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1
Poulain, Pierre-Marie, Riccardo Gerin, Elena Mauri, and Romain Pennel. "Wind Effects on Drogued and Undrogued Drifters in the Eastern Mediterranean." Journal of Atmospheric and Oceanic Technology 26, no. 6 (June 1, 2009): 1144–56. http://dx.doi.org/10.1175/2008jtecho618.1.
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Abstract The wind effects on drogued and undrogued drifters are assessed using Coastal Ocean Dynamics Experiment (CODE) and Surface Velocity Program (SVP) drifter datasets and ECMWF wind products in the eastern Mediterranean. Complex and real linear regression models are used to estimate the relative slip of undrogued SVP drifters and to extract the wind-driven currents from the drifter velocities. The frequency response of the wind-driven currents is studied using cross-spectral analysis. By comparing the velocities of cotemporal and nearly collocated undrogued and drogued SVP drifters, it appears that undrogued SVP drifters have a general downwind slippage of about 1% of the wind speed. Time-lagged complex correlations and cross-spectral results show that the wind response is almost simultaneous. The velocities of SVP drifters drogued to 15 m are poorly correlated with the winds (R2 ≈ 3%): wind-driven currents have a magnitude of 0.7% of the wind speed and are 27°–42° to the right of the wind. For undrogued SVP drifters, the correlation with the winds increases to R2 ≈ 22% and the angle between winds and currents decreases to 17°–20°. The magnitude of the wind-driven currents is about 2% of the wind speed. For CODE designs, wind-driven currents are 1% of the wind speed at an angle of about 28° to the right of the wind (R2 ≈ 8%). Spectral and cospectral analyses reveal that the drifters sampled more anticyclonic than cyclonic motions. The inner coherence spectra show that wind and currents are more correlated at temporal scales spanning 3–10 days. They also confirm that the wind response is quasi-simultaneous and that currents are generally to the right of the wind.
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Plant, William J., William C. Keller, and Kenneth Hayes. "Simultaneous Measurement of Ocean Winds and Waves with an Airborne Coherent Real Aperture Radar." Journal of Atmospheric and Oceanic Technology 22, no. 7 (July 1, 2005): 832–46. http://dx.doi.org/10.1175/jtech1724.1.
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Abstract A coherent, X-band airborne radar has been developed to measure wind speed and direction simultaneously with directional wave spectra on the ocean. The coherent real aperture radar (CORAR) measures received power, mean Doppler shifts, and mean Doppler bandwidths from small-resolution cells on the ocean surface and converts them into measurements of winds and waves. The system operates with two sets of antennas, one rotating and one looking to the side of the airplane. The rotating antennas yield neutral wind vectors at a height of 10 m above the ocean surface using a scatterometer model function to relate measured cross sections to wind speed and direction. The side-looking antennas produce maps of normalized radar cross section and line-of-sight velocity from which directional ocean wave spectra may be obtained. Capabilities of CORAR for wind and wave measurement are illustrated using data taken during the Shoaling Waves Experiment (SHOWEX) sponsored by the Office of Naval Research. Wind vectors measured by CORAR agree well with those measured by nearby buoys. Directional wave spectra obtained by CORAR also agree with buoy measurements and illustrate that offshore winds can produce dominant waves at an angle to the wind vector that are in good agreement with the measurements. The best agreement is produced using the Joint North Sea Wave Project (JONSWAP) parameterizations of the development of wave height and period with fetch.
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Luminari, A., E. Piconcelli, F. Tombesi, L. Zappacosta, F. Fiore, L. Piro, and F. Vagnetti. "Constraining the geometry of the nuclear wind in PDS 456 using a novel emission model." Astronomy & Astrophysics 619 (November 2018): A149. http://dx.doi.org/10.1051/0004-6361/201833623.
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Context. Outflows from active galactic nuclei (AGN) are often invoked to explain the co-evolution of AGN and their host galaxies, and the scaling relations between the central black hole mass and the bulge velocity dispersion. Nuclear winds are often seen in the X-ray spectra through Fe K shell transitions and some of them are called ultra fast outflows (UFOs) due to their high velocities, up to some fractions of the speed of light. If they were able to transfer some percentage of the AGN luminosity to the host galaxy, this might be enough to trigger an efficient feedback mechanism. Aims. We aim to establish new constraints on the covering fraction and on the kinematic properties of the UFO in the powerful (Lbol ∼ 1047 erg s−1) quasar PDS 456, an established Rosetta stone for studying AGN feedback from disk winds. This will allow us to estimate the mass outflow rate and the energy transfer rate of the wind, which are key quantities to understand the potential impact on the host galaxy. Methods. We analyze two sets of simultaneous XMM-Newton and NuSTAR observations taken in September 2013 and reported in Nardini et al. (2015, Science, 347, 860) as having similar broadband spectral properties. We fit the Fe K features with a P-Cygni profile between 5 and 14 keV, using a novel Monte Carlo model for the WINd Emission (WINE). Results. We find an outflow velocity ranging from 0.17 to 0.28 c, with a mean value of 0.23 c. We obtain an opening angle of the wind of 71−8+13 deg and a covering fraction of 0.7−0.3+0.2, suggesting a wide-angle outflow. We check the reliability of the WINE model by performing extensive simulations of joint XMM-Newton and NuSTAR observations. Furthermore, we test the accuracy of the WINE model in recovering the geometrical properties of UFOs by simulating observations with the forthcoming Advanced Telescope for High-Energy Astrophysics (ATHENA) in the X-ray band.
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Rao, I. Srinivasa, V. K. Anandan, and P. Narasimha Reddy. "Evaluation of DBS Wind Measurement Technique in Different Beam Configurations for a VHF Wind Profiler." Journal of Atmospheric and Oceanic Technology 25, no. 12 (December 1, 2008): 2304–12. http://dx.doi.org/10.1175/2008jtecha1113.1.
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Abstract Atmospheric winds in the troposphere have been observed routinely for many years with wind profiling (VHF and UHF) radars using the Doppler beam swinging (DBS) technique. Accuracy of wind estimates using wind profiling radars with different beam configurations has its limitations due to both the system of observation and atmospheric conditions. This paper presents a quantitative analysis and evaluation of horizontal wind estimation in different beam configurations up to an altitude of 18 km using the mesosphere–stratosphere–troposphere (MST) radar located in Gadanki, India. Horizontal wind velocities are derived in three different ways using two-, three-, and four-beam configurations. To know the performance of each configuration, radar-derived winds have been compared with the winds obtained by simultaneous GPS sonde balloon measurements, which are considered to be a standard reference by default. Results show that horizontal winds measured using three different beam configurations are comparable in general but discrepancy varies from one beam configuration to the other. It is observed that horizontal winds measured using four-beam configuration (east, west, north, and south) have better estimates than the other two-beam configurations. The standard deviation was found to be varying from 1.4 to 2.5 m s−1 and percentage error is about 9.68%–12.73% in four-beam configuration, whereas in other beam configurations the standard deviation is about 1.65–3.9 m s−1 and the percentage error is about 11.29%–15.16% with reference to GPS sonde balloon–measured winds.
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Park, Soojin, Sang-Woo Kim, Moon-Soo Park, and Chang-Keun Song. "Measurement of Planetary Boundary Layer Winds with Scanning Doppler Lidar." Remote Sensing 10, no. 8 (August 10, 2018): 1261. http://dx.doi.org/10.3390/rs10081261.
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The accurate measurement of wind profiles in the planetary boundary layer (PBL) is important not only for numerical weather prediction, but also for air quality modeling. Two wind retrieval methods using scanning Doppler light detection and ranging (lidar) measurements were compared and validated with simultaneous radiosonde soundings. A comparison with 17 radiosonde sounding profiles showed that the sine-fitting method was able to retrieve a larger number of data points, but the singular value decomposition method showed significantly smaller bias (0.57 m s−1) and root-mean-square error (1.75 m s−1) with radiosonde soundings. Increasing the averaging time interval of radial velocity for obtaining velocity azimuth display scans to 15 min resulted in better agreement with radiosonde soundings due to the signal averaging effect on noise. Simultaneous measurements from collocated wind Doppler lidar and aerosol Mie-scattering lidar revealed the temporal evolution of PBL winds and the vertical distribution of aerosols within the PBL.
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Simkhada, D. B., J. B. Snively, M. J. Taylor, and S. J. Franke. "Analysis and modeling of ducted and evanescent gravity waves observed in the Hawaiian airglow." Annales Geophysicae 27, no. 8 (August 19, 2009): 3213–24. http://dx.doi.org/10.5194/angeo-27-3213-2009.
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Abstract. Short-period gravity waves of especially-small horizontal scale have been observed in the Maui, Hawaii airglow. Typical small-scale gravity wave events have been investigated, and intrinsic wave propagation characteristics have been calculated from simultaneous meteor radar wind measurements. Here we report specific cases where wave structure is significantly determined by the local wind structure, and where wave characteristics are consistent with ducted or evanescent waves throughout the mesopause region. Two of the documented events, exhibiting similar airglow signatures but dramatically different propagation conditions, are selected for simple numerical modeling case studies. First, a Doppler-ducted wave trapped within relatively weak wind flow is examined. Model results confirm that the wave is propagating in the 85–95 km region, trapped weakly by evanescence above and below. Second, an evanescent wave in strong wind flow is examined. Model results suggest an opposite case from the first case study, where the wave is instead trapped above or below the mesopause region, with strong evanescence arising in the 85–95 km airglow region. Distinct differences between the characteristics of these visibly-similar wave events demonstrate the need for simultaneous observations of mesopause winds to properly assess local propagation conditions.
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Moss, Andrew C., Corwin J. Wright, Robin N. Davis, and Nicholas J. Mitchell. "Gravity-wave momentum fluxes in the mesosphere over Ascension Island (8° S, 14° W) and the anomalous zonal winds of the semi-annual oscillation in 2002." Annales Geophysicae 34, no. 2 (March 3, 2016): 323–30. http://dx.doi.org/10.5194/angeo-34-323-2016.
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Abstract. Anomalously strong westward winds during the first phase of the equatorial mesospheric semi-annual oscillation (MSAO) have been attributed to unusual filtering conditions producing exceptional gravity-wave fluxes. We test this hypothesis using meteor-radar measurements made over Ascension Island (8° S, 14° W). An anomalous wind event in 2002 of −85.5 ms−1 occurred simultaneously with the momentum fluxes of high-frequency gravity waves reaching the largest observed westward values of −29 m2 s−2 and strong westward wind accelerations of −510 ms−1 day−1. However, despite this strong wave forcing during the event, no unusual filtering conditions or significant increases in wave-excitation proxies were observed. Further, although strong westward wave-induced accelerations were also observed during the 2006 MSAO first phase, there was no corresponding simultaneous response in westward wind. We thus suggest that strong westward fluxes/accelerations of high-frequency gravity waves are not always sufficient to produce anomalous first-phase westward MSAO winds and other forcing may be significant.
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Nishikawa, Hatsumi, Yoshihiro Tachibana, Yoshimi Kawai, Mayumi K. Yoshioka, and Hisashi Nakamura. "Evidence for SST-Forced Anomalous Winds Revealed from Simultaneous Radiosonde Launches from Three Ships across the Kuroshio Extension Front." Monthly Weather Review 144, no. 10 (October 2016): 3553–67. http://dx.doi.org/10.1175/mwr-d-15-0442.1.
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Simultaneous launches of radiosondes were conducted from three research vessels aligned meridionally across a sea surface temperature (SST) front on the flank of the Kuroshio Extension. The soundings carried out every 2 h over 5 days in early July 2012 provided a unique opportunity in capturing unambiguous data on anomalous easterly winds derived from a pronounced meridional SST gradient. The data indicate that a meridional contrast in surface heat fluxes from the underlying ocean enhanced the air temperature anomaly across the SST front, which was observed from the surface up to 300-m altitude. Correspondingly, high and low pressure anomalies that reached 800-m altitude formed on the north and south sides of the SST front, respectively. These temperature and pressure anomalies were maintained even during the passage of synoptic-scale disturbances. Although the free-tropospheric winds are overall westerly, winds below the 1000-m level were easterly due to geostrophic anomalies driven by the northward pressure gradient near the surface. During periods of the northerlies at the surface, especially over the warmer side of the SST front, the wind direction changed in a clockwise direction from 1500 m to the surface, in the opposite sense to the Ekman spiral. The vertical wind shear is apparently in the thermal wind balance ascribed to the meridional contrast in air temperature derived from the SST anomaly.
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Anandan, V. K., I. Srinivasa Rao, and P. Narasimha Reddy. "A Study on Optimum Tilt Angle for Wind Estimation Using Indian MST Radar." Journal of Atmospheric and Oceanic Technology 25, no. 9 (September 1, 2008): 1579–89. http://dx.doi.org/10.1175/2008jtecha1030.1.
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Abstract The effect of tilt angle on horizontal wind estimation is studied using Indian mesosphere–stratosphere–troposphere (MST) radar located at Gadanki (13.45°N, 79.18°E). It operates in Doppler beam swinging (DBS) mode with a beamwidth of 3°. Horizontal winds are computed for different tilt angles from 3° to 15° with an increment of 3° from a height range of 3.6–18 km. The effective beam pointing angle (θeff) is calculated to determine the effect of aspect sensitivity on the determination of horizontal wind components. For different tilt angles radar-derived winds are compared with simultaneous GPS sonde wind measurements, which were launched from a nearby site. The first method utilizes direct comparison of radar-derived winds with those of GPS sondes using the actual beam pointing angle; the second method uses the effective beam pointing angle derived from the ratios of two oblique beams. For this study a variety of statistics were explored in terms of standard deviation, correlation coefficient, and percentage error. From the results it is observed that in agreement with previous studies, the effective beam pointing angle deviates from the actual beam pointing angle, which results in the underestimation of horizontal wind components, and also when tilt angle is close to zenith and far from zenith, the estimation of horizontal winds is found to be far from true values at different heights. Radar wind estimation has better agreement with GPS sonde measurement when the off-zenith angle is around 10°. It is also found that correction to the actual beam pointing angle provides 3%–6% improved agreement between the radar and GPS wind measurements.
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Ahmadikia, Hossein, Mohsen Soleimani, and Ehsan Gholami. "Simultaneous effects of water spray and crosswind on performance of natural draft dry cooling tower." Thermal Science 17, no. 2 (2013): 443–55. http://dx.doi.org/10.2298/tsci110510134a.
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To investigate the effect of water spray and crosswind on the effectiveness of the natural draft dry cooling tower (NDDCT), a three-dimensional model has been developed. Efficiency of NDDCT is improved by water spray system at the cooling tower entrance for high ambient temperature condition with and without crosswind. The natural and forced heat convection flow inside and around the NDDCT is simulated numerically by solving the full Navier-Stokes equations in both air and water droplet phases. Comparison of the numerical results with one-dimensional analytical model and the experimental data illustrates a well-predicted heat transfer rate in the cooling tower. Applying water spray system on the cooling tower radiators enhances the cooling tower efficiency at both no wind and windy conditions. For all values of water spraying rate, NDDCTs operate most effectively at the crosswind velocity of 3m/s and as the wind speed continues to rise to more than 3 m/s up to 12 m/s, the tower efficiency will decrease by approximately 18%, based on no-wind condition. The heat transfer rate of radiator at wind velocity 10 m/s is 11.5% lower than that of the no wind condition. This value is 7.5% for water spray rate of 50kg/s.
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Benmahi, B., T. Cavalié, T. K. Greathouse, V. Hue, R. Giles, S. Guerlet, A. Spiga, and R. Cosentino. "Mapping the zonal winds of Jupiter’s stratospheric equatorial oscillation." Astronomy & Astrophysics 652 (August 2021): A125. http://dx.doi.org/10.1051/0004-6361/202141523.
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Context. Since the 1950s, quasi-periodic oscillations have been studied in the terrestrial equatorial stratosphere. Other planets of the Solar System present (or are expected to present) such oscillations; for example the Jupiter equatorial oscillation and the Saturn semi-annual oscillation. In Jupiter’s stratosphere, the equatorial oscillation of its relative temperature structure about the equator is characterized by a quasi-period of 4.4 yr. Aims. The stratospheric wind field in Jupiter’s equatorial zone has never been directly observed. In this paper, we aim to map the absolute wind speeds in Jupiter’s equatorial stratosphere in order to quantify vertical and horizontal wind and temperature shear. Methods. Assuming geostrophic equilibrium, we apply the thermal wind balance using almost simultaneous stratospheric temperature measurements between 0.1 and 30 mbar performed with Gemini/TEXES and direct zonal wind measurements derived at 1 mbar from ALMA observations, all carried out between March 14 and 22, 2017. We are thus able to self-consistently calculate the zonal wind field in Jupiter’s stratosphere where the JEO occurs. Results. We obtain a stratospheric map of the zonal wind speeds as a function of latitude and pressure about Jupiter’s equator for the first time. The winds are vertically layered with successive eastward and westward jets. We find a 200 m s−1 westward jet at 4 mbar at the equator, with a typical longitudinal variability on the order of ~50 m s−1. By extending our wind calculations to the upper troposphere, we find a wind structure that is qualitatively close to the wind observed using cloud-tracking techniques. Conclusions. Almost simultaneous temperature and wind measurements, both in the stratosphere, are a powerful tool for future investigations of the JEO (and other planetary equatorial oscillations) and its temporal evolution.
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Wurman, Joshua, Karen Kosiba, and Paul Robinson. "In Situ, Doppler Radar, and Video Observations of the Interior Structure of a Tornado and the Wind–Damage Relationship." Bulletin of the American Meteorological Society 94, no. 6 (June 1, 2013): 835–46. http://dx.doi.org/10.1175/bams-d-12-00114.1.
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Direct observations of the winds inside a tornado were obtained with an instrumented armored vehicle, the Tornado Intercept Vehicle (TIV), and integrated with finescale mobile Doppler radar (Doppler on Wheels) data revealing, for the first time, the structure of the near-ground three-dimensional wind field in and around the core region of a strong tornado, and permitting comparison with conceptual models. Inward and upward spiraling near-surface flow, upward motion near the surface, and an axial downdraft aloft are documented, as well as a periodic oscillation in tornado intensity. Simultaneous video documentation of damage occurring during the tornado is related to the direct wind observations, permitting the first comparisons of the time history of damage to the time history of directly measured winds and a limited evaluation of the underlying assumptions and quantitative relationships in the enhanced Fujita (EF) scale.
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Yang, Xin, Wei Qian, Daoyi Gong, Chuanfeng Zhao, Pak-wai Chan, Wei Zhou, Yu Huang, Fang Zhang, and Zhigang Li. "Vertical Characteristics of Pollution Transport in Hong Kong and Beijing, China." Atmosphere 12, no. 4 (April 4, 2021): 457. http://dx.doi.org/10.3390/atmos12040457.
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Transported pollution plays an important role in the atmospheric environment of eastern China. This study analyzed the characteristics of surface winds at different air quality levels using meteorological station observations of both wind and mass concentrations of particulate matter with aerodynamic diameters <2.5 μm (PM2.5) over Hong Kong and Beijing. In recent decades, wind directions at the surface exhibit a similar pattern for both good and poor air quality levels at all three stations, indicating a weak relationship between surface winds and air quality in Hong Kong. However, winds at a height of 1–2 km govern pollution accumulation. This dominant role is illustrated by a sudden change in wind direction within this layer and a simultaneous pollution accumulation stage on 8 January 2014. The controlling influence of winds at 1–2 km on both the deterioration and improvement of air quality is also supported by a distinct vertical wind distribution for all 21 monotonic increasing stages and 17 decreasing stages of PM2.5. In contrast, air pollution is transported to Beijing throughout the atmospheric layer that extends from the surface to a height of more than 3 km. This key difference may be due to variations in meteorology, topography, and emission sources between Hong Kong and Beijing. The results that layer of 1–2 km in Hong Kong and of surface to 3 km in Beijing is the height where pollution transport is most likely to occur are critical for forecasting severe haze episodes in eastern China.
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Щербаков, Александр, Aleksandr Shcherbakov, Андрей Медведев, Andrey Medvedev, Дмитрий Кушнарев, Dmitriy Kushnarev, Максим Толстиков, Maksim Tolstikov, Сергей Алсаткин, and Sergei Alsatkin. "Calculation of meridional neutral winds in middle latitudes from the Irkutsk incoherent scatter radar data." Solnechno-Zemnaya Fizika 1, no. 3 (September 27, 2015): 37–48. http://dx.doi.org/10.12737/10962.
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The paper sequentially presents technique for determining velocity of meridional neutral winds from the Irkutsk Incoherent Scatter Radar (IISR) data. Due to IISR specific features effective at other IS radars, techniques for determining ionosphere parameters, in particular plasma drift velocities, resulted in considerable variance of defined parameters. To measure the plasma drift velocity taking into account such IISR features, we have developed a special technique based on phase analysis of autocorrelation function of incoherent scatter signal. The technique needs to be tested, and for this purpose, an experiment was carried out to measure velocities of low-orbit satellites. However, methods for meridional neutral wind calculations used by many authors [Evans, 1970] with the use of drift velocities obtained before, resulted in great disagreements with empirical HWM93 and HWM07 wind models. In addition, simultaneous measurements at two frequencies at IISR showed that it was difficult to explain such differences without taking into account the cross-field movements. Possible underestimation of the impact of movements generated by electric fields can result in serious error in determining wind velocities. The paper considers improvements for methods of calculating winds, and shows that the results obtained with it are in a better agreement with wind models.
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Kendall, Roger A., and Edward C. Carterette. "Perceptual Scaling of Simultaneous Wind Instrument Timbres." Music Perception 8, no. 4 (1991): 369–404. http://dx.doi.org/10.2307/40285519.
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Timbral similarities among wind instrument duos were studied. Flute, oboe, E♭ alto saxophone, B♭ clarinet, and B♭ trumpet instrumentalists performed in all possible duo pairings (dyads). Source material included B♭4 unisons, unison melody, major thirds, and harmonized melody. Nonunison combinations had each instrument of the pair as the soprano, creating a total of six contexts. Music major and nonmusic major subjects rated the similarity of all possible pairs of dyads in each of the six contexts. Classical multidimensional scaling (MDS) was performed; contexts were treated as " subjects" in an individual differences scaling (INDSCAL) analysis of composite data. The resulting spaces had two stable, interpretable dimensions. From verbal attribute rating experiments ( Kendall & Carterette, in preparation, a), these were identified as " nasal" vs. " not nasal," and " rich" vs. " brilliant." A third dimension was interpreted as "simple" vs. "complex."Extrema in the space were associated with three of the five instruments: Trumpet (brilliant), saxophone (rich), and oboe ( nasal). Data that were amalgamated over contexts and plotted in two dimensions yielded a circumplicial configuration. Implications for orchestration are discussed and a theoretical model of timbre combinations and groupings is presented.
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Wada, Eiko, Hiroyuki Hashiguchi, Masayuki K. Yamamoto, Michihiro Teshiba, and Shoichiro Fukao. "Simultaneous Observations of Cirrus Clouds with a Millimeter-Wave Radar and the MU Radar." Journal of Applied Meteorology 44, no. 3 (March 1, 2005): 313–23. http://dx.doi.org/10.1175/jam2191.1.
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Abstract Observations of frontal cirrus clouds were conducted with the scanning millimeter-wave radar at the Shigaraki Middle and Upper Atmosphere (MU) Radar Observatory in Shiga, Japan, during 30 September–13 October 2000. The three-dimensional background winds were also observed with the very high frequency (VHF) band MU radar. Comparing the observational results of the two radars, it was found that the cirrus clouds appeared coincident with the layers of the strong vertical shear of the horizontal winds, and they developed and became thicker under the condition of the strong vertical shear of the horizontal wind and updraft. The result of the radiosonde observation indicated that Kelvin–Helmholtz instability (KHI) occurred at 8–9-km altitudes because of the strong vertical shear of the horizontal wind. The warm and moist air existed above the 8.5-km altitude, and the cold and dry air existed below the 8.5-km altitude. As a result of the airmass mixing of air above and below the 8.5-km altitudes, the cirrus clouds were formed. The updraft, which existed at 8.5–12-km altitude, caused the development of the cirrus clouds with the thickness of >2 km. By using the scanning millimeter-wave radar, the three-dimensional structure of cell echoes formed by KHI for the first time were successfully observed.
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Hasebe, F., T. Tsuda, T. Nakamura, and M. D. Burrage. "Validation of HRDI MLT winds with meteor radars." Annales Geophysicae 15, no. 9 (September 30, 1997): 1142–57. http://dx.doi.org/10.1007/s00585-997-1142-7.
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Abstract. A validation study of the mesospheric and lower-thermospheric (MLT) wind velocities measured by the High-Resolution Doppler Imager (HRDI) on board the Upper-Atmosphere Research Satellite (UARS) has been carried out, comparing with observations by meteor radars located at Shigaraki, Japan and Jakarta, Indonesia. The accuracy of the HRDI winds relative to the meteor radars is obtained by a series of simultaneous wind measurements at the time of UARS overpasses. Statistical tests on the difference in the wind vectors observed by HRDI and the meteor radars are applied to determine whether the wind speed has been overestimated by HRDI (or underestimated by the MF radars) as previously noticed in HRDI vs. MF radar comparisons. The techniques employed are the conventional t-test applied to the mean values of the paired wind vector components as well as wind speeds, and two nonparametric tests suitable for testing the paired wind speed. The square-root transformation has been applied before the t-tests of the wind speed in order to fit the wind-speed distribution function to the normal distribution. The overall results show little evidence of overestimation by HRDI (underestimation by meteor radars) of wind velocities in the MLT region. Some exceptions are noticed, however, at the altitudes around 88 km, where statistical differences occasionally reach a level of significance of 0.01. The validation is extended to estimate the precision of the wind velocities by both HRDI and meteor radars. In the procedure, the structure function defined by the mean square difference of the observed anomalies is applied in the vertical direction for the profile data. This method assumes the isotropy and the homogeneity of variance for the physical quantity and the homogeneity of variance for the observational errors. The estimated precision is about 6ms–1 for the Shigaraki meteor radar, 15ms–1 for the Jakarta meteor radar, and 20ms–1 for HRDI at 90-km altitude. These values can be used to confirm the statistical significance of the wind field obtained by averaging the observed winds.
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Deepa, V., G. Ramkumar, and K. K. Kumar. "Observational evidence for the generation of a 4-day oscillation in the low-latitude middle atmosphere associated with an anomalous stratospheric cooling." Annales Geophysicae 25, no. 9 (October 2, 2007): 1959–65. http://dx.doi.org/10.5194/angeo-25-1959-2007.
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Abstract. Altitude profiles of temperature in the stratosphere and lower mesosphere over Gadanki (13.5° N, 79.2° E), based on lidar observations during the Equatorial Wave Study campaign (29 February–2 April 2000), showed an anomalous cooling of the stratosphere, lasting for about 4–5 days. Immediately following this stratospheric cooling, a prominent ~4-day period oscillation is observed in the zonal, as well as meridional wind in the 30–50 km altitude region, obtained from simultaneous rocketsonde and balloon wind measurements. The amplitude of this wave is in the range of 5–15 ms−1 in this altitude region. The altitude profiles of phase of this 4-day oscillation show a constant phase with height indicating that the wave is not propagating vertically. The causative mechanism for the sudden cooling is investigated by examining the day-to-day variation in the total atmospheric column ozone. Zonal and meridional wind components of this oscillation are approximately in quadrature phase, with zonal wind leading the meridional wind. Strikingly, while the 4-day wave is clearly observable in the zonal and meridional winds, it is almost absent in the temperature.
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Satheesh Kumar, S., T. Narayana Rao, and A. Taori. "A novel approach for the extraction of cloud motion vectors using airglow imager measurements." Atmospheric Measurement Techniques 8, no. 9 (September 23, 2015): 3893–901. http://dx.doi.org/10.5194/amt-8-3893-2015.
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Abstract. The paper explores the possibility of implementing an advanced photogrammetric technique, generally employed for satellite measurements, on airglow imager, a ground-based remote sensing instrument primarily used for upper atmospheric studies, measurements of clouds for the extraction of cloud motion vectors (CMVs). The major steps involved in the algorithm remain the same, including image processing for better visualization of target elements and noise removal, identification of target cloud, setting a proper search window for target cloud tracking, estimation of cloud height, and employing 2-D cross-correlation to estimate the CMVs. Nevertheless, the implementation strategy at each step differs from that of satellite, mainly to suit airglow imager measurements. For instance, climatology of horizontal winds at the measured site has been used to fix the search window for target cloud tracking. The cloud height is estimated very accurately, as required by the algorithm, using simultaneous collocated lidar measurements. High-resolution, both in space and time (4 min), cloud imageries are employed to minimize the errors in retrieved CMVs. The derived winds are evaluated against MST radar-derived winds by considering it as a reference. A very good correspondence is seen between these two wind measurements, both showing similar wind variation. The agreement is also found to be good in both the zonal and meridional wind velocities with RMSEs < 2.4 m s−1. Finally, the strengths and limitations of the algorithm are discussed, with possible solutions, wherever required.
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Satheesh Kumar, S., T. Narayana Rao, and A. Taori. "A novel approach for the extraction of cloud motion vectors using airglow imager measurements." Atmospheric Measurement Techniques Discussions 8, no. 3 (March 12, 2015): 2657–82. http://dx.doi.org/10.5194/amtd-8-2657-2015.
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Abstract. The paper explores the possibility of implementing an advanced photogrammetric technique, generally employed for satellite measurements, on airglow imager, a ground-based remote sensing instrument primarily used for upper atmospheric studies, measurements of clouds for the extraction of cloud motion vectors (CMVs). The major steps involved in the algorithm remain the same, including image processing for better visualization of target elements and noise removal, identification of target cloud, setting a proper search window for target cloud tracking, estimation of cloud height, and employing 2-D cross-correlation to estimate the CMVs. Nevertheless, the implementation strategy at each step differs from that of satellite, mainly to suit airglow imager measurements. For instance, climatology of horizontal winds at the measured site has been used to fix the search window for target cloud tracking. The cloud height is estimated very accurately, as required by the algorithm, using simultaneous collocated Lidar measurements. High-resolution, both in space and time (4 min), cloud imageries are employed to minimize the errors in retrieved CMVs. The derived winds are evaluated against MST radar-derived winds by considering it as a reference. A very good correspondence is seen between these two wind measurements, both showing similar wind variation. The agreement is also found to be good in the both zonal and meridional wind velocities with RMSEs < 2.4 m s−1. At the end, the strengths and limitations of the algorithm are discussed, with possible solutions, wherever required.
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Hildebrand, J., G. Baumgarten, J. Fiedler, U. P. Hoppe, B. Kaifler, F. J. Lübken, and B. P. Williams. "Combined wind measurements by two different lidar instruments in the Arctic middle atmosphere." Atmospheric Measurement Techniques Discussions 5, no. 3 (June 12, 2012): 4123–56. http://dx.doi.org/10.5194/amtd-5-4123-2012.
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Abstract. During a joint campaign in January 2009 the Rayleigh/Mie/Raman (RMR) lidar and the sodium lidar at the ALOMAR Observatory (69° N, 16° E) in Northern Norway were operated simultaneously for more than 40 h, collecting data for wind measurements in the middle atmosphere from 30 up to 110 km altitude. At the upper (lower) altitude range where the RMR (sodium) lidar can operate, both lidars probe the same sounding volume, allowing to compare the derived wind speeds. We present the first simultaneous common volume wind measurements in the middle atmosphere using two different lidar instruments. The comparison of winds derived by RMR and sodium lidar is excellent for long integration times of 10 h as well as shorter ones of 1 h. Combination of data from both lidars allows identifying wavy structures between 30 and 110 km altitude, whose amplitudes increase with height. We have also performed lidar measurements of the same wind component using two independent branches of the RMR lidar and found a good agreement of the results but also identified inhomogeneities in the horizontal wind at about 55 km altitude of up to 20 ms−1. Such small scale inhomogeneities in the horizontal wind field are an essential challenge when comparing data from different instruments.
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Hildebrand, Jens, Gerd Baumgarten, Jens Fiedler, and Franz-Josef Lübken. "Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar." Atmospheric Chemistry and Physics 17, no. 21 (November 10, 2017): 13345–59. http://dx.doi.org/10.5194/acp-17-13345-2017.
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Abstract. We present an extensive data set of simultaneous temperature and wind measurements in the Arctic middle atmosphere. It consists of more than 300 h of Doppler Rayleigh lidar observations obtained during three January seasons (2012, 2014, and 2015) and covers the altitude range from 30 km up to about 85 km. The data set reveals large year-to-year variations in monthly mean temperatures and winds, which in 2012 are affected by a sudden stratospheric warming. The temporal evolution of winds and temperatures after that warming are studied over a period of 2 weeks, showing an elevated stratopause and the reformation of the polar vortex. The monthly mean temperatures and winds are compared to data extracted from the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Horizontal Wind Model (HWM07). Lidar and ECMWF data show good agreement of mean zonal and meridional winds below ≈ 55 km altitude, but we also find mean temperature, zonal wind, and meridional wind differences of up to 20 K, 20 m s−1, and 5 m s−1, respectively. Differences between lidar observations and HWM07 data are up to 30 m s−1. From the fluctuations of temperatures and winds within single nights we extract the potential and kinetic gravity wave energy density (GWED) per unit mass. It shows that the kinetic GWED is typically 5 to 10 times larger than the potential GWED, the total GWED increases with altitude with a scale height of ≈ 16 km. Since temporal fluctuations of winds and temperatures are underestimated in ECMWF, the total GWED is underestimated as well by a factor of 3–10 above 50 km altitude. Similarly, we estimate the energy density per unit mass for large-scale waves (LWED) from the fluctuations of nightly mean temperatures and winds. The total LWED is roughly constant with altitude. The ratio of kinetic to potential LWED varies with altitude over 2 orders of magnitude. LWEDs from ECMWF data show results similar to the lidar data. From the comparison of GWED and LWED, it follows that large-scale waves carry about 2 to 5 times more energy than gravity waves.
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Gkiolas, Dimitris, Demetri Yiasemides, and Demetri Mathioulakis. "Experimental study of a pitching and plunging wing." Aircraft Engineering and Aerospace Technology 90, no. 7 (October 1, 2018): 1136–44. http://dx.doi.org/10.1108/aeat-01-2017-0049.
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Purpose The complex flow behavior over an oscillating aerodynamic body, e.g. a helicopter rotor blade, a rotating wind turbine blade or the wing of a maneuvering airplane involves combinations of pitching and plunging motions. As the parameters of the problem (Re, St and phase difference between these two motions) vary, a quasi-steady analysis fails to provide realistic results for the aerodynamic response of the moving body, whereas this study aims to provide reliable experimental data. Design/methodology/approach In the present study, a pitching and plunging mechanism was designed and built in a subsonic closed-circuit wind tunnel as well as a rectangular aluminum wing of a 2:1 aspect-ratio with a NACA64-418 airfoil, used in wind turbine blades. To measure the pressure distribution along the wing chord, a number of fast responding transducers were embedded into the mid span wing surface. Simultaneous pressure measurements were conducted along the wing chord for the Reynolds number of 0.85 × 106 for both steady and unsteady cases (pitching and plunging). A flow visualization technique was used to detect the flow separation line under steady conditions. Findings Elevated pressure fluctuations coincide with the flow separation line having been detected through surface flow visualization and flattened pressure distributions appear downstream of the flow separation line. Closed hysteresis loops of the lift coefficient versus angle of attack were measured for combined pitching and plunging motions. Practical implications The experimental data can be used for improvement of unsteady fluid mechanics problem solvers. Originality/value In the present study, a new installation was built allowing the aerodynamic study of oscillating wings performing pitching and plunging motions with prescribed frequencies and phase lags between the two motions. The experimental data can be used for improvement of computational fluid dynamics codes in case that the examined aerodynamic body is oscillating.
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Draper, D. W., and D. G. Long. "Simultaneous wind and rain retrieval using SeaWinds data." IEEE Transactions on Geoscience and Remote Sensing 42, no. 7 (July 2004): 1411–23. http://dx.doi.org/10.1109/tgrs.2004.830169.
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Castro Fo, Belmiro Mendes de. "Wind driven currents in the channel of São Sebastião: winter, 1979." Boletim do Instituto Oceanográfico 38, no. 2 (1990): 111–32. http://dx.doi.org/10.1590/s0373-55241990000200002.
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Simultaneous 40 h low-passed wind, current and sea level data in the Channel of São Sebastião (CSS) and atmospheric pressure and sea level data in the South Brazil Bight (SBB) during winter of 1979 were analysed and compared. Currents in the CSS were predominantly northeastward, associated with frontal southerly winds. Current reversals occurred between meteorological disturbance passages. There were significant correlation between alongchannel components of wind and current, with a time lag of 12-18 h, wind leading; and between alongchannel component of current and sea level, with a time lag of 6-12 h, current leading. Most of the variance in the CSS series is concentrated in two frequency bands: 11-16 d and 3 d. SBB series also show high variance in those two bands. Coherences in those two bands show significant values when calculated between alongchannel components of wind and current, and sea level, in the CSS. Those three last signals were almost in phase in the 11-16 d band; and there was a lead of 16 h (25 h) by wind over current (sea level) in the 3 d band. There are several indications that in die subtidal band currents in the CSS are not totally locally forced.
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Calderón-Vega, Felícitas, Adrián-David García-Soto, and César Mösso. "Correlation of Concurrent Extreme Metocean Hazards Considering Seasonality." Applied Sciences 10, no. 14 (July 13, 2020): 4794. http://dx.doi.org/10.3390/app10144794.
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Simultaneous occurrence of metocean variables can present a multihazard to maritime systems. However, simplified design approaches to assess simultaneous significant wave heights and wind velocities are lacking, especially if seasonality is considered. This is addressed in this study by using extreme significant wave heights and companion wind velocities recorded in the Gulf of Mexico. Time-dependent, generalized extreme value (GEV) models and classical regression are the basis to propose a simplified approach to estimate correlated extreme significant wave heights and wind velocities associated with given return periods, accounting for seasonality and including measures of uncertainty. It is found that the proposed approach is a new but simple method to adequately characterize the concurrent extreme metocean variables and their uncertainty. It is concluded that the method is an effective probabilistic design tool to determine simultaneous extreme significant wave heights and companion wind velocities for desired return periods and seasonality.
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Zu, Gongbo, and Kit Ming Lam. "Simultaneous measurement of wind velocity field and wind forces on a square tall building." Advances in Structural Engineering 21, no. 15 (May 7, 2018): 2241–58. http://dx.doi.org/10.1177/1369433218770822.
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Vortex shedding from a tall building is known to be responsible for the quasi-periodic across-wind force exerted on the building. This article unveils the exact relationship between the vortex shedding pattern and the fluctuating across-wind force. Simultaneous particle-image velocimetry and pressure measurements are carried out on a square-plan tall building model in the wind tunnel toward an understanding of the velocity–pressure–force relation for across-wind force generation on the building. A collection of instantaneous wind flow patterns and synchronized wind pressure distributions suggests the existence of full periods of vortex shedding from the building. The results are further analyzed using the conditional sampling method by which the roles of development and shedding of large-scale vortices in the building wake on the generation of peak across-wind forces are evidently found. Furthermore, quasi-periodicity of across-wind excitation is clearly confirmed with Hilbert transform of the across-wind force signal. The phase averaging technique is applied to the particle-image velocimetry flow fields and distinct vortex shedding patterns from the building are observed for most of the measurement time, together with an evident phase relationship with the across-wind forces.
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Tobalske, B., and K. Dial. "Flight kinematics of black-billed magpies and pigeons over a wide range of speeds." Journal of Experimental Biology 199, no. 2 (February 1, 1996): 263–80. http://dx.doi.org/10.1242/jeb.199.2.263.
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To investigate how birds that differ in morphology change their wing and body movements while flying at a range of speeds, we analyzed high-speed (60 Hz) video tapes of black-billed magpies (Pica pica) flying at speeds of 4-14 m s-1 and pigeons (Columba livia) flying at 6-20 m s-1 in a wind-tunnel. Pigeons had higher wing loading and higher-aspect-ratio wings compared with magpies. Both species alternated phases of steady-speed flight with phases of acceleration and deceleration, particularly at intermediate flight speeds. The birds modulated their wingbeat kinematics among these phases and frequently exhibited non-flapping phases while decelerating. Such modulation in kinematics during forward flight is typical of magpies but not of pigeons in the wild. The behavior of the pigeons may have been a response to the reduced power costs for flight in the closed wind-tunnel relative to those for free flight at similar speeds. During steady-speed flight, wingbeat frequency did not change appreciably with increasing flight speed. Body angle relative to the horizontal, the stroke-plane angles of the wingtip and wrist relative to the horizontal and the angle describing tail spread at mid-downstroke all decreased with increasing flight speed, thereby illustrating a shift in the dominant function of wing flapping from weight support at slow speeds to positive thrust at fast speeds. Using wingbeat kinematics to infer lift production, it appeared that magpies used a vortex-ring gait during steady-speed flight at all speeds whereas pigeons used a vortex-ring gait at 6 and 8 m s-1, a transitional vortex-ring gait at 10 m s-1, and a continuous-vortex gait at faster speeds. Both species used a vortex-ring gait for acceleration and a continuous-vortex gait or a non-flapping phase for deceleration during flight at intermediate wind-tunnel speeds. Pigeons progressively flexed their wings during glides as flight speed increased but never performed bounds. Wingspan during glides in magpies did not vary with flight speed, but the percentage of bounds among non-flapping intervals increased with speed from 10 to 14 m s-1. The use of non-flapping wing postures seemed to be related to the gaits used during flapping and to the aspect ratio of the wings. We develop an 'adverse-scaling' hypothesis in which it is proposed that the ability to reduce metabolic and mechanical power output using flap-bounding flight at fast flight speeds is scaled negatively with body mass. This represents an alternative to the 'fixed-gear' hypothesis previously suggested by other authors to explain the use of intermittent flight in birds. Future comparative studies in the field would be worthwhile, especially if instantaneous flight speeds and within-wingbeat kinematics were documented; new studies in the laboratory should involve simultaneous recording of wing kinematics and aerodynamic forces on the wing.
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Rokade, M. V., R. Kondala Rao, S. S. Nikte, R. N. Ghodpage, P. T. Patil, A. K. Sharma, and S. Gurubaran. "Intraseasonal oscillation (ISO) in the MLT zonal wind over Kolhapur (16.8° N) and Tirunelveli (8.7° N)." Annales Geophysicae 30, no. 12 (December 5, 2012): 1623–31. http://dx.doi.org/10.5194/angeo-30-1623-2012.
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Abstract. Simultaneous observations of the mean zonal winds at 88 km obtained by the medium-frequency (MF) radars at Kolhapur (16.8° N, 74.2° E) and Tirunelveli (8.7° N, 77.8° E) have been used to study the intraseasonal oscillation (ISO) in the MLT region. The influences of the intraseasonal variations in the lower tropospheric convective activity associated with the Madden-Julian oscillations on the latitudinal behavior of intraseasonal oscillations (ISO) of the zonal winds in the equatorial mesosphere and lower thermosphere (MLT) have been studied. The ISO activity in the lower tropospheric convective activity is examined by employing outgoing long wave radiation (OLR) as a proxy for deep convective activity occurring in the tropical lower atmosphere. The ISO activity in the zonal wind over TIR is more correlated with that in the convective activity compared to the ISO over KOL. The latitudinal and temporal variabilities of the ISO in MLT zonal winds are explained in terms of the intraseasonal variabilities in the convective activity.
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danok, Suaad, Kamal Twfek, and Esraa Mansour. "Theoretical and Experimental Analysis for Performance of Wind Turbine." Tikrit Journal of Engineering Sciences 27, no. 4 (December 20, 2020): 114–20. http://dx.doi.org/10.25130/tjes.27.4.12.
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This research depends on carrying out an applied and numerical analysis for capability to utilize winds turbines which considered as means of renewable and friendly energy to environment, and how to make use of this technology to generate electric energy in Kirkuk city. Where it was studied shifting kinetic energy of winds into mechanic energy and has been accomplishes install a horizontal-turbine in one of work sites in Kirkuk city of (16m) height of the ground level. It has tri-blades of (400W) power. It has been connected to an electric system supply designed and manufacture during the research period. In order to measure the voltage-difference and electric current consequently to measure the power and energy produced from the wind turbine and changed according to the wind speed alteration. Gauge records for two time seasons are taken by using the technology-programming of delicate controller in simultaneous work with meteorological system, so that it can set data-principle to be analyzed by using (MATLAB) program to find and check theoretical generated power compared with practical results and find the range of validity to generate the sufficient energy for domestic consumption. The results shows that summer season is better than winter season in using wind turbine in Kirkuk city. As the monthly energy rate produce during summer season has emerged to ten-time than monthly energy rate produced during winter season.
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Mehrens, Anna Rieke, and Lueder von Bremen. "On the correlation of spatial wind speed and solar irradiance variability above the North Sea." Advances in Science and Research 13 (April 12, 2016): 57–61. http://dx.doi.org/10.5194/asr-13-57-2016.
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Abstract. Mesoscale wind fluctuations on a time scale of tens of minutes to several hours lead to high wind power fluctuations. Enhanced mesoscale wind variability emerges during cold air outbreaks and resulting cellular convection. The study investigates spatial wind and solar variability and their correlation during cellular convection. Cellular convection leads to simultaneous high solar and wind variability, but the highest solar or wind variability occurs due to other meteorological phenomena.
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Hildebrand, J., G. Baumgarten, J. Fiedler, U. P. Hoppe, B. Kaifler, F. J. Lübken, and B. P. Williams. "Combined wind measurements by two different lidar instruments in the Arctic middle atmosphere." Atmospheric Measurement Techniques 5, no. 10 (October 19, 2012): 2433–45. http://dx.doi.org/10.5194/amt-5-2433-2012.
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Abstract. During a joint campaign in January 2009, the Rayleigh/Mie/Raman (RMR) lidar and the sodium lidar at the ALOMAR Observatory (69° N, 16° E) in Northern Norway were operated simultaneously for more than 40 h, collecting data for wind measurements in the middle atmosphere from 30 up to 110 km altitude. As both lidars share the same receiving telescopes, the upper altitude range of the RMR lidar and the lower altitude range of the sodium lidar overlap in the altitude region of ≈80–85 km. For this overlap region we are thus able to present the first simultaneous wind measurements derived from two different lidar instruments. The comparison of winds derived by RMR and sodium lidar is excellent for long integration times of 10 h as well as shorter ones of 1 h. Combination of data from both lidars allows identifying wavy structures between 30 and 110 km altitude, whose amplitudes increase with height. We have also performed vertical wind measurements and measurements of the same horizontal wind component using two independent lasers and telescopes of the RMR lidar and show how to use this data to calibrate and validate the wind retrieval. For the latter configuration we found a good agreement of the results but also identified inhomogeneities in the horizontal wind at about 55 km altitude of up to 20 ms−1 for an integration time of nearly 4 h. Such small-scale inhomogeneities in the horizontal wind field are an essential challenge when comparing data from different instruments.
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Tamura, Y., K. Suda, A. Sasaki, K. Miyashita, Y. Iwatani, T. Maruyama, K. Hibi, and R. Ishibashi. "Simultaneous wind measurements over two sites using Doppler sodars." Journal of Wind Engineering and Industrial Aerodynamics 89, no. 14-15 (December 2001): 1647–56. http://dx.doi.org/10.1016/s0167-6105(01)00149-0.
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Nie, Congling, and David G. Long. "A C-Band Scatterometer Simultaneous Wind/Rain Retrieval Method." IEEE Transactions on Geoscience and Remote Sensing 46, no. 11 (November 2008): 3618–31. http://dx.doi.org/10.1109/tgrs.2008.922146.
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Gonzalez, N., A. Hauchecorne, S. Kirkwood, F. J. Lübken, A. H. Manson, A. Mourier, F. J. Schmidlin, et al. "Intelcomparisons of simultaneous remote and in situ wind measurements." Journal of Atmospheric and Terrestrial Physics 56, no. 13-14 (November 1994): 1985–2001. http://dx.doi.org/10.1016/0021-9169(94)90024-8.
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Silva-Leon, Jorge, Andrea Cioncolini, Mostafa R. A. Nabawy, Alistair Revell, and Andrew Kennaugh. "Simultaneous wind and solar energy harvesting with inverted flags." Applied Energy 239 (April 2019): 846–58. http://dx.doi.org/10.1016/j.apenergy.2019.01.246.
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Söderholm, Patrik, and Ger Klaassen. "Wind Power in Europe: A Simultaneous Innovation–Diffusion Model." Environmental and Resource Economics 36, no. 2 (October 6, 2006): 163–90. http://dx.doi.org/10.1007/s10640-006-9025-z.
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Pechlivanoglou, G., C. N. Nayeri, and C. O. Paschereit. "Performance Optimization of Wind Turbine Rotors with Active Flow Control (Part 1)." Mechanical Engineering 134, no. 04 (April 1, 2012): 51. http://dx.doi.org/10.1115/1.2012-apr-8.
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This article describes the performance optimization of wind turbine rotors with active flow control. The active Gurney flap concept was tested in the wind tunnel under dynamic AoA variations to simulate unsteady inflow conditions. A high-deflection micro flap was actuated by four digital electric servos with a maximum deflection rate of 360°/sec. A custom code was created to allow dynamic AoA variations of the test wing with simultaneous dynamic force measurements. During the dynamic investigations, various control strategies were tested, starting from standard PID controllers with semi-empirical parameter tuning models to Direct Inverse Controllers with neural network tuning strategies and pure self-learning neural network controllers. The results of the closed-loop measurements using the manually tuned PID controller showed a reduction potential for the dynamic lift loads in the range of 70% as well as a stable controller behavior. The Direct Inverse Controller not only showed a load reduction of 36.8%, but also significant improvement potential with respect to its fine-tuning.
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Pant, T. K., D. Tiwari, S. Sridharan, R. Sridharan, S. Gurubaran, K. S. V. Subbarao, and R. Sekar. "Evidence for direct solar control of the mesopause dynamics through dayglow and radar measurements." Annales Geophysicae 22, no. 9 (September 23, 2004): 3299–303. http://dx.doi.org/10.5194/angeo-22-3299-2004.
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Abstract. The day-to-day measurements of the daytime intensities of hydroxyl (OH) Meinel (8-3) band airglow emissions at 731.6 and 740.2nm carried out from the equatorial station Thiruvananthapuram (8.5° N, 76.5° E, 0.5° dip) during the period of January-March 2001 have been investigated. This investigation provides evidence for the presence of a long period (≈16 days) wave modulating these intensities at the mesopause altitudes. Simultaneous radar measurements of zonal wind at ~87km, i.e. mesopause from Tirunelveli (8.7° N, 77.8° E, 0.33° dip), a location nearby, also reveal the presence of these long period oscillations. The daytime airglow and zonal wind undergo changes simultaneously. Similar modulations are seen in the solar 10.7cm flux also preceding dayglow and wind variabilities by 4-5 days. It is inferred in the present case that the changes in the solar flux are the cause of the generation of this long period wave in the atmosphere below the mesosphere. The oscillations in the measured dayglow intensities in the mesopause region and the winds at ~87km are resulting from the modulation caused by this wave in this region after a delay of 4-5 days.
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Yan, Qiushuang, Chenqing Fan, Jie Zhang, and Junmin Meng. "Understanding Ku-Band Ocean Radar Backscatter at Low Incidence Angles under Weak to Severe Wind Conditions by Comparison of Measurements and Models." Remote Sensing 12, no. 20 (October 20, 2020): 3445. http://dx.doi.org/10.3390/rs12203445.
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The rain-free normalized radar cross-section (NRCS) measurements from the Ku-band precipitation radars (PRs) aboard the tropical rainfall measuring mission (TRMM) and the global precipitation measurement (GPM) mission, along with simultaneous sea surface wind truth from buoy observations, stepped-frequency microwave radiometer (SFMR) measurements, and H*Wind analyses, are used to investigate the abilities of the quasi-specular scattering models, i.e., the physical optics model (PO) and the classical and improved geometrical optics models (GO and GO4), to reproduce the Ku-band NRCS at low incidence angles of 0–18° over the wind speed range of 0–45 m/s. On this basis, the limitations of the quasi-specular scattering theory and the effects of wave breaking are discussed. The results show that the return caused by quasi-specular reflection is affected significantly by the presence of background swell waves at low winds. At moderate wind speeds of 5–15 m/s, the NRCS is still dominated by the quasi-specular reflection, and the wave breaking starts to work but its contribution is very small, thus, the models are found in excellent agreement with the measurements. With wind speed increasing, the impact of wave breaking increases, whereas the role of standard quasi-specular reflection decreases. The wave breaking impact on NRCS is first visible at incidence angles near 18° as wind speed exceeds about 20 m/s, then it becomes dominant when wind speed exceeds about 37 m/s where the NRCS is insensitive to wind speed and depends linearly on incidence angle, which cannot be explained by the standard quasi-specular scattering theory.
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Edberg, N. J. T., U. Auster, S. Barabash, A. Bößwetter, D. A. Brain, J. L. Burch, C. M. Carr, et al. "Rosetta and Mars Express observations of the influence of high solar wind pressure on the Martian plasma environment." Annales Geophysicae 27, no. 12 (December 17, 2009): 4533–45. http://dx.doi.org/10.5194/angeo-27-4533-2009.
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Abstract. 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.
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Jauch, Clemens, and Arne Gloe. "Simultaneous Inertia Contribution and Optimal Grid Utilization with Wind Turbines." Energies 12, no. 15 (August 5, 2019): 3013. http://dx.doi.org/10.3390/en12153013.
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This paper presents findings of a study on continuous feed-in management and continuous synthetic inertia contribution with wind turbines. A realistic case study, based on real measurements, is outlined. A wind turbine feeds into a weak feeder, such that its power has to be adapted to the permissible loading of this feeder. At the same time the wind turbine is to provide inertia to the grid by applying the previously published variable inertia constant controller. It is discussed that optimal grid utilization and simultaneous inertia contribution are mandatory for the frequency control in power systems that are heavily penetrated with renewable energies. The study shows that continuous feed-in management can be combined well with continuous inertia provision. There are hardly any negative consequences for the wind turbine. The benefits for the grid are convincing, both in terms of increased system utilization and in terms of provided inertia. It is concluded that wind turbines can enhance angular stability in a power system to a larger extent than conventional power plants.
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Mahjabin, Tanziha, Charitha Pattiaratchi, Yasha Hetzel, and Ivica Janekovic. "Spatial and Temporal Variability of Dense Shelf Water Cascades along the Rottnest Continental Shelf in Southwest Australia." Journal of Marine Science and Engineering 7, no. 2 (February 1, 2019): 30. http://dx.doi.org/10.3390/jmse7020030.
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Along the majority of Australian shallow coastal regions, summer evaporation increases the salinity of shallow waters, and subsequently in autumn/winter, the nearshore waters become cooler due to heat loss. This results in the formation of horizontal density gradients with density increasing toward the coast that generates gravity currents known as dense shelf water cascades (DSWCs) flowing offshore along the sea bed. DSWCs play important role in ecological and biogeochemical processes in Australian waters through the transport of dissolved and suspended materials offshore. In this study a numerical ocean circulation model of Rottnest continental shelf, validated using simultaneous ocean glider and mooring data, indicated that the passage of cold fronts associated with winter storms resulted in rapid heat loss through evaporative cooling. These conditions resulted in enhancement of the DSWCs due to modifications of the cross-shelf density gradient and wind effects. Specifically, onshore (offshore) directed winds resulted in an enhancement (inhibition) of DSWCs due to downwelling (vertical mixing). Consequently, the largest DSWC events occurred during the cold fronts when atmospheric temperatures reinforced density gradients and onshore winds promoted downwelling that enhanced DSWCs. Advection of DSWCs was also strongly influenced by the wind conditions, with significantly more transport occurring along-shelf compared to cross-shelf.
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Smith, Vanessa, and Hussam Mahmoud. "Multihazard Assessment of Wind Turbine Towers under Simultaneous Application of Wind, Operation, and Seismic Loads." Journal of Performance of Constructed Facilities 30, no. 6 (December 2016): 04016043. http://dx.doi.org/10.1061/(asce)cf.1943-5509.0000898.
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Semedo, Alvaro, Øyvind Saetra, Anna Rutgersson, Kimmo K. Kahma, and Heidi Pettersson. "Wave-Induced Wind in the Marine Boundary Layer." Journal of the Atmospheric Sciences 66, no. 8 (August 1, 2009): 2256–71. http://dx.doi.org/10.1175/2009jas3018.1.
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Abstract Recent field observations and large-eddy simulations have shown that the impact of fast swell on the marine atmospheric boundary layer (MABL) might be stronger than previously assumed. For low to moderate winds blowing in the same direction as the waves, swell propagates faster than the mean wind. The momentum flux above the sea surface will then have two major components: the turbulent shear stress, directed downward, and the swell-induced stress, directed upward. For sufficiently high wave age values, the wave-induced component becomes increasingly dominant, and the total momentum flux will be directed into the atmosphere. Recent field measurements have shown that this upward momentum transfer from the ocean into the atmosphere has a considerable impact on the surface layer flow dynamics and on the turbulence structure of the overall MABL. The vertical wind profile will no longer exhibit a logarithmic shape because an acceleration of the airflow near the surface will take place, generating a low-level wave-driven wind maximum (a wind jet). As waves propagate away from their generation area as swell, some of the wave momentum will be returned to the atmosphere in the form of wave-driven winds. A model that qualitatively reproduces the wave-following atmospheric flow and the wave-generated wind maximum, as seen from measurements, is proposed. The model assumes a stationary momentum and turbulent kinetic energy balance and uses the dampening of the waves at the surface to describe the momentum flux from the waves to the atmosphere. In this study, simultaneous observations of wind profiles, turbulent fluxes, and wave spectra during swell events are presented and compared with the model. In the absence of an established model for the linear damping ratio during swell conditions, the model is combined with observations to estimate the wave damping. For the cases in which the observations showed a pronounced swell signal and almost no wind waves, the agreement between observed and modeled wind profiles is remarkably good. The resulting attenuation length is found to be relatively short, which suggests that the estimated damping ratios are too large. The authors attribute this, at least partly, to processes not accounted for by the model, such as the existence of an atmospheric background wind. In the model, this extra momentum must be supplied by the waves in terms of a larger damping ratio.
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Rodríguez, Ernesto, Alexander Wineteer, Dragana Perkovic-Martin, Tamás Gál, Steven Anderson, Seth Zuckerman, James Stear, and Xiufeng Yang. "Ka-Band Doppler Scatterometry over a Loop Current Eddy." Remote Sensing 12, no. 15 (July 24, 2020): 2388. http://dx.doi.org/10.3390/rs12152388.
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Doppler scatterometry is a promising new technique for the simultaneous measurement of ocean surface currents and winds. These measurements have been recommended by the recent US NRC Decadal Review for NASA as being priority variables for the coming decade of Earth observations. In addition, currents and winds are useful for many applications, including assessing the operating conditions for oil platforms or tracking the dispersal of plastic or oil by surface currents and winds. While promising, Doppler scatterometry is relatively new and understanding the measurement characteristics is an important area of research. To this end, Chevron sponsored the deployment of DopplerScatt, a NASA/JPL Ka-band Doppler scatterometer, over instrumented sites located at the edge of a Gulf of Mexico Loop Current Eddy (LCE). In addition to in situ measurements, coincident synoptic maps of surface currents were collected by the Areté ROCIS instrument, an optical current measurement system. Here we report on the results of this experiment for both surface currents and winds. Surface current comparisons show that the Ka-band Current Geophysical Model Function (CGMF) needs to include wind drift currents, which could not be estimated with prior data sets. Once the CGMF is updated, ROCIS and DopplerScatt show good agreement for surface current speeds, but, at times, direction differences on the order of 10° can occur. Remote sensing optical and radar data agree better among themselves than with ADCP currents measured at 5 m depth, showing that remote sensing is sensitive to the the currents in top 1 m of the ocean. The LCE data provided a unique opportunity to study the effects of surface currents and stability conditions on scatterometer winds. We show that, like Ku-band, Ka-band estimates of winds are related to neutral winds (and wind stress) and are referenced relative to the moving frame provided by the current. This is useful for the study of air-sea interactions, but must be accounted for when using scatterometer winds for weather prediction.
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Morris, M. P., P. B. Chilson, T. J. Schuur, and A. Ryzhkov. "Microphysical retrievals from simultaneous polarimetric and profiling radar observations." Annales Geophysicae 27, no. 12 (December 7, 2009): 4435–48. http://dx.doi.org/10.5194/angeo-27-4435-2009.
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Abstract. The character of precipitation detected at the surface is the final product of many microphysical interactions in the cloud above, the combined effects of which may be characterized by the observed drop size distribution (DSD). This necessitates accurate retrieval of the DSD from remote sensing data, especially radar as it offers large areal coverage, high spatial resolution, and rigorous quality control and testing. Combined instrument observations with a UHF wind profiler, an S-band polarimetric weather radar, and a video disdrometer are analyzed for two squall line events occuring during the calendar year 2007. UHF profiler Doppler velocity spectra are used to estimate the DSD aloft, and are complemented by DSDs retrieved from an exponential model applied to polarimetric data. Ground truth is provided by the disdrometer. A complicating factor in the retrieval from UHF profiler spectra is the presence of ambient air motion, which can be corrected using the method proposed by Teshiba et al. (2009), in which a comparison between idealized Doppler spectra calculated from the DSDs retrieved from KOUN and those retrieved from contaminated wind profiler spectra is performed. It is found that DSDs measured using the distrometer at the surface and estimated using the wind profiler and polarimetric weather radar generally showed good agreement. The DSD retrievals using the wind profiler were improved when the estimates of the vertical wind were included into the analysis, thus supporting the method of Teshiba et al. (2009). Furthermore, the the study presents a method of investigating the time and height structure of DSDs.
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Bageston, J. V., C. M. Wrasse, P. P. Batista, R. E. Hibbins, D. C Fritts, D. Gobbi, and V. F. Andrioli. "Observation of a mesospheric front in a thermal-doppler duct over King George Island, Antarctica." Atmospheric Chemistry and Physics 11, no. 23 (December 7, 2011): 12137–47. http://dx.doi.org/10.5194/acp-11-12137-2011.
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Abstract. A mesospheric front was observed with an all-sky airglow imager on the night of 9–10 July 2007 at Ferraz Station (62° S, 58° W), located on King George island on the Antarctic Peninsula. The observed wave propagated from southwest to northeast with a well defined wave front and a series of crests behind the main front. The wave parameters were obtained via a 2-D Fourier transform of the imager data providing a horizontal wavelength of 33 km, an observed period of 6 min, and a horizontal phase speed of 92 m s−1. Simultaneous mesospheric winds were measured with a medium frequency (MF) radar at Rothera Station (68° S, 68° W) and temperature profiles were obtained from the SABER instrument on the TIMED satellite. These wind and temperature profiles were used to estimate the propagation environment of the wave event. A wavelet technique was applied to the wind in the plane of wave propagation at the OH emission height spanning three days centered on the front event to define the dominant periodicities. Results revealed a dominance of near-inertial periods, and semi-diurnal and terdiurnal tides suggesting that the ducting structure enabling mesospheric front propagation occurred on large spatial scales. The observed tidal motions were used to reconstruct the winds employing a least-squares method, which were then compared to the observed ducting environment. Results suggest an important contribution of large-scale winds to the ducting structure, but with buoyancy frequency variations in the vertical also expected to be important. These results allow us to conclude that the wave front event was supported by a duct including contributions from both winds and temperature.
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Vasiljević, Nikola, Michael Harris, Anders Tegtmeier Pedersen, Gunhild Rolighed Thorsen, Mark Pitter, Jane Harris, Kieran Bajpai, and Michael Courtney. "Wind sensing with drone-mounted wind lidars: proof of concept." Atmospheric Measurement Techniques 13, no. 2 (February 7, 2020): 521–36. http://dx.doi.org/10.5194/amt-13-521-2020.
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Abstract. The fusion of drone and wind lidar technology introduces the exciting possibility of performing high-quality wind measurements virtually anywhere. We present a proof-of-concept (POC) drone–lidar system and report results from several test campaigns that demonstrate its ability to measure accurate wind speeds. The POC system is based on a dual-telescope continuous-wave (CW) lidar, with drone-borne telescopes and ground-based optoelectronics. Commercially available drone and gimbal units are employed. The demonstration campaigns started with a series of comparisons of the wind speed measurements acquired by the POC system to simultaneous measurements performed by nearby mast-based sensors. On average, an agreement down to about 0.1 m s−1 between mast- and drone-based measurements of the horizontal wind speed is found. Subsequently, the extent of the flow disturbance caused by the drone downwash was investigated. These tests vindicated the somewhat conservative choice of lidar measurement ranges made for the initial wind speed comparisons. Overall, the excellent results obtained without any drone motion correction and with fairly primitive drone position control indicate the potential of drone–lidar systems in terms of accuracy and applications. The next steps in the development are outlined and several potential applications are discussed.
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Damineli, A., M. Teodoro, N. D. Richardson, T. R. Gull, M. F. Corcoran, K. Hamaguchi, J. H. Groh, et al. "The wind-wind collision hole in eta Car." Proceedings of the International Astronomical Union 12, S329 (November 2016): 186–90. http://dx.doi.org/10.1017/s1743921317002630.
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AbstractEta Carinae is one of the most massive observable binaries. Yet determination of its orbital and physical parameters is hampered by obscuring winds. However the effects of the strong, colliding winds changes with phase due to the high orbital eccentricity. We wanted to improve measures of the orbital parameters and to determine the mechanisms that produce the relatively brief, phase-locked minimum as detected throughout the electromagnetic spectrum. We conducted intense monitoring of the He ii λ4686 line in η Carinae for 10 months in the year 2014, gathering ~300 high S/N spectra with ground- and space-based telescopes. We also used published spectra at the FOS4 SE polar region of the Homunculus, which views the minimum from a different direction. We used a model in which the He ii λ4686 emission is produced by two mechanisms: a) one linked to the intensity of the wind-wind collision which occurs along the whole orbit and is proportional to the inverse square of the separation between the companion stars; and b) the other produced by the ‘bore hole’ effect which occurs at phases across the periastron passage. The opacity (computed from 3D SPH simulations) as convolved with the emission reproduces the behavior of equivalent widths both for direct and reflected light. Our main results are: a) a demonstration that the He ii λ4686 light curve is exquisitely repeatable from cycle to cycle, contrary to previous claims for large changes; b) an accurate determination of the longitude of periastron, indicating that the secondary star is ‘behind’ the primary at periastron, a dispute extended over the past decade; c) a determination of the time of periastron passage, at ~4 days after the onset of the deep light curve minimum; and d) show that the minimum is simultaneous for observers at different lines of sight, indicating that it is not caused by an eclipse of the secondary star, but rather by the immersion of the wind-wind collision interior to the inner wind of the primary.