, in addition to future space missions which will help to answer it, are briefly discussed.

  10. Designing a torque-less wind shield for broadband observation of marsquakes

    Science.gov (United States)

    Nishikawa, Y.; Araya, A.; Kurita, K.; Kobayashi, N.; Kawamura, T.

    2014-12-01

    To perform seismic observations on Mars, reduction of the surface wind effect is necessary. In particular, ground tilt causes a serious problem for broadband seismic observations. Ground tilt is a seismic noise source, and it can be attributed to the torque of the wind shield. The torque brings about a difference in ground strain. Here, we report on an optimized torque-less wind shield to protect a seismometer from the wind, the design method, and an evaluation method for the background noise level. We have conducted wind tunnel tests and numerical simulations with several types of designs and obtained an effective shape to minimize the torque from the wind. The designed torque-less wind shield has lower ground tilt noise than typical-shape wind shields by one order of magnitude. This will enable us to achieve a more than 90% noise-free condition during an observation span, even for the most windy conditions on the Martian surface.

  11. SAR Observation and Modeling of Gap Winds in the Prince William Sound of Alaska

    Directory of Open Access Journals (Sweden)

    Karl Volz

    2008-08-01

    Full Text Available Alaska’s Prince William Sound (PWS is a unique locale tending to have strong gap winds, especially in the winter season. To characterize and understand these strong surface winds, which have great impacts on the local marine and aviation activities, the surface wind retrieval from the Synthetic Aperture Radar data (SAR-wind is combined with a numerical mesoscale model. Helped with the SAR-wind observations, the mesoscale model is used to study cases of strong winds and relatively weak winds to depict the nature of these winds, including the area of extent and possible causes of the wind regimes. The gap winds from the Wells Passage and the Valdez Arm are the most dominant gap winds in PWS. Though the Valdez Arm is north-south trending and Wells Passage is east-west oriented, gap winds often develop simultaneously in these two places when a low pressure system is present in the Northern Gulf of Alaska. These two gap winds often converge at the center of PWS and extend further out of the Sound through the Hinchinbrook Entrance. The pressure gradients imposed over these areas are the main driving forces for these gap winds. Additionally, the drainage from the upper stream glaciers and the blocking effect of the banks of the Valdez Arm probably play an important role in enhancing the gap wind.

  12. Wind profiler observations of a monsoon low-level jet over a tropical Indian station

    Directory of Open Access Journals (Sweden)

    M. C. R. Kalapureddy

    2007-11-01

    Full Text Available Three-year high-resolution wind observations of the wind profiler have been utilized to characterize the diurnal and seasonal features of the monsoon Low-Level Jet (LLJ over a tropical station, Gadanki (13.5° N, 79.2° E, with a focus on the diurnal variability of low-level winds. The Boreal summer monsoon winds show a conspicuously strong westerly LLJ with average wind speed exceeding 20 m s−1. The L-band wind profiler measurements have shown an advantage of better height and time resolutions over the conventional radiosonde method for diurnal wind measurements. An interesting diurnal oscillation of LLJ core has been observed. It is varying in the height range of 1.8±0.6 km with the maximum and minimum intensity noticed during the early morning and afternoon hours, respectively. The jet core (wind maxima height is observed to coincide with the inversion height. Strong wind shears are normally located beneath the LLJ core. The sole wind profiler observations are capable of identifying the monsoon phases, such as onset, break and active spells, etc. The mutual influence between the LLJ and the boundary layer has been discussed. One notices that the observed LLJ diurnal structures depend on the local convective activity, wind shears and turbulence activity associated with boundary layer winds. The day-to-day change in the LLJ structure depends on the latitudinal position of the LLJ core.

  13. Evaluation of satellite and reanalysis wind products with in situ wave glider wind observations in the Southern Ocean

    CSIR Research Space (South Africa)

    Schmidt, KM

    2017-12-01

    Full Text Available Wave Glider (WG) deployments in the Southern Ocean with the intent to determine which blended satellite or reanalysis product best represents the magnitude and variability of the observed wind field. Results show that the ECMWF reanalysis product...

  14. Self-consistent Castaing distribution of solar wind turbulent fluctuations

    CERN Document Server

    Sorriso-Valvo, L; Lijoi, L; Perri, S; Carbone, V

    2015-01-01

    The intermittent behavior of solar wind turbulent fluctuations has often been investigated through the modeling of their probability distribution functions (PDFs). Among others, the Castaing model (Castaing et al. 1990) has successfully been used in the past. In this paper, the energy dissipation field of solar wind turbulence has been studied for fast, slow and polar wind samples recorded by Helios 2 and Ulysses spacecraft. The statistical description of the dissipation rate has then be used to remove intermittency through conditioning of the PDFs. Based on such observation, a self-consistent, parameter-free Castaing model is presented. The self-consistent model is tested against experimental PDFs, showing good agreement and supporting the picture of a multifractal energy cascade at the origin of solar wind intermittency.

  15. Improved observations of turbulence dissipation rates from wind profiling radars

    Directory of Open Access Journals (Sweden)

    K. McCaffrey

    2017-07-01

    Full Text Available Observations of turbulence dissipation rates in the planetary boundary layer are crucial for validation of parameterizations in numerical weather prediction models. However, because dissipation rates are difficult to obtain, they are infrequently measured through the depth of the boundary layer. For this reason, demonstrating the ability of commonly used wind profiling radars (WPRs to estimate this quantity would be greatly beneficial. During the XPIA field campaign at the Boulder Atmospheric Observatory, two WPRs operated in an optimized configuration, using high spectral resolution for increased accuracy of Doppler spectral width, specifically chosen to estimate turbulence from a vertically pointing beam. Multiple post-processing techniques, including different numbers of spectral averages and peak processing algorithms for calculating spectral moments, were evaluated to determine the most accurate procedures for estimating turbulence dissipation rates using the information contained in the Doppler spectral width, using sonic anemometers mounted on a 300 m tower for validation. The optimal settings were determined, producing a low bias, which was later corrected. Resulting estimations of turbulence dissipation rates correlated well (R2 = 0. 54 and 0. 41 with the sonic anemometers, and profiles up to 2 km from the 449 MHz WPR and 1 km from the 915 MHz WPR were observed.

  16. The magnetic field investigation on the Ulysses mission - Instrumentation and preliminary scientific results

    Science.gov (United States)

    Balogh, A.; Beek, T. J.; Forsyth, R. J.; Hedgecock, P. C.; Marquedant, R. J.; Smith, E. J.; Southwood, D. J.; Tsurutani, B. T.

    1992-01-01

    A fundamental feature of the heliosphere is the three-dimensional structure of the interplanetary magnetic field. The magnetic field investigation on Ulysses, the first space probe to explore the out-of-ecliptic and polar heliosphere, aims at determining the large-scale features and gradients of the field, as well as the heliolatitude dependence of interplanetary phenomena so far only observed near the ecliptic plane. The Ulysses magnetometer uses two sensors, one a Vector Helium Magnetometer, the other a Fluxgate Magnetometer. Onboard data processing yields measurements of the magnetic field vector with a time resolution up to 2 vectors/second and a sensitivity of about 10 pT. Since the switch-on of the instrument in flight on 25 October 1990, a steady stream of observations has been made, indicating that at this phase of the solar cycle the field is generally disturbed: several shock waves and a large number of discontinuities have been observed, as well as several periods with apparently intense wave activity. The paper gives a brief summary of the scientific objectives of the investigation, followed by a detailed description of the instrument and its characteristics. Examples of wave bursts, interplanetary shocks and crossings of the heliospheric current sheet are given to illustrate the observations made with the instrument.

  17. FPI observations of nighttime mesospheric and thermospheric winds in China and their comparisons with HWM07

    Directory of Open Access Journals (Sweden)

    W. Yuan

    2013-08-01

    Full Text Available We analyzed the nighttime horizontal neutral winds in the middle atmosphere (~ 87 and ~ 98 km and thermosphere (~ 250 km derived from a Fabry–Perot interferometer (FPI, which was installed at Xinglong station (40.2° N, 117.4° E in central China. The wind data covered the period from April 2010 to July 2012. We studied the annual, semiannual and terannual variations of the midnight winds at ~ 87 km, ~ 98 km and ~ 250 km for the first time and compared them with Horizontal Wind Model 2007 (HWM07. Our results show the following: (1 at ~ 87 km, both the observed and model zonal winds have similar phases in the annual and semiannual variations. However, the HWM07 amplitudes are much larger. (2 At ~ 98 km, the model shows strong eastward wind in the summer solstice, resulting in a large annual variation, while the observed strongest component is semiannual. The observation and model midnight meridional winds agree well. Both are equatorward throughout the year and have small amplitudes in the annual and semiannual variations. (3 There are large discrepancies between the observed and HWM07 winds at ~ 250 km. This discrepancy is largely due to the strong semiannual zonal wind in the model and the phase difference in the annual variation of the meridional wind. The FPI annual variation coincides with the results from Arecibo, which has similar geomagnetic latitude as Xinglong station. In General, the consistency of FPI winds with model winds is better at ~ 87 and ~ 98 km than that at ~ 250 km. We also studied the seasonally and monthly averaged nighttime winds. The most salient features include the following: (1 the seasonally averaged zonal winds at ~ 87 and ~ 98 km typically have small variations throughout the night. (2 The model zonal and meridional nighttime wind variations are typically much larger than those of observations at ~ 87 km and ~ 98 km. (3 At ~ 250 km, model zonal wind compares well with the observation in the winter. For spring and

  18. THE NEW HORIZONS SOLAR WIND AROUND PLUTO (SWAP) OBSERVATIONS OF THE SOLAR WIND FROM 11–33 au

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, H. A.; McComas, D. J.; Valek, P.; Weidner, S.; Livadiotis, G. [Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238 (United States); Nicolaou, G., E-mail: helliott@swri.edu [Swedish Institute of Space Physics, Box 812, SE-98128, Kiruna (Sweden)

    2016-04-15

    The Solar Wind Around Pluto (SWAP) instrument on National Aeronautics and Space Administration's New Horizons Pluto mission has collected solar wind observations en route from Earth to Pluto, and these observations continue beyond Pluto. Few missions have explored the solar wind in the outer heliosphere making this dataset a critical addition to the field. We created a forward model of SWAP count rates, which includes a comprehensive instrument response function based on laboratory and flight calibrations. By fitting the count rates with this model, the proton density (n), speed (V), and temperature (T) parameters are determined. Comparisons between SWAP parameters and both propagated 1 au observations and prior Voyager 2 observations indicate consistency in both the range and mean wind values. These comparisons as well as our additional findings confirm that small and midsized solar wind structures are worn down with increasing distance due to dynamic interaction of parcels of wind with different speed. For instance, the T–V relationship steepens, as the range in V is limited more than the range in T with distance. At times the T–V correlation clearly breaks down beyond 20 au, which may indicate wind currently expanding and cooling may have an elevated T reflecting prior heating and compression in the inner heliosphere. The power of wind parameters at shorter periodicities decreases with distance as the longer periodicities strengthen. The solar rotation periodicity is present in temperature beyond 20 au indicating the observed parcel temperature may reflect not only current heating or cooling, but also heating occurring closer to the Sun.

  19. Lidar observations of marine boundary-layer winds and heights: a preliminary study

    DEFF Research Database (Denmark)

    Peña, Alfredo; Gryning, Sven-Erik; Floors, Rogier Ralph

    2015-01-01

    Here we describe a nearly 1-yr meteorological campaign, which was carried out at the FINO3 marine research platform on the German North Sea, where a pulsed wind lidar and a ceilometer were installed besides the platform's 105-m tower and measured winds and the aerosol backscatter in the entire...... marine atmospheric boundary layer. The campaign was the last phase of a research project, in which the vertical wind profile in the atmospheric boundary layer was firstly investigated on a coastal and a semi-urban site. At FINO3 the wind lidar, which measures the wind speed up to 2000 m, shows...... the highest data availability (among the three sites) and a very good agreement with the observations of wind speed and direction from cup anemometers and vanes from the platform's tower. The wind lidar was also able to perform measurements under a winter storm where 10-s gusts were observed above 60 m s 1...

  20. ERWIN-2: Wind Observations and Comparisons with Meteor Radar at Eureka.

    Science.gov (United States)

    Kristoffersen, Samuel; Brown, Stephen; Ward, William E.; Manson, Alan; Meek, Chris

    EWIN-2 (E-Region Wind Interferometer) is a field-widened Michelson interferometer that is used to measure winds in the mesopause (90 km). ERWIN-2 measures Doppler shifts in the hydroxyl, green-line, and O2 airglow emissions to determine the winds. A quad mirror in the optical system allows for simultaneous measurement of five viewing directions. This results in an observation cadence of 2 minutes for all three emissions at a precision of 5 m/s thereby making ERWIN-2 the fastest wind measuring instrument in the world for the mesopause region. Instrument operation, wind observations from January 2009, discussions of zero-wind calibra-tion and vertical wind determination and comparisons with meteor radar, used to validate ERWIN-2 operation and determine emission layer heights, will be presented.

  1. Wind modulation of upwelling at the shelf-break front off Patagonia: Observational evidence

    Science.gov (United States)

    Carranza, M. M.; Gille, S. T.; Piola, A. R.; Charo, M.; Romero, S. I.

    2017-03-01

    The South-Atlantic Patagonian shelf is the largest chlorophyll-a (Chl-a) hot spot in Southern Ocean color images. While a persistent 1500 km long band of high Chl-a along the shelf-break front (SBF) is indicative of upwelling, the mechanisms that drive it are not entirely known. Along-front wind oscillations can enhance upwelling and provide a nutrient pumping mechanism at shelf-break fronts of western boundary currents. Here we assess wind-induced upwelling at the SBF off Patagonia from daily satellite Chl-a and winds, historical hydrographic observations, cross-shelf Chl-a fluorescence transects from two cruises, and in situ winds and water column structure from a mooring site. Satellite Chl-a composites segregated by along-front wind direction indicate that surface Chl-a is enhanced at the SBF with southerly winds and suppressed with northerly winds. Northerly winds also result in enhanced Chl-a further offshore (˜25-50 km). Synoptic transects as well as mean hydrographic sections segregated by along-front winds show isopycnals tilted upward for southerly winds. Spring observations from the mooring also suggest that southerly winds destratify the water column and northerly winds restratify, in agreement with Ekman transport interacting with the front. Moreover, changes in water column temperature lag along-front wind forcing by 2-4 days. Our results suggest that oscillations in along-front winds, on timescales typical of atmospheric storms (2-10 days), can significantly modulate the upwelling and Chl-a concentrations at the SBF off Patagonia, revealing the importance of wind-induced upwelling for shelf-slope exchange at shelf-break fronts of western boundary currents.

  2. Comparing offshore wind farm wake observed from satellite SAR and wake model results

    Science.gov (United States)

    Bay Hasager, Charlotte

    2014-05-01

    Offshore winds can be observed from satellite synthetic aperture radar (SAR). In the FP7 EERA DTOC project, the European Energy Research Alliance project on Design Tools for Offshore Wind Farm Clusters, there is focus on mid- to far-field wind farm wakes. The more wind farms are constructed nearby other wind farms, the more is the potential loss in annual energy production in all neighboring wind farms due to wind farm cluster effects. It is of course dependent upon the prevailing wind directions and wind speed levels, the distance between the wind farms, the wind turbine sizes and spacing. Some knowledge is available within wind farm arrays and in the near-field from various investigations. There are 58 offshore wind farms in the Northern European seas grid connected and in operation. Several of those are spaced near each other. There are several twin wind farms in operation including Nysted-1 and Rødsand-2 in the Baltic Sea, and Horns Rev 1 and Horns Rev 2, Egmond aan Zee and Prinses Amalia, and Thompton 1 and Thompton 2 all in the North Sea. There are ambitious plans of constructing numerous wind farms - great clusters of offshore wind farms. Current investigation of offshore wind farms includes mapping from high-resolution satellite SAR of several of the offshore wind farms in operation in the North Sea. Around 20 images with wind farm wake cases have been retrieved and processed. The data are from the Canadian RADARSAT-1/-2 satellites. These observe in microwave C-band and have been used for ocean surface wind retrieval during several years. The satellite wind maps are valid at 10 m above sea level. The wakes are identified in the raw images as darker areas downwind of the wind farms. In the SAR-based wind maps the wake deficit is found as areas of lower winds downwind of the wind farms compared to parallel undisturbed flow in the flow direction. The wind direction is clearly visible from lee effects and wind streaks in the images. The wind farm wake cases

  3. Observing Boundary-Layer Winds from Hot-Air Balloon Flights

    NARCIS (Netherlands)

    Bruijn, de E.I.F.; Haan, de S.; Bosveld, F.C.; Wichers Schreur, B.G.J.; Holtslag, A.A.M.

    2016-01-01

    High-resolution upper-air wind observations are sparse, and additional observations are a welcome source of meteorological information. In this paper the potential of applying balloon flights for upper-air wind measurements is explored, and the meteorological content of this information is

  4. Solar wind modulation of the Martian ionosphere observed by Mars Global Surveyor

    Directory of Open Access Journals (Sweden)

    J.-S. Wang

    2004-06-01

    Full Text Available Electron density profiles in the Martian ionosphere observed by the radio occultation experiment on board Mars Global Surveyor have been analyzed to determine if the densities are influenced by the solar wind. Evidence is presented that the altitude of the maximum ionospheric electron density shows a positive correlation to the energetic proton flux in the solar wind. The solar wind modulation of the Martian ionosphere can be attributed to heating of the neutral atmosphere by the solar wind energetic proton precipitation. The modulation is observed to be most prominent at high solar zenith angles. It is argued that this is consistent with the proposed modulation mechanism.

  5. Distribution and solar wind control of compressional solar wind-magnetic anomaly interactions observed at the Moon by ARTEMIS

    Science.gov (United States)

    Halekas, J. S.; Poppe, A. R.; Lue, C.; Farrell, W. M.; McFadden, J. P.

    2017-06-01

    A statistical investigation of 5 years of observations from the two-probe Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) mission reveals that strong compressional interactions occur infrequently at high altitudes near the ecliptic but can form in a wide range of solar wind conditions and can occur up to two lunar radii downstream from the lunar limb. The compressional events, some of which may represent small-scale collisionless shocks ("limb shocks"), occur in both steady and variable interplanetary magnetic field (IMF) conditions, with those forming in steady IMF well organized by the location of lunar remanent crustal magnetization. The events observed by ARTEMIS have similarities to ion foreshock phenomena, and those observed in variable IMF conditions may result from either local lunar interactions or distant terrestrial foreshock interactions. Observed velocity deflections associated with compressional events are always outward from the lunar wake, regardless of location and solar wind conditions. However, events for which the observed velocity deflection is parallel to the upstream motional electric field form in distinctly different solar wind conditions and locations than events with antiparallel deflections. Consideration of the momentum transfer between incoming and reflected solar wind populations helps explain the observed characteristics of the different groups of events.Plain Language SummaryWe survey the environment around the Moon to determine when and where strong amplifications in the charged particle density and magnetic field strength occur. These structures may be some of the smallest shock waves in the solar system, and learning about their formation informs us about the interaction of charged particles with small-scale magnetic fields throughout the solar system and beyond. We find that these compressions occur in an extended region downstream from the lunar dawn and dusk regions and

  6. On a magnetosphere disturbed by solar wind; observations of macroelectrons

    Directory of Open Access Journals (Sweden)

    E. B. Wodnicka

    2009-06-01

    Full Text Available Three-dimensional electromagnetic full kinetic particle code (a version of TRISTAN is used to study the interaction of a weakly-magnetized object with a solar wind of low density. The details of two magnetospheric processes – wave activity and energetic electrons appearing at the flanks of the magnetosphere – are presented. The results of the simulation are compared with known magnetospheric data.

  7. How measurement uncertainties impact upon the observed scaling properties of MHD turbulence in the solar wind

    Science.gov (United States)

    Hnat, B.; Gogoberidze, G.; Chapman, S. C.; Dunlop, M.

    2012-12-01

    Quantifying the scaling exponents of fluctuations in the solar wind is central to testing predictions of turbulence theories. We study spectral features of Alfvenic turbulence in fast solar wind. We propose a general, instrument independent method (Gogoberidze et al, MNRAS, 2012) to estimate the uncertainty in velocity fluctuations obtained by in-situ satellite observations in the solar wind. We show that when the measurement uncertainties of the velocity fluctuations are taken into account the less energetic Elsasser spectrum obeys a unique power law scaling throughout the inertial range as prevailing theories of magnetohydrodynamic turbulence predict. Moreover, in the solar wind interval analyzed, the two Elsasser spectra are observed to have the same scaling exponent ~1:54 throughout the inertial range. This highlights the importance of understanding uncertainty estimates and how they affect observed scaling in the PSD when using the solar wind as a laboratory to test predictions of theories of turbulence.

  8. Wind Atlas for South Africa (WASA) Observational wind atlas for 10 met. stations in Northern, Western and Eastern Cape provinces

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Hansen, Jens Carsten; Kelly, Mark C.

    Program (WAsP 11). The windclimatological inputs are the observed wind climates derived from the WAsP Climate Analyst. Topographical inputs are elevation maps constructed from SRTM 3 data and rough-ness length maps constructed from SWBD data and Google Earth satellite imagery. Summaries are given...

  9. Wind estimation around the shipwreck of Oriental Star based on field damage surveys and radar observations.

    Science.gov (United States)

    Meng, Zhiyong; Yao, Dan; Bai, Lanqiang; Zheng, Yongguang; Xue, Ming; Zhang, Xiaoling; Zhao, Kun; Tian, Fuyou; Wang, Mingjun

    Based on observational analyses and on-site ground and aerial damage surveys, this work aims to reveal the weather phenomena-especially the wind situation-when Oriental Star capsized in the Yangtze River on June 1, 2015. Results demonstrate that the cruise ship capsized when it encountered strong winds at speeds of at least 31 m s-1 near the apex of a bow echo embedded in a squall line. As suggested by the fallen trees within a 2-km radius around the wreck location, such strong winds were likely caused by microburst straight-line wind and/or embedded small vortices, rather than tornadoes.

  10. Hourly observations of the jet stream - Wind shear, Richardson number and pilot reports of turbulence

    Science.gov (United States)

    Syrett, William J.

    1991-01-01

    Results are presented of observations of the jet stream made on the basis of over 400 hr of wind and temperature data taken during two prolonged jet stream passages above western and central Pennsylvania during mid-November 1986 and mid-January 1987. Wind profilers are found to be far better suited for the detailed examination of jet stream structure than are weather balloons. The combination of good vertical resolution with not previously obtained temporal resolution reveals structural details not seen before. Development of probability forecasts of turbulence based on wind profiler-derived shear values appears possible. A good correlation between pilot reports and turbulence and wind shear is found.

  11. Observations of wind and waves in the central Bay of Bengal during ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 112; Issue 2. Observations of wind ... Some of the available statistical predictive methods for the determination of MLD by forced mixing are utilized to test the extent of mechanical mixing within the top layer of water by the local wind and wave activity. The same is ...

  12. Fault Detection and Isolation and Fault Tolerant Control of Wind Turbines Using Set-Valued Observers

    DEFF Research Database (Denmark)

    Casau, Pedro; Rosa, Paulo Andre Nobre; Tabatabaeipour, Seyed Mojtaba

    2012-01-01

    Research on wind turbine Operations & Maintenance (O&M) procedures is critical to the expansion of Wind Energy Conversion systems (WEC). In order to reduce O&M costs and increase the lifespan of the turbine, we study the application of Set-Valued Observers (SVO) to the problem of Fault Detection...

  13. Observing and Simulating Wind-Turbine Wakes During the Evening Transition

    Science.gov (United States)

    Lee, Joseph C. Y.; Lundquist, Julie K.

    2017-09-01

    Wind-turbine-wake evolution during the evening transition introduces variability to wind-farm power production at a time of day typically characterized by high electricity demand. During the evening transition, the atmosphere evolves from an unstable to a stable regime, and vertical stratification of the wind profile develops as the residual planetary boundary layer decouples from the surface layer. The evolution of wind-turbine wakes during the evening transition is examined from two perspectives: wake observations from single turbines, and simulations of multiple turbine wakes using the mesoscale Weather Research and Forecasting (WRF) model. Throughout the evening transition, the wake's wind-speed deficit and turbulence enhancement are confined within the rotor layer when the atmospheric stability changes from unstable to stable. The height variations of maximum upwind-downwind differences of wind speed and turbulence intensity gradually decrease during the evening transition. After verifying the WRF-model-simulated upwind wind speed, wind direction and turbulent kinetic energy profiles with observations, the wind-farm-scale wake evolution during the evening transition is investigated using the WRF-model wind-farm parametrization scheme. As the evening progresses, due to the presence of the wind farm, the modelled hub-height wind-speed deficit monotonically increases, the relative turbulence enhancement at hub height grows by 50%, and the downwind surface sensible heat flux increases, reducing surface cooling. Overall, the intensifying wakes from upwind turbines respond to the evolving atmospheric boundary layer during the evening transition, and undermine the power production of downwind turbines in the evening.

  14. Robinson Crusoe: the fate of the British Ulysses.

    Science.gov (United States)

    Pimentel, Juan

    2010-03-01

    If travel has been one of the leitmotifs of Western imagination, Robinson Crusoe has certainly been one of its foremost incarnations. This British Ulysses foretold the global village, but also its problems. He predicted the end of distance, but also the triumph of isolation and anaesthetized loneliness. This paper provides an overview of the connections between Defoe's narrative and the new science and explores two versions of the story by two contemporary writers, Julio Cortazar and John Maxwell Coetzee. 2009 Elsevier Ltd. All rights reserved.

  15. Fault Diagnosis of an Advanced Wind Turbine Benchmark using Interval-based ARRs and Observers

    DEFF Research Database (Denmark)

    Sardi, Hector Eloy Sanchez; Escobet, Teressa; Puig, Vicenc

    2015-01-01

    This paper proposes a model-based fault diagnosis (FD) approach for wind turbines and its application to a realistic wind turbine FD benchmark. The proposed FD approach combines the use of analytical redundancy relations (ARRs) and interval observers. Interval observers consider an unknown...... but bounded description of the model parametric uncertainty and noise using the the so-called set-membership approach. This approach leads to formulate the fault detection test by means of checking if the measurements fall inside the estimated output interval, obtained from the mathematical model of the wind...... turbine and noise/parameter uncertainty bounds. Fault isolation is based on considering a set of ARRs obtained from the structural analysis of the wind turbine model and a fault signature matrix that considers the relation of ARRs and faults. The proposed FD approach has been validated on a 5-MW wind...

  16. Polar thermospheric winds and temperature observed by Fabry-Perot Interferometer at Jang Bogo Station, Antarctica

    Science.gov (United States)

    Jee, G.; Lee, C.; Song, I. S.; Wu, Q.; Kwon, H. J.; Kim, J. H.; Kim, Y.

    2016-12-01

    We analyze the night time neutral winds and temperature in the mesosphere and thermosphere regions (87 km, 97 km, and 250 km) by using the airglow observations by Fabry-Perot Interferometer (FPI) that was installed at Jang Bogo Station (JBS) in Antarctica in March 2014. JBS is located in the polar cap or auroral oval, depending on the local time and geomagnetic activity. This region of polar thermosphere is strongly influenced by the plasma convection driven by magnetospheric electric field. The neutral winds at 250 km measured from the red line (630.0 nm) clearly show the pattern similar to the plasma convection while the winds at 87 km measured from OH emission (892.0 nm) display the semidiurnal tidal effects propagated from the lower atmosphere. However, the winds at 97 km measured from the green line (557.7 nm) are considerably different from the winds at 87 km but more similar to the winds at 250 km in terms of diurnal variation. This result may indicate that the 97-km winds are mainly affected by the plasma convection rather than by tide at lower atmosphere. Note that there is a possibility that the 557.7 nm emissions may be contaminated by aurora in the polar region, which will be discussed in the present study. For the climatological study of the polar neutral winds, the comparison with HWM-2014 model is performed. Finally, the wind and temperature responses to geomagnetic storm on 17 March 2015 will be presented.

  17. Observer-based scheme for tuning the control of variable speed wind turbines operating in hostile environments

    DEFF Research Database (Denmark)

    Caruana, Cedric; Al-Durra, Ahmed; Blaabjerg, Frede

    2016-01-01

    The rapid growth rate of wind energy coupled with the increasing sizes of individual wind turbines strengthens the need for optimised wind energy capture. This study utilises the unknown input observer to track the variation of the maximal value of wind turbines' power coefficient to tune...

  18. Comparison of model predicted to observed winds in the coastal zone

    Energy Technology Data Exchange (ETDEWEB)

    Garstang, M.; Pielke, R.A.; Snow, J.W.

    1982-06-01

    Predictions of near-surface (10 to 100 m) wind velocities made by a mesoscale numerical model on a 10 km grid over and near the coastline are checked against observations. Two comparisons are made. The first is between observed and model-estimated mean annual wind power density at locations where surface observations exist in three coastal areas: the Chesapeake Bay, the Apalachee Bay and the South Texas coastal area. The second comparison is made between model predictions over the Delmarva Peninsula and adjacent ocean and observations made over a 120 x 30 km rectangle extending across the peninsula and out to sea. It is concluded that the unbiased error analysis skill ratings of 81% and 76% are attained for two days of prediction-observation comparisons. In the meantime, the skill of the model in duplicating individual coastal wind fields is taken as 78%. In addition, a qualitative comparison is made between the predicted fields of wind and the observed wind field. The predicted wind field unquestionably reproduces the observed field.

  19. Differences in mid-latitude stratospheric winds between reanalysis data and versus radiosonde observations at Prague

    Directory of Open Access Journals (Sweden)

    M. Kozubek

    2014-04-01

    Full Text Available Reanalysis data are very useful for studying the stratosphere. They can be used for analysis of long-term trends (temperature, wind speed, humidity, etc. or analysis of global atmospheric dynamics, etc. There are various reanalysis projects that provide outputs which are not identical. In this paper, we mutually compare three of them, ERA-40, ERA-Interim and NCEP/NCAR, and compare them with balloon radiosonde observations from Prague, Port Hardy and Valentia stations. This comparison is done for wind speed and direction at pressure levels 100 and 10 hPa and for various periods between 1957 and 2009. The results show that the differences between reanalysis vary. Wind speed data from all three analyses reasonably agree except for the 10 hPa historical data before 1966 and particularly ERA-40 data at the end of the data series (1998–2001. The quality of the ERA-40 10 hPa stratospheric wind data has been proven to be substantially worse over the last four ERA-40 years of 1998–2001 (2002 compared to previous years, both in wind speed and wind direction. The reanalysis data results are compared with radiosonde observations from Prague, Port Hardy and Valentia stations at 10 hPa for the months of February between 1989 and 2009. The results show that there are sometimes surprisingly large differences, more for ERA-Interim versus Prague measurements. Differences in wind direction greater than 45° (outliers between the reanalysis data and Prague observations in wind direction occur in Februaries predominantly when winds in Prague are in "minor" sectors, such as north, northeast and east (easterlies, whereas "major" sectors, particularly the dominant W (westerlies wind sector, exhibit almost no outliers.

  20. Solar wind stream interaction regions throughout the heliosphere

    Science.gov (United States)

    Richardson, Ian G.

    2018-01-01

    This paper focuses on the interactions between the fast solar wind from coronal holes and the intervening slower solar wind, leading to the creation of stream interaction regions that corotate with the Sun and may persist for many solar rotations. Stream interaction regions have been observed near 1 AU, in the inner heliosphere (at ˜ 0.3-1 AU) by the Helios spacecraft, in the outer and distant heliosphere by the Pioneer 10 and 11 and Voyager 1 and 2 spacecraft, and out of the ecliptic by Ulysses, and these observations are reviewed. Stream interaction regions accelerate energetic particles, modulate the intensity of Galactic cosmic rays and generate enhanced geomagnetic activity. The remote detection of interaction regions using interplanetary scintillation and white-light imaging, and MHD modeling of interaction regions will also be discussed.

  1. Detecting, categorizing and forecasting large romps in wind farm power output using meteorological observations and WPPT

    DEFF Research Database (Denmark)

    Cutler, N.; Kay, M.; Jacka, K.

    2007-01-01

    The Wind Power Prediction Tool (WPPT) has been installed in Australia for the first time, to forecast the power output from the 65MW Roaring 40s Renewable Energy P/L Woolnorth Bluff Point wind form. This article analyses the general performance of WPPT as well as its performance during large romps...... (swings) in power output. In addition to this, detected large ramps are studied in detail and categorized. WPPT combines wind speed and direction forecasts from the Australian Bureau of Meteorology regional numerical weather prediction model, MesoLAPS, with real-time wind power observations to make hourly...... forecasts of the wind farm power output. The general performances of MesoLAPS and WPPTore evaluated over I year using the root mean square error (RMSE). The errors are significantly lower than for basic benchmark forecasts but higher than for many other WPPT installations, where the site conditions...

  2. Theoretical and Observational Consequences of Rotation and Magnetic Fields in Stellar Winds

    Science.gov (United States)

    Ignace, Richard

    1996-05-01

    My dissertation concerns the study of stellar winds from theoretical modeling of the wind structure and the development of observational diagnostics. First, I have investigated the effects of stellar rotation for the wind structure of stars across the H-R Diagram. The effect of rotation is to increase the wind density at the equator while decreasing the density near the poles. The model, known as the Wind-Compressed Zone (WCZ) model, predicts that equatorial wind compressions are most likely to occur for stars with rapid rotation, low terminal speeds, and/or radial velocity distributions that increase gradually from the base of the wind. It is found that in favorable cases, stellar rotation can play a significant role in shaping the winds of Wolf Rayet stars, B supergiants, Asymptotic Giant Branch stars, and even some novae. The second major part of my thesis relates to the fact that the WCZ model will predict the magnetic field structure in the wind, if the field strength is relatively weak. However, there are generally no good diagnostics of stellar magnetic fields in the weak field limit, where Zeeman splitting is smaller than Doppler broadening. Thus, I have explored applications of the Hanle effect for probing magnetic fields in stellar winds. This effect (which has been used in studies of the solar atmosphere) deals with the modification of resonance line scattering polarization by a magnetic field. Solutions for the Hanle effect in optically thin axisymmetric extended stellar envelopes have been derived. Relative to the zero field case, the Hanle effect can result in significant changes of the line polarization, in some cases causing a position angle flip of 90(deg) . With multiline observations the Hanle effect is a viable diagnostic of stellar magnetic fields in the range 1-1000 Gauss. This thesis work was completed under the supervision of Joseph Cassinelli and in collaboration with Kenneth Nordsieck and Jon Bjorkman.

  3. From the Sun’s south to the north pole – Ulysses COSPIN/LET composition measurements at solar maximum

    Directory of Open Access Journals (Sweden)

    M. Y. Hofer

    2003-06-01

    Full Text Available Based on elemental abundance ratios derived from the Ulysses COSPIN/LET measurements, we classified the energetic particle populations during and after the socalled Fast Latitude Scan – the time period during which the Ulysses spacecraft traveled from the highest heliolatitude south to maximum northern latitude, i.e. 27 November 2000 to 13 October 2001 – as being mixed between solar energetic particles (major component and particles accelerated at stream interaction regions. During the fast latitude scan, the Ulysses spacecraft made the first transit in heliolatitude from pole to pole during solar activity maximum conditions, providing a unique opportunity to acquire energetic particle composition data over a maximum range of heliolatitudes in the inner heliosphere. At low latitudes, based on our elemental abundance analysis, we found that while solar energetic particles dominated, there were indications for particle acceleration at single compression regions in a few instances. In the high heliolatitude range the observed elemental particle compositions are mainly of the solar energetic particle type. Within the statistical errors, the observed abundance ratios were independent of latitude, and were characteristic of solar energetic particles. These observations raise an important question for the theories of particle propagation in the inner heliosphere. The daily elemental abundance ratios of S/O, Mg/O and Si/O shown here are the first measured ratios at high heliolatitudes in the energy range from 13.0 to 30.0 MeV/n.Key words. Interplanetary physics (energetic particles; interplanetary shocks – Solar physics, astrophysics and astronomy (flares and mass ejections

  4. Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

    Directory of Open Access Journals (Sweden)

    A. B. Galvin

    2009-10-01

    Full Text Available STEREO has now completed the first two years of its mission, moving from close proximity to Earth in 2006/2007 to more than 50 degrees longitudinal separation from Earth in 2009. During this time, several large-scale structures have been observed in situ. Given the prevailing solar minimum conditions, these structures have been predominantly coronal hole-associated solar wind, slow solar wind, their interfaces, and the occasional transient event. In this paper, we extend earlier solar wind composition studies into the current solar minimum using high-resolution (1-h sampling times for the charge state analysis. We examine 2-year trends for iron charge states and solar wind proton speeds, and present a case study of Carrington Rotation 2064 (December 2007 which includes minor ion (He, Fe, O kinetic and Fe composition parameters in comparison with proton and magnetic field signatures at large-scale structures observed during this interval.

  5. Disturbance observer based pitch control of wind turbines for disturbance rejection

    Science.gov (United States)

    Yuan, Yuan; Chen, Xu; Tang, Jiong

    2016-04-01

    In this research, a disturbance observer based (DOB) control scheme is illustrated to reject the unknown low frequency disturbances to wind turbines. Specifically, we aim at maintaining the constant output power but achieving better generator speed regulation when the wind turbine is operated at time-varying and turbulent wind field. The disturbance observer combined with a filter is designed to asymptotically reject the persistent unknown time-varying disturbances. The proposed algorithm is tested in both linearized and nonlinear NREL offshore 5-MW baseline wind turbine. The application of this DOB pitch controller achieves improved power and speed regulation in Region 3 compared with a baseline gain scheduling PID collective controller both in linearized and nonlinear plant.

  6. MESSENGER and Venus Express Observations of the Solar Wind Interaction with Venus

    Science.gov (United States)

    Slavin, James A.; Acuna, Mario H.; Anderson, Brian J.; Barabash, Stas; Benna, Mehdi; Boardsen, Scott A.; Fraenz, Markus; Gloeckler, George; Gold, Robert E.; Ho,George C.; hide

    2009-01-01

    At 23:08 UTC on 5 June 2007 the MESSENGER spacecraft reached its closest approach altitude of 338 kin during its final flyby of Venus en route to its 2011 orbit insertion at Mercury. The availability of the simultaneous Venus Express solar wind and interplanetary magnetic field measurements provides a rare opportunity to examine the influence of upstream conditions on this planet's solar wind interaction. We present MESSENGER observations of new features of the Venus - solar wind interaction including hot flow anomalies upstream of the bow shock, a flux rope in the near-tail and a two-point determination of the timescale for magnetic flux transport through this induced magnetosphere. Citation: Stavin, J. A., et al. (2009), MESSENGER and Venus Express observations of the solar wind interaction with Venus,

  7. Thermospheric wind variations observed by a Fabry-Perot interferometer at Tromsoe, Norway, at substorm onsets

    Science.gov (United States)

    Xu, H.; Shiokawa, K.; Oyama, S. I.; Otsuka, Y.

    2016-12-01

    In this research, we investigated the thermospheric wind variations before and after isolated substorm onset by using a Fabry-Perot interferometer (FPI) at Tromsoe, Norway. We used wind variations measured from the Doppler shift of both red line (630.0 nm, altitudes: 200-300 km) and green line (557.7 nm, altitudes: 90-100 km) with a time resolution of 13 min. The wind data were obtained for 7 years from 2009 to 2015. We first identified isolated local substorm onsets by using IMAGE magnetometer data, and checked the wind variations before and after these onset times. In total, we obtained 8 events from red line data and 10 events from green line data at different local times. Most wind observations were made at equatorward of substorm onset arcs which are identified by auroral images obtained at Tromsoe. We calculated differences of wind velocities at the onset time and 30-min (1-hour) after the onset time using winds averaged over ±15 min (±30 min) of the epoch time. For red line, except for few notable decreases at dawnside, eastward wind tends to increase from the onset time to both 30-min and 1-hour after the onset time at all nightside local times. This result is opposite to the tendency expected from thermospheric tidal wind variations, and suggests a particular eastward drive of thermospheric wind during substorms. With some exceptions, northward wind tends to decrease at local times before 0200 LT and increase after that, which is consistent with the expectation from thermospheric tides. For green line, eastward components have similar tendency of increase at all local times with some notable decreases at duskside. Northward components show some increases at pre-midnight sector, and significant decreases at duskside, post-midnight sector and dawnside. These results are obtained by using wind vectors obtained by the sky scanning of the FPI with assuming uniform winds in the field-of-view of the sky scanning. In the presentation we will also report results

  8. Mammal Observations-Oregon OCS Floating Wind Farm Site

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of the Oregon OCS Data Release presents marine mammal observations from U.S. Geological Survey (USGS) field activity 2014-607-FA in the Oregon Outer...

  9. Geologic Observations-Oregon OCS Floating Wind Farm Site

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This part of the Oregon Outer Continental Shelf (OCS) Floating Windfarm Suite Data Release presents geological observations from video collected on U.S. Geological...

  10. Observations of Plasma Turbulence and Heating from the Solar Wind and Simulations

    Science.gov (United States)

    Wicks, R. T.

    2015-12-01

    The cascade of energy by plasma turbulence has been shown to occur in, and heat, the solar wind. Recent work in the study of solar wind turbulence has focussed, in the most part, on advanced data analysis techniques, such as third moment structure functions, wavelets, conditional data sampling, multi-spacecraft observations and reconstruction of 2D k-spectra with tomography, and statistical studies from long time series of spacecraft observations. These techniques are complex and contain different assumptions about the qualities of the data underpinning the measurements. Here, we will review recent advances and discoveries in the study of plasma turbulence from solar wind data analysis and discuss how benchmarking of techniques against one another could be pursued and how simulations can be used to aid in the understanding of the results of solar wind data analysis, in particular in the framework of the "Turbulence Dissipation Challenge" (Parashar et al., Journal of Plasma Physics, Volume 81, Issue 05, 905810513, 2015). We will pay particular attention to observing two different heating mechanisms: stochastic heating and resonant wave-particle interactions. The magnetic helicity of the solar wind is shown to separate into two distinct components, one originating from pseudo-Alfvenic (k may have a component parallel to the magnetic field) and one from the Alfvenic fluctuations (k is strictly perpendicular). The solar wind results are compared with "pseudo-spacecraft" data from large 3D PIC simulations.

  11. Magnetic Cyclotron Waves near the Proton Cyclotron Frequency in the Solar Wind: Wind and ACE Observations in 2005

    Science.gov (United States)

    Broiles, T. W.; Jian, L.; Stevens, M. L.; Gary, S. P.; Lepri, S. T.; Vinas, A. F.; Moya, P. S.; Alexander, R.

    2016-12-01

    Strong narrow-band electromagnetic waves near the proton cyclotron frequency (fpc) have been observed extensively in the solar wind throughout the inner heliosphere. They are transverse and near-circularly polarized, and propagate in directions quasi-parallel or anti-parallel to the magnetic field. Their frequency is a few times of fpc in the spacecraft frame and a fraction of fpc in the plasma frame after removing the Doppler shift effect. These waves are left-hand (LH) or right-hand (RH) polarized in the spacecraft frame with otherwise similar characteristics except LH ones appear more often and have higher wave power. Intrinsically they can be LH polarized Alfven-cyclotron waves or RH polarized magnetosonic waves. Through the assistance of audification, we have studied the long-lasting wave events near fpc in 2005 using the high-cadence magnetic field data and well-calibrated plasma data from the Wind mission. A mixture of temperature anisotropies for core protons, beam protons, and alpha particles, as well as proton beam drift are often found for selected events of extensive waves. The wave dispersion analysis using these ion moments indicate these waves are likely to be associated with unstable Alfven-cyclotron anisotropy instability or ion beam instability, and suggest there is a mixture of Alfven-cyclotron waves and magnetosonic waves in the solar wind. Using the conjunction of Wind and ACE spacecraft when they were within 50 Earth radii of each other, we study how often the two spacecraft observe the same waves and whether there is noticeable heating for heavy ions associated with these waves.

  12. IPS observations of the solar wind speed out of the ecliptic

    Science.gov (United States)

    Coles, W. A.; Rickett, B. J.

    1976-01-01

    Interplanetary scintillation observations from 1971-1975 show that the average solar wind speed increases away from the solar equator, with a mean gradient of 2.1 km/s per degree. These results are compared with spacecraft observations over the + or - 7 deg attainable in the ecliptic and with those deduced from comet tails. The role of temporal variations, especially those caused by latitude dependent solar wind streams, is emphasized, and this points to the need for extensive ecliptic and ground-based observations during an out-of-the-ecliptic spacecraft mission.

  13. In situ observations of nightime warm katabatic winds on Gale by REMS.

    Science.gov (United States)

    Zorzano, María-Paz; Martín-Torres, Francisco Javier; Newman, Claire; Hamilton, Victoria; Martínez-Frías, Jesús; de la Torre, Manuel; Haberle, Bob; Mischna, Michael; Kahanpää, Henrik; Harri, Ari-Matti; Navarro, Sara; Lepinette, Alain; Sebastian, Eduardo; Javier Gómez-Elvira, REMS Team; the MSL Science Team

    2013-04-01

    We report the first in-situ observations of warm nighttime winds at Gale landing site. Gale is an impact crater basin with 5 km depth and an internal mound of the same height. This sharp topographic contrast induces huge environmental differences after sunset that leads to the appearance of downslope winds. Katabatic winds are produced as the descending mass of air is compressed adiabatically because of the pressure difference. This leads to the injection at the base of the crater of a jet of air with increased temperature. The Rover Environmental Monitoring Station (REMS) on the Mars Science Laboratory (MSL) mission has sensors recording air and ground temperature, pressure, relative humidity, wind speed and ultraviolet radiation in different bands. REMS collects data from all sensors simultaneously daily during the course of the mission. REMS has detected the signatures of katabatic winds simultaneously in 4 of its sensors: pressure wiggles associated with the incoming mass of air (pressure sensor), sudden air temperature increments up to 10 K (air temperature sensor); an associated modulation in the ground temperature (ground temperature sensor); and variations of strength and orientation indicating a donwnslope wind (wind sensor). The hot air winds observed by REMS show a pattern with a certain characteristic frequency along the nighttime hours. The magnitude and signature of the air temperature increase after sunset changes when the local column of dust increases suggesting a strong dependence on the local circulation of air and local column of dust. Katabatic winds must be ubiquous on Mars given the huge topographic differences of its poorly eroded landscape. These warm nighttime winds prevent cooling of the ground surface and may lead to erroneous thermal inertia estimates when the ground temperature is remotely measured from orbiters, that usually do not take them into account them in the retrieval process. Furthermore the signature of katabatic winds

  14. Quality Control Methodology Of A Surface Wind Observational Database In North Eastern North America

    Science.gov (United States)

    Lucio-Eceiza, Etor E.; Fidel González-Rouco, J.; Navarro, Jorge; Conte, Jorge; Beltrami, Hugo

    2016-04-01

    This work summarizes the design and application of a Quality Control (QC) procedure for an observational surface wind database located in North Eastern North America. The database consists of 526 sites (486 land stations and 40 buoys) with varying resolutions of hourly, 3 hourly and 6 hourly data, compiled from three different source institutions with uneven measurement units and changing measuring procedures, instrumentation and heights. The records span from 1953 to 2010. The QC process is composed of different phases focused either on problems related with the providing source institutions or measurement errors. The first phases deal with problems often related with data recording and management: (1) compilation stage dealing with the detection of typographical errors, decoding problems, site displacements and unification of institutional practices; (2) detection of erroneous data sequence duplications within a station or among different ones; (3) detection of errors related with physically unrealistic data measurements. The last phases are focused on instrumental errors: (4) problems related with low variability, placing particular emphasis on the detection of unrealistic low wind speed records with the help of regional references; (5) high variability related erroneous records; (6) standardization of wind speed record biases due to changing measurement heights, detection of wind speed biases on week to monthly timescales, and homogenization of wind direction records. As a result, around 1.7% of wind speed records and 0.4% of wind direction records have been deleted, making a combined total of 1.9% of removed records. Additionally, around 15.9% wind speed records and 2.4% of wind direction data have been also corrected.

  15. Nonlinear Predictive Control of Wind Energy Conversion System Using Dfig with Aerodynamic Torque Observer

    Science.gov (United States)

    Kamel, Ouari; Mohand, Ouhrouche; Toufik, Rekioua; Taib, Nabil

    2015-01-01

    In order to improvement of the performances for wind energy conversions systems (WECS), an advanced control techniques must be used. In this paper, as an alternative to conventional PI-type control methods, a nonlinear predictive control (NPC) approach is developed for DFIG-based wind turbine. To enhance the robustness of the controller, a disturbance observer is designed to estimate the aerodynamic torque which is considered as an unknown perturbation. An explicitly analytical form of the optimal predictive controller is given consequently on-line optimization is not necessary The DFIG is fed through the rotor windings by a back-to-back converter controlled by Pulse Width Modulation (PWM), where the stator winding is directly connected to the grid. The presented simulation results show a good performance in trajectory tracking of the proposed strategy and rejection of disturbances is successfully achieved.

  16. Observations of Downwind Development of Wind Speed and Variance Profiles at Bognaes and Comparison with Theory

    DEFF Research Database (Denmark)

    Jensen, Niels Otto; Højstrup, Jørgen; Peterson, E. W.

    1979-01-01

    Observations of atmospheric flow over a change in surface roughness are reported. Both wind speed and turbulence characteristics were measured. Although the observation site departed from the ideal assumed in roughness change models, it was found that the predictions of `second-order closure...

  17. The Høvsøre Tall Wind-Profile Experiment: A Description of Wind Profile Observations in the Atmospheric Boundary Layer

    DEFF Research Database (Denmark)

    Peña, Alfredo; Floors, Rogier Ralph; Gryning, Sven-Erik

    2014-01-01

    at a meteorological mast. The sonic measurements cover the first 100mand the wind lidar measures above 100m every 50min the vertical. Results of the analysis of observations of the horizontal wind-speed components in the range 10–1200 m and surface turbulence fluxes are illustrated in detail, combined with forcing...... for the analysis of vertical wind-speed profiles under a wide range of atmospheric stability, turbulence, and forcing conditions. One of the objectives of the campaign was to serve as a benchmark for flow over flat terrain models. The observations consist of combined wind lidar and sonic anemometer measurements...

  18. Interplanetary and Interstellar Dust Observed by the Wind/WAVES Electric Field Instrument

    Science.gov (United States)

    Malaspina, David; Horanyi, M.; Zaslavsky, A.; Goetz, K.; Wilson, L. B., III; Kersten, K.

    2014-01-01

    Observations of hypervelocity dust particles impacting the Wind spacecraft are reported here for the first time using data from the WindWAVES electric field instrument. A unique combination of rotating spacecraft, amplitude-triggered high-cadence waveform collection, and electric field antenna configuration allow the first direct determination of dust impact direction by any spacecraft using electric field data. Dust flux and impact direction data indicate that the observed dust is approximately micron-sized with both interplanetary and interstellar populations. Nanometer radius dust is not detected by Wind during times when nanometer dust is observed on the STEREO spacecraft and both spacecraft are in close proximity. Determined impact directions suggest that interplanetary dust detected by electric field instruments at 1 AU is dominated by particles on bound trajectories crossing Earths orbit, rather than dust with hyperbolic orbits.

  19. High Temporal Resolution Tropospheric Wind Profile Observations at NASA Kennedy Space Center During Hurricane Irma

    Science.gov (United States)

    Decker, Ryan; Barbre, Robert; Huddleston, Lisa; Wilfong, Tim; Brauer, Tom

    2018-01-01

    The NASA Kennedy Space Center (KSC) operates a 48-MHz Tropospheric/Stratospheric Doppler Radar Wind Profiler (TDRWP) on a continual basis generating wind profiles between 2-19 km in the support of space launch vehicle operations. A benefit of the continual operability of the system is the ability to provide unique observations of severe weather events such as hurricanes. On the evening of 10 September 2017, Hurricane Irma passed within 100 miles to the west of KSC through the middle of the Florida peninsula. The hurricane was responsible for power outages to approximately 2/3 of Florida's population. This paper will describe the characteristics of the tropospheric wind observations from the TDRWP during Irma, provide a comparison to previous TDRWP observations from Hurricane Matthew in 2016, and discuss lessons learned regarding dissemination of TDRWP data during the event.

  20. Wind‐gust parametrizations at heights relevant for wind energy: a study based on mast observations

    DEFF Research Database (Denmark)

    Suomi, I.; Vihma, T.; Gryning, Sven-Erik

    2013-01-01

    Wind gusts are traditionally observed and reported at the reference height of 10 m and most gust parametrization methods have been developed only for this height. In many practical applications, e.g. in wind energy, the relevant heights are, however, up to a few hundred metres. In this study, mean...... gustiness conditions were studied using observations from two coastal/archipelago weather masts in the Gulf of Finland (northern Europe) with observation heights between 30 and 143 m. Only moderate and strong wind cases were addressed. Both masts were located over relatively flat terrain but the local...... speed, which is parametrized on the basis of the surface friction velocity, the Obukhov length and height and the boundary‐layer height. The new gust parametrization method outperformed the two older methods: the effects of surface roughness, stability and the height above the surface were well...

  1. The solar wind as a turbulence laboratory- some new quantitative points of contact between theory and solar wind observations

    Science.gov (United States)

    Hnat, Bogdan; Chapman, Sandra; Gogoberidze, Giga; Kiyani, Khurom; Osman, Kareem; Turner, Andrew

    2013-04-01

    Single point observations of the high Reynolds number solar wind flow, suitable for the study of turbulence, are on timescales from below ion kinetic scales up to days, providing extensive datasets for the study of plasma turbulence. Central to the concept of using the solar wind as a test laboratory for plasma turbulence are methods that allow direct quantitative comparison between the predictions of theory and simulation, and the observations. Critically, theoretical predictions, and data analysis methods, must come together in a manner in which uncertainties can be well understood, and thus different theoretical scenarios be distinguished unambiguously. Scaling is a key prediction of theories of infinite range turbulence. Its full characterization requires the scaling exponents of all the moments of the probability density of fluctuations as a function of scale. In practice, only the first few moments are accessible. Comparisons with theory often focus on the second moment scaling, that is, the exponent of the power spectral density (PSD). We focus on what can be learned from two key properties of turbulent fluctuations: components of the tensor power spectral density, and the functional form and scaling of the non- Gaussian pdf of fluctuations. Solar wind plasma turbulence is anisotropic due to the presence of a background field, so that in general the power spectral density (or correlation) tensor is needed to characterise the turbulence. We focus on the ratios of the PSD tensor terms which are sensitive to the scaling exponent, providing a method for direct observational tests of theories. The reduced PSD tensor accessed by single spacecraft measurements yields ratios of perpendicular terms which we show are robust to uncertainties. In the MHD inertial range of turbulence in the solar wind, these can clearly distinguish turbulence theories as we discuss[1]. They also offer insights into the physics below the ion kinetic scales where a further scaling range

  2. Seasonal and diurnal changes in wind variability from Flatland VHF profiler observations

    Energy Technology Data Exchange (ETDEWEB)

    Nastrom, G.D. [Saint Cloud State Univ., MN (United States). Dept. of Earth Sci.; Clark, W.L. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Aeronomy Lab.; Zandt, T.E. van [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Aeronomy Lab.; Warnock, J.M. [National Oceanic and Atmospheric Administration, Boulder, CO (United States). Aeronomy Lab.

    1996-02-01

    Climatological results are presented on the hourly variance of the wind observed in the mid-troposphere (3 to 9 km MSL). This quantity roughly indicates the energy in the atmospheric wind field for variations with periods roughly less than 1 hour. Observations are from the Flatland VHF research wind profiler, located near Champaign/Urbana, Illinois, well away from significant orographic features. The period of record covers two years, September 1990 through August 1992. The values of the variance of the winds along vertical and oblique (15 degrees from zenith in the cardinal directions) beams are presented versus height, season, time-of-day, and beam pointing direction. It is found that the hourly variance values have approximately lognormal frequency distribution. The mean hourly variance is significantly larger for the oblique wind observations than for the vertical. Mean wind variances also tend to be larger in the east/west steering plane than in the north/south plane. The mean variance generally increases with height, but faster than would be expected if it were due solely to the decrease in atmospheric density, implying the presence of local source/sinks of wind energy. The rate of change with height is noticeably different for the vertical and oblique beams, being much less for the vertical beam, in some seasons even decreasing with height. With respect to season, the mean hourly variance is smallest in the summer and largest in the winter. With respect to diurnal changes, the variance is maximum during the afternoon for spring, summer, and autumn, with the maximum up to a factor of two larger than the minimum. In winter, the diurnal change is much smaller, with little indication of an afternoon maximum. (orig.)

  3. The observable properties of cool winds from galaxies, AGN, and star clusters - I. Theoretical framework

    Science.gov (United States)

    Krumholz, Mark R.; Thompson, Todd A.; Ostriker, Eve C.; Martin, Crystal L.

    2017-11-01

    Winds arising from galaxies, star clusters, and active galactic nuclei are crucial players in star and galaxy formation, but it has proven remarkably difficult to use observations of them to determine physical properties of interest, particularly mass fluxes. Much of the difficulty stems from a lack of a theory that links a physically realistic model for winds' density, velocity and covering factors to calculations of light emission and absorption. In this paper we provide such a model. We consider a wind launched from a turbulent region with a range of column densities, derive the differential acceleration of gas as a function of column density, and use this result to compute winds' absorption profiles, emission profiles and emission intensity maps in both optically thin and optically thick species. The model is sufficiently simple that all required computations can be done analytically up to straightforward numerical integrals, rendering it suitable for the problem of deriving physical parameters by fitting models to observed data. We show that our model produces realistic absorption and emission profiles for some example cases, and argue that the most promising methods of deducing mass fluxes are based on combinations of absorption lines of different optical depths, or on combining absorption with measurements of molecular line emission. In the second paper in this series, we expand on these ideas by introducing a set of observational diagnostics that are significantly more robust than those commonly in use, and that can be used to obtain improved estimates of wind properties.

  4. Observed Trend in Surface Wind Speed Over the Conterminous USA and CMIP5 Simulations

    Science.gov (United States)

    Hashimoto, Hirofumi; Nemani, Ramakrishna R.

    2016-01-01

    There has been no spatial surface wind map even over the conterminous USA due to the difficulty of spatial interpolation of wind field. As a result, the reanalysis data were often used to analyze the statistics of spatial pattern in surface wind speed. Unfortunately, no consistent trend in wind field was found among the available reanalysis data, and that obstructed the further analysis or projection of spatial pattern of wind speed. In this study, we developed the methodology to interpolate the observed wind speed data at weather stations using random forest algorithm. We produced the 1-km daily climate variables over the conterminous USA from 1979 to 2015. The validation using Ameriflux daily data showed that R2 is 0.59. Existing studies have found the negative trend over the Eastern US, and our study also showed same results. However, our new datasets also revealed the significant increasing trend over the southwest US especially from April to June. The trend in the southwestern US represented change or seasonal shift in North American Monsoon. Global analysis of CMIP5 data projected the decrease trend in mid-latitude, while increase trend in tropical region over the land. Most likely because of the low resolution in GCM, CMIP5 data failed to simulate the increase trend in the southwest US, even though it was qualitatively predicted that pole ward shift of anticyclone help the North American Monsoon.

  5. Control of variable speed variable pitch wind turbine based on a disturbance observer

    Science.gov (United States)

    Ren, Haijun; Lei, Xin

    2017-11-01

    In this paper, a novel sliding mode controller based on disturbance observer (DOB) to optimize the efficiency of variable speed variable pitch (VSVP) wind turbine is developed and analyzed. Due to the highly nonlinearity of the VSVP system, the model is linearly processed to obtain the state space model of the system. Then, a conventional sliding mode controller is designed and a DOB is added to estimate wind speed. The proposed control strategy can successfully deal with the random nature of wind speed, the nonlinearity of VSVP system, the uncertainty of parameters and external disturbance. Via adding the observer to the sliding mode controller, it can greatly reduce the chattering produced by the sliding mode switching gain. The simulation results show that the proposed control system has the effectiveness and robustness.

  6. Suzaku Observations of PSR B1259-63: A New Manifestation of Relativistic Pulsar Wind

    Energy Technology Data Exchange (ETDEWEB)

    Uchiyama, Yasunobu; Tanaka, Takaaki; Takahashi, Tadayuki; Mori, Koji; Nakazawa, Kazuhiro

    2009-04-27

    We observed PSR B1259-63, a young non-accreting pulsar orbiting around a Be star SS 2883, eight times with the Suzaku satellite from July to September 2007, to characterize the X-ray emission arising from the interaction between a pulsar relativistic wind and Be star outflows. The X-ray spectra showed a featureless continuum in 0.6-10 keV, modeled by a power law with a wide range of photon index 1.3-1.8. When combined with the Suzaku PIN detector which allowed spectral analysis in the hard 15-50 keV band, X-ray spectra do show a break at {approx} 5 keV in a certain epoch. Regarding the PSR B1259-63 system as a compactified pulsar wind nebula, in which e{sup {+-}} pairs are assumed to be accelerated at the inner shock front of the pulsar wind, we attribute the X-ray spectral break to the low-energy cutoff of the synchrotron radiation associated with the Lorentz factor of the relativistic pulsar wind {gamma}{sub 1} {approx} 4 x 10{sup 5}. Our result indicates that Comptonization of stellar photons by the unshocked pulsar wind will be accessible (or tightly constrained) by observations with the Fermi Gamma-ray Space Telescope during the next periastron passage. The PSR B1259-63 system allows us to probe the fundamental properties of the pulsar wind by a direct means, being complementary to the study of large-scale pulsar wind nebulae.

  7. Accretion disk winds in active galactic nuclei: X-ray observations, models, and feedback

    Science.gov (United States)

    Tombesi, F.

    2016-05-01

    Powerful winds driven by active galactic nuclei (AGN) are often invoked to play a fundamental role in the evolution of both supermassive black holes (SMBHs) and their host galaxies, quenching star formation and explaining the tight SMBH-galaxy relations. A strong support of this ``quasar mode'' feedback came from the recent X-ray observation of a mildly relativistic accretion disk wind in a ultraluminous infrared galaxy (ULIRG) and its connection with a large-scale molecular outflow, providing a direct link between the SMBH and the gas out of which stars form. Spectroscopic observations, especially in the X-ray band, show that such accretion disk winds may be common in local AGN and quasars. However, their origin and characteristics are still not fully understood. Detailed theoretical models and simulations focused on radiation, magnetohydrodynamic (MHD) or a combination of these two processes to investigate the possible acceleration mechanisms and the dynamics of these winds. Some of these models have been directly compared to X-ray spectra, providing important insights into the wind physics. However, fundamental improvements on these studies will come only from the unprecedented energy resolution and sensitivity of the upcoming X-ray observatories, namely ASTRO-H (launch date early 2016) and Athena (2028).

  8. Scaling laws of turbulence and heating of fast solar wind: the role of density fluctuations.

    Science.gov (United States)

    Carbone, V; Marino, R; Sorriso-Valvo, L; Noullez, A; Bruno, R

    2009-08-07

    Incompressible and isotropic magnetohydrodynamic turbulence in plasmas can be described by an exact relation for the energy flux through the scales. This Yaglom-like scaling law has been recently observed in the solar wind above the solar poles observed by the Ulysses spacecraft, where the turbulence is in an Alfvénic state. An analogous phenomenological scaling law, suitably modified to take into account compressible fluctuations, is observed more frequently in the same data set. Large-scale density fluctuations, despite their low amplitude, thus play a crucial role in the basic scaling properties of turbulence. The turbulent cascade rate in the compressive case can, moreover, supply the energy dissipation needed to account for the local heating of the nonadiabatic solar wind.

  9. Scaling Laws of Turbulence and Heating of Fast SolarWind: The Role of Density Fluctuations

    CERN Document Server

    Carbone, V; Sorriso-Valvo, L; Noullez, A; Bruno, R

    2010-01-01

    Incompressible and isotropic magnetohydrodynamic turbulence in plasms can be described by an exact relation for the energy flux through the scales. This Yaglom-like scaling law has been recently observed in the solar wind above the solar poles observed by the Ulysses spacecraft, where the turbulence is in an Alfv\\'enic state. An analogous phenomenological scaling law, suitably modified to take into account compressible fluctuations, is observed more frequently in the same dataset. Large scale density fluctuations, despite their low amplitude, play thus a crucial role in the basic scaling properties of turbulence. The turbulent cascade rate in the compressive case can moreover supply the energy dissipation needed to account for the local heating of the non-adiabatic solar wind.

  10. The Solar Wind as a Turbulence Laboratory

    Directory of Open Access Journals (Sweden)

    Vincenzo Carbone

    2013-05-01

    Full Text Available In this review we will focus on a topic of fundamental importance for both astrophysics and plasma physics, namely the occurrence of large-amplitude low-frequency fluctuations of the fields that describe the plasma state. This subject will be treated within the context of the expanding solar wind and the most meaningful advances in this research field will be reported emphasizing the results obtained in the past decade or so. As a matter of fact, Helios inner heliosphere and Ulysses' high latitude observations, recent multi-spacecrafts measurements in the solar wind (Cluster four satellites and new numerical approaches to the problem, based on the dynamics of complex systems, brought new important insights which helped to better understand how turbulent fluctuations behave in the solar wind. In particular, numerical simulations within the realm of magnetohydrodynamic (MHD turbulence theory unraveled what kind of physical mechanisms are at the basis of turbulence generation and energy transfer across the spectral domain of the fluctuations. In other words, the advances reached in these past years in the investigation of solar wind turbulence now offer a rather complete picture of the phenomenological aspect of the problem to be tentatively presented in a rather organic way.

  11. ULYSSES IN THE DIVINE COMEDY – HELL – A COMPARISON OF THE HERO IN DANTE, HOMER AND VIRGIL

    Directory of Open Access Journals (Sweden)

    Alysson Ramos Artuso

    2016-07-01

    Full Text Available Ulysses is a constant character in Western literature and Dante Alighieri was an author that rework him. In the Divine Comedy, Ulysses is in Hell, in the eighth ditch of the eighth circle, corresponding to the fraudsters. In the construction of this character, Dante recovered Ulysses characteristics from Greek and Latin tradition, which is analyzed and compared in this article with the Homer’s and Virgil’s characters. At the end, Ulysses and Dantes - author and character of Comedy – are related.

  12. Geology of Biblis Patera, Ulysses Patera, and Jovis Tholus, Mars

    Science.gov (United States)

    Plescia, J. B.

    1993-01-01

    There are a variety of constructional volcanic features in Tharsis. These features range from Olympus Mons and the Tharsis Montes shields, to the small low shields and fissure eruptions that characterize much of the volcanic plains, to the smaller volcanic constructs in the northeast and western parts of Tharsis. I describe the geology of the western group, which includes Biblis Patera, Ulysses Patera, and Jovis Tholus. Each of these volcanoes has had a unique, and complex geologic history. Biblis Patera is located at 2.3 deg. N, 123.8 deg. The volcano is elongate in a northwesterly direction and has a large, faulted caldera complex. The flanks of the volcano and adjacent plains are characterized by lava flows, northwest-trending graben and troughs, and caldera-concentric graben and troughs. Biblis Patera is approximately 66 x 127 km with an oval 51 x 56 km caldera; the summit elevation is approximately 2 km above the surrounding plains. The constrcut has an estimated volume of 8-22 x 10(exp 3) cu km. Ulysses Patera is located at 2.7 deg. N, 121.3 deg. W and stands approx. 2-3 km above the surrounding plain; flank slopes are approximately 7 deg. to 12 deg. The caldera floor is quite deep, lying 1.8 to 2.2 km below the caldera rim. The caldera has a void volume of approximately 5000 cu km, the total solid mass volume of the volcano is 7-16 x 10(exp 3) cu km. Jovis Tholus is centered at 18.3 deg N; 117.5 deg W; it is a low relief, volcano with gentle flank slopes of between 3 and 8 deg. The construct is dominated by a series of inset calderas which make up the largest fraction of the area. The caldera complex is offset to the southwest side. Total shield dimensions are approximately 77 km (e-wt) by 62 km (n-s); the caldera complex is approximately 44 x 34 km. The shield is embayed on all sides by younger Amazonian age volcanics. Total relief, relative to the surrounding plains, is probably approximately 2 km. The total volume of Jovis Tholus is estimated to be

  13. Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

    Science.gov (United States)

    Yueh, Simon H.; Chaubell, Mario J.

    2012-01-01

    Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed

  14. Surface Wind Observational Database in North Eastern North America: Quality Control Procedure and Climatological Variability

    Science.gov (United States)

    Lucio-Eceiza, Etor E.; Fidel González-Rouco, J.; Navarro, Jorge; Hidalgo, Ángela; Conte, Jorge; Beltrami, Hugo

    2015-04-01

    This work summarizes the design and application of a Quality Control (QC) procedure for an observational surface wind database located in North Eastern North America. It also presents some insights of the long-term climatological variability over the region. The database consists of 527 sites (487 land stations and 40 buoys) with varying resolutions of hourly, 3 hourly and 6 hourly data, compiled from three different source institutions. The records span from 1940 to 2010 and cover an approximate spatial extension of 2.2 × 106 km2. The QC process is composed of different phases focused either on problems related with the providing source institutions or measurement errors. Due to the size of the data set, a great effort has been made on the automation of the procedures. A number of problems are associated with data management and data conventions: unification of measurement units and recording times due to the variety of institutional sources; detection of erroneous data sequence duplications within a station or among different ones; and detection of errors related with physically unrealistic data measurements. From the other hand there is a variety of treated instrumental errors: problems related with low variability, placing particular emphasis on the detection of unrealistic low wind speed records with the help of regional references; high variability related erroneous records; wind speed biases on week to monthly timescales and homogenization of wind direction records. As a result, around 1.7% of wind speed records and 0.4% of wind direction records have been deleted, making a combined total of 1.9% of removed records. Around 2.4% of wind direction data have been also corrected. The already quality controlled database allows for subsequent climatological analyses. The intra and inter decadal variability of the monthly surface wind field in such a vast and orographically complex region as the North Eastern North America is explored. Several decades of quality

  15. Open solar flux estimates from near-Earth measurements of the interplanetary magnetic field: comparison of the first two perihelion passes of the Ulysses spacecraft

    Directory of Open Access Journals (Sweden)

    M. Lockwood

    2004-04-01

    Full Text Available Results from all phases of the orbits of the Ulysses spacecraft have shown that the magnitude of the radial component of the heliospheric field is approximately independent of heliographic latitude. This result allows the use of near-Earth observations to compute the total open flux of the Sun. For example, using satellite observations of the interplanetary magnetic field, the average open solar flux was shown to have risen by 29% between 1963 and 1987 and using the aa geomagnetic index it was found to have doubled during the 20th century. It is therefore important to assess fully the accuracy of the result and to check that it applies to all phases of the solar cycle. The first perihelion pass of the Ulysses spacecraft was close to sunspot minimum, and recent data from the second perihelion pass show that the result also holds at solar maximum. The high level of correlation between the open flux derived from the various methods strongly supports the Ulysses discovery that the radial field component is independent of latitude. We show here that the errors introduced into open solar flux estimates by assuming that the heliospheric field's radial component is independent of latitude are similar for the two passes and are of order 25% for daily values, falling to 5% for averaging timescales of 27 days or greater. We compare here the results of four methods for estimating the open solar flux with results from the first and second perehelion passes by Ulysses. We find that the errors are lowest (1–5% for averages over the entire perehelion passes lasting near 320 days, for near-Earth methods, based on either interplanetary magnetic field observations or the aa geomagnetic activity index. The corresponding errors for the Solanki et al. (2000 model are of the order of 9–15% and for the PFSS method, based on solar magnetograms, are of the order of 13–47%. The model of Solanki et al. is based on the continuity equation of open flux, and uses the

  16. ROSAT Observations of Solar Wind Charge Exchange with the Lunar Exosphere

    Science.gov (United States)

    Collier, Michael R.; Snowden, S. L.; Benna, M.; Carter, J. A.; Cravens, T. E.; Hills, H. Kent; Hodges, R. R.; Kuntz, K. D.; Porter, F. Scott; Read, A.; hide

    2012-01-01

    We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the anti-solar direction. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the count rate increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere. Along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed. This technique can be used to explore the solar wind-lunar interaction.

  17. Observations and Predictability of Gap Winds in the Salmon River Canyon of Central Idaho, USA

    Directory of Open Access Journals (Sweden)

    Natalie S. Wagenbrenner

    2018-01-01

    Full Text Available This work investigates gap winds in a steep, deep river canyon prone to wildland fire. The driving mechanisms and the potential for forecasting the gap winds are investigated. The onset and strength of the gap winds are found to be correlated to the formation of an along-gap pressure gradient linked to periodic development of a thermal trough in the Pacific Northwest, USA. Numerical simulations are performed using a reanalysis dataset to investigate the ability of numerical weather prediction (NWP to simulate the observed gap wind events, including the timing and flow characteristics within the canyon. The effects of model horizontal grid spacing and terrain representation are considered. The reanalysis simulations suggest that horizontal grid spacings used in operational NWP could be sufficient for simulating the gap flow events given the regional-scale depression in which the Salmon River Canyon is situated. The strength of the events, however, is under-predicted due, at least in part, to terrain smoothing in the model. Routine NWP, however, is found to have mixed results in terms of forecasting the gap wind events, primarily due to problems in simulating the regional sea level pressure system correctly.

  18. Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

    Directory of Open Access Journals (Sweden)

    M. H. Denton

    2008-03-01

    Full Text Available Moments calculated from the ion distributions (~0–40 keV measured by the Cluster Ion Spectrometry (CIS instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM instrument and used to characterise the bulk properties of the plasma in the near-Earth magnetosphere over five years (2001–2005. Results are presented in the form of 2-D xy, xz and yz GSM cuts through the magnetosphere using data obtained from the Cluster Science Data System (CSDS and the Cluster Active Archive (CAA. Analysis reveals the distribution of ~0–40 keV ions in the inner magnetosphere is highly ordered and highly responsive to changes in solar wind velocity. Specifically, elevations in temperature are found to occur across the entire nightside plasma sheet region during times of fast solar wind. We demonstrate that the nightside plasma sheet ion temperature at a downtail distance of ~12 to 19 Earth radii increases by a factor of ~2 during periods of fast solar wind (500–1000 km s−1 compared to periods of slow solar wind (100–400 km s−1. The spatial extent of these increases are shown in the xy, xz and yz GSM planes. The results from the study have implications for modelling studies and simulations of solar-wind/magnetosphere coupling, which ultimately rely on in situ observations of the plasma sheet properties for input/boundary conditions.

  19. ACE/SWICS OBSERVATIONS OF HEAVY ION DROPOUTS WITHIN THE SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Weberg, Micah J. [PhD Candidate in Space and Planetary Physics, 2435 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. (United States); Zurbuchen, Thomas H. [Professor, Space Science and Aerospace Engineering, Associate Dean for Entrepreneurship, 2429 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. (United States); Lepri, Susan T., E-mail: mjweberg@umich.edu, E-mail: thomasz@umich.edu, E-mail: slepri@umich.edu [Associate Research Scientist, 2417 Space Research Building, 2455 Hayward Street, Ann Arbor, MI 48109-2143, USA. (United States)

    2012-11-20

    We present the first in situ observations of heavy ion dropouts within the slow solar wind, observed for select elements ranging from helium to iron. For iron, these dropouts manifest themselves as depletions of the Fe/H ratio by factors up to {approx}25. The events often exhibit mass-dependent fractionation and are contained in slow, unsteady wind found within a few days from known stream interfaces. We propose that such dropouts are evidence of gravitational settling within large coronal loops, which later undergo interchange reconnection and become source regions of slow, unsteady wind. Previously, spectroscopic studies by Raymond et al. in 1997 (and later Feldman et al. in 1999) have yielded strong evidence for gravitational settling within these loops. However, their expected in situ signature plasma with heavy elements fractionated by mass was not observed prior to this study. Using data from the SWICS instrument on board the Advanced Composition Explorer (ACE), we investigate the composition of the solar wind within these dropouts and explore long term trends over most of a solar cycle.

  20. First observation of mesosphere response to the solar wind high-speed streams

    Science.gov (United States)

    Yi, Wen; Reid, Iain M.; Xue, Xianghui; Younger, Joel P.; Spargo, Andrew J.; Murphy, Damian J.; Chen, Tingdi; Dou, Xiankang

    2017-08-01

    We present a first analysis of 9 and 6.75 day periodic oscillations observed in the neutral mesospheric density in 2005 and 2006. Mesospheric densities near 90 km are derived using data from the Davis meteor radar (68.5°S, 77.9°E; magnetic latitude, 74.6°S), Antarctica. Spectral analysis indicates that the pronounced periodicities of 9 and 6.75 days observed in the mesosphere densities are associated with variations in solar wind high-speed streams and recurrent geomagnetic activity. Neutral mesospheric winds and temperatures, simultaneously measured by the Davis meteor radar, also exhibit 9 and 6.75 day periodicities. A Morlet wavelet analysis shows that the time evolution of the 9 and 6.75 day oscillations in the neutral mesosphere densities and winds are similar to those in the solar wind and in planetary magnetic activity index, Kp in 2005 and 2006. These results demonstrate a direct coupling between Sun's corona (upper atmosphere) and the Earth's mesosphere.

  1. IPS observations of the solar wind velocity and the acceleration mechanism

    Science.gov (United States)

    Ofman, L.; Davila, J. M.; Coles, W. A.; Grall, R. R.; Klinglesmith, M. T.

    1997-01-01

    Coronal holes are well know sources of high speed solar wind, however, the exact acceleration mechanism of the wind is still unknown. Interplanetary scintillation (IPS) observations indicate that the fast solar wind reaches an average velocity of 800 km s(exp -1) within several solar radii with large velocity fluctuations. However, the origin of the IPS velocity spread below 10 solar radii is unclear. A previously developed coronal home model with a more realistic initial state is applied, and time-dependent, nonlinear, resistive 2.5-DMHD equations are numerically solved. It is found that nonlinear solitary-like waves with a supersonic phase speed are generated in coronal holes by torisonal Alfven waves in the radial flow velocity. The outward propagating nonlinear waves are similar in properties to sound solitons. When these waves are present, the solar wind speed and density fluctuate considerably on a time scale of an hour and on spatial scales of several solar radii in addition to the Alfvenic fluctuations. This is in qualitative agreement with the IPS velocity observations beyond 10 solar radii.

  2. The RUNE Experiment—A Database of Remote-Sensing Observations of Near-Shore Winds

    Directory of Open Access Journals (Sweden)

    Rogier Floors

    2016-10-01

    Full Text Available We present a comprehensive database of near-shore wind observations that were carried out during the experimental campaign of the RUNE project. RUNE aims at reducing the uncertainty of the near-shore wind resource estimates from model outputs by using lidar, ocean, and satellite observations. Here, we concentrate on describing the lidar measurements. The campaign was conducted from November 2015 to February 2016 on the west coast of Denmark and comprises measurements from eight lidars, an ocean buoy and three types of satellites. The wind speed was estimated based on measurements from a scanning lidar performing PPIs, two scanning lidars performing dual synchronized scans, and five vertical profiling lidars, of which one was operating offshore on a floating platform. The availability of measurements is highest for the profiling lidars, followed by the lidar performing PPIs, those performing the dual setup, and the lidar buoy. Analysis of the lidar measurements reveals good agreement between the estimated 10-min wind speeds, although the instruments used different scanning strategies and measured different volumes in the atmosphere. The campaign is characterized by strong westerlies with occasional storms.

  3. Observing and quantifying the solar wind signature of the magnetically complex corona.

    Science.gov (United States)

    Hnat, B.; Chapman, S. C.; Kiyani, K. H.; Nicol, R. M.

    2008-12-01

    The solar wind exhibits fluctuations over a broad range of timescales characteristic of magnetohydrodynamic (MHD) turbulence evolving in the presence of structures of coronal origin. In- situ spacecraft observations of plasma parameters are at minute (or below) resolution for intervals spanning the solar cycle and provide a large number of samples for statistical studies. The magnetic field power spectrum typically has two characteristic components, an inertial range of turbulence over several orders of magnitude with approximately Kolmogorov power law and at lower frequencies, an approximately '1/f' energy containing range believed to be of direct coronal origin. We focus on the behaviour of in- situ observations of fluctuations in the inner heliosphere as a function of solar cycle and solar wind speed; that is, with respect to coronal structure and dynamics. We employ a recently developed technique that sensitively distinguishes between fractal and multifractal scaling in the timeseries. Our working hypothesis is that since the latter can be characteristic of local MHD turbulence, the former maps more directly to features of coronal origin. We find a strong correlation between the scaling properties of magnetic energy density fluctuations and the magnetic complexity of the coronal magnetic fields. At solar maximum in the ecliptic, where the in- situ observations can be dominated by slow solar wind, the magnetic energy density as seen by WIND and ACE shows a fractal signature, whereas at minimum it is multifractal. This is corroborated by ULLYSES polar observations at solar minimum in quiet, fast solar wind where again, multifractal scaling is found. This high magnetic complexity in the corona corresponds to fractal, rather than multifractal scaling in magnetic energy density; remarkably, this fractal signature dominates the full dynamic range of observations, extending across timescales typically identified with both the '1/f' and 'inertial range'. The

  4. Observing System Simulation Experiment (OSSE) for a future Doppler Wind Lidar satellite in Japan:

    Science.gov (United States)

    Baron, Philippe; Ishii, Shoken; Okamoto, Kozo

    2017-04-01

    A feasibility study of tropospheric wind measurements by a coherent Doppler lidar aboard a super-low-altitude satellite is being conducted in Japan. We consider a coherent lidar with a laser light source at 2.05 μm whose characteristics correspond to an existing ground-based instrument (power=3.75 W, PRF=30 Hz and pulse width=200 ns). An Observing System Simulation Experiment (OSSE) has been implemented based on the Sensitivity Observing System experiment (SOSE) developed at the Japanese Meteorological-Research-Institute using the Japan Meteorological Agency global Numerical Weather Prediction model. The measurement simulator uses wind, aerosol and cloud 3-d global fields from the OSSE speudo-truth and the aerosol model MASINGAR. In this presentation, we will first discuss the measurement performances. Considering measurement horizontal resolutions of 100 km along the orbit track, we found that below 3 km, the median horizontal wind error is between 0.8-1 m/s for a vertical resolution of 0.5 km, and that near 50% of the data are valid measurements. Decreasing the vertical resolution to 1 km allows us to maintain similar performances up to 8 km almost over most latitudes. Above, the performances significantly fall down but a relatively good percentage of valid measurements (20-40%) are still found near the tropics where cirrus clouds frequently occur. The potential of the instrument to improve weather prediction models will be discussed using the OSSE results obtained for both polar and low inclination orbit satellites. The first results show positive improvements of short-term forecasts (performance assessment of future space-borne Doppler wind lidar", SOLA, vol. 12, pp. 55-59, 2016. S. Ishii et al., "Feasibility study for future space-borne coherent Doppler wind lidar, Part 1: Instrumental Overview for Global Wind Profile Observation", submitted to J. Meteor. Soc. Japan, 2016 P. Baron et al., "Feasibility study for future space-borne coherent Doppler wind lidar

  5. Electron instability thresholds of solar wind magnetic fluctuations in non-thermal anisotropic kappa distribution plasmas: Survey of Wind-SWE-VEIS observations

    Science.gov (United States)

    Vinas, A. F.; Adrian, M. L.; Moya, P. S.; Wendel, D. E.

    2015-12-01

    The solar wind electron velocity distribution function (eVDF) displays a great variety of non-thermal features (e.g., core, halo and strahl electron populations; with superposition of different temperatures, thermal anisotropies, suprathermal tails, beam-like features, etc.) that deviate from thermal equilibrium. These electron nonthermal deviations provide a local source for whistler-cyclotron and firehose instabilities electromagnetic fluctuations that are commonly observed. We present clear observational evidence that the temperature anisotropy whistler instability threshold, of a nonthermal kappa distribution plasma, marginally bounds solar wind magnetic fluctuations — when the full electron distribution is considered, without regard of separation of the various electron components during slow solar wind periods. Analysis seems to suggest that during slow solar wind periods, collisional effects are dominant. During fast solar wind periods, magnetic fluctuations and solar wind anisotropies are enhanced above the parallel whistler anisotropic threshold boundary and collisional effects are drastically reduced. Preliminary calculations further show that the oblique electron whistler mirror anisotropic instability bounds both the slow and fast solar wind. Regardless of solar wind speed, the solar wind electron thermal anisotropy appears globally bounded by the parallel electron firehose instability for anisotropies Te⊥ / Te|| < 1 indicative of a firehose-stable electron plasma. Preliminary analysis suggests that skew-kappa nonthermal distributions also shows marginally stable threshold boundaries when considering electron heat flux instability thresholds. The results of our analysis suggests that the slow solar wind electron plasma, when considered globally as a single eVDF, is only marginally stable with respect to nonthermal skew kappa distributions and parallel propagating instabilities.

  6. Locust displacing winds in eastern Australia reassessed with observations from an insect monitoring radar

    Science.gov (United States)

    Hao, Zhenhua; Drake, V. Alistair; Sidhu, Leesa; Taylor, John R.

    2017-07-01

    Based on previous investigations, adult Australian plague locusts are believed to migrate on warm nights (with evening temperatures >25 °C), provided daytime flight is suppressed by surface winds greater than the locusts' flight speed, which has been shown to be 3.1 m s-1. Moreover, adult locusts are believed to undertake briefer `dispersal' flights on nights with evening temperature >20 °C. To reassess the utility of these conditions for forecasting locust flight, contingency tests were conducted comparing the nights selected on these bases (predicted nights) for the months of November, January, and March and the nights when locust migration were detected with an insect monitoring radar (actual nights) over a 7-year period. In addition, the wind direction distributions and mean wind directions on all predicted nights and actual nights were compared. Observations at around 395 m above ground level (AGL), the height at which radar observations have shown that the greatest number of locusts fly, were used to determine the actual nights. Tests and comparisons were also made for a second height, 990 m AGL, as this was used in the previous investigation. Our analysis shows that the proposed criteria are successful from predicting migratory flight only in March, when the surface temperature is effective as a predicting factor. Surface wind speed has no predicting power. It is suggested that a strong daytime surface wind speed requirement should not be considered and other meteorological variables need to be added to the requirement of a warm surface temperature around dusk for the predictions to have much utility.

  7. Locust displacing winds in eastern Australia reassessed with observations from an insect monitoring radar

    Science.gov (United States)

    Hao, Zhenhua; Drake, V. Alistair; Sidhu, Leesa; Taylor, John R.

    2017-12-01

    Based on previous investigations, adult Australian plague locusts are believed to migrate on warm nights (with evening temperatures >25 °C), provided daytime flight is suppressed by surface winds greater than the locusts' flight speed, which has been shown to be 3.1 m s-1. Moreover, adult locusts are believed to undertake briefer `dispersal' flights on nights with evening temperature >20 °C. To reassess the utility of these conditions for forecasting locust flight, contingency tests were conducted comparing the nights selected on these bases (predicted nights) for the months of November, January, and March and the nights when locust migration were detected with an insect monitoring radar (actual nights) over a 7-year period. In addition, the wind direction distributions and mean wind directions on all predicted nights and actual nights were compared. Observations at around 395 m above ground level (AGL), the height at which radar observations have shown that the greatest number of locusts fly, were used to determine the actual nights. Tests and comparisons were also made for a second height, 990 m AGL, as this was used in the previous investigation. Our analysis shows that the proposed criteria are successful from predicting migratory flight only in March, when the surface temperature is effective as a predicting factor. Surface wind speed has no predicting power. It is suggested that a strong daytime surface wind speed requirement should not be considered and other meteorological variables need to be added to the requirement of a warm surface temperature around dusk for the predictions to have much utility.

  8. Verification of the ECMWF ensemble forecasts of wind speed against analyses and observations

    DEFF Research Database (Denmark)

    Pinson, Pierre; Hagedorn, Renate

    2012-01-01

    A framework for the verification of ensemble forecasts of near-surface wind speed is described. It is based on existing scores and diagnostic tools, though considering observations from synoptic stations as reference instead of the analysis. This approach is motivated by the idea of having a user......-oriented view of verification, for instance with the wind power applications in mind. The verification framework is specifically applied to the case of ECMWF ensemble forecasts and over Europe. Dynamic climatologies are derived at the various stations, serving as a benchmark. The impact of observational...... uncertainty on scores and diagnostic tools is also considered. The interest of this framework is demonstrated from its application to the routine evaluation of ensemble forecasts and to the assessment of the quality improvements brought in by the recent change in horizontal resolution of the ECMWF ensemble...

  9. Multispacecraft observations of the terrestrial bow shock and magnetopause during extreme solar wind disturbances

    DEFF Research Database (Denmark)

    Tatrallyay, M.; Erdos, G.; Nemeth, Z.

    2012-01-01

    by the interplanetary magnetic field (IMF) component transverse to the solar wind flow. The observed magnetopause crossings could be predicted with a reasonable accuracy (0.1-0.2 RE) by one of the presented models at least. For geosynchronous magnetopause crossings observed by the GOES satellites, (1) the new model...... interplanetary disturbances. The results of a global 3-D MHD model were in good agreement with the Cluster observations on 17 January 2005, but they did not predict the bow shock crossings on 31 October 2003....

  10. Alfvénic turbulence in solar wind originating near coronal hole boundaries: heavy-ion effects?

    Directory of Open Access Journals (Sweden)

    B. Bavassano

    2006-03-01

    Full Text Available The mid-latitude phases of the Ulysses mission offer an excellent opportunity to investigate the solar wind originating near the coronal hole boundaries. Here we report on Alfvénic turbulence features, revealing a relevant presence of in-situ generated fluctuations, observed during the wind rarefaction phase that charaterizes the transition from fast to slow wind. Heavy-ion composition and magnetic field measurements indicate a strict time correspondence of the locally generated fluctuations with 1 the crossing of the interface between fast and slow wind and 2 the presence of strongly underwound magnetic field lines (with respect to the Parker spiral. Recent studies suggest that such underwound magnetic configurations correspond to fast wind magnetic lines that, due to footpoint motions at the Sun, have their inner leg transferred to slow wind and are stretched out by the velocity gradient. If this is a valid scenario, the existence of a magnetic connection across the fast-slow wind interface is a condition that, given the different state of the two kinds of wind, may favour the development of processes acting as local sources of turbulence. We suggest that heavy-ion effects could be responsible of the observed turbulence features.

  11. On the Response of the Ulysses RTG to the Impact of Large SRM-Fragments

    Energy Technology Data Exchange (ETDEWEB)

    Eck, Marshall B.; Mukunda, Meera

    1990-01-01

    Presented at the Seventh Symposium on Space Nuclear Power Systems in Albuquerque, NM, January 7-11, 1990. It will be shown that end-on impacts, which are more likely to occur with Ulysses than with Galileo, will produce greater average fueled clad distortion than was typical of Galileo. Fortunately, the predicted distortions remain well within the Galileo database. It will also be shown that the 2-dimensional calculations which were performed for the Galileo configuration were indeed valid in that application and are also valid for the Ulysses configuration. There are three copies in the file.

  12. Modeling and Observing the Role of Wind-Waves in Titan's Hydrocarbon Seas

    Science.gov (United States)

    Hayes, A. G., Jr.; Soderblom, J. M.; Donelan, M. A.; Barnes, J. W.; Lorenz, R. D.

    2016-12-01

    Oceanography is no longer just an Earth Science. Standing bodies of liquid that interact with both atmospheric and surface reservoirs are known to exist on Titan and are thought to have existed on early Mars. The exchange of heat, moisture, and momentum between lakes/seas and the atmosphere are of fundamental importance to the hydrologic systems of all three bodies. On Earth, surface liquids are almost always disturbed by some form of wave activity. On Titan, however, Cassini observations through the end of the Equinox Mission (12/2010) showed no indication of surface waves. This was intriguing given the predominance of aeolian features at equatorial latitudes and has been attributed to the light winds predicted during the Titan winter. More recently, the previous series of upper limits and non-detections have given way to indications that the expected freshening of winds in northern summer is causing sporadic ruffling of sea surfaces. Specifically, apparent sunglints offset from the geometric specular point have become a common observation by VIMS and transient radar signatures have been observed over the surfaces of both Ligeia Mare and Kraken Mare. SAR images also reveal morphologies consistent with secondary coastlines, most notably Ontario Lacus and Ligeia Mare. This presentation will review Cassini observations of transient surface activity on Titan's Mare and quantitatively describe the implied constraints on sea surface roughness. Assuming that the transient activity is due to wind waves, we can turn the Cassini spacecraft into an anemometer by coupling roughness constraints to a physics-based model of wave generation and propagation in the Titan environment. By determining the fraction of the lake surface that is oriented in a specific geometry, which can be obtained from either nadir RADAR backscatter or VIMS specular reflection measurements, we can determine the driving wind speeds that best match the observations by matching the fraction of the

  13. Surface wind-drifted currents observed by drifting buoys in the East China Sea

    Science.gov (United States)

    Komatsu, K.

    Surface and upper layer currents were observed by drifting GPS buoys in the East China Sea from February to March in 2001 and 2003. Both observations showed that two buoys deployed at the same position 120 nautical miles northwestward from the Kuroshio made different trajectories each other. The buoy drogued at 15m depth drifted northward, indicating the Kuroshio Branch Current extending to the Japan Sea, whose trajectory was properly reproduced by a high resolution 3-D model assimilated to satellite sea level. On the other hand, the buoy without drogue was drawn in eastward to the Kuroshio and its trajectory was not reproduced by the numerical model. In the region where currents were comparatively weak, the no-drogue buoy drifted to the direction which gave good agreement in synoptic time scale with the surface current direction inferred from the Ekman drift using wind data based on QuikSCAT. However the drifting speed of the buoy was over twice faster than 3.5% of the wind speed, indicating the contamination of drifting effects due to wind waves. These results suggested that a small difference of the vertical position of organic/inorganic matters in the surface layer let their future routes change drastically under the multiple drifting effects.

  14. Estimating wind-turbine-caused bird and bat fatality when zero carcasses are observed

    Science.gov (United States)

    Huso, Manuela M.P.; Dalthorp, Daniel; Dail, David; Madsen, Lisa

    2015-01-01

    Many wind-power facilities in the United States have established effective monitoring programs to determine turbine-caused fatality rates of birds and bats, but estimating the number of fatalities of rare species poses special difficulties. The loss of even small numbers of individuals may adversely affect fragile populations, but typically, few (if any) carcasses are observed during monitoring. If monitoring design results in only a small proportion of carcasses detected, then finding zero carcasses may give little assurance that the number of actual fatalities is small. Fatality monitoring at wind-power facilities commonly involves conducting experiments to estimate the probability (g) an individual will be observed, accounting for the possibilities that it falls in an unsearched area, is scavenged prior to detection, or remains undetected even when present. When g  ~0.45. Further, we develop extensions for temporal replication that can inform prior distributions of M and methods for combining information across several areas or time periods. We apply the method to data collected at a wind-power facility where scheduled searches yielded X = 0 raptor carcasses

  15. Estimating wind-turbine-caused bird and bat fatality when zero carcasses are observed.

    Science.gov (United States)

    Huso, Manuela M P; Dalthorp, Dan; Dail, David; Madsen, Lisa

    2015-07-01

    Many wind-power facilities in the United States have established effective monitoring programs to determine turbine-caused fatality rates of birds and bats, but estimating the number of fatalities of rare species poses special difficulties. The loss of even small numbers of individuals may adversely affect fragile populations, but typically, few (if any) carcasses are observed during monitoring. If monitoring design results in only a small proportion of carcasses detected, then finding zero carcasses may give little assurance that the number of actual fatalities is small. Fatality monitoring at wind-power facilities commonly involves conducting experiments to estimate the probability (g) an individual will be observed, accounting for the possibilities that it falls in an unsearched area, is scavenged prior to detection, or remains undetected even when present. When g -0.45. Further, we develop extensions for temporal replication that can inform prior distributions of M and methods for combining information across several areas or time periods. We apply the method to data collected at a wind-power facility where scheduled searches yielded X = 0 raptor carcasses.

  16. Stratosphere and lower mesosphere wind observation and gravity wave activities of the wind field in China using a mobile Rayleigh Doppler lidar

    Science.gov (United States)

    Zhao, Ruocan; Dou, Xiankang; Xue, Xianghui; Sun, Dongsong; Han, Yuli; Chen, Chong; Zheng, Jun; Li, Zimu; Zhou, Anran; Han, Yan; Wang, Guocheng; Chen, Tingdi

    2017-08-01

    Since the mobile Rayleigh Doppler lidar of the University of Science and Technology of China was developed in 2013, more than 100 days of valid nighttime wind data from 15 to 60 km altitude were obtained during recent 3 years. The observation locations cover the northwest (midlatitude) of China: Delingha (37.371°N, 97.374°E), Xinzhou (38.425°N, 112.729°E), and Jiuquan (39.741°N, 98.495°E). Recently, we have extracted perturbations of the wind profiles from the wind field measurements and we have found that inertia gravity waves and mountain waves existed at the same time. The results of wind field and several gravity waves cases are shown in this paper. Typical characteristics of the gravity waves are analyzed in this midlatitude area of China. A 2-D fast Fourier transform of the wind perturbation shows that a dominant stationary wave mode and a downward wave mode exist simultaneously in the spectrum. A band-pass 2-D filter was applied to the spectrum followed by inverse fast Fourier transform to separate inertia gravity waves from stationary mountain waves. The horizontal wavelength is retrieved using hodograph methods, indicating that the inertia waves are generated thousands of kilometers away. Observed mountain waves from a combination of vertical wind and leaned line of sight wind measurements show a small-angle leaned wave front from the horizontal direction. This kind of gravity wave observation of the stratospheric wind field and its wave patterns is rare and significant for the study of atmospheric dynamics.

  17. Real time simulation of nonlinear generalized predictive control for wind energy conversion system with nonlinear observer.

    Science.gov (United States)

    Ouari, Kamel; Rekioua, Toufik; Ouhrouche, Mohand

    2014-01-01

    In order to make a wind power generation truly cost-effective and reliable, an advanced control techniques must be used. In this paper, we develop a new control strategy, using nonlinear generalized predictive control (NGPC) approach, for DFIG-based wind turbine. The proposed control law is based on two points: NGPC-based torque-current control loop generating the rotor reference voltage and NGPC-based speed control loop that provides the torque reference. In order to enhance the robustness of the controller, a disturbance observer is designed to estimate the aerodynamic torque which is considered as an unknown perturbation. Finally, a real-time simulation is carried out to illustrate the performance of the proposed controller. Copyright © 2013 ISA. Published by Elsevier Ltd. All rights reserved.

  18. The Relationship of High-Latitude Thermospheric Wind With Ionospheric Horizontal Current, as Observed by CHAMP Satellite

    Science.gov (United States)

    Huang, Tao; Lühr, Hermann; Wang, Hui; Xiong, Chao

    2017-12-01

    The relationship between high-latitude ionospheric currents (Hall current and field-aligned current) and thermospheric wind is investigated. The 2-D patterns of horizontal wind and equivalent current in the Northern Hemisphere derived from the CHAMP satellite are considered for the first time simultaneously. The equivalent currents show strong dependences on both interplanetary magnetic field (IMF) By and Bz components. However, IMF By orientation is more important in controlling the wind velocity patterns. The duskside wind vortex as well as the antisunward wind in the morning polar cap is more evident for positive By. To better understand their spatial relation in different sectors, a systematic superposed epoch analysis is applied. Our results show that in the dusk sector, the vectors of the zonal wind and equivalent current are anticorrelated, and both of them form a vortical flow pattern for different activity levels. The currents and zonal wind are intensified with the increase of merging electric field. However, on the dawnside, where the relation is less clear, antisunward zonal winds dominate. Plasma drift seems to play a less important role for the wind than neutral forces in this sector. In the noon sector, the best anticorrelation between equivalent current and wind is observed for a positive IMF By component and it is less obvious for negative By. A clear seasonal effect with current intensities increasing from winter to summer is observed in the noon sector. Different from the currents, the zonal wind intensity shows little dependence on seasons. Our results indicate that the plasma drift and the neutral forces are of comparable influence on the zonal wind at CHAMP altitude in the noon sector.

  19. Solar Wind Strahl Observations and Their Implication to the Core-Halo Formation due to Scattering

    Science.gov (United States)

    Vinas, Adolfo F.

    2011-01-01

    A study of the kinetic properties of the strahl electron velocity distribution functions (VDF?s) in the solar wind is presented. This study focuses on the mechanisms that control and regulate the electron VDF?s and the stability of the strahl electrons in the solar wind; mechanisms that are not yet well understood. Various parameters are investigated such as the strahl-electron density, temperature anisotropy, and electron heat-flux. These parameters are used to investigate the stability of the strahl population. The analysis check for whether the strahl electrons are constrained by some instability (e.g., the whistler or KAW instabilities), or are maintained by other types of processes. The electron heat-flux and temperature anisotropy are determined by modeling of the 3D-VDF?s from which the moments properties of the various populations are obtained. The results of this study have profound implication on the current hypothesis about the probable formation of the solar wind halo electrons produced from the scattering of the strahl population. This hypothesis is strengthened by direct observations of the strahl electrons being scattered into the core-halo in an isolated event. The observation implies that the scattering of the strahl is not a continuous process but occurs in bursts in regions where conditions for wave growth providing the scattering are optimum. Sometimes, observations indicate that the strahl component is anisotropic (Tper/Tpal approx. 2). This provides a possible free energy source for the excitation of whistler waves as a possible scattering mechanism, however this condition is not always observed. The study is based on high time resolution data from the Cluster/PEACE electron spectrometer.

  20. Multispectral observations of the Jovian aurora

    Science.gov (United States)

    1992-01-01

    The upper atmospheres of the Earth and the outer planets form a screen on which precipitating charged particles, like the electron beam in a television, trace fleeting, but revealing patterns of visible, ultraviolet, infrared, and x ray emissions that offer valuable clues to processes occurring within the planetary magnetospheres. At Earth, years of in situ measurements, as well as ground based observations, have yielded a picture (still fuzzy) where the interaction of the solar wind with the magnetosphere of the Earth provides a complex path for the storage and release of energy during magnetic substorms; the ultimate manifestation of terrestrial auroral processes. More recent global imaging of substorm events from high above the Earth (greater than 3.5 R(sub e)) by Dynamics Explorer have made a unique contribution towards understanding the global and temporal evolution of such auroral events by providing a morphological perspective and by providing the crucial observational link that allows the separation of spatial and temporal variations inherent in the interpretation of in situ data. A similar role was played by the Hubble Space Telescope (HST) during the recent encounter of Ulysses with Jupiter in helping to define a new paradigm in Jovian auroral physics. The old paradigm portrayed Jupiter's magnetosphere as totally dominated by internal processes (i.e. Io related tori, heavy ions, etc.) where energetic heavy ion precipitation in the inner magnetosphere was solely responsible for the observed auroral phenomena. Ulysses and HST portray a more Earth-like paradigm where electron acceleration in the outer magnetosphere near the boundary with the solar wind plays a distinct role in the formation of auroral hot spots, yet energetic heavy ions also enter into the picture (similar to the role of the energetic ions from the terrestrial ring current during magnetic substorms). These heavy ions as a result of excitation during their transit through the atmosphere

  1. Wind observations from a forested hill: Relating turbulence statistics to surface characteristics in hilly and patchy terrain

    Directory of Open Access Journals (Sweden)

    Lukas Pauscher

    2018-01-01

    Full Text Available This study investigates turbulence characteristics as observed at a 200 m tall mast at a hilly and complex site. It thereby concentrates on turbulence statistics, which are important for the site suitability analysis of a wind turbine. The directional variations in terrain are clearly reflected in the observed turbulence intensities and drag. Integral turbulence statistics showed some variations from their typical flat terrain values. Footprint modelling was used to model the area of effect and to relate the observed turbulence characteristics to the ruggedness and roughness within the estimated fetch area. Among the investigated turbulence quantities, the normalised standard deviation of the wind velocity along the streamlines showed the highest correlation with the effective roughness and ruggedness within the footprint followed by the normalised friction velocity and normalised standard deviation of the vertical wind speed. A differentiation between the effects of roughness and ruggedness was not possible, as forest cover and complex orography are highly correlated at the investigated site. An analysis of turbulence intensity by wind speed indicated a strong influence of atmospheric stability. Stable conditions lead to an overall reduction in turbulence intensity for a wind speed range between approx. 6–12 m s−1 when compared to neutral stratification. The variance of the horizontal wind speed strongly varied over the height range which is typical for a modern wind turbine and was in the order of the differences between different standard turbulence classes for wind turbines.

  2. Tidal signatures of the thermospheric mass density and zonal wind at midlatitude: CHAMP and GRACE observations

    Directory of Open Access Journals (Sweden)

    C. Xiong

    2015-02-01

    Full Text Available By using the accelerometer measurements from CHAMP and GRACE satellites, the tidal signatures of the thermospheric mass density and zonal wind at midlatitudes have been analyzed in this study. The results show that the mass density and zonal wind at southern midlatitudes are dominated by a longitudinal wave-1 pattern. The most prominent tidal components in mass density and zonal wind are the diurnal tides D0 and DW2 and the semidiurnal tides SW1 and SW3. This is consistent with the tidal signatures in the F region electron density at midlatitudes as reported by Xiong and Lühr (2014. These same tidal components are observed both in the thermospheric and ionospheric quantities, supporting a mechanism that the non-migrating tides in the upper atmosphere are excited in situ by ion–neutral interactions at midlatitudes, consistent with the modeling results of Jones Jr. et al. (2013. We regard the thermospheric dynamics as the main driver for the electron density tidal structures. An example is the in-phase variation of D0 between electron density and mass density in both hemispheres. Further research including coupled atmospheric models is probably needed for explaining the similarities and differences between thermospheric and ionospheric tidal signals at midlatitudes.

  3. Observations of magnetospheric substorms occurring with no apparent solar wind/IMF trigger

    Energy Technology Data Exchange (ETDEWEB)

    Henderson, M.G.; Reeves, G.D.; Belian, R.D. [Los Alamos National Lab., NM (United States); Murphree, J.S. [Univ. of Calgary, Alberta (Canada)

    1996-03-01

    An outstanding topic in magnetospheric physics is whether substorms are always externally triggered by disturbances in either the interplanetary magnetic field or solar wind, or whether they can also occur solely as the result of an internal magnetospheric instability. Over the past decade, arguments have been made on both sides of this issue. Horwitz and McPherron have shown examples of substorm onsets which they claimed were not externally triggered. However, as pointed out by Lyons, there are several problems associated with these studies that make their results somewhat inconclusive. In particular, in the McPherron et al. study, fluctuations in the B{sub y} component were not considered as possible triggers. Furthermore, Lyons suggests that the sharp decreases in the AL index during intervals of steady IMF/solar wind, are not substorms at all but rather that they are just enhancements of the convection driven DP2 current system that are often observed to occur during steady magnetospheric convection events. In the present study, we utilize a much more comprehensive dataset (consisting of particle data from the Los Alamos energetic particle detectors at geosynchronous orbit, IMP 8 magnetometer and plasma data, Viking UV auroral imager data, mid-latitude Pi2 pulsation data, ground magnetometer data and ISEE1 magnetic field and energetic particle data) to show as unambiguously as possible that typical substorms can indeed occur in the absence of an identifiable trigger in the solar wind/IMF.

  4. A survey of solar wind conditions at 5 AU: A tool for interpreting solar wind-magnetosphere interactions at Jupiter

    Directory of Open Access Journals (Sweden)

    Robert Wilkes Ebert

    2014-09-01

    Full Text Available We examine Ulysses solar wind and interplanetary magnetic field (IMF observations at 5 AU for two ~13 month intervals during the rising and declining phases of solar cycle 23 and the predicted response of the Jovian magnetosphere during these times. The declining phase solar wind, composed primarily of corotating interaction regions and high-speed streams, was, on average, faster, hotter, less dense, and more Alfvénic relative to the rising phase solar wind, composed mainly of slow wind and interplanetary coronal mass ejections. Interestingly, none of solar wind and IMF distributions reported here were bimodal, a feature used to explain the bimodal distribution of bow shock and magnetopause standoff distances observed at Jupiter. Instead, many of these distributions had extended, non-Gaussian tails that resulted in large standard deviations and much larger mean over median values. The distribution of predicted Jupiter bow shock and magnetopause standoff distances during these intervals were also not bimodal, the mean/median values being larger during the declining phase by ~1 – 4%. These results provide data-derived solar wind and IMF boundary conditions at 5 AU for models aimed at studying solar wind-magnetosphere interactions at Jupiter and can support the science investigations of upcoming Jupiter system missions. Here, we provide expectations for Juno, which is scheduled to arrive at Jupiter in July 2016. Accounting for the long-term decline in solar wind dynamic pressure reported by McComas et al. (2013, Jupiter’s bow shock and magnetopause is expected to be at least 8 – 12% further from Jupiter, if these trends continue.

  5. An OSSE on Mesoscale Model Assimilation of Simulated HIRAD-Observed Hurricane Surface Winds

    Science.gov (United States)

    Albers, Cerese; Miller, Timothy; Uhlhorn, Eric; Krishnamurti, T. N.

    2012-01-01

    The hazards of landfalling hurricanes are well known, but progress on improving the intensity forecasts of these deadly storms at landfall has been slow. Many cite a lack of high-resolution data sets taken inside the core of a hurricane, and the lack of reliable measurements in extreme conditions near the surface of hurricanes, as possible reasons why even the most state-of-the-art forecasting models cannot seem to forecast intensity changes better. The Hurricane Imaging Radiometer (HIRAD) is a new airborne microwave remote sensor for observing hurricanes, and is operated and researched by NASA Marshall Space Flight Center in partnership with the NOAA Atlantic Oceanographic and Meteorological Laboratory/Hurricane Research Division, the University of Central Florida, the University of Michigan, and the University of Alabama in Huntsville. This instrument?s purpose is to study the wind field of a hurricane, specifically observing surface wind speeds and rain rates, in what has traditionally been the most difficult areas for other instruments to study; the high wind and heavy rain regions. Dr. T. N. Krishnamurti has studied various data assimilation techniques for hurricane and monsoon rain rates, and this study builds off of results obtained from utilizing his style of physical initializations of rainfall observations, but obtaining reliable observations in heavy rain regions has always presented trouble to our research of high-resolution rainfall forecasting. Reliable data from these regions at such a high resolution and wide swath as HIRAD provides is potentially very valuable to mesoscale forecasting of hurricane intensity. This study shows how the data assimilation technique of Ensemble Kalman Filtering (EnKF) in the Weather Research and Forecasting (WRF) model can be used to incorporate wind, and later rain rate, data into a mesoscale model forecast of hurricane intensity. The study makes use of an Observing System Simulation Experiment (OSSE) with a simulated

  6. On Lunar Exospheric Column Densities and Solar Wind Access Beyond the Terminator from ROSAT Soft X-ray Observations of Solar Wind Charge Exchange (SWCX)

    Science.gov (United States)

    Collier, M. R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T.; Farrell, W. M.; Fatemi, S.; Hills, H. K.; Hodges, R. R.; Holmstrom, M.; Kuntz, K. D.; Porter, F. S.; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Travnicek, P. M.

    2013-12-01

    We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the antisolar point. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears dominated by exospheric species arising from solar wind implantation, this technique can also monitor how the exosphere varies with solar wind conditions. Now along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed.

  7. A survey of 3He enhancements at 2–20 MeV/nucleon: Ulysses COSPIN/LET

    Directory of Open Access Journals (Sweden)

    C. Tranquille

    2003-06-01

    Full Text Available We present the results of a survey of enhancements in the ratio of 3He/4 He as measured by the COSPIN/LET instrument on board the Ulysses spacecraft in the energy range 2–20 MeV/n. In the context of this study, all ratios of 3He/4 He above 0.05 are considered to be enhanced compared with the solar system value of ~0.0004. Previous studies have shown that enhanced fluxes of 3He are frequently associated with small, impulsive solar flare events in which the observer is well connected to the flare site. These events also often show enrichments in heavy ion composition compared with standard coronal values. Recent attention has also focused on 3He enrichments as evidence for re-acceleration of remnant particle populations that are present in the inner heliosphere following periods of enhanced solar activity. For this study, we have examined the Ulysses data set from launch (October 1990 up to the present, representing a full solar cycle. The spatial coverage extends from 1–5.4 AU in heliocentric distance, and effectively includes the complete range of heliomagnetic latitudes from pole to pole. We have identified 12 periods of enhanced 3He/4 He, occurring at heliocentric distances out to 5 AU, and heliolatitudes up to 48°. We investigate the characteristics of the events, many of which last for several days, in order to establish possible origins.Key words. Interplanetary physics (energetic particles – Solar physics, astrophysics and astronomy (energetic particles; flares and mass ejections

  8. A survey of 3He enhancements at 2–20 MeV/nucleon: Ulysses COSPIN/LET

    Directory of Open Access Journals (Sweden)

    M. Y. Hofer

    Full Text Available We present the results of a survey of enhancements in the ratio of 3He/4 He as measured by the COSPIN/LET instrument on board the Ulysses spacecraft in the energy range 2–20 MeV/n. In the context of this study, all ratios of 3He/4 He above 0.05 are considered to be enhanced compared with the solar system value of ~0.0004. Previous studies have shown that enhanced fluxes of 3He are frequently associated with small, impulsive solar flare events in which the observer is well connected to the flare site. These events also often show enrichments in heavy ion composition compared with standard coronal values. Recent attention has also focused on 3He enrichments as evidence for re-acceleration of remnant particle populations that are present in the inner heliosphere following periods of enhanced solar activity. For this study, we have examined the Ulysses data set from launch (October 1990 up to the present, representing a full solar cycle. The spatial coverage extends from 1–5.4 AU in heliocentric distance, and effectively includes the complete range of heliomagnetic latitudes from pole to pole. We have identified 12 periods of enhanced 3He/4 He, occurring at heliocentric distances out to 5 AU, and heliolatitudes up to 48°. We investigate the characteristics of the events, many of which last for several days, in order to establish possible origins.Key words. Interplanetary physics (energetic particles – Solar physics, astrophysics and astronomy (energetic particles; flares and mass ejections

  9. MAVEN observations of the Mars upper atmosphere, ionosphere, and solar wind interactions

    Science.gov (United States)

    Jakosky, Bruce M.

    2017-09-01

    The Mars Atmosphere and Volatile Evolution (MAVEN) mission to Mars has been operating in orbit for more than a full Martian year. Observations are dramatically changing our view of the Mars upper atmosphere system, which includes the upper atmosphere, ionosphere, coupling to the lower atmosphere, magnetosphere, and interactions with the Sun and the solar wind. The data are allowing us to understand the processes controlling the present-day structure of the upper atmosphere and the rates of escape of gas to space. These will tell us the role that escape to space has played in the evolution of the Mars atmosphere and climate.

  10. MHD Model Results of Solar Wind Plasma Interaction with Mars and Comparison with MAVEN Observations

    Science.gov (United States)

    Ma, Y. J.; Russell, C. T.; Nagy, A. F.; Toth, G.; Halekas, J. S.; Connerney, J. E. P.; Espley, J. R.; Mahaffy, P. R.

    2015-01-01

    The crustal remnant field on Mars rotates constantly with the planet, varying the magnetic field configuration interacting with the solar wind. It has been found that ion loss rates slowly vary with the subsolar longitude, anticorrelating with the intensity of the dayside crustal field source, with some time delay, using a time-dependent multispecies MHD model. In this study, we investigate in detail how plasma properties are influenced locally by the crustal field and its rotation. Model results will be compared in detail with plasma observations from MAVEN.

  11. Interaction of solar wind with Mercury and its magnetic field. [as observed by Mariner 10 space probe

    Science.gov (United States)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1976-01-01

    A brief review is presented of magnetic field and solar wind electron observations by Mariner 10 spacecraft. The intrinsic magnetic field of the planet Mercury and the implications of such a field for the planetary interior are also discussed.

  12. PMSE and wind profiles from observations above EISCAT Tromsø site

    Science.gov (United States)

    Mann, Ingrid; Nozawa, Satonori; Haeggstroem, Ingemar; Tjulin, Anders; Dalin, Peter; Hall, Chris; Anyairo, Charles; Rostami, Sina

    2017-04-01

    One of the processes that are linked to the entry of cosmic dust in atmosphere is the formation of Polar Mesospheric Summer Echoes (PMSE). PMSE are strong radar echoes that are observed in the polar summer mesosphere. They are caused by spatial variations in the plasma refractive index which arise in the presence of electrically charged ice particles. The ice particles that are linked to PMSE are often below the optically observable size range and are assumed to form by water ice condensing onto meteoric smoke particles at around 80 to 90 km altitude. The atmosphere at PMSE altitude is influenced by solar radiative forcing from above and gravity waves from below, and while ionization is small, it is highly variable due to a number of different processes. A straightforward quantitative description of the physics leading to PMSE formation is at present still missing. With one of the first tri-static PMSE observations with the EISCAT VHF radar we found signs of wind shear in PMSE. The observations suggest that the PMSE contains sublayers that move in different directions horizontally, and this points to Kelvin-Helmholtz instability possibly playing a role in PMSE process. We compare the EISCAT observations to wind observations carried with other radar at the same location and discuss implications for future observations. We acknowledge Chris Meek and Alan Manson who provided MF radar data. EISCAT is an international association supported by research organizations in Norway (NFR), Sweden (VR), Finland (SA), Japan (NIPR and STEL), China (CRIPR), and the United Kingdom (NERC); data are available under http://www. eiscat.se/madrigal/.

  13. High-resolution forecasting of wind power generation with regime switching models and off-site observations

    Energy Technology Data Exchange (ETDEWEB)

    Trombe, P.-J.; Pinson, P.

    2012-11-01

    This work considered the probabilistic forecasting of wind power generation from a single wind farm, over very short lead times (i.e., 15 minutes). Realistic assumptions were made regarding the online availability of wind data in the current wind power context, meaning that neither wind measurements nor wind forecasts are available for the temporal resolution of interest. The sole data that are used consist of on-site observations of wind power generation, along with corresponding observations from the two nearest wind farms located in a radius of 50 km. Focus is placed on the most recent approaches from the wind power forecasting literature, including regime-switching models, the use of off-site predictors and a new predictive distribution. The predictive performances of these approaches and their associated models are compared against one another to assess their respective merits. Eventually, combinations of these approaches are proposed and proved to generate improved wind power forecasts. Through an application with three wind farms in Ireland, we show that regime-switching models for which the sequence of regime is unobservable (i.e., Markov-Switching) generate more accurate point forecasts, better calibrated and sharper conditional densities, than single regime or other regime-switching models for which the regimes are observable. Furthermore, gains in wind power predictability can be increased by taking advantage of off-site information when available or using a more appropriate predictive distribution such as the GLN distribution. The highest gains were obtained by using simultaneously off-site observation and the GLN distribution. The superior predictive power of Markov-Switching models is interesting in two aspects. First, because this type of models is rather generic and thus non site-dependent, requiring very little expert knowledge to be tuned. It confirms the potential shown for offshore applications. Second, because Markov-Switching models assume the

  14. Long-term Behaviour Of Venus Winds At Cloud Level From Virtis/vex Observations

    Science.gov (United States)

    Hueso, Ricardo; Peralta, J.; Sánchez-Lavega, A.; Pérez-Hoyos, S.; Piccioni, G.; Drossart, P.

    2009-09-01

    The Venus Express (VEX) mission has been in orbit to Venus for more than three years now. The VIRTIS instrument onboard VEX observes Venus in two channels (visible and infrared) obtaining spectra and multi-wavelength images of the planet. Images in the ultraviolet range are used to study the upper cloud at 66 km while images in the infrared (1.74 μm) map the opacity of the lower cloud deck at 48 km. Here we present an analysis of the overall dynamics of Venus’ atmosphere at both levels using observations that cover a large fraction of the VIRTIS dataset. We will present our latest results concerning the zonal winds, the overall stability in the lower cloud deck motions and the variability in the upper cloud. Meridional winds are also observed in the upper and lower cloud in the UV and IR images obtained with VIRTIS. While the upper clouds present a net meridional motion consistent with the upper branch of a Hadley cell the lower cloud present more irregular, variable and less intense motions in the meridional direction. Acknowledgements This work has been funded by Spanish MEC AYA2006-07735 with FEDER support and Grupos Gobierno Vasco IT-464-07. RH acknowledges a "Ramón y Cajal” contract from MEC.

  15. Surface river plume in a large lake under wind forcing: Observations and laboratory experiments

    Science.gov (United States)

    Demchenko, Natalia; He, Cheng; Rao, Yerubandi R.; Valipour, Reza

    2017-10-01

    Observations of a small riverine plume (Grand River, ON) in the nearshore zones of Lake Erie were analyzed to describe its spatial variability and its thickness under different wind forcing conditions during late spring of 2012. Observational results reveal a well-marked frontal region in the vicinity of the river mouth, causing the plume to discharge into the lake in the surface layers (positive buoyant). Wind driven alongshore currents at the mid-depth had speeds of 2-9 cm/s, in comparison to those in the cross-shore 3-6 cm/s, which transported the plume along the shore during the measurement period. Series of laboratory experiments were conducted to obtain the propagation speed (U) of the buoyant plume in terms of buoyancy anomaly (Ba), Richardson number (Ri), dimensionless time (t‧), and aspect ratio (A). Based on our experiments, we developed two non-dimensional relationships describing the speed of propagation (U) as U/Ba1/2 = 8 Ri-1/2t‧1/3A and the plume thickness (h) as h/H = 0.8 Ri-1/4t‧1/2A in the water depth (H), which are in agreement with field observations.

  16. Characterization of the Turbulent Magnetic Integral Length in the Solar Wind: From 0.3 to 5 Astronomical Units

    Science.gov (United States)

    Ruiz, M. E.; Dasso, S.; Matthaeus, W. H.; Weygand, J. M.

    2014-10-01

    The solar wind is a structured and complex system, in which the fields vary strongly over a wide range of spatial and temporal scales. As an example, the turbulent activity in the wind affects the evolution in the heliosphere of the integral turbulent scale or correlation length [ λ], usually associated with the breakpoint in the turbulent-energy spectrum that separates the inertial range from the injection range. This large variability of the fields demands a statistical description of the solar wind. We study the probability distribution function (PDF) of the magnetic-autocorrelation lengths observed in the solar wind at different distances from the Sun. We used observations from the Helios, ACE, and Ulysses spacecraft. We distinguished between the usual solar wind and one of its transient components (interplanetary coronal mass ejections, ICMEs), and also studied solar-wind samples with low and high proton beta [βp]. We find that in the last three regimes the PDF of λ is a log-normal function, consistent with the multiplicative and nonlinear processes that take place in the solar wind, the initial λ (before the Alfvénic point) being larger in ICMEs.

  17. Wind-Driven Particle Mobility on Mars: Insights from MER Observations

    Science.gov (United States)

    Sullivan, R.; Arvidson, R.; Bell, J. F.; Geissler, P.; Golombek, M.; Greeley, R.; Herkenhoff, K.; Johnson, J.; Thompson, S.; Whelley, P.

    2007-12-01

    High-resolution images from MOC and HiRISE reveal numerous small, linear, light-toned bedforms in settings all across Mars. These features represent one of the most abundant aeolian feature types on the planet, yet their nature and origin remain uncertain. Larger, dark-toned features have been identified confidently as dunes from their morphologies; they presumably are relatively depleted of dust and some therefore could be currently active, but only minor surface changes to a small number of dunes have been reported. There have been no reports of changes to any of the numerous light-toned bedforms. It is problematic that winds responsible for frequently raising dust do not seem to significantly affect bedforms that very likely are composed of (more easily-entrained) sand-sized particles. Here we consider factors other than wind frequency that control bedform mobility across Mars, applying observations from MER traverses at Gusev and Meridiani Planum. (1) MI images show that surface dust at Gusev (and likely elsewhere across Mars) typically occurs as extended, fragile aggregates that should be far easier to entrain than mono-particle "dust"-sized grains. (2) Light-toned bedforms investigated at Gusev are coarse-grained ripples (i.e., bedforms with coarse grains mantling finer-grained, sandy interiors). Currently they are crusted and dust-covered. We suggest that the numerous small, linear, light-toned bedforms seen in high resolution orbital images are coarse-grained ripples also. Although such ripples are much less familiar on Earth compared with ripples and dunes having unimodal particle size-frequencies, we suggest this is partly due to the lack of free quartz on Mars available for contributing to an abundant, durable, very well-sorted sediment supply for saltation. Poorly-sorted debris is organized by wind into relatively slow-moving coarse- grained ripples, so in the absence of quartz, we speculate that coarse-grained ripples should be relatively more common

  18. Knowledge of coronal heating and solar-wind acceleration obtained from observations of the solar wind near 1 AU

    Science.gov (United States)

    Neugebauer, M.

    1992-01-01

    Clues to the nature of the mechanisms responsible for heating the corona and accelerating the solar wind can be obtained by contrasting the properties of the quasi-stationary and transient states of the solar wind. Substantial differences exist in the proton temperatures and anisotropies, the entropy, the field strength, the Alfvenicity of fluctuations in the field, the distribution of MHD discontinuities, and the helium abundance of the two types of flow. Those differences are displayed as a function of the solar wind speed. Several signals of wave acceleration can be found in the data for quasi-stationary flows. The relatively smooth velocity dependences of proton temperature, helium abundance, and frequency of occurrence of rotational discontinuities suggest that the acceleration mechanisms for flow from coronal holes, coronal streamers, and the quasi-stationary low-speed flows between them may be basically the same, differing only in degree.

  19. The Indian Summer Monsoon onset revisited: new approach based on the analysis of historical wind observations

    Science.gov (United States)

    Ordoñez, Paulina; Gallego, David; Ribera, Pedro; Peña-Ortiz, Cristina; Garcia-Herrera, Ricardo; Vega, Inmaculada; Gómez, Francisco de Paula

    2016-04-01

    The Indian Summer Monsoon onset is one of the meteorological events most anticipated in the world. Due to its relevance for the population, the India Meteorological Department has dated the onset over the southern tip of the Indian Peninsula (Kerala) since 1901. The traditional method to date the onset was based in the judgment of skilled meteorologist and because of this, the method was considered subjective and not adequate for the study of long-term changes in the onset. A new method for determining the monsoon onset based solely on objective criteria has been in use since 2006. Unfortunately, the new method relies -among other variables- on OLR measurements. This requirement impedes the construction of an objective onset series before the satellite era. An alternative approach to establish the onset by objective methods is the use of the wind field. During the last decade, some works have demonstrated that the changes in the wind direction in some areas of the Indian Ocean can be used to determine the monsoon onset rather precisely. However, this method requires precise wind observations over a large oceanic area which has limited the periods covered for such kind of indices to those of the reanalysis products. In this work we present a new approach to track the Indian monsoon onset based solely on historical wind direction measurements taken onboard ships. Our new series provides an objective record of the onset since the last decade of the 19th century and perhaps more importantly, it can incorporate any new historical wind record not yet known in order to extend the series length. The new series captures quite precisely the rapid precipitation increase associated to the monsoon onset, correlates well with previous approaches and it is robust against anomalous (bogus) onsets. Although no significant trends in the onset date were detected, a tendency to later than average onsets during the 1900-1925 and 1970-1990 periods and earlier than average onsets between

  20. Lidar observations of wind- and wave-driven morphological evolution of coastal foredunes

    Science.gov (United States)

    Spore, N.; Brodie, K. L.; Kershner, C. M.

    2016-02-01

    Coastal foredunes are continually evolving geomorphic features that are slowly built up by wind-blown sand and rapidly eroded during storms by large waves and swash. Landward aeolian transport removes sediment from the active beach and surf-zone, trapping it in the dune, where as coastal erosion both removes sediment from the dune and can decrease the overall fetch and sediment supply available to the dune. Understanding how wave and wind-driven process interact with each other and the dune-beach system itself is a critical component of improving predictions of coastal evolution. To investigate these processes, two 50 m alongshore by 25 m cross-shore patches of dune along an open coast beach fronting the Atlantic Ocean in Duck, NC were scanned with a high resolution terrestrial lidar scanner ( 5000 points per m^2) every three weeks over the last year to observe detailed morphological evolution of the dune and upper beach. Sequential scans were co-registered to each other using fixed objects in the field of view, significantly increasing precision and accuracy of the observations. The north study site featured a 7.5 m tall scarped foredune system, where as the southern study site featured a 6 m tall, hummocky, prograding foredune. Initial analyses show large accretion events on the southern prograding site. For example, during one three week period in February, portions of the site accreted over 40 cm. In contrast, during the same three week period at the northern site (less than 1 km away), response was alongshore variable with erosion and accretion of roughly 10 cm on the foredune face. Further analysis will focus on separating wind vs. wave driven evolution of these sites. Funded by the USACE Coastal Inlets Research Program.

  1. Rosetta and Mars Express observations of the influence of high solar wind pressure on the Martian plasma environment

    Directory of Open Access Journals (Sweden)

    N. J. T. Edberg

    2009-12-01

    Full Text Available We report on new simultaneous in-situ observations at Mars from Rosetta and Mars Express (MEX on how the Martian plasma environment is affected by high pressure solar wind. A significant sharp increase in solar wind density, magnetic field strength and turbulence followed by a gradual increase in solar wind velocity is observed during ~24 h in the combined data set from both spacecraft after Rosetta's closest approach to Mars on 25 February 2007. The bow shock and magnetic pileup boundary are coincidently observed by MEX to become asymmetric in their shapes. The fortunate orbit of MEX at this time allows a study of the inbound boundary crossings on one side of the planet and the outbound crossings on almost the opposite side, both very close to the terminator plane. The solar wind and interplanetary magnetic field (IMF downstream of Mars are monitored through simultaneous measurements provided by Rosetta. Possible explanations for the asymmetries are discussed, such as crustal magnetic fields and IMF direction. In the same interval, during the high solar wind pressure pulse, MEX observations show an increased amount of escaping planetary ions from the polar region of Mars. We link the high pressure solar wind with the observed simultaneous ion outflow and discuss how the pressure pulse could also be associated with the observed boundary shape asymmetry.

  2. Rosetta and Mars Express observations of the influence of high solar wind pressure on the Martian plasma environment

    Directory of Open Access Journals (Sweden)

    N. J. T. Edberg

    2009-12-01

    Full Text Available We report on new simultaneous in-situ observations at Mars from Rosetta and Mars Express (MEX on how the Martian plasma environment is affected by high pressure solar wind. A significant sharp increase in solar wind density, magnetic field strength and turbulence followed by a gradual increase in solar wind velocity is observed during ~24 h in the combined data set from both spacecraft after Rosetta's closest approach to Mars on 25 February 2007. The bow shock and magnetic pileup boundary are coincidently observed by MEX to become asymmetric in their shapes. The fortunate orbit of MEX at this time allows a study of the inbound boundary crossings on one side of the planet and the outbound crossings on almost the opposite side, both very close to the terminator plane. The solar wind and interplanetary magnetic field (IMF downstream of Mars are monitored through simultaneous measurements provided by Rosetta. Possible explanations for the asymmetries are discussed, such as crustal magnetic fields and IMF direction. In the same interval, during the high solar wind pressure pulse, MEX observations show an increased amount of escaping planetary ions from the polar region of Mars. We link the high pressure solar wind with the observed simultaneous ion outflow and discuss how the pressure pulse could also be associated with the observed boundary shape asymmetry.

  3. Multi-wavelength observations of pulsar wind nebulae and composite supernova remnants

    Science.gov (United States)

    Temim, Tea

    Multi-wavelength studies of pulsar wind nebulae (PWNe) and supernova remnants (SNRs) lead to a better understanding of their evolutionary development, the interaction of supernovae (SNe) and pulsar winds with their surroundings, and nucleosynthesis and production and processing of dust grains by SNe. PWNe and composite supernova remnants, in particular, are unique laboratories for the study of the energetic pulsar winds, particle injection processes, and the impact of PWNe on the evolving SNR. They provide information on SNR shock properties, densities and temperatures, and the chemical composition and the ionization state of the material ejected by SNe. SNRs also serve as laboratories for the study of dust production and processing in SNe. While X-ray observations yield important information about the SN progenitor, hot gas properties, SN explosion energy, and the surrounding interstellar medium (ISM), the IR can provide crucial information about the faint non-thermal emission, continuum emission from dust, and forbidden line emission from SN ejecta. Combining observations at a wide range of wavelengths provides a more complete picture of the SNR development and helps better constrain current models describing a SNR's evolution and its impact on the surrounding medium. This thesis focuses on a multi-wavelength study of PWNe in various stages of their evolution and investigates their interaction with the expanding SN ejecta and dust and the SNR reverse shock. The study of these interactions can provide important information on the SNR properties that may otherwise be unobservable. The work in this thesis has been carried out under the supervision of Patrick Slane at the Harvard-Smithsonian Center for Astrophysics, and Charles E. Woodward and Rebert D. Gehrz at the University of Minnesota. The first part of the thesis summarizes the evolution and observational properties of SNRs and PWNe, with a focus on the evolution of young PWNe that are sweeping up inner SN

  4. Integrating Wind Profiling Radars and Radiosonde Observations with Model Point Data to Develop a Decision Support Tool to Assess Upper-Level Winds for Space Launch

    Science.gov (United States)

    Bauman, William H., III; Flinn, Clay

    2013-01-01

    On the day-of-launch, the 45th Weather Squadron (45 WS) Launch Weather Officers (LWOs) monitor the upper-level winds for their launch customers to include NASA's Launch Services Program and NASA's Ground Systems Development and Operations Program. They currently do not have the capability to display and overlay profiles of upper-level observations and numerical weather prediction model forecasts. The LWOs requested the Applied Meteorology Unit (AMU) develop a tool in the form of a graphical user interface (GUI) that will allow them to plot upper-level wind speed and direction observations from the Kennedy Space Center (KSC) 50 MHz tropospheric wind profiling radar, KSC Shuttle Landing Facility 915 MHz boundary layer wind profiling radar and Cape Canaveral Air Force Station (CCAFS) Automated Meteorological Processing System (AMPS) radiosondes, and then overlay forecast wind profiles from the model point data including the North American Mesoscale (NAM) model, Rapid Refresh (RAP) model and Global Forecast System (GFS) model to assess the performance of these models. The AMU developed an Excel-based tool that provides an objective method for the LWOs to compare the model-forecast upper-level winds to the KSC wind profiling radars and CCAFS AMPS observations to assess the model potential to accurately forecast changes in the upperlevel profile through the launch count. The AMU wrote Excel Visual Basic for Applications (VBA) scripts to automatically retrieve model point data for CCAFS (XMR) from the Iowa State University Archive Data Server (http://mtarchive.qeol.iastate.edu) and the 50 MHz, 915 MHz and AMPS observations from the NASA/KSC Spaceport Weather Data Archive web site (http://trmm.ksc.nasa.gov). The AMU then developed code in Excel VBA to automatically ingest and format the observations and model point data in Excel to ready the data for generating Excel charts for the LWO's. The resulting charts allow the LWOs to independently initialize the three models 0

  5. Low-frequency magnetic field fluctuations in Venus' solar wind interaction region: Venus Express observations

    Directory of Open Access Journals (Sweden)

    L. Guicking

    2010-04-01

    Full Text Available We investigate wave properties of low-frequency magnetic field fluctuations in Venus' solar wind interaction region based on the measurements made on board the Venus Express spacecraft. The orbit geometry is very suitable to investigate the fluctuations in Venus' low-altitude magnetosheath and mid-magnetotail and provides an opportunity for a comparative study of low-frequency waves at Venus and Mars. The spatial distributions of the wave properties, in particular in the dayside and nightside magnetosheath as well as in the tail and mantle region, are similar to observations at Mars. As both planets do not have a global magnetic field, the interaction process of the solar wind with both planets is similar and leads to similar instabilities and wave structures. We focus on the spatial distribution of the wave intensity of the fluctuating magnetic field and detect an enhancement of the intensity in the dayside magnetosheath and a strong decrease towards the terminator. For a detailed investigation of the intensity distribution we adopt an analytical streamline model to describe the plasma flow around Venus. This allows displaying the evolution of the intensity along different streamlines. It is assumed that the waves are generated in the vicinity of the bow shock and are convected downstream with the turbulent magnetosheath flow. However, neither the different Mach numbers upstream and downstream of the bow shock, nor the variation of the cross sectional area and the flow velocity along the streamlines play probably an important role in order to explain the observed concentration of wave intensity in the dayside magnetosheath and the decay towards the nightside magnetosheath. But, the concept of freely evolving or decaying turbulence is in good qualitative agreement with the observations, as we observe a power law decay of the intensity along the streamlines. The observations support the assumption of wave convection through the magnetosheath, but

  6. First wind shear observation in PMSE with the tristatic EISCAT VHF radar

    Science.gov (United States)

    Mann, I.; Häggström, I.; Tjulin, A.; Rostami, S.; Anyairo, C. C.; Dalin, P.

    2016-11-01

    The Polar Summer Mesosphere has the lowest temperatures that occur in the entire Earth system. Water ice particles below the optically observable size range participate there in the formation of strong radar echoes (Polar Mesospheric Summer Echoes, PMSE). To study PMSE we carried out observations with the European Incoherent Scatter (EISCAT) VHF and EISCAT UHF radar simultaneously from a site near Tromsø (69.58°N, 19.2272°E) and observed VHF backscattering also with the EISCAT receivers in Kiruna (67.86°N, 20.44°E) and Sodankylä (67.36°N, 26.63°E). This is one of the first tristatic measurements with EISCAT VHF, and we therefore describe the observations and geometry in detail. We present observations made on 26 June 2013 from 7:00 to 13:00 h UT where we found similar PMSE patterns with all three VHF receivers and found signs of wind shear in PMSE. The observations suggest that the PMSE contains sublayers that move in different directions horizontally, and this points to Kelvin-Helmholtz instability possibly playing a role in PMSE formation. We find no signs of PMSE in the UHF data. The electron densities that we derive from observed incoherent scatter at UHF are at PMSE altitudes close to the noise level but possibly indicate reduced electron densities directly above the PMSE.

  7. Observation-based parameterization of air-sea fluxes in terms of wind speed and atmospheric stability under low-to-moderate wind conditions

    Science.gov (United States)

    Zou, Zhongshui; Zhao, Dongliang; Liu, Bin; Zhang, Jun A.; Huang, Jian

    2017-05-01

    This study explores the behavior of the exchange coefficients for wind stress (CD), sensible heat flux (CH), and water vapor flux (CE) as functions of surface wind speed (U10) and atmospheric stability using direct turbulent flux measurements obtained from a platform equipped with fast-response turbulence sensors in a low-to-moderate wind region. Turbulent fluxes are calculated using the eddy-correlation method with extensive observations. The total numbers of quality-controlled 30 min flux runs are 12,240, 5813, and 5637 for estimation of CD, CH, and CE, respectively. When adjusted to neutral stability using the Monin-Obukhov similarity theory (MOST), we found that CDN, CHN, and CEN decrease with neutral-adjusted wind speed when wind speed is less than 5 m/s. CDN is constant over the range 5 m/s 12 m/s. In contrast, CHN and CEN exhibit no clear dependence on wind speed and are generally constant, with mean values of 0.96 × 10-3 and 1.2 × 10-3, respectively. This behavior of neutral exchange coefficients is consistent with the findings of previous studies. We also found that CDN under offshore winds is generally greater than that under onshore wind conditions, which is ascribed to the younger wind waves present due to the shorter fetch in the former case. However, this behavior is not exhibited by CHN or CEN. The original CD, CH, and CE values without MOST adjustment are also investigated to develop a new parameterization based on wind speed and stability. Three stability parameters are tested, including the bulk Richardson number, stability as defined in COARE 3.0, and a simplified Richardson number using the Charnock parameter. This new parameterization is free of MOST and the associated self-correlation. Compared with previous studies and COARE 3.0 results, the new parameterization using the simplified Richardson number performs well, with an increased correlation coefficient and reduction of root-mean-square error and bias.

  8. Observation of turbulent intermittency scaling with magnetic helicity in an MHD plasma wind tunnel.

    Science.gov (United States)

    Schaffner, D A; Wan, A; Brown, M R

    2014-04-25

    The intermittency in turbulent magnetic field fluctuations has been observed to scale with the amount of magnetic helicity injected into a laboratory plasma. An unstable spheromak injected into the MHD wind tunnel of the Swarthmore Spheromak Experiment displays turbulent magnetic and plasma fluctuations as it relaxes into a Taylor state. The level of intermittency of this turbulence is determined by finding the flatness of the probability distribution function of increments for magnetic pickup coil fluctuations B˙(t). The intermittency increases with the injected helicity, but spectral indices are unaffected by this variation. While evidence is provided which supports the hypothesis that current sheets and reconnection sites are related to the generation of this intermittent signal, the true nature of the observed intermittency remains unknown.

  9. Statistics of counter-streaming solar wind suprathermal electrons at solar minimum: STEREO observations

    Directory of Open Access Journals (Sweden)

    B. Lavraud

    2010-01-01

    Full Text Available Previous work has shown that solar wind suprathermal electrons can display a number of features in terms of their anisotropy. Of importance is the occurrence of counter-streaming electron patterns, i.e., with "beams" both parallel and anti-parallel to the local magnetic field, which is believed to shed light on the heliospheric magnetic field topology. In the present study, we use STEREO data to obtain the statistical properties of counter-streaming suprathermal electrons (CSEs in the vicinity of corotating interaction regions (CIRs during the period March–December 2007. Because this period corresponds to a minimum of solar activity, the results are unrelated to the sampling of large-scale coronal mass ejections, which can lead to CSE owing to their closed magnetic field topology. The present study statistically confirms that CSEs are primarily the result of suprathermal electron leakage from the compressed CIR into the upstream regions with the combined occurrence of halo depletion at 90° pitch angle. The occurrence rate of CSE is found to be about 15–20% on average during the period analyzed (depending on the criteria used, but superposed epoch analysis demonstrates that CSEs are preferentially observed both before and after the passage of the stream interface (with peak occurrence rate >35% in the trailing high speed stream, as well as both inside and outside CIRs. The results quantitatively show that CSEs are common in the solar wind during solar minimum, but yet they suggest that such distributions would be much more common if pitch angle scattering were absent. We further argue that (1 the formation of shocks contributes to the occurrence of enhanced counter-streaming sunward-directed fluxes, but does not appear to be a necessary condition, and (2 that the presence of small-scale transients with closed-field topologies likely also contributes to the occurrence of counter-streaming patterns, but only in the slow solar wind prior to

  10. On lunar exospheric column densities and solar wind access beyond the terminator from ROSAT soft X-ray observations of solar wind charge exchange

    Science.gov (United States)

    Collier, Michael R.; Snowden, S. L.; Sarantos, M.; Benna, M.; Carter, J. A.; Cravens, T. E.; Farrell, W. M.; Fatemi, S.; Hills, H. Kent; Hodges, R. R.; Holmström, M.; Kuntz, K. D.; Porter, F. Scott; Read, A.; Robertson, I. P.; Sembay, S. F.; Sibeck, D. G.; Stubbs, T. J.; Travnicek, P.; Walsh, B. M.

    2014-07-01

    We analyze the Röntgen satellite (ROSAT) position sensitive proportional counter soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges: two 19° wedges (one north and one south) 13-32° off the terminator toward the dark side and one wedge 38° wide centered on the antisolar direction. The radial profiles of both the north and the south wedges show significant limb brightening that is absent in the 38° wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears to be dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now, along with Mars, Venus, and Earth, the Moon represents another solar system body at which SWCX has been observed.

  11. Observation of the Starting and Low Speed Behavior of Small Horizontal Axis Wind Turbine

    Directory of Open Access Journals (Sweden)

    Sikandar Khan

    2014-01-01

    Full Text Available This paper describes the starting behavior of small horizontal axis wind turbines at high angles of attack and low Reynolds number. The unfavorable relative wind direction during the starting time leads to low starting torque and more idling time. Wind turbine models of sizes less than 5 meters were simulated at wind speed range of 2 m/s to 5 m/s. Wind turbines were modeled in Pro/E and based on the optimized designs given by MATLAB codes. Wind turbine models were simulated in ADAMS for improving the starting behavior. The models with high starting torques and less idling times were selected. The starting behavior was successfully improved and the optimized wind turbine models were able to produce more starting torque even at wind speeds less than 5 m/s.

  12. Turbulence observations in the Gulf of Trieste under moderate wind forcing and different water column stratification

    Science.gov (United States)

    Marcello Falcieri, Francesco; Kantha, Lakshmi; Benetazzo, Alvise; Bergamasco, Andrea; Bonaldo, Davide; Barbariol, Francesco; Malačič, Vlado; Sclavo, Mauro; Carniel, Sandro

    2016-03-01

    The oceanographic campaign CARPET2014 (Characterizing Adriatic Region Preconditionig EvenTs), (30 January-4 February 2014) collected the very first turbulence data in the Gulf of Trieste (northern Adriatic Sea) under moderate wind (average wind speed 10 m s-1) and heat flux (net negative heat flux ranging from 150 to 400 W m-2). Observations consisted of 38 CTD (Conductivity, Temperature, Depth) casts and 478 microstructure profiles (grouped into 145 ensembles) with three sets of yoyo casts, each lasting for about 12 consecutive hours. Averaging closely repeated casts, such as the ensembles, can lead to a smearing effect when in the presence of a vertical density structure with strong interfaces that can move up or down between subsequent casts under the influence of tides and internal waves. In order to minimize the smearing effect of such displacements on mean quantities, we developed an algorithm to realign successive microstructure profiles to produce sharper and more meaningful mean profiles of measured turbulence parameters. During the campaign, the water column in the gulf evolved from well-mixed to stratified conditions due to Adriatic waters intruding at the bottom along the gulf's south-eastern coast. We show that during the warm and relatively dry winter, the water column in the Gulf of Trieste, even under moderate wind forcing, was not completely mixed due to the influence of bottom waters intruding from the open sea. Inside the gulf, two types of water intrusions were found during yoyo casts: one coming from the northern coast of the Adriatic Sea (i.e. cooler, fresher and more turbid) and one coming from the open sea in front of the Po Delta (i.e. warmer, saltier and less turbid). The two intrusions had different impacts on turbulence kinetic energy dissipation rate profiles. The former, with high turbidity, acted as a barrier to wind-driven turbulence, while the latter, with low sediment concentrations and a smaller vertical density gradient, was not

  13. Estimating atmospheric stability from observations and correcting wind shear models accordingly

    NARCIS (Netherlands)

    Holtslag, M.C.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.

    2014-01-01

    Atmospheric stability strongly influences wind shear and thus has to be considered when performing load calculations for wind turbine design. Numerous methods exist however for obtaining stability in terms of the Obukhov length L as well as for correcting the logarithmic wind profile. It is

  14. Observed Wind Speed at Weather Station and Heat Transfer Coefficient of External Surface of the Building in Summer and Winter

    OpenAIRE

    小林, 定教; コバヤシ, サダノリ; Sadanori, KOBAYASHI

    1994-01-01

    The heat transfer coefficient of the external surface of the building used for thermal load calculations was proposed by Dr. Watanabe et at. in about 1934. In those days the main purpose of studies focused on heating; recently calculations in respect to cooling have been increasing in importance, calling attention to the heat transfer coefficient in summer in relation to the wind speed. In this paper I studied summer and winter wind speeds based on observation results of a weather station, an...

  15. Observations of the atmospheric tide, mean wind, and sodium nightglow near the mesopause with the magneto- optic Doppler analyzer

    Science.gov (United States)

    Williams, Bifford Preston

    1997-09-01

    In this thesis, I (1) demonstrate a new instrument design that is capable of measuring winds and nightglow; (2) present measurements of the mean winds, tides, and sodium nightglow near the mesopause (ca. 90 km); (3) compare these wind results with those measured by other instruments and results of numerical and empirical models; and (4) compare the nightglow intensity measurements with the predictions of a comprehensive numerical model, to better understand the interaction of the tides with the mesopause-region chemistry. I designed, constructed and operated the Magneto-Optic Doppler Analyzer (MODA). For 1.5 years, Moda observed the sodium nightglow intensity variation and the horizontal wind integrated from ~86-96 km altitude at Niwot Ridge, Colorado (40.0o N, 105.5o W). The observed nightglow intensity showed a significant semidiurnal oscillation, with a 5 hr phase shift in the fall. The mean zonal wind peaked in the summer and winter with a minimum at the equinoxes. The meridional wind was slightly southward or near zero. The semidiurnal tide amplitude peaked in the early summer with a minimum in February. The phases were roughly in quadrature. The measured phase difference between the intensity and zonal wind indicated a seasonal variation of the tide-nightglow interaction. MODA wind results were compared with results from the Urbana Medium-Frequency (MF) Radar, the High Resolution Doppler Imager (HRDI), the empirical Horizontal Wind Model 1993 (HWM93), and the theoretical Global Scale Wave Model (GSWM). The annual variation of the mean winds showed the same pattern amongst the instruments and models. MODA measured the smallest tidal amplitudes, possibly due to longitudinal differences. MODA semidiurnal phases agreed better with HRDI and HWM93 (1-2 hr difference), than with GSWM (~6 hr difference). The calculated semidiurnal sodium nightglow variation from the Thermosphere-Ionosphere-Mesosphere- Electrodynamics General Circulation Model for March shows a

  16. Short-Circuit Fault Tolerant Control of a Wind Turbine Driven Induction Generator Based on Sliding Mode Observers

    Directory of Open Access Journals (Sweden)

    Takwa Sellami

    2017-10-01

    Full Text Available The installed energy production capacity of wind turbines is growing intensely on a global scale, making the reliability of wind turbine subsystems of greater significance. However, many faults like Inter-Turn Short-Circuit (ITSC may affect the turbine generator and quickly lead to a decline in supplied power quality. In this framework, this paper proposes a Sliding Mode Observer (SMO-based Fault Tolerant Control (FTC scheme for Induction Generator (IG-based variable-speed grid-connected wind turbines. First, the dynamic models of the wind turbine subsystems were developed. The control schemes were elaborated based on the Maximum Power Point Tracking (MPPT method and Indirect Rotor Flux Oriented Control (IRFOC method. The grid control was also established by regulating the active and reactive powers. The performance of the wind turbine system and the stability of injected power to the grid were hence analyzed under both healthy and faulty conditions. The robust developed SMO-based Fault Detection and Isolation (FDI scheme was proved to be fast and efficient for ITSC detection and localization.Afterwards, SMO were involved in scheming the FTC technique. Accordingly, simulation results assert the efficacy of the proposed ITSC FTC method for variable-speed wind turbines with faulty IG in protecting the subsystems from damage and ensuring continuous connection of the wind turbine to the grid during ITSC faults, hence maintaining power quality.

  17. Tonopah Test Range Air Monitoring: CY2016 Meteorological, Radiological, and Wind Transported Particulate Observations

    Energy Technology Data Exchange (ETDEWEB)

    Chapman, Jenny [Desert Research Inst. (DRI), Las Vegas, NV (United States); Nikolich, George [Desert Research Inst. (DRI), Las Vegas, NV (United States); Shadel, Craig [Desert Research Inst. (DRI), Las Vegas, NV (United States); McCurdy, Greg [Desert Research Inst. (DRI), Las Vegas, NV (United States); Etyemezian, Vicken [Desert Research Inst. (DRI), Las Vegas, NV (United States); Miller, Julianne J [Desert Research Inst. (DRI), Las Vegas, NV (United States); Mizell, Steve [Desert Research Inst. (DRI), Las Vegas, NV (United States)

    2017-10-01

    In 1963, the U.S. Department of Energy (DOE) (formerly the Atomic Energy Commission [AEC]), implemented Operation Roller Coaster on the Tonopah Test Range (TTR) and an adjacent area of the Nevada Test and Training Range (NTTR) (formerly the Nellis Air Force Range). This operation resulted in radionuclide-contaminated soils at the Clean Slate I, II, and III sites. This report documents observations made during ongoing monitoring of radiological, meteorological, and dust conditions at stations installed adjacent to Clean Slate I and Clean Slate III, and at the TTR Sandia National Laboratories (SNL) Range Operations Control (ROC) center. The primary objective of the monitoring effort is to determine if wind blowing across the Clean Slate sites is transporting particles of radionuclide-contaminated soil beyond the physical and administrative boundaries of the sites.

  18. Observational appearance and spectrum of black hole winds from supercritical accretion discs: scattering effect

    Science.gov (United States)

    Orihashi, M.; Fukue, J.

    2017-12-01

    We investigate the observational appearance of a black hole wind blown off from a supercritical accretion disc, considering the electron scattering, which separates the thermalization surface and the apparent photosphere, especially in the high-energy regime. Similar to the spherical case, the size of the thermalization surface becomes quite smaller than that of the apparent photosphere. In contrast with the spherical case, the shapes of the thermalization surface as well as the apparent photosphere are extremely aspherical. As a result, the expected spectral energy distribution is somewhat flat and soft in the middle and high-energy regimes, except for a small peak of the outer disc origin in the low-energy regime.

  19. Turbulence suppression at water density interfaces: observations under moderate wind forcing.

    Science.gov (United States)

    Marcello Falcieri, Francesco; Kanth, Lakshmi H.; Benetazzo, Alvise; Bergamasco, Andrea; Bonaldo, Davide; Barbariol, Francesco; Malačič, Vlado; Sclavo, Mauro; Carniel, Sandro

    2016-04-01

    Water column stratification has a strong influence on the behaviour of turbulence kinetic energy (TKE) dissipation rates. Density gradient interfaces, due to thermohaline characteristics and to suspended sediment concentration, can act as a barrier and significantly damp TKE. Between January 30th - February 4th 2014 (CARPET2014 oceanographic campaign on R/V URANIA) we collected the very first turbulence data in the Gulf of Trieste (a small bay located in the North-eartern part of the Adriatic Sea). Observation consisted of 38 CTD casts and 478 microstructure profiles (145 ensembles) collected with a free-falling probe (MSS90L). Among those 48 were grouped in three sets of yoyo casts, each lasting for about 12 consecutive hours. The meteorological conditions during the campaign were of moderate wind (average wind speed 10 m s-1) and heat flux (net negative heat flux ranging from 150 to 400 W m-2). The water column characteristics in the Gulf during the campaign evolved from well-mixed to stratified conditions with waters intruding from the Adriatic Sea at the bottom. Two types of water intrusions were found during yoyo casts: one coming from the Adriatic Sea northern coast (i.e. warmer, saltier and more turbid) and one coming from the open sea in front of the Po Delta (i.e. cooler, fresher and less turbid). Our observations show that under moderate wind forcing, the GOT was not completely mixed due to the interfaces created by the bottom waters intruding from the open sea. The comparison of microstructure profiles collected during well mixed and stratified conditions permitted us to highlight the effect of different stratification on TKE dissipation rates. While during well mixed condition TKE profiles are governed just by their forcing, the two intrusions showed different impacts on TKE dissipation rate profiles. The coastal one, with high turbidity, acted as a barrier to surface driven turbulence dumping it of almost two order of magnitude, while the one coming

  20. Extreme stress and mental health: immigrant syndrome with chronic and multiple stress (the Ulysses syndrome

    Directory of Open Access Journals (Sweden)

    Joseba Achotegui Loizate

    2014-11-01

    Full Text Available Today, for millions of individuals, emigration presents stress levels of such intensity that they exceed the human capacity of adaptation: loneliness and the enforced separation from one’s loved ones, the failure of the migratory project, the experiencing of extreme hard ships and terror... These persons are, therefore, highly vulnerable to the Immigrant Syndrome with Chronic and Multiple Stress (the Ulysses Syndrome, in reference to the Greek hero who suffered countless adversities and dangers in lands far from his loved ones.We consider that a direct and unequivocal relationship exists between the stress limits which these immigrants experience and the symptomatology of The Ulysses Syndrome and that this Syndromeis found in the limit between the area of mental health and the area of psychopathology.

  1. The Effect of Solar Wind Variations on the Escape of Oxygen Ions From Mars Through Different Channels: MAVEN Observations

    Science.gov (United States)

    Dubinin, E.; Fraenz, M.; Pätzold, M.; McFadden, J.; Halekas, J. S.; DiBraccio, G. A.; Connerney, J. E. P.; Eparvier, F.; Brain, D.; Jakosky, B. M.; Vaisberg, O.; Zelenyi, L.

    2017-11-01

    We present multi-instrument observations of the effects of solar wind on ion escape fluxes on Mars based on the Mars Atmosphere and Volatile EvolutioN (MAVEN) data from 1 November 2014 to 15 May 2016. Losses of oxygen ions through different channels (plasma sheet, magnetic lobes, boundary layer, and ion plume) as a function of the solar wind and the interplanetary magnetic field variations were studied. We have utilized the modified Mars Solar Electric (MSE) coordinate system for separation of the different escape routes. Fluxes of the low-energy (≤30 eV) and high-energy (≥30 eV) ions reveal different trends with changes in the solar wind dynamic pressure, the solar wind flux, and the motional electric field. Major oxygen fluxes occur through the tail of the induced magnetosphere. The solar wind motional electric field produces an asymmetry in the ion fluxes and leads to different relations between ion fluxes supplying the tail from the different hemispheres and the solar wind dynamic pressure (or flux) and the motional electric field. The main driver for escape of the high-energy oxygen ions is the solar wind flux (or dynamic pressure). On the other hand, the low-energy ion component shows the opposite trend: ion flux decreases with increasing solar wind flux. As a result, the averaged total oxygen ion fluxes reveal a low variability with the solar wind strength. The large standard deviations from the averages values of the escape fluxes indicate the existence of mechanisms which can enhance or suppress the efficiency of the ion escape. It is shown that the Martian magnetosphere possesses the properties of a combined magnetosphere which contains different classes of field lines. The existence of the closed magnetic field lines in the near-Mars tail might be responsible for suppression of the ion escape fluxes.

  2. Turbulence feature modifications from high to low wind conditions: results from the CCT observations at Ny-Ålesund, Svalbard.

    Science.gov (United States)

    Schiavon, Mario; Mazzola, Mauro; Tampieri, Francesco; Pietro Viola, Angelo; Choi, Taejin

    2017-04-01

    The turbulence features in the quasi neutral surface layer are investigated as the intensity of the wind decreases, i.e. as the forcing due to the shear decreases. In this aim, a 5-year (2012-2016) set of observations of meteorological and micro-meteorological parameters acquired on the Climate Change Tower (CCT) in Ny-Ålesund, Svalbard Islands, is used. The 34-m high tower, operated by the Italian National Council of Research (CNR) is equipped with four slow response wind and temperature probes and three fast response sonic anemometers and is located on heterogeneous terrain. One of the fast sensors was installed by KOPRI since 2012. The observations are averaged over 10 and 30 minutes intervals. The analysis addresses the share of the mean turbulent kinetic energy (TKE) among the along-wind, cross-wind and vertical velocity variances (respectively , , ), with attention to the parameterizations of the boundary layer commonly used in NWP models: the classical Mellor-Yamada (1982) scheme with the return-to-isotropy term by Rotta(1951) and its modifications, and the recent approach by Zilitinkevich and coworkers (2013). The results show that the share of TKE among the vertical and the total horizontal variance + is weakly dependent on the wind velocity while the share of the total horizontal variance between the along-wind and cross-wind components depends on wind speed. At high velocity (and large wind shear) a clear anisotropy , with ≈ 2 , is observed, quite consistent with literature (Tampieri, 2017, pag. 69). As the velocity decreases, the ratio /( + ) displays a wide flat distribution between 0.2 and 0.8 with median values corresponding approximately to horizontal isotropy: ≈. These features can be parameterized using suitable coefficients, function of the wind intensity in the equations for the TKE share, capturing the average behaviour of the flow. A further investigation based on estimates of the relative importance of the high frequency and low

  3. Statistics of MLT wind field values derived from 11 years of common volume specular meteor observations in northern Norway

    Science.gov (United States)

    Chau, Jorge Luis; Stober, Gunter; Laskar, Fazlul; Hall, Chris M.; Tsutsumi, Masaki

    2016-04-01

    Traditionally mean values of the mesosphere and lower thermosphere winds over the radar volume are obtained using monostatic specular meteor radars. Such observing volume consist of a few hundreds of kilometers in radius. Moreover the differences between measured radial velocities and the expected radial velocities from the measured mean winds are used to derive properties of gravity wave momentum fluxes. Recently, Stober and Chau [2015] have proposed to use a multi-static approach to retrieve horizontally resolved wind fields, where most of the radar volume is observed from different viewing angles. Similar results could be obtained if measurements from close-by monostatic systems are combined. In this work we present the results of the derived wind fields from combining specular meteor radar data between 2004 and 2015 from the Trømso (19.22oW, 69.58oN) and Andenes (16.04oW, 69.27oN) radar systems. Among the directly estimated values are the mean winds and the horizontal and vertical gradients of the zonal and meridional winds. Combining the horizontal gradients, the horizontal divergence, relative vorticity, shear and deformation are derived. The seasonal and annual variability of these parameters are presented and discussed, as well as the planetary wave, tidal, and gravity wave information embedded in these new parameters.

  4. An Observing System Simulation Experiment (OSSE to Assess the Impact of Doppler Wind Lidar (DWL Measurements on the Numerical Simulation of a Tropical Cyclone

    Directory of Open Access Journals (Sweden)

    Lei Zhang

    2010-01-01

    Full Text Available The importance of wind observations has been recognized for many years. However, wind observations—especially three-dimensional global wind measurements—are very limited. A satellite-based Doppler Wind Lidar (DWL is proposed to measure three-dimensional wind profiles using remote sensing techniques. Assimilating these observations into a mesoscale model is expected to improve the performance of the numerical weather prediction (NWP models. In order to examine the potential impact of the DWL three-dimensional wind profile observations on the numerical simulation and prediction of tropical cyclones, a set of observing simulation system experiments (OSSEs is performed using the advanced research version of the Weather Research and Forecasting (WRF model and its three-dimensional variational (3DVAR data assimilation system. Results indicate that assimilating the DWL wind observations into the mesoscale numerical model has significant potential for improving tropical cyclone track and intensity forecasts.

  5. Frequency spectra and vertical profiles of wind fluctuations in the summer Antarctic mesosphere revealed by MST radar observations

    Science.gov (United States)

    Sato, Kaoru; Kohma, Masashi; Tsutsumi, Masaki; Sato, Toru

    2017-01-01

    Continuous observations of polar mesosphere summer echoes at heights from 81-93 km were performed using the first Mesosphere-Stratosphere-Troposphere/Incoherent Scatter radar in the Antarctic over the three summer periods of 2013/2014, 2014/2015, and 2015/2016. Power spectra of horizontal and vertical wind fluctuations, and momentum flux spectra in a wide-frequency range from (8 min)-1 to (20 days) -1 were first estimated for the Antarctic summer mesosphere. The horizontal (vertical) wind power spectra obey a power law with an exponent of approximately -2 (-1) at frequencies higher than the inertial frequency of (13 h)-1 and have isolated peaks at about 1 day and a half day. In addition, an isolated peak of a quasi-2 day period is observed in the horizontal wind spectra but is absent from the vertical wind spectra, which is consistent with the characteristics of a normal-mode Rossby-gravity wave. Zonal (meridional) momentum flux spectra are mainly positive (negative), and large fluxes are observed in a relatively low-frequency range from (1 day)-1 to (1 h)-1. A case study was performed to investigate vertical profiles of momentum fluxes associated with gravity waves and time mean winds on and around 3 January 2015 when a minor stratospheric warming occurred in the Northern Hemisphere. A significant momentum flux convergence corresponding to an eastward acceleration of 200 m s-1 d-1 was observed before the warming and became stronger after the warming when mean zonal wind weakened. The strong wave forcing roughly accorded with the Coriolis force of mean meridional winds.

  6. James Joyce’s Trojan Hobby-Horse: The Iliad and the Collective Unconscious Ulysses

    Directory of Open Access Journals (Sweden)

    Dieter Fuchs

    2013-12-01

    Full Text Available James Joyce’s Ulysses rewrites the Homeric Odyssey in such a way that the ancient myth provides a structural pattern, which gives order and meaning to a seemingly chaotic and meaningless contemporary world – an aspect which T. S. Eliot called the “mythical method”. As the characters of Ulysses are ignorant of this ordering device, they function as Jungian archetypes rather than individuals: Their deeds correspond to a mythical framework which is not actively remembered but provides a collective unconsciousness that guides their lives as a principle of order and continuity. What they do is meaningful although they consider themselves as insignificant agents thrown into a seemingly chaotic world. Whereas scholars have focused on Homer’s Odyssey as an archetypal (i.e. collective unconscious key to the cultural memory of the mythical roots of Western culture, they have turned a comparatively blind eye to the fact that Homer’s corresponding work of the Iliad has a similar function for the mythopoetic design of Ulysses. This paper is going to reconstruct Joyce’s neglected intertextual dialogue with the Iliad as an archetypal key to the cultural memory of the roots of Western civilisation.

  7. Observational Evidence for Self-generation of Small-scale Magnetic Flux Ropes from Intermittent Solar Wind Turbulence

    Science.gov (United States)

    Zheng, Jinlei; Hu, Qiang

    2018-01-01

    We present unique and additional observational evidence for the self-generation of small-scale coherent magnetic flux rope structures in the solar wind. Such structures with durations between 9 and 361 minutes are identified from Wind in situ spacecraft measurements through the Grad–Shafranov (GS) reconstruction approach. The event occurrence counts are on the order of 3500 per year on average and have a clear solar-cycle dependence. We build a database of small-scale magnetic flux ropes from 20 yr worth of Wind spacecraft data. We show a power-law distribution of the wall-to-wall time corresponding well to the inertial range turbulence, which agrees with relevant observations and numerical simulation results. We also provide the axial current density distribution from the GS-based observational analysis, which yields a non-Gaussian probability density function consistent with numerical simulation results.

  8. Kinetic scale turbulence and dissipation in the solar wind: key observational results and future outlook

    Science.gov (United States)

    Goldstein, M. L.; Wicks, R. T.; Perri, S.; Sahraoui, F.

    2015-01-01

    Turbulence is ubiquitous in the solar wind. Turbulence causes kinetic and magnetic energy to cascade to small scales where they are eventually dissipated, adding heat to the plasma. The details of how this occurs are not well understood. This article reviews the evidence for turbulent dissipation and examines various diagnostics for identifying solar wind regions where dissipation is occurring. We also discuss how future missions will further enhance our understanding of the importance of turbulence to solar wind dynamics. PMID:25848084

  9. Model for vortex turbulence with discontinuities in the solar wind

    Directory of Open Access Journals (Sweden)

    O. P. Verkhoglyadova

    2003-01-01

    Full Text Available A model of vortex with embedded discontinuities in plasma flow is developed in the framework of ideal MHD in a low b plasma. Vortex structures are considered as a result of 2-D evolution of nonlinear shear Alfvén waves in the heliosphere. Physical properties of the solutions and vector fields are analyzed and the observational aspects of the model are discussed. The ratio of normal components to the discontinuity Br /Vr can be close to -2. The alignment between velocity and magnetic field vectors takes place. Spacecraft crossing such vortices will typically observe a pair of discontinuities, but with dissimilar properties. Occurrence rate for different discontinuity types is estimated and agrees with observations in high-speed solar wind stream. Discontinuity crossing provides a backward rotation of magnetic field vector and can be observed as part of a backward arc. The Ulysses magnetometer data obtained in the fast solar wind are compared with the results of theoretical modelling.

  10. Decades-long changes of the interstellar wind through our solar system.

    Science.gov (United States)

    Frisch, P C; Bzowski, M; Livadiotis, G; McComas, D J; Moebius, E; Mueller, H-R; Pryor, W R; Schwadron, N A; Sokół, J M; Vallerga, J V; Ajello, J M

    2013-09-06

    The journey of the Sun through the dynamically active local interstellar medium creates an evolving heliosphere environment. This motion drives a wind of interstellar material through the heliosphere that has been measured with Earth-orbiting and interplanetary spacecraft for 40 years. Recent results obtained by NASA's Interstellar Boundary Explorer mission during 2009-2010 suggest that neutral interstellar atoms flow into the solar system from a different direction than found previously. These prior measurements represent data collected from Ulysses and other spacecraft during 1992-2002 and a variety of older measurements acquired during 1972-1978. Consideration of all data types and their published results and uncertainties, over the three epochs of observations, indicates that the trend for the interstellar flow ecliptic longitude to increase linearly with time is statistically significant.

  11. Mistic winds, a microsatellite constellation approach to high-resolution observations of the atmosphere using infrared sounding and 3d winds measurements

    Science.gov (United States)

    Maschhoff, K. R.; Polizotti, J. J.; Aumann, H. H.; Susskind, J.

    2016-10-01

    MISTiC Winds is an approach to improve short-term weather forecasting based on a miniature high resolution, wide field, thermal emission spectrometry instrument that will provide global tropospheric vertical profiles of atmospheric temperature and humidity at high (3-4 km) horizontal and vertical ( 1 km) spatial resolution. MISTiC's extraordinarily small size, payload mass of less than 15 kg, and minimal cooling requirements can be accommodated aboard a 27U-class CubeSat or an ESPA-Class micro-satellite. Low fabrication and launch costs enable a LEO sunsynchronous sounding constellation that would collectively provide frequent IR vertical profiles and vertically resolved atmospheric motion vector wind observations in the troposphere. These observations are highly complementary to present and emerging environmental observing systems, and would provide a combination of high vertical and horizontal resolution not provided by any other environmental observing system currently in operation. The spectral measurements that would be provided by MISTiC Winds are similar to those of NASA's AIRS that was built by BAE Systems and operates aboard the AQUA satellite. These new observations, when assimilated into high resolution numerical weather models, would revolutionize short-term and severe weather forecasting, save lives, and support key economic decisions in the energy, air transport, and agriculture arenas-at much lower cost than providing these observations from geostationary orbit. In addition, this observation capability would be a critical tool for the study of transport processes for water vapor, clouds, pollution, and aerosols. Key remaining technical risks are being reduced through laboratory and airborne testing under NASA's Instrument Incubator Program.

  12. MISTiC Winds, a Micro-Satellite Constellation Approach to High Resolution Observations of the Atmosphere using Infrared Sounding and 3D Winds Measurements

    Science.gov (United States)

    Maschhoff, K. R.; Polizotti, J. J.; Susskind, J.; Aumann, H. H.

    2015-12-01

    MISTiCTM Winds is an approach to improve short-term weather forecasting based on a miniature high resolution, wide field, thermal emission spectrometry instrument that will provide global tropospheric vertical profiles of atmospheric temperature and humidity at high (3-4 km) horizontal and vertical ( 1 km) spatial resolution. MISTiC's extraordinarily small size, payload mass of less than 15 kg, and minimal cooling requirements can be accommodated aboard a 27U-class CubeSat or an ESPA-Class micro-satellite. Low fabrication and launch costs enable a LEO sun-synchronous sounding constellation that would collectively provide frequent IR vertical profiles and vertically resolved atmospheric motion vector wind observations in the troposphere. These observations are highly complementary to present and emerging environmental observing systems, and would provide a combination of high vertical and horizontal resolution not provided by any other environmental observing system currently in operation. The spectral measurements that would be provided by MISTiC Winds are similar to those of NASA's Atmospheric Infrared Sounder that was built by BAE Systems and operates aboard the AQUA satellite. These new observations, when assimilated into high resolution numerical weather models, would revolutionize short-term and severe weather forecasting, save lives, and support key economic decisions in the energy, air transport, and agriculture arenas-at much lower cost than providing these observations from geostationary orbit. In addition, this observation capability would be a critical tool for the study of transport processes for water vapor, clouds, pollution, and aerosols. Key technical risks are being reduced through laboratory and airborne testing under NASA's Instrument Incubator Program.

  13. MISTiC Winds: A micro-satellite constellation approach to high resolution observations of the atmosphere using infrared sounding and 3D winds measurements

    Science.gov (United States)

    Maschhoff, K. R.; Polizotti, J. J.; Aumann, H. H.; Susskind, J.

    2016-09-01

    MISTiCTM Winds is an approach to improve short-term weather forecasting based on a miniature high resolution, wide field, thermal emission spectrometry instrument that will provide global tropospheric vertical profiles of atmospheric temperature and humidity at high (3-4 km) horizontal and vertical ( 1 km) spatial resolution. MISTiC's extraordinarily small size, payload mass of less than 15 kg, and minimal cooling requirements can be accommodated aboard a 27U-class CubeSat or an ESPA-Class micro-satellite. Low fabrication and launch costs enable a LEO sunsynchronous sounding constellation that would collectively provide frequent IR vertical profiles and vertically resolved atmospheric motion vector wind observations in the troposphere. These observations are highly complementary to present and emerging environmental observing systems, and would provide a combination of high vertical and horizontal resolution not provided by any other environmental observing system currently in operation. The spectral measurements that would be provided by MISTiC Winds are similar to those of NASA's AIRS that was built by BAE Systems and operates aboard the AQUA satellite. These new observations, when assimilated into high resolution numerical weather models, would revolutionize short-term and severe weather forecasting, save lives, and support key economic decisions in the energy, air transport, and agriculture arenas-at much lower cost than providing these observations from geostationary orbit. In addition, this observation capability would be a critical tool for the study of transport processes for water vapor, clouds, pollution, and aerosols. Key remaining technical risks are being reduced through laboratory and airborne testing under NASA's Instrument Incubator Program.

  14. MISTiC Winds, a Micro-Satellite Constellation Approach to High Resolution Observations of the Atmosphere Using Infrared Sounding and 3D Winds Measurements

    Science.gov (United States)

    Maschhoff, K. R.; Polizotti, J. J.; Aumann, H. H.; Susskind, J.

    2016-01-01

    MISTiC(TM) Winds is an approach to improve short-term weather forecasting based on a miniature high resolution, wide field, thermal emission spectrometry instrument that will provide global tropospheric vertical profiles of atmospheric temperature and humidity at high (3-4 km) horizontal and vertical ( 1 km) spatial resolution. MISTiCs extraordinarily small size, payload mass of less than 15 kg, and minimal cooling requirements can be accommodated aboard a 27U-class CubeSat or an ESPA-Class micro-satellite. Low fabrication and launch costs enable a LEO sunsynchronous sounding constellation that would collectively provide frequent IR vertical profiles and vertically resolved atmospheric motion vector wind observations in the troposphere. These observations are highly complementary to present and emerging environmental observing systems, and would provide a combination of high vertical and horizontal resolution not provided by any other environmental observing system currently in operation. The spectral measurements that would be provided by MISTiC Winds are similar to those of NASA's AIRS that was built by BAE Systems and operates aboard the AQUA satellite. These new observations, when assimilated into high resolution numerical weather models, would revolutionize short-term and severe weather forecasting, save lives, and support key economic decisions in the energy, air transport, and agriculture arenasat much lower cost than providing these observations from geostationary orbit. In addition, this observation capability would be a critical tool for the study of transport processes for water vapor, clouds, pollution, and aerosols. Key remaining technical risks are being reduced through laboratory and airborne testing under NASA's Instrument Incubator Program.

  15. High-resolution observations of the near-surface wind field over an isolated mountain and in a steep river canyon

    Science.gov (United States)

    B. W. Butler; N. S. Wagenbrenner; J. M. Forthofer; B. K. Lamb; K. S. Shannon; D. Finn; R. M. Eckman; K. Clawson; L. Bradshaw; P. Sopko; S. Beard; D. Jimenez; C. Wold; M. Vosburgh

    2015-01-01

    A number of numerical wind flow models have been developed for simulating wind flow at relatively fine spatial resolutions (e.g., 100 m); however, there are very limited observational data available for evaluating these high-resolution models. This study presents high-resolution surface wind data sets collected from an isolated mountain and a steep river canyon. The...

  16. The observed scaling properties of fluctuations in the solar wind and in geomagnetic indices: intermittent turbulence and coronal driver.

    Science.gov (United States)

    Chapman, S. C.; Hnat, B.; Kiyani, K.; Watkins, N.

    2007-12-01

    The solar wind provides a natural laboratory for observations of MHD turbulence over extended temporal scales. We quantify the 'macroscopic' scaling seen in extended intervals of solar wind by testing for scaling in the Probability Density Functions (PDF) of fluctuations in the timeseries both directly and via structure function analysis. In practice there are statistical limitations presented by a finite length time series which we will first discuss. The anisotropic nature of solar wind fluctuations can be accessed by decomposing the vector velocity linearly into two coexistent components perpendicular and parallel to the local average magnetic field. These show distinct scaling. That of the perpendicular fluctuations is consistent with recent predictions for anisotropic MHD. That of the parallel fluctuations is close to the scaling which we find in the number and magnetic energy density, and Poynting flux. One interpretation of the co- existence of these scalings in the solar wind is that they reflect both local and nonlocal phenomenologies, with implications for our understanding of the evolving solar wind. Intriguingly, a more detailed analysis of magnetic energy density reveals a solar cycle dependence, and at solar maximum, self affine rather than multifractal scaling, suggesting the scaling is of solar origin. To see how these fluctuations impact on magnetospheric activity, we consider the same analysis performed on fluctuations of the AU and AL geomagnetic indices that provide a measure of magnetospheric activity, and of the epsilon parameter which is a measure of the solar wind driver.

  17. ROSAT Observations of Soft X-ray Emission from the Solar Wind Interaction with the Lunar Exosphere

    Science.gov (United States)

    Collier, Michael

    We analyze the ROSAT PSPC soft X-ray image of the moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the antisolar point. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now along with Mars, Venus, and Earth, the moon represents another solar system body at which solar wind charge exchange has been observed.

  18. Radio Observations of the Pulsar Wind Nebula HESS J1303-631 with ATCA

    Science.gov (United States)

    Sushch, Iurii; Oya, Igor; Schwanke, Ullrich; Johnston, Simon; Dalton, Matthew

    2016-04-01

    Based on its enregy-dependent morphology the initially unidentified very high energy (VHE; E > 100 GeV) gamma-ray source HESS J1303-631 was recently associated with the pulsar PSR J1301-6305. Subsequent detection of X-ray and GeV counterparts further supports the identification of the H.E.S.S. source as evolved pulsar wind nebula (PWN). Recent radio observations of the PSR J1301-6305 region with ATCA dedicated to search for the radio counterpart of HESS J1303-631 are reported here. Observations at 5.5 GHz and 7.5 GHz do not reveal any extended emission associated with the pulsar. The analysis of the archival 1.384 GHz and 2.368 GHz data also does not show any significant emission. The 1.384 GHz data reveal a hint of an extended shell-like emission in the same region which might be a supernova remnant. The implications of the non-detection at radio wavelengths on the nature and evolution of the PWN as well as the possibility of the SNR candidate being a birth place of PSR J1301-6305 are discussed.

  19. HF radar observations of a quasi-biennial oscillation in midlatitude mesospheric winds

    Science.gov (United States)

    Malhotra, Garima; Ruohoniemi, J. M.; Baker, J. B. H.; Hibbins, R. E.; McWilliams, K. A.

    2016-11-01

    The equatorial quasi-biennial oscillation (QBO) is known to be an important source of interannual variability in the middle- and high-latitude stratosphere. The influence of the QBO on the stratospheric polar vortex in particular has been extensively studied. However, the impact of the QBO on the winds of the midlatitude mesosphere is much less clear. We have applied 13 years (2002-2014) of data from the Saskatoon Super Dual Auroral Radar Network HF radar to show that there is a strong QBO signature in the midlatitude mesospheric zonal winds during the late winter months. We find that the Saskatoon mesospheric winds are related to the winds of the equatorial QBO at 50 hPa such that the westerly mesospheric winds strengthen when QBO is easterly, and vice versa. We also consider the situation in the late winter Saskatoon stratosphere using the European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis data set. We find that the Saskatoon stratospheric winds between 7 hPa and 70 hPa weaken when the equatorial QBO at 50 hPa is easterly, and vice versa. We speculate that gravity wave filtering from the QBO-modulated stratospheric winds and subsequent opposite momentum deposition in the mesosphere plays a major role in the appearance of the QBO signature in the late winter Saskatoon mesospheric winds, thereby coupling the equatorial stratosphere and the midlatitude mesosphere.

  20. An observational climatology of anomalous wind events at offshore meteomast IJmuiden (North Sea)

    NARCIS (Netherlands)

    Kalverla, P.C.; Steeneveld, G.J.; Ronda, R.J.; Holtslag, A.A.M.

    2017-01-01

    Uncertainty reduction in offshore wind systems heavily relies on meteorological advances. A detailed characterization of the wind climate at a given site is indispensable for site assessment, and its accurate representation in load assessment models can reduce costs of turbine design and the risk of

  1. Observation Targeting for the Tehachapi Pass and Mid-Columbia Basin: WindSENSE Phase III Project Summary Report

    Energy Technology Data Exchange (ETDEWEB)

    Hanley, D

    2011-10-22

    The overall goal of this multi-phased research project known as WindSENSE is to develop an observation system deployment strategy that would improve wind power generation forecasts. The objective of the deployment strategy is to produce the maximum benefit for 1- to 6-hour ahead forecasts of wind speed at hub-height ({approx}80 m). In Phase III of the project, the focus was on the Mid-Columbia Basin region which encompasses the Bonneville Power Administration (BPA) wind generation area shown in Figure 1 that includes Klondike, Stateline, and Hopkins Ridge wind plants. The typical hub height of a wind turbine is approximately 80-m above ground level (AGL). So it would seem that building meteorological towers in the region upwind of a wind generation facility would provide data necessary to improve the short-term forecasts for the 80-m AGL wind speed. However, this additional meteorological information typically does not significantly improve the accuracy of the 0- to 6-hour ahead wind power forecasts because processes controlling wind variability change from day-to-day and, at times, from hour-to-hour. It is also important to note that some processes causing significant changes in wind power production function principally in the vertical direction. These processes will not be detected by meteorological towers at off-site locations. For these reasons, it is quite challenging to determine the best type of sensors and deployment locations. To address the measurement deployment problem, Ensemble Sensitivity Analysis (ESA) was applied in the Phase I portion of the WindSENSE project. The ESA approach was initially designed to produce spatial fields that depict the sensitivity of a forecast metric to a set of prior state variables selected by the user. The best combination of variables and locations to improve the forecast was determined using the Multiple Observation Optimization Algorithm (MOOA) developed in Phase I. In Zack et al. (2010a), the ESA-MOOA approach was

  2. Field-based observations confirm linear scaling of sand flux with wind stress

    CERN Document Server

    Martin, Raleigh L

    2016-01-01

    Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the sand flux scales with wind speed, largely because models do not agree on how particle speed changes with wind shear velocity. Here, we present comprehensive measurements from three new field sites and three published studies, showing that characteristic saltation layer heights, and thus particle speeds, remain approximately constant with shear velocity. This result implies a linear dependence of saltation flux on wind shear stress, which contrasts with the nonlinear 3/2 scaling used in most aeolian process predictions. We confirm the linear flux law with direct measurements of the stress-flux relationship occurring at each site. Models for dust generation, dune migration, and other processes driven by wind-blown sand on Earth, Mars, and several other planetary surfaces should be modified to account for linear stress-flux scaling.

  3. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  4. Average thermospheric wind patterns over the polar regions, as observed by CHAMP

    Directory of Open Access Journals (Sweden)

    H. Lühr

    2007-06-01

    Full Text Available Measurements of the CHAMP accelerometer are utilized to investigate the average thermospheric wind distribution in the polar regions at altitudes around 400 km. This study puts special emphasis on the seasonal differences in the wind patterns. For this purpose 131 days centered on the June solstice of 2003 are considered. Within that period CHAMP's orbit is precessing once through all local times. The cross-track wind estimates of all 2030 passes are used to construct mean wind vectors for 918 equal-area cells. These bin averages are presented in corrected geomagnetic coordinates. Both hemispheres are considered simultaneously providing summer and winter responses for the same prevailing geophysical conditions. The period under study is characterized by high magnetic activity (Kp=4− but moderate solar flux level (F10.7=124. Our analysis reveals clear wind features in the summer (Northern Hemisphere. Over the polar cap there is a fast day-to-night flow with mean speeds surpassing 600 m/s in the dawn sector. At auroral latitudes we find strong westward zonal winds on the dawn side. On the dusk side, however, an anti-cyclonic vortex is forming. The dawn/dusk asymmetry is attributed to the combined action of Coriolis and centrifugal forces. Along the auroral oval the sunward streaming plasma causes a stagnation of the day-to-night wind. This effect is particularly clear on the dusk side. On the dawn side it is evident only from midnight to 06:00 MLT. The winter (Southern Hemisphere reveals similar wind features, but they are less well ordered. The mean day-to-night wind over the polar cap is weaker by about 35%. Otherwise, the seasonal differences are mainly confined to the dayside (06:00–18:00 MLT. In addition, the larger offset between geographic and geomagnetic pole in the south also causes hemispheric differences of the thermospheric wind distribution.

  5. Quality assessment of Automatic Dependent Surveillance Contract (ADS-C wind and temperature observation from commercial aircraft

    Directory of Open Access Journals (Sweden)

    S. de Haan

    2013-02-01

    Full Text Available Aircraft observations of wind and temperature are very important for upper air meteorology. In this article, the quality of the meteorological information of an Automatic Dependent Surveillance-Contract (ADS-C message is assessed. The ADS-C messages broadcast by the aircraft are received at air traffic control centres for surveillance and airline control centres for general aircraft and dispatch management. A comparison is performed against a global numerical prediction (NWP model and wind and temperature observations derived from Enhanced Surveillance (EHS air-traffic control radar which interrogates all aircraft in selective mode (Mode-S EHS. Almost 16 000 ADS-C reports with meteorological information were compiled from the Royal Dutch Airlines (KLM database. The length of the data set is 76 consecutive days and started on 1 January 2011. The wind and temperature observations are of good quality when compared to the global NWP forecast fields from the European Centre for Medium-Range Weather Forecasts (ECMWF. Comparison of ADS-C wind and temperature observations against Mode-S EHS derived observations in the vicinity of Amsterdam Airport Schiphol shows that the wind observations are of similar quality and the temperature observations of ADS-C are of better quality than those from Mode-S EHS. However, the current ADS-C data set has a lower vertical resolution than Mode-S EHS. High vertical resolution can be achieved by requesting more ADS-C when aircraft are ascending or descending, but could result in increased data communication costs.

  6. Observations of Near-Surface Relative Humidity in a Wind Turbine Array Boundary Layer Using an Instrumented Unmanned Aerial System

    Science.gov (United States)

    Adkins, K. A.; Sescu, A.

    2016-12-01

    Simulation and modeling have shown that wind farms have an impact on the near-surface atmospheric boundary layer (ABL) as turbulent wakes generated by the turbines enhance vertical mixing. These changes alter downstream atmospheric properties. With a large portion of wind farms hosted within an agricultural context, changes to the environment can potentially have secondary impacts such as to the productivity of crops. With the exception of a few observational data sets that focus on the impact to near-surface temperature, little to no observational evidence exists. These few studies also lack high spatial resolution due to their use of a limited number of meteorological towers or remote sensing techniques. This study utilizes an instrumented small unmanned aerial system (sUAS) to gather in-situ field measurements from two Midwest wind farms, focusing on the impact that large utility-scale wind turbines have on relative humidity. Wind turbines are found to differentially alter the relative humidity in the downstream, spanwise and vertical directions under a variety of atmospheric stability conditions.

  7. Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

    Science.gov (United States)

    Jasinski, Jamie M.; Slavin, James A.; Raines, Jim M.; DiBraccio, Gina A.

    2017-12-01

    We analyze 94 traversals of Mercury's southern magnetospheric plasma mantle using data from the MESSENGER spacecraft. The mean and median proton number densities in the mantle are 1.5 and 1.3 cm-3, respectively. For sodium number density these values are 0.004 and 0.002 cm-3. Moderately higher densities are observed on the magnetospheric dusk side. The mantle supplies up to 1.5 × 108 cm-2 s-1 and 0.8 × 108 cm-2 s-1 of proton and sodium flux to the plasma sheet, respectively. We estimate the cross-electric magnetospheric potential from each observation and find a mean of 19 kV (standard deviation of 16 kV) and a median of 13 kV. This is an important result as it is lower than previous estimations and shows that Mercury's magnetosphere is at times not as highly driven by the solar wind as previously thought. Our values are comparable to the estimations for the ice giant planets, Uranus and Neptune, but lower than Earth. The estimated potentials do have a very large range of values (1-74 kV), showing that Mercury's magnetosphere is highly dynamic. A correlation of the potential is found to the interplanetary magnetic field (IMF) magnitude, supporting evidence that dayside magnetic reconnection can occur at all shear angles at Mercury. But we also see that Mercury has an Earth-like magnetospheric response, favoring -BZ IMF orientation. We find evidence that -BX orientations in the IMF favor the southern cusp and southern mantle. This is in agreement with telescopic observations of exospheric emission, but in disagreement with modeling.

  8. Observations of Wind-Direction Variability in the Nocturnal Boundary Layer

    Science.gov (United States)

    Lang, Francisco; Belušić, Danijel; Siems, Steven

    2017-09-01

    Large sudden wind-direction shifts and submeso variability under nocturnal conditions are examined using a micrometeorological network of stations in north-western Victoria, Australia. The network was located in an area with mostly homogeneous and flat terrain. We have investigated the main characteristics of the horizontal propagation of events causing the wind-direction shift and not addressed in previous studies. The submeso motions at the study site exhibit behaviour typical of flat terrain, such as the lower relative mesovelocity scale and smaller cross-wind variances than that for complex terrain. The distribution of wind-direction shifts shows that there is a small but persistent preference for counter-clockwise rotation, occurring for 55% of the time. Large wind-direction shifts tend to be associated with a sharp decrease in air temperature (74% of the time), which is associated with rising motion of cold air, followed by an increase in turbulent mixing. The horizontal propagation of events was analyzed using the cross-correlation function method. There is no preferred mean wind direction associated with the events nor is there any relationship between the mean wind and propagation directions. The latter indicates that the events are most likely not local flow perturbations advected by the mean flow but are rather features of generally unknown origin. This needs to be taken into account when developing parametrizations of the stable boundary layer in numerical models.

  9. Quality Control and First Insights on the Variability of Surface Wind Observations for North Eastern North America

    Science.gov (United States)

    Lucio-Eceiza, E.; González-Rouco, F. J.; Navarro Montesinos, J.; Hidalgo; Jiménez, P.; García-Bustamante, E.; Conte, J.; Casabella, N.; Beltrami, H.

    2013-12-01

    Over the last decades, a policy change in energy sources has been fostered in Atlantic Canada. The purpose of this has been to reduce the dependency on energy produced abroad and to propose feasible alternatives with the aim of reducing greenhouse emissions. The region offers a high potential for the development of wind energy facilities and studies within the framework of wind resource assessment are encouraged. Studies of this nature rely on the quality of observational data. Henceforth, it is essential to develop procedures that ensure the reliability of observations before they are subjected to any subsequent analysis. This work summarizes the Quality Control process applied to an observational database of surface wind module and direction in North Eastern North America. The data set consists of 525 stations compiled from three different sources: 344 land sites from Environment Canada (EC; 1940-2009) located in the provinces of Atlantic Canada and Quebec; 40 buoys distributed over the East Coast and the Canadian Great Lakes provided by Fisheries and Oceans Canada (FOC; 1988-2008); and 141 land sites over both Eastern Canada and North Eastern USA provided by the National Center of Atmospheric Research (NCAR; 1975-2010). The process comprises different phases that: 1) unify measurement units and recording times; 2) find accidentally duplicated periods of data within a time series or between different stations; 3) check for physical consistency in the ranges of values; 4) detect time intervals of anomalous low and high variability; and 5) look for long term biases in mean and variance. The temporal extension and resolution of the quality controlled database allows to explore the wind variability at different temporal scales, from daily to multidecadal. This contribution will present a first assessment of the wind field climatology in the region, including a description of long term trends, analogous of wind circulation regimes and their relationship to large scale

  10. Understanding the Internal Magnetic Field Configurations of ICMEs Using More than 20 Years of Wind Observations

    Science.gov (United States)

    Nieves-Chinchilla, T.; Vourlidas, A.; Raymond, J. C.; Linton, M. G.; Al-haddad, N.; Savani, N. P.; Szabo, A.; Hidalgo, M. A.

    2018-02-01

    The magnetic topology, structure, and geometry of the magnetic obstacles embedded within interplanetary coronal mass ejections (ICMEs) are not yet fully and consistently described by in situ models and reconstruction techniques. The main goal of this work is to better understand the status of the internal magnetic field of ICMEs and to explore in situ signatures to identify clues to develop a more accurate and reliable in situ analytical models. We take advantage of more than 20 years of Wind observations of transients at 1 AU to compile a comprehensive database of ICMEs through three solar cycles, from 1995 to 2015. The catalog is publicly available at wind.gsfc.nasa.gov and is fully described in this article. We identify and collect the properties of 337 ICMEs, of which 298 show organized magnetic field signatures. To allow for departures from idealized magnetic configurations, we introduce the term "magnetic obstacle" (MO) to signify the possibility of more complex configurations. To quantify the asymmetry of the magnetic field strength profile within these events, we introduce the distortion parameter (DiP) and calculate the expansion velocity within the magnetic obstacle. Circular-cylindrical geometry is assumed when the magnetic field strength displays a symmetric profile. We perform a statistical study of these two parameters and find that only 35% of the events show symmetric magnetic profiles and a low enough expansion velocity to be compatible with the assumption of an idealized cylindrical static flux rope, and that 41% of the events do not show the expected relationship between expansion and magnetic field compression in the front, with the maximum magnetic field closer to the first encounter of the spacecraft with the magnetic obstacle; 18% show contractions ( i.e. apparent negative expansion velocity), and 30% show magnetic field compression in the back. We derive an empirical relation between DiP and expansion velocity that is the first step toward

  11. ON THE RETRIEVAL OF MESOSPHERIC WINDS ON MARS AND VENUS FROM GROUND-BASED OBSERVATIONS AT 10 μm

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Valverde, M. A. [Instituto de Astrofisica de Andalucia, IAA/CSIC, Granada (Spain); Montabone, L. [Space Science Institute, Boulder, CO (United States); Sornig, M.; Sonnabend, G., E-mail: valverde@iaa.es [University of Cologne, KOSMA, Köln (Germany)

    2016-01-10

    A detailed analysis is presented of ground-based observations of atmospheric emissions on Mars and Venus under non-local thermodynamic equilibrium (non-LTE) conditions at high spectral resolution. Our first goal is to comprehend the difficulties behind the derivation of wind speeds from ground-based observations. A second goal is to set a framework to permit comparisons with other observations and with atmospheric models. A forward model including non-LTE radiative transfer is used to evaluate the information content within the telescopic beam, and is later convolved with the beam function and a typical wind field to discern the major contributions to the measured radiance, including limb and nadir views. The emission mostly arises from the non-LTE limb around altitudes of 75 km on Mars and 110 km on Venus. We propose a parameterization of the limb emission using few geophysical parameters which can be extended to other hypothetical CO{sub 2} planetary atmospheres. The tropospheric or LTE component of the emission varies with the temperature and is important at low solar illumination but only for the emerging radiance, not for the wind determinations since these are derived from the Doppler shift at the non-LTE line cores. We evaluated the sources of uncertainty and found that the forward model errors amount to approximately 12% of the measured winds, which is normally smaller than the instrumental errors. We applied this study to revise a set of measurements extending for three Martian years and confirmed previous results suggesting winds that are too large simulated by current Martian circulation models at equatorial latitudes during solstice. We encourage new observational campaigns, particularly for the strong jet at mid–high latitudes on Mars, and propose general guidelines and recommendations for future observations.

  12. Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations

    Science.gov (United States)

    Hayward, Rosalyn K.; Fenton, Lori; Titus, Timothy N.

    2014-01-01

    The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90°N to 90°S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ∼60,000 km2 of medium to large-size dark dune fields and ∼15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ∼70,000 km2), and north pole (NP, ∼845,000 km2) portions of the database, bringing the global total to ∼975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40°S and 80°S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.

  13. CFOSAT: a new Chinese-French satellite for joint observations of ocean wind vector and directional spectra of ocean waves

    Science.gov (United States)

    Hauser, D.; Tison, C.; Amiot, T.; Delaye, L.; Mouche, A.; Guitton, G.; Aouf, L.; Castillan, P.

    2016-05-01

    CFOSAT (the China France Oceanography Satellite) is a joint mission from the Chinese and French Space Agencies, devoted to the observation ocean surface wind and waves so as to improve wind and wave forecast for marine meteorology, ocean dynamics modeling and prediction, climate variability knowledge, fundamental knowledge of surface processes. Currently under Phase D (manufacturing phase), the launch is now planned for mid-2018 the later. The CFOSAT will carry two payloads, both Ku-Band radar: the wave scatterometer (SWIM) and the wind scatterometer (SCAT). Both instruments are based on new concepts with respect to existing satellite-borne wind and wave sensors. Indeed, one of the originalities of CFOSAT is that it will provide simultaneously and in the same zone, the directional spectra of ocean waves and the wind vector. The concept used to measure the directional spectra of ocean waves has never been used from space until now: it is based on a near-nadir incidence pointing, rotating fan-beam radar, used in a real-aperture mode. In this paper we present the CFOSAT mission, its objectives and main characteristics. We then focus on the SWIM instrument, the expected geophysical products and performances. Finally, we present ongoing studies based on existing satellite data of directional spectra of ocean waves (Sentinel-1, ..) and carried out in preparation to CAL/VAL activities and to future data exploitation.

  14. Solar wind dependence of ion parameters in the Earth's magnetospheric region calculated from CLUSTER observations

    Directory of Open Access Journals (Sweden)

    M. H. Denton

    2008-03-01

    Full Text Available Moments calculated from the ion distributions (~0–40 keV measured by the Cluster Ion Spectrometry (CIS instrument are combined with data from the Cluster Flux Gate Magnetometer (FGM instrument and used to characterise the bulk properties of the plasma in the near-Earth magnetosphere over five years (2001–2005. Results are presented in the form of 2-D xy, xz and yz GSM cuts through the magnetosphere using data obtained from the Cluster Science Data System (CSDS and the Cluster Active Archive (CAA. Analysis reveals the distribution of ~0–40 keV ions in the inner magnetosphere is highly ordered and highly responsive to changes in solar wind velocity. Specifically, elevations in temperature are found to occur across the entire nightside plasma sheet region during times of fast solar wind. We demonstrate that the nightside plasma sheet ion temperature at a downtail distance of ~12 to 19 Earth radii increases by a factor of ~2 during periods of fast solar wind (500–1000 km s−1 compared to periods of slow solar wind (100–400 km s−1. The spatial extent of these increases are shown in the xy, xz and yz GSM planes. The results from the study have implications for modelling studies and simulations of solar-wind/magnetosphere coupling, which ultimately rely on in situ observations of the plasma sheet properties for input/boundary conditions.

  15. Evolution of Intermittency in the Slow and Fast Solar Wind Beyond the Ecliptic Plane

    CERN Document Server

    Wawrzaszek, Anna; Macek, Wiesław M; Bruno, Roberto

    2016-01-01

    We study intermittency as a departure from self-similarity of the solar wind magnetic turbulence and investigate the evolution with the heliocentric distance and latitude. We use data from the Ulysses spacecraft measured during two solar minima (1997-1998 and 2007-2008) and one solar maximum (1999-2001). In particular, by modeling a multifractal spectrum, we revealed the intermittent character of turbulence in the small-scale fluctuations of the magnetic field embedded in the slow and fast solar wind. Generally, at small distances from the Sun, in both the slow and fast solar wind, we observe the high degree of multifractality (intermittency) that decreases somewhat slowly with distance and slowly with latitude. The obtained results seem to suggest that generally intermittency in the solar wind has a solar origin. However, the fast and slow streams, shocks, and other nonlinear interactions can only be considered as the drivers of the intermittent turbulence. It seems that analysis shows that turbulence beyond...

  16. Looking at Animals without Seeing Them: Havelock Ellis in the “Circe” Episode of Ulysses

    Directory of Open Access Journals (Sweden)

    Ronan Crowley

    2017-09-01

    Full Text Available Taking wing from Joyce’s reading of Havelock Ellis’s Studies in the Psychology of Sex, in which the Irish writer found an account of cross-species sexual contact, this essay explores Leopold Bloom’s animal metamorphosis in the “Circe” episode of Ulysses. It argues that this encounter with the nonhuman animal is subordinated to the cause of working through barriers of human difference. In the process, the animal that enables this reconciliation disappears. Unable to represent animal interiority, “Circe” settles for merely probing their interiors.

  17. First observation of mesospheric wind shear as high as 330 m s−1 km−1

    Directory of Open Access Journals (Sweden)

    D. Offermann

    Full Text Available Mesospheric wind profiles with an altitude resolution of 25 m have been obtained by means of radar tracking of foil chaff clouds. Such experiments were performed during winter 1990 at Biscarrosse, France (44°N, 1°W. On one flight, a wind shear as high as 330 m s–1 km–1 at 87.4 km and a region of dynamical instability between 86 and 88 km was measured. This wind shear is believed to be the largest value ever measured in the mesosphere. The region of dynamical instability results from a superposition of two wave motions, and is found to link well with enhanced turbulence and small-scale wave activity.

  18. Interpretation of the mesospheric and lower thermospheric mean winds observed with MF radar at about 30N with the 2D-SOCRATES model

    Science.gov (United States)

    Xiao, C.; Hu, X.; Zhang, X.; Zhang, D.; Wu, X.; G, X.

    Data obtained from Japanese Yamagawa 31 2 0 N 130 6 0 W MF radar and Chinese Wuhan 30 5 0 N 114 4 0 W MF radar have been used to study the mean winds in the MLT at about 30 0 N The observed mean winds show obvious seasonal variations Westerly wind prevails in winter and decreases with the increasing heights even reverses near the 95km altitude sometimes During summer the mean zonal wind is westward in the mesosphere and eastward in the lower thermosphere with the reversing height about 79km From 70km to 95km the mean meridional wind blows northwards in winter and southwards in summer Northerly wind prevails above about 95km The winds in spring and autumn are the transitions between summer and winter winds structures These wind features are due to the atmospheric photochemistry radiation and dynamics The NCAR interactive chemical-dynamical-radiative 2-D model SOCRATES is used to investigate the effects of the radiation and dynamics on the MLT circulations and to interpret the above observations When both of the radiation and dynamics are considered in the model simulation the resulting zonal-mean winds are similar to the mean winds observed by MF radar When not considering the dynamics the results reveal that the radiative-balanced winds increase with the increasing heights which disagree with the observational winds Large climatological values of forcing are required to account for such discrepancies The gravity waves play a dominant role in contributing to the forcing which provide a drag of the order of

  19. Horns Rev 2 offshore wind farm photo case with wakes observed in 2016

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Nygaard, Nicolai Gayle; Volker, Patrick

    Offshore wind farm wakes were photographed in foggy conditions at Horns Rev 2 on 25 January 2016 at 12:45 UTC (See1). The study examines the atmospheric conditions from satellite images, radiosonde, vertical profiling wind lidar located at the transformer platform and SCADA data. Furthermore...... results from atmospheric WRF meso-scale modelling, Park wake model and large eddy simulation wake model are prepared and analysed. At the time of the photos a humid and warm air mass was advected from the southwest over cold sea. The dew-point temperature was such that cold-water advection fog formed...

  20. An observational study of the variability of ocean wind stress and sea surface roughness

    Science.gov (United States)

    Chen, Wei

    1997-11-01

    The processes that are responsible for air-sea interaction in the planetary boundary layer are very complex, yet these processes shape the global weather and climate evolution. While appearing to be relatively well understood, the mean wind speed, wind stress and sea state over large averaging scales often show considerable scatter. Their variability over shorter averaging scales has received far less attention, yet an enhanced knowledge of their local behaviours and mutual relationship should improve our understanding of the mechanisms underlying air-sea interaction on a larger scale. To pursue these objectives, a comprehensive airborne air- sea interaction experiment called SOWEX was carried out over the Southern Ocean, off the west coast of Tasmania during June, 1992, during which the 10m wind speed varied from almost 20m/sec to less than 5m/sec. Based on the atmospheric data obtained from this experiment, besides reporting the traditional drag coefficient and roughness length over large averaged scales, the present study describes the localised behaviour of momentum flux associated with large scale atmospheric motions. The momentum flux within the ascending motion regions where the wind speed on the average slows down was found to be larger than that within the more extensive descending regions. This appears to be generally associated with the structure of atmospheric roll vortices. Our study of the sea state measured by an airborne scanning radar altimeter has contributed a significant extension to gale force wind speeds of the relation between wind speed and surface mean square slope (mss). The present determination of mss has been improved by including the influence of the tilts of the dominant ocean waves on the local incidence angle of the radar altimeter. A major result from the present data analysis shows that the sea surface roughness as measured by the local (2km) averaged mss responds to local wind speed variations more closely than it follows the

  1. Interpretation of the mesospheric and lower thermospheric mean winds observed by MF radar at about 30°N with the 2D-SOCRATES model

    Science.gov (United States)

    Xiao, C. Y.; Hu, X.; Zhang, X. X.; Zhang, D. Y.; Wu, X. C.; Gong, X. Y.; Igarashi, K.

    Data obtained by Wuhan (30.5°N, 114.4°E) MF radar and Yamagawa (31.2°N, 130.6°E) MF radar have been used to study the mean winds in the mesosphere and lower thermosphere (MLT) at about 30°N. The observed mean zonal and mean meridional winds show obviously seasonal variations. Westerly wind prevails in winter, and decreases with the increasing height above 76 km, even reverses above 96 km sometimes. The summer mean zonal wind is westward in the mesosphere and eastward in the lower thermosphere, with the reversal height of about 80 km. From 70 to 95 km, the mean meridional wind blows northward in winter and southward in summer. Northerly wind prevails between 95 and 98 km throughout seasons. These wind features have similar patterns to those of the empirical HWM93 wind model. 2D-SOCRATES model is used to try to give physical interpretations of the observed wind fields, with which dynamic contributions to the MLT wind structures are analyzed. Simulations show that the planetary waves play an unimportant role in the MLT region since they have relatively small magnitudes during winter and even cannot propagate upward into the upper atmosphere during summer. The gravity waves play a crucial role in determining the wind structures in the MLT region, providing forcing of about 40 m/s/day and diffusion coefficients of about 50 m 2/s at 30°N. The atmospheric tidal waves have significant influences in the wind structures with forcing of about 10 m/s/day and diffusion coefficients of about several m 2/s in the MLT at 30°N. Breakings of these atmospheric waves tend to close off the westerly jet in winter and easterly jet in summer, to produce strong wind shear in the mesopause, and to drive the meridional wind directed from the summer hemisphere to the winter hemisphere.

  2. A comparison of selected vertical wind measurement techniques on basis of the EUCAARI IMPACT observations

    Science.gov (United States)

    Arabas, S.; Baehr, C.; Boquet, M.; Dufournet, Y.; Pawlowska, H.; Siebert, H.; Unal, C.

    2009-04-01

    The poster presents a comparison of selected methods for determination of the vertical wind in the boundary layer used during the EUCAARI IMPACT campaign that took place in May 2008 in The Netherlands. The campaign covered a monthlong intensified ground-based and airborne measurements in the vicinity of the CESAR observatory in Cabauw. Ground-based vertical wind remote sensing was carried out using the Leosphere WindCube WLS70 IR Doppler lidar, Vaisala LAP3000 radar wind-profiler and the TUDelft TARA S-band radar. In-situ airborne measurements were performed using an ultrasonic anemometer (on the ACTOS helicopter underhung platform) and a 5-hole pressure probe (on the SAFIRE ATR-42 airplane radome). Several in-situ anemometers were deployed on the 200-meter high tower of the CESAR observatory. A summary of the characteristics and principles of the considered techniques is presented. A comparison of the results obtained from different platforms depicts the capabilities of each technique and highlights the time, space and velocity resolutions.

  3. Variance Analysis of Wind and Natural Gas Generation under Different Market Structures: Some Observations

    Energy Technology Data Exchange (ETDEWEB)

    Bush, B.; Jenkin, T.; Lipowicz, D.; Arent, D. J.; Cooke, R.

    2012-01-01

    Does large scale penetration of renewable generation such as wind and solar power pose economic and operational burdens on the electricity system? A number of studies have pointed to the potential benefits of renewable generation as a hedge against the volatility and potential escalation of fossil fuel prices. Research also suggests that the lack of correlation of renewable energy costs with fossil fuel prices means that adding large amounts of wind or solar generation may also reduce the volatility of system-wide electricity costs. Such variance reduction of system costs may be of significant value to consumers due to risk aversion. The analysis in this report recognizes that the potential value of risk mitigation associated with wind generation and natural gas generation may depend on whether one considers the consumer's perspective or the investor's perspective and whether the market is regulated or deregulated. We analyze the risk and return trade-offs for wind and natural gas generation for deregulated markets based on hourly prices and load over a 10-year period using historical data in the PJM Interconnection (PJM) from 1999 to 2008. Similar analysis is then simulated and evaluated for regulated markets under certain assumptions.

  4. Wind and Wave Characteristics Observed During the LUMINY Gas Transfer Experiments

    NARCIS (Netherlands)

    Caulliez, G.; Jaouen, L.; Larsen, S.E.; Hansen, F.Aa.; Lund, S.; Leeuw, G. de; Woolf, D.K.; Bowyer, P.A.; Leifer, I.; Kunz, G.J.; Nightingale, P.D.; Rhee, T.S.; Liddicoat, M.I.; Baker, J.; Rapsomanikis, S.; Hassoun, S.; Cohen, L.H.

    1999-01-01

    The parameterization of the greenhouse gas fluxes between the atmosphere and oceans as function of wind and sea state parameters remains a challenging problem, of key importance for climate modelling. It is well-known that exchange across the air-water interface of gases of poor solubility as carbon

  5. Observations of wind and waves in the central Bay of Bengal during ...

    Indian Academy of Sciences (India)

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

    during its transmission in the surface duct. The present analysis aiming for estimation .... 20minute period is used for computing the signif- icant wave height (Hs) and period (Ts) .... Variations of wind speed, significant wave height, significant wave period and mixed-layer depth in the central. Bay of Bengal. swell waves from ...

  6. A Vortical Dawn Flank Boundary Layer for Near-Radial IMF: Wind Observations on 24 October 2001

    Science.gov (United States)

    Farrugia, C. J.; Gratton, F. T.; Gnavi, G.; Torbert, R. B.; Wilson, Lynn B., III

    2014-01-01

    We present an example of a boundary layer tailward of the dawn terminator which is entirely populated by rolled-up flow vortices. Observations were made by Wind on 24 October 2001 as the spacecraft moved across the region at the X plane approximately equal to -13 Earth radii. Interplanetary conditions were steady with a near-radial interplanetary magnetic field (IMF). Approximately 15 vortices were observed over the 1.5 hours duration of Wind's crossing, each lasting approximately 5 min. The rolling up is inferred from the presence of a hot tenuous plasma being accelerated to speeds higher than in the adjoining magnetosheath, a circumstance which has been shown to be a reliable signature of this in single-spacecraft observations. A blob of cold dense plasma was entrained in each vortex, at whose leading edge abrupt polarity changes of field and velocity components at current sheets were regularly observed. In the frame of the average boundary layer velocity, the dense blobs were moving predominantly sunward and their scale size along the X plane was approximately 7.4 Earth radii. Inquiring into the generation mechanism of the vortices, we analyze the stability of the boundary layer to sheared flows using compressible magnetohydrodynamic Kelvin-Helmholtz theory with continuous profiles for the physical quantities. We input parameters from (i) the exact theory of magnetosheath flow under aligned solar wind field and flow vectors near the terminator and (ii) the Wind data. It is shown that the configuration is indeed Kelvin-Helmholtz (KH) unstable. This is the first reported example of KH-unstable waves at the magnetopause under a radial IMF.

  7. Observation and modeling of tide- and wind-induced surface currents in Galway Bay

    Directory of Open Access Journals (Sweden)

    Lei REN

    2015-10-01

    Full Text Available A high-frequency radar system has been deployed in Galway Bay, a semi-enclosed bay on the west coast of Ireland. The system provides surface currents with fine spatial resolution every hour. Prior to its use for model validation, the accuracy of the radar data was verified through comparison with measurements from acoustic Doppler current profilers (ADCPs and a good correlation between time series of surface current speeds and directions obtained from radar data and ADCP data. Since Galway Bay is located on the coast of the Atlantic Ocean, it is subject to relatively windy conditions, and surface currents are therefore strongly wind-driven. With a view to assimilating the radar data for forecasting purposes, a three-dimensional numerical model of Galway Bay, the Environmental Fluid Dynamics Code (EFDC, was developed based on a terrain-following vertical (sigma coordinate system. This study shows that the performance and accuracy of the numerical model, particularly with regard to tide- and wind-induced surface currents, are sensitive to the vertical layer structure. Results of five models using different layer structures are presented and compared with radar measurements. A variable vertical structure with thin layers at the bottom and the surface and thicker layers in the middle of the water column was found to be the optimal layer structure for reproduction of tide- and wind-induced surface currents. This structure ensures that wind shear can properly propagate from the surface layer to the sub-surface layers, thereby ensuring that wind forcing is not overdamped by tidal forcing. The vertical layer structure affects not only the velocities at the surface layer but also the velocities further down in the water column.

  8. Observation and modeling of tide- and wind-induced surface currents in Galway Bay

    Directory of Open Access Journals (Sweden)

    Lei Ren

    2015-10-01

    Full Text Available A high-frequency radar system has been deployed in Galway Bay, a semi-enclosed bay on the west coast of Ireland. The system provides surface currents with fine spatial resolution every hour. Prior to its use for model validation, the accuracy of the radar data was verified through comparison with measurements from acoustic Doppler current profilers (ADCPs and a good correlation between time series of surface current speeds and directions obtained from radar data and ADCP data. Since Galway Bay is located on the coast of the Atlantic Ocean, it is subject to relatively windy conditions, and surface currents are therefore strongly wind-driven. With a view to assimilating the radar data for forecasting purposes, a three-dimensional numerical model of Galway Bay, the Environmental Fluid Dynamics Code (EFDC, was developed based on a terrain-following vertical (sigma coordinate system. This study shows that the performance and accuracy of the numerical model, particularly with regard to tide- and wind-induced surface currents, are sensitive to the vertical layer structure. Results of five models with different layer structures are presented and compared with radar measurements. A variable vertical structure with thin layers at the bottom and the surface and thicker layers in the middle of the water column was found to be the optimal layer structure for reproduction of tide- and wind-induced surface currents. This structure ensures that wind shear can properly propagate from the surface layer to the sub-surface layers, thereby ensuring that wind forcing is not overdamped by tidal forcing. The vertical layer structure affects not only the velocities at the surface layer but also the velocities further down in the water column.

  9. Geology of the small Tharsis volcanoes: Jovis Tholus, Ulysses Patera, Biblis Patera, Mars

    Science.gov (United States)

    Plescia, J. B.

    1994-01-01

    Jovis Tholus, Ulysses Patera, and Biblis Patera, three small volcanoes in the Tharsis area of Mars, provide important insight into the evolution of volcanism on Mars. All three are interpreted to be shield volcanoes, indicating that shield volcansim was present from the outset in Tharsis. Jovis Tholus is the least complex with simple repeated outpouring of lavas and caldera-forming events. Ulysses Patera is dominated by a giant caldera within which is a line of cinder cones or domes suggesting terminal stages of volcanism in which the magma had either significant volatiles or increased viscosity. Biblis Patera is characterized by nested calderas which have expanded by block faulting of the flank; it also exhibits lava flows erupted onto the flanks from events along concentric fractures. These shields are different from the younger Tharsis Montes shields only in terms of the volume of erupted material. The limited shield volume suggests that the magma source which fed the shields was rapidly depleted. The relatively large size ofthe calderas probably results from relatively large, shallow magma bodies rather than significant burial of the flanks by younger lavas. Eruption rates consistent with typical terrestrial basaltic eruptiuon rates suggest that these volcanoes were probably built over time spans of 10(exp 4) to 10(exp 5) years. Stratigraphic ages range from Early to Upper Hesperian; absolute ages range from 1.9 to 3.4 Ga.

  10. [Rethinking the challenges of Ulysses and Faust: health, the individual and history].

    Science.gov (United States)

    Melo-Filho, D A

    1995-01-01

    Concentrating on two historical synecdoches, Ulysses and Faust, this article takes up the etymology of the Latin term salute as a unit lying somewhere between "existential needs" and "especially human needs", leading to the challenge of satisfying the need for "conservation of life" and at the same time to "surpass it, go beyond it". Both meanings are present in Ulysses attitude of not succumbing to the siren s melody and in Faust s desire to rise above everyday life. Some aspects of the Marxist conception of the philosophy of history and Althusser s Structuralist Marxism are criticized. Also, in light of Marxist-Hellerian theory, the article analyzes the hypothesis that the target of the final reports of the VIII National Health Conference was "particular man" and not the individual, since health is treated only as "an existential need", and does not envisage the generic human. As a theoretical challenge, the text, in search of the unfolding individual, finally recommends the construction of "epistemological sutures" between nature and society, everyday life and universality, and the young and old Marx.

  11. The Eyes of That Cow: Eating Animals and Theorizing Vegetarianism in James Joyce’s Ulysses

    Directory of Open Access Journals (Sweden)

    Peter Adkins

    2017-07-01

    Full Text Available At the end of the nineteenth century more than half of Ireland’s entire land surface was being used for the raising of livestock, most of which was transported through Dublin on its way to England to be slaughtered and eaten. The same period saw the development of a new social phenomena of vegetarianism amongst Ireland’s intellectuals and literary figures. This article focuses on James Joyce’s portrayal of livestock, meat and vegetarianism in Ulysses, examining how the novel engages with the politics of cattle raising, the emergence of industrialized animal slaughter and the ethics of meat eating at the turn of the twentieth century. Attending to the ways in which Joyce both historicizes and theorizes the lives of animals and the production of meat, this article places Ulysses in dialogue with recent writings on animal ethics by Jacques Derrida and J. M. Coetzee and the emergence of what is being termed “vegan studies” to suggest a vegetarian reading of Joyce’s novel.

  12. CWEX: Crop/wind-energy experiment: Observations of surface-layer, boundary-layer and mesoscale interactions with a wind farm

    Science.gov (United States)

    Large wind turbines perturb mean and turbulent wind characteristics, which modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could create significant changes in surface fluxes of heat, momentum, moisture, and CO2 over hundreds ...

  13. Crop/Wind-energy Experiment (CWEX): Observations of surface-layer, boundary-layer and mesoscale interactions with a wind farm

    Science.gov (United States)

    Perturbations of mean and turbulent wind characteristics by large wind turbines modify fluxes between the vegetated surface and the lower boundary layer. While simulations have suggested that wind farms could significantly change surface fluxes of heat, momentum, moisture, and CO2 over hundreds of s...

  14. On the Long-Term Variability of Jupiter's Winds and Brightness as Observed from Hubble

    Science.gov (United States)

    Simon-Miller, Amy A.; Gierasch, Peter J.

    2010-01-01

    Hubble Space Telescope Wide Field Planetary Camera 2 imaging data of Jupiter were combined with wind profiles from Voyager and Cassini data to study long-term variability in Jupiter's winds and cloud brightness. Searches for evidence of wind velocity periodicity yielded a few latitudes with potential variability; the most significant periods were found nearly symmetrically about the equator at 0 deg., 10-12 deg. N, and 14-18 deg. S planetographic latitude. The low to mid-latitude signals have components consistent with the measured stratospheric temperature Quasi-Quadrennial Oscillation (QQO) period of-5 years, while the equatorial signal is approximately seasonal and could be tied to mesoscale wave formation, robustness tests indicate that a constant or continuously varying periodic signal near 4.5 years would appear with high significance in the data periodograms as long as uncertainties or noise in the data are not of greater magnitude. However, the lack of a consistent signal over many latitudes makes it difficult to interpret as a QQO-related change. In addition, further analyses of calibrated 410-nm and 953-nm brightness scans found few corresponding changes in troposphere haze and cloud structure on QQO timescales. However, stratospheric haze reflectance at 255-nm did appear to vary on seasonal timescales, though the data do not have enough temporal coverage or photometric accuracy to be conclusive. Sufficient temporal coverage and spacing, as well as data quality, are critical to this type of search.

  15. First observation of mesospheric wind shear as high as 330 m s-1 km-1

    Science.gov (United States)

    Wu, Yong-Fu; Widdel, H.-U.; Offermann, D.

    1995-09-01

    Mesospheric wind profiles with an altitude resolution of 25 m have been obtained by means of radar tracking of foil chaff clouds. Such experiments were performed during winter 1990 at Biscarrosse, France (44°N, 1°W). On one flight, a wind shear as high as 330 m s-1 km-1 at 87.4 km and a region of dynamical instability between 86 and 88 km was measured. This wind shear is believed to be the largest value ever measured in the mesosphere. The region of dynamical instability results from a superposition of two wave motions, and is found to link well with enhanced turbulence and small-scale wave activity. Acknowledgements. I thank D. R. McDiarmid of the Herzberg Institute of Astrophysics, National Research Council, Canada, for important ideas and discussions during the development of this work. I thank the referees for useful comments which have improved the paper. I also thank E.M. Poulter of NIWA for helpful suggestions, and for reading the manuscript and making useful comments. The work was supported by contract CO1309 of the New Zealand Foundation for Research, Science and Technology. Topical Editor C.-G. Fälthammar thanks K. Mursula and W. J. Hughes for their help in evaluating this paper.--> Correspondence to: W. Allan-->

  16. Relation of zonal plasma drift and wind in the equatorial F region as derived from CHAMP observations

    Directory of Open Access Journals (Sweden)

    J. Park

    2013-06-01

    Full Text Available In this paper we estimate zonal plasma drift in the equatorial ionospheric F region without counting on ion drift meters. From June 2001 to June 2004 zonal plasma drift velocity is estimated from electron, neutral, and magnetic field observations of Challenging Mini-satellite Payload (CHAMP in the 09:00–20:00 LT sector. The estimated velocities are validated against ion drift measurements by the Republic of China Satellite-1/Ionospheric Plasma and Electrodynamics Instrument (ROCSAT-1/IPEI during the same period. The correlation between the CHAMP (altitude ~ 400 km estimates and ROCSAT-1 (altitude ~ 600 km observations is reasonably high (R ≈ 0.8. The slope of the linear regression is close to unity. However, the maximum westward drift and the westward-to-eastward reversal occur earlier for CHAMP estimates than for ROCSAT-1 measurements. In the equatorial F region both zonal wind and plasma drift have the same direction. Both generate vertical currents but with opposite signs. The wind effect (F region wind dynamo is generally larger in magnitude than the plasma drift effect (Pedersen current generated by vertical E field, thus determining the direction of the F region vertical current.

  17. Employment of satellite snowcover observations for improving seasonal runoff estimates. [Indus River and Wind River Range, Wyoming

    Science.gov (United States)

    Rango, A.; Salomonson, V. V.; Foster, J. L.

    1975-01-01

    Low resolution meteorological satellite and high resolution earth resources satellite data were used to map snowcovered area over the upper Indus River and the Wind River Mountains of Wyoming, respectively. For the Indus River, early Spring snowcovered area was extracted and related to April through June streamflow from 1967-1971 using a regression equation. Composited results from two years of data over seven Wind River Mountain watersheds indicated that LANDSAT-1 snowcover observations, separated on the basis of watershed elevation, could also be related to runoff in significant regression equations. It appears that earth resources satellite data will be useful in assisting in the prediction of seasonal streamflow for various water resources applications, nonhazardous collection of snow data from restricted-access areas, and in hydrologic modeling of snowmelt runoff.

  18. Numerical and Observational Investigations of Long-Lived Mcs-Induced Severe Surface Wind Events: the Derecho

    Science.gov (United States)

    Schmidt, Jerome Michael

    This study addresses the production of sustained, straight-line, severe surface winds associated with mesoscale convective systems (MCSs) of extratropical origin otherwise known as derechos. The physical processes which govern the observed derecho characteristics are identified and their possible forcing mechanisms are determined. Detailed observations of two derechos are presented along with simulations using the Colorado State University Regional Atmospheric Modeling System (CSU-RAMS). The observations revealed a derecho environment characterized by strong vertical wind shear through the depth of the troposphere and large values of convective available potential energy (CAPE). The thermodynamic environment of the troposphere in each case had a distinct three-layer structure consisting of: (i) a surface-based stable layer of 1-to-2 km in depth, (ii) an elevated well -mixed layer of 2-4 km in depth, and (iii) an upper tropospheric layer of intermediate stability that extended to the tropopause. Two primary sets of simulations were performed to assess the impact of the observed environmental profiles on the derecho structure, propagation, and longevity. The first set consisted of nested-grid regional-scale simulations initialized from the standard NMC analyses on a domain having relatively coarse horizontal resolution (75 km). The second set of simulations consisted of two and three-dimensional experiments initialized in a horizontally homogeneous environment having a relatively fine horizontal resolution (2 km) and explicit microphysics. The results from these experiments indicate the importance of convectively -induced gravity waves on the MCS structure, propagation, longevity, and severe surface wind development. The sensitivity of the simulated convection and gravity waves to variations in the vertical wind shear and moisture profiles are described. Detailed Doppler radar analyses and 3-D simulations of a severe, bow echo squall line are presented which reveal

  19. Chaos Theory and James Joyce's "ulysses": Leopold Bloom as a Human COMPLEX@SYSTEM^

    Science.gov (United States)

    Mackey, Peter Francis

    1995-01-01

    These four ideas apply as much to our lives as to the life of Leopold Bloom: (1) A trivial decision can wholly change a life. (2) A chance encounter can dramatically alter life's course. (3) A contingent nexus exists between consciousness and environment. (4) A structure of meaning helps us interpret life's chaos. These ideas also relate to a contemporary science called by some "chaos theory." The connection between Ulysses and chaos theory enhances our understanding of Bloom's day; it also suggests that this novel may be about the real process of life itself. The first chapter explains how Joyce's own essays and comments to friends compel attention to the links between Ulysses and chaos theory. His scientific contemporaries anticipated chaos theory, and their ideas seem to have rubbed off on him. We see this in his sense of trivial things and chance, his modernistic organizational impulses, and the contingent nature of Bloom's experience. The second chapter studies what chaos theory and Joyce's ideas tell us about "Ithaca," the episode which particularly implicates our processes of interpreting this text as well as life itself as we face their chaos. The third chapter examines Bloom's close feel for the aboriginal world, a contingency that clarifies his vulnerability to trivial changes. The fourth chapter studies how Bloom's stream of consciousness unfolds--from his chance encounters with trivial things. Beneath this stream's seeming chaos, Bloom's distinct personality endures, similar to how Joyce's schemas give Ulysses an imbedded, underlying order. The fifth chapter examines how trivial perturbations, such as Lyons' misunderstanding about "Throwaway," produce small crises for Bloom, exacerbating his seeming impotence before his lonely "fate.". The final chapter analyzes Bloom's views that fate and chance dictate his life. His views provide an opportunity to explore the implications chaos theory has for our understanding of free will and determinism. Ultimately

  20. Analysis of a Transonic Alternating Flow Phenomenon Observed During Ares Crew Launch Vehicle Wind Tunnel Tests

    Science.gov (United States)

    Sekula, Martin K.; Piatak, David J.; Rausch, Russ D.

    2010-01-01

    A transonic wind tunnel test of the Ares I-X Rigid Buffet Model (RBM) identified a Mach number regime where unusually large buffet loads are present. A subsequent investigation identified the cause of these loads to be an alternating flow phenomenon at the Crew Module-Service Module junction. The conical design of the Ares I-X Crew Module and the cylindrical design of the Service Module exposes the vehicle to unsteady pressure loads due to the sudden transition from separated to attached flow about the cone-cylinder junction with increasing Mach number. For locally transonic conditions at this junction, the flow randomly fluctuates back and forth between a subsonic separated flow and a supersonic attached flow. These fluctuations produce a square-wave like pattern in the pressure time histories which, upon integration result in large amplitude, impulsive buffet loads. Subsequent testing of the Ares I RBM found much lower buffet loads since the evolved Ares I design includes an ogive fairing that covers the Crew Module-Service Module junction, thereby making the vehicle less susceptible to the onset of alternating flow. An analysis of the alternating flow separation and attachment phenomenon indicates that the phenomenon is most severe at low angles of attack and exacerbated by the presence of vehicle protuberances. A launch vehicle may experience either a single or, at most, a few impulsive loads since it is constantly accelerating during ascent rather than dwelling at constant flow conditions in a wind tunnel. A comparison of a wind-tunnel-test-data-derived impulsive load to flight-test-data-derived load indicates a significant over-prediction in the magnitude and duration of the buffet load

  1. Vertical velocity and turbulence aspects during Mistral events as observed by UHF wind profilers

    Directory of Open Access Journals (Sweden)

    J.-L. Caccia

    2004-11-01

    Full Text Available The general purpose of this paper is to experimentally study mesoscale dynamical aspects of the Mistral in the coastal area located at the exit of the Rhône-valley. The Mistral is a northerly low-level flow blowing in southern France along the Rhône-valley axis, located between the French Alps and the Massif Central, towards the Mediterranean Sea. The experimental data are obtained by UHF wind profilers deployed during two major field campaigns, MAP (Mesoscale Alpine Program in autumn 1999, and ESCOMPTE (Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transports d'Emission in summer 2001. Thanks to the use of the time evolution of the vertical profile of the horizontal wind vector, recent works have shown that the dynamics of the Mistral is highly dependent on the season because of the occurrence of specific synoptic patterns. In addition, during summer, thermal forcing leads to a combination of sea breeze with Mistral and weaker Mistral due to the enhanced friction while, during autumn, absence of convective turbulence leads to substantial acceleration as low-level jets are generated in the stably stratified planetary boundary layer. At the exit of the Rhône valley, the gap flow dynamics dominates, whereas at the lee of the Alps, the dynamics is driven by the relative contribution of "flow around" and "flow over" mechanisms, upstream of the Alps. This paper analyses vertical velocity and turbulence, i.e. turbulent dissipation rate, with data obtained by the same UHF wind profilers during the same Mistral events. In autumn, the motions are found to be globally and significantly subsident, which is coherent for a dry, cold and stable flow approaching the sea, and the turbulence is found to be of pure dynamical origin (wind shears and mountain/lee wave breaking, which is coherent with non-convective situations. In summer, due to the ground heating and to the interactions with thermal circulation, the

  2. Onshore Wind Stress and Buoyancy Flux Observed on a Dissipative Mediterranean Beach

    Science.gov (United States)

    2015-12-01

    There are a few people I’d be remiss if I did not thank personally. On the oceanography side, to Mr. Keith Wyckoff for his enthusiasm and for...1610, doi:10.1175/JPO-D-12-0173.1. Fairall, C. W., E. F. Bradley, J. E. Hare , A. A. Grachev, and J. B. Edson, 2003: Bulk parameterization of air–sea...doi:10.1029/93JC01439. Grachev, A., C. Fairall, J. Hare , J. Edson, and S. Miller, 2003: Wind stress vector over ocean waves. J. Phys. Oceanogr

  3. VHF radar observation of atmospheric winds, associated shears and C2n at a tropical location: interdependence and seasonal pattern

    Directory of Open Access Journals (Sweden)

    A. R. Jain

    Full Text Available The turbulence refractivity structure constant (C2n is an important parameter of the atmosphere. VHF radars have been used extensively for the measurements of C2n. Presently, most of such observations are from mid and high latitudes and only very limited observations are available for equatorial and tropical latitudes. Indian MST radar is an excellent tool for making high-resolution measurements of atmospheric winds, associated shears and turbulence refractivity structure constant (C2n. This radar is located at Gadanki (13.45° N, 79.18° E, a tropical station in India. The objective of this paper is to bring out the height structure of C2n for different seasons using the long series of data (September 1995 – August 1999 from Indian MST radar. An attempt is also made to understand such changes in the height structure of C2n in relation to background atmospheric parameters such as horizontal winds and associated shears. The height structure of C2n, during the summer monsoon and post-monsoon season, shows specific height features that are found to be related to Tropical Easterly Jet (TEJ winds. It is important to examine the nature of the radar back-scatterers and also to understand the causative mechanism of such scatterers. Aspect sensitivity of the received radar echo is examined for this purpose. It is observed that radar back-scatterers at the upper tropospheric and lower stratospheric heights are more anisotropic, with horizontal correlation length of 10–20 m, as compared to those observed at lower and middle tropospheric heights.Key words. Meteorology and atmospheric dynamics (climatology; tropical meteorology; turbulence

  4. Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations

    Science.gov (United States)

    Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

    2012-01-01

    One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

  5. Observations of C-Band Brightness Temperature and Ocean Surface Wind Speed and Rain Rate in Hurricanes Earl And Karl (2010)

    Science.gov (United States)

    Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem

    2012-01-01

    Ocean surface emission is affected by: a) Sea surface temperature. b) Wind speed (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields wind speed and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface wind, temp and rain b) Advances understanding & prediction of hurricane intensity c) Expands Stepped Frequency Microwave Radiometer capabilities d) Uses synthetic thinned array and RFI mitigation technology of Lightweight Rain Radiometer (NASA Instrument Incubator) Passive Microwave C-Band Radiometer with Freq: 4, 5, 6 & 6.6 GHz: a) Version 1: H-pol for ocean wind speed, b) Version 2: dual ]pol for ocean wind vectors. Performance Characteristics: a) Earth Incidence angle: 0deg - 60deg, b) Spatial Resolution: 2-5 km, c) Swath: approx.70 km for 20 km altitude. Observational Goals: WS 10 - >85 m/s RR 5 - > 100 mm/hr.

  6. HF Radar Observations of Current, Wave and Wind Parameters in the South Australian Gulf

    Science.gov (United States)

    Middleditch, A.; Cosoli, S.

    2016-12-01

    The Australian Coastal Ocean Radar Network (ACORN) has been measuring metocean parameters from an array of HF radar systems since 2007. Current, wave and wind measurements from a WERA phased-array radar system in the South Australian Gulf are evaluated using current meter, wave buoy and weather station data over a 12-month period. The spatial and temporal scales of the radar deployment have been configured for the measurement of surface currents from the first order backscatter spectra. Quality control procedures are applied to the radar currents that relate to the geometric configurations, statistical properties, and diagnostic variables provided by the analysis software. Wave measurements are obtained through an iterative inversion algorithm that provides an estimate of the directional frequency spectrum. The standard static configurations and data sampling strategies are not optimised for waves and so additional signal processing steps need to be implemented in order to provide reliable estimates. These techniques are currently only applied in offline mode but a real-time approach is in development. Improvements in the quality of extracted wave data are found through increased averaging of the raw radar data but the impact of temporal non-stationarity and spatial inhomogeneities in the WERA measurement region needs to be taken into account. Validations of wind direction data from a weather station on Neptune Island show the potential of using HF radar to combat the spread of bushfires in South Australia.

  7. Neutral wind and density perturbations in the thermosphere created by gravity waves observed by the TIDDBIT sounder

    Science.gov (United States)

    Vadas, Sharon L.; Crowley, Geoff

    2017-06-01

    In this paper, we study the 10 traveling ionospheric disturbances (TIDs) observed at zobs˜283 km by the TIDDBIT ionospheric sounder on 30 October 2007 at 0400-0700 UT near Wallops Island, USA. These TIDs propagated northwest/northward and were previously found to be secondary gravity waves (GWs) from tropical storm Noel. An instrumented sounding rocket simultaneously measured a large neutral wind peak uH' with a similar azimuth at z ˜ 325 km. Using the measured TID amplitudes and wave vectors from the TIDDBIT system, together with ion-neutral theory, GW dissipative polarization relations and ray tracing, we determine the GW neutral horizontal wind and density perturbations as a function of altitude from 220 to 380 km. We find that there is a serious discrepancy between the GW dissipative theory and the observations unless the molecular viscosity, μ, decreases with altitude in the middle to upper thermosphere. Assuming that μ∝ρ¯q, where ρ¯ is the density, we find using GW dissipative theory that the GWs could have been observed at zobs and that one or more of the GWs could have caused the uH' wind peak at z≃325 km if q ˜ 0.67 for z≥220 km. This implies that the kinematic viscosity, ν=μ/ρ¯, increases less rapidly with altitude for z≥220 km: ν∝1/ρ¯0.33. This dependence makes sense because as ρ¯→0, the distance between molecules goes to infinity, which implies no molecular collisions and therefore no molecular viscosity μ.

  8. Multi-Point Observations of Transient Phenomena at the Magnetopause Associated With Solar Wind Dynamic Pressure Impulse Events

    Science.gov (United States)

    Kim, H.; Clauer, C. R.; Lessard, M.; Engebretson, M. J.; Matzka, J.; Sibeck, D. G.; Singer, H. J.; Stolle, C.; Hartinger, M.; Weimer, D. R.; Xu, Z.

    2015-12-01

    We report multi-point conjugate observations of transient phenomena at the magnetopause using datasets from the Time History of Events and Macroscale Interactions during Substorms (THEMIS), Cluster, Geostationary Operational Environmental Satellite (GOES) spacecraft and interhemispheric ground magnetometer array. Simultaneous with the inward displacement of the magnetopause produced by an increase in solar wind dynamic pressure, we observe the generation of a pair of traveling convection vortices (TCVs) in both polar ionospheres. The TCV events are characterized by their single or twin vortex, of which the centers are located approximately at 72-76 degrees magnetic latitudes, propagating either dawnward or duskward away from local noon. ULF Pc1 waves identified as electromagnetic ion cyclotron (EMIC) waves in association with the initiation of the TCVs were also observed on the ground. It appears that the waves are generated by the increased instability caused by the compression of the magnetosphere during the transient events. We discuss the spatiotemporal structures of the transient phenomena near the magnetopause and their magnetospheric and ionospheric responses, concluding that the signatures are closely associated with the sudden increase of solar wind dynamic pressure.

  9. Observations of the properties of the water surface roughness structure under the action of wind and waves

    Science.gov (United States)

    Long, Steven R.; Huang, Norden E.

    1988-01-01

    The statistical properties of a water surface roughness structure subjected to wind and waves are analyzed in a laboratory wind wave channel. The surface slope is derived using elevation measurements and the pitot tube is employed to measure wind speed. The transient responses of the surface slope to a calm condition and low, medium, and high wind conditions are studied. Two methods for determining a critical wind speed range are described.

  10. Heterogeneous Boundary Layers through the Diurnal Cycle: Evaluation of the WRF Wind Farm Parameterization using Scanning Lidar Observations and Wind Turbine Power Measurements during a Range of Stability Conditions

    Science.gov (United States)

    Lundquist, J. K.

    2015-12-01

    As wind energy deployment increases, questions arise regarding impacts on local climates and how these impacts evolve with the diurnal cycle of the boundary layer. Satellite observations suggest nocturnal increases of surface temperatures, and measurements of turbine wakes document stronger and more persistent reductions of wind speed and increases in turbulence downwind of turbines during stable conditions. Validations of mesoscale parameterizations of these effects have been constrained to idealized conditions defined by neutrally-stratified conditions and/or limited wind directions and wind speeds, or by comparison to idealized large-eddy simulations. Synthesis of conventional meteorological measurements and unconventional measurements can offer unique insights for validating models over a large heterogeneous domain. The CWEX-13 field experiment provides an extensive dataset for such validation at spatial scales on the order of 10 km in a range of atmospheric stability and wind conditions. CWEX-13 took place within a 300 MW wind farm in central Iowa during summer 2013 and featured strong diurnal cycles. The wind turbines are sited irregularly, creating a heterogenous "canopy". Three profiling lidars, numerous surface flux stations, and a scanning lidar sampled wakes from multiple turbines. Further, the wind farm owner/operator has provided access to turbine power production and wind speed measurement data for model validation, providing ~ 200 measurements of proxies that integrate the wind profile over the rotor disk, from 40 m to 120 m above the surface. Building on previous work that identified optimal physics options, grid configurations, and boundary condition data sets by comparison to lidar wind profile measurements, we execute simulations with the WRF Wind Farm Parameterization for a ten-day period featuring moderate winds and strong diurnal cycles. We evaluate simulations with different modeling choices (e.g., vertical resolution, approaches to

  11. IPS activity observed as a precursor of solar induced terrestrial activity. [solar wind density fluctuations

    Science.gov (United States)

    Cronyn, W. M.; Shawhan, S. D.; Rickard, J. J.; Mitchell, D. G.; Roelof, E. C.; Gotwols, B. L.

    1978-01-01

    A radio telescope designed to exploit the interplanetary scintillation (IPS) technique and locate, map, and track solar wind disturbances which result in geomagnetic disturbances, thereby providing a forecast capability, is described. Preliminary results from operation of the telescope include: (1) evidence for a precursor signal in the IPS activity with a 1-2 day lead time with respect to density enhancements which frequently give rise to geomagnetic activity; (2) detection of a spectral broadening signature which also serves as a precursor of geomagnetic activity; (3) out-of-the-ecliptic plasma density enhancements which were not detected by near-Earth, ecliptic plane spacecraft; (4) detection of 12 corotating density enhancements;(5) detection of over 80 sources which give detectable scintillation of which 45 have been used for detailed synoptic analysis and 9 for spectral analysis; and (6) measurement of 0-lag coefficient of 0.56 between density and IPS activity enhancements.

  12. Vertical velocity and turbulence aspects during Mistral events as observed by UHF wind profilers

    Directory of Open Access Journals (Sweden)

    J.-L. Caccia

    2004-11-01

    Full Text Available The general purpose of this paper is to experimentally study mesoscale dynamical aspects of the Mistral in the coastal area located at the exit of the Rhône-valley. The Mistral is a northerly low-level flow blowing in southern France along the Rhône-valley axis, located between the French Alps and the Massif Central, towards the Mediterranean Sea. The experimental data are obtained by UHF wind profilers deployed during two major field campaigns, MAP (Mesoscale Alpine Program in autumn 1999, and ESCOMPTE (Expérience sur Site pour COntraindre les Modèles de Pollution atmosphériques et de Transports d'Emission in summer 2001.

    Thanks to the use of the time evolution of the vertical profile of the horizontal wind vector, recent works have shown that the dynamics of the Mistral is highly dependent on the season because of the occurrence of specific synoptic patterns. In addition, during summer, thermal forcing leads to a combination of sea breeze with Mistral and weaker Mistral due to the enhanced friction while, during autumn, absence of convective turbulence leads to substantial acceleration as low-level jets are generated in the stably stratified planetary boundary layer. At the exit of the Rhône valley, the gap flow dynamics dominates, whereas at the lee of the Alps, the dynamics is driven by the relative contribution of "flow around" and "flow over" mechanisms, upstream of the Alps. This paper analyses vertical velocity and turbulence, i.e. turbulent dissipation rate, with data obtained by the same UHF wind profilers during the same Mistral events.

    In autumn, the motions are found to be globally and significantly subsident, which is coherent for a dry, cold and stable flow approaching the sea, and the turbulence is found to be of pure dynamical origin (wind shears and mountain/lee wave breaking, which is coherent with non-convective situations.

    Imprint of the Sun’s Evolving Polar Winds on IBEX Energetic Neutral Atom All-sky Observations of the Heliosphere

    Energy Technology Data Exchange (ETDEWEB)

    Zirnstein, E. J.; McComas, D. J. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Dayeh, M. A. [Southwest Research Institute, San Antonio, TX 78228 (United States); Sokół, J. M., E-mail: ejz@princeton.edu [Space Research Centre of the Polish Academy of Sciences, 00-716 Warsaw (Poland)

    2017-09-01

    With 7 years of Interstellar Boundary Explorer ( IBEX ) measurements of energetic neutral atoms (ENAs), IBEX has shown a clear correlation between dynamic changes in the solar wind and the heliosphere’s response in the formation of ENAs. In this paper, we investigate temporal variations in the latitudinal-dependent ENA spectrum from IBEX and their relationship to the solar wind speed observed at 1 au. We find that the variation in latitude of the transition in ENA spectral indices between low (≲1.8) and high (≳1.8) values, as well as the distribution of ENA spectral indices at high and low latitudes, correlates well with the evolution of the fast and slow solar wind latitudinal structure observed near 1 au. This correlation includes a delay due to the time it takes the solar wind to propagate to the termination shock and into the inner heliosheath, and for ENAs to be generated via charge-exchange and travel back toward 1 au. Moreover, we observe a temporal asymmetry in the steepening of the ENA spectrum in the northern and southern hemispheres, consistent with asymmetries observed in the solar wind and polar coronal holes. While this asymmetry is observed near the upwind direction of the heliosphere, it is not yet observed in the tail direction, suggesting a longer line-of-sight integration distance or different processing of the solar wind plasma downstream of the termination shock.

  13. Imprint of the Sun’s Evolving Polar Winds on IBEX Energetic Neutral Atom All-sky Observations of the Heliosphere

    Science.gov (United States)

    Zirnstein, E. J.; Dayeh, M. A.; McComas, D. J.; Sokół, J. M.

    2017-09-01

    With 7 years of Interstellar Boundary Explorer (IBEX) measurements of energetic neutral atoms (ENAs), IBEX has shown a clear correlation between dynamic changes in the solar wind and the heliosphere’s response in the formation of ENAs. In this paper, we investigate temporal variations in the latitudinal-dependent ENA spectrum from IBEX and their relationship to the solar wind speed observed at 1 au. We find that the variation in latitude of the transition in ENA spectral indices between low (≲1.8) and high (≳1.8) values, as well as the distribution of ENA spectral indices at high and low latitudes, correlates well with the evolution of the fast and slow solar wind latitudinal structure observed near 1 au. This correlation includes a delay due to the time it takes the solar wind to propagate to the termination shock and into the inner heliosheath, and for ENAs to be generated via charge-exchange and travel back toward 1 au. Moreover, we observe a temporal asymmetry in the steepening of the ENA spectrum in the northern and southern hemispheres, consistent with asymmetries observed in the solar wind and polar coronal holes. While this asymmetry is observed near the upwind direction of the heliosphere, it is not yet observed in the tail direction, suggesting a longer line-of-sight integration distance or different processing of the solar wind plasma downstream of the termination shock.

  14. One Year of Doppler Lidar Observations Characterizing Boundary Layer Wind, Turbulence, and Aerosol Structure During the Indianapolis Flux Experiment

    Science.gov (United States)

    Hardesty, R. M.; Brewer, A.; Shepson, P. B.; Cambaliza, M. O. L.; Salmon, O. E.; Heimburger, A. M. F.; Davis, K. J.; Lauvaux, T.; McGowan, L. E.; Miles, N. L.; Richardson, S.; Sarmiento, D. P.; Karion, A.; Sweeney, C.; Iraci, L. T.; Hillyard, P. W.; Podolske, J. R.; Gurney, K. R.; Razlivanov, I. N.; Song, Y.; Turnbull, J. C.; Whetstone, J. R.; Possolo, A.; Prasad, K.

    2014-12-01

    The Indianapolis Flux Experiment (INFLUX) is aimed at improving methods for estimation of greenhouse gas emissions at urban scales. INFLUX observational components include several-times-per-month aircraft measurements of gas concentrations and meteorological parameters, as well as a number of towers observing CO2, CH4, and CO and a single continuously operating Doppler lidar to estimate wind, turbulence and aerosol structure in the boundary layer. The observations are used to develop top-down emissions estimates from the aircraft measurements and as input to inversion models. The Doppler lidar provides information on boundary layer structure for both the aircraft and inversion studies. A commercial Doppler lidar characterized by low pulse energy and high pulse repetition rate has operated for well over a year at a site NE of downtown Indianapolis. The lidar produces profiles of horizontal wind speed, vertical velocity variance, and aerosol structure two to three times per hour. These data are then used to investigate boundary layer mixing and thickness and horizontal transport as inputs for the flux calculations. During its one year deployment the lidar generally operated reliably with few outages. Comparisons with aircraft spirals over the site and with the NOAA High Resolution research Doppler lidar deployed to Indianapolis for one month during May, 2014, were used to assess the performance of the INFLUX lidar. Measurements agreed quite well when aerosol loading was sufficient for lidar observations throughout the boundary layer. However, low aerosol loading during some periods limited the range of the lidar and precluded characterization of the full boundary layer. We present an overall assessment of the commercial Doppler lidar for providing the needed information on boundary layer structure for emission estimations, and show variability of the boundary layer observations over diurnal, seasonal, and annual cycles. Recommendations on system design changes to

  15. Studies of Pulsar Wind Nebula in the Supernova Remnant IC443: Preliminary Observations from the Chandra Data

    Science.gov (United States)

    Ariyibi, E. A.

    2009-10-01

    Preliminary observations of the Chandra data were made in order to study the Pulsar Wind Nebula in the Supernova Remnant IC443. The Chandra X-ray observatory short observation on IC443 was centred on 13 chip ACIS. The CIAO analytical programme was used for the data analysis. The data were separated into point source, with an energy range of 2.1 to 10.0 keV, and diffuse source with energy less than 2.1 Kev. The resulting spectra were fitted to a power law. The observed density numbers and the normalised counts of both the point source and the diffuse source were used to describe the X-ray source. Afin d'étudier la "Pulsar wind Nebula" dans le reste de la Supernova IC 443, nous avons mené une exploitation préliminaire des observations provenant du satellite spatiale Chandra. L'observation brêve de IC 443, par Chandra fut centrée sur les composantes du spectromètre identifiées par la séquence 13. Le programme informatique CIAO fut utilisé pour l'analyse des données. Les données furent groupées en sources ponctuelles, chacune ayant des énergies allant de 2.1 a 10.0 kev ; et en sources diffuses chacune avec des énergies de moins de 2.1 kev. Les spectres obtenus furent interpolés à l'aide de fonction puissance. La densité de flux ainsi que le décompte des particules induites au détecteur par le rayonnement provenant des sources ponctuelles et diffuses furent utilisés pour décrire la source de rayon-X.

  16. STEREO and Wind Observations of Intense Cyclotron Harmonic Waves at the Earth's Bow Shock and Inside the Magnetosheath

    Science.gov (United States)

    Breneman, A. W.; Cattell, C.

    2013-01-01

    We present the first observations of electron cyclotron harmonic waves at the Earth's bow shock from STEREO and Wind burst waveform captures. These waves are observed at magnetic field gradients at a variety of shock geometries ranging from quasi-parallel to nearly perpendicular along with whistler mode waves, ion acoustic waves, and electrostatic solitary waves. Large amplitude cyclotron harmonic waveforms are also observed in the magnetosheath in association with magnetic field gradients convected past the bow shock. Amplitudes of the cyclotron harmonic waves range from a few tens to more than 500 millivolts/meter peak-peak. A comparison between the short (15 meters) and long (100 meters) Wind spin plane antennas shows a similar response at low harmonics and a stronger response on the short antenna at higher harmonics. This indicates that wavelengths are not significantly larger than 100 meters, consistent with the electron cyclotron radius. Waveforms are broadband and polarizations are distinctively comma-shaped with significant power both perpendicular and parallel to the magnetic field. Harmonics tend to be more prominent in the perpendicular directions. These observations indicate that the waves consist of a combination of perpendicular Bernstein waves and field-aligned waves without harmonics. A likely source is the electron cyclotron drift instability which is a coupling between Bernstein and ion acoustic waves. These waves are the most common type of high-frequency wave seen by STEREO during bow shock crossings and magnetosheath traversals and our observations suggest that they are an important component of the high-frequency turbulent spectrum in these regions.

  17. A comparison of mixing depths observed by ground-based wind profilers and an airborne lidar

    Energy Technology Data Exchange (ETDEWEB)

    White, A.B.; Senff, C. [Univ. of Colorado/NOAA Environmental Technology Lab., Cooperative Inst. for Research in Environmental Sciences, Boulder, CO (United States); Banta, R.M. [NOAA Environmental Technology Lab., Boulder, CO (United States)

    1997-10-01

    The mixing depth is one of the most important parameters in air pollution studies because it determines the vertical extent of the `box` in which pollutants are mixed and dispersed. During the 1995 Southern Oxidants Study (SOS95), scientists from the National Oceanic and Atmospheric Administration Environmental Technology Laboratory (NOAA/ETL) deployed four 915-MHz boundary-layer radar/wind profilers (hereafter radars) in and around the Nashville, Tennessee metropolitan area. Scientists from NOAA/ETL also operated an ultraviolet differential absorption lidar (DIAL) onboard a CASA-212 aircraft. Profiles from radar and DIAL can be used to derive estimates of the mixing depth. The methods used for both instruments are similar in that they depend on information derived from the backscattered power. However, different scattering mechanisms for the radar and DIAL mean that different tracers of mixing depth are measured. In this paper we compare the mixing depth estimates obtained from the radar and DIAL and discuss the similarities and differences that occur. (au)

  18. Current observations from a looking down vertical V-ADCP: interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy

    Directory of Open Access Journals (Sweden)

    Laura Cutroneo

    2017-04-01

    Full Text Available In the context of the environmental monitoring of the Concordia wreck removal project, measurements of currents, winds and sea level height were made along the eastern coast of the Giglio Island, Tyrrhenian Sea (Italy, during 2012–2013. The aim of the study was to investigate the effect of atmospheric forcing and periodic sea-level changes on the coastal currents. Normalised Cross-Correlation Function analysis allowed us to correlate these observations. A marked inter-seasonal variability was found in both current and local wind velocity observations but a significant level of correlation between the data was only found during strong wind events. Current and wind directions appeared to be uncorrelated and current measurements showed a predominant NW–SE direction, presumably linked to the shape and orientation of Giglio Island itself. During strong winds from the SSE, current flow was towards the NNW but it suddenly switched from the NNW to the SE at the end of wind events. The results show that, at Giglio Island, currents are principally dominated by the general cyclonic Tyrrhenian circulation, and, secondly, by strong wind events. The sea level had no effects on the current regime.

  19. ModObs: Atmospheric modelling for wind energy, climate and environment applications : exploring added value from new observation technique

    Science.gov (United States)

    Sempreviva, A. M.

    2009-04-01

    The EC FP6 Marie Curie Training Network "ModObs" http://www.modobs.windeng.net addresses the improvement of atmospheric boundary layer (ABL) models to investigate the interplay of processes at different temporal and spatial scales, and to explore the added value from new observation techniques. The overall goal is to bring young scientists to work together with experienced researchers in developing a better interaction amongst scientific communities of modelers and experimentalists, using a comprehensive approach to "Climate Change", "Clean Energy assessment" and "Environmental Policies", issues. This poster describes the work in progress of ten students, funded by the network, under the supervision of a team of scientists within atmospheric physics, engineering and satellite remote sensing and end-users such as companies in the private sector, all with the appropriate expertise to integrate the most advanced research methods and techniques in the following topics. MODELING: GLOBAL-TO-MESO SCALE: Analytical and process oriented numerical models will be used to study the interaction between the atmosphere and the ocean on a regional scale. Initial results indicate an interaction between the intensity of polar lows and the subsurface warm core often present in the Nordic Seas (11). The presence of waves, mainly swell, influence the MABL fluxes and turbulence structure. The regional and global wave effect on the atmosphere will be also studied and quantified (7) MESO-SCALE: Applicability of the planetary boundary layer (PBL) parametrizations in the meso-scale WRF model to marine atmospheric boundary layer (MABL) over the North Sea is investigated. The most suitable existing PBL parametrization will be additionally improved and used for downscaling North Sea past and future climates (2). Application of the meso-scale model (MM5 and WRF) for the wind energy in off-shore and coastal area. Set-up of the meso-scale model, post-processing and verification of the data from

  1. Estimation of Stator Winding Faults in Induction Motors using an Adaptive Observer Scheme

    DEFF Research Database (Denmark)

    Kallesøe, C. S.; Vadstrup, P.; Rasmussen, Henrik

    2004-01-01

    This paper addresses the subject of inter-turn short circuit estimation in the stator of an induction motor. In the paper an adaptive observer scheme is proposed. The proposed observer is capable of simultaneously estimating the speed of the motor, the amount turns involved in the short circuit...... and an expression of the current in the short circuit. Moreover the states of the motor are estimated, meaning that the magnetizing currents are made available even though a fault has happened in the motor. To be able to develop this observer, a model particular suitable for the chosen observer design, is also...... derived. The efficiency of the proposed observer is demonstrated by tests performed on a test setup with a customized designed induction motor. With this motor it is possible to simulate inter-turn short circuit faults....

  2. Estimation of Stator winding faults in induction motors using an adaptive observer scheme

    DEFF Research Database (Denmark)

    Kallesøe, C. S.; Vadstrup, P.; Rasmussen, Henrik

    2004-01-01

    This paper addresses the subject of inter-turn short circuit estimation in the stator of an induction motor. In the paper an adaptive observer scheme is proposed. The proposed observer is capable of simultaneously estimating the speed of the motor, the amount turns involved in the short circuit...... and an expression of the current in the short circuit. Moreover the states of the motor are estimated, meaning that the magnetizing currents are made available even though a fault has happened in the motor. To be able to develop this observer, a model particular suitable for the chosen observer design, is also...... derived. The efficiency of the proposed observer is demonstrated by tests performed on a test setup with a customized designed induction motor. With this motor it is possible to simulate inter-turn short circuit faults....

  3. Observer-based estimation of stator-winding faults in delta-connected induction motors

    DEFF Research Database (Denmark)

    Skovemose Kallesøe, Carsten; Izadi-Zamanabadi, Roozbeh; Vadstrup, Pierre

    2007-01-01

    This paper addresses the subject of interturn short circuit estimation in the stator of a delta-connected induction motor. In this paper, an adaptive observer scheme is proposed. The proposed observer is capable of simultaneously estimating the speed of the motor, the amount turns involved...... in the short circuit, and an expression of the current in the short circuit. Moreover, the currents are made available even though a fault has occurred in the motor. To be able to develop this observer, a model that is particularly suitable for the chosen observer design, is also derived. The effeciency...... of the proposed observer is demonstrated by tests performed on a test setup with a customized designed induction motor. With this motor it is possible to simulate interturn short-circuit faults....

  4. Observer Based Estimation of Stator Winding Faults in Delta-connected Induction Motors, a LMI Approach

    DEFF Research Database (Denmark)

    Kallesøe, Carsten; Vadstrup, Pierre; Rasmussen, Henrik

    2006-01-01

    This paper addresses the subject of inter-turn short circuit estimation in the stator of an induction motor. In the paper an adaptive observer scheme is proposed. The proposed observer is capable of simultaneously estimating the speed of the motor, the amount turns involved in the short circuit...... and an expression of the current in the short circuit. Moreover the states of the motor are estimated, meaning that the magnetizing currents are made available even though a fault has happened in the motor. To be able to develop this observer, a model particular suitable for the chosen observer design, is also...... derived. The efficiency of the proposed observer is demonstrated by tests performed on a test setup with a customized designed induction motor. With this motor it is possible to simulate inter-turn short circuit faults....

  5. Numerical Prediction of Experimentally Observed Behavior of a Scale Model of an Offshore Wind Turbine Supported by a Tension-Leg Platform: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Prowell, I.; Robertson, A.; Jonkman, J.; Stewart, G. M.; Goupee, A. J.

    2013-01-01

    Realizing the critical importance the role physical experimental tests play in understanding the dynamics of floating offshore wind turbines, the DeepCwind consortium conducted a one-fiftieth-scale model test program where several floating wind platforms were subjected to a variety of wind and wave loading condition at the Maritime Research Institute Netherlands wave basin. This paper describes the observed behavior of a tension-leg platform, one of three platforms tested, and the systematic effort to predict the measured response with the FAST simulation tool using a model primarily based on consensus geometric and mass properties of the test specimen.

  6. Observation of horizontal winds in the middle-atmosphere between 30° S and 55° N during the northern winter 2009–2010

    Directory of Open Access Journals (Sweden)

    P. Baron

    2013-06-01

    Full Text Available Although the links between stratospheric dynamics, climate and weather have been demonstrated, direct observations of stratospheric winds are lacking, in particular at altitudes above 30 km. We report observations of winds between 8 and 0.01 hPa (~35–80 km from October 2009 to April 2010 by the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES on the International Space Station. The altitude range covers the region between 35–60 km where previous space-borne wind instruments show a lack of sensitivity. Both zonal and meridional wind components were obtained, though not simultaneously, in the latitude range from 30° S to 55° N and with a single profile precision of 7–9 m s–1 between 8 and 0.6 hPa and better than 20 m s–1 at altitudes above. The vertical resolution is 5–7 km except in the upper part of the retrieval range (10 km at 0.01 hPa. In the region between 1–0.05 hPa, an absolute value of the mean difference –1 is found between SMILES profiles retrieved from different spectroscopic lines and instrumental settings. Good agreement (absolute value of the mean difference of ~2 m s–1 is also found with the European Centre for Medium-Range Weather Forecasts (ECMWF analysis in most of the stratosphere except for the zonal winds over the equator (difference > 5 m s−1. In the mesosphere, SMILES and ECMWF zonal winds exhibit large differences (> 20 m s–1, especially in the tropics. We illustrate our results by showing daily and monthly zonal wind variations, namely the semi-annual oscillation in the tropics and reversals of the flow direction between 50–55° N during sudden stratospheric warmings. The daily comparison with ECMWF winds reveals that in the beginning of February, a significantly stronger zonal westward flow is measured in the tropics at 2 hPa compared to the flow computed in the analysis (difference of ~20 m s–1. The results show that the comparison between SMILES and ECMWF winds is not only

  7. First wind shear observation in PMSE with the tristatic EISCAT VHF radar

    OpenAIRE

    Mann, Ingrid; Häggström, I.; Tjulin, A; Rostami, S; Anyairo, CC; Dalin, P

    2016-01-01

    (c) American Geophysical Union, reprinted with permission. Article also available at source: https://doi.org/10.1002/2016JA023080 The Polar Summer Mesosphere has the lowest temperatures that occur in the entire Earth system. Water ice particles below the optically observable size range participate there in the formation of strong radar echoes (Polar Mesospheric Summer Echoes, PMSE). To study PMSE we carried out observations with the European Incoherent Scatter (EISCAT) VHF and EIS...

  8. The effect of wind turbine noise on sleep and quality of life: A systematic review and meta-analysis of observational studies.

    Science.gov (United States)

    Onakpoya, Igho J; O'Sullivan, Jack; Thompson, Matthew J; Heneghan, Carl J

    2015-09-01

    Noise generated by wind turbines has been reported to affect sleep and quality of life (QOL), but the relationship is unclear. Our objective was to explore the association between wind turbine noise, sleep disturbance and quality of life, using data from published observational studies. We searched Medline, Embase, Global Health and Google Scholar databases. No language restrictions were imposed. Hand searches of bibliography of retrieved full texts were also conducted. The reporting quality of included studies was assessed using the STROBE guidelines. Two reviewers independently determined the eligibility of studies, assessed the quality of included studies, and extracted the data. We included eight studies with a total of 2433 participants. All studies were cross-sectional, and the overall reporting quality was moderate. Meta-analysis of six studies (n=2364) revealed that the odds of being annoyed is significantly increased by wind turbine noise (OR: 4.08; 95% CI: 2.37 to 7.04; p<0.00001). The odds of sleep disturbance was also significantly increased with greater exposure to wind turbine noise (OR: 2.94; 95% CI: 1.98 to 4.37; p<0.00001). Four studies reported that wind turbine noise significantly interfered with QOL. Further, visual perception of wind turbine generators was associated with greater frequency of reported negative health effects. In conclusion, there is some evidence that exposure to wind turbine noise is associated with increased odds of annoyance and sleep problems. Individual attitudes could influence the type of response to noise from wind turbines. Experimental and observational studies investigating the relationship between wind turbine noise and health are warranted. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Determining volcanic SO2 plume heights in satellite observations using meteorological wind fields

    Science.gov (United States)

    Keicher, Viktoria; Hörmann, Christoph; Sihler, Holger; Platt, Ulrich; Wagner, Thomas

    2016-04-01

    Satellite observations nowadays provide the global monitoring of volcanic plumes via sulphur dioxide (SO2) that is injected into the Earth's atmosphere. In turn, SO2 may lead to the formation of sulphate aerosols that can influence climate via direct and indirect radiative effects. The retrieval of SO2 requires an accurate plume height estimate in order to constrain total amounts for such events. One of the main difficulties for the retrieval is the typically unknown atmospheric profile resulting from unknown initial conditions (individual explosions over an extended time period leading to different gas layer altitudes and influencing the atmospheric transport pattern). In recent years, satellite observations helped to improve global SO2 estimates, but still large uncertainties exist. Passive satellite remote sensing using measurements in the UV/vis spectral range for example offers the opportunity to observe the location of a plume in two dimensions, but information about the corresponding height is sparse. Furthermore, information about these plume profiles is not only interesting in itself (e.g. to assess the radiative effect of volcanic plumes). It is also important for the quantitative interpretation of satellite observations. Here, we present first results for a newly developed approach using the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) in combination with data for different volcanic SO2 plumes as observed by the second generation Global Ozone Monitoring Instrument (GOME-2). The main plume information that can be retrieved by the satellite (i.e. plume location and observation time) are used as initial input parameters in order to estimate the plume's profile at the time of the measurements. For selected case studies we use these trajectories to further estimate values the eruption time and height. The correspondingly modelled values can also be used to verify the results when they are compared to direct local observations and

  10. Direct observations of the formation of the solar wind halo from the strahl

    Energy Technology Data Exchange (ETDEWEB)

    Gurgiolo, C. [Bitterroot Basic Research, Hamilton, MT (United States); Goldstein, M.L.; Vinas, A.F. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). Geospace Science Lab.; Fazakerley, A.N. [Univ. College London, Holmbury St. Mary Dorking, Surrey (United Kingdom). Mullard Space Science Lab.

    2012-07-01

    Observations of a continual erosion of the strahl and build up of the halo with distance from the sun suggests that, at least in part, the halo may be formed as a result of scattering of the strahl. This hypothesis is supported in this paper by observation of intense scattering of strahl electrons, which gives rise to a proto-halo electron population. This population eventually merges into, or becomes the halo. The fact that observations of intense scattering of the strahl are not common implies that the formation of the halo may not be a continuous process, but one that occurs, in part, in bursts in regions where the conditions responsible for the scattering are optimum. (orig.)

  11. Ion Events Observed by Wind far Upstream From the Bow Shock and by Geotail / Imp-8 Near the Bow Shock and Within the Plasma Sheet

    Science.gov (United States)

    Anagnostopoulos, G.; Efthymiadis, D.; Sarris, E. T.; Krimigis, S. M.

    2002-12-01

    Mason et al. (1996) reported characteristics of short duration energetic (>~30 keV/neucleon) heavy ion enhancements observed by the WIND spacecraft at large distances upstream from the bow shock during two periods of high speed streams (Jan. 20, 1995 - Feb. 19, 1995) and Desai et al (2000) extended their study and presented results from a statistical analysis of upstream events rich in CNO species as observed by the WIND spacecraft between 1994 day 325 to 1999 day 92. Desai et al. suggested that some ion characteristics (as for instance, the fact that the majority of the events were observed in the dawn-noon sector, the solar-wind-like ion composition and the heavy ion dominance of the total energy ion spectrum above ~0.5 MeV) appear to pose severe problems for the leakage model, while other characteristics appear to pose serious challenges for the Fermi acceleration model. In this paper we compare the statistical results of Desai et al. with the results from previous statistical and case studies and we show that the Wind observations are in general consistent with the leakage model. Furthermore, we examine simultaneous multispacecraft observations during time periods of some typical events presented by the authors (Mason et al., 1996; Desai et al., 2000) and we compare them with predictions from the leakage and bow shock acceleration models. In particular: (a) we present observations by WIND far upstream from the bow shock and by Geotail and IMP-8 within the magnetosphere and we infer that particle acceleration within the plasma sheet and subsequent leakage to the upstream region are responsible for the generation of these upstream ion events, and (b) we compare the upstream WIND observations with observations obtained by Geotail and IMP-8 near the bow shock, and we infer that the near bow shock observations do not fit with major predictions of Fermi acceleration models.

  12. Initial daytime and nighttime SOFDI observations of thermospheric winds from Fabry-Perot Doppler shift measurements of the 630-nm OI line-shape profile

    Directory of Open Access Journals (Sweden)

    A. J. Gerrard

    2011-09-01

    Full Text Available In this paper we present both night and day thermospheric wind observations made with the Second-generation, Optimized, Fabry-Perot Doppler Imager (SOFDI, a novel triple-etalon Fabry-Perot interferometer (FPI designed to make 24-h measurements of thermospheric winds from OI 630-nm emission. These results were obtained from the northeastern United States and from under the magnetic equator at Huancayo, Peru and demonstrate the current instrument capability for measurements of Doppler shifts for either night or day. We found the uncertainties in the measurements agree with expected values based upon forward modeling calculations; nighttime wind components having an uncertainty of ~20-m s−1 at 30-min resolution and daytime wind components having an uncertainty of ~70-m s−1 at 20-min resolution. The nighttime uncertainties are typically larger than those seen with traditional single-etalon FPIs, which occur at the cost of being able to achieve daytime measurements. The thermospheric wind measurements from Huancayo replicate recently reported CHAMP zonal winds and are in disagreement with current empirical wind climatologies. In addition, we discuss the incorporation of how multiple point heads in the SOFDI instrument will allow for unique studies of gravity wave activity in future measurements.

  13. Wake meandering and its relationship with the incoming wind characteristics: a statistical approach applied to long-term on-field observations

    Science.gov (United States)

    Torres Garcia, E.; Aubrun, S.; Boquet, M.; Royer, P.; Coupiac, O.; Girard, N.

    2017-05-01

    In several papers, the importance of the atmospheric flow in the wake development of wind turbines (WT) has been pointed out, making it clear that it is necessary to have long-term on-field observations for an appropriate description of the wake development, its structure and dynamics. This work presents a statistical approach to wake meandering, y w , and the relationship that this behavior has with the incoming wind conditions and neighboring wakes. The work was developed in the framework of the French project SMARTEOLE. The study is based on a 7-month measurement campaign in which a pulsed scanning LiDAR system was used. The ground based LiDAR, measures the flow field in a segment such that the wake of two wind turbines can be captured quasi-horizontally. The analysis filters the incoming wind conditions according to the thermal stability, wind direction and wind velocity at hub height; therefore, the wakes that are developed in periods with similar wind conditions are expected to be analogous, hence meandering can be tracked and statistically analyzed. A well-defined wake evolution was found and the uncertainty analysis made on the wake meandering uncovered some interesting characteristics, including the number of samples required to reach a statistical uncertainty on the mean wake position between 2 × 10-2 D and 8 × 10-2 D for a confidence interval of 95%.

  14. Microphysical, Macrophysical and Radiative Signatures of Volcanic Aerosols in Trade Wind Cumulus Observed by the A-Train

    Science.gov (United States)

    Yuan, T.; Remer, L. A.; Yu, H.

    2011-01-01

    Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-tem1 degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The "total shortwave aerosol forcin", resulting from direct and indirect forcings including both cloud albedo and cloud amount. is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

  15. Microphysical, macrophysical and radiative signatures of volcanic aerosols in trade wind cumulus observed by the A-Train

    Directory of Open Access Journals (Sweden)

    T. Yuan

    2011-07-01

    Full Text Available Increased aerosol concentrations can raise planetary albedo not only by reflecting sunlight and increasing cloud albedo, but also by changing cloud amount. However, detecting aerosol effect on cloud amount has been elusive to both observations and modeling due to potential buffering mechanisms and convolution of meteorology. Here through a natural experiment provided by long-term degassing of a low-lying volcano and use of A-Train satellite observations, we show modifications of trade cumulus cloud fields including decreased droplet size, decreased precipitation efficiency and increased cloud amount are associated with volcanic aerosols. In addition we find significantly higher cloud tops for polluted clouds. We demonstrate that the observed microphysical and macrophysical changes cannot be explained by synoptic meteorology or the orographic effect of the Hawaiian Islands. The "total shortwave aerosol forcin", resulting from direct and indirect forcings including both cloud albedo and cloud amount, is almost an order of magnitude higher than aerosol direct forcing alone. Furthermore, the precipitation reduction associated with enhanced aerosol leads to large changes in the energetics of air-sea exchange and trade wind boundary layer. Our results represent the first observational evidence of large-scale increase of cloud amount due to aerosols in a trade cumulus regime, which can be used to constrain the representation of aerosol-cloud interactions in climate models. The findings also have implications for volcano-climate interactions and climate mitigation research.

  16. A Study on Sunward Propagating Alfvénic Fluctuations With a Power Law Spectrum Observed by the Wind Spacecraft

    Science.gov (United States)

    Wu, Honghong; Wang, Xin; Tu, Chuanyi; Wang, Linghua; He, Jiansen; Tian, Hui

    2017-10-01

    Sunward propagating Alfvénic fluctuations with a power law spectrum (SAFP) have been recently observed in the upstream region of the Earth's bow shock. However, some physical properties of these fluctuations such as anisotropy remain unclear. Here we develop a new method for identifying SAFPs, and present for the first time the anisotropy of SAFPs power and spectral index. In this method, the propagation direction determination of SAFPs does not rely on a radial magnetic geometry but the pitch angle distribution of strahl electron outflow. Therefore, the SAFPs with any value of θRB (angle between the global mean magnetic field and the Sun-to-Earth radial direction) can be identified, so that enables the study of the spectral anisotropy. We find 508 SAFPs using the Wind spacecraft measurements from 1995 to 2014. We show that the SAFP has an averaged spectral index of -1.77 ± 0.28 and the index changes continuously from -2.18 ± 0.21 when θRB=0°-10° to -1.71 ± 0.03 when θRB=80°-90°. These SAFPs are observed more frequently in the slow solar wind especially at solar minimum. We also select antisunward propagating Alfvénic fluctuations with a power law spectrum using the same method for comparison. The results indicate that the power spectrum of SAFP is steeper, and the spectral intensity as well as the power anisotropy of SAFP is weaker. These new findings may provide information on the generation of turbulence in the upstream region.

  17. A comparison study between observations and simulation results of Barghouthi model for O+ and H+ outflows in the polar wind

    Directory of Open Access Journals (Sweden)

    I. A. Barghouthi

    2011-11-01

    Full Text Available To advance our understanding of the effect of wave-particle interactions on ion outflows in the polar wind region and the resulting ion heating and escape from low altitudes to higher altitudes, we carried out a comparison between polar wind simulations obtained using Barghouthi model with corresponding observations obtained from different satellites. The Barghouthi model describes O+ and H+ outflows in the polar wind region in the range 1.7 RE to 13.7 RE, including the effects of gravity, polarization electrostatic field, diverging geomagnetic field lines, and wave-particle interactions. Wave-particle interactions were included into the model by using a particle diffusion equation, which depends on diffusion coefficients determined from estimates of the typical electric field spectral density at relevant altitudes and frequencies. We provide a formula for the velocity diffusion coefficient that depends on altitude and velocity, in which the velocity part depends on the perpendicular wavelength of the electromagnetic turbulence λ⊥. Because of the shortage of information about λ⊥, it was included into the model as a parameter. We produce different simulations (i.e. ion velocity distributions, ions density, ion drift velocity, ion parallel and perpendicular temperatures for O+ and H+ ions, and for different λ⊥. We discuss the simulations in terms of wave-particle interactions, perpendicular adiabatic cooling, parallel adiabatic cooling, mirror force, and ion potential energy. The main findings of the simulations are as follows: (1 O+ ions are highly energized at all altitudes in the simulation tube due to wave-particle interactions that heat the ions in the perpendicular direction, and part of this gained energy transfer to the parallel direction by mirror force, resulting in accelerating O+ ions along geomagnetic field lines from lower altitudes to higher altitudes. (2 The effect of wave-particle interactions is negligible for H

  18. Partial Variance of Increments Method in Solar Wind Observations and Plasma Simulations

    Science.gov (United States)

    Greco, A.; Matthaeus, W. H.; Perri, S.; Osman, K. T.; Servidio, S.; Wan, M.; Dmitruk, P.

    2018-02-01

    The method called "PVI" (Partial Variance of Increments) has been increasingly used in analysis of spacecraft and numerical simulation data since its inception in 2008. The purpose of the method is to study the kinematics and formation of coherent structures in space plasmas, a topic that has gained considerable attention, leading the development of identification methods, observations, and associated theoretical research based on numerical simulations. This review paper will summarize key features of the method and provide a synopsis of the main results obtained by various groups using the method. This will enable new users or those considering methods of this type to find details and background collected in one place.

  19. Solar Wind Halo Formation by the Scattering of the Strahl via Direct Cluster/PEACE Observations of the 3D Velocity Distribution Function

    Science.gov (United States)

    Figueroa-Vinas, Adolfo; Gurgiolo, Chris A.; Nieves-Chinchilla, Teresa; Goldstein, Melvyn L.

    2010-01-01

    It has been suggested by a number of authors that the solar wind electron halo can be formed by the scattering of the strahl. On frequent occasions we have observed in electron angular skymaps (Phi/Theta-plots) of the electron 3D velocity distribution functions) a bursty-filament of particles connecting the strahl to the solar wind core-halo. These are seen over a very limited energy range. When the magnetic field is well off the nominal solar wind flow direction such filaments are inconsistent with any local forces and are probably the result of strong scattering. Furthermore, observations indicates that the strahl component is frequently and significantly anisotropic (Tper/Tpal approx.2). This provides a possible free energy source for the excitation of whistler waves as a possible scattering mechanism. The empirical observational evidence between the halo and the strahl suggests that the strahl population may be, at least in part, the source of the halo component.

  20. Deep Chandra Observations of HCG 16. I. Active Nuclei, Star Formation, and Galactic Winds

    Science.gov (United States)

    O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.; Giacintucci, S.; Trevisan, M.; David, L. P.; Ponman, T. J.; Mamon, G. A.; Raychaudhury, S.

    2014-10-01

    We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ~400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ~0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

  1. Deep Chandra observations of HCG 16. I. Active nuclei, star formation, and galactic winds

    Energy Technology Data Exchange (ETDEWEB)

    O' Sullivan, E.; Zezas, A.; Vrtilek, J. M.; David, L. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Giacintucci, S. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Trevisan, M. [Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas 1758, 12227-010, São José dos Campos (Brazil); Ponman, T. J.; Raychaudhury, S. [School of Physics and Astronomy, University of Birmingham, Birmingham, B15 2TT (United Kingdom); Mamon, G. A., E-mail: eosullivan@cfa.harvard.edu [Institut d' Astrophysique de Paris (UMR 7095 CNRS and UMPC), 98 bis Bd Arago, F-75014 Paris (France)

    2014-10-01

    We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ∼400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ∼0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

  2. Transient and local weakening of surface winds observed above the Kuroshio front in the winter East China Sea

    National Research Council Canada - National Science Library

    Kasamo, Kenki; Isobe, Atsuhiko; Minobe, Shoshiro; Manda, Atsuyoshi; Nakamura, Hirohiko; Ogata, Koto; Nishikawa, Hatsumi; Tachibana, Yoshihiro; Kako, Shin'ichiro

    2014-01-01

    To confirm whether surface winds strengthen above warm waters around oceanic fronts using in situ data, a field measurement was conducted using both expendable bathythermographs and Global Positioning...

  3. The VELA-X-Pulsar Wind Nebula Revisited with Four Years of Fermi Large Area Telescope Observations

    Science.gov (United States)

    Grondin, M. -H.; Romani, R. W.; Lemoine-Goumard, M.; Guillemot, L.; Harding, Alice K.; Reposeur, T.

    2013-01-01

    The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2deg × 3deg south of the pulsar and observed in the radio, X-ray, and very high energy ?-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

  4. Optimal Tuning of Multivariable Disturbance-Observer-Based Control for Flicker Mitigation Using Individual Pitch Control of Wind Turbine

    DEFF Research Database (Denmark)

    Raja, Muhammad Imran; Hussain, Dil muhammed Akbar; Soltani, Mohsen

    2017-01-01

    , (p is the rotor rotational frequency) for three-bladed wind turbine. Novel DOBC with individual pitch control (IPC) to mitigate the flickers is presented and linear state-space model of wind turbine with tower dynamics is developed. The proposed controller is tuned using optimal control theory...

  5. Hub Height Ocean Winds over the North Sea Observed by the NORSEWInD Lidar Array: Measuring Techniques, Quality Control and Data Management

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Stein, Detlef; Courtney, Michael

    2013-01-01

    mast situated in flat terrain. The so-called “NORSEWInD standard” for comparing lidar and mast wind data includes the criteria that the slope of the linear regression should lie within 0.98 and 1.01 and the linear correlation coefficient higher than 0.98 for the wind speed range 4–16 m∙s−1. Five lidars...... performed excellently, two slightly failed the first criterion and one failed both. The lidars were operated offshore from six months to more than two years and observed in total 107 months of 10-min mean wind profile observations. Four lidars were re-evaluated post deployment with excellent results...

  6. No evidence that solar wind turbulence can be described by the critical balance theory

    Science.gov (United States)

    Wang, X.; Tu, C. Y.; Marsch, E.

    2015-12-01

    The critical balance theory (GS, Goldreich and Sridhar, 1995) in MHD turbulence seems now to be well accepted in the turbulence community. During recent years, quite a few papers claimed to have provided evidence in support of this theory by solar wind turbulence observations. Here we present new data that result in a different conclusion, namely that the previous observations cannot be considered as evidence for the GS theory. It is based on the critical balance assumption that the parallel Alfven wave propagation time equals the perpendicular cascade time, k⊥v⊥=k//VA. Assuming that the cascading energy flux does not change with scale, a spectral index of -2 is obtained for the parallel power spectrum P(k//). To check this theoretical prediction, small sampling angle (θRB) with the mean magnetic field averaged at the local time and the local scale is used for selecting the local power spectral densities (PSDs). We recovered that the so averaged PSDs at different scales have a nearly -2 slope. However, using 30 days of Ulysses data we discovered that the critical balance assumption was invalid in the corresponding data analysis. The values of δB/B0 corresponding to the selected local PSDs are all found to be much smaller than the required value of tan(θRB). Most of the observations with a small sampling angle may be considered to be rather more perpendicular from the theoretical point of view. We also found that the spectral index of the selected PSDs depends on the selection criterion. If one guarantees constantly small sampling angles in a local time period, the slope of the selected PSD changes to -1.7. Thus our conclusion is that no evidence exists that solar wind turbulence can be described by the GS theory. What is the true origin of the spectral anisotropy of the solar wind turbulence remains an important open question.

  7. Hurricane Imaging Radiometer (HIRAD) Observations of Brightness Temperatures and Ocean Surface Wind Speed and Rain Rate During NASA's GRIP and HS3 Campaigns

    Science.gov (United States)

    Miller, Timothy L.; James, M. W.; Roberts, J. B.; Jones, W. L.; Biswas, S.; Ruf, C. S.; Uhlhorn, E. W.; Atlas, R.; Black, P.; Albers, C.

    2012-01-01

    HIRAD flew on high-altitude aircraft over Earl and Karl during NASA s GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010, and plans to fly over Atlantic tropical cyclones in September of 2012 as part of the Hurricane and Severe Storm Sentinel (HS3) mission. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain spatial resolution of approximately 2 km, out to roughly 30 km each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface wind speed and rain rate can be retrieved. The physical retrieval technique has been used for many years by precursor instruments, including the Stepped Frequency Microwave Radiometer (SFMR), which has been flying on the NOAA and USAF hurricane reconnaissance aircraft for several years to obtain observations within a single footprint at nadir angle. Results from the flights during the GRIP and HS3 campaigns will be shown, including images of brightness temperatures, wind speed, and rain rate. Comparisons will be made with observations from other instruments on the campaigns, for which HIRAD observations are either directly comparable or are complementary. Features such as storm eye and eye-wall, location of storm wind and rain maxima, and indications of dynamical features such as the merging of a weaker outer wind/rain maximum with the main vortex may be seen in the data. Potential impacts on operational ocean surface wind analyses and on numerical weather forecasts will also be discussed.

  8. Velocity fluctuations in polar solar wind: a comparison between different solar cycles

    Directory of Open Access Journals (Sweden)

    B. Bavassano

    2009-02-01

    Full Text Available The polar solar wind is a fast, tenuous and steady flow that, with the exception of a relatively short phase around the Sun's activity maximum, fills the high-latitude heliosphere. The polar wind properties have been extensively investigated by Ulysses, the first spacecraft able to perform in-situ measurements in the high-latitude heliosphere. The out-of-ecliptic phases of Ulysses cover about seventeen years. This makes possible to study heliospheric properties at high latitudes in different solar cycles. In the present investigation we focus on hourly- to daily-scale fluctuations of the polar wind velocity. Though the polar wind is a quite uniform flow, fluctuations in its velocity do not appear negligible. A simple way to characterize wind velocity variations is that of performing a multi-scale statistical analysis of the wind velocity differences. Our analysis is based on the computation of velocity differences at different time lags and the evaluation of statistical quantities (mean, standard deviation, skewness, and kurtosis for the different ensembles. The results clearly show that, though differences exist in the three-dimensional structure of the heliosphere between the investigated solar cycles, the velocity fluctuations in the core of polar coronal holes exhibit essentially unchanged statistical properties.

  9. Combining radar and direct observation to estimate pelican collision risk at a proposed wind farm on the Cape west coast, South Africa.

    Science.gov (United States)

    Jenkins, Andrew R; Reid, Tim; du Plessis, Johan; Colyn, Robin; Benn, Grant; Millikin, Rhonda

    2018-01-01

    Pre-construction assessments of bird collision risk at proposed wind farms are often confounded by insufficient or poor quality data describing avian flight paths through the development area. These limitations can compromise the practical value of wind farm impact studies. We used radar- and observer-based methods to quantify great white pelican flights in the vicinity of a planned wind farm on the Cape west coast, South Africa, and modelled turbine collision risk under various scenarios. Model outputs were combined with pre-existing demographic data to evaluate the possible influence of the wind farm on the pelican population, and to examine impact mitigation options. We recorded high volumes of great white pelican movement through the wind farm area, coincident with the breeding cycle of the nearby colony and associated with flights to feeding areas located about 50 km away. Pelicans were exposed to collision risk at a mean rate of 2.02 High Risk flights.h-1. Risk was confined to daylight hours, highest during the middle of the day and in conditions of strong north-westerly winds, and 82% of High Risk flights were focused on only five of the proposed 35 turbine placements. Predicted mean mortality rates (22 fatalities.yr-1, 95% Cl, 16-29, with average bird and blade speeds and 95% avoidance rates) were not sustainable, resulting in a negative population growth rate (λ = 0.991). Models suggested that removal of the five highest risk turbines from the project, or institution of a curtailment regimen that shuts down at least these turbines at peak traffic times, could theoretically reduce impacts to manageable levels. However, in spite of the large quantities of high quality data used in our analyses, our collision risk model remains compromised by untested assumptions about pelican avoidance rates and uncertainties about the existing dynamics of the pelican population, and our findings are probably not reliable enough to ensure sustainable development.

  10. Particle observations and propagation in the Three-Dimensional Heliosphere

    Science.gov (United States)

    Malandraki, O.E.; Marsden, R.G.; Lario, D.; Sanderson, T.R.; Tranquille, C.; Forsyth, R.J.; Elliott, H.A.; Lanzerotti, L.J.; Geranios, A.; Sarris, E.T.; Heber, B.; Mueller-Mellin, R.

    Ulysses, the first spacecraft ever to fly over the poles of the Sun, plays a central role in the Heliospheric Network, the international fleet of spacecraft to explore the Sun and Heliosphere. In November 2006, Ulysses, began its passage over the Sun’s south pole for the third time. Although like during the first polar passes in 1994/1995 the Sun is again close to its activity minimum, an unexpected rise of solar activity occurred in December 2006. Active Region 0930 produced a series of major solar flares with the strongest one (X9.0) recorded on December 5 after it rotated into view on the solar east limb. We will present energetic particle observations by Ulysses located at >70 deg south heliolatitude during this period and will discuss their implications for particle propagation to solar polar regions. The observed events will also be compared with previous Ulysses high latitude measurements obtained close to solar maximum. Furthermore, comparisons with data acquired from other spacecraft of the Heliospheric Network near the ecliptic plane will be discussed. (The project is co-funded by the European Social Fund and National Resources (EPEAEK II) PYTHAGORAS II.)

  11. Using CYGNSS to Observe Convectively Driven Near-Surface Winds in Tropical Precipitation Systems During Madden-Julian Oscillation Events

    Science.gov (United States)

    Lang, Timothy J.; Li, Xuanli; Mecikalski, John; Hoover, Kacie; Castillo, Tyler; Chronis, Themis

    2017-01-01

    The Cyclone Global Navigation OKLMA 1411 UTC Satellite System (CYGNSS) is a multi-satellite constellation that launched 15 December 2016. The primary objective of CYGNSS is to use bistatic Global Positioning System (GPS) reflectometry to accurately measure near-surface wind speeds within the heavily raining inner core of tropical cyclones. CYGNSS also features rapid revisit times over a given region in the tropics - ranging from several minutes to a few hours, depending on the constellation geometry at that time. Despite the focus on tropical cyclones, the ability of CYGNSS to provide rapid updates of winds, unbiased by the presence of precipitation, has many other potential applications related to general tropical convection.

  12. Meteor radar measurements of MLT winds near the equatorial electro jet region over Thumba (8.5° N, 77° E: comparison with TIDI observations

    Directory of Open Access Journals (Sweden)

    S. R. John

    2011-07-01

    Full Text Available The All-Sky interferometric meteor (SKYiMET radar (MR derived winds in the vicinity of the equatorial electrojet (EEJ are discussed. As Thumba (8.5° N, 77° E; dip lat. 0.5° N is under the EEJ belt, there has been some debate on the reliability of the meteor radar derived winds near the EEJ height region. In this regard, the composite diurnal variations of zonal wind profiles in the mesosphere-lower thermosphere (MLT region derived from TIMED Doppler Interferometer (TIDI and ground based meteor radar at Thumba are compared. In this study, emphasis is given to verify the meteor radar observations at 98 km height region, especially during the EEJ peaking time (11:00 to 14:00 LT. The composite diurnal cycles of zonal winds over Thumba are constructed during four seasons of the year 2006 using TIDI and meteor radar observations, which showed good agreement especially during the peak EEJ hours, thus assuring the reliability of meteor radar measurements of neutral winds close to the EEJ height region. It is evident from the present study that on seasonal scales, the radar measurements are not biased by the EEJ. The day-time variations of HF radar measured E-region drifts at the EEJ region are also compared with MR measurements to show there are large differences between ionospheric drifts and MR measurements. The significance of the present study lies in validating the meteor radar technique over Thumba located at magnetic equator by comparing with other than the radio technique for the first time.

  13. F3 layer development during quiet and disturbed periods as observed at conjugate locations in Brazil: The role of the meridional wind

    Science.gov (United States)

    Batista, Inez S.; Candido, C. M. N.; Souza, J. R.; Abdu, M. A.; de Araujo, R. C.; Resende, L. C. A.; Santos, A. M.

    2017-02-01

    In this work we use ionospheric data from two low-latitude stations located north and south of the geomagnetic equator, at approximately the same magnetic longitude, in order to study the occurrence of the F3 layer. The location of the stations being at almost geomagnetically conjugate points is such that the effects of the electric field/vertical plasma drift and diffusion will be almost symmetric around the magnetic equator. Under this configuration it is possible to deduce the effect of meridional wind in the F3 layer occurrence. Our results show that during the December solstice the layer will be present at the Southern Hemisphere (SH) location in 97% of the days and in the Northern Hemisphere (NH) location in only 4% of the days. In the June solstice the situation is reversed with the occurrence in the NH being 82% and 16% in the SH. For the March equinox the occurrence is low at both locations (4% in NH and 7% in SH), being mainly present during magnetically disturbed periods. The analysis of the effective meridional wind based on the Horizontal Wind Model and on the asymmetry of the F layer peak height observed at the two locations confirms the ubiquitous role of the wind in the F3 layer formation and/or persistence during both quiet and disturbed periods. The B0 parameter, that is a measure of the thickness of the bottomside F region profile, revealed to be a good proxy for the F3 layer occurrence.

  14. An Observer-Based Controller with a LMI-Based Filter against Wind-Induced Motion for High-Rise Buildings

    Directory of Open Access Journals (Sweden)

    Chao-Jun Chen

    2017-01-01

    Full Text Available Active mass damper (AMD control system is proposed for high-rise buildings to resist a strong wind. However, negative influence of noise in sensors impedes the application of AMD systems in practice. To reduce the adverse influence of noise on AMD systems, a Kalman filter and a linear matrix inequality- (LMI- based filter are designed. Firstly, a ten-year return period fluctuating wind load is simulated by mixed autoregressive-moving average (MARMA method, and its reliability is tested by wind speed power spectrum and correlation analysis. Secondly, a designed state observer with different filters uses wind-induced acceleration responses of a high-rise building as the feedback signal that includes noise to calculate control force in this paper. Finally, these methods are applied to a numerical example of a high-rise building and an experiment of a single span four-storey steel frame. Both numerical and experimental results are presented to verify that both Kalman filter and LMI-based filter can effectively suppress noise, but only the latter can guarantee the stability of AMD parameters.

  15. Evidence from large scale numerical simulations and observations for a relationship between magnetic reconnection, current sheets and intermittent turbulence in the solar wind

    Science.gov (United States)

    Osman, Kareem; Matthaeus, William; Gosling, Jack; Greco, Antonella; Servidio, Sergio; Chapman, Sandra; Hnat, Bogdan; Phan, Tai

    2014-05-01

    Turbulence is ubiquitous in space plasmas and leads to the emergence of coherent structures. These display signatures of intermittency in the form of rare large amplitude fluctuations that produce highly non-Gaussian heavy tailed probability distribution functions, and have properties consistent with dynamical generation by strong plasma turbulence. Therefore, coherent structures embedded in the solar wind should reflect the nonlinear dynamics that give rise to intermittency, such as random magnetic reconnection between adjoining flux tubes. We present evidence from large scale numerical simulations and observations of a relationship between magnetic reconnection, current sheets and intermittent turbulence in the solar wind for the first time using in-situ measurements from the Wind spacecraft at 1 AU. Reconnection exhausts and current sheets are concentrated in spatially non-uniform intermittent structures, such that 87-92% and ~9% respectively are associated with the most non-Gaussian 1% of fluctuations. The likelihood that an identified current sheet will also correspond to an active reconnection site increases dramatically as the least intermittent fluctuations are removed. Hence, the turbulent solar wind contains a hierarchy of intermittent structures that are increasingly linked to current sheets, which in turn are more likely to correspond to sites of active magnetic reconnection. These results could have far reaching implications for laboratory and astrophysical plasmas where turbulence and magnetic reconnection are ubiquitous.

  16. Application of Ensemble Sensitivity Analysis to Observation Targeting for Short-term Wind Speed Forecasting in the Tehachapi Region Winter Season

    Energy Technology Data Exchange (ETDEWEB)

    Zack, John [AWS Truepower, LLC, Albany, NY (United States); Natenberg, Eddie [AWS Truepower, LLC, Albany, NY (United States); Young, Steve [AWS Truepower, LLC, Albany, NY (United States); Van Knowe, Glenn [AWS Truepower, LLC, Albany, NY (United States); Waight, Ken [AWS Truepower, LLC, Albany, NY (United States); Manobainco, John [AWS Truepower, LLC, Albany, NY (United States); Kamath, Chandrika [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2010-10-20

    This study extends the wind power forecast sensitivity work done by Zack et al. (2010a, b) in two prior research efforts. Zack et al. (2010a, b) investigated the relative predictive value and optimal combination of different variables/locations from correlated sensitivity patterns. Their work involved developing the Multiple Observation Optimization Algorithm (MOOA) and applying the algorithm to the results obtained from the Ensemble Sensitivity Analysis (ESA) method (Ancell and Hakim 2007; Torn and Hakim 2008).

  17. Current observations from a looking down vertical V-ADCP: interaction with winds and tide? The case of Giglio Island (Tyrrhenian Sea, Italy)

    OpenAIRE

    Laura Cutroneo; Gabriele Ferretti; Davide Scafidi; Gian Domenico Ardizzone; Greta Vagge; Marco Capello

    2017-01-01

    In the context of the environmental monitoring of the Concordia wreck removal project, measurements of currents, winds and sea level height were made along the eastern coast of the Giglio Island, Tyrrhenian Sea (Italy), during 2012–2013. The aim of the study was to investigate the effect of atmospheric forcing and periodic sea-level changes on the coastal currents. Normalised Cross-Correlation Function analysis allowed us to correlate these observations. A marked inter-seasonal variability wa...

  18. Ulysse à la dérive : de déviations en faux-fuyants, un itinéraire élisabéthain Wandering with Ulysses: Interpretative Deviations in Elizabethan Texts

    Directory of Open Access Journals (Sweden)

    Charlotte Coffin

    2009-06-01

    Full Text Available From Antiquity onwards, the Ulysses myth has been subject to contradictory interpretations, depending on whether his cunning intelligence is seen to indicate wisdom or deceitfulness, and whether the stress is laid on the Greek’s sly speeches or on his painful travels. Yet Elizabethan texts paradoxically deviate from this rich tradition as they often present a much simpler version of the hero, where the phrase “wise Ulysses” excludes any attempt at critical investigation. This article offers a survey of a variety of texts and genres, in order to show how both allegorical interpretations and rhetorical exploitations of the myth tend to erase ambivalence, whereas Shakespeare’s Troilus and Cressida fully explores its suggestions of  the dangerous power of eloquence.

  19. Profiling Radar Observations and Numerical Simulations of a Downslope Wind Storm and Rotor on the Lee of the Medicine Bow Mountains in Wyoming

    Directory of Open Access Journals (Sweden)

    Binod Pokharel

    2017-02-01

    Full Text Available This study describes a downslope wind storm event observed over the Medicine Bow range (Wyoming, USA on 11 January 2013. The University of Wyoming King Air (UWKA made four along-wind passes over a five-hour period over the mountain of interest. These passes were recognized as among the most turbulent ones encountered in many years by crew members. The MacCready turbulence meter aboard the UWKA measured moderate to severe turbulence conditions on each pass in the lee of the mountain range, with eddy dissipation rate values over 0.5 m2/3 s−1. Three rawinsondes were released from an upstream location at different times. This event is simulated using the non-hydrostatic Weather Research and Forecast (WRF model at an inner- domain resolution of 1 km. The model produces a downslope wind storm, notwithstanding some discrepancies between model and rawinsonde data in terms of upstream atmospheric conditions. Airborne Wyoming Cloud Radar (WCR vertical-plane Doppler velocity data from two beams, one pointing to the nadir and one pointing slant forward, are synthesized to obtain a two-dimensional velocity field in the vertical plane below flight level. This synthesis reveals the fine-scale details of an orographic wave breaking event, including strong, persistent downslope acceleration, a strong leeside updraft (up to 10 m·s−1 flanked by counter-rotating vortices, and deep turbulence, extending well above flight level. The analysis of WCR-derived cross-mountain flow in 19 winter storms over the same mountain reveals that cross-mountain flow acceleration and downslope wind formation are difficult to predict from upstream wind and stability profiles.

  20. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  1. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Said Said, Usama; Badger, Jake

    2006-01-01

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  2. Evaporation suppression from reservoirs using floating covers: Lab scale wind-tunnel observations and mechanistic model predictions

    Science.gov (United States)

    Or, Dani; Lehmann, Peter; Aminzadeh, Milad; Sommer, Martina; Wey, Hannah; Krentscher, Christiane; Wunderli, Hans; Breitenstein, Daniel

    2017-04-01

    The competition over dwindling fresh water resources is expected to intensify with projected increase in human population in arid regions, expansion of irrigated land and changes in climate and drought patterns. The volume of water stored in reservoirs would also increase to mitigate seasonal shortages due to rainfall variability and to meet irrigation water needs. By some estimates up to half of the stored water is lost to evaporation, thereby exacerbating the water scarcity problem. Recently, there is an upsurge in the use of self-assembling floating covers to suppress evaporation, yet the design and implementation remain largely empirical. We report a systematic experimental evaluation of different cover types and external drivers (radiation, wind, wind plus radiation) on evaporation suppression and energy balance of a 1.4 m2 basin placed in a wind-tunnel. Surprisingly, evaporation suppression by black and white floating covers (balls and plates) were similar despite significantly different energy balance regimes over the cover surfaces. Moreover, the evaporation suppression efficiency was a simple function of the uncovered area (square root of the uncovered fraction) with linear relations with the covered area in some cases. The thermally decoupled floating covers offer an efficient solution to the evaporation suppression with limited influence of the surface energy balance (water temperature for black and white covers was similar and remained nearly constant). The results will be linked with a predictive evaporation-energy balance model and issues of spatial scales and long exposure times will be studied.

  3. Satellite winds as a tool for offshore wind resource assessment: The Great Lakes Wind Atlas

    DEFF Research Database (Denmark)

    Doubrawa, Paula; Barthelmie, Rebecca Jane; Pryor, Sara C.

    2015-01-01

    This work presents a new observational wind atlas for the Great Lakes, and proposes a methodology to combine in situ and satellite wind observations for offshore wind resource assessment. Efficient wind energy projects rely on accurate wind resource estimates, which are complex to obtain offshore...... the North American Regional Reanalysis. Generalized wind climates are obtained for each buoy and coastal site with the wind model WAsP, and combined into a single wind speed estimate for the Great Lakes region. The method of classes is used to account for the temporal sparseness in the SAR data set...

  4. RADIO POLARIZATION OBSERVATIONS OF THE SNAIL: A CRUSHED PULSAR WIND NEBULA IN G327.1–1.1 WITH A HIGHLY ORDERED MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y. K.; Ng, C.-Y. [Department of Physics, The University of Hong Kong, Pokfulam Road (Hong Kong); Bucciantini, N. [INAF—Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Slane, P. O. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Gaensler, B. M. [Dunlap Institute for Astronomy and Astrophysics, The University of Toronto, Toronto, ON M5S 3H4 (Canada); Temim, T., E-mail: ncy@bohr.physics.hku.hk [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2016-04-01

    Pulsar wind nebulae (PWNe) are suggested to be acceleration sites of cosmic rays in the Galaxy. While the magnetic field plays an important role in the acceleration process, previous observations of magnetic field configurations of PWNe are rare, particularly for evolved systems. We present a radio polarization study of the “Snail” PWN inside the supernova remnant G327.1−1.1 using the Australia Telescope Compact Array. This PWN is believed to have been recently crushed by the supernova (SN) reverse shock. The radio morphology is composed of a main circular body with a finger-like protrusion. We detected a strong linear polarization signal from the emission, which reflects a highly ordered magnetic field in the PWN and is in contrast to the turbulent environment with a tangled magnetic field generally expected from hydrodynamical simulations. This could suggest that the characteristic turbulence scale is larger than the radio beam size. We built a toy model to explore this possibility, and found that a simulated PWN with a turbulence scale of about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50%–75% provides the best match to observations. This implies substantial mixing between the SN ejecta and pulsar wind material in this system.

  5. Characteristics of Arctic winds at CANDAC-PEARL (80° N, 86° W and Svalbard (78° N, 16° E for 2006–2009: radar observations and comparisons with the model CMAM-DAS

    Directory of Open Access Journals (Sweden)

    A. H. Manson

    2011-10-01

    Full Text Available Operation of a Meteor Wind Radar (MWR at Eureka, Ellesmere Island (80° N, 86° W began in February 2006; this is the location of the Polar Environmental and Atmospheric Research Laboratory (PEARL, operated by the "Canadian Network for the Detection of Atmospheric Change" (CANDAC. The first 36 months of wind data (82–97 km are here combined with contemporaneous winds from the Meteor Wind Radar at Adventdalen, Svalbard (78° N, 16° E, to provide the first evidence for substantial interannual variability (IAV of longitudinally spaced observations of mean/background winds and waves at such High Arctic latitudes. The influences of "Sudden Stratospheric Warmings" (SSW are also apparent. Monthly meridional (north-south, NS 3-year means for each location/radar demonstrate that winds (82–97 km differ significantly between Canada and Norway, with winter-equinox values generally northward over Eureka and southward over Svalbard. Using January 2008 as case study, these oppositely directed meridional winds are related to mean positions of the Arctic mesospheric vortex. The vortex is from the Canadian Middle Atmosphere Model, with its Data Assimilation System (CMAM-DAS. The characteristics of "Sudden stratospheric Warmings" SSW in each of the three winters are noted, as well as their uniquely distinctive short-term mesospheric wind disturbances. Comparisons of the mean winds over 36 months at 78 and 80° N, with those within CMAM-DAS, are featured. E.g. for 2007, while both monthly mean EW and NS winds from CMAM/radar are quite similar over Eureka (82–88 km, the modeled autumn-winter NS winds over Svalbard (73–88 km differ significantly from observations. The latter are southward, and the modeled winds over Svalbard are predominately northward. The mean positions of the winter polar vortex are related to these differences.

  6. Observations of high-energy jets in the corona above the quiet sun, the heating of the corona, and the acceleration of the solar wind

    Science.gov (United States)

    Brueckner, G. E.; Bartoe, J.-D. F.

    1983-01-01

    High spatial resolution observations of the ultraviolet solar spectrum which reveal high-energy events in the quiet sun are presented. The tandem Wadsworth spectrograph used to make the observations is described along with the observing techniques, and a brief description of the characteristics of high-resolution transition zone spectra is given. The sizes, velocities, line profiles, time behavior, temperature range, differential emission measures, densities, masses, energies, and birthrates of turbulent events and jets in the quiet sun are derived from the observations and discussed. Possible accelerating mechanisms for these events are discussed, and the consequences of these events for the heating of the solar corona are discussed. A cloud model of the solar wind is proposed and possible correlations between the high-energy events and other solar fine-structure features are discussed.

  7. Long-term observations of the wind field in the Antarctic and Arctic mesosphere and lower-thermosphere at conjugate latitudes

    Science.gov (United States)

    Iimura, H.; Fritts, D. C.; Tsutsumi, M.; Nakamura, T.; Hoffmann, P.; Singer, W.

    2011-10-01

    Mean winds, semidiurnal and diurnal tides, and trends and long-period oscillations spanning a solar cycle (from early 1999 through June 2010) measured by medium frequency (MF) radars at conjugate Antarctic and Arctic latitudes (Syowa, Antarctica, 69°S, 39.6°E, and Andenes, Norway, 69.3°N, 16°E) are described and compared. Zonal mean winds are stronger and more uniform from year to year over the Antarctic, with a stronger eastward winter jet spanning the range of altitudes presented (70 to 96 km). The summer westward jet is also stronger and maximizes at higher altitudes over the Antarctic than over the Arctic. The eastward winter jet over the Arctic, while generally weaker, exhibits a localized maximum in late winter at ˜2 to 3 year intervals. Meridional mean winds likewise achieve somewhat stronger maxima at higher altitudes over the Antarctic than over the Arctic. Semidiurnal tide amplitudes are typically somewhat larger over the Antarctic and similar in the two components, with maxima at ˜85 km or above and narrow responses that tend to cluster from ˜February to May and ˜September to November over the Antarctic and from ˜December to February and ˜June to September over the Arctic. Zonal diurnal tide amplitudes are quite similar between the sites, with maxima extending from ˜70 to 90 km and slightly stronger over the Antarctic. Meridional diurnal amplitudes display more significant growth with altitude, achieve stronger maxima at the highest altitudes presented, and typically exhibit a single and narrow maximum during December to February over the Antarctic and double maxima from ˜May to September over the Arctic. Also discussed are trends and long-period oscillations over a solar cycle observed in these mean and tidal wind fields.

  8. Superorbital Periodic Modulation in Wind-Accretion High-Mass X-Ray Binaries from Swift Burst Alert Telescope Observations

    Science.gov (United States)

    Corbet, Robin H. D.; Krimm, Hans A.

    2013-01-01

    We report the discovery using data from the Swift-Burst Alert Telescope (BAT) of superorbital modulation in the wind-accretion supergiant high-mass X-ray binaries 4U 1909+07 (= X 1908+075), IGR J16418-4532, and IGR J16479-4514. Together with already known superorbital periodicities in 2S 0114+650 and IGR J16493-4348, the systems exhibit a monotonic relationship between superorbital and orbital periods. These systems include both supergiant fast X-ray transients and classical supergiant systems, and have a range of inclination angles. This suggests an underlying physical mechanism which is connected to the orbital period. In addition to these sources with clear detections of superorbital periods, IGR J16393-4643 (= AX J16390.4-4642) is identified as a system that may have superorbital modulation due to the coincidence of low-amplitude peaks in power spectra derived from BAT, Rossi X-Ray Timing Explorer Proportional Counter Array, and International Gamma-Ray Astrophysics Laboratory light curves. 1E 1145.1-6141 may also be worthy of further attention due to the amount of low-frequency modulation of its light curve. However, we find that the presence of superorbital modulation is not a universal feature of wind-accretion supergiant X-ray binaries.

  9. Magnetic Fields Around the Heliosphere: Theory vs Observations

    Science.gov (United States)

    Pogorelov, Nikolai

    2016-07-01

    Voyager in situ measurements of the magnetic field around the heliosphere are the source of invaluable information about the interface between the solar wind (SW) and local interstellar medium (LISM). On the other hand, they are quite challenging for theoretical analysis unless accompanied by remote observations of neutral atoms the Interstellar Boundary Explorer (IBEX) and Ulysses missions. Of particular interest is the fine structure of the heliopause due to its instability and possible magnetic reconnection. Both phenomena may have contributed to the remarkable changes in the galactic and anomalous cosmic ray fluxes observed by Voyager 1 within a one-month period of 2012 after which the spacecraft penetrated into the LISM. Draping of the heliopause by the interstellar magnetic field affects the position of the bright ribbon of enhanced ENA flux observed by IBEX on the celestial sphere and 2-3 kHz radio emission caused by shock propagation through the outer heliosheath observed by Voyager 1. Interstellar magnetic field determines the structure of the bow wave in front of the heliopause. Moreover, magnetic fields define the orientation and shape of the heliotail, the features of which have been observed by IBEX. Recent numerical simulations show that the details of the large-scale interstellar magnetic field modification caused by the presence of the heliotail may be the source of the observed 1-10 TeV cosmic ray anisotropy studied in detail in numerous air shower measurements around the world. In this paper, an overview will be given of the recent theoretical and simulations results describing the magnetic field distribution around the heliosphere. The objective of the talk is to connect observational and theoretical results, and outline challenges that are going to inspire the heliospheric community in the coming years.

  10. Summertime wind climate in Yerevan: valley wind systems

    Science.gov (United States)

    Gevorgyan, Artur

    2017-03-01

    1992-2014 wind climatology analysis in Yerevan is presented with particular focus given to the summertime thermally induced valley wind systems. Persistence high winds are observed in Yerevan during July-August months when the study region is strongly affected by a heat-driven plain-plateau circulation. The local valley winds arrive in Yerevan in the evening hours, generally, from 1500 to 1800 UTC, leading to rapid enhancement of wind speeds and dramatic changes in wind direction. Valley-winds significantly impact the local climate of Yerevan, which is a densely populated city. These winds moderate evening temperatures after hot and dry weather conditions observed during summertime afternoons. On the other hand, valley winds result in significantly higher nocturnal temperatures and more frequent occurrence of warm nights (tn90p) in Yerevan due to stronger turbulent mixing of boundary layer preventing strong surface cooling and temperature drop in nighttime and morning hours. The applied WRF-ARW limited area model is able to simulate the key features of the observed spatial pattern of surface winds in Armenia associated with significant terrain channeling, wind curls, etc. By contrast, ECMWF EPS global model fails to capture mesoscale and local wind systems over Armenia. However, the results of statistical verification of surface winds in Yerevan showed that substantial biases are present in WRF 18-h wind forecasts, as well as, the temporal variability of observed surface winds is not reproduced adequately in WRF-ARW model.

  11. Waveform-based spaceborne GNSS-R wind speed observation: Demonstration and analysis using UK TechDemoSat-1 data

    Science.gov (United States)

    Wang, Feng; Yang, Dongkai; Zhang, Bo; Li, Weiqiang

    2018-03-01

    This paper explores two types of mathematical functions to fit single- and full-frequency waveform of spaceborne Global Navigation Satellite System-Reflectometry (GNSS-R), respectively. The metrics of the waveforms, such as the noise floor, peak magnitude, mid-point position of the leading edge, leading edge slope and trailing edge slope, can be derived from the parameters of the proposed models. Because the quality of the UK TDS-1 data is not at the level required by remote sensing mission, the waveforms buried in noise or from ice/land are removed by defining peak-to-mean ratio, cosine similarity of the waveform before wind speed are retrieved. The single-parameter retrieval models are developed by comparing the peak magnitude, leading edge slope and trailing edge slope derived from the parameters of the proposed models with in situ wind speed from the ASCAT scatterometer. To improve the retrieval accuracy, three types of multi-parameter observations based on the principle component analysis (PCA), minimum variance (MV) estimator and Back Propagation (BP) network are implemented. The results indicate that compared to the best results of the single-parameter observation, the approaches based on the principle component analysis and minimum variance could not significantly improve retrieval accuracy, however, the BP networks obtain improvement with the RMSE of 2.55 m/s and 2.53 m/s for single- and full-frequency waveform, respectively.

  12. The turning of the wind in the atmospheric boundary layer

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Gryning, Sven-Erik; Floors, Rogier Ralph

    2014-01-01

    Here we use accurate observations of the wind speed vector to analyze the behavior with height of the wind direction. The observations are a combination of tall meteorological mast and long-range wind lidar measurements covering the entire atmospheric boundary layer. The observations were performed...... winds underpredict the turning of the wind and the boundary-layer winds in general....

  13. Observation of Chorus Waves by the Van Allen Probes: Dependence on Solar Wind Parameters and Scale Size

    Science.gov (United States)

    Aryan, Homayon; Sibeck, David; Balikhin, Michael; Agapitov, Oleksiy; Kletzing, Craig

    2016-01-01

    Highly energetic electrons in the Earths Van Allen radiation belts can cause serious damage to spacecraft electronic systems and affect the atmospheric composition if they precipitate into the upper atmosphere. Whistler mode chorus waves have attracted significant attention in recent decades for their crucial role in the acceleration and loss of energetic electrons that ultimately change the dynamics of the radiation belts. The distribution of these waves in the inner magnetosphere is commonly presented as a function of geomagnetic activity. However, geomagnetic indices are nonspecific parameters that are compiled from imperfectly covered ground based measurements. The present study uses wave data from the two Van Allen Probes to present the distribution of lower band chorus waves not only as functions of single geomagnetic index and solar wind parameters but also as functions of combined parameters. Also the current study takes advantage of the unique equatorial orbit of the Van Allen Probes to estimate the average scale size of chorus wave packets, during close separations between the two spacecraft, as a function of radial distance, magnetic latitude, and geomagnetic activity, respectively. Results show that the average scale size of chorus wave packets is approximately 13002300 km. The results also show that the inclusion of combined parameters can provide better representation of the chorus wave distributions in the inner magnetosphere and therefore can further improve our knowledge of the acceleration and loss of radiation belt electrons.

  14. Observation of chorus waves by the Van Allen Probes: dependence on solar wind parameters and scale size

    Science.gov (United States)

    Aryan, H.; Sibeck, D. G.; Balikhin, M. A.; Agapitov, O. V.; Kletzing, C.

    2016-12-01

    Highly energetic electrons in the Earth's Van Allen radiation belts can cause serious damage to spacecraft electronic systems, and affect the atmospheric composition if they precipitate into the upper atmosphere. Whistler mode chorus waves have attracted significant attention in recent decades for their crucial role in the acceleration and loss of energetic electrons that ultimately change the dynamics of the radiation belts. The distribution of these waves in the inner magnetosphere is commonly presented as a function of geomagnetic activity. However, geomagnetic indices are non-specific parameters that are compiled from imperfectly covered ground based measurements. The present study uses wave data from the two Van Allen Probes to present the distribution of lower band chorus waves not only as functions of single geomagnetic index and solar wind parameters, but also as functions of combined parameters. Also the current study takes advantage of the unique equatorial orbit of the Van Allen Probes to estimate the average scale size of chorus wave packets, during close separations between the two spacecraft, as a function of radial distance, magnetic latitude, and geomagnetic activity respectively. Results show that the average scale size of chorus wave packets is approximately 1300 - 2300 km. The results also show that the inclusion of combined parameters can provide better representation of the chorus wave distributions in the inner magnetosphere, and therefore can further improve our knowledge of the acceleration and loss of radiation belt electrons.

  15. Gap Filling of the CALYPSO HF Radar Sea Surface Current Data through Past Measurements and Satellite Wind Observations

    Directory of Open Access Journals (Sweden)

    Adam Gauci

    2016-01-01

    Full Text Available High frequency (HF radar installations are becoming essential components of operational real-time marine monitoring systems. The underlying technology is being further enhanced to fully exploit the potential of mapping sea surface currents and wave fields over wide areas with high spatial and temporal resolution, even in adverse meteo-marine conditions. Data applications are opening to many different sectors, reaching out beyond research and monitoring, targeting downstream services in support to key national and regional stakeholders. In the CALYPSO project, the HF radar system composed of CODAR SeaSonde stations installed in the Malta Channel is specifically serving to assist in the response against marine oil spills and to support search and rescue at sea. One key drawback concerns the sporadic inconsistency in the spatial coverage of radar data which is dictated by the sea state as well as by interference from unknown sources that may be competing with transmissions in the same frequency band. This work investigates the use of Machine Learning techniques to fill in missing data in a high resolution grid. Past radar data and wind vectors obtained from satellites are used to predict missing information and provide a more consistent dataset.

  16. A class of flux observers for doubly-fed induction generators used in small power wind generation systems

    DEFF Research Database (Denmark)

    Lascu, C.; Boldea, I.; Blaabjerg, Frede

    2013-01-01

    This paper investigates a family of stator and rotor flux observers for sensorless operation of doubly-fed induction generators (DFIG). Four stator flux observer topologies are described and compared. All proposed schemes use the voltage and current models connected in parallel or in series. For ...

  17. Spatial gradients of GCR protons in the inner heliosphere derived from Ulysses COSPIN/KET and PAMELA measurements

    Science.gov (United States)

    Gieseler, J.; Heber, B.

    2016-05-01

    Context. During the transition from solar cycle 23 to 24 from 2006 to 2009, the Sun was in an unusual solar minimum with very low activity over a long period. These exceptional conditions included a very low interplanetary magnetic field (IMF) strength and a high tilt angle, which both play an important role in the modulation of galactic cosmic rays (GCR) in the heliosphere. Thus, the radial and latitudinal gradients of GCRs are very much expected to depend not only on the solar magnetic epoch, but also on the overall modulation level. Aims: We determine the non-local radial and the latitudinal gradients of protons in the rigidity range from ~0.45 to 2 GV. Methods: This was accomplished by using data from the satellite-borne experiment Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) at Earth and the Kiel Electron Telescope (KET) onboard Ulysses on its highly inclined Keplerian orbit around the Sun with the aphelion at Jupiter's orbit. Results: In comparison to the previous A> 0 solar magnetic epoch, we find that the absolute value of the latitudinal gradient is lower at higher and higher at lower rigidities. This energy dependence is therefore a crucial test for models that describe the cosmic ray transport in the inner heliosphere.

  18. XMM-Newton Observations of MBM 12: More Constraints on the Solar Wind Charge Exchange and Local Bubble Emissions

    Science.gov (United States)

    Koutroumpa, Dimitra; Smith, Randall K.; Edgar, Richard J.; Kuntz, Kip D.; Plucinsky, Paul P.; Snowden, Steven L.

    2010-01-01

    We present the first analysis of an XMM-Newton observation of the nearby molecular cloud MBM 12. We find that in the direction of MBM 12 the total O VII (0.57 keV) triplet emission is 1.8(+0.5/-0.6) photons/sq cm/s/sr (or Line Units - LU) while for the O VIII (0.65 keV) line emission we find a 3(sigma) upper limit of Newton observations. This comparison provides new constraints on the relative heliospheric and Local Bubble contributions to the local diffuse X-ray background. The heliospheric SWCX model predicts 0.82 LU for O VII, which accounts for approx. 46+/-15% of the observed value, and 0.33 LU for the O VIII line emission consistent with the XMM-Newton observed value. We discuss our results in combination with previous observations of the MBM 12 with CHANDRA and Suzaku.

  19. CONSTRAINTS ON THE GALACTIC POPULATION OF TeV PULSAR WIND NEBULAE USING FERMI LARGE AREA TELESCOPE OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Acero, F.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Allafort, A.; Bechtol, K.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Buehler, R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L. [Universita di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Universite Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D.; Buson, S. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brigida, M. [Dipartimento di Fisica ' ' M. Merlin' ' dell' Universita e del Politecnico di Bari, I-70126 Bari (Italy); Bruel, P., E-mail: funk@slac.stanford.edu, E-mail: joshualande@gmail.com, E-mail: lemoine@cenbg.in2p3.fr, E-mail: rousseau@cenbg.in2p3.fr [Laboratoire Leprince-Ringuet, Ecole polytechnique, CNRS/IN2P3, F-91128 Palaiseau (France); and others

    2013-08-10

    Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV {gamma}-ray emitters. Since launch, the Fermi Large Area Telescope (LAT) has identified five high-energy (100 MeV < E < 100 GeV) {gamma}-ray sources as PWNe and detected a large number of PWN candidates, all powered by young and energetic pulsars. The wealth of multi-wavelength data available and the new results provided by Fermi-LAT give us an opportunity to find new PWNe and to explore the radiative processes taking place in known ones. The TeV {gamma}-ray unidentified (UNID) sources are the best candidates for finding new PWNe. Using 45 months of Fermi-LAT data for energies above 10 GeV, an analysis was performed near the position of 58 TeV PWNe and UNIDs within 5 Degree-Sign of the Galactic plane to establish new constraints on PWN properties and find new clues on the nature of UNIDs. Of the 58 sources, 30 were detected, and this work provides their {gamma}-ray fluxes for energies above 10 GeV. The spectral energy distributions and upper limits, in the multi-wavelength context, also provide new information on the source nature and can help distinguish between emission scenarios, i.e., between classification as a pulsar candidate or as a PWN candidate. Six new GeV PWN candidates are described in detail and compared with existing models. A population study of GeV PWN candidates as a function of the pulsar/PWN system characteristics is presented.

  20. South Baltic Wind Atlas

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Hahmann, Andrea N.; Hasager, Charlotte Bay

    A first version of a wind atlas for the South Baltic Sea has been developed using the WRF mesoscale model and verified by data from tall Danish and German masts. Six different boundary-layer parametrization schemes were evaluated by comparing the WRF results to the observed wind profiles at the m......A first version of a wind atlas for the South Baltic Sea has been developed using the WRF mesoscale model and verified by data from tall Danish and German masts. Six different boundary-layer parametrization schemes were evaluated by comparing the WRF results to the observed wind profiles...

  1. Modelling of Wind Turbine Loads nearby a Wind Farm

    Science.gov (United States)

    Roscher, B.; Werkmeister, A.; Jacobs, G.; Schelenz, R.

    2017-05-01

    Each wind turbine experiences a variety of loads during its lifetime, especially inside a wind farm due to the wake effect between the turbines. This paper describes a possibility to observe a load spectrum while considering wake effects in a wind farm by through the turbulence intensity. The turbulence intensity is distributed along the wind rose of Alpha Ventus. For each turbulence intensity, a Weibull characteristic is calculated. The resulting wind fields are used to determine the loads through a multibody simulation of an imaginary wind turbine located at FINO-1, representing a closely placed wind turbine at the outer edge of a wind farm. These loads are analyzed and summed up. As expected, the change of the turbulence intensity due to the wake effect has an impact on the internal loading of a wind turbine inside a wind farm. Based on the assumed loading conditions, the maximum loads increased by a factor of almost 2.5.

  2. The use of real-time off-site observations as a methodology for increasing forecast skill in prediction of large wind power ramps one or more hours ahead of their impact on a wind plant.

    Energy Technology Data Exchange (ETDEWEB)

    Martin Wilde, Principal Investigator

    2012-12-31

    ABSTRACT Application of Real-Time Offsite Measurements in Improved Short-Term Wind Ramp Prediction Skill Improved forecasting performance immediately preceding wind ramp events is of preeminent concern to most wind energy companies, system operators, and balancing authorities. The value of near real-time hub height-level wind data and more general meteorological measurements to short-term wind power forecasting is well understood. For some sites, access to onsite measured wind data - even historical - can reduce forecast error in the short-range to medium-range horizons by as much as 50%. Unfortunately, valuable free-stream wind measurements at tall tower are not typically available at most wind plants, thereby forcing wind forecasters to rely upon wind measurements below hub height and/or turbine nacelle anemometry. Free-stream measurements can be appropriately scaled to hub-height levels, using existing empirically-derived relationships that account for surface roughness and turbulence. But there is large uncertainty in these relationships for a given time of day and state of the boundary layer. Alternatively, forecasts can rely entirely on turbine anemometry measurements, though such measurements are themselves subject to wake effects that are not stationary. The void in free-stream hub-height level measurements of wind can be filled by remote sensing (e.g., sodar, lidar, and radar). However, the expense of such equipment may not be sustainable. There is a growing market for traditional anemometry on tall tower networks, maintained by third parties to the forecasting process (i.e., independent of forecasters and the forecast users). This study examines the value of offsite tall-tower data from the WINDataNOW Technology network for short-horizon wind power predictions at a wind farm in northern Montana. The presentation shall describe successful physical and statistical techniques for its application and the practicality of its application in an operational

  3. Observation

    Science.gov (United States)

    Kripalani, Lakshmi A.

    2016-01-01

    The adult who is inexperienced in the art of observation may, even with the best intentions, react to a child's behavior in a way that hinders instead of helping the child's development. Kripalani outlines the need for training and practice in observation in order to "understand the needs of the children and...to understand how to remove…

  4. Mean vertical wind in the mesosphere-lower thermosphere region (80–120 km deduced from the WINDII observations on board UARS

    Directory of Open Access Journals (Sweden)

    V. Fauliot

    Full Text Available The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S green-line emission in the Earth's mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.

  5. Mean vertical wind in the mesosphere-lower thermosphere region (80–120 km deduced from the WINDII observations on board UARS

    Directory of Open Access Journals (Sweden)

    V. Fauliot

    1997-09-01

    Full Text Available The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S green-line emission in the Earth's mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.

  6. Determine volcanic SO2 plume heights from satellite observations on a global scale using meteorological wind fields

    Science.gov (United States)

    Keicher, Viktoria; Hörmann, Christoph; Sihler, Holger; Platt, Ulrich; Warnach, Simon; Wagner, Thomas

    2017-04-01

    Satellite observations nowadays provide the global monitoring of volcanic plumes via sulphur dioxide (SO2) that is injected into the Earth's atmosphere. In turn, SO2 may lead to the formation of sulphate aerosols that can influence climate via direct and indirect radiative effects. The quantitative retrieval of SO2 requires an accurate plume height estimate in order to constrain total amounts for such events. However, especially for volcanic eruptions the vertical SO2 profile is typically unknown because of the initial conditions (e.g. individual explosions over an extended time period may lead to different gas layer altitudes). In recent years, satellite observations helped to improve global SO2 estimates, but still large uncertainties exist. Passive satellite remote sensing instruments in the UV/vis spectral range for example offer the opportunity to observe the location of a plume in two dimensions, but information about the corresponding height is limited. To gain further information about these plume profiles is not only interesting for the quantitative interpretation of satellite observations, but also in itself (e.g. to assess the radiative effect of volcanic plumes). Here, we present first results for a newly developed and systematic approach using the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) in combination with data for selected volcanic SO2 plumes originating from different volcanoes. The main plume informations retrieved by the satellite (i.e. plume location and observation time) are used as initial input parameters in order to estimate the plume's profile at the time of the measurements. The resulting trajectories can be used to constrain the eruption time and height. First comparisons show that retrieved results are in good agreement with direct local observations and reports. While the algorithm has been so far only applied to data from the second generation Global Ozone Monitoring Instrument (GOME-2), it may be

  7. Full non-linear treatment of the global thermospheric wind system. I - Mathematical method and analysis of forces. II - Results and comparison with observations

    Science.gov (United States)

    Blum, P. W.; Harris, I.

    1975-01-01

    The equations of horizontal motion of the neutral atmosphere between 120 and 500 km are integrated with the inclusion of all nonlinear terms of the convective derivative and the viscous forces due to vertical and horizontal velocity gradients. Empirical models of the distribution of neutral and charged particles are assumed to be known. The model of velocities developed is a steady state model. In Part I the mathematical method used in the integration of the Navier-Stokes equations is described and the various forces are analyzed. Results of the method given in Part I are presented with comparison with previous calculations and observations of upper atmospheric winds. Conclusions are that nonlinear effects are only significant in the equatorial region, especially at solstice conditions and that nonlinear effects do not produce any superrotation.

  8. The velocity law and acceleration of the hydrogen and OSiN discrete components observed in P Cyg's stellar wind in 1982

    Science.gov (United States)

    Markova, N.

    1990-05-01

    In this paper, the radial-velocity variations of the discrete absorption components observed in 1982 in some Balmer, oxygen, silicon and nitrogen lines in the visible spectrum of P Cyg are used to infer the velocity law and acceleration of these components. The shell ejection model is assessed (on the basis of some previous results) as being the most suitable explanation for the existence of these features. Some shell parameters such as time of formation, radial extent, internal velocity gradient and mass are determined as functions of the shell age. The interaction between the shell and quiescent wind is considered in a very simplified way. The rate of mass accretion and the amount of the accreted mass as shell lifetime functions are determined. A lower limit to the initial shell mass is fixed.

  9. X-RAY OBSERVATIONS OF THE SUPERNOVA REMNANT CTB 87 (G74.9+1.2): AN EVOLVED PULSAR WIND NEBULA

    Energy Technology Data Exchange (ETDEWEB)

    Matheson, H.; Safi-Harb, S. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba, R3T 2N2 (Canada); Kothes, R., E-mail: matheson@physics.umanitoba.ca, E-mail: samar@physics.umanitoba.ca, E-mail: roland.kothes@nrc-cnrc.gc.ca [Dominion Radio Astrophysical Observatory, National Research Council Herzberg, P.O. Box 248, Penticton, British Columbia, V2A 6J9 (Canada)

    2013-09-01

    Pulsar wind nebulae (PWNe) studies with the Chandra X-Ray Observatory have opened a new window to address the physics of pulsar winds, zoom on their interaction with their hosting supernova remnant (SNR) and interstellar medium, and identify their powering engines. We here present a new 70 ks, plus an archived 18 ks, Chandra ACIS observation of the SNR CTB 87 (G74.9+1.2), classified as a PWN with unusual radio properties and poorly studied in X-rays. We find that the peak of the X-ray emission is clearly offset from the peak of the radio emission by {approx}100'' and located at the southeastern edge of the radio nebula. We detect a point source-the putative pulsar-at the peak of the X-ray emission and study its spectrum separately from the PWN. This new point source, CXOU J201609.2+371110, is surrounded by a compact nebula displaying a torus-like structure and possibly a jet. A more extended diffuse nebula is offset from the radio nebula, extending from the point source to the northwest for {approx}250''. The spectra of the point source, compact nebula, and extended diffuse nebula are all well described by a power-law model with a photon index of 1.1 (0.7-1.6), 1.2 (0.9-1.4), and 1.7 (1.5-1.8), respectively, for a column density N{sub H} = 1.38 (1.21-1.57) Multiplication-Sign 10{sup 22} cm{sup -2} (90% confidence). The total X-ray luminosity of the source is {approx}1.6 Multiplication-Sign 10{sup 34} erg s{sup -1} at an assumed distance of 6.1 kpc, with {approx}2% and 6% contribution from the point source and compact nebula, respectively. The observed properties suggest that CTB 87 is an evolved ({approx}5-28 kyr) PWN, with the extended radio emission likely a ''relic'' PWN, as in Vela-X and G327.1-1.1. To date, however, there is no evidence for thermal X-ray emission from this SNR, and the SNR shell is still missing, suggesting expansion into a low-density medium (n{sub 0} < 0.2 D{sup -1/2}{sub 6.1} cm{sup -3}), likely

  10. Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

    Directory of Open Access Journals (Sweden)

    C. Senior

    Full Text Available High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF. Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed.

    Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation

  11. Strong sunward propagating flow bursts in the night sector during quiet solar wind conditions: SuperDARN and satellite observations

    Directory of Open Access Journals (Sweden)

    C. Senior

    2002-06-01

    Full Text Available High-time resolution data from the two Iceland SuperDARN HF radars show very strong nightside convection activity during a prolonged period of low geomagnetic activity and northward interplanetary magnetic field (IMF. Flows bursts with velocities ranging from 0.8 to 1.7 km/s are observed to propagate in the sunward direction with phase velocities up to 1.5 km/s. These bursts occur over several hours of MLT in the 20:00–01:00 MLT sector, in the evening-side sunward convection. Data from a simultaneous DMSP pass and POLAR UVI images show a very contracted polar cap and extended regions of auroral particle precipitation from the magnetospheric boundaries. A DMSP pass over the Iceland-West field-of-view while one of these sporadic bursts of enhanced flow is observed, indicates that the flow bursts appear within the plasma sheet and at its outward edge, which excludes Kelvin-Helmholtz instabilities at the magnetopause boundary as the generation mechanism. In the nightside region, the precipitation is more spot-like and the convection organizes itself as clockwise U-shaped structures. We interpret these flow bursts as the convective transport following plasma injection events from the tail into the night-side ionosphere. We show that during this period, where the IMF clock angle is around 70°, the dayside magnetosphere is not completely closed.Key words. Ionosphere (Auroral ionosphere; Ionospheremagnetosphere interactions; Particle precipitation

  12. Superposed epoch analysis of vertical ion velocity, electron temperature, field-aligned current, and thermospheric wind in the dayside auroral region as observed by DMSP and CHAMP

    Science.gov (United States)

    Kervalishvili, G.; Lühr, H.

    2016-12-01

    This study reports on the results obtained by a superposed epoch analysis (SEA) method applied to the electron temperature, vertical ion velocity, field-aligned current (FAC), and thermospheric zonal wind velocity at high-latitudes in the Northern Hemisphere. The SEA study is performed in a magnetic latitude versus magnetic local time (MLat-MLT) frame. The obtained results are based on observations collected during the years 2001-2005 by the CHAMP and DMSP (F13 and F15) satellites. The dependence on interplanetary magnetic field (IMF) orientations is also investigated using data from the NASA/GSFC's OMNI database. Further, the obtained results are subdivided into three Lloyd seasons of 130 days each, which are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32days), and local summer (1 July ± 65 days). A period of 130 days is needed by the CHAMP satellite to pass through all local times. The time and location of the electron temperature peaks from CHAMP measurements near the cusp region are used as the reference parameter for the SEA method to investigate the relationship between the electron temperature and other ionospheric quantities. The SEA derived MLat profiles of the electron temperature show a seasonal dependence, increasing from winter to summer, as expected. But, the temperature rise (difference between the reference temperature peak and the background electron temperature) strongly decreases towards local summer. The SEA derived MLat profiles of the ion vertical velocity at DMSP altitude show the same seasonal behaviour as the electron temperature rice. There exists a clear linear relation between these two variables with a quiet large correlation coefficient value, >0.9. The SEA derived MLat profiles of both, thermospheric zonal wind velocity and FAC, show a clear IMF By orientation dependence for all local seasons. The zonal wind velocity is prominently directed towards west in the MLat-MLT frame

  13. Offshore wind resource estimation for wind energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Badger, Merete; Mouche, A.

    2010-01-01

    Satellite remote sensing from active and passive microwave instruments is used to estimate the offshore wind resource in the Northern European Seas in the EU-Norsewind project. The satellite data include 8 years of Envisat ASAR, 10 years of QuikSCAT, and 23 years of SSM/I. The satellite observati......Satellite remote sensing from active and passive microwave instruments is used to estimate the offshore wind resource in the Northern European Seas in the EU-Norsewind project. The satellite data include 8 years of Envisat ASAR, 10 years of QuikSCAT, and 23 years of SSM/I. The satellite...... observations are compared to selected offshore meteorological masts in the Baltic Sea and North Sea. The overall aim of the Norsewind project is a state-of-the-art wind atlas at 100 m height. The satellite winds are all valid at 10 m above sea level. Extrapolation to higher heights is a challenge. Mesoscale...... modeling of the winds at hub height will be compared to data from wind lidars observing at 100 m above sea level. Plans are also to compare mesoscale model results and satellite-based estimates of the offshore wind resource....

  14. CORONAL HEATING BY SURFACE ALFVEN WAVE DAMPING: IMPLEMENTATION IN A GLOBAL MAGNETOHYDRODYNAMICS MODEL OF THE SOLAR WIND

    Energy Technology Data Exchange (ETDEWEB)

    Evans, R. M. [NASA Goddard Space Flight Center, Space Weather Lab, Greenbelt, MD 20771 (United States); Opher, M. [Astronomy Department, Boston University, 675 Commonwealth Avenue, Boston, MA 02215 (United States); Oran, R.; Van der Holst, B.; Sokolov, I. V.; Frazin, R.; Gombosi, T. I. [Center for Space Environment Modeling, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109 (United States); Vasquez, A., E-mail: Rebekah.e.frolov@nasa.gov [Instituto de Astronomia y Fisica del Espacio (CONICET-UBA) and FCEN (UBA), CC 67, Suc 28, Ciudad de Buenos Aires (Argentina)

    2012-09-10

    The heating and acceleration of the solar wind is an active area of research. Alfven waves, because of their ability to accelerate and heat the plasma, are a likely candidate in both processes. Many models have explored wave dissipation mechanisms which act either in closed or open magnetic field regions. In this work, we emphasize the boundary between these regions, drawing on observations which indicate unique heating is present there. We utilize a new solar corona component of the Space Weather Modeling Framework, in which Alfven wave energy transport is self-consistently coupled to the magnetohydrodynamic equations. In this solar wind model, the wave pressure gradient accelerates and wave dissipation heats the plasma. Kolmogorov-like wave dissipation as expressed by Hollweg along open magnetic field lines was presented in van der Holst et al. Here, we introduce an additional dissipation mechanism: surface Alfven wave (SAW) damping, which occurs in regions with transverse (with respect to the magnetic field) gradients in the local Alfven speed. For solar minimum conditions, we find that SAW dissipation is weak in the polar regions (where Hollweg dissipation is strong), and strong in subpolar latitudes and the boundaries of open and closed magnetic fields (where Hollweg dissipation is weak). We show that SAW damping reproduces regions of enhanced temperature at the boundaries of open and closed magnetic fields seen in tomographic reconstructions in the low corona. Also, we argue that Ulysses data in the heliosphere show enhanced temperatures at the boundaries of fast and slow solar wind, which is reproduced by SAW dissipation. Therefore, the model's temperature distribution shows best agreement with these observations when both dissipation mechanisms are considered. Lastly, we use observational constraints of shock formation in the low corona to assess the Alfven speed profile in the model. We find that, compared to a polytropic solar wind model, the wave

  15. Visual and radar observations of birds in relation to collision risk at the Horns Rev offshore wind farm. Annual status report 2003

    Energy Technology Data Exchange (ETDEWEB)

    Kjaer Christensen, T.; Hounisen, J.P.; Clausager, I.; Krag Petersen, I.

    2004-07-01

    The aim of the project is to assess the collision risk between birds and wind turbines at the Horns Rev wind farm. In 2003 the studies focused on describing bird movements in relation to the wind farm and to identify the species-specific behavioural responses towards the wind turbines shown by migrating and staging species. The Horns Rev area lies in a region known to be important for substantial water bird migration as well as holding internationally important numbers of several wintering and staging water bird species. (au)

  16. A PROPOSAL FOR OBSERVATION OF ATMOSPHERIC CIRCULATION AND TRANSPORT PROCESSES IN THE TROPOSPHERE AND LOWER STRATOSPHERE OVER ANTARCTICA WITH A NETWORK OF WIND PROFILERS

    OpenAIRE

    カンザワ, ヒロシ; Hiroshi, KANZAWA

    1992-01-01

    The wind profiler is a powerful tool to study atmospheric circulation and transport processes because it can measure not only horizontal components but also the vertical component of wind. A wind profiler developed originally by the U.S. NOAA/Environmental Research Laboratories/Wave Propagation Laboratory can measure winds from 0.5-17km above the surface with an altitude resolution of 250m and time resolution under 1 hour. The profiler uses a 400MHz UHF band, and the area of the antenna is ab...

  17. Application of Ensemble Sensitivity Analysis to Observation Targeting for Short-term Wind Speed Forecasting in the Washington-Oregon Region

    Energy Technology Data Exchange (ETDEWEB)

    Zack, John [AWS Truewind, LLC, Albany, NY (United States); Natenberg, Eddie [AWS Truewind, LLC, Albany, NY (United States); Young, Steve [AWS Truewind, LLC, Albany, NY (United States); Knowe, Glenn Van [AWS Truewind, LLC, Albany, NY (United States); Waight, Ken [AWS Truewind, LLC, Albany, NY (United States); Manobianco, John [AWS Truewind, LLC, Albany, NY (United States); Kamath, Chandrika [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2010-10-01

    To economically and reliably balance electrical load and generation, electrical grid operators, also called Balancing Authorities (BA), need highly accurate electrical power generation forecasts in time frames ranging from a few minutes to six hours ahead. As wind power generation increases, there is a requirement to improve the accuracy of 0- to 6-hour ahead wind power forecasts. Forecasts covering this short look-ahead period have depended heavily on short-term trends obtained from the actual power production and meteorological data of a wind generation facility. Additional data are often available from Numerical Weather Prediction (NWP) models and sometimes from off-site meteorological towers near wind generation facilities.

  18. Online Fault Identification Based on an Adaptive Observer for Modular Multilevel Converters Applied to Wind Power Generation Systems

    Directory of Open Access Journals (Sweden)

    Hui Liu

    2015-07-01

    Full Text Available Due to the possibility of putting a large number of modules consisting of switches and capacitors connected in series, the modular multilevel converter (MMC can easily be scaled to high power and high voltage power conversion, which is an attractive feature for filter-less and transformer-less design and helpful to achieve high efficiency. However, a significantly increased amount of sub-modules in a MMC may increase the requirements for sensors and also increase the risk of failures. As a result, fault detection and diagnosis of MMC sub-modules are of great importance for continuous operation and post-fault maintenance. Therefore, in this paper, an effective fault diagnosis technique for real-time diagnosis of the switching device faults covering both the open-circuit faults and the short-circuit faults in MMC sub-modules is proposed, in which the faulty phase and the fault type is detected by analyzing the difference among the three output load currents, while the localization of the faulty switches is achieved by comparing the estimation results by the adaptive observer. In contrast to other methods that use additional sensors or devices, the presented technique uses the measured phase currents only, which are already available for MMC control. In additional, its operation, effectiveness and robustness are confirmed by simulation results under different operating conditions and load conditions.

  19. Wind Braking of Magnetars

    Science.gov (United States)

    Tong, H.; Xu, R. X.; Song, L. M.; Qiao, G. J.

    2013-05-01

    We explore the wind braking of magnetars considering recent observations challenging the traditional magnetar model. There is evidence for strong multipole magnetic fields in active magnetars, but the dipole field inferred from spin-down measurements may be strongly biased by particle wind. Recent observations challenging the traditional model of magnetars may be explained naturally by the wind braking scenario: (1) the supernova energies of magnetars are of normal value; (2) the non-detection in Fermi observations of magnetars; (3) the problem posed by low magnetic field soft gamma-ray repeaters; (4) the relation between magnetars and high magnetic field pulsars; and (5) a decreasing period derivative during magnetar outbursts. Transient magnetars with L_x{<}-\\dot{E}_rot may still be magnetic dipole braking. This may explain why low luminosity magnetars are more likely to have radio emissions. A strong reduction of the dipole magnetic field is possible only when the particle wind is very collimated at the star surface. A small reduction of the dipole magnetic field may result from detailed considerations of magnetar wind luminosity. In the wind braking scenario, magnetars are neutron stars with a strong multipole field. For some sources, a strong dipole field may no longer be needed. A magnetism-powered pulsar wind nebula will be one of the consequences of wind braking. For a magnetism-powered pulsar wind nebula, we should see a correlation between the nebula luminosity and the magnetar luminosity. Under the wind braking scenario, a braking index smaller than three is expected. Future braking index measurement of a magnetar may tell us whether magnetars are wind braking or magnetic dipole braking.

  20. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...... of windhe interaction between wind and structures, where it is shown that wind loading depends strongly on this interaction...

  1. Sea state observation in island-sheltered nearshore zone based on in situ intermediate-water wave measurements and NCEP/CFSR wind data

    Digital Repository Service at National Institute of Oceanography (India)

    Dora, G.U.; SanilKumar, V.

    In this study, wind-seas, swells, and the coastal wind pattern are examined to interpret the temporal diversity of the sea state in the island-sheltered nearshore zone off Karwar on the west coast of India. The sea state is analyzed based on the sea...

  2. Fault tolerant wind speed estimator used in wind turbine controllers

    DEFF Research Database (Denmark)

    Odgaard, Peter Fogh; Stoustrup, Jakob

    2012-01-01

    Advanced control schemes can be used to optimize energy production and cost of energy in modern wind turbines. These control schemes most often rely on wind speed estimations. These designs of wind speed estimators are, however, not designed to be fault tolerant towards faults in the used sensors....... In this paper a fault tolerant wind speed estimator is designed based on a set of unknown input observers, each designed to the different sets of non-faulty sensors. Faults in the rotor, generator and wind speed sensors are considered. The designed wind speed estimator is passive tolerant towards faults...... in the wind speed sensors, and faults in the generator and rotor speed sensors are accommodated by an active fault tolerant observer scheme in which the faults are detected and identified, and the observer corresponding to the non-faulty sensors are used. The potential of the scheme is shown by applying...

  3. Lidar observations of low-level wind reversals over the Gulf of Lion and characterization of their impact on the water vapour variability

    Science.gov (United States)

    Di Girolamo, Paolo; Flamant, Cyrille; Cacciani, Marco; Summa, Donato; Stelitano, Dario; Richard, Evelyne; Ducrocq, Véronique; Fourrie, Nadia; Said, Frédérique

    2017-02-01

    Water vapour measurements from a ground-based Raman lidar and an airborne differential absorption lidar, complemented by high resolution numerical simulations from two mesoscale models (Arome-WMED and MESO-NH), are considered to investigate transition events from Mistral/Tramontane to southerly marine flow taking place over the Gulf of Lion in Southern France in the time frame September-October 2012, during the Hydrological Cycle in the Mediterranean Experiment (HyMeX) Special Observation Period 1 (SOP1). Low-level wind reversals associated with these transitions are found to have a strong impact on water vapour transport, leading to a large variability of the water vapour vertical and horizontal distribution. The high spatial and temporal resolution of the lidar data allow to monitor the time evolution of the three-dimensional water vapour field during these transitions from predominantly northerly Mistral/Tramontane flow to a predominantly southerly flow, allowing to identify the quite sharp separation between these flows, which is also quite well captured by the mesoscale models.

  4. Lidar Observations of Low-level Wind Reversals over the Gulf of Lion and Characterization of Their Impact on the Water Vapour Variability

    Directory of Open Access Journals (Sweden)

    Di Girolamo Paolo

    2016-01-01

    Full Text Available Water vapour measurements from a ground-based Raman lidar and an airborne differential absorption lidar, complemented by high resolution numerical simulations from two mesoscale models (Arome-WMED and MESO-NH, are considered to investigate transition events from Mistral/Tramontane to southerly marine flow taking place over the Gulf of Lion in Southern France in the time frame September-October 2012, during the Hydrological Cycle in the Mediterranean Experiment (HyMeX Special Observation Period 1 (SOP1. Low-level wind reversals associated with these transitions are found to have a strong impact on water vapour transport, leading to a large variability of the water vapour vertical and horizontal distribution. The high spatial and temporal resolution of the lidar data allow to monitor the time evolution of the three-dimensional water vapour field during these transitions from predominantly northerly Mistral/Tramontane flow to a predominantly southerly flow, allowing to identify the quite sharp separation between these flows, which is also quite well captured by the mesoscale models.

  5. Strategic wind power trading considering rival wind power production

    DEFF Research Database (Denmark)

    Exizidis, Lazaros; Kazempour, Jalal; Pinson, Pierre

    2016-01-01

    In an electricity market with high share of wind power, it is expected that wind power producers may exercise market power. However, wind producers have to cope with wind’s uncertain nature in order to optimally offer their generation, whereas in a market with more than one wind producers......, uncertainty of rival wind power generation should also be considered. Under this context, this paper addresses the impact of rival wind producers on the offering strategy and profits of a pricemaker wind producer. A stochastic day-ahead market setup is considered, which optimizes the day-ahead schedules...... considering a number of foreseen real-time scenarios. The results indicate that strategic wind producer is more likely to exercise market power having a mid-mean or low-mean forecast distribution, rather than having a high-mean one. Furthermore, it is observed that its offering strategy varies considerably...

  6. Wakes in large offshore wind farms

    DEFF Research Database (Denmark)

    Berthelmie, Rebecca J.; Frandsen, Sten Tronæs; Rathmann, Ole

    2008-01-01

    Power losses due to wind turbine wakes are of the order of 10 and 20% of total power output in large wind farms. The focus of this research carried out within the EC funded UPWIND project is wind speed and turbulence modelling for large wind farms/wind turbines in complex terrain and offshore...... is for five turbines in flat terrain. Finally a complex terrain wind farm will be modelled and compared with observations. For offshore wind farms, the focus is on cases at the Horns Rev wind farm which indicate wind farm models require modification to reduce under-prediction of wake losses while CFD models...... in order to optimise wind farm layouts to reduce wake losses and loads. For complex terrain, a set of three evaluations is underway. The first is a model comparison for a Gaussian Hill where CFD models and wind farm models are being compared for the case of one hilltop wind turbine. The next case...

  7. MHD-kinetic Modeling of the Solar wind Interaction with the Local Interstellar Medium: Can Steady State Models Explain Voyager Observations?

    Science.gov (United States)

    Redman, A. C.; Pogorelov, N. V.; Heerikhuisen, J.; Kim, T. K.

    2016-12-01

    Because of the Voyager interstellar mission, solar wind (SW) interaction with the local interstellar medium (LISM) represents a natural laboratory for the investigation of colliding streams of partially ionized plasma. It has been known for a long time that charge exchange between ions and neutral H atoms plays a major role in this interaction. Since the mean free path of charge exchange may be as large as 50 AU, kinetic treatment of the neutral atom transport becomes an important ingredient of any SW-LISM interaction model. We use an MHD-kinetic model implemented in our in-house Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) to analyze the plasma and magnetic field distributions in the heliosphere and in the LISM beyond it. Simulations are performed using an adaptive mesh refinement technique for a set of the LISM parameters that are believed to be the best choice from the viewpoint of fitting measurement from different data sets. To specify the SW parameters, we used OMNI data averaged over an approximately 5-year period from 2010 to 2015. While this model does not include time-dependence of the SW, it allows us to make analyze the dependence of the velocity distribution at Voyager 2 and magnetic field in the LISM at Voyager 1 and arrive at important conclusions regarding the possibility of reproducing measurements with steady-state models. In particular, it is shown that the transverse velocity component at V2 is not reproduced well for any set of LISM properties. On the other hand, the boundary conditions with the magnetic field strength of about 3 microG are in agreement with Voyager 1 observations. We also demonstrate that the heliospheric magnetic field calculated in the inner heliosheath assuming a unipolar field substantially overestimates Voyager observations. This means that there should exist some mechanism to dissipate magnetic field immediately behind the termination shock.

  8. A Database of Interplanetary and Interstellar Dust Detected by the Wind Spacecraft

    Science.gov (United States)

    Malaspina, David M.; Wilson, Lynn B., III

    2016-01-01

    It was recently discovered that the WAVES instrument on the Wind spacecraft has been detecting, in situ, interplanetary and interstellar dust of approximately 1 micron radius for the past 22 years. These data have the potential to enable advances in the study of cosmic dust and dust-plasma coupling within the heliosphere due to several unique properties: the Wind dust database spans two full solar cycles; it contains over 107,000 dust detections; it contains information about dust grain direction of motion; it contains data exclusively from the space environment within 350 Earth radii of Earth; and it overlaps by 12 years with the Ulysses dust database. Further, changes to the WAVES antenna response and the plasma environment traversed by Wind over the lifetime of the Wind mission create an opportunity for these data to inform investigations of the physics governing the coupling of dust impacts on spacecraft surfaces to electric field antennas. A Wind dust database has been created to make the Wind dust data easily accessible to the heliophysics community and other researchers. This work describes the motivation, methodology, contents, and accessibility of the Wind dust database.

  9. Ionization and NO production in the polar mesosphere during high-speed solar wind streams. Model validation and comparison with NO enhancements observed by Odin-SMR

    Energy Technology Data Exchange (ETDEWEB)

    Kirkwood, S.; Belova, E. [Swedish Institute of Space Physics, Kiruna (Sweden). Polar Atmospheric Research; Osepian, A. [Polar Geophysical Institute, Murmansk (Russian Federation); Urban, J.; Perot, K. [Chalmers Univ. of Technology, Gothenburg (Sweden). Dept. of Radio and Space Science; Sinha, A.K. [Indian Institute of Geomagnetism, Navi Mumbai (India)

    2015-09-01

    Precipitation of high-energy electrons (EEP) into the polar middle atmosphere is a potential source of significant production of odd nitrogen, which may play a role in stratospheric ozone destruction and in perturbing large-scale atmospheric circulation patterns. High-speed streams of solar wind (HSS) are a major source of energization and precipitation of electrons from the Earth's radiation belts, but it remains to be determined whether these electrons make a significant contribution to the odd-nitrogen budget in the middle atmosphere when compared to production by solar protons or by lower-energy (auroral) electrons at higher altitudes, with subsequent downward transport. Satellite observations of EEP are available, but their accuracy is not well established. Studies of the ionization of the atmosphere in response to EEP, in terms of cosmic-noise absorption (CNA), have indicated an unexplained seasonal variation in HSS-related effects and have suggested possible order-of-magnitude underestimates of the EEP fluxes by the satellite observations in some circumstances. Here we use a model of ionization by EEP coupled with an ion chemistry model to show that published average EEP fluxes, during HSS events, from satellite measurements (Meredith et al., 2011), are fully consistent with the published average CNA response (Kavanagh et al., 2012). The seasonal variation of CNA response can be explained by ion chemistry with no need for any seasonal variation in EEP. Average EEP fluxes are used to estimate production rate profiles of nitric oxide between 60 and 100 km heights over Antarctica for a series of unusually well separated HSS events in austral winter 2010. These are compared to observations of changes in nitric oxide during the events, made by the sub-millimetre microwave radiometer on the Odin spacecraft. The observations show strong increases of nitric oxide amounts between 75 and 90 km heights, at all latitudes poleward of 60 S, about 10 days after the

  10. Sensing the wind profile

    Energy Technology Data Exchange (ETDEWEB)

    Pena, A.

    2009-03-15

    This thesis consists of two parts. The first is a synopsis of the theoretical progress of the study that is based on a number of journal papers. The papers, which constitute the second part of the report, aim to analyze, measure, and model the wind prole in and beyond the surface layer by combining observations from cup anemometers with lidars. The lidar is necessary to extend the measurements on masts at the Horns Rev offshore wind farm and over at land at Hoevsoere, Denmark. Both sensing techniques show a high degree of agreement for wind speed measurements performed at either sites. The wind speed measurements are averaged for several stability conditions and compare well with the surface-layer wind profile. At Hoevsoere, it is sufficient to scale the wind speed with the surface friction velocity, whereas at Horns Rev a new scaling is added, due to the variant roughness length. This new scaling is coupled to wind prole models derived for flow over the sea and tested against the wind proles up to 160 m at Horns Rev. The models, which account for the boundary-layer height in stable conditions, show better agreement with the measurements than compared to the traditional theory. Mixing-length parameterizations for the neutral wind prole compare well with length-scale measurements up to 300 m at Hoevsoere and 950 m at Leipzig. The mixing-length-derived wind proles strongly deviate from the logarithmic wind prole, but agree better with the wind speed measurements. The length-scale measurements are compared to the length scale derived from a spectral analysis performed up to 160 m at Hoevsoere showing high agreement. Mixing-length parameterizations are corrected to account for stability and used to derive wind prole models. These compared better to wind speed measurements up to 300 m at Hoevsoere than the surface-layer wind prole. The boundary-layer height is derived in nearneutral and stable conditions based on turbulent momentum uxes only and in unstable conditions

  11. Late-Time Evolution of Composite Supernova Remnants: Deep Chandra Observations and Hydrodynamical Modeling of a Crushed Pulsar Wind Nebula in SNR G327.1-1.1

    Science.gov (United States)

    Temim, Tea; Slane, Patrick; Kolb, Christopher; Blondin, John; Hughes, John P.; Bucciantini, Niccolo

    2015-01-01

    In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 ks Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology; a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock(RS) that can occur as a result of a density gradient in the ambient medium and or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a approx. 17,000 yr old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar's motion. We also show that the RSPWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to gamma-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.

  12. LATE-TIME EVOLUTION OF COMPOSITE SUPERNOVA REMNANTS: DEEP CHANDRA OBSERVATIONS AND HYDRODYNAMICAL MODELING OF A CRUSHED PULSAR WIND NEBULA IN SNR G327.1-1.1

    Energy Technology Data Exchange (ETDEWEB)

    Temim, Tea [Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Slane, Patrick [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Kolb, Christopher; Blondin, John [North Carolina State University, 421 Riddick Hall, Raleigh, NC 27695 (United States); Hughes, John P. [Rutgers University, 57 US Highway 1, New Brunswick, NJ 08901 (United States); Bucciantini, Niccoló [INAF Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi, 5, 50125, Firenze Italy (Italy)

    2015-07-20

    In an effort to better understand the evolution of composite supernova remnants (SNRs) and the eventual fate of relativistic particles injected by their pulsars, we present a multifaceted investigation of the interaction between a pulsar wind nebula (PWN) and its host SNR G327.1-1.1. Our 350 Chandra X-ray observations of SNR G327.1-1.1 reveal a highly complex morphology: a cometary structure resembling a bow shock, prong-like features extending into large arcs in the SNR interior, and thermal emission from the SNR shell. Spectral analysis of the non-thermal emission offers clues about the origin of the PWN structures, while enhanced abundances in the PWN region provide evidence for a mixing of supernova ejecta with PWN material. The overall morphology and spectral properties of the SNR suggest that the PWN has undergone an asymmetric interaction with the SNR reverse shock (RS), whichcan occur as a result of a density gradient in the ambient medium and/or a moving pulsar that displaces the PWN from the center of the remnant. We present hydrodynamical simulations of G327.1-1.1 that show that its morphology and evolution can be described by a ∼17,000-year-old composite SNR that expanded into a density gradient with an orientation perpendicular to the pulsar’s motion. We also show that the RS/PWN interaction scenario can reproduce the broadband spectrum of the PWN from radio to γ-ray wavelengths. The analysis and modeling presented in this work have important implications for our general understanding of the structure and evolution of composite SNRs.

  13. Observation of summer daytime aurora in the noctilucent cloud layer and its link to high-energy particle precipitation during high-speed solar wind streams

    Science.gov (United States)

    Lee, Y.; Kwak, Y. S.; Kim, K. C.; Solheim, B.; Park, J.

    2015-12-01

    Aurora produced by precipitating low-energy electrons can be suppressed in summer daytime. However, the high-energy electrons (>30 keV) that are unsuppressed by sunlight are capable of penetrating deep into the mesosphere, where they can produce the odd hydrogen (HOx) and eventually lead to catalytic ozone (O3) loss. By elevating the D-region ionization level, they also play the important role of facilitating the production of polar mesospheric summer echoes (PMSE) as a precursor of polar mesospheric clouds (PMC). In the present study, it was discovered that high-energy electrons induce supersonic luminous phenomena, including the enhancement of O(1S) 557.7-nm emission with an intensity of up to 300 kR (horizontally integrated) and a supersonic velocity (300-1500 m s-1) as seen within a field of view that is 150-km wide, also called a supersonic burst (SB). SB-accompanied O(1S) emission enhancement is differentiated from aurora because the former occurs only in summer daytime, at a low altitude of ~80 km, and in the form of an intense localised burst. The source of the SB energy might be linked to the precipitation of high-energy electrons (>30 keV), especially as observed during high-speed solar wind streams (HSSs). In producing O(1S) emission, the secondary electron number flux of the precipitated primary electrons increases in magnitude by as much as an order of four, and a local process is required to provide the supplement. The supplementary local process may involve a supersonic velocity possibly caused by ion acceleration in a strong electric field, resulting in the inducement of electron acceleration in the field.

  14. Wind farm production estimates

    DEFF Research Database (Denmark)

    Larsen, Torben J.; Larsen, Gunner Chr.; Aagaard Madsen, Helge

    2012-01-01

    the DWMmodel is to model the in- stationary wind farm flow characteristics by considering wind turbine wakes as passive tracers continuously emitted from the wind farm turbines each with a downstream transport pro- cess dictated by large scale turbulent eddies (lateral and ver- tical transportation; i......]. A very satisfactory agreement between experimental data and predictions is observed. This paper finally includes additionally an analysis of the production impact caused by atmospheric stability effects. For this study, atmospheric stability conditions are defined in terms of the Monin-Obukhov length....... Three different stability classes, including stable, neutral and unstable atmospheric stratification, have been investigated....

  15. Offshore wind resources at Danish measurement sites

    Energy Technology Data Exchange (ETDEWEB)

    Barthelmie, R.J.; Courtney, M.S.; Lange, B.; Nielsen, M.; Sempreviva, A.M. [Risoe National Lab., Dept. of Wind Energy and Atmospheric Physics, Roskilde (Denmark); Svenson, J.; Olsen, F. [SEAS, Haslev (Denmark); Christensen, T. [Elsamprojekt, Fredericia (Denmark)

    1999-03-01

    In order to characterise wind and turbulence characteristics at prospective offshore wind energy sites, meteorological observations from a number of purpose-built offshore monitoring sites have been analyzed and compared with long wind speed time series. New analyses have been conducted on the data sets focussing on meteorology, turbulence, extreme winds and wind and wave interactions. Relationships between wind speed, turbulence and fetch are highly complex. Minimum turbulence intensity offshore is associated with wind speeds of about 12 m/s. At lower wind speeds, stability effects are important while at higher winds speeds wind and wave interactions appear to dominate. On average, turbulence intensity offshore at 48 m height is approximately 0.08 if no coastal effects are present. However, the effect of the coastal discontinuity persists in wind speed and turbulence characteristics for considerable distances offshore. The majority of the adjustment of appears to occur within 20 km of the coast. (au)

  16. Wind Energy Conversion Systems Technology and Trends

    CERN Document Server

    2012-01-01

    Wind Energy Conversion System covers the technological progress of wind energy conversion systems, along with potential future trends. It includes recently developed wind energy conversion systems such as multi-converter operation of variable-speed wind generators, lightning protection schemes, voltage flicker mitigation and prediction schemes for advanced control of wind generators. Modeling and control strategies of variable speed wind generators are discussed, together with the frequency converter topologies suitable for grid integration. Wind Energy Conversion System also describes offshore farm technologies including multi-terminal topology and space-based wind observation schemes, as well as both AC and DC based wind farm topologies. The stability and reliability of wind farms are discussed, and grid integration issues are examined in the context of the most recent industry guidelines. Wind power smoothing, one of the big challenges for transmission system operators, is a particular focus. Fault ride th...

  17. Wind turbulence characterization for wind energy development

    Energy Technology Data Exchange (ETDEWEB)

    Wendell, L.L.; Gower, G.L.; Morris, V.R.; Tomich, S.D.

    1991-09-01

    As part of its support of the US Department of Energy's (DOE's) Federal Wind Energy Program, the Pacific Northwest Laboratory (PNL) has initiated an effort to work jointly with the wind energy community to characterize wind turbulence in a variety of complex terrains at existing or potential sites of wind turbine installation. Five turbulence characterization systems were assembled and installed at four sites in the Tehachapi Pass in California, and one in the Green Mountains near Manchester, Vermont. Data processing and analyses techniques were developed to allow observational analyses of the turbulent structure; this analysis complements the more traditional statistical and spectral analyses. Preliminary results of the observational analyses, in the rotating framework or a wind turbine blade, show that the turbulence at a site can have two major components: (1) engulfing eddies larger than the rotor, and (2) fluctuating shear due to eddies smaller than the rotor disk. Comparison of the time series depicting these quantities at two sites showed that the turbulence intensity (the commonly used descriptor of turbulence) did not adequately characterize the turbulence at these sites. 9 refs., 10 figs.,

  18. Interplanetary Fast Shocks and Associated Drivers Observed through the Twenty-Third Solar Minimum by WIND Over its First 2.5 Years

    Science.gov (United States)

    Mariani, F.; Berdichevsky, D.; Szabo, A.; Lepping, R. P.; Vinas, A. F.

    1999-01-01

    A list of the interplanetary (IP) shocks observed by WIND from its launch (in November 1994) to May 1997 is presented. Forty two shocks were identified. The magnetohydrodynamic nature of the shocks is investigated, and the associated shock parameters and their uncertainties are accurately computed using a practical scheme which combines two techniques. These techniques are a combination of the "pre-averaged" magnetic-coplanarity, velocity-coplanarity, and the Abraham-Schrauner-mixed methods, on the one hand, and the Vinas and Scudder [1986] technique for solving the non-linear least-squares Rankine-Hugoniot shock equations, on the other. Within acceptable limits these two techniques generally gave the same results, with some exceptions. The reasons for the exceptions are discussed. It is found that the mean strength and rate of occurrence of the shocks appears to correlated with the solar cycle. Both showed a decrease in 1996 coincident with the time of the lowest ultraviolet solar radiance, indicative of solar minimum and start of solar cycle 23, which began around June 1996. Eighteen shocks appeared to be associated with corotating interaction regions (CIRs). The distribution of their shock normals showed a mean direction peaking in the ecliptic plane and with a longitude (phi(sub n)) in that plane between perpendicular to the Parker spiral and radial from the Sun. When grouped according to the sense of the direction of propagation of the shocks the mean azimuthal (longitude) angle in GSE coordinates was approximately 194 deg for the fast-forward and approximately 20 deg for the fast-reverse shocks. Another 16 shocks were determined to be driven by solar transients, including magnetic clouds. These shocks had a broader distribution of normal directions than those of the CIR cases with a mean direction close to the Sun-Earth line. Eight shocks of unknown origin had normal orientation well off the ecliptic plane. No shock propagated with longitude phi(sub n) >= 220

  19. Wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Yeoman, J.C. Jr.

    1978-12-01

    This evaluation of wind turbines is part of a series of Technology Evaluations of possible components and subsystems of community energy systems. Wind turbines, ranging in size from 200 W to 10 MW, are discussed as candidates for prime movers in community systems. Estimates of performance characteristics and cost as a function of rated capacity and rated wind speed are presented. Data concerning material requirements, environmental effects, and operating procedures also are given and are represented empirically to aid computer simulation.

  20. From local wind energy resource to national wind power production

    Directory of Open Access Journals (Sweden)

    Wolf-Gerrit Früh

    2015-02-01

    Full Text Available Wind power is one of the most established renewable power resources yet it is also one of the most volatile resources. This poses a key challenge for successfully integrating wind power at a large scale into the power grid. Here we present an analysis of the time scales associated with wind power from hourly to seasonal fluctuations and how combining spatially distributed wind power sources helps to reduce its volatility. The analysis, based on observed wind speeds, is then generalised in a simple statistical model to develop a tool which can estimate the power output profile from a particular consortium of wind power sources. As the estimator only uses the local, or the mean national, wind resource and the mean distance between the sites to estimate the joint power output profile, it can be used by developers to estimate the reliability of their joint power output and to form the most effective consortium.

  1. Christian de Perthuis, 2003, La génération future a-t-elle un avenir?, Paris , Editions Belin, collection Ulysse

    Directory of Open Access Journals (Sweden)

    Sandrine Rousseau

    2004-10-01

    Full Text Available L’auteur de cet ouvrage, professeur associé à l’Université Paris-Dauphine, dirige la veille stratégique du groupe Caisse des dépôts, et appartient au club Ulysse, fondé en 2000 et qui se présente comme «un lieu de discussion et de débats entre économistes et observateurs de la vie politique, économique et sociale. Désireux de passer au-delà des clivages traditionnels, ses membres ont pour objectif d’éclairer et d’enrichir les débats sur les grandes échéances électorales, en assurant une prése...

  2. Wind Energy

    Energy Technology Data Exchange (ETDEWEB)

    Ganley, Jason; Zhang, Jie; Hodge, Bri-Mathias

    2016-03-15

    Wind energy is a variable and uncertain renewable resource that has long been used to produce mechanical work, and has developed into a large producer of global electricity needs. As renewable sources of energy and feedstocks become more important globally to produce sustainable products, many different processes have started adopting wind power as an energy source. Many times this is through a conversion to hydrogen through electrolysis that allows for a more continuous process input. Other important pathways include methanol and ammonia. As the demand for sustainable products and production pathways increases, and wind power capital costs decrease, the role of wind power in chemical and energy production seems poised to increase significantly.

  3. Using wind tunnels to predict bird mortality in wind farms: the case of griffon vultures.

    Science.gov (United States)

    de Lucas, Manuela; Ferrer, Miguel; Janss, Guyonne F E

    2012-01-01

    Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topography and wind flows in relation to flight paths of griffon vultures, using a scaled model of the wind farm area in an aerodynamic wind tunnel, and test the difference between the observed flight paths of griffon vultures and the predominant wind flows. Different wind currents for each wind direction in the aerodynamic model were observed. Simulations of wind flows in a wind tunnel were compared with observed flight paths of griffon vultures. No statistical differences were detected between the observed flight trajectories of griffon vultures and the wind passages observed in our wind tunnel model. A significant correlation was found between dead vultures predicted proportion of vultures crossing those cells according to the aerodynamic model. Griffon vulture flight routes matched the predominant wind flows in the area (i.e. they followed the routes where less flight effort was needed). We suggest using these kinds of simulations to predict flight paths over complex terrains can inform the location of wind turbines and thereby reduce soaring bird mortality.

  4. Using wind tunnels to predict bird mortality in wind farms: the case of griffon vultures.

    Directory of Open Access Journals (Sweden)

    Manuela de Lucas

    Full Text Available BACKGROUND: Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. METHODOLOGY/PRINCIPAL FINDINGS: As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topography and wind flows in relation to flight paths of griffon vultures, using a scaled model of the wind farm area in an aerodynamic wind tunnel, and test the difference between the observed flight paths of griffon vultures and the predominant wind flows. Different wind currents for each wind direction in the aerodynamic model were observed. Simulations of wind flows in a wind tunnel were compared with observed flight paths of griffon vultures. No statistical differences were detected between the observed flight trajectories of griffon vultures and the wind passages observed in our wind tunnel model. A significant correlation was found between dead vultures predicted proportion of vultures crossing those cells according to the aerodynamic model. CONCLUSIONS: Griffon vulture flight routes matched the predominant wind flows in the area (i.e. they followed the routes where less flight effort was needed. We suggest using these kinds of simulations to predict flight paths over complex terrains can inform the location of wind turbines and thereby reduce soaring bird mortality.

  5. Long-Range WindScanner System

    DEFF Research Database (Denmark)

    Vasiljevic, Nikola; Lea, Guillaume; Courtney, Michael

    2016-01-01

    The technical aspects of a multi-Doppler LiDAR instrument, the long-range WindScanner system, are presented accompanied by an overview of the results from several field campaigns. The long-range WindScanner system consists of three spatially-separated, scanning coherent Doppler LiDARs and a remote......-rangeWindScanner system measures the wind field by emitting and directing three laser beams to intersect, and then scanning the beam intersection over a region of interest. The long-range WindScanner system was developed to tackle the need for high-quality observations of wind fields on scales of modern wind turbine...

  6. Wingbeat frequency and the body drag anomaly: Wind-tunnel observations on a thrush nightingale (Luscinia luscinia) and a teal (Anas crecca)

    NARCIS (Netherlands)

    Pennycuick, C.J.; Klaassen, M.R.J.; Kvist, A.; Lindstrom, A.

    1996-01-01

    A teal (Anas crecca) and a thrush nightingale (Luscinia luscinia) were trained to fly in the Lund wind tunnel for periods of up to 3 and 16 h respectively. Both birds flew in steady flapping flight, with such regularity that their wingbeat frequencies could be determined by viewing them through a

  7. Comparisons of Wind Speed Retrievals from an Airborne Microwave Radiometer (AMPR) with Satellite-Based Observations During the OLYMPEX/RADEX Field Campaign

    Science.gov (United States)

    Lang, Timothy J.; Biswas, Sayak

    2017-01-01

    AMPR is an airborne instrument that flew aboard the NASA ER-2 during the OLYMPEX/RADEX field campaign in late 2015. This poster's goal is to explore how well the instrument can retrieve near-surface wind speed over the ocean.

  8. NWP Forecast Errors of Boundary Layer Flow in Complex Terrain Observed During the Second Wind Forecast Improvement Project (WFIP2) Field Campaign.

    Science.gov (United States)

    Wilczak, James M.

    2017-04-01

    The Second Wind Forecast Improvement Project (WFIP2) is a U.S. Department of Energy and NOAA-led program whose goal is to improve the accuracy of NWP forecasts of wind speed in complex terrain for wind energy applications. WFIP2 includes a field campaign held in the vicinity of the Columbia River Basin in the Pacific Northwest of the U.S., which began in October 2015, and will continue through March, 2017. As part of WFIP2 a large suite of in-situ and remote sensing instrumentation has been deployed, including a network of three 449 MHz radar wind profilers (RWP's) with RASS, eight 915 MHz RWP's with RASS, 18 sodars, 4 profiling microwave radiometers, 5 scanning lidars, 5 profiling lidars, a network of 10 microbarographs, and many surface meteorological stations. Key NWP forecast models utilized for WFIP2 are the 13 km resolution Rapid Refresh (RAP), 3km High Resolution Rapid Refresh (HRRR), 0.75km HRRR-Nest, and the 12 km North American Mesoscale (NAM) forecast system. Preliminary results from WFIP2 will be presented, including seasonal variations of model forecast errors of wind speed, direction, temperature and humidity profiles and boundary layer depths; meteorological phenomena producing large forecast errors; and the relative skill of the various NWP forecasting systems. Diurnal time height cross-sections of the model's mean bias and RMSE are evaluated for each of the models, providing a holistic view of model accuracy at simulating boundary layer structure. Model errors are analyzed as a function of season (3 month averages) and location, and show the impact of increasing model resolution on forecast skill. Seasonal averages of model biases and RMSE provide more robust results than do shorter case study episodes, and can be used to verify that model errors found in shorter case study episodes are in fact representative. The results are used to identify specific model weaknesses and the corresponding parameterization schemes that are in greatest need of

  9. Comparison of SAR Wind Speed Retrieval Algorithms for Evaluating Offshore Wind Energy Resources

    DEFF Research Database (Denmark)

    Kozai, K.; Ohsawa, T.; Takeyama, Y.

    2010-01-01

    Envisat/ASAR-derived offshore wind speeds and energy densities based on 4 different SAR wind speed retrieval algorithms (CMOD4, CMOD-IFR2, CMOD5, CMOD5.N) are compared with observed wind speeds and energy densities for evaluating offshore wind energy resources. CMOD4 ignores effects of atmospheric...

  10. QuikSCAT and SSM/I ocean surface winds for wind energy

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Astrup, Poul; Nielsen, Per

    2007-01-01

    Ocean surface winds observed by satellite scatterometer (QuikSCAT) and passive microwave (SMM/I) provide valuable information for wind energy applications. In wind energy two long-term aspects on the offshore wind climate is of concern. One is the 20-year average necessary for the estimation...

  11. The winds of cataclysmic variables

    Energy Technology Data Exchange (ETDEWEB)

    Mauche, C.W. [Lawrence Livermore National Lab., CA (United States). Lab. for Experimental Astrophysics; Raymond, J.C. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (United States)

    1994-02-16

    The authors present an observational and theoretical review of the winds of cataclysmic variables (CVs). Specifically, they consider the related problems of the geometry and mass-loss rate of the winds of CVs, their ionization state and variability, and the results from studies of eclipsing CVs. Finally, they consider the properties of accretion disk wind models. Some of these models predict substantial angular momentum loss, which could affect both disk structure and binary evolution.

  12. Investigation of aerodynamic stability by wind response observation during cantilever construction of the Ikara Ohashi bridge; Ikara Ohashi haridashi sekoji no kaze kansoku ni yoru taifu anteisei no kento

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, K.; Mukai, H.; Takeda, T. [Kajima Corp., Tokyo (Japan)

    1995-12-20

    In order to ensure aerodynamic stability during cantilever construction of the Ikara Ohashi Bridge, wind response observation was carried out and discussions were given on the result. The Ikara Ohashi Bridge is a 5-span continuous PC cable-stayed bridge with the central span being a concrete bridge having a length of 260 m, which is the longest in Japan. The bridge was constructed using a method that main girders are extended from the central tower to the right and left sides while the girders are stayed by bracing cables. The bridge construction site is in an area which is often subjected to typhoons and gusts like seasonal winds in winter, hence a discussion on aerodynamic stability of the bridge especially during extension work was viewed as an important matter. In addition, the construction used two small-capacity cables spaced and bundled as the bracing material, which required verification on their aerodynamic stability. In order to identify vibration characteristics of the main girders and the central tower, wind response observation has been performed as soon as the construction was begun. As a result, the vibration characteristics of the main girders and the central tower were identified, and it was verified that vibration shape and dominant frequency can be evaluated properly by an intrinsic value analysis that uses a multi-material point frame model. Furthermore, effects of different vibration absorbing measures were compared, and the effective methods were adopted as the result. 4 refs., 12 figs.

  13. Sensing the wind profile

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo

    2009-01-01

    This thesis consists of two parts. The first is a synopsis of the theoretical progress of the study that is based on a number of journal papers. The papers, which constitute the second part of the report, aim to analyze, measure, and model the wind prole in and beyond the surface layer by combining...... observations from cup anemometers with lidars. The lidar is necessary to extend the measurements on masts at the Horns Rev offshore wind farm and over at land at Høvsøre, Denmark. Both sensing techniques show a high degree of agreement for wind speed measurements performed at either sites. The wind speed...... measurements are averaged for several stability conditions and compare well with the surface-layer wind profile. At Høvsøre, it is sufficient to scale the wind speed with the surface friction velocity, whereas at Horns Rev a new scaling is added, due to the variant roughness length. This new scaling is coupled...

  14. Assimilation of Typhoon Wind Field Retrieved from Scatterometer and SAR Based on the Huber Norm Quality Control

    National Research Council Canada - National Science Library

    Boheng Duan; Weimin Zhang; Xiaofeng Yang; Haijin Dai; Yi Yu

    2017-01-01

    Observations of sea surface wind field are critical for typhoon prediction. The scatterometer observation is one of the most important sources of sea surface winds, which provides both wind speed and wind direction information...

  15. World Wind

    Data.gov (United States)

    National Aeronautics and Space Administration — World Wind allows any user to zoom from satellite altitude into any place on Earth, leveraging high resolution LandSat imagery and SRTM elevation data to experience...

  16. Dune formation under bimodal winds.

    Science.gov (United States)

    Parteli, Eric J R; Durán, Orencio; Tsoar, Haim; Schwämmle, Veit; Herrmann, Hans J

    2009-12-29

    The study of dune morphology represents a valuable tool in the investigation of planetary wind systems--the primary factor controlling the dune shape is the wind directionality. However, our understanding of dune formation is still limited to the simplest situation of unidirectional winds: There is no model that solves the equations of sand transport under the most common situation of seasonally varying wind directions. Here we present the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction. Our calculations show that dunes align longitudinally to the resultant wind trend if the angle(w) between the wind directions is larger than 90 degrees. Under high sand availability, linear seif dunes are obtained, the intriguing meandering shape of which is found to be controlled by the dune height and by the time the wind lasts at each one of the two wind directions. Unusual dune shapes including the "wedge dunes" observed on Mars appear within a wide spectrum of bimodal dune morphologies under low sand availability.

  17. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Science.gov (United States)

    2013-05-20

    ...-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains Wind Power, LLC v. Xcel Energy...

  18. Calm winds

    Science.gov (United States)

    Ólafsson, Haraldur

    2017-04-01

    Knowledge of calm winds is of societal importance in connection with distribution pollution from natural sources (dust, volcanic gases and ash) as well as antropogenic sources. Time series from a multitude of automatic weather stations in Iceland have been explored and the climatology of calmness is established. This climatology underlines the importancec of not only abscence of large scale winds, but more importantly, the presence of surface inversions. Calmness is most frequent in summer, with secondary maxima in autumn and winter. The autumn calmness coincides with a period when frequency of synoptic scale cyclones does not increase, while the frequency of surface inversions increases rapidly. There is a very strong diurnal cycle in frequency of calm winds in the summer. The data indiates strongly that the nocturnal calmness is a result of a surface inversion, not the abscence of sea breeze. The frequency of calm winds is not only low at the coast, but also in the mountains, in spite of higher surface roughness away from the sea. The frequency of calm winds is much greater inside valleys and fjords than anywhere else. There are indications that open water in fjords has limited effect on the frequecy of calm winds along the fjord.

  19. Applicability of Synthetic Aperture Radar Wind Retrievals on Offshore Wind Resources Assessment in Hangzhou Bay, China

    DEFF Research Database (Denmark)

    Chang, Rui; Zhu, Rong; Badger, Merete

    2014-01-01

    ENVISAT advanced SAR (ASAR) for mapping wind resources with high spatial resolution. Around 181 collected pairs of wind data from SAR wind maps and from 13 meteorological stations in Hangzhou Bay are compared. The statistical results comparing in situ wind speed and SAR-based wind speed show a standard......In view of the high cost and sparse spatial resolution of offshore meteorological observations, ocean winds retrieved from satellites are valuable in offshore wind resource assessment as a supplement to in situ measurements. This study examines satellite synthetic aperture radar (SAR) images from...

  20. Wind-driven particle mobility on Mars: Insights from Mars Exploration Rover observations at "El Dorado" and surroundings at Gusev Crater

    Science.gov (United States)

    Sullivan, R.; Arvidson, R.; Bell, J.F.; Gellert, Ralf; Golombek, M.; Greeley, R.; Herkenhoff, K.; Johnson, J.; Thompson, S.; Whelley, P.; Wray, J.

    2008-01-01

    The ripple field known as 'El Dorado' was a unique stop on Spirit's traverse where dust-raising, active mafic sand ripples and larger inactive coarse-grained ripples interact, illuminating several long-standing issues of Martian dust mobility, sand mobility, and the origin of transverse aeolian ridges. Strong regional wind events endured by Spirit caused perceptible migration of ripple crests in deposits SSE of El Dorado, erasure of tracks in sandy areas, and changes to dust mantling the site. Localized thermal vortices swept across El Dorado, leaving paths of reduced dust but without perceptibly damaging nearly cohesionless sandy ripple crests. From orbit, winds responsible for frequently raising clay-sized dust into the atmosphere do not seem to significantly affect dunes composed of (more easily entrained) sand-sized particles, a long-standing paradox. This disparity between dust mobilization and sand mobilization on Mars is due largely to two factors: (1) dust occurs on the surface as fragile, low-density, sand-sized aggregates that are easily entrained and disrupted, compared with clay-sized air fall particles; and (2) induration of regolith is pervasive. Light-toned bed forms investigated at Gusev are coarse-grained ripples, an interpretation we propose for many of the smallest linear, light-toned bed forms of uncertain origin seen in high-resolution orbital images across Mars. On Earth, wind can organize bimodal or poorly sorted loose sediment into coarse-grained ripples. Coarse-grained ripples could be relatively common on Mars because development of durable, well-sorted sediments analogous to terrestrial aeolian quartz sand deposits is restricted by the lack of free quartz and limited hydraulic sediment processing. Copyright 2008 by the American Geophysical Union.

  1. Offshore winds mapped from satellite remote sensing

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay

    2014-01-01

    the uncertainty on the model results on the offshore wind resource, it is necessary to compare model results with observations. Observations from ground-based wind lidar and satellite remote sensing are the two main technologies that can provide new types of offshore wind data at relatively low cost....... The advantages of microwave satellite remote sensing are 1) horizontal spatial coverage, 2) long data archives and 3) high spatial detail both in the coastal zone and of far-field wind farm wake. Passive microwave ocean wind speed data are available since 1987 with up to 6 observations per day with near...

  2. Wind energy applications of synthetic aperture radar

    Energy Technology Data Exchange (ETDEWEB)

    Bruun Christiansen, M.

    2006-11-15

    Synthetic aperture radars (SAR), mounted on satellites or aircraft, have proven useful for ocean wind mapping. Wind speeds at the height 10 m may be retrieved from measurements of radar backscatter using empirical model functions. The resulting wind fields are valuable in offshore wind energy planning as a supplement to on site measurements, which are costly and sparse, and model wind fields, which are not fully validated. Two applications of SAR measurements in offshore wind energy planning are addressed here: the study of wind farm wake effects and the potential of using SAR winds in offshore wind resource assessment. Firstly, wind wakes behind two large offshore wind farms in Denmark Horns Rev and Nysted are identified. A region of reduced wind speed is found downstream of both wind farms from the SAR wind fields. The wake extent and magnitude depends on the wind speed, the atmospheric stability, and the fraction of turbines operating. Wind farm wake effects are detected up to 20 km downwind of the last turbine. This distance is longer than predicted by state-of-the art wake models. Wake losses are typically 10-20% near the wind farms. Secondly, the potential of using SAR wind maps in offshore wind resource assessment is investigated. The resource assessment is made through Weibull fitting to frequency observations of wind speed and requires at least 100 satellite observations per year for a given site of interest. Predictions of the energy density are very sensitive to the wind speed and the highest possible accuracy on SAR wind retrievals is therefore sought. A 1.1 m s{sup -1} deviation on the mean wind speed is found through comparison with mast measurements at Horns Rev. The accuracy on mean wind speeds and energy densities found from satellite measurements varies with different empirical model functions. Additional uncertainties are introduced by the infrequent satellite sampling at fixed times of the day. The accuracy on satellite based wind resource

  3. Contribution of the ULF wave activity to the global recovery of the outer radiation belt during the passage of a high-speed solar wind stream observed in September 2014

    Science.gov (United States)

    Dal Lago, A.; Da Silva, L. A.; Alves, L. R.; Dallaqua, R.; Marchezi, J.; Medeiros, C.; Souza, V. M. C. E. S.; Koga, D.; Jauer, P. R.; Vieira, L.; Rockenbach, M.; Mendes, O., Jr.; De Nardin, C. M.; Sibeck, D. G.

    2016-12-01

    The interaction of the solar wind with the Earth's magnetosphere can either increase or decrease the relativistic electron population in the outer radiation belt. In order to investigate the contribution of the ULF wave activity to the global recovery of the outer radiation belt relativistic electron population, we searched the Van Allen data for a period in which we can clearly distinguish the enhancement of the fluxes from the background. The complex solar wind structure observed from September 12-24, 2014, which resulted from the interaction of two coronal mass ejections (CMEs) and a high-speed stream, presented such a scenario. The CMEs are related to the dropout of the relativistic electron population followed by several days of low fluxes. The global recovery started during the passage of the high-speed stream that was associated with the occurrence of substorms that persisted for several days. Here we estimate the contribution of ULF wave-particle interactions to the enhancement of the relativistic electron fluxes. Our approach is based on estimates of the ULF wave radial diffusion coefficients employing two models: (a) an analytic expression presented by Ozeke et al. (2014); and (b) a simplified model based on the solar wind parameters. The preliminary results, uncertainties and future steps are discussed in details.

  4. 77 FR 29633 - Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC...

    Science.gov (United States)

    2012-05-18

    ... Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII, LLC, Alta Wind XIII, LLC, Alta Wind XIV, LLC, Alta Wind XV, LLC, Alta Windpower Development, LLC, TGP Development... 385.207, Alta Wind VII, LLC, Alta Wind IX, LLC, Alta Wind X, LLC, Alta Wind XI, LLC, Alta Wind XII...

  5. Small Wind Energy Systems

    DEFF Research Database (Denmark)

    Simoes, Marcelo; Farret, Felix Alberto; Blaabjerg, Frede

    2015-01-01

    devices, and a centralized distribution control. In order to establish a small wind energy system it is important to observe the following: (i) Attending the energy requirements of the actual or future consumers; (ii) Establishing civil liabilities in case of accidents and financial losses due to shortage...

  6. Superconducting Wind Turbine Generators

    DEFF Research Database (Denmark)

    Mijatovic, Nenad

    on the HTS field winding performance were examined and verified throughout a series of Locked Armature experiments. The interaction have been defined in the terms of two (direct and quadrature) axis machine theory (Park transformation), where significant reduction of ~ 20% was observed for the rated armature...

  7. A Changing Wind Collision

    Science.gov (United States)

    Nazé, Yaël; Koenigsberger, Gloria; Pittard, Julian M.; Parkin, Elliot Ross; Rauw, Gregor; Corcoran, Michael F.; Hillier, D. John

    2018-02-01

    We report on the first detection of a global change in the X-ray emitting properties of a wind–wind collision, thanks to XMM-Newton observations of the massive Small Magellenic Cloud (SMC) system HD 5980. While its light curve had remained unchanged between 2000 and 2005, the X-ray flux has now increased by a factor of ∼2.5, and slightly hardened. The new observations also extend the observational coverage over the entire orbit, pinpointing the light-curve shape. It has not varied much despite the large overall brightening, and a tight correlation of fluxes with orbital separation is found without any hysteresis effect. Moreover, the absence of eclipses and of absorption effects related to orientation suggests a large size for the X-ray emitting region. Simple analytical models of the wind–wind collision, considering the varying wind properties of the eruptive component in HD 5980, are able to reproduce the recent hardening and the flux-separation relationship, at least qualitatively, but they predict a hardening at apastron and little change in mean flux, contrary to observations. The brightness change could then possibly be related to a recently theorized phenomenon linked to the varying strength of thin-shell instabilities in shocked wind regions. Based on XMM-Newton and Chandra data.

  8. Modeling wind speed and wind power distributions in Rwanda

    Energy Technology Data Exchange (ETDEWEB)

    Safari, Bonfils [Department of Physics, National University of Rwanda, P.O. Box 117, Huye District, South Province (Rwanda)

    2011-02-15

    Utilization of wind energy as an alternative energy source may offer many environmental and economical advantages compared to fossil fuels based energy sources polluting the lower layer atmosphere. Wind energy as other forms of alternative energy may offer the promise of meeting energy demand in the direct, grid connected modes as well as stand alone and remote applications. Wind speed is the most significant parameter of the wind energy. Hence, an accurate determination of probability distribution of wind speed values is very important in estimating wind speed energy potential over a region. In the present study, parameters of five probability density distribution functions such as Weibull, Rayleigh, lognormal, normal and gamma were calculated in the light of long term hourly observed data at four meteorological stations in Rwanda for the period of the year with fairly useful wind energy potential (monthly hourly mean wind speed anti v{>=}2 m s{sup -1}). In order to select good fitting probability density distribution functions, graphical comparisons to the empirical distributions were made. In addition, RMSE and MBE have been computed for each distribution and magnitudes of errors were compared. Residuals of theoretical distributions were visually analyzed graphically. Finally, a selection of three good fitting distributions to the empirical distribution of wind speed measured data was performed with the aid of a {chi}{sup 2} goodness-of-fit test for each station. (author)

  9. Validation Campaigns for Sea Surface Wind and Wind Profile by Ground-Based Doppler Wind Lidar

    Science.gov (United States)

    Liu, Zhishen; Wu, Songhua; Song, Xiaoquan; Liu, Bingyi; Li, Zhigang

    2010-12-01

    According to the research frame of ESA-MOST DRAGON Cooperation Program (ID5291), Chinese partners from Ocean Remote Sensing Institute of Ocean University of China have carried out a serial of campaigns for ground-based lidar validations and atmospheric observations. ORSI/OUC Doppler wind lidar has been developed and deployed to accurately measure wind speed and direction over large areas in real time -- an application useful for ADM-Aeolus VAL/CAL, aviation safety, weather forecasting and sports. The sea surface wind campaigns were successfully accomplished at the Qingdao sailing competitions during the 29th Olympic Games. The lidar located at the seashore near the sailing field, and made a horizontal scan over the sea surface, making the wind measurement in real time and then uploading the data to the local meteorological station every 10 minutes. In addition to the sea surface wind campaigns, ORSI/OUC Doppler wind lidar was deployed on the wind profile observations for the China's Shenzhou 7 spacecraft landing zone weather campaigns in September 2008 in Inner Mongolia steppe. Wind profile was tracked by the mobile Doppler lidar system to help to predict the module's landing site. During above ground tests, validation lidar is tested to be able to provide an independent and credible measurement of radial wind speed, wind profile, 3D wind vector, aerosol- backscattering ratio, aerosol extinction coefficient, extinction-to-backscatter ratio in the atmospheric boundary layer and troposphere, sea surface wind vectors, which will be an independent and very effective validation tool for upcoming ADM-Aeolus project.

  10. Astrospheres and Solar-like Stellar Winds

    Directory of Open Access Journals (Sweden)

    Wood Brian E.

    2004-07-01

    Full Text Available Stellar analogs for the solar wind have proven to be frustratingly difficult to detect directly. However, these stellar winds can be studied indirectly by observing the interaction regions carved out by the collisions between these winds and the interstellar medium (ISM. These interaction regions are called "astrospheres", analogous to the "heliosphere" surrounding the Sun. The heliosphere and astrospheres contain a population of hydrogen heated by charge exchange processes that can produce enough H I Ly alpha absorption to be detectable in UV spectra of nearby stars from the Hubble Space Telescope (HST. The amount of astrospheric absorption is a diagnostic for the strength of the stellar wind, so these observations have provided the first measurements of solar-like stellar winds. Results from these stellar wind studies and their implications for our understanding of the solar wind are reviewed here. Of particular interest are results concerning the past history of the solar wind and its impact on planetary atmospheres.

  11. WIND TURBINES FOR WIND POWER INSTALLATIONS

    Directory of Open Access Journals (Sweden)

    Barladean A.S.

    2008-04-01

    Full Text Available The problem of wind turbine choice for wind power stations is examined in this paper. It is shown by comparison of parameters and characteristics of wind turbines, that for existing modes and speeds of wind in territory of Republic of Moldova it is necessary to use multi-blade small speed rotation wind turbines of fan class.

  12. XMM-Newton observations of the massive colliding wind binary and non-thermal radio emitter CygOB2#8A [O6If + O5.5III(f)

    Science.gov (United States)

    De Becker, M.; Rauw, G.; Sana, H.; Pollock, A. M. T.; Pittard, J. M.; Blomme, R.; Stevens, I. R.; van Loo, S.

    2006-09-01

    We report on the results of four XMM-Newton observations separated by about ten days from each other of CygOB2#8A [O6If + O5.5III(f)]. This massive colliding wind binary is a very bright X-ray emitter - one of the first X-ray emitting O-stars discovered by the Einstein satellite - as well as a confirmed non-thermal radio emitter whose binarity was discovered quite recently. The X-ray spectrum between 0.5 and 10.0keV is essentially thermal, and is best fitted with a three-component model with temperatures of about 3, 9 and 20MK. The X-ray luminosity corrected for the interstellar absorption is rather large, i.e. about 1034ergs-1. Compared to the `canonical' LX/Lbol ratio of O-type stars, CygOB2#8A was a factor of 19-28 overluminous in X-rays during our observations. The EPIC spectra did not reveal any evidence for the presence of a non-thermal contribution in X-rays. This is not unexpected considering that the simultaneous detections of non-thermal radiation in the radio and soft X-ray (below 10.0keV) domains is unlikely. Our data reveal a significant decrease in the X-ray flux from apastron to periastron with an amplitude of about 20 per cent. Combining our XMM-Newton results with those from previous ROSAT-PSPC and ASCA-SIS observations, we obtain a light curve suggesting a phase-locked X-ray variability. The maximum emission level occurs around phase 0.75, and the minimum is probably seen shortly after the periastron passage. Using hydrodynamic simulations of the wind-wind collision, we find a high X-ray emission level close to phase 0.75, and a minimum at periastron as well. The high X-ray luminosity, the strong phase-locked variability and the spectral shape of the X-ray emission of CygOB2#8A revealed by our investigation point undoubtedly to X-ray emission dominated by colliding winds. Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member states and the USA (NASA). E-mail: debecker

  13. Wind turbine

    Science.gov (United States)

    Cheney, Jr., Marvin C.

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  14. Dependence of the open-closed field line boundary in Saturn's ionosphere on both the IMF and solar wind dynamic pressure: comparison with the UV auroral oval observed by the HST

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2008-02-01

    Full Text Available We model the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004, and compare these with the auroral ovals observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope. The modelling employs the paraboloid model of Saturn's magnetospheric magnetic field, whose parameters are varied according to the observed values of both the solar wind dynamic pressure and the interplanetary magnetic field (IMF vector. It is shown that the open field area responds strongly to the IMF vector for both expanded and compressed magnetic models, corresponding to low and high dynamic pressure, respectively. It is also shown that the computed open field region agrees with the poleward boundary of the auroras as well as or better than those derived previously from a model in which only the variation of the IMF vector was taken into account. The results again support the hypothesis that the auroral oval at Saturn is associated with the open-closed field line boundary and hence with the solar wind interaction.

  15. Dependence of the open-closed field line boundary in Saturn's ionosphere on both the IMF and solar wind dynamic pressure: comparison with the UV auroral oval observed by the HST

    Directory of Open Access Journals (Sweden)

    E. S. Belenkaya

    2008-02-01

    Full Text Available We model the open magnetic field region in Saturn's southern polar ionosphere during two compression regions observed by the Cassini spacecraft upstream of Saturn in January 2004, and compare these with the auroral ovals observed simultaneously in ultraviolet images obtained by the Hubble Space Telescope. The modelling employs the paraboloid model of Saturn's magnetospheric magnetic field, whose parameters are varied according to the observed values of both the solar wind dynamic pressure and the interplanetary magnetic field (IMF vector. It is shown that the open field area responds strongly to the IMF vector for both expanded and compressed magnetic models, corresponding to low and high dynamic pressure, respectively. It is also shown that the computed open field region agrees with the poleward boundary of the auroras as well as or better than those derived previously from a model in which only the variation of the IMF vector was taken into account. The results again support the hypothesis that the auroral oval at Saturn is associated with the open-closed field line boundary and hence with the solar wind interaction.

  16. Turbulent character of wind energy.

    Science.gov (United States)

    Milan, Patrick; Wächter, Matthias; Peinke, Joachim

    2013-03-29

    Wind turbines generate electricity from turbulent wind. Large fluctuations, and, more importantly, frequent wind gusts cause a highly fluctuating electrical power feed into the grid. Such effects are the hallmark of high-frequency turbulence. Here we show evidence that it is the complex structure of turbulence that dominates the power output for one single wind turbine as well as for an entire wind farm. We illustrate the highly intermittent, peaked nature of wind power fed into the grid. Multifractal scaling is observed, as described initially by Kolmogorov's 1962 theory of turbulence. In parallel, we propose a stochastic model that converts wind speed signals into power output signals with appropriate multifractal statistics. As more and more wind turbines become integrated into our electric grids, a proper understanding of this intermittent power source must be worked out to ensure grid stability in future networks. Thus, our results stress the need for a profound understanding of the physics of turbulence and its impact on wind energy.

  17. Verification and Calibration of a Reduced Order Wind Farm Model by Wind Tunnel Experiments

    Science.gov (United States)

    Schreiber, J.; Nanos, E. M.; Campagnolo, F.; Bottasso, C. L.

    2017-05-01

    In this paper an adaptation of the FLORIS approach is considered that models the wind flow and power production within a wind farm. In preparation to the use of this model for wind farm control, this paper considers the problem of its calibration and validation with the use of experimental observations. The model parameters are first identified based on measurements performed on an isolated scaled wind turbine operated in a boundary layer wind tunnel in various wind-misalignment conditions. Next, the wind farm model is verified with results of experimental tests conducted on three interacting scaled wind turbines. Although some differences in the estimated absolute power are observed, the model appears to be capable of identifying with good accuracy the wind turbine misalignment angles that, by deflecting the wake, lead to maximum power for the investigated layouts.

  18. A new observational approach to investigate the heliospheric interstellar wind interface - The study of extreme and far ultraviolet resonantly scattered solar radiation from neon, oxygen, carbon and nitrogen

    Science.gov (United States)

    Bowyer, Stuart; Fahr, Hans J.

    1990-01-01

    One of the outstanding uncertainties in the understanding of the heliosphere concerns the character of the interaction between the outflowing solar wind and the interstellar medium. A new possibility for obtaining information on this topic is suggested. The cosmically abundant elements neon, oxygen, carbon, and nitrogen will be affected differently at their interface passage depending upon the character of this region. Consequently, the distribution of these atoms and their ions will vary within the inner heliosphere. The study of resonantly scattered solar radiation from these species will then provide information on the nature of the interface. A preliminary evaluation of this approach has been carried out, and the results are encouraging. The relevant lines to be studied are in the extreme and far ulraviolet. The existing data in these bands are reviewed; unfortunately, past instrumentation has had insufficient resolution and sensitivity to provide useful information. The capabilities of future approved missions with capabilities in this area are evaluated.

  19. Wind turbine noise diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Richarz, W. [Aerocoustics Engineering Ltd., Toronto, ON (Canada); Richarz, H.

    2009-07-01

    This presentation proposed a self-consistent model for broad-band noise emitted from modern wind turbines. The simple source model was consistent with the physics of sound generation and considered the unique features of wind turbines. Although the acoustics of wind turbines are similar to those of conventional propellers, the dimensions of wind turbines pose unique challenges in diagnosing noise emission. The general features of the sound field were deduced. Source motion and source directivity appear to be responsible for amplitude variations. The amplitude modulation is likely to make wind-turbine noise more audible, and may be partly responsible for annoyance that has been reported in the literature. Acoustic array data suggests that broad-band noise is emitted predominantly during the downward sweep of each rotor blade. Source motion and source directivity account for the observed pattern. Rotor-tower interaction effects are of lesser importance. Predicted amplitude modulation ranges from 1 dB to 6dB. 2 refs., 9 figs.

  20. Bringing satellite winds to hub-height

    DEFF Research Database (Denmark)

    Badger, Merete; Pena Diaz, Alfredo; Bredesen, Rolv Erlend

    2012-01-01

    Satellite observations of the ocean surface can provide detailed information about the spatial wind variability over large areas. This is very valuable for the mapping of wind resources offshore where other measurements are costly and sparse. Satellite sensors operating at microwave frequencies...... measure the amount of radar backscatter from the sea surface, which is a function of the instant wind speed, wind direction, and satellite viewing geometry. A major limitation related to wind retrievals from satellite observations is that existing empirical model functions relate the radar backscatter...

  1. Remote Sensing Wind and Wind Shear System.

    Science.gov (United States)

    Contents: Remote sensing of wind shear and the theory and development of acoustic doppler; Wind studies; A comparison of methods for the remote detection of winds in the airport environment; Acoustic doppler system development; System calibration; Airport operational tests.

  2. On the Escarpment Wind Profile

    DEFF Research Database (Denmark)

    Jensen, Niels Otto; Peterson, E. W.

    1978-01-01

    It is shown that miscellaneous theories for flow over low ridges give results consistent with each other and that these results can be used to quantify certain observed features of the wind profile downwind from an escarpment......It is shown that miscellaneous theories for flow over low ridges give results consistent with each other and that these results can be used to quantify certain observed features of the wind profile downwind from an escarpment...

  3. Wind Energy Japan

    Energy Technology Data Exchange (ETDEWEB)

    Komatsubara, Kazuyo [Embassy of the Kingdom of the Netherlands, Tokyo (Japan)

    2012-06-15

    An overview is given of wind energy in Japan: Background; Wind Energy in Japan; Japanese Wind Energy Industry; Government Supports; Useful Links; Major Japanese Companies; Profiles of Major Japanese Companies; Major Wind Energy Projects in Japan.

  4. Database on wind characteristics - Analyses of wind turbine design loads

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, G.C.; Hansen, K.S.

    2004-06-01

    The main objective of IEA R and D Wind Annex XVII - Database on Wind Characteristics - has been to provide wind energy planners, designers and researchers, as well as the international wind engineering community in general, with a source of actual wind field data (time series and resource data) observed in a wide range of different wind climates and terrain types. Connected to an extension of the initial Annex period, the scope for the continuation was widened to include also support to the international wind turbine standardisation efforts.. The project partners are Sweden, Norway, U.S.A., The Netherlands and Denmark, with Denmark as the Operating Agent. The reporting of the continuation of Annex XVII falls in two separate parts. Part one accounts in details for the available data in the established database bank, and part two describes various data analyses performed with the overall purpose of improving the design load cases with relevance for to wind turbine structures. The present report constitutes the second part of the Annex XVII reporting. Both fatigue and extreme load aspects are dealt with, however, with the main emphasis on the latter. The work has been supported by The Ministry of Environment and Energy, Danish Energy Agency, The Netherlands Agency for Energy and the Environment (NOVEM), The Norwegian Water Resources and Energy Administration (NVE), The Swedish National Energy Administration (STEM) and The Government of the United States of America. (au)

  5. Flatback airfoil wind tunnel experiment.

    Energy Technology Data Exchange (ETDEWEB)

    Mayda, Edward A. (University of California, Davis, CA); van Dam, C.P. (University of California, Davis, CA); Chao, David D. (University of California, Davis, CA); Berg, Dale E.

    2008-04-01

    A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

  6. Using Satellite SAR to Characterize the Wind Flow around Offshore Wind Farms

    Directory of Open Access Journals (Sweden)

    Charlotte Bay Hasager

    2015-06-01

    Full Text Available Offshore wind farm cluster effects between neighboring wind farms increase rapidly with the large-scale deployment of offshore wind turbines. The wind farm wakes observed from Synthetic Aperture Radar (SAR are sometimes visible and atmospheric and wake models are here shown to convincingly reproduce the observed very long wind farm wakes. The present study mainly focuses on wind farm wake climatology based on Envisat ASAR. The available SAR data archive covering the large offshore wind farms at Horns Rev has been used for geo-located wind farm wake studies. However, the results are difficult to interpret due to mainly three issues: the limited number of samples per wind directional sector, the coastal wind speed gradient, and oceanic bathymetry effects in the SAR retrievals. A new methodology is developed and presented. This method overcomes effectively the first issue and in most cases, but not always, the second. In the new method all wind field maps are rotated such that the wind is always coming from the same relative direction. By applying the new method to the SAR wind maps, mesoscale and microscale model wake aggregated wind-fields results are compared. The SAR-based findings strongly support the model results at Horns Rev 1.

  7. A nonlinear dynamics approach for incorporating wind-speed patterns into wind-power project evaluation.

    Science.gov (United States)

    Huffaker, Ray; Bittelli, Marco

    2015-01-01

    Wind-energy production may be expanded beyond regions with high-average wind speeds (such as the Midwest U.S.A.) to sites with lower-average speeds (such as the Southeast U.S.A.) by locating favorable regional matches between natural wind-speed and energy-demand patterns. A critical component of wind-power evaluation is to incorporate wind-speed dynamics reflecting documented diurnal and seasonal behavioral patterns. Conventional probabilistic approaches remove patterns from wind-speed data. These patterns must be restored synthetically before they can be matched with energy-demand patterns. How to accurately restore wind-speed patterns is a vexing problem spurring an expanding line of papers. We propose a paradigm shift in wind power evaluation that employs signal-detection and nonlinear-dynamics techniques to empirically diagnose whether synthetic pattern restoration can be avoided altogether. If the complex behavior of observed wind-speed records is due to nonlinear, low-dimensional, and deterministic system dynamics, then nonlinear dynamics techniques can reconstruct wind-speed dynamics from observed wind-speed data without recourse to conventional probabilistic approaches. In the first study of its kind, we test a nonlinear dynamics approach in an application to Sugarland Wind-the first utility-scale wind project proposed in Florida, USA. We find empirical evidence of a low-dimensional and nonlinear wind-speed attractor characterized by strong temporal patterns that match up well with regular daily and seasonal electricity demand patterns.

  8. Quantifying offshore wind resources from satellite wind maps: Study area the North Sea

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Barthelmie, Rebecca Jane; Christiansen, Merete B.

    2006-01-01

    analysis and application program (WAsP). An estimate of the wind resource at the new project site at Horns Rev is given based on satellite SAR observations. The comparison of offshore satellite scatterometer winds, global model data and in situ data shows good agreement. Furthermore, the wake effect......Offshore wind resources are quantified from satellite synthetic aperture radar (SAR) and satellite scatterometer observations at local and regional scale respectively at the Horns Rev site in Denmark. The method for wind resource estimation from satellite observations interfaces with the wind atlas...

  9. ModObs: Atmospheric modelling for wind energy, climate and environment applications: exploring added value from new observation technique. Work in progress within a FP6 Marie Curie Research Training Network

    Science.gov (United States)

    Sempreviva, A. M.

    2009-09-01

    The EC FP6 Marie Curie Training Network "ModObs” http://www.modobs.windeng.net addresses the improvement of atmospheric boundary layer (ABL) models to investigate the interplay of processes at different temporal and spatial scales, and to explore the added value from new observation techniques. The overall goal is to bring young scientists to work ogether with experienced researchers in developing a better interaction amongst scientific communities of modelers and experimentalists, using a comprehensive approach to "Climate Change”, "Clean Energy assessment” and "Environmental Policies”, issues. This poster describes the work in progress of ten students, funded by the network, under the supervision of a team of scientists within atmospheric physics, engineering and satellite remote sensing and end-users such as companies in the private sector, all with the appropriate expertise to integrate the most advanced research methods and techniques in the following topics. MODELING: GLOBAL-TO-MESO SCALE: Analytical and process oriented numerical models will be used to study the interaction between the atmosphere and the ocean on a regional scale. Initial results indicate an interaction between the intensity of polar lows and the subsurface warm core often present in the Nordic Seas (11). The presence of waves, mainly swell, influence the MABL fluxes and turbulence structure. The regional and global wave effect on the atmosphere will be also studied and quantified (7) MESO-SCALE: Applicability of the planetary boundary layer (PBL) parametrizations in the meso-scale WRF model to marine atmospheric boundary layer (MABL) over the North Sea is investigated. The most suitable existing PBL parametrization will be additionally improved and used for downscaling North Sea past and future climates (2). Application of the meso-scale model (MM5 and WRF) for the wind energy in off-shore and coastal area. Set-up of the meso-scale model, post-processing and verification of the data

  10. Wind conditions for wind turbine design

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B.

    1999-04-01

    Delegates from Europe and USA attended the meeting and discussed general aspects of wind conditions for wind turbine design. The subjects and the presented papers covered a very broad range of aspects of wind conditions and related influence on the wind turbine. (EHS)

  11. Offshore wind mapping Mediterranean area using SAR

    DEFF Research Database (Denmark)

    Calaudi, Rosamaria; Arena, Felice; Badger, Merete

    2013-01-01

    Satellite observations of the ocean surface, for example from Synthetic Aperture Radars (SAR), provide information about the spatial wind variability over large areas. This is of special interest in the Mediterranean Sea, where spatial wind information is only provided by sparse buoys, often...... with long periods of missing data. Here, we focus on evaluating the use of SAR for offshore wind mapping. Preliminary results from the analysis of SAR-based ocean winds in Mediterranean areas show interesting large scale wind flow features consistent with results from previous studies using numerical models...

  12. Winds from disks in compact binaries

    Energy Technology Data Exchange (ETDEWEB)

    Mauche, C.W.

    1993-10-27

    We herein present an observational and theoretical review of the winds of compact binaries. After a brief consideration of the accretion disk coronae and winds of X-ray binaries, the review concentrates on the winds of cataclysmic variables (CVs). Specifically, we consider the related problems of the geometry and mass-loss rate of the winds of CVs, their ionization state and variability, and the results from studies of eclipsing CVs. Finally, the properties of bona fide accretion disk wind models are reviewed.

  13. Wind Technologies & Evolving Opportunities (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Robichaud, R.

    2014-07-01

    This presentation covers opportunities for wind technology; wind energy market trends; an overview of the National Wind Technology Center near Boulder, Colorado; wind energy price and cost trends; wind turbine technology improvements; and wind resource characterization improvements.

  14. Wind Statistics Offshore based on Satellite Images

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Mouche, Alexis; Badger, Merete

    2009-01-01

    -based observations become available. At present preliminary results are obtained using the routine methods. The first step in the process is to retrieve raw SAR data, calibrate the images and use a priori wind direction as input to the geophysical model function. From this process the wind speed maps are produced....... Results comparing satellite scatterometer winds to offshore meteorological observations have shown good results, and more comparisons are planned in this respect during the Norsewind project....

  15. Test application of a semi-objective approach to wind forecasting for wind energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Wegley, H.L.; Formica, W.J.

    1983-07-01

    The test application of the semi-objective (S-O) wind forecasting technique at three locations is described. The forecasting sites are described as well as site-specific forecasting procedures. Verification of the S-O wind forecasts is presented, and the observed verification results are interpreted. Comparisons are made between S-O wind forecasting accuracy and that of two previous forecasting efforts that used subjective wind forecasts and model output statistics. (LEW)

  16. Health impact of wind farms.

    Science.gov (United States)

    Kurpas, Donata; Mroczek, Bozena; Karakiewicz, Beata; Kassolik, Krzysztof; Andrzejewski, Waldemar

    2013-01-01

    analyses of these issues are justified, especially because none of the studies published in peer-reviewed journals so far meet the criteria for cohort or case-control studies. Due to methodology, currently available research results do not allow for higher than C-level recommendations. In the case of wind farms, the ideal types of research would be: a retrospective observation of a particular group of residents before and after the wind farm construction, case-control studies or cohort studies with control groups matched in respect of socioeconomic factors, predisposition for chronic diseases, exposure to environmental risk factors, and only one variable which would differentiate cases from controls--the distance between place of residence and a wind farm.

  17. Wind resource characterization in the Arabian Peninsula

    KAUST Repository

    Yip, Chak Man Andrew

    2015-12-28

    Wind energy is expected to contribute to alleviating the rise in energy demand in the Middle East that is driven by population growth and industrial development. However, variability and intermittency in the wind resource present significant challenges to grid integration of wind energy systems. These issues are rarely addressed in the literature of wind resource assessment in the Middle East due to sparse meteorological observations with varying record lengths. In this study, the wind field with consistent space–time resolution for over three decades at three hub heights (50m, 80m, 140m) over the whole Arabian Peninsula is constructed using the Modern Era Retrospective-Analysis for Research and Applications (MERRA) dataset. The wind resource is assessed at a higher spatial resolution with metrics of temporal variations in the wind than in prior studies. Previously unrecognized locations of interest with high wind abundance and low variability and intermittency have been identified in this study and confirmed by recent on-site observations. In particular, the western mountains of Saudi Arabia experience more abundant wind resource than most Red Sea coastal areas. The wind resource is more variable in coastal areas along the Arabian Gulf than their Red Sea counterparts at a similar latitude. Persistent wind is found along the coast of the Arabian Gulf.

  18. Wind Power Meteorology

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

    Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed......: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed...

  19. Seasonality in onshore normalized wind profiles above the surface layer

    DEFF Research Database (Denmark)

    Nissen, Jesper Nielsen; Gryning, Sven-Erik

    2010-01-01

    This work aims to study the seasonal difference in normalized wind speed above the surface layer as it is observed at the 160 m high mast at the coastal site Høvsøre at winds from the sea (westerly). Normalized and stability averaged wind speeds above the surface layer are observed to be 20 to 50...... is to reconstruct the seasonal signal in normalized wind speed and identify the physical process behind. The method proved reasonably successful in capturing the relative difference in wind speed between seasons, indicating that the simulated physical processes are likely candidates to the observed seasonal signal...... in normalized wind speed....

  20. Variability of wind direction statistics of mean and extreme wind events over the Baltic Sea region

    Directory of Open Access Journals (Sweden)

    Svenja E. Bierstedt

    2015-10-01

    Full Text Available It is not clear to what extent the variations of seasonal mean winds and seasonal extreme winds are related. We investigate this relationship for the Baltic Sea area by analysing two regional climate gridded data sets, coastDat2 and HiResAFF, for the periods 1948–2009 and 1850–2009, respectively. Both data sets are based on regional climate simulations incorporating information from observations with the aim of reproducing the observed trajectory of climate variables. We compare the wind direction distribution of mean and extreme wind events by analysing seasonal wind roses. Mean wind directions display a more isotropic distribution, with a seasonally varying maximum. Extreme winds are much more constrained to south-westerly and westerly directions. The co-variability in time between the wind speed along the dominant directions of seasonal mean and the seasonal extreme winds was investigated using a complex correlation coefficient. This coefficient enables the simultaneous investigation of the co-variability of two-dimensional variables, for example wind. This coefficient is small for all seasons, indicating a very weak co-variance in time between seasonal mean and seasonal extremes. Hence, deviations in the direction of the mean wind are not a good indicator for deviations in the direction of extreme winds. We also assess the spatial structure and temporal variability of mean and extreme wind statistics using a principal component analysis. The principal components exhibit no significant long-term trends over the simulation periods, although multidecadal trends are detected for some periods and seasons. In recent decades, wintertime mean and extremes shifted to a more south-westerly direction. In the other seasons, no trends in wind directions are detected. We also investigate the possibility that seasonal patterns of extreme winds might persist over several adjacent seasons. No such persistent patterns can be identified, and hence extreme

  1. Chandra observations of comet 2P/Encke 2003 : First detection of a collisionally thin, fast solar wind charge exchange system

    NARCIS (Netherlands)

    Lisse, CM; Christian, DJ; Dennerl, K; Wolk, SJ; Bodewits, Dennis; Hoekstra, Ronnie; Combi, MR; Makinen, T; Dryer, M; Fry, CD; Weaver, H

    2005-01-01

    We report the results of 15 hr of Chandra observations of comet 2P/Encke 2003 on November 24. X-ray emission from comet Encke was resolved on scales of 500-40,000 km, with unusual morphology due to the presence of a low-density, collisionally thin (to charge exchange) coma. A light curve with

  2. The Helium Abundance at Quiescent Current Sheets and the Slow Solar Wind

    Science.gov (United States)

    Suess, Steven T.; Ko, Y.-K.; VonSteiger, R.

    2008-01-01

    Ulysses MAG data were used to identify current sheets during sunspot minimum years of 1994-1997 and 2004-2006. The purpose of limiting the dates was to focus attention on 'quiescent current sheets' with as little influence from ICMEs as possible. SWOOPS data were then used in a superposed epoch analysis to study Helium abundance in the vicinity of the current sheet, similar to the study done by Borrini et al. (1981). That earlier study found a narrow (ca. 2 day) minimum in He/H around the current sheet that is extremely variable from one year to the next in the period 1971-1978. A similar result is found here for data at all latitudes and distances in 2004-2006. Conversely, data from 1994-1997 produce a deep minimum several times wider (ca. 10 days). The reason for this is found to be that low He/H is more closely associated with slow wind than the current sheet per se. There are thus apparently at least two sources of slow wind, one associated with very low He/H of 0-0.02 and one associated with moderate abundance of 0.03-0.05. The large variability is a consequence of the relatively small number of current sheet encounters around solar minimum and the random distribution of low He/H intervals, lasting less than 1 day to more than 7 days, throughout slow wind.

  3. Prospecting for Wind

    Science.gov (United States)

    Swapp, Andy; Schreuders, Paul; Reeve, Edward

    2011-01-01

    Many people use wind to help meet their needs. Over the years, people have been able to harness or capture the wind in many different ways. More recently, people have seen the rebirth of electricity-generating wind turbines. Thus, the age-old argument about technology being either good or bad can also be applied to the wind. The wind can be a…

  4. Careers in Wind Energy

    Science.gov (United States)

    Liming, Drew; Hamilton, James

    2011-01-01

    As a common form of renewable energy, wind power is generating more than just electricity. It is increasingly generating jobs for workers in many different occupations. Many workers are employed on wind farms: areas where groups of wind turbines produce electricity from wind power. Wind farms are frequently located in the midwestern, western, and…

  5. On hurricane parametric wind and applications in storm surge modeling

    Science.gov (United States)

    Lin, Ning; Chavas, Daniel

    2012-05-01

    This study revisits the parametric modeling of the hurricane surface wind field composed of the storm vortex and the environmental background flow. First, we investigate the parametric representation of the surface background wind by analyzing its empirical relationship with storm movement. A marked deceleration and counter-clockwise rotation of the surface background wind from the storm translation vector is detected, a result predicted by the Ekman theory but rarely applied in wind and surge modeling. Then, we examine the various parameters used to model the wind field and, through numerical simulations, quantify their induced uncertainties in the extreme wind and surge estimates at two coastal sites. Our analyses show that, over the range of accepted values and methods in the literature, the local wind and surge estimates are most sensitive to uncertainties in the surface wind reduction factor and storm wind profile but less sensitive to uncertainties in other wind parameters, such as inflow angle and surface background wind (varying in the observed range). The surge is more sensitive than the wind to uncertainties in the wind parameters, and these sensitivities are comparable to the sensitivity of the surge to the uncertainty in the sea surface drag coefficient. We also find that some commonly used wind parameters unsupported by theory or observations can induce significant errors in the wind and surge estimates. The results of this study provide new insights and references for future hurricane wind and surge analysis.

  6. 75 FR 23263 - Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC...

    Science.gov (United States)

    2010-05-03

    ... Energy Regulatory Commission Alta Wind I, LLC; Alta Wind II, LLC; Alta Wind III, LLC; Alta Wind IV, LLC; Alta Wind V, LLC; Alta Wind VI, LLC; Alta Wind VII, LLC; Alta Wind VIII, LLC; Alta Windpower... Federal Energy Regulatory Commission (Commission), 18 CFR 285.207 (2009), Alta Wind I, LLC, Alta Wind II...

  7. Forecasting wind power production from a wind farm using the RAMS model

    DEFF Research Database (Denmark)

    Tiriolo, L.; Torcasio, R. C.; Montesanti, S.

    2015-01-01

    The importance of wind power forecast is commonly recognized because it represents a useful tool for grid integration and facilitates the energy trading. This work considers an example of power forecast for a wind farm in the Apennines in Central Italy. The orography around the site is complex...... and the horizontal resolution of the wind forecast has an important role. To explore this point we compared the performance of two 48 h wind power forecasts using the winds predicted by the Regional Atmospheric Modeling System (RAMS) for the year 2011. The two forecasts differ only for the horizontal resolution...... of the ECMWF Integrated Forecasting System (IFS), whose horizontal resolution over Central Italy is about 25 km at the time considered in this paper. Because wind observations were not available for the site, the power curve for the whole wind farm was derived from the ECMWF wind operational analyses available...

  8. The influence of the Wind Speed Profile on Wind Turbine Performance Measurements

    DEFF Research Database (Denmark)

    Wagner, Rozenn; Antoniou, Ioannis; Pedersen, Søren M.

    2009-01-01

    . Assuming a certain turbine hub height, the profiles with hub-height wind speeds between 6 m s-1 and 8 m s-1 are normalized at 7 m s-1 and grouped to a number of mean shear profiles. The energy in the profiles varies considerably for the same hub-height wind speed. These profiles are then used as input......To identify the influence of wind shear and turbulence on wind turbine performance, flat terrain wind profiles are analysed up to a height of 160 m. The profiles' shapes are found to extend from no shear to high wind shear, and on many occasions, local maxima within the profiles are also observed...... to a Blade Element Momentum model that simulates the Siemens 3.6 MW wind turbine. The analysis is carried out as time series simulations where the electrical power is the primary characterization parameter. The results of the simulations indicate that wind speed measurements at different heights over...

  9. Hourly wind speed analysis in Sicily

    Energy Technology Data Exchange (ETDEWEB)

    Bivona, S.; Leone, C. [Palermo Univ., Dip di Fisica e Technologie Relative, Palermo (Italy); Burlon, R. [Palermo Univ., Dip. di Ingegnaria Nucleare, Palermo (Italy)

    2003-07-01

    The hourly average wind speed data recorded by CNMCA (Centro Nazionale di Meteorologia e Climatologia Aeronautica) have been used to study the statistical properties of the wind speed at nine locations on Sicily. By grouping the observations month by month, we show that the hourly average wind speed, with calms omitted, is represented by a Weibull function. The suitability of the distribution is judged by the discrepancies between the observed and calculated values of the monthly average wind speed and of the standard deviation. (Author)

  10. Satellite information for wind energy applications

    DEFF Research Database (Denmark)

    Nielsen, M.; Astrup, Poul; Hasager, Charlotte Bay

    2004-01-01

    An introduction to satellite information relevant for wind energy applications is given. It includes digital elevation model (DEM) data based on satellite observations. The Shuttle Radar Topography Mission (SRTM) is useful for regional scale wind resourcestudies. Comparison results from complex...... in WASP combined with topography and roughness information to assess the coastal wind power potential. Scatterometer wind data are observed ~ twice per day, whereas SAR only are obtained 3 to 8 timesmonthly. The relatively low number of samples and the absolute uncertainty within the maps, ~ 1.3 ms-1...

  11. Tower Winds - Cape Kennedy

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Digitized data taken from Wind Gust Charts. Record contains hourly wind directions and speed with a peak wind recorded at the end of each day. Sorted by: station,...

  12. The disk wind in the rapidly spinning stellar-mass black hole 4U 1630-472 observed with NuSTAR

    DEFF Research Database (Denmark)

    King, Ashley L.; Walton, Dominic J.; Miller, Jon M.

    2014-01-01

    We present an analysis of a short NuSTAR observation of the stellar-mass black hole and low-mass X-ray binary 4U 1630-472. Reflection from the inner accretion disk is clearly detected for the first time in this source, owing to the sensitivity of NuSTAR. With fits to the reflection spectrum, we...... find evidence for a rapidly spinning black hole, (1σ statistical errors). However, archival data show that the source has relatively low radio luminosity. Recently claimed relationships between jet power and black hole spin would predict either a lower spin or a higher peak radio luminosity. We also...

  13. Wind speed forecasting in the central California wind resource area

    Energy Technology Data Exchange (ETDEWEB)

    McCarthy, E.F. [Wind Economics & Technology, Inc., Martinez, CA (United States)

    1997-12-31

    A wind speed forecasting program was implemented in the summer seasons of 1985 - 87 in the Central California Wind Resource Area (WRA). The forecasting program is designed to use either meteorological observations from the WRA and local upper air observations or upper air observations alone to predict the daily average windspeed at two locations. Forecasts are made each morning at 6 AM and are valid for a 24 hour period. Ease of use is a hallmark of the program as the daily forecast can be made using data entered into a programmable HP calculator. The forecasting program was the first step in a process to examine whether the electrical energy output of an entire wind power generation facility or defined subsections of the same facility could be predicted up to 24 hours in advance. Analysis of the results of the summer season program using standard forecast verification techniques show the program has skill over persistence and climatology.

  14. Wind Farm Power Forecasting

    OpenAIRE

    Haouas, Nabiha; Bertrand, Pierre R.

    2013-01-01

    Forecasting annual wind power production is useful for the energy industry. Until recently, attention has only been paid to the mean annual wind power energy and statistical uncertainties on this forecasting. Recently, Bensoussan et al. (2012) have pointed that the annual wind power produced by one wind turbine is a Gaussian random variable under a reasonable set of assumptions. Moreover, they can derive both mean and quantiles of annual wind power produced by one wind ...

  15. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    OpenAIRE

    Ju Feng; Wen Zhong Shen

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data a...

  16. Superconducting Wind Turbine Generators

    OpenAIRE

    Yunying Pan; Danhzen Gu

    2016-01-01

    Wind energy is well known as a renewable energy because its clean and less polluted characteristic, which is the foundation of development modern wind electricity. To find more efficient wind turbine is the focus of scientists around the world. Compared from conventional wind turbines, superconducting wind turbine generators have advantages at zero resistance, smaller size and lighter weight. Superconducting wind turbine will inevitably become the main trends in this area. This paper intends ...

  17. Wind Power Today: Federal Wind Program Highlights

    Energy Technology Data Exchange (ETDEWEB)

    2005-04-01

    Wind Power Today is an annual publication that provides an overview of the wind research conducted under the U.S. Department of Energy's Wind and Hydropower Technologies Program. The purpose of Wind Power Today is to show how DOE supports wind turbine research and deployment in hopes of furthering the advancement of wind technologies that produce clean, low-cost, reliable energy. Content objectives include: educate readers about the advantages and potential for widespread deployment of wind energy; explain the program's objectives and goals; describe the program's accomplishments in research and application; examine the barriers to widespread deployment; describe the benefits of continued research and development; facilitate technology transfer; and attract cooperative wind energy projects with industry.

  18. Wind flow through shrouded wind turbines

    Science.gov (United States)

    2017-03-01

    THROUGH SHROUDED WIND TURBINES by Jonathan P. Scheuermann March 2017 Thesis Advisor: Muguru Chandrasekhara Second Reader: Kevin Jones THIS......CODE 13. ABSTRACT (maximum 200 words) Wall pressure distributions and cross section flow distribution on wind turbine shroud designs, determined

  19. Advanced structural wind engineering

    CERN Document Server

    Kareem, Ahsan

    2013-01-01

    This book serves as a textbook for advanced courses as it introduces state-of-the-art information and the latest research results on diverse problems in the structural wind engineering field. The topics include wind climates, design wind speed estimation, bluff body aerodynamics and applications, wind-induced building responses, wind, gust factor approach, wind loads on components and cladding, debris impacts, wind loading codes and standards, computational tools and computational fluid dynamics techniques, habitability to building vibrations, damping in buildings, and suppression of wind-induced vibrations. Graduate students and expert engineers will find the book especially interesting and relevant to their research and work.

  20. Wind energy bibliography

    Energy Technology Data Exchange (ETDEWEB)

    None

    1995-05-01

    This bibliography is designed to help the reader search for information on wind energy. The bibliography is intended to help several audiences, including engineers and scientists who may be unfamiliar with a particular aspect of wind energy, university researchers who are interested in this field, manufacturers who want to learn more about specific wind topics, and librarians who provide information to their clients. Topics covered range from the history of wind energy use to advanced wind turbine design. References for wind energy economics, the wind energy resource, and environmental and institutional issues related to wind energy are also included.

  1. Modelling pulsar wind nebulae

    CERN Document Server

    2017-01-01

    In view of the current and forthcoming observational data on pulsar wind nebulae, this book offers an assessment of the theoretical state of the art of modelling them. The expert authors also review the observational status of the field and provide an outlook for future developments. During the last few years, significant progress on the study of pulsar wind nebulae (PWNe) has been attained both from a theoretical and an observational perspective, perhaps focusing on the closest, more energetic, and best studied nebula: the Crab, which appears in the cover. Now, the number of TeV detected PWNe is similar to the number of characterized nebulae observed at other frequencies over decades of observations. And in just a few years, the Cherenkov Telescope Array will increase this number to several hundreds, actually providing an essentially complete account of TeV emitting PWNe in the Galaxy. At the other end of the multi-frequency spectrum, the SKA and its pathfinder instruments, will reveal thousands of new pulsa...

  2. Interactions in Massive Colliding Wind Binaries

    Directory of Open Access Journals (Sweden)

    Michael F. Corcoran

    2012-03-01

    Full Text Available There are observational difficulties determining dynamical masses of binary star components in the upper HR diagram both due to the scarcity of massive binary systems and spectral and photometric contamination produced by the strong wind outflows in these systems. We discuss how variable X-ray emission in these systems produced by wind-wind collisions in massive binaries can be used to constrain the system parameters, with application to two important massive binaries, Eta Carinae and WR 140.

  3. Origin of the Ubiquitous Fast Solar Wind

    Science.gov (United States)

    Habbal, S. R.; Woo, R.; Fineschi, S.; O'Neal, R.; Kohl, J.; Noci, G.

    1997-01-01

    The solar wind is a direct manifestation of the coronal heating processes which continue to elude us. For over three decades, observations in interplanetary space have identified two types of wind: a slow component with highly variable physical properties also characterized by speeds typically beow 500 kn/s, and a much less variable fast wind flowing on average at 750 km/s1.

  4. Repowering of wind farms - A case study

    Energy Technology Data Exchange (ETDEWEB)

    Nivedh, B.S. [Quality Engineering and Software Technologies, Bangalore (India); Devi, R.P.K. [College of Engineering. Power Systems Engineering, Guindy (India); Sreevalsan, E. [Gamesa Wind Turbines India Private Limited, Chennai (India)

    2012-07-01

    The main objective of the study is to devise a method for assessing the repowering potential and to improve the energy output from the wind farms and also to understand the impact on the power quality due to repowering. With repowering, the first-generation wind turbines can be replaced with modern multi-megawatt wind turbines. To carry-out the study an old wind farm located at Kayathar, Tamilnadu is selected. The wind farm was commissioned in 1990's with a capacity of 7.35MW, which consists of 36 Wind Turbines each with the capacity of 200kW and 225kW. The present annual energy generation of the wind farm is 7350MWhr with the plant load factor of 11.41%. The intent of this study is to predict the annual energy output of the wind farm after the repowering using WAsP (Wind Atlas Analysis Application Program). Further this study analyses the power quality issues of the various Wind Turbines. In addition, the main feeder, in which the wind farm which is taken for the study also modeled and the impact on power quality due to repowering also studied. Simulations were carried out using MATLAB. The results are analyzed to understand the significance of repowering to overcome the energy crisis of the nation since the best locations for wind in India are occupied by old wind turbines. The following are the observations and conclusions from the above study. Plant load factor (PLF) increased to 24 %, Energy yield increased to more than 4 times and the capacity of the wind farm became double. And in the view of power quality, comparing to the existing Feeder, Repowered Feeder having less reactive power consumption, voltage variations and flickers except the harmonic distortion. (Author)

  5. Potential of Offshore Wind Energy and Extreme Wind Speed Forecasting on the West Coast of Taiwan

    Directory of Open Access Journals (Sweden)

    Pei-Chi Chang

    2015-02-01

    Full Text Available It is of great importance and urgency for Taiwan to develop offshore wind power. However, relevant data on offshore wind energy resources are limited. This study imported wind speeds measured by a tidal station and a buoy into the software WAsP to estimate the high-altitude wind speeds in the two areas. A light detection and ranging (Lidar system was set up near the tidal station and buoy. High-altitude wind speeds measured by the Lidar system were compared with the WAsP-estimated values, and it was discovered that the two data sets were consistent. Then, long-term wind speed data observed by buoys and tidal stations at various locations were imported into WAsP to forecast wind speeds at heights of 55–200 m on the west coast of Taiwan. The software WAsP Engineering was used to analyze the extreme wind speeds in the same areas. The results show that wind speeds at 100 m are approximately 9.32–11.24 m/s, which means that the coastal areas of west Taiwan are rich in wind energy resources. When a long-term 10-min average wind speed is used, the extreme wind speed on the west coast is estimated to be between 36.4 and 55.3 m/s.

  6. Improving Maryland's Offshore Wind Energy Resource Estimate Using Doppler Wind Lidar Technology to Assess Microtmeteorology Controls

    Science.gov (United States)

    St. Pé, Alexandra; Wesloh, Daniel; Antoszewski, Graham; Daham, Farrah; Goudarzi, Navid; Rabenhorst, Scott; Delgado, Ruben

    2016-06-01

    There is enormous potential to harness the kinetic energy of offshore wind and produce power. However significant uncertainties are introduced in the offshore wind resource assessment process, due in part to limited observational networks and a poor understanding of the marine atmosphere's complexity. Given the cubic relationship between a turbine's power output and wind speed, a relatively small error in the wind speed estimate translates to a significant error in expected power production. The University of Maryland Baltimore County (UMBC) collected in-situ measurements offshore, within Maryland's Wind Energy Area (WEA) from July-August 2013. This research demonstrates the ability of Doppler wind lidar technology to reduce uncertainty in estimating an offshore wind resource, compared to traditional resource assessment techniques, by providing a more accurate representation of the wind profile and associated hub-height wind speed variability. The second objective of this research is to elucidate the impact of offshore micrometeorology controls (stability, wind shear, turbulence) on a turbine's ability to produce power. Compared to lidar measurements, power law extrapolation estimates and operational National Weather Service models underestimated hub-height wind speeds in the WEA. In addition, lidar observations suggest the frequent development of a low-level wind maximum (LLWM), with high turbinelayer wind shear and low turbulence intensity within a turbine's rotor layer (40m-160m). Results elucidate the advantages of using Doppler wind lidar technology to improve offshore wind resource estimates and its ability to monitor under-sampled offshore meteorological controls impact on a potential turbine's ability to produce power.

  7. Applicability of Synthetic Aperture Radar Wind Retrievals on Offshore Wind Resources Assessment in Hangzhou Bay, China

    Directory of Open Access Journals (Sweden)

    Rui Chang

    2014-05-01

    Full Text Available In view of the high cost and sparse spatial resolution of offshore meteorological observations, ocean winds retrieved from satellites are valuable in offshore wind resource assessment as a supplement to in situ measurements. This study examines satellite synthetic aperture radar (SAR images from ENVISAT advanced SAR (ASAR for mapping wind resources with high spatial resolution. Around 181 collected pairs of wind data from SAR wind maps and from 13 meteorological stations in Hangzhou Bay are compared. The statistical results comparing in situ wind speed and SAR-based wind speed show a standard deviation (SD of 1.99 m/s and correlation coefficient of R = 0.67. The model wind directions, which are used as input for the SAR wind speed retrieval, show a high correlation coefficient (R = 0.89 but a large standard deviation (SD = 42.3° compared to in situ observations. The Weibull probability density functions are compared at one meteorological station. The SAR-based results appear not to estimate the mean wind speed, Weibull scale and shape parameters and wind power density from the full in situ data set so well due to the lower number of satellite samples. Distributions calculated from the concurrent 81 SAR and in situ samples agree well.

  8. Emergency wind erosion control

    Science.gov (United States)

    February through May is the critical time for wind erosion in Kansas, but wind erosion can happen any time when high winds occur on smooth, wide fields with low vegetation and poor soil structure. The most effective wind erosion control is to ensure a protective cover of residue or growing crop thro...

  9. Mesoscale wind fluctuations over Danish waters

    DEFF Research Database (Denmark)

    Vincent, Claire Louise

    the time axis of the Hilbert spectrum. Results reveal clear patterns between wind uctuations and locally observed meteorological conditions. The analysis is expanded by classifying wind uctuations on time scales of 1{3 hours according to synoptic patterns, satellite pictures and wind classes. Results...... that realistic hour-scale wind uctuations and open cellular convection patterns develop in WRF simulations with 2km horizontal grid spacing. The atmospheric conditions during one of the case studies are then used to initialise a simplied version of the model that has no large scale weather forcing, topography...

  10. Transport of Venusian rolling 'stones' by wind?

    Science.gov (United States)

    Greeley, R.; Marshall, J. R.

    1985-02-01

    Simulations of Venusian wind processes are described which show that particles are moved by 'rolling' at wind speeds as much as 30 percent lower than those required for saltation threshold. This mode of wind transport is only observed for sustained periods in water on earth; thus, there are similarities between aqueous fluid transport on earth and atmospheric transport on Venus. The formation of small sand ridges and grooves oriented parallel to the wind direction is associated with the rolling of grains in Venusian simulations and these structures may be unique aeolian features on Venus.

  11. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    DEFF Research Database (Denmark)

    Feng, Ju; Shen, Wen Zhong

    2015-01-01

    quite well in terms of the coefficient of determination R-2. Then, the best of these joint distributions is used in the layout optimization of the Horns Rev 1 wind farm and the choice of bin sizes for wind speed and wind direction is also investigated. It is found that the choice of bin size for wind......Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint...... distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data at Horns Rev and three different joint distributions are obtained, which all fit the measurement data...

  12. Geostrophic winds in Denmark: A preliminary study

    DEFF Research Database (Denmark)

    Kristensen, L.; Jensen, G.

    1999-01-01

    High-precision barometers have been deployed at six sites in Denmark, four west and two east of the Great Belt. The purpose is to establish long climatological records of the geostrophic wind as a supplement to the records of tens of years of duration ofsurface observations of wind, temperature...

  13. Wind power. [electricity generation

    Science.gov (United States)

    Savino, J. M.

    1975-01-01

    A historical background on windmill use, the nature of wind, wind conversion system technology and requirements, the economics of wind power and comparisons with alternative systems, data needs, technology development needs, and an implementation plan for wind energy are presented. Considerable progress took place during the 1950's. Most of the modern windmills feature a wind turbine electricity generator located directly at the top of their rotor towers.

  14. Wind Power Utilization Guide.

    Science.gov (United States)

    1981-09-01

    wind causes the bladed -rotor turbine to rotate at low speed about the hori- zontal drive shaft that is always parallel to the force of the wind . The...current meter. Another form of a vertical axis wind turbine is a vertically straight- bladed wind turbine with cyclically pitched blades (see Figure 4.15...The expres- sions for the rotor torque for a Darrieus machine can be found in Reference 4.16. The Darrieus wind turbine

  15. Wind-Wave Characterization in a Wind-Jet Region: The Ebro Delta Case

    Directory of Open Access Journals (Sweden)

    Laura Ràfols

    2017-02-01

    Full Text Available This manuscript describes the wind-wave generation, development and fading in a complex area: a wind-jet region. The study region is the offshore Ebro Delta (NW Mediterranean Sea where strong cross-shelf winds occur due to a topographic channelization. This leads to relatively short-fetch conditions, which interact with the swell component. The third-generation wave model Simulating WAves Nearshore (SWAN is implemented and fed by high-resolution wind fields. A combination of buoy and High Frequency (HF radar data is used for model validation, resulting in a reasonable level of agreement. The numerical results characterize the wind-wave evolution during a wind jet. A bimodal spectrum is observed due to the interaction of swell and sea systems. The wave directional spreading exhibits lower values at the wind-jet axis. Finally, a reliability analysis of the wave data from an HF radar deployed at the region is carried out.

  16. A Comparison of Wind Flow Models for Wind Resource Assessment in Wind Energy Applications

    Directory of Open Access Journals (Sweden)

    Mathieu Landry

    2012-10-01

    Full Text Available The objective of this work was to assess the accuracy of various coupled mesoscale-microscale wind flow modeling methodologies for wind energy applications. This is achieved by examining and comparing mean wind speeds from several wind flow modeling methodologies with observational measurements from several 50 m met towers distributed across the study area. At the mesoscale level, with a 5 km resolution, two scenarios are examined based on the Mesoscale Compressible Community Model (MC2 model: the Canadian Wind Energy Atlas (CWEA scenario, which is based on standard input data, and the CWEA High Definition (CWEAHD scenario where high resolution land cover input data is used. A downscaling of the obtained mesoscale wind climate to the microscale level is then performed, where two linear microscale models, i.e., MsMicro and the Wind Atlas Analysis and Application Program (WAsP, are evaluated following three downscaling scenarios: CWEA-WAsP, CWEA-MsMicro and CWEAHD-MsMicro. Results show that, for the territory studied, with a modeling approach based on the MC2 and MsMicro models, also known as Wind Energy Simulation Toolkit (WEST, the use of high resolution land cover and topography data at the mesoscale level helps reduce modeling errors for both the mesoscale and microscale models, albeit only marginally. At the microscale level, results show that the MC2-WAsP modeling approach gave substantially better results than both MC2 and MsMicro modeling approaches due to tweaked meso-micro coupling.

  17. Modelling and measurements of power losses and turbulence intensity in wind turbine wakes at Middelgrunden offshore wind farm

    DEFF Research Database (Denmark)

    Barthelmie, Rebecca Jane; Frandsen, Sten Tronæs; Nielsen, Niels Morten

    2007-01-01

    Understanding of power losses and turbulence increase due to wind turbine wake interactions in large offshore wind forms is crucial to optimizing wind farm design. Power losses and turbulence increase due to wakes are quantified based on observations from Middel-grunden and state-of-the-art models....... Observed power losses due solely to wakes are approximately 10% on average. These are relatively high for a single line of wind turbines due in part to the close spacing of the wind farm. The wind form model Wind Analysis and Application Program (WAsP) is shown to capture wake losses despite operating...... beyond its specifications for turbine spacing. The paper describes two methods of estimating turbulence intensity. one based on the mean and standard deviation (SD) of wind speed from the nacelle anemometer, the other from mean power output and its SD. Observations from the nacelle anemometer indicate...

  18. An Icelandic wind atlas

    Science.gov (United States)

    Nawri, Nikolai; Nína Petersen, Gudrun; Bjornsson, Halldór; Arason, Þórður; Jónasson, Kristján

    2013-04-01

    While Iceland has ample wind, its use for energy production has been limited. Electricity in Iceland is generated from renewable hydro- and geothermal source and adding wind energy has not be considered practical or even necessary. However, adding wind into the energy mix is becoming a more viable options as opportunities for new hydro or geothermal power installation become limited. In order to obtain an estimate of the wind energy potential of Iceland a wind atlas has been developed as a part of the Nordic project "Improved Forecast of Wind, Waves and Icing" (IceWind). The atlas is based on mesoscale model runs produced with the Weather Research and Forecasting (WRF) Model and high-resolution regional analyses obtained through the Wind Atlas Analysis and Application Program (WAsP). The wind atlas shows that the wind energy potential is considerable. The regions with the strongest average wind are nevertheless impractical for wind farms, due to distance from road infrastructure and power grid as well as harsh winter climate. However, even in easily accessible regions wind energy potential in Iceland, as measured by annual average power density, is among the highest in Western Europe. There is a strong seasonal cycle, with wintertime power densities throughout the island being at least a factor of two higher than during summer. Calculations show that a modest wind farm of ten medium size turbines would produce more energy throughout the year than a small hydro power plants making wind energy a viable additional option.

  19. Wind Farm Wake: The 2016 Horns Rev Photo Case

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Nygaard, Nicolai Gayle; Volker, Patrick

    2017-01-01

    Offshore wind farm wakes were observed and photographed in foggy conditions at Horns Rev 2 on 25 January 2016 at 12:45 UTC. These new images show highly contrasting conditions regarding the wind speed, turbulence intensity, atmospheric stability, weather conditions and wind farm wake development...... rated power. The wind direction was southwesterly and long, narrow wakes persisted several rotor diameters downwind of the wind turbines. Eventually mixing of warm air from aloft dispersed the fog in the far wake region of the wind farm....

  20. Modelling of power fluctuations from large offshore wind farms

    DEFF Research Database (Denmark)

    Sørensen, Poul Ejnar; Cutululis, Nicolaos Antonio; Vigueras-Rodriguez, Antonio

    2008-01-01

    This paper deals with modelling of power fluctuations from large wind farms. The modelling is supported and validated using wind speed and power measurements from the two large offshore wind farms in Denmark. The time scale in focus is from 1 min to a couple of hours, where significant power...... fluctuations have been observed from these wind farms. Power and wind speed are measured with 1 s sampling time in all individual wind turbines in almost 1 year, which provides a substantial database for the analyses. The paper deals with diversified models representing each wind turbine individually...... and with aggregation of a wind farm to be represented by a single large wind turbine model. Copyright (C) 2007 John Wiley & Sons, Ltd....

  1. Extreme wind estimate for Hornsea wind farm

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo

    The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

  2. Wind turbine reliability database update.

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Valerie A.; Hill, Roger Ray; Stinebaugh, Jennifer A.; Veers, Paul S.

    2009-03-01

    This report documents the status of the Sandia National Laboratories' Wind Plant Reliability Database. Included in this report are updates on the form and contents of the Database, which stems from a fivestep process of data partnerships, data definition and transfer, data formatting and normalization, analysis, and reporting. Selected observations are also reported.

  3. Wind tunnel measurements of wake structure and wind farm power for actuator disk model wind turbines in yaw

    Science.gov (United States)

    Howland, Michael; Bossuyt, Juliaan; Kang, Justin; Meyers, Johan; Meneveau, Charles

    2016-11-01

    Reducing wake losses in wind farms by deflecting the wakes through turbine yawing has been shown to be a feasible wind farm control approach. In this work, the deflection and morphology of wakes behind a wind turbine operating in yawed conditions are studied using wind tunnel experiments of a wind turbine modeled as a porous disk in a uniform inflow. First, by measuring velocity distributions at various downstream positions and comparing with prior studies, we confirm that the nonrotating wind turbine model in yaw generates realistic wake deflections. Second, we characterize the wake shape and make observations of what is termed a "curled wake," displaying significant spanwise asymmetry. Through the use of a 100 porous disk micro-wind farm, total wind farm power output is studied for a variety of yaw configurations. Strain gages on the tower of the porous disk models are used to measure the thrust force as a substitute for turbine power. The frequency response of these measurements goes up to the natural frequency of the model and allows studying the spatiotemporal characteristics of the power output under the effects of yawing. This work has been funded by the National Science Foundation (Grants CBET-113380 and IIA-1243482, the WINDINSPIRE project). JB and JM are supported by ERC (ActiveWindFarms, Grant No. 306471).

  4. Influence of local wind speed and direction on wind power dynamics – Application to offshore very short-term forecasting

    DEFF Research Database (Denmark)

    Gallego, Cristobal; Pinson, Pierre; Madsen, Henrik

    2011-01-01

    on one-step ahead forecasting and a time series resolution of 10 min. It has been found that the local wind direction contributes to model some features of the prevailing winds, such as the impact of the wind direction on the wind variability, whereas the non-linearities related to the power......Wind power time series usually show complex dynamics mainly due to non-linearities related to the wind physics and the power transformation process in wind farms. This article provides an approach to the incorporation of observed local variables (wind speed and direction) to model some...... of these effects by means of statistical models. To this end, a benchmarking between two different families of varyingcoefficient models (regime-switching and conditional parametric models) is carried out. The case of the offshore wind farm of Horns Rev in Denmark has been considered. The analysis is focused...

  5. Wind characteristics and energy potentialities of some selected sites ...

    African Journals Online (AJOL)

    The wind regime as observed in three meteorological stations in the north Cameroon are presented in form of velocity duration curves as well as in form of velocity frequency curves. Monthly average wind speed distributions were determined for each station. Based on the analysed data, the utilisation of wind for power ...

  6. Satellite information for wind energy applications

    Energy Technology Data Exchange (ETDEWEB)

    Nielsen, M.; Astrup, P.; Bay Hasager, C.

    2004-11-01

    An introduction to satellite information relevant for wind energy applications is given. It includes digital elevation model (DEM) data based on satellite observations. The Shuttle Radar Topography Mission (SRTM) is useful for regional scale wind resource studies. Comparison results from complex terrain in Spain and flat terrain in Denmark are found to be acceptable for both sites. Also land cover type information can be retrieved from satellite observations. Land cover type maps have to be combined with roughness data from field observation or literature values. Land cover type maps constitute an aid to map larger regions within shorter time. Field site observations of obstacles and hedges are still necessary. The raster-based map information from DEM and land cover maps can be converted for use in WASP. For offshore locations it is possible to estimate the wind resources based on ocean surface wind data from several types of satellite observations. The RWT software allows an optimal calculation of SAR wind resource statistics. A tab-file with SAR-based observed wind climate (OWC) data can be obtained for 10 m above sea level and used in WASP. RWT uses a footprint averaging technique to obtain data as similar as possible to mast observations. Maximum-likelihood fitting is used to calculate the Weibull A and k parameters from the constrained data set. Satellite SAR wind maps cover the coastal zone from 3 km and offshore with very detailed information of 400 m by 400 m grid resolution. Spatial trends in mean wind, energy density, Weibull A and k and uncertainty values are provided for the area of interest. Satellite scatterometer wind observations have a spatial resolution of 25 km by 25 km. These data typically represent a site further offshore, and the tab-file statistics should be used in WASP combined with topography and roughness information to assess the coastal wind power potential. Scatterometer wind data are observed {approx} twice per day, whereas SAR only

  7. AGN Winds and Blazar Phenomenology

    Science.gov (United States)

    Kazanas, Demos

    2012-01-01

    The launch of {\\em Fermi} produced a significant number of AGN detections to allow statistical treatment of their properties. One of the first such systematics was the "Blazar Divide" in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. Further data accumulation indicated this separation to be less clear than thought before. An MHD wind model which can model successfully the Seyfert X-ray absorber properties provides the vestiges of an account of the observed blazar classification. We propose to employ this model to model in detail the broad band blazar spectra and their statistical properties in terms of the physical parameters of these MHD winds.

  8. Wind power today

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  9. Wind turbines acoustic measurements

    Science.gov (United States)

    Trematerra, Amelia; Iannace, Gino

    2017-07-01

    The importance of wind turbines has increased over the last few years throughout the European Community. The European energy policy guidelines state that for the year 2020 20% of all energy must be produced by alternative energy sources. Wind turbines are an important type of energy production without petrol. A wind speed in a range from 2.5 m/s to 25.0 m/s is needed. One of the obstacles to the widespread diffusion of wind turbine is noise generation. This work presents some noise measurements of wind turbines in the South of Italy, and discusses the noise problems for the people living near wind farms.

  10. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to