Sample records for zonal wind speed

  1. Gravitational Anomalies Caused by Zonal Winds in Jupiter

    NASA Astrophysics Data System (ADS)

    Schubert, G.; Kong, D.; Zhang, K.

    2012-12-01

    We present an accurate three-dimensional non-spherical numerical calculation of the gravitational anomalies caused by zonal winds in Jupiter. The calculation is based on a three-dimensional finite element method and accounts for the full effect of significant departure from spherical geometry caused by rapid rotation. Since the speeds of Jupiter's zonal winds are much smaller than that of its rigid-body rotation, our numerical calculation is carried out in two stages. First, we compute the non-spherical distributions of density and pressure at the equilibrium within Jupiter via a hybrid inverse approach by determining an a priori unknown coefficient in the polytropic equation of state that results in a match to the observed shape of Jupiter. Second, by assuming that Jupiter's zonal winds extend throughout the interior along cylinders parallel to the rotation axis, we compute gravitational anomalies produced by the wind-related density anomalies, providing an upper bound to the gravitational anomalies caused by the Jovian zonal winds.

  2. Saturn’s gravitational field induced by its equatorially antisymmetric zonal winds

    NASA Astrophysics Data System (ADS)

    Kong, Dali; Zhang, Keke; Schubert, Gerald; Anderson, John D.

    2018-05-01

    The cloud-level zonal winds of Saturn are marked by a substantial equatorially antisymmetric component with a speed of about 50ms‑1 which, if they are sufficiently deep, can produce measurable odd zonal gravitational coefficients ΔJ 2k+1, k = 1, 2, 3, 4. This study, based on solutions of the thermal-gravitational wind equation, provides a theoretical basis for interpreting the odd gravitational coefficients of Saturn in terms of its equatorially antisymmetric zonal flow. We adopt a Saturnian model comprising an ice-rock core, a metallic dynamo region and an outer molecular envelope. We use an equatorially antisymmetric zonal flow that is parameterized, confined in the molecular envelope and satisfies the solvability condition required for the thermal-gravitational wind equation. The structure and amplitude of the zonal flow at the cloud level are chosen to be consistent with observations of Saturn. We calculate the odd zonal gravitational coefficients ΔJ 2k+1, k = 1, 2, 3, 4 by regarding the depth of the equatorially antisymmetric winds as a parameter. It is found that ΔJ 3 is ‑4.197 × 10‑8 if the zonal winds extend about 13 000 km downward from the cloud tops while it is ‑0.765 × 10‑8 if the depth is about 4000 km. The depth/profile of the equatorially antisymmetric zonal winds can eventually be estimated when the high-precision measurements of the Cassini Grand Finale become available.

  3. Thermal zonal winds in the Venus mesosphere from the Venus Express temperature soundings

    NASA Astrophysics Data System (ADS)

    Piccialli, Arianna; Titov, Dmitri; Tellmann, Silvia; Migliorini, Alessandra; Read, Peter; Grassi, Davide; Paetzold, Martin; Haeusler, Bernd; Piccioni, Giuseppe; Drossart, Pierre

    The Venus mesosphere (60-100 km altitude) is a transition region characterized by extremely complex dynamics: strong retrograde zonal winds dominate in the troposphere and lower meso-sphere while a solar-antisolar circulation can be observed in the upper mesosphere. The super-rotation extends from the surface up to the cloud top (˜65 km altitude) with wind speeds of only a few meters per second near the surface and reaching a maximum value of ˜100 m s-1 at cloud top, corresponding to a rotation period of ˜4 Earth days (˜60 times faster than Venus itself). The solar-antisolar circulation is driven by the day-night contrast in solar heating, and occurs above 110 km altitude with speeds of 120 m s-1 . The processes responsible for maintain-ing the zonal super-rotation in the lower atmosphere and its transition to the solar-antisolar circulation in the upper atmosphere are still poorly understood (Schubert et al.,2007). Different techniques have been used to obtain direct observations of wind at various altitudes: tracking of clouds in ultraviolet (UV) and near infrared (NIR) images give information on wind speeds at the cloud top (Moissl et al., 2009; Sanchez-Lavega et al., 2008) and within the clouds (˜47 km, ˜61 km) (Sanchez-Lavega et al., 2008) while ground-based measurements of Doppler shifts in the CO2 band at 10 µm (Sornig et al., 2008) and in several CO millimiter lines (Rengel et al., 2008) provide wind speeds above the clouds up to ˜110 km altitude. The deep atmosphere from the surface up to the cloud top has been investigated through the Doppler tracking of descent probes and balloons (Counselman et al., 1980; Kerzhanovich and Limaye, 1985). In the mesosphere, between 45-85 km of altitude, where direct observations of wind are not possible, the zonal wind field can be derived from the vertical temperature structure using a special approximation of the thermal wind equation: based on cyclostrophic balance. Previous studies (Leovy, 1973; Newman et al

  4. Changes in Jupiter's Zonal Wind Profile Preceding and During the Juno Mission

    NASA Technical Reports Server (NTRS)

    Tollefson, Joshua; Wong, Michael H.; de Pater, Imke; Simon, Amy A.; Orton, Glenn S.; Rogers, John H.; Atreya, Sushil K.; Cosentino, Richard G.; Januszewski, William; Morales-Juberias, Raul; hide

    2017-01-01

    We present five epochs of WFC3 HST Jupiter observations taken between 2009-2016 and extract global zonal wind profiles for each epoch. Jupiter's zonal wind field is globally stable throughout these years, but significant variations in certain latitude regions persist. We find that the largest uncertainties in the wind field are due to vortices or hot-spots, and show residual maps which identify the strongest vortex flows. The strongest year-to-year variation in the zonal wind profiles is the 24 deg N jet peak. Numerous plume outbreaks have been observed in the Northern Temperate Belt and are associated with decreases in the zonal velocity and brightness. We show that the 24 deg N jet peak velocity and brightness decreased in 2012 and again in late 2016, following outbreaks during these years. Our February 2016 zonal wind profile was the last highly spatially resolved measurement prior to Juno s first science observations. The final 2016 data were taken in conjunction with Juno's perijove 3 pass on 11 December 2016, and show the zonal wind profile following the plume outbreak at 24 deg N in October 2016.

  5. Zonal wind observations during a geomagnetic storm

    NASA Technical Reports Server (NTRS)

    Miller, N. J.; Spencer, N. W.

    1986-01-01

    In situ measurements taken by the Wind and Temperature Spectrometer (WATS) onboard the Dynamics Explorer 2 spacecraft during a geomagnetic storm display zonal wind velocities that are reduced in the corotational direction as the storm intensifies. The data were taken within the altitudes 275 to 475 km in the dusk local time sector equatorward of the auroral region. Characteristic variations in the value of the Dst index of horizontal geomagnetic field strength are used to monitor the storm evolution. The detected global rise in atmospheric gas temperature indicates the development of thermospheric heating. Concurrent with that heating, reductions in corotational wind velocities were measured equatorward of the auroral region. Just after the sudden commencement, while thermospheric heating is intense in both hemispheres, eastward wind velocities in the northern hemisphere show reductions ranging from 500 m/s over high latitudes to 30 m/s over the geomagnetic equator. After 10 hours storm time, while northern thermospheric heating is diminishing, wind velocity reductions, distinct from those initially observed, begin to develop over southern latitudes. In the latter case, velocity reductions range from 300 m/s over the highest southern latitudes to 150 m/s over the geomagnetic equator and extend into the Northern Hemisphere. The observations highlight the interhemispheric asymmetry in the development of storm effects detected as enhanced gas temperatures and reduced eastward wind velocities. Zonal wind reductions over high latitudes can be attributed to the storm induced equatorward spread of westward polar cap plasma convection and the resulting plasma-neutral collisions. However, those collisions are less significant over low latitudes; so zonal wind reductions over low latitudes must be attributed to an equatorward extension of a thermospheric circulation pattern disrupted by high latitude collisions between neutrals transported via eastward winds and ions

  6. The Galileo probe Doppler wind experiment: Measurement of the deep zonal winds on Jupiter

    NASA Astrophysics Data System (ADS)

    Atkinson, David H.; Pollack, James B.; Seiff, Alvin

    1998-09-01

    During its descent into the upper atmosphere of Jupiter, the Galileo probe transmitted data to the orbiter for 57.5 min. Accurate measurements of the probe radio frequency, driven by an ultrastable oscillator, allowed an accurate time history of the probe motions to be reconstructed. Removal from the probe radio frequency profile of known Doppler contributions, including the orbiter trajectory, the probe descent velocity, and the rotation of Jupiter, left a measurable frequency residual due to Jupiter's zonal winds, and microdynamical motion of the probe from spin, swing under the parachute, atmospheric turbulence, and aerodynamic buffeting. From the assumption of the dominance of the zonal horizontal winds, the frequency residuals were inverted and resulted in the first in situ measurements of the vertical profile of Jupiter's deep zonal winds. A number of error sources with the capability of corrupting the frequency measurements or the interpretation of the frequency residuals were considered using reasonable assumptions and calibrations from prelaunch and in-flight testing. It is found that beneath the cloud tops (about 700 mbar) the winds are prograde and rise rapidly to 170 m/s at 4 bars. Beyond 4 bars to the depth at which the link with the probe was lost, nearly 21 bars, the winds remain constant and strong. Corrections for the high temperatures encountered by the probe have recently been completed and provide no evidence of diminishing or strengthening of the zonal wind profile in the deeper regions explored by the Galileo probe.

  7. Periodical oscillation of zonal wind velocities at the cloud top of Venus

    NASA Astrophysics Data System (ADS)

    Kouyama, T.; Imamura, T.; Nakamura, M.; Satoh, T.; Futaana, Y.

    2010-12-01

    Zonal wind velocity of Venus increases with height and reaches about 100 m s-1 at the cloud top level (~70km). The speed is approximately 60 times faster than the rotation speed of the solid body of Venus (~1.6 m s-1, at the equator) and this phenomenon is called a "super-rotation". From previous observations, it is known that the super-rotation changes on a long timescale. At the cloud top level, it was suggested that the super-rotation has a few years period oscillation based on observations made by Pioneer Venus orbiter of USA from 1979 to 1985 (Del Genio et al.,1990). However, the period, the amplitude, the spatial structure and the mechanism of the long period oscillation have not been understood well. Venus Express (VEX) of European Space Agency has been observing Venus since its orbital insertion in April 2006. Venus Monitoring Camera (VMC) onboard VEX has an ultra violet (UV) filter (365 nm), and VMC has taken day-side cloud images at the cloud top level with this filter. Such images exhibit various cloud features made by unknown UV absorber in the atmosphere. For investigating the characteristics of long-timescale variations of the super-rotation, we analyzed zonal velocity fields derived from UV cloud images from May 2006 to January 2010 using a cloud tracking method. UV imaging of VMC is done when the spacecraft is in the ascending portion of its elongated polar orbit. Since the orbital plane is nearly fixed in the inertial space, the local time of VMC/UV observation changes with a periodicity of one Venus year. As a result, periods when VMC observation covered day-side areas of Venus, large enough for cloud trackings, are not continuous. For deriving wind velocities we were able to use cloud images taken in 280 orbits during this period. The derived zonal wind velocity from 10°S to 40°S latitude shows a prominent year-to-year variation, and the variation is well fitted by a periodical oscillation with a period of about 260 Earth days, although not all

  8. Nonstationary Gravity Wave Forcing of the Stratospheric Zonal Mean Wind

    NASA Technical Reports Server (NTRS)

    Alexander, M. J.; Rosenlof, K. H.

    1996-01-01

    The role of gravity wave forcing in the zonal mean circulation of the stratosphere is discussed. Starting from some very simple assumptions about the momentum flux spectrum of nonstationary (non-zero phase speed) waves at forcing levels in the troposphere, a linear model is used to calculate wave propagation through climatological zonal mean winds at solstice seasons. As the wave amplitudes exceed their stable limits, a saturation criterion is imposed to account for nonlinear wave breakdown effects, and the resulting vertical gradient in the wave momentum flux is then used to estimate the mean flow forcing per unit mass. Evidence from global, assimilated data sets are used to constrain these forcing estimates. The results suggest the gravity-wave-driven force is accelerative (has the same sign as the mean wind) throughout most of the stratosphere above 20 km. The sense of the gravity wave forcing in the stratosphere is thus opposite to that in the mesosphere, where gravity wave drag is widely believed to play a principal role in decelerating the mesospheric jets. The forcing estimates are further compared to existing gravity wave parameterizations for the same climatological zonal mean conditions. Substantial disagreement is evident in the stratosphere, and we discuss the reasons for the disagreement. The results suggest limits on typical gravity wave amplitudes near source levels in the troposphere at solstice seasons. The gravity wave forcing in the stratosphere appears to have a substantial effect on lower stratospheric temperatures during southern hemisphere summer and thus may be relevant to climate.

  9. Why the stratospheric zonal and meridional wind changes trend in the mid -1990s?

    NASA Astrophysics Data System (ADS)

    Krizan, P.

    2016-12-01

    This poster tries to explain the reasons for trend change of the stratospheric zonal and meridional wind in the mid-1990s. In the areas of negative (positive) wind speed trend before 1995 the positive (negative) trend is observed after this point Similar change is observed also for total ozone where we observe negative trend before 1995 and positive one after. We use MERRA reanalysis data especially monthly mean of geopotential from January to March. We suppose the position and strength of polar vortex and Aleutian high plays here very important role..

  10. Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed

    NASA Astrophysics Data System (ADS)

    Domeisen, Daniela I. V.; Martius, Olivia; Jiménez-Esteve, Bernat

    2018-02-01

    Sudden stratospheric warming (SSW) events are to a dominant part induced by upward propagating planetary waves. While theory predicts that the zonal phase speed of a tropospheric wave forcing affects wave propagation into the stratosphere, its relevance for SSW events has so far not been considered. This study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward, indicating that the stratosphere preselects eastward phase speeds for propagation, especially for zonal wave number 2. This also affects SSW events: Split SSW events tend to be preceded by anomalously eastward zonal phase speeds. Zonal phase speed may indeed explain part of the increased wave flux observed during the preconditioning of SSW events, as, for example, for the record 2009 SSW event.

  11. Ion Layer Separation and Equilibrium Zonal Winds in Midlatitude Sporadic E

    NASA Technical Reports Server (NTRS)

    Earle, G. D.; Kane, T. J.; Pfaff, R. F.; Bounds, S. R.

    2000-01-01

    In-situ observations of a moderately strong mid-latitude sporadic-E layer show a separation in altitude between distinct sublayers composed of Fe(+), Mg(+), and NO(+). From these observations it is possible to estimate the zonal wind field consistent with diffusive equilibrium near the altitude of the layer. The amplitude of the zonal wind necessary to sustain the layer against diffusive effects is less than 10 meters per second, and the vertical wavelength is less than 10 km.

  12. Longitudinal variability in Jupiter's zonal winds derived from multi-wavelength HST observations

    NASA Astrophysics Data System (ADS)

    Johnson, Perianne E.; Morales-Juberías, Raúl; Simon, Amy; Gaulme, Patrick; Wong, Michael H.; Cosentino, Richard G.

    2018-06-01

    Multi-wavelength Hubble Space Telescope (HST) images of Jupiter from the Outer Planets Atmospheres Legacy (OPAL) and Wide Field Coverage for Juno (WFCJ) programs in 2015, 2016, and 2017 are used to derive wind profiles as a function of latitude and longitude. Wind profiles are typically zonally averaged to reduce measurement uncertainties. However, doing this destroys any variations of the zonal-component of winds in the longitudinal direction. Here, we present the results derived from using a "sliding-window" correlation method. This method adds longitudinal specificity, and allows for the detection of spatial variations in the zonal winds. Spatial variations are identified in two jets: 1 at 17 ° N, the location of a prominent westward jet, and the other at 7 ° S, the location of the chevrons. Temporal and spatial variations at the 24°N jet and the 5-μm hot spots are also examined.

  13. On the wave forcing of the semi-annual zonal wind oscillation

    NASA Technical Reports Server (NTRS)

    Nagpal, O. P.; Raghavarao, R.

    1991-01-01

    Observational evidence of rather large period waves (23-60 d) in the troposphere/stratosphere, particularly during the winter months, is presented. Wind data collected on a regular basis employing high-altitude balloons and meteorological rockets over the past few years are used. Maximum entropy methods applied to the time series of zonal wind data indicate the presence of 23-60-waves more prominently than shorter-period waves. The waves have substantial amplitudes in the stratosphere and lower mesosphere, often larger than those noted in the troposphere. The mean zonal wind in the troposphere (5-15 km altitude) during December, January, and February exhibits the presence of strong westerlies at latitudes between 8 and 21 deg N.

  14. Trends in the Zonal Winds over the Southern Ocean from the NCEP/NCAR Reanalysis and Scatterometers

    NASA Astrophysics Data System (ADS)

    Richman, J. G.

    2002-12-01

    The winds over the Southern Ocean for the entire 54-year (1948-2001) period of the NCEP/NCAR Reanalysis have been decomposed into Principal Components (Empirical Orthogonal Functions). The first EOF describes 83 percent of the variance in the zonal wind. The loading of the EOF shows the predominately westerly surface flow with strongest winds in the Indian sector of the Southern Ocean. The structure of this EOF is similar to the Southern Annular Mode (SAM) identified by Thompson, et al 2000. The amplitude of this EOF reveals a large trend of 4.42 cm/s/yr in the strength of the zonal wind corresponding to a nearly 50 percent increase in the wind stress over the Southern Ocean. Such a trend, if real, would be important in the dynamics of the Antarctic Circumpolar Current (ACC). Recent studies by Gille, et al. (2001), Olbers and Ivchenko (2001) and Gent et al. (2001) have shown that the transport of the ACC is correlated to the variability in the zonal wind with a monotonic increase in the transport with increasing zonal wind strength. However, errors in the data assimilation scheme for surface pressure observations on the Antarctic continent appears to have caused a spurious trend in the sea level pressure south of 40S of -0.2 hPa/yr (Hines, et al. 2000 and Marshall, 2002). The sea level pressure difference between 40S and 60S has risen by 8 hPa over the same period. This sea level pressure difference is used as a proxy for the strength of the zonal winds. Thus, the trend in the zonal wind EOF amplitude may be an artifact of model errors in the NCEP Reanalysis. To check this trend, we analyzed scatterometer winds over the Southern Ocean from the SEASAT, ERS (1 and 2), NSCAT and QuikScat satellites. The scatterometer data is not used in the NCEP Reanalysis and, thus, is an independent estimate of the winds. The SEASAT Scatterometer (SASS) operated for 90 days in July-September, 1978, while the ERS, NSCAT and QuikScat scatterometers provide a continuous dataset from

  15. Zonal Winds Between 25 and 120 Km Retrieved from Solar Occultation Spectra. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Vancleef, Garrett Warren; Shaw, John H.

    1989-01-01

    Atmospheric winds at heights between 25 and 120 km have been retrieved with precisions of 5/ms from the Doppler shifts of atmospheric absorption lines measured from a satellite-borne instrument. Lines of the upsilon 3 CO2 and upsilon 2 H2O rotation-vibration bands caused by gases in the instrument allowed the instrumental frequency scale to be absolutely calibrated so that accurate relative speeds could be obtained. By comparing the positions of both sets of instrumental lines the calibration of the frequency scale was determined to be stable to a precision of less than 2 x 10(-5) cm during the course of each occultation. It was found that the instrumental resolution of 0.015 cm after apodization, the signal to noise ratio of about 100 and stable calibration allowed relative speeds to be determined to a precision of 5 ms or better by using small numbers of absorption lines between 1600 and 3200 cm. Absolute absorption line positions were simultaneously recovered to precisions of 5 x 10(-5) cm or better. The wind speed profiles determined from four sunset occultations and one sunrise occultation show remarkable similarities in the magnitudes and directions of the zonal wind velocities as functions of height. These wind profiles appear to be manifestations of atmospheric tides.

  16. The effect of the equatorially symmetric zonal winds of Saturn on its gravitational field

    NASA Astrophysics Data System (ADS)

    Kong, Dali; Zhang, Keke; Schubert, Gerald; Anderson, John D.

    2018-04-01

    The penetration depth of Saturn’s cloud-level winds into its interior is unknown. A possible way of estimating the depth is through measurement of the effect of the winds on the planet’s gravitational field. We use a self-consistent perturbation approach to study how the equatorially symmetric zonal winds of Saturn contribute to its gravitational field. An important advantage of this approach is that the variation of its gravitational field solely caused by the winds can be isolated and identified because the leading-order problem accounts exactly for rotational distortion, thereby determining the irregular shape and internal structure of the hydrostatic Saturn. We assume that (i) the zonal winds are maintained by thermal convection in the form of non-axisymmetric columnar rolls and (ii) the internal structure of the winds, because of the Taylor-Proundman theorem, can be uniquely determined by the observed cloud-level winds. We calculate both the variation ΔJn , n = 2, 4, 6 … of the axisymmetric gravitational coefficients Jn caused by the zonal winds and the non-axisymmetric gravitational coefficients ΔJnm produced by the columnar rolls, where m is the azimuthal wavenumber of the rolls. We consider three different cases characterized by the penetration depth 0.36, R S, 0.2, R S and 0.1, R S, where R S is the equatorial radius of Saturn at the 1-bar pressure level. We find that the high-degree gravitational coefficient (J 12 + ΔJ 12) is dominated, in all the three cases, by the effect of the zonal flow with |ΔJ 12/J 12| > 100% and that the size of the non-axisymmetric coefficients ΔJ mn directly reflects the depth and scale of the flow taking place in the Saturnian interior.

  17. First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer

    NASA Astrophysics Data System (ADS)

    Rüfenacht, R.; Kämpfer, N.; Murk, A.

    2012-12-01

    Today, the wind data for the upper stratosphere and lower mesosphere are commonly extrapolated using models or calculated from measurements of the temperature field, but are not measured directly. Still, such measurements would allow direct observations of dynamic processes and thus provide a better understanding of the circulation in this altitude region where the zonal wind speed reaches a maximum. Observations of middle-atmospheric winds are also expected to provide deeper insight in the coupling between the upper and the lower atmosphere, especially in the case of sudden stratospheric warming events. Furthermore, as the local chemical composition of the middle atmosphere can be measured with high accuracy, wind data could be beneficial for the interpretation of the associated transport processes. In future, middle-atmospheric wind measurements could help to improve atmospheric circulation models. Aiming to contribute to the closing of this data gap the Institute of Applied Physics of the University of Bern built a new ground-based 142 GHz Doppler-spectro-radiometer with the acronym WIRA (WInd RAdiometer) specifically designed for the measurement of middle-atmospheric wind. Currently wind speeds in five levels between 30 and 79 km can be retrieved what makes WIRA the first instrument continuously measuring profiles of horizontal wind in this altitude range. On the altitude levels where our measurement can be compared to ECMWF very good agreement has been found in the long-term statistics, with WIRA = (0.98±0.02) × ECMWF + (0.44±0.91) m/s on average, as well as in short time structures with a duration of a few days. WIRA uses a passive double sideband heterodyne receiver together with a digital Fourier transform spectrometer for the data acquisition. A big advantage of the radiometric approach is that such instruments can also operate under adverse weather conditions and thus provide a continuous time series for the given location. The optics enables the

  18. First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer

    NASA Astrophysics Data System (ADS)

    Rüfenacht, Rolf; Kämpfer, Niklaus; Murk, Axel

    2013-04-01

    Today, the wind data for the upper stratosphere and lower mesosphere are commonly extrapolated using models or calculated from measurements of the temperature field, but are not measured directly. Still, such measurements would allow direct observations of dynamic processes and thus provide a better understanding of the circulation in this altitude region where the zonal wind speed reaches a maximum. Observations of middle-atmospheric winds are also expected to provide deeper insight in the coupling between the upper and the lower atmosphere, especially in the case of sudden stratospheric warming events. Furthermore, as the local chemical composition of the middle atmosphere can be measured with high accuracy, wind data could be beneficial for the interpretation of the associated transport processes. In future, middle-atmospheric wind measurements could help to improve atmospheric circulation models. Aiming to contribute to the closing of this data gap the Institute of Applied Physics of the University of Bern built a new ground-based 142 GHz Doppler-spectro-radiometer with the acronym WIRA (WInd RAdiometer) specifically designed for the measurement of middle-atmospheric wind. Until now wind speeds in five levels between 30 and 79 km can be retrieved what made WIRA the first instrument continuously measuring profiles of horizontal wind in this altitude range. On the altitude levels where our measurement can be compared to ECMWF very good agreement has been found in the long-term statistics, with WIRA = (0.98±0.02) × ECMWF + (0.44±0.91) m/s on average, as well as in short time structures with a duration of a few days. WIRA uses a passive heterodyne receiver together with a digital Fourier transform spectrometer for the data acquisition. A big advantage of the radiometric approach is that such instruments can also operate under adverse weather conditions and thus provide a continuous time series for the given location. The optics enables the instrument to scan a

  19. On the role of the Kelvin wave in the westerly phase of the semiannual zonal wind oscillation

    NASA Technical Reports Server (NTRS)

    Dunkerton, T.

    1979-01-01

    The role of the Kelvin wave, discovered by Hirota (1978), in producing the westerly accelerations of the semiannual zonal wind oscillation in the tropical upper stratosphere is examined quantitatively. It is shown that, for reasonable values of the wave parameters, this Kelvin wave could indeed give rise to the observed accelerations. For the thermal damping rates of Dickinson (1973), the most likely range of phase speeds for a wavenumber 1 disturbance is from 45 to 60 m/sec. For 'photochemically accelerated' damping rates (Blake and Lindzen, 1973), a phase speed in excess of 70 m/sec would be required. The possibility of a significant modulation of the semiannual westerlies by the quasi-biennial oscillation is also suggested.

  20. Shape, zonal winds and gravitational field of Jupiter: a fully self-consistent, multi-layered model

    NASA Astrophysics Data System (ADS)

    Schubert, Gerald; Kong, Dali; Zhang, Keke

    2016-10-01

    We construct a three-dimensional, finite-element, fully self-consistent, multi-layered,non-spheroidal model of Jupiter consisting of an inner core, a metallic electrically conducting dynamo region and an outer molecular electrically insulating envelope. We assume that the Jovian zonal winds are on cylinders parallel to the rotation axis but, due to the effect of magnetic braking, are confined within the outer molecular envelope. Two related calculations are carried out. The first provides an accurate description of the shape and internal density profile of Jupiter; the effect of rotational distortion is not treated as a small perturbation on a spherically symmetric state. This calculation determines the density, size and shape of the inner core, the irregular shape of the 1-bar pressure level, and the internal structure of Jupiter; the full effect of rotational distortion, without the influence of the zonal winds, is accounted for. Our multi-layered model is able to produce the known mass, the known equatorial and polar radii, and the known zonal gravitational coefficient J2 of Jupiter within their error bars; it also yields the coefficients J4 and J6 within about 5% accuracy, and the core equatorial radius 0.09RJ containing 3.73 Earth masses.The second calculation determines the variation of the gravitational field caused solely by the effect of the zonal winds on the rotationally distorted non-spheroidal Jupiter. Four different cases, ranging from a deep wind profile to a very shallow profile, are considered and implications for accurate interpretation of the zonal gravitational coefficients expected from the Juno mission are discussed.

  1. The 4-5 day mode oscillation in zonal winds of Indian middle atmosphere during MONEX-79

    NASA Astrophysics Data System (ADS)

    Reddy, R. S.; Mukherjee, B. K.; Indira, K.; Murty, B. V. R.

    1985-12-01

    In the early studies based on time series of balloon observations, the existence of 4 to 5 day period waves and 10 to 20 day wind fluctuations were found in the tropical lower stratosphere, and they are identified theoretically as the mixed Rossby-gravity wave and the Kelvin wave, respectively. On the basis of these studies, it was established that the vertically propagating equatorial waves play an important role in producing the QBO (quasi-biennial oscillation) in the mean zonal wind through the mechanism of wave-zonal interaction. These studies are mainly concentrated over the equatorial Pacific and Atlantic Oceans. Similar prominent wave disturbances have been observed over the region east of the Indian Ocean during a quasi-biennial oscillation. Zonal winds in upper troposphere and lower stratosphere (10 to 20) km of the middle atmosphere over the Indian subcontinent may bear association with the activity of summer monsoon (June-September). Monsoon Experiment (MONEX-79) has provided upper air observations at Balasore (21 deg. 30 min.N; 85 deg. 56 min.E), during the peak of monsoon months July and August. A unique opportunity has, therefore, been provided to study the normal oscillations present in the zonal winds of lower middle atmosphere over India, which may have implication on large scale wave dynamics. This aspect is examined in the present study.

  2. Dependence of wind speed and UV albedo at Venus top cloud layer on topography and local time revealed from VMC images

    NASA Astrophysics Data System (ADS)

    Patsaeva, Marina; Khatuntsev, Igor; Turin, Alexander; Zasova, Ludmila; Bertaux, Jean-loup

    2017-04-01

    A set of UV (365 nm) and IR (965 nm) images obtained by the Venus Monitoring Camera (VMC) was used to study the circulation of the mesosphere at two altitude levels. Displacement vectors were obtained by wind tracking in automated mode for observation period from 2006 to 2014 for UV images [1,2] and from 2006 to 2012 for IR images. The long observation period and good longitude-latitude coverage by single measurements allowed us to focus on the study of the slow-periodic component. The influence of the underlying surface topography on the change of speed of the average zonal wind at UV level at low latitudes, discovered by visual methods has been described in [3]. Analysis of the longitude-latitude distribution of the zonal and meridional components for 172000 (257 orbits) digital individual wind measurements at UV level and for 32,000 (150 orbits) digital individual wind measurements at IR level allows us to compare the influence of Venus topography on the change of the zonal and meridional components at both cloud levels. At the UV level (67±2 km) longitudinal profiles of the zonal speed for different latitude bins in low latitudes correlate with surface profiles. These correlations are most noticeable in the region of Aphrodite Terra. The correlation shift depends on the surface height. Albedo profiles correlate with surface profiles also at high latitudes. Zonal speed profiles at low latitude (5-15°S) depend not only on altitude, but also on local time. Minimum of the zonal speed is observed over Aphrodite Terra (90-100°E) at about 12 LT. A diurnal harmonic with an extremum over Aphrodite Terra was found. It can be considered as a superposition of a solar-synchronous tide and a stationary wave caused by interaction of the windstream with the surface. At the IR level (55±4 km) a correlation between surface topography and meridional speed was found in the region 10-30°S. The average meridional flow is equatorward at the IR level, but in the region Aphrodite

  3. REVIEWS OF TOPICAL PROBLEMS: Generation of large-scale eddies and zonal winds in planetary atmospheres

    NASA Astrophysics Data System (ADS)

    Onishchenko, O. G.; Pokhotelov, O. A.; Astafieva, N. M.

    2008-06-01

    The review deals with a theoretical description of the generation of zonal winds and vortices in a turbulent barotropic atmosphere. These large-scale structures largely determine the dynamics and transport processes in planetary atmospheres. The role of nonlinear effects on the formation of mesoscale vortical structures (cyclones and anticyclones) is examined. A new mechanism for zonal wind generation in planetary atmospheres is discussed. It is based on the parametric generation of convective cells by finite-amplitude Rossby waves. Weakly turbulent spectra of Rossby waves are considered. The theoretical results are compared to the results of satellite microwave monitoring of the Earth's atmosphere.

  4. First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer

    NASA Astrophysics Data System (ADS)

    Rüfenacht, R.; Kämpfer, N.; Murk, A.

    2012-11-01

    We report on the wind radiometer WIRA, a new ground-based microwave Doppler-spectro-radiometer specifically designed for the measurement of middle-atmospheric horizontal wind by observing ozone emission spectra at 142.17504 GHz. Currently, wind speeds in five levels between 30 and 79 km can be retrieved which makes WIRA the first instrument able to continuously measure horizontal wind in this altitude range. For an integration time of one day the measurement error on each level lies at around 25 m s-1. With a planned upgrade this value is expected to be reduced by a factor of 2 in the near future. On the altitude levels where our measurement can be compared to wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF) very good agreement in the long-term statistics as well as in short time structures with a duration of a few days has been found. WIRA uses a passive double sideband heterodyne receiver together with a digital Fourier transform spectrometer for the data acquisition. A big advantage of the radiometric approach is that such instruments can also operate under adverse weather conditions and thus provide a continuous time series for the given location. The optics enables the instrument to scan a wide range of azimuth angles including the directions east, west, north, and south for zonal and meridional wind measurements. The design of the radiometer is fairly compact and its calibration does not rely on liquid nitrogen which makes it transportable and suitable for campaign use. WIRA is conceived in a way that it can be operated remotely and does hardly require any maintenance. In the present paper, a description of the instrument is given, and the techniques used for the wind retrieval based on the determination of the Doppler shift of the measured atmospheric ozone emission spectra are outlined. Their reliability was tested using Monte Carlo simulations. Finally, a time series of 11 months of zonal wind measurements over Bern (46°57' N

  5. First middle-atmospheric zonal wind profile measurements with a new ground-based microwave Doppler-spectro-radiometer

    NASA Astrophysics Data System (ADS)

    Rüfenacht, R.; Kämpfer, N.; Murk, A.

    2012-07-01

    We report on the wind radiometer WIRA, a new ground-based microwave Doppler-spectro-radiometer specifically designed for the measurement of middle-atmospheric horizontal wind by observing ozone emission spectra at 142.17504 GHz. Currently, wind speeds in five levels between 30 and 79 km can be retrieved what makes WIRA the first instrument able to continuously measure horizontal wind in this altitude range. For an integration time of one day the measurement error on each level lies at around 25 m s-1. With a planned upgrade this value is expected to be reduced by a factor of 2 in the near future. On the altitude levels where our measurement can be compared to wind data from the European Centre for Medium-Range Weather Forecasts (ECMWF) very good agreement in the long-term statistics as well as in short time structures with a duration of a few days has been found. WIRA uses a passive double sideband heterodyne receiver together with a digital Fourier transform spectrometer for the data acquisition. A big advantage of the radiometric approach is that such instruments can also operate under adverse weather conditions and thus provide a continuous time series for the given location. The optics enables the instrument to scan a wide range of azimuth angles including the directions east, west, north, and south for zonal and meridional wind measurements. The design of the radiometer is fairly compact and its calibration does not rely on liquid nitrogen what makes it transportable and suitable for campaign use. WIRA is conceived in a way that it can be operated remotely and does hardly require any maintenance. In the present paper, a description of the instrument is given, and the used techniques for the wind retrieval based on the determination of the Doppler shift of the measured atmospheric ozone emission spectra are outlined. Their reliability was tested using MonteCarlo simulations. Finally, a first time series of 11 months of zonal wind measurements over Bern (46°57

  6. Influence of Venus topography on the zonal wind and UV albedo at cloud top level: The role of stationary gravity waves

    NASA Astrophysics Data System (ADS)

    Bertaux, Jean-Loup; Khatuntsev, I. V.; Hauchecorne, A.; Markiewicz, W. J.; Marcq, E.; Lebonnois, S.; Patsaeva, M.; Turin, A.; Fedorova, A.

    2016-06-01

    Based on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67 ± 2 km) collected with Venus Monitoring Camera on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°S) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the uplift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to the cloud top level, break there, and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth by Lindzen (1981) but is not reproduced in the current GCM of Venus atmosphere from LMD. (Laboratoire de Météorologie Dynamique) In the equatorial regions, the UV albedo at 365 nm varies also with longitude. We argue that this variation may be simply explained by the divergence of the horizontal wind field. In the longitude region (from 60° to -10°) where the horizontal wind speed is increasing in magnitude (stretch), it triggers air upwelling which brings the UV absorber at cloud top level and decreases the albedo and vice versa when the wind is decreasing in magnitude (compression). This picture is fully consistent with the classical view of Venus meridional circulation, with upwelling at equator revealed by horizontal air motions away from equator: the longitude effect is only an additional but important modulation of this effect. This interpretation is comforted by a recent map of cloud top H2O, showing that near the equator the lower UV albedo longitude region is correlated with increased H2O. We argue that H2O enhancement is the sign of upwelling, suggesting that the UV absorber is also brought to cloud top by upwelling.

  7. Wind speed perception and risk.

    PubMed

    Agdas, Duzgun; Webster, Gregory D; Masters, Forrest J

    2012-01-01

    How accurately do people perceive extreme wind speeds and how does that perception affect the perceived risk? Prior research on human-wind interaction has focused on comfort levels in urban settings or knock-down thresholds. No systematic experimental research has attempted to assess people's ability to estimate extreme wind speeds and perceptions of their associated risks. We exposed 76 people to 10, 20, 30, 40, 50, and 60 mph (4.5, 8.9, 13.4, 17.9, 22.3, and 26.8 m/s) winds in randomized orders and asked them to estimate wind speed and the corresponding risk they felt. Multilevel modeling showed that people were accurate at lower wind speeds but overestimated wind speeds at higher levels. Wind speed perceptions mediated the direct relationship between actual wind speeds and perceptions of risk (i.e., the greater the perceived wind speed, the greater the perceived risk). The number of tropical cyclones people had experienced moderated the strength of the actual-perceived wind speed relationship; consequently, mediation was stronger for people who had experienced fewer storms. These findings provide a clearer understanding of wind and risk perception, which can aid development of public policy solutions toward communicating the severity and risks associated with natural disasters.

  8. Wind Speed Perception and Risk

    PubMed Central

    Agdas, Duzgun; Webster, Gregory D.; Masters, Forrest J.

    2012-01-01

    Background How accurately do people perceive extreme wind speeds and how does that perception affect the perceived risk? Prior research on human–wind interaction has focused on comfort levels in urban settings or knock-down thresholds. No systematic experimental research has attempted to assess people's ability to estimate extreme wind speeds and perceptions of their associated risks. Method We exposed 76 people to 10, 20, 30, 40, 50, and 60 mph (4.5, 8.9, 13.4, 17.9, 22.3, and 26.8 m/s) winds in randomized orders and asked them to estimate wind speed and the corresponding risk they felt. Results Multilevel modeling showed that people were accurate at lower wind speeds but overestimated wind speeds at higher levels. Wind speed perceptions mediated the direct relationship between actual wind speeds and perceptions of risk (i.e., the greater the perceived wind speed, the greater the perceived risk). The number of tropical cyclones people had experienced moderated the strength of the actual–perceived wind speed relationship; consequently, mediation was stronger for people who had experienced fewer storms. Conclusion These findings provide a clearer understanding of wind and risk perception, which can aid development of public policy solutions toward communicating the severity and risks associated with natural disasters. PMID:23226230

  9. Observed correlation of Venus topography with the zonal wind and albedo at cloud top level: the role of stationary gravity waves.

    NASA Astrophysics Data System (ADS)

    Bertaux, Jean-Loup; Khatunstsev, Igor; Hauchecorne, Alain; Markiewicz, Wojtek; Emmanuel, Marcq; Sébastien, Lebonnois; Marina, Patsaeva; Alex, Turin; Anna, Fedorova

    2016-04-01

    Based on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67±2 km) collected with VMC (Venus Monitoring Camera) on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°s) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to cloud top level, break there and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth by Lindzen [1981], but is not reproduced in a current GCM of Venus atmosphere. Consistent with present findings, the two VEGA mission balloons experienced a small, but significant, difference of westward velocity, at their 53 km floating altitude. The albedo at 365 nm varies also with longitude and latitude in a pattern strikingly similar in the low latitude regions to a recent map of cloud top H2O [Fedorova et al., 2015], in which a lower UV albedo is correlated with increased H2O. We argue that H2O enhancement is the sign of upwelling, suggesting that the UV absorber is also brought to cloud top by upwelling.

  10. On the long-term variability of Jupiter and Saturn zonal winds

    NASA Astrophysics Data System (ADS)

    Sanchez-Lavega, A.; Garcia-Melendo, E.; Hueso, R.; Barrado-Izagirre, N.; Legarreta, J.; Rojas, J. F.

    2012-12-01

    We present an analysis of the long-term variability of Jupiter and Saturn zonal wind profiles at their upper cloud level as retrieved from cloud motion tracking on images obtained at ground-based observatories and with different spacecraft missions since 1979, encompassing about three Jovian and one Saturn years. We study the sensitivity and variability of the zonal wind profile in both planets to major planetary-scale disturbances and to seasonal forcing. We finally discuss the implications that these results have for current model efforts to explain the global tropospheric circulation in these planets. Acknowledgements: This work has been funded by Spanish MICIIN AYA2009-10701 with FEDER support, Grupos Gobierno Vasco IT-464-07 and UPV/EHU UFI11/55. [1] Sánchez-Lavega A., et al., Icarus, 147, 405-420 (2000). [2] García-Melendo E., Sánchez LavegaA., Icarus, 152, 316-330 (2001) [3] Sánchez-Lavega A., et al., Nature, 423, 623-625 (2003). [4] García-Melendo E., et al., Geophysical Research Letters, 37, L22204 (2010).

  11. A simple inertial model for Neptune's zonal circulation

    NASA Technical Reports Server (NTRS)

    Allison, Michael; Lumetta, James T.

    1990-01-01

    Voyager imaging observations of zonal cloud-tracked winds on Neptune revealed a strongly subrotational equatorial jet with a speed approaching 500 m/s and generally decreasing retrograde motion toward the poles. The wind data are interpreted with a speculative but revealingly simple model based on steady gradient flow balance and an assumed global homogenization of potential vorticity for shallow layer motion. The prescribed model flow profile relates the equatorial velocity to the mid-latitude shear, in reasonable agreement with the available data, and implies a global horizontal deformation scale L(D) of about 3000 km.

  12. Post-processing method for wind speed ensemble forecast using wind speed and direction

    NASA Astrophysics Data System (ADS)

    Sofie Eide, Siri; Bjørnar Bremnes, John; Steinsland, Ingelin

    2017-04-01

    Statistical methods are widely applied to enhance the quality of both deterministic and ensemble NWP forecasts. In many situations, like wind speed forecasting, most of the predictive information is contained in one variable in the NWP models. However, in statistical calibration of deterministic forecasts it is often seen that including more variables can further improve forecast skill. For ensembles this is rarely taken advantage of, mainly due to that it is generally not straightforward how to include multiple variables. In this study, it is demonstrated how multiple variables can be included in Bayesian model averaging (BMA) by using a flexible regression method for estimating the conditional means. The method is applied to wind speed forecasting at 204 Norwegian stations based on wind speed and direction forecasts from the ECMWF ensemble system. At about 85 % of the sites the ensemble forecasts were improved in terms of CRPS by adding wind direction as predictor compared to only using wind speed. On average the improvements were about 5 %, but mainly for moderate to strong wind situations. For weak wind speeds adding wind direction had more or less neutral impact.

  13. Estimation of effective wind speed

    NASA Astrophysics Data System (ADS)

    Østergaard, K. Z.; Brath, P.; Stoustrup, J.

    2007-07-01

    The wind speed has a huge impact on the dynamic response of wind turbine. Because of this, many control algorithms use a measure of the wind speed to increase performance, e.g. by gain scheduling and feed forward. Unfortunately, no accurate measurement of the effective wind speed is online available from direct measurements, which means that it must be estimated in order to make such control methods applicable in practice. In this paper a new method is presented for the estimation of the effective wind speed. First, the rotor speed and aerodynamic torque are estimated by a combined state and input observer. These two variables combined with the measured pitch angle is then used to calculate the effective wind speed by an inversion of a static aerodynamic model.

  14. The 10-30-day oscillation of winter zonal wind in the entrance region of the East Asian subtropical jet and its relationship with precipitation in southern China

    NASA Astrophysics Data System (ADS)

    Yao, Chenyu; Huang, Qian; Zhu, Bin; Liu, Fei

    2018-06-01

    Using ECMWF ERA-Interim 6-h reanalysis data, zonal wind intra-seasonal oscillations (ISOs) in the entrance region of the East Asian subtropical westerly jet (EASWJ) in winter from 1979/1980 to 2012/2013 are studied. The results first show that there is an area with large ISO strength in the northwest of the EASWJ; in the key region, zonal wind has a dominant period of 10-30 days. The composite analysis reveals that zonal wind at 200 hPa in this key region has 10-30-day oscillation characteristics. On the 10-30-day time scale, the center of zonal wind anomaly moves eastward. The propagation of zonal wind oscillation relates to temperature tendencies at different latitudes. The remarkable increase (or decrease) in zonal wind in the key region is mostly determined by temperature anomalies to the north. The 10-30-day filtered temperature advection to the north of the key region leads to either a decrease or an increase in temperature; on the other hand, temperature variations south of the key region have trends opposite of the northern trends, which changes the temperature gradient. On the 10-30-day time scale, zonal wind anomalies are associated with precipitation in southern China. When there are easterly wind anomalies over the key region, precipitation occurs over the Yangtze River basin and its south. Diabatic heating during precipitation corresponds with warming to the south of the key region, which combines with the temperature advection to weaken the easterly wind and strengths the westerly wind. Then, the intra-seasonal precipitation moves to southwest China with warm advection and the enhanced westerly wind, which brings the positive relative vorticity advection there.

  15. Jupiter cloud morphology and zonal winds from ground-based observations before and during Juno's first perijove

    NASA Astrophysics Data System (ADS)

    Hueso, R.; Sánchez-Lavega, A.; Iñurrigarro, P.; Rojas, J. F.; Pérez-Hoyos, S.; Mendikoa, I.; Gómez-Forrellad, J. M.; Go, C.; Peach, D.; Colas, F.; Vedovato, M.

    2017-05-01

    We analyze Jupiter observations between December 2015 and August 2016 in the 0.38-1.7 μm wavelength range from the PlanetCam instrument at the 2.2 m telescope at Calar Alto Observatory and in the optical range by amateur observers contributing to the Planetary Virtual Observatory Laboratory. Over this time Jupiter was in a quiescent state without notable disturbances. Analysis of ground-based images and Hubble Space Telescope observations in February 2016 allowed the retrieval of mean zonal winds from -74.5° to +73.2°. These winds did not change over 2016 or when compared with winds from previous years with the sole exception of intense zonal winds at the North Temperate Belt. We also present results concerning the major wave systems in the North Equatorial Belt and in the upper polar hazes visible in methane absorption bands, a description of the planet's overall cloud morphology and observations of Jupiter hours before Juno's orbit insertion.

  16. Saturn's North Polar Vortex Revealed by Cassini/VIMS: Zonal Wind Structure and Constraints on Cloud Distributions

    NASA Astrophysics Data System (ADS)

    Baines, Kevin H.; Momary, T. W.; Fletcher, L. N.; Buratti, B. J.; Roos-Serote, M.; Showman, A. P.; Brown, R. H.; Clark, R. N.; Nicholson, P. D.

    2008-09-01

    We present the first high-spatial resolution, near-nadir imagery and movies of Saturn's north polar region that reveal the wind structure of a north polar vortex. Obtained by Cassini/VIMS on June 15, 2008 from high over Saturn's polar region (sub-spacecraft latitude of 65 degrees N. lat) at an altitude of 0.42 million km during the long polar night, these 210-per-pixel images of the polar region north of 73 degrees N. latitude show several concentric cloud rings and hundreds of individual cloud features in silhouette against the 5-micron background thermal glow of Saturn's deep atmosphere. In contrast to the clear eye of the south polar vortex, the north polar vortex sports a central cloud feature about 650-km in diameter. Zonal winds reach a maximum of 150 m/s near 88 degrees N. latitude (planetocentric) - comparable to the south polar vortex maximum of 190 m/s near 88 degrees S. latitude - and fall off nearly monotonically to 10 m/s near 80 degrees N. latitude. At slightly greater distance from the pole, inside the north polar hexagon in the 75-77 degree N. latitude region, zonal winds increase dramatically to 130 m/s, as silhouetted clouds are seen speeding aroud the "race track” of the hexagonal feature. VIMS 5-micron thermal observations over a 1.6-year period from October 29, 2006 to June 15, 2008 are consistent with the polar hexagon structure itself remaining fixed in the Voyager-era radio rotation rate (Desch and Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) to within an accuracy of 3 seconds per rotational period. This agrees with the stationary nature of the wave in this rotation system found by Godfrey (Icarus 76, 335-356, 1988), but is inconsistent with rotation rates found during the current Cassini era.

  17. Are Strong Zonal Winds in Giant Planets Caused by Density-Stratification?

    NASA Astrophysics Data System (ADS)

    Verhoeven, J.; Stellmach, S.

    2012-12-01

    One of the most striking features of giant planets like Jupiter and Saturn are the zonal wind patterns observed on their surfaces. The mechanism that drives this differential rotation is still not clearly identified and is currently strongly debated in the astro- and geophysics community. Different mechanisms have been proposed over the last decades. Here, a recently discovered mechanism based on background density stratification (Glatzmaier et al., 2009) is investigated. This mechanism has the potential to overcome known difficulties of previous explanations and its efficiency has been demonstrated in 2-d simulations covering equatorial planes. By performing highly resolved numerical simulations in a local Cartesian geometry, we are able to test the efficiency and functionality of this mechanism in turbulent, rotating convection in three spatial dimensions. The choice of a Cartesian model geometry naturally excludes other known mechanisms capable of producing differential rotation, thus allowing us to investigate the role of density stratification in isolation. Typically, the dynamics can be classified into two main regimes: A regime exhibiting strong zonal winds for weak to moderate thermal driving and a regime where zonal winds are largely absent in the case of a strong thermal forcing. Our results indicate that previous 2-d results must be handled with care and can only explain parts of the full 3-d behavior. We show that the density-stratification mechanism tends to operate in a more narrow parameter range in 3-d as compared to 2-d simulations. The dynamics of the regime transition is shown to differ in both cases, which renders scaling laws derived from two-dimensional studies questionable. Based on our results, we provide estimates for the importance of the density-stratification mechanism for giant planets like Jupiter (strong density stratification), for systems like the Earth's core (weak density stratification) and compare its efficiency with other

  18. A New Look at Titan's Zonal Winds from Cassini Radio Occultations

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Schinder, P. J.

    2012-01-01

    We use the existing thirteen Cassini radio'occultation soundings to construct a meridional cross section of geopotential height vs. pressure and latitude. The assumption of balanced flow permits the construction of a similar cross section of zonal winds, from near the surface to the 0.1'mbar level. In the lower troposphere, the winds are approx.10 m/s, except within 20deg of the equator, where they are much smaller. The winds increase higher up in the troposphere to nearly 40 m/s in the tropopause region, but then decay rapidly in the lower stratosphere to near'zero values at 20 mbar (approx.80 km), reminiscent of the Huygens Doppler Wind Experiment result. This null zone extends over most latitudes, except for limited bands at mid'latitudes. Higher up in the stratosphere, the winds become larger. They are highest in the northern (winter) hemisphere. We compare the occultation results with the DWE and CIRS retrievals and discuss the similarities and differences among the data sets.

  19. Climatology of mesopause region nocturnal temperature, zonal wind, and sodium density observed by sodium lidar over Hefei, China (32°N, 117°E)

    NASA Astrophysics Data System (ADS)

    Li, T.; Ban, C.; Fang, X.; Li, J.; Wu, Z.; Xiong, J.; Feng, W.; Plane, J. M. C.

    2017-12-01

    The University of Science and Technology of China narrowband sodium temperature/wind lidar, located in Hefei, China (32°N, 117°E), was installed in November 2011 and have made routine nighttime measurements since January 2012. We obtained 154 nights ( 1400 hours) of vertical profiles of temperature, sodium density, and zonal wind, and 83 nights ( 800 hours) of vertical flux of gravity wave (GW) zonal momentum in the mesopause region (80-105 km) during the period of 2012 to 2016. In temperature, it is likely that the diurnal tide dominates below 100 km in spring, while the semidiurnal tide dominates above 100 km throughout the year. A clear semiannual variation in temperature is revealed near 90 km, likely related to the tropical mesospheric semiannual oscillation (MSAO). The variability of sodium density is positively correlated with temperature, suggesting that in addition to dynamics, the chemistry may also play an important role in the formation of sodium atoms. The observed sodium peak density is 1000 cm-3 higher than that simulated by the model. In zonal wind, the diurnal tide dominates in both spring and fall, while semidiurnal tide dominates in winter. The observed semiannual variation in zonal wind near 90 km is out-of-phase with that in temperature, consistent with tropical MSAO. The GW zonal momentum flux is mostly westward in fall and winter, anti-correlated with eastward zonal wind. The annual mean flux averaged over 87-97 km is -0.3 m2/s2 (westward), anti-correlated with eastward zonal wind of 10 m/s. The comparisons of lidar results with those observed by satellite, nearby radar, and simulated by model show generally good agreements.

  20. Temporal Variability and Latitudinal Jets in Venus's Zonal Wind Profiles

    NASA Astrophysics Data System (ADS)

    Young, Eliot F.; Bullock, M. A.; Tavenner, T.; Coyote, S.; Murphy, J. R.

    2008-09-01

    We have observed Venus's night hemisphere from NASA's IRTF (Infrared Telescope Facility) during each inferior conjunction since 2001 to quantify the motion of features in Venus's lower and middle cloud decks. We now present latitudinal profiles from 11 nights, obtained in May and July 2004, February 2006 and September 2007. In about 7 of the 11 nights there are zonal jets near 45N and/or -50S, with speed differentials of 5 to 15 m/s relative to the adjacent equatorward latitude bands. These jets may be evidence of episodic Hadley cell-type circulation. About half of the nights show relatively constant velocity profiles between the latitudes of 50N to 50S, suggesting that considerable mixing is taking place between latitudes. Our most remarkable result is the temporal variability in the median zonal speeds from day to day. For example, the median velocity near the equator increases from 53 to 65 m/s over the period from July 11 - 13, 2004, and increases from 65 to 82 m/s over the period from Sept. 9 - 11, 2007. These velocity changes are too great to be due to the tracking of clouds that are in the middle vs. lower cloud deck, nor can they be caused by clouds that occupy different altitudes; a velocity variation of 25% corresponds to an altitude difference of 15 km, based on vertical profiles of zonal windspeeds from tracking of Pioneer Venus and Venera descent probes. Fifteen km is greater than the expected variation in either cloud base. VIRTIS observations of Venus's southern hemisphere were also obtained in September 2007 and should be able to corroborate or contradict the observed variations. This work was supported by NASA's Planetary Astronomy and Atmospheres programs.

  1. Some studies of zonal and meridional wind characteristics at low latitude Indian stations

    NASA Astrophysics Data System (ADS)

    Nagpal, O. P.; Kumar, S.

    1985-12-01

    At the beginning of the Indian Middle Atmosphere Programme (IMAP), it was decided that the preparation of consolidation reports of already available parameters for the middle atmosphere would be useful. Atmospheric wind data obtained by rockets and balloons constituted one such parameter which had to be consolidated. The present paper summaries the results of this consolidation study. Both zonal and meridional components of winds at four low latitude Indian stations namely Thumba, Shar, Hyderabad, and Balasore, have been analyzed to yield reference wind profiles for each month. The montly mean values have been used to bring out the amplitudes and phases of the annual, semiannual and quasi-biennial oscillations.

  2. Some studies of zonal and meridional wind characteristics at low latitude Indian stations

    NASA Technical Reports Server (NTRS)

    Nagpal, O. P.; Kumar, S.

    1985-01-01

    At the beginning of the Indian Middle Atmosphere Programme (IMAP), it was decided that the preparation of consolidation reports of already available parameters for the middle atmosphere would be useful. Atmospheric wind data obtained by rockets and balloons constituted one such parameter which had to be consolidated. The present paper summaries the results of this consolidation study. Both zonal and meridional components of winds at four low latitude Indian stations namely Thumba, Shar, Hyderabad, and Balasore, have been analyzed to yield reference wind profiles for each month. The montly mean values have been used to bring out the amplitudes and phases of the annual, semiannual and quasi-biennial oscillations.

  3. Generalized extreme gust wind speeds distributions

    USGS Publications Warehouse

    Cheng, E.; Yeung, C.

    2002-01-01

    Since summer 1996, the US wind engineers are using the extreme gust (or 3-s gust) as the basic wind speed to quantify the destruction of extreme winds. In order to better understand these destructive wind forces, it is important to know the appropriate representations of these extreme gust wind speeds. Therefore, the purpose of this study is to determine the most suitable extreme value distributions for the annual extreme gust wind speeds recorded in large selected areas. To achieve this objective, we are using the generalized Pareto distribution as the diagnostic tool for determining the types of extreme gust wind speed distributions. The three-parameter generalized extreme value distribution function is, thus, reduced to either Type I Gumbel, Type II Frechet or Type III reverse Weibull distribution function for the annual extreme gust wind speeds recorded at a specific site.With the considerations of the quality and homogeneity of gust wind data collected at more than 750 weather stations throughout the United States, annual extreme gust wind speeds at selected 143 stations in the contiguous United States were used in the study. ?? 2002 Elsevier Science Ltd. All rights reserved.

  4. The generation of a zonal-wind oscillation by nonlinear interactions of internal gravity waves

    NASA Astrophysics Data System (ADS)

    Campbell, Lucy

    2003-11-01

    Nonlinear interactions of internal gravity waves give rise to numerous large-scale phenomena that are observed in the atmosphere, for example the quasi-biennial oscillation (QBO). This is an oscillation in zonal wind direction which is observed in the equatorial stratosphere; it is characterized by alternating regimes of easterly and westerly shear that descend with time. In the past few decades, a number of theories have been developed to explain the mechanism by which the QBO is generated. These theories are all based on ``quasi-linear'' representations of wave-mean-flow interactions. In this presentation, a fully nonlinear numerical simulation of the QBO is described. A spectrum of gravity waves over a range of phase speeds is forced at the lower boundary of the computational domain and propagates upwards in a density-stratified shear flow. As a result of the absorption and reflection of the waves at their critical levels, regions of large shear develop in the background flow and propagate downwards with time.

  5. Assessment of C-Type Darrieus Wind Turbine Under Low Wind Speed Condition

    NASA Astrophysics Data System (ADS)

    Misaran, M. S.; Rahman, Md. M.; Muzammil, W. K.; Ismail, M. A.

    2017-07-01

    Harvesting wind energy in in a low wind speed region is deem un-economical if not daunting task. Study shows that a minimum cut in speed of 3.5 m/s is required to extract a meaningful wind energy for electricity while a mean speed of 6 m/s is preferred. However, in Malaysia the mean speed is at 2 m/s with certain potential areas having 3 m/s mean speed. Thus, this work aims to develop a wind turbine that able to operate at lower cut-in speed and produce meaningful power for electricity generation. A C-type Darrieus blade is selected as it shows good potential to operate in arbitrary wind speed condition. The wind turbine is designed and fabricated in UMS labs while the performance of the wind turbine is evaluated in a simulated wind condition. Test result shows that the wind turbine started to rotate at 1 m/s compared to a NACA 0012 Darrieus turbine that started to rotate at 3 m/s. The performance of the turbine shows that it have good potential to be used in an intermittent arbitrary wind speed condition as well as low mean wind speed condition.

  6. Wind speed vector restoration algorithm

    NASA Astrophysics Data System (ADS)

    Baranov, Nikolay; Petrov, Gleb; Shiriaev, Ilia

    2018-04-01

    Impulse wind lidar (IWL) signal processing software developed by JSC «BANS» recovers full wind speed vector by radial projections and provides wind parameters information up to 2 km distance. Increasing accuracy and speed of wind parameters calculation signal processing technics have been studied in this research. Measurements results of IWL and continuous scanning lidar were compared. Also, IWL data processing modeling results have been analyzed.

  7. High-resolution daily gridded datasets of air temperature and wind speed for Europe

    NASA Astrophysics Data System (ADS)

    Brinckmann, S.; Krähenmann, S.; Bissolli, P.

    2015-08-01

    New high-resolution datasets for near surface daily air temperature (minimum, maximum and mean) and daily mean wind speed for Europe (the CORDEX domain) are provided for the period 2001-2010 for the purpose of regional model validation in the framework of DecReg, a sub-project of the German MiKlip project, which aims to develop decadal climate predictions. The main input data sources are hourly SYNOP observations, partly supplemented by station data from the ECA&D dataset (http://www.ecad.eu). These data are quality tested to eliminate erroneous data and various kinds of inhomogeneities. Grids in a resolution of 0.044° (5 km) are derived by spatial interpolation of these station data into the CORDEX area. For temperature interpolation a modified version of a regression kriging method developed by Krähenmann et al. (2011) is used. At first, predictor fields of altitude, continentality and zonal mean temperature are chosen for a regression applied to monthly station data. The residuals of the monthly regression and the deviations of the daily data from the monthly averages are interpolated using simple kriging in a second and third step. For wind speed a new method based on the concept used for temperature was developed, involving predictor fields of exposure, roughness length, coastal distance and ERA Interim reanalysis wind speed at 850 hPa. Interpolation uncertainty is estimated by means of the kriging variance and regression uncertainties. Furthermore, to assess the quality of the final daily grid data, cross validation is performed. Explained variance ranges from 70 to 90 % for monthly temperature and from 50 to 60 % for monthly wind speed. The resulting RMSE for the final daily grid data amounts to 1-2 °C and 1-1.5 m s-1 (depending on season and parameter) for daily temperature parameters and daily mean wind speed, respectively. The datasets presented in this article are published at http://dx.doi.org/10.5676/DWD_CDC/DECREG0110v1.

  8. Observed longitude variations of zonal wind, UV albedo and H2O at Venus cloud top level: the role of stationary gravity waves generated by Venus topography

    NASA Astrophysics Data System (ADS)

    Bertaux, Jean-Loup; Hauchecorne, Alain; khatuntsev, Igor; Markiewicz, Wojciech; Marcq, emmanuel; Lebonnois, Sebastien; Patsaeva, Marina; Turin, Alexander; Fedorova, Anna

    2016-10-01

    Based on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67±2 km) collected with VMC (Venus Monitoring Camera) on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5°S to 15°S) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to the cloud top level, break there and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth but is not reproduced in the current GCM of Venus atmosphere from LMD.In the equatorial regions, the UV albedo of clouds at 365 nm and the H2O mixing ratio at cloud top varies also with longitude, with an anti-correlation: the more H2O, the darker are the clouds. We argue that these variations may be simply explained by the divergence of the horizontal wind field. In the longitude region (from 60° to -10°) where the horizontal wind speed is increasing in magnitude (stretch), it triggers air upwelling which brings both the UV absorber and H2O at cloud top level and decreases the albedo, and vice-versa when the wind is decreasing in magnitude (compression). This picture is fully consistent with the classical view of Venus meridional circulation, with upwelling at equator revealed by horizontal air motions away from equator: the longitude effect is only an additional but important modulation of this effect. We argue that H2O enhancement is the sign of upwelling because the H2O mixing ratio decreases with altitude, comforting the view that the UV absorber is also brought to cloud top by upwelling.

  9. Zonal wind indices to reconstruct United States winter precipitation during El Niño

    NASA Astrophysics Data System (ADS)

    Farnham, D. J.; Steinschneider, S.; Lall, U.

    2017-12-01

    The highly discussed 2015/16 El Niño event, which many likened to the similarly strong 1997/98 El Niño event, led to precipitation impacts over the continental United States (CONUS) inconsistent with general expectations given past events and model-based forecasts. This presents a challenge for regional water managers and others who use seasonal precipitation forecasts who previously viewed El Niño events as times of enhanced confidence in seasonal water availability and flood risk forecasts. It is therefore useful to understand the extent to which wintertime CONUS precipitation during El Niño events can be explained by seasonal sea surface temperature heating patterns and the extent to which the precipitation is a product of natural variability. In this work, we define two seasonal indices based on the zonal wind field spanning from the eastern Pacific to the western Atlantic over CONUS that can explain El Niño precipitation variation spatially throughout CONUS over 11 historic El Niño events from 1950 to 2016. The indices reconstruct El Niño event wintertime (Jan-Mar) gridded precipitation over CONUS through cross-validated regression much better than the traditional ENSO sea surface temperature indices or other known modes of variability. Lastly, we show strong relationships between sea surface temperature patterns and the phases of the zonal wind indices, which in turn suggests that some of the disparate CONUS precipitation during El Niño events can be explained by different heating patterns. The primary contribution of this work is the identification of intermediate variables (in the form of zonal wind indices) that can facilitate further studies into the distinct hydroclimatic response to specific El Niño events.

  10. Synthetic thermosphere winds based on CHAMP neutral and plasma density measurements

    NASA Astrophysics Data System (ADS)

    Gasperini, F.; Forbes, J. M.; Doornbos, E. N.; Bruinsma, S. L.

    2016-04-01

    Meridional winds in the thermosphere are key to understanding latitudinal coupling and thermosphere-ionosphere coupling, and yet global measurements of this wind component are scarce. In this work, neutral and electron densities measured by the Challenging Minisatellite Payload (CHAMP) satellite at solar low and geomagnetically quiet conditions are converted to pressure gradient and ion drag forces, which are then used to solve the horizontal momentum equation to estimate low latitude to midlatitude zonal and meridional "synthetic" winds. We validate the method by showing that neutral and electron densities output from National Center for Atmospheric Research (NCAR) Thermosphere Ionosphere Mesosphere Electrodynamics-General Circulation Model (TIME-GCM) can be used to derive solutions to the momentum equations that replicate reasonably well (over 85% of the variance) the winds self-consistently calculated within the TIME-GCM. CHAMP cross-track winds are found to share over 65% of the variance with the synthetic zonal winds, providing further reassurance that this wind product should provide credible results. Comparisons with the Horizontal Wind Model 14 (HWM14) show that the empirical model largely underestimates wind speeds and does not reproduce much of the observed variability. Additionally, in this work we reveal the longitude, latitude, local time, and seasonal variability in the winds; show evidence of ionosphere-thermosphere (IT) coupling, with enhanced postsunset eastward winds due to depleted ion drag; demonstrate superrotation speeds of ˜27 m/s at the equator; discuss vertical wave coupling due the diurnal eastward propagating tide with zonal wave number 3 and the semidiurnal eastward propagating tide with zonal wave number 2.

  11. Mixture distributions of wind speed in the UAE

    NASA Astrophysics Data System (ADS)

    Shin, J.; Ouarda, T.; Lee, T. S.

    2013-12-01

    Wind speed probability distribution is commonly used to estimate potential wind energy. The 2-parameter Weibull distribution has been most widely used to characterize the distribution of wind speed. However, it is unable to properly model wind speed regimes when wind speed distribution presents bimodal and kurtotic shapes. Several studies have concluded that the Weibull distribution should not be used for frequency analysis of wind speed without investigation of wind speed distribution. Due to these mixture distributional characteristics of wind speed data, the application of mixture distributions should be further investigated in the frequency analysis of wind speed. A number of studies have investigated the potential wind energy in different parts of the Arabian Peninsula. Mixture distributional characteristics of wind speed were detected from some of these studies. Nevertheless, mixture distributions have not been employed for wind speed modeling in the Arabian Peninsula. In order to improve our understanding of wind energy potential in Arabian Peninsula, mixture distributions should be tested for the frequency analysis of wind speed. The aim of the current study is to assess the suitability of mixture distributions for the frequency analysis of wind speed in the UAE. Hourly mean wind speed data at 10-m height from 7 stations were used in the current study. The Weibull and Kappa distributions were employed as representatives of the conventional non-mixture distributions. 10 mixture distributions are used and constructed by mixing four probability distributions such as Normal, Gamma, Weibull and Extreme value type-one (EV-1) distributions. Three parameter estimation methods such as Expectation Maximization algorithm, Least Squares method and Meta-Heuristic Maximum Likelihood (MHML) method were employed to estimate the parameters of the mixture distributions. In order to compare the goodness-of-fit of tested distributions and parameter estimation methods for

  12. WIND SPEED Monitoring in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Bulygina, O.; Korshunova, N. N.; Razuvaev, V. N.; Groisman, P. Y.

    2016-12-01

    The wind regime of Russia varies a great deal due to the large size of the country's territory and variety of climate and terrain conditions. Changes in the regime of surface wind are of great practical importance. They can affect heat and water balance. Strong wind is one of the most hazardous meteorological event for various sectors of economy and for infrastructure. The main objective of this research is to monitoring wind speed change in Northern Eurasia At meteorological stations wind speed and wind direction are measured at the height of 10-12 meters over the land surface with the help of wind meters or wind wanes. Calculations were made on the basis of data for the period of 1980-2015. It allowed the massive scale disruption of homogeneity to be eliminated and sufficient period needed to obtain sustainable statistic characteristics to be retained. Data on average and maximum wind speed measured at 1457 stations of Russia were used. The analysis of changes in wind characteristics was made on the basis of point data and series of average characteristics obtained for 18 quasi-homogeneous climatic regions. Statistical characteristics (average and maximum values of wind speed, prevailing wind direction, values of the boundary of the 90%, 95% and 99%-confidence interval in the distribution of maximum wind speed) were obtained for all seasons and for the year as a whole. Values of boundaries of the 95% and 99%-confidence interval in the distribution of maximum wind speed were considered as indicators of extremeness of the wind regime. The trend of changes in average and maximum wind speed was assessed with a linear trend coefficient. A special attention was paid to wind changes in the Arctic where dramatic changes in surface air temperature and sea ice extent and density have been observed during the past decade. The analysis of the results allowed seasonal and regional features of changes in the wind regime on the territory of the northern part of Eurasia to be

  13. Hubble Space Telescope observations of the 1990 equatorial disturbance on Saturn - Zonal winds and central meridian albedos

    NASA Astrophysics Data System (ADS)

    Barnet, C. D.; Westphal, J. A.; Beebe, R. F.; Huber, L. F.

    1992-12-01

    The present comparison of two sets of HST data from August and November 1990 with Voyager 1 and 2 data acquired in 1980 and 1981 gives attention to Saturn's equatorial-region disturbance of September 1990. Longitudinal variations in the equatorial zonal winds are interpreted as evidence for interaction between the storm nucleus that was generated during the disturbance and the local wind field.

  14. A preliminary comparison of Na lidar and meteor radar zonal winds during quiet and sub-storm conditions

    NASA Astrophysics Data System (ADS)

    Grandhi, Kishore Kumar; Nesse Tyssøy, Hilde; Williams, Bifford P.; Stober, Gunter

    2017-04-01

    It is speculated that sufficiently large electric fields during geomagnetic disturbed conditions may decouple the meteor trail electron motions from the background neutral winds and leads to erroneous neutral wind estimation. As per our knowledge, the potential errors have never been reported. In the present case study, we have been using co-located meteor radar and sodium resonance lidar zonal wind measurements over Andenes (69.27oN,16.04oE) during intense sub storms in the declining phase of Jan 2005 solar proton event (21-22 Jan 2005). In total 14 hours of continuous measurements are available for the comparison, which covers both quiet and disturbed conditions. For comparison, the lidar zonal winds are averaged in meteor radar time and height bins. High cross correlations (˜0.8) are found in all height regions. The discrepancies can be explained in the light of differences in the observational volumes of the two instruments. Further, we extended the comparison to address the ionization impact on the meteor radar winds. For quiet hours, the observed meteor radar winds are quite consistent with lidar winds. While during the disturbed hours comparatively large differences are noticed at higher most altitudes. This might be due to ionization impact on meteor radar winds. At the present one event is not sufficient to make any consolidate conclusion. However, at least from this study we found some effect on the neutral wind measurements for the meteor radar. Further study with more co-located measurements are needed to test statistical significance of the result.

  15. A preliminary comparison of Na lidar and meteor radar zonal winds during geomagnetic quiet and disturbed conditions

    NASA Astrophysics Data System (ADS)

    Kishore Kumar, G.; Nesse Tyssøy, H.; Williams, Bifford P.

    2018-03-01

    We investigate the possibility that sufficiently large electric fields and/or ionization during geomagnetic disturbed conditions may invalidate the assumptions applied in the retrieval of neutral horizontal winds from meteor and/or lidar measurements. As per our knowledge, the possible errors in the wind estimation have never been reported. In the present case study, we have been using co-located meteor radar and sodium resonance lidar zonal wind measurements over Andenes (69.27°N, 16.04°E) during intense substorms in the declining phase of the January 2005 solar proton event (21-22 January 2005). In total, 14 h of measurements are available for the comparison, which covers both quiet and disturbed conditions. For comparison, the lidar zonal wind measurements are averaged over the same time and altitude as the meteor radar wind measurements. High cross correlations (∼0.8) are found in all height regions. The discrepancies can be explained in light of differences in the observational volumes of the two instruments. Further, we extended the comparison to address the electric field and/or ionization impact on the neutral wind estimation. For the periods of low ionization, the neutral winds estimated with both instruments are quite consistent with each other. During periods of elevated ionization, comparatively large differences are noticed at the highermost altitude, which might be due to the electric field and/or ionization impact on the wind estimation. At present, one event is not sufficient to make any firm conclusion. Further study with more co-located measurements are needed to test the statistical significance of the result.

  16. A nonlinear dynamics approach for incorporating wind-speed patterns into wind-power project evaluation.

    PubMed

    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.

  17. A Novel Wind Speed Forecasting Model for Wind Farms of Northwest China

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Zhou; Wang, Yun

    2017-01-01

    Wind resources are becoming increasingly significant due to their clean and renewable characteristics, and the integration of wind power into existing electricity systems is imminent. To maintain a stable power supply system that takes into account the stochastic nature of wind speed, accurate wind speed forecasting is pivotal. However, no single model can be applied to all cases. Recent studies show that wind speed forecasting errors are approximately 25% to 40% in Chinese wind farms. Presently, hybrid wind speed forecasting models are widely used and have been verified to perform better than conventional single forecasting models, not only in short-term wind speed forecasting but also in long-term forecasting. In this paper, a hybrid forecasting model is developed, the Similar Coefficient Sum (SCS) and Hermite Interpolation are exploited to process the original wind speed data, and the SVM model whose parameters are tuned by an artificial intelligence model is built to make forecast. The results of case studies show that the MAPE value of the hybrid model varies from 22.96% to 28.87 %, and the MAE value varies from 0.47 m/s to 1.30 m/s. Generally, Sign test, Wilcoxon's Signed-Rank test, and Morgan-Granger-Newbold test tell us that the proposed model is different from the compared models.

  18. A Nonlinear Dynamics Approach for Incorporating Wind-Speed Patterns into Wind-Power Project Evaluation

    PubMed Central

    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. PMID:25617767

  19. Modeling wind adjustment factor and midflame wind speed for Rothermel's surface fire spread model

    Treesearch

    Patricia L. Andrews

    2012-01-01

    Rothermel's surface fire spread model was developed to use a value for the wind speed that affects surface fire, called midflame wind speed. Models have been developed to adjust 20-ft wind speed to midflame wind speed for sheltered and unsheltered surface fuel. In this report, Wind Adjustment Factor (WAF) model equations are given, and the BehavePlus fire modeling...

  20. Transient response of sap flow to wind speed.

    PubMed

    Chu, Chia R; Hsieh, Cheng-I; Wu, Shen-Yuang; Phillips, Nathan G

    2009-01-01

    Transient responses of sap flow to step changes in wind speed were experimentally investigated in a wind tunnel. A Granier-type sap flow sensor was calibrated and tested in a cylindrical tube for analysis of its transient time response. Then the sensor was used to measure the transient response of a well-watered Pachira macrocarpa plant to wind speed variations. The transient response of sap flow was described using the resistance-capacitance model. The steady sap flow rate increased as the wind speed increased at low wind speeds. Once the wind speed exceeded 8.0 m s(-1), the steady sap flow rate did not increase further. The transpiration rate, measured gravimetrically, showed a similar trend. The response of nocturnal sap flow to wind speed variation was also measured and compared with the results in the daytime. Under the same wind speed, the steady sap flow rate was smaller than that in the daytime, indicating differences between diurnal and nocturnal hydraulic function, and incomplete stomatal closure at night. In addition, it was found that the temporal response of the Granier sensor is fast enough to resolve the transient behaviour of water flux in plant tissue.

  1. Indexed semi-Markov process for wind speed modeling.

    NASA Astrophysics Data System (ADS)

    Petroni, F.; D'Amico, G.; Prattico, F.

    2012-04-01

    The increasing interest in renewable energy leads scientific research to find a better way to recover most of the available energy. Particularly, the maximum energy recoverable from wind is equal to 59.3% of that available (Betz law) at a specific pitch angle and when the ratio between the wind speed in output and in input is equal to 1/3. The pitch angle is the angle formed between the airfoil of the blade of the wind turbine and the wind direction. Old turbine and a lot of that actually marketed, in fact, have always the same invariant geometry of the airfoil. This causes that wind turbines will work with an efficiency that is lower than 59.3%. New generation wind turbines, instead, have a system to variate the pitch angle by rotating the blades. This system able the wind turbines to recover, at different wind speed, always the maximum energy, working in Betz limit at different speed ratios. A powerful system control of the pitch angle allows the wind turbine to recover better the energy in transient regime. A good stochastic model for wind speed is then needed to help both the optimization of turbine design and to assist the system control to predict the value of the wind speed to positioning the blades quickly and correctly. The possibility to have synthetic data of wind speed is a powerful instrument to assist designer to verify the structures of the wind turbines or to estimate the energy recoverable from a specific site. To generate synthetic data, Markov chains of first or higher order are often used [1,2,3]. In particular in [1] is presented a comparison between a first-order Markov chain and a second-order Markov chain. A similar work, but only for the first-order Markov chain, is conduced by [2], presenting the probability transition matrix and comparing the energy spectral density and autocorrelation of real and synthetic wind speed data. A tentative to modeling and to join speed and direction of wind is presented in [3], by using two models, first

  2. Hourly Wind Speed Interval Prediction in Arid Regions

    NASA Astrophysics Data System (ADS)

    Chaouch, M.; Ouarda, T.

    2013-12-01

    The long and extended warm and dry summers, the low rate of rain and humidity are the main factors that explain the increase of electricity consumption in hot arid regions. In such regions, the ventilating and air-conditioning installations, that are typically the most energy-intensive among energy consumption activities, are essential for securing healthy, safe and suitable indoor thermal conditions for building occupants and stored materials. The use of renewable energy resources such as solar and wind represents one of the most relevant solutions to overcome the increase of the electricity demand challenge. In the recent years, wind energy is gaining more importance among the researchers worldwide. Wind energy is intermittent in nature and hence the power system scheduling and dynamic control of wind turbine requires an estimate of wind energy. Accurate forecast of wind speed is a challenging task for the wind energy research field. In fact, due to the large variability of wind speed caused by the unpredictable and dynamic nature of the earth's atmosphere, there are many fluctuations in wind power production. This inherent variability of wind speed is the main cause of the uncertainty observed in wind power generation. Furthermore, producing wind power forecasts might be obtained indirectly by modeling the wind speed series and then transforming the forecasts through a power curve. Wind speed forecasting techniques have received substantial attention recently and several models have been developed. Basically two main approaches have been proposed in the literature: (1) physical models such as Numerical Weather Forecast and (2) statistical models such as Autoregressive integrated moving average (ARIMA) models, Neural Networks. While the initial focus in the literature has been on point forecasts, the need to quantify forecast uncertainty and communicate the risk of extreme ramp events has led to an interest in producing probabilistic forecasts. In short term

  3. Cloud level winds from UV and IR images obtained by VMC onboard Venus Express

    NASA Astrophysics Data System (ADS)

    Khatuntsev, Igor; Patsaeva, Marina; Titov, Dmitri; Ignatiev, Nikolay; Turin, Alexander; Bertaux, Jean-Loup

    2017-04-01

    During eight years Venus Monitoring Camera (VMC) [1] onboard the Venus Express orbiter has observed the upper cloud layer of Venus. The largest set of images was obtained in the UV (365 nm), visible (513 nm) and two infrared channels - 965 nm and 1010 nm. The UV dayside images were used to study the atmospheric circulation at the Venus cloud tops [2], [3]. Mean zonal and meridional profiles of winds and their variability were derived from cloud tracking of UV images. In low latitudes the mean retrograde zonal wind at the cloud top (67±2 km) is about 95 m/s with a maximum of about 102 m/s at 40-50°S. Poleward from 50°S the zonal wind quickly fades out with latitude. The mean poleward meridional wind slowly increases from zero value at the equator to about 10 m/s at 50°S. Poleward from this latitude, the absolute value of the meridional component monotonically decreases to zero at the pole. The VMC observations suggest clear diurnal signature in the wind field. They also indicate a long term trend for the zonal wind speed at low latitudes to increase from 85 m/s in the beginning of the mission to 110 m/s by the middle of 2012. The trend was explained by influence of the surface topography on the zonal flow [4]. Cloud features tracking in the IR images provided information about winds in the middle cloud deck (55±4 km). In the low and middle latitudes (5-65°S) the IR mean retrograde zonal velocity is about 68-70 m/s. In contrast to poleward flow at the cloud tops, equatorward motions dominate in the middle cloud with maximum speed of 5.8±1.2 m/s at latitude 15°S. The meridional speed slowly decreases to 0 at 65-70°S. At low latitudes the zonal and meridional speed demonstrate long term variations. Following [4] we explain the observed long term trend of zonal and meridional components by the influence of surface topography of highland region Aphrodite Terra on dynamic processes in the middle cloud deck through gravity waves. Acknowledgements: I.V. Khatuntsev

  4. Comparison of horizontal winds from the LIMS satellite instrument with rocket measurements

    NASA Technical Reports Server (NTRS)

    Smith, A. K.; Bailey, P. L.

    1985-01-01

    Statistical results are given for a comparison between horizontal geostrophic winds computed from satellite height data and all available in situ rocket wind soundings during a 7-month period. The satellite data are the daily mapped fields from the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) instrument, which extend from 100 to 0.1 mbar. Results indicate that in both the tropics and the extratropical Northern Hemisphere, the average zonal and meridional wind speeds agree to within 2-4 m/s throughout the stratosphere. The rms differences are much larger, with values of 5-10 m/s in the lower stratosphere, increasing to 20-40 m/s in the lower mesosphere. Time series show that LIMS and rocketsonde zonal wind speeds show coherent variations with temporal periods of 1-2 weeks and more, and both exhibit irregular variations on time scales of less than one week.

  5. Intra-seasonal Oscillations (ISO) of Zonal-Mean Meridional Winds and Temperatures as Measured by UARS

    NASA Technical Reports Server (NTRS)

    Huang, Frank T.; Mayr, Hans G.; Reber, Carl A.

    2004-01-01

    Based on an empirical analysis of measurements with the High Resolution Doppler Imager (HRDI) on the UARS spacecraft in the upper mesosphere (95 km), persistent and regular intra-seasonal oscillations (ISO) with periods of about 2 to 4 months have recently been reported in the zonal-mean meridional winds. Similar oscillations have also been discussed independently in a modeling study, and they were attributed to wave-mean-flow interactions. The observed and modeled meridional wind ISOs were largely confined to low latitudes. We report here an analysis of concurrent temperature measurements on UARS, which produces oscillations similar to those seen in the meridional winds. Although the temperature oscillations are observed at lower altitudes (55 km), their phase variations with latitude are qualitatively consistent with the inferred properties seen in the meridional winds and thus provide independent evidence for the existence of ISOs in the mesosphere.

  6. Reliability of Wind Speed Data from Satellite Altimeter to Support Wind Turbine Energy

    NASA Astrophysics Data System (ADS)

    Uti, M. N.; Din, A. H. M.; Omar, A. H.

    2017-10-01

    Satellite altimeter has proven itself to be one of the important tool to provide good quality information in oceanographic study. Nowadays, most countries in the world have begun in implementation the wind energy as one of their renewable energy for electric power generation. Many wind speed studies conducted in Malaysia using conventional method and scientific technique such as anemometer and volunteer observing ships (VOS) in order to obtain the wind speed data to support the development of renewable energy. However, there are some limitations regarding to this conventional method such as less coverage for both spatial and temporal and less continuity in data sharing by VOS members. Thus, the aim of this research is to determine the reliability of wind speed data by using multi-mission satellite altimeter to support wind energy potential in Malaysia seas. Therefore, the wind speed data are derived from nine types of satellite altimeter starting from year 1993 until 2016. Then, to validate the reliability of wind speed data from satellite altimeter, a comparison of wind speed data form ground-truth buoy that located at Sabah and Sarawak is conducted. The validation is carried out in terms of the correlation, the root mean square error (RMSE) calculation and satellite track analysis. As a result, both techniques showing a good correlation with value positive 0.7976 and 0.6148 for point located at Sabah and Sarawak Sea, respectively. It can be concluded that a step towards the reliability of wind speed data by using multi-mission satellite altimeter can be achieved to support renewable energy.

  7. Dynamics in the Modern Upper Atmosphere of Venus: Zonal Wind Transition to Subsolar-to-Antisolar Flow

    NASA Astrophysics Data System (ADS)

    Livengood, T. A.; Kostiuk, T.; Hewagama, T.; Fast, K. E.

    2017-12-01

    We observed Venus on 19-23 Aug 2010 (UT) to investigate equatorial wind velocities from above the cloud tops through the lower thermosphere. Measurements were made from the NASA Infrared Telescope Facility using the NASA Goddard Space Flight Center Heterodyne Instrument for Planetary Winds and Composition. High-resolution spectra were acquired on a CO2 pressure-broadened absorption feature that probes the lower mesosphere ( 70 km altitude) with a non-LTE core emission of the same transition that probes the lower thermosphere ( 110 km). The resolving power of λ/Δλ≈3×107 determines line-of-sight velocity from Doppler shifts to high precision. The altitude differential between the features enables investigating the transition from zonal wind flow near the cloud tops to subsolar-to-antisolar flow in the thermosphere. The fully-resolved carbon dioxide transition was measured near 952.8808 cm-1 (10.494 µm) rest frequency at the equator with 1 arcsec field-of-view on Venus (24 arcsec diameter) distributed about the central meridian and across the terminator at ±15° intervals in longitude. The non-LTE emission is solar-pumped and appears only on the daylight side, probing subsolar-to-antisolar wind velocity vector flowing radially from the subsolar point through the terminator, which was near the central meridian in these observations and had zero line-of-sight wind projection at the terminator. The velocity of the zonal flow is approximately uniform, with maximum line-of-sight projection at the limb, and can be measured by the frequency of the absorption line on both the daylight and dark side. Variations in Doppler shift between the observable features and the differing angular dependence of the contributing wind phenomena thus provide independent mechanisms to distinguish the dynamical processes at the altitude of each observed spectral feature. Winds up to >100 m/s were determined in previous investigations with uncertainties of order 10 m/s or less.

  8. ECMWF and SSM/I global surface wind speeds

    NASA Technical Reports Server (NTRS)

    Halpern, David; Hollingsworth, Anthony; Wentz, Frank

    1994-01-01

    Monthly mean 2.5 deg x 2.5 deg resolution 10-m height wind speeds from the Special Sensor Microwave/Imager (SSM/I) instrument and the European Centre for Medium-Range Weather Forecasts (ECMWF) forecast-analysis system are compared between 60 deg S and 60 deg N during 1988-91. The SSM/I data were uniformly processed while numerous changes were made to the ECMWF forecast-analysis system. The SSM/I measurements, which were compared with moored-buoy wind observations, were used as a reference dataset to evaluate the influence of the changes made to the ECMWF system upon the ECMWF surface wind speed over the ocean. A demonstrable yearly decrease of the difference between SSM/I and ECMWF wind speeds occurred in the 10 deg S-10 deg N region, including the 5 deg S-5 deg N zone of the Pacific Ocean, where nearly all of the variations occurred in the 160 deg E-160 deg W region. The apparent improvement of the ECMWF wind speed occurred at the same time as the yearly decrease of the equatorial Pacific SSM/I wind speed, which was associated with the natural transition from La Nina to El Nino conditions. In the 10 deg S-10 deg N tropical Atlantic, the ECMWF wind speed had a 4-yr trend, which was not expected nor was it duplicated with the SSM/I data. No yearly trend was found in the difference between SSM/I and ECMWF surface wind speeds in middle latitudes of the Northern and Southern Hemispheres. The magnitude of the differences between SSM/I and ECMWF was 0.4 m/s or 100% larger in the Northern than in the Southern Hemisphere extratropics. In two areas (Arabian Sea and North Atlantic Ocean) where ECMWF and SSM/I wind speeds were compared to ship measurements, the ship data had much better agreement with the ECMWF analyses compared to SSM/I data. In the 10 deg S-10 deg N area the difference between monthly standard deviations of the daily wind speeds dropped significantly from 1988 to 1989 but remained constant at about 30% for the remaining years.

  9. Jupiter cloud morphology and zonal winds from ground-based observations during Juno's first year around Jupiter

    NASA Astrophysics Data System (ADS)

    Hueso, R.; Sánchez-Lavega, A.; Gómez-Forrellad, J. M.; Rojas, J. F.; Pérez-Hoyos, S.; Sanz-Requena, J. F.; Peralta, J.; Ordonez-Etxeberria, I.; Chen-Chen, H.; Mendikoa, I.; Peach, D.; Go, C.; Wesley, A.; Miles, P.; Olivetti, T.

    2017-09-01

    We present an analysis of Jupiter's atmospheric activity over Juno's first year around the planet based on ground-based observations. We present variability of the zonal winds associated to large outbreaks of convective activity at different belts in the planet, a study of short-scale atmospheric waves at low latitudes and examine polar views of the planet that can be compared with JunoCam observations.

  10. High-resolution daily gridded data sets of air temperature and wind speed for Europe

    NASA Astrophysics Data System (ADS)

    Brinckmann, Sven; Krähenmann, Stefan; Bissolli, Peter

    2016-10-01

    New high-resolution data sets for near-surface daily air temperature (minimum, maximum and mean) and daily mean wind speed for Europe (the CORDEX domain) are provided for the period 2001-2010 for the purpose of regional model validation in the framework of DecReg, a sub-project of the German MiKlip project, which aims to develop decadal climate predictions. The main input data sources are SYNOP observations, partly supplemented by station data from the ECA&D data set (http://www.ecad.eu). These data are quality tested to eliminate erroneous data. By spatial interpolation of these station observations, grid data in a resolution of 0.044° (≈ 5km) on a rotated grid with virtual North Pole at 39.25° N, 162° W are derived. For temperature interpolation a modified version of a regression kriging method developed by Krähenmann et al.(2011) is used. At first, predictor fields of altitude, continentality and zonal mean temperature are used for a regression applied to monthly station data. The residuals of the monthly regression and the deviations of the daily data from the monthly averages are interpolated using simple kriging in a second and third step. For wind speed a new method based on the concept used for temperature was developed, involving predictor fields of exposure, roughness length, coastal distance and ERA-Interim reanalysis wind speed at 850 hPa. Interpolation uncertainty is estimated by means of the kriging variance and regression uncertainties. Furthermore, to assess the quality of the final daily grid data, cross validation is performed. Variance explained by the regression ranges from 70 to 90 % for monthly temperature and from 50 to 60 % for monthly wind speed. The resulting RMSE for the final daily grid data amounts to 1-2 K and 1-1.5 ms-1 (depending on season and parameter) for daily temperature parameters

  11. Using Sentinel-1 SAR satellites to map wind speed variation across offshore wind farm clusters

    NASA Astrophysics Data System (ADS)

    James, S. F.

    2017-11-01

    Offshore wind speed maps at 500m resolution are derived from freely available satellite Synthetic Aperture Radar (SAR) data. The method for processing many SAR images to derive wind speed maps is described in full. The results are tested against coincident offshore mast data. Example wind speed maps for the UK Thames Estuary offshore wind farm cluster are presented.

  12. A PV view of the zonal mean distribution of temperature and wind in the extratropical troposphere

    NASA Technical Reports Server (NTRS)

    Sun, De-Zheng; Lindzen, Richard S.

    1994-01-01

    The dependence of the temperature and wind distribution of the zonal mean flow in the extratropical troposphere on the gradient of pontential vorticity along isentropes is examined. The extratropics here refer to the region outside the Hadley circulation. Of particular interest is whether the distribution of temperature and wind corresponding to a constant potential vorticity (PV) along isentropes resembles the observed, and the implications of PV homogenization along isentropes for the role of the tropics. With the assumption that PV is homogenized along isentropes, it is found that the temperature distribution in the extratropical troposphere may be determined by a linear, first-order partial differential equation. When the observed surface temperature distribution and tropical lapse rate are used as the boundary conditions, the solution of the equation is close to the observed temperature distribution except in the upper troposphere adjacent to the Hadley circulation, where the troposphere with no PV gradient is considerably colder. Consequently, the jet is also stronger. It is also found that the meridional distribution of the balanced zonal wind is very sensitive to the meridional distribution of the tropopause temperature. The result may suggest that the requirement of the global momentum balance has no practical role in determining the extratropical temperature distribution. The authors further investigated the sensitivity of the extratropical troposphere with constant PV along isentropes to changes in conditions at the tropical boundary (the edge of the Hadley circulation). It is found that the temperature and wind distributions in the extratropical troposphere are sensitive to the vertical distribution of PV at the tropical boundary. With a surface distribution of temperature that decreases linearly with latitude, the jet maximum occurs at the tropical boundary and moves with it. The overall pattern of wind distribution is not sensitive to the change of

  13. A multiple-fan active control wind tunnel for outdoor wind speed and direction simulation

    NASA Astrophysics Data System (ADS)

    Wang, Jia-Ying; Meng, Qing-Hao; Luo, Bing; Zeng, Ming

    2018-03-01

    This article presents a new type of active controlled multiple-fan wind tunnel. The wind tunnel consists of swivel plates and arrays of direct current fans, and the rotation speed of each fan and the shaft angle of each swivel plate can be controlled independently for simulating different kinds of outdoor wind fields. To measure the similarity between the simulated wind field and the outdoor wind field, wind speed and direction time series of two kinds of wind fields are recorded by nine two-dimensional ultrasonic anemometers, and then statistical properties of the wind signals in different time scales are analyzed based on the empirical mode decomposition. In addition, the complexity of wind speed and direction time series is also investigated using multiscale entropy and multivariate multiscale entropy. Results suggest that the simulated wind field in the multiple-fan wind tunnel has a high degree of similarity with the outdoor wind field.

  14. Frequency-dependent behavior of the barotropic and baroclinic modes of zonal jet variability

    NASA Astrophysics Data System (ADS)

    Sheshadri, A.; Plumb, R. A.

    2016-12-01

    Stratosphere-troposphere interactions are frequently described in terms of the leading modes of variability, i.e. the annular modes. An idealized dynamical core model is used to explore the differences between the low- and high- frequency (periods greater and less than 30 days) behavior of the first two principal components of zonal mean zonal wind and eddy kinetic energy, i.e., the barotropic/baroclinic annular modes of variability of the extratropical circulation. The modes show similar spatial characteristics in the different frequency ranges considered, however the ranking of the modes switches in some cases from one range to the other. There is some cancelation in the signatures of eddy heat flux and eddy kinetic energy in the leading low-pass and high-pass filtered zonal wind mode, partly explaining their small signature in the total. At low frequencies, the first zonal wind mode describes latitudinal shifts of both the midlatitude jet and its associated storm tracks, and the persistence of zonal wind anomalies appears to be sustained primarily by a baroclinic, rather than a barotropic, feedback. On shorter time scales, the behavior is more complicated and transient.

  15. ARE660 Wind Generator: Low Wind Speed Technology for Small Turbine Development

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Robert W. Preus; DOE Project Officer - Keith Bennett

    2008-04-23

    This project is for the design of a wind turbine that can generate most or all of the net energy required for homes and small businesses in moderately windy areas. The purpose is to expand the current market for residential wind generators by providing cost effective power in a lower wind regime than current technology has made available, as well as reduce noise and improve reliability and safety. Robert W. Preus’ experience designing and/or maintaining residential wind generators of many configurations helped identify the need for an improved experience of safety for the consumer. Current small wind products have unreliablemore » or no method of stopping the wind generator in fault or high wind conditions. Consumers and their neighbors do not want to hear their wind generators. In addition, with current technology, only sites with unusually high wind speeds provide payback times that are acceptable for the on-grid user. Abundant Renewable Energy’s (ARE) basic original concept for the ARE660 was a combination of a stall controlled variable speed small wind generator and automatic fail safe furling for shutdown. The stall control for a small wind generator is not novel, but has not been developed for a variable speed application with a permanent magnet alternator (PMA). The fail safe furling approach for shutdown has not been used to our knowledge.« less

  16. LIDAR wind speed measurements at a Taiwan onshore wind park

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Ting; Lin, Ta-Hui; Hsuan, Chung-Yao; Li, Yu-Cheng; Yang, Ya-Fei; Tai, Tzy-Hwan; Huang, Chien-Cheng

    2016-04-01

    Measurements of wind speed and wind direction were carried out using a Leosphere Windcube LIDAR system at a Taiwan onshore wind park. The Lidar shot a total of five laser beams to the atmosphere to collect the light-of-sight (LOS) velocity. Four beams were sent successively in four cardinal directions along a 28° scanning cone angle, followed by a fifth, vertical beam. An unchangeable sampling rate of approximately 1.2 Hz was set in the LIDAR system to collect the LOS velocity. The supervisory control and data acquisition (SCADA) data from two GE 1.5 MW wind turbines near the LIDAR deployment site were acquired for the whole measuring period from February 4 to February 16 of 2015. The SCADA data include the blade angular velocity, the wind velocity measured at hub height from an anemometer mounted on the nacelle, the wind turbine yaw angle, and power production; each parameter was recorded as averages over 1-min periods. The data analysis involving the LIDAR measurements and the SCADA data were performed to obtain the turbulent flow statistics. The results show that the turbine power production has significant dependence to the wind speed, wind direction, turbulence intensity and wind shear.

  17. Wind speed statistics for Goldstone, California, anemometer sites

    NASA Technical Reports Server (NTRS)

    Berg, M.; Levy, R.; Mcginness, H.; Strain, D.

    1981-01-01

    An exploratory wind survey at an antenna complex was summarized statistically for application to future windmill designs. Data were collected at six locations from a total of 10 anemometers. Statistics include means, standard deviations, cubes, pattern factors, correlation coefficients, and exponents for power law profile of wind speed. Curves presented include: mean monthly wind speeds, moving averages, and diurnal variation patterns. It is concluded that three of the locations have sufficiently strong winds to justify consideration for windmill sites.

  18. Statistical distribution of wind speeds and directions globally observed by NSCAT

    NASA Astrophysics Data System (ADS)

    Ebuchi, Naoto

    1999-05-01

    In order to validate wind vectors derived from the NASA scatterometer (NSCAT), statistical distributions of wind speeds and directions over the global oceans are investigated by comparing with European Centre for Medium-Range Weather Forecasts (ECMWF) wind data. Histograms of wind speeds and directions are calculated from the preliminary and reprocessed NSCAT data products for a period of 8 weeks. For wind speed of the preliminary data products, excessive low wind distribution is pointed out through comparison with ECMWF winds. A hump at the lower wind speed side of the peak in the wind speed histogram is discernible. The shape of the hump varies with incidence angle. Incompleteness of the prelaunch geophysical model function, SASS 2, tentatively used to retrieve wind vectors of the preliminary data products, is considered to cause the skew of the wind speed distribution. On the contrary, histograms of wind speeds of the reprocessed data products show consistent features over the whole range of incidence angles. Frequency distribution of wind directions relative to spacecraft flight direction is calculated to assess self-consistency of the wind directions. It is found that wind vectors of the preliminary data products exhibit systematic directional preference relative to antenna beams. This artificial directivity is also considered to be caused by imperfections in the geophysical model function. The directional distributions of the reprocessed wind vectors show less directivity and consistent features, except for very low wind cases.

  19. Hi-Q Rotor - Low Wind Speed Technology

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Todd E. Mills; Judy Tatum

    The project objective was to optimize the performance of the Hi-Q Rotor. Early research funded by the California Energy Commission indicated the design might be advantageous over state-of-the-art turbines for collecting wind energy in low wind conditions. The Hi-Q Rotor is a new kind of rotor targeted for harvesting wind in Class 2, 3, and 4 sites, and has application in areas that are closer to cities, or 'load centers.' An advantage of the Hi-Q Rotor is that the rotor has non-conventional blade tips, producing less turbulence, and is quieter than standard wind turbine blades which is critical to themore » low-wind populated urban sites. Unlike state-of-the-art propeller type blades, the Hi-Q Rotor has six blades connected by end caps. In this phase of the research funded by DOE's Inventions and Innovation Program, the goal was to improve the current design by building a series of theoretical and numeric models, and composite prototypes to determine a best of class device. Development of the rotor was performed by aeronautical engineering and design firm, DARcorporation. From this investigation, an optimized design was determined and an 8-foot diameter, full-scale rotor was built and mounted using a Bergey LX-1 generator and furling system which were adapted to support the rotor. The Hi-Q Rotor was then tested side-by-side against the state-of-the-art Bergey XL-1 at the Alternative Energy Institute's Wind Test Center at West Texas State University for six weeks, and real time measurements of power generated were collected and compared. Early wind tunnel testing showed that the cut-in-speed of the Hi-Q rotor is much lower than a conventional tested HAWT enabling the Hi-Q Wind Turbine to begin collecting energy before a conventional HAWT has started spinning. Also, torque at low wind speeds for the Hi-Q Wind Turbine is higher than the tested conventional HAWT and enabled the wind turbine to generate power at lower wind speeds. Based on the data collected, the

  20. Geographic distribution of zonal wind and UV albedo at cloud top level from VMC camera on Venus Express: Influence of Venus topography through stationary gravity waves vertical propagation.

    NASA Astrophysics Data System (ADS)

    Bertaux, Jean-Loup; Khatunstsev, Igor; Hauchecorne, Alain; Markiewicz, Wojciech; Marcq, Emmanuel; Lebonnois, Sébastien; Patsaeva, Marina; Turin, Alexander

    2015-04-01

    UV images (at 365 nm) of Venus cloud top collected with VMC camera on board Venus Express allowed to derive a large number of wind measurements at altitude 67±2 km from tracking of cloud features in the period 2006-2012. Both manual (45,600) and digital (391,600) individual wind measurements over 127 orbits were analyzed showing various patterns with latitude and local time. A new longitude-latitude geographic map of the zonal wind shows a conspicuous region of strongly decreased zonal wind, a remarkable feature that was unknown up to now. While the average zonal wind near equator (from 5°S to 15°s) is -100.9 m/s in the longitude range 200-330°, it reaches -83.4 m/s in the range 60-100°, a difference of 17.5 m/s. When compared to the altimetry map of Venus, it is found that the zonal wind pattern is well correlated with the underlying relief in the region of Aphrodite Terra, with a downstream shift of about 30° (˜3,200 km). We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to cloud top level, break there and transfer their momentum to the zonal flow. A similar phenomenon is known to operate on Earth with an influence on mesospheric winds. The LMD-GCM for Venus was run with or without topography, with and without a parameterization of gravity waves and does not display such an observed change of velocity near equator. The cloud albedo map at 365 nm varies also in longitude and latitude. We speculate that it might be the result of increased vertical mixing associated to wave breaking, and decreased abundance of the UV absorber which makes the contrast in images. The impact of these new findings on current super rotation theories remains to be assessed. This work was triggered by the presence of a conspicuous peak at 117 days in a time series of wind measurements. This is the length of the solar day as seen at the

  1. New results on equatorial thermospheric winds and temperatures from Ethiopia, Africa

    NASA Astrophysics Data System (ADS)

    Tesema, Fasil; Mesquita, Rafael; Meriwether, John; Damtie, Baylie; Nigussie, Melessew; Makela, Jonathan; Fisher, Daniel; Harding, Brian; Yizengaw, Endawoke; Sanders, Samuel

    2017-03-01

    Measurements of equatorial thermospheric winds, temperatures, and 630 nm relative intensities were obtained using an imaging Fabry-Perot interferometer (FPI), which was recently deployed at Bahir Dar University in Ethiopia (11.6° N, 37.4° E, 3.7° N magnetic). The results obtained in this study cover 6 months (53 nights of useable data) between November 2015 and April 2016. The monthly-averaged values, which include local winter and equinox seasons, show the magnitude of the maximum monthly-averaged zonal wind is typically within the range of 70 to 90 ms-1 and is eastward between 19:00 and 21:00 LT. Compared to prior studies of the equatorial thermospheric wind for this local time period, the magnitude is considerably weaker as compared to the maximum zonal wind speed observed in the Peruvian sector but comparable to Brazilian FPI results. During the early evening, the meridional wind speeds are 30 to 50 ms-1 poleward during the winter months and 10 to 25 ms-1 equatorward in the equinox months. The direction of the poleward wind during the winter months is believed to be mainly caused by the existence of the interhemispheric wind flow from the summer to winter hemispheres. An equatorial wind surge is observed later in the evening and is shifted to later local times during the winter months and to earlier local times during the equinox months. Significant night-to-night variations are also observed in the maximum speed of both zonal and meridional winds. The temperature observations show the midnight temperature maximum (MTM) to be generally present between 00:30 and 02:00 LT. The amplitude of the MTM was ˜ 110 K in January 2016 with values smaller than this in the other months. The local time difference between the appearance of the MTM and a pre-midnight equatorial wind was generally 60 to 180 min. A meridional wind reversal was also observed after the appearance of the MTM (after 02:00 LT). Climatological models, HWM14 and MSIS-00, were compared to the

  2. Critical wind speed at which trees break

    NASA Astrophysics Data System (ADS)

    Virot, E.; Ponomarenko, A.; Dehandschoewercker, É.; Quéré, D.; Clanet, C.

    2016-02-01

    Data from storms suggest that the critical wind speed at which trees break is constant (≃42 m /s ), regardless of tree characteristics. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke's law, Griffith's criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees.

  3. Critical wind speed at which trees break.

    PubMed

    Virot, E; Ponomarenko, A; Dehandschoewercker, É; Quéré, D; Clanet, C

    2016-02-01

    Data from storms suggest that the critical wind speed at which trees break is constant (≃42m/s), regardless of tree characteristics. We question the physical origin of this observation both experimentally and theoretically. By combining Hooke's law, Griffith's criterion, and tree allometry, we show that the critical wind speed indeed hardly depends on the height, diameter, and elastic properties of trees.

  4. Datasets on hub-height wind speed comparisons for wind farms in California.

    PubMed

    Wang, Meina; Ullrich, Paul; Millstein, Dev

    2018-08-01

    This article includes the description of data information related to the research article entitled "The future of wind energy in California: Future projections with the Variable-Resolution CESM"[1], with reference number RENE_RENE-D-17-03392. Datasets from the Variable-Resolution CESM, Det Norske Veritas Germanischer Lloyd Virtual Met, MERRA-2, CFSR, NARR, ISD surface observations, and upper air sounding observations were used for calculating and comparing hub-height wind speed at multiple major wind farms across California. Information on hub-height wind speed interpolation and power curves at each wind farm sites are also presented. All datasets, except Det Norske Veritas Germanischer Lloyd Virtual Met, are publicly available for future analysis.

  5. Relationship between wind speed and gas exchange over the ocean

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Rik

    1992-01-01

    A quadratic dependence of gas exchange on wind speed is employed to analyze the relationship between gas transfer and wind speed with particular emphasizing variable and/or low wind speeds. The quadratic dependence is fit through gas-transfer velocities over the ocean determined by methods based on the natural C-14 disequilibrium and the bomb C-14 inventory. The variation in the CO2 levels is related to these mechanisms, but the results show that other causes play significant roles. A weaker dependence of gas transfer on wind is suggested for steady winds, and long-term averaged winds demonstrate a stronger dependence in the present model. The chemical enhancement of CO2 exchange is also shown to play a role by increasing CO2 fluxes at low wind speeds.

  6. Observed and Aogcm Simulated Relationships Between us Wind Speeds and Large Scale Modes of Climate Variability

    NASA Astrophysics Data System (ADS)

    Schoof, J. T.; Pryor, S. C.; Barthelmie, R. J.

    2013-12-01

    Previous research has indicated that large-scale modes of climate variability, such as El Niño - Southern Oscillation (ENSO), the Arctic Oscillation (AO) and the Pacific-North American pattern (PNA), influence the inter-annual and intra-annual variability of near-surface and upper-level wind speeds over the United States. For example, we have shown that rawinsonde derived wind speeds indicate that 90th percentile of wind speeds at 700 hPa over the Pacific Northwest and Southwestern USA are significantly higher under the negative phase of the PNA, and the Central Plains experiences higher wind speeds at 850 hPa under positive phase Southern Oscillation index while the Northeast exhibits higher wind speeds at 850 hPa under positive phase NAO. Here, we extend this research by further investigating these relationships using both reanalysis products and output from coupled atmosphere-ocean general circulation models (AOGCMs) developed for the 5th Phase of the Coupled Model Intercomparison Project (CMIP5). The research presented has two specific goals. First, we evaluate the AOGCM simulations in terms of their ability to represent the temporal and spatial representations of ENSO, the AO, and the PNA pattern relative to historical observations. The diagnostics used include calculation of the power spectra (and thus representation of the fundamental frequencies of variability) and Taylor diagrams (for comparative assessment of the spatial patterns and their intensities). Our initial results indicate that most AOGCMs produce modes that are qualitatively similar to those observed, but that differ slightly in terms of the spatial pattern, intensity of specific centers of action, and variance explained. Figure 1 illustrates an example of the analysis of the frequencies of variability of two climate modes for the NCEP-NCAR reanalysis (NNR) and a single AOGCM (BCC CSM1). The results show a high degree of similarity in the power spectra but for this AOGCM the variance of the PNA

  7. Flight speed and performance of the wandering albatross with respect to wind.

    PubMed

    Richardson, Philip L; Wakefield, Ewan D; Phillips, Richard A

    2018-01-01

    Albatrosses and other large seabirds use dynamic soaring to gain sufficient energy from the wind to travel large distances rapidly and with little apparent effort. The recent development of miniature bird-borne tracking devices now makes it possible to explore the physical and biological implications of this means of locomotion in detail. Here we use GPS tracking and concurrent reanalyzed wind speed data to model the flight performance of wandering albatrosses Diomedea exulans soaring over the Southern Ocean. We investigate the extent to which flight speed and performance of albatrosses is facilitated or constrained by wind conditions encountered during foraging trips. We derived simple equations to model observed albatross ground speed as a function of wind speed and relative wind direction. Ground speeds of the tracked birds in the along-wind direction varied primarily by wind-induced leeway, which averaged 0.51 (± 0.02) times the wind speed at a reference height of 5 m. By subtracting leeway velocity from ground velocity, we were able to estimate airspeed (the magnitude of the bird's velocity through the air). As wind speeds increased from 3 to 18 m/s, the airspeed of wandering albatrosses flying in an across-wind direction increased by 0.42 (± 0.04) times the wind speed (i.e. ~ 6 m/s). At low wind speeds, tracked birds increased their airspeed in upwind flight relative to that in downwind flight. At higher wind speeds they apparently limited their airspeeds to a maximum of around 20 m/s, probably to keep the forces on their wings in dynamic soaring well within tolerable limits. Upwind airspeeds were nearly constant and downwind leeway increased with wind speed. Birds therefore achieved their fastest upwind ground speeds (~ 9 m/s) at low wind speeds (~ 3 m/s). This study provides insights into which flight strategies are optimal for dynamic soaring. Our results are consistent with the prediction that the optimal range speed of albatrosses is higher

  8. Calculation of wind speeds required to damage or destroy buildings

    NASA Astrophysics Data System (ADS)

    Liu, Henry

    Determination of wind speeds required to damage or destroy a building is important not only for the improvement of building design and construction but also for the estimation of wind speeds in tornadoes and other damaging storms. For instance, since 1973 the U.S. National Weather Service has been using the well-known Fujita scale (F scale) to estimate the maximum wind speeds of tornadoes [Fujita, 1981]. The F scale classifies tornadoes into 13 numbers, F-0 through F-12. The wind speed (maximum gust speed) associated with each F number is given in Table 1. Note that F-6 through F-12 are for wind speeds between 319 mi/hr (mph) and the sonic velocity (approximately 760 mph; 1 mph = 1.6 km/kr). However, since no tornadoes have been classified to exceed F-5, the F-6 through F-12 categories have no practical meaning [Fujita, 1981].

  9. Jupiter cloud morphology and zonal winds from ground-based observations before and during Juno exploration

    NASA Astrophysics Data System (ADS)

    Sanchez-Lavega, A.; Hueso, R.; Perez-Hoyos, S.; Iñurrigarro, P.; Mendikoa, I.; Rojas, J. F.

    2016-12-01

    We present the results of a long term campaign between September 2015 and August 2016 of imaging of Jupiter's cloud morphology and zonal winds in the 0.38 - 1.7 μm wavelength spectral range. We use PlanetCam lucky imaging camera at the 2.2m telescope at Calar Alto Observatory in Spain, and for the optical range, the contribution of a network of observers to the Planetary Virtual Observatory Laboratory database (PVOL-IOPW at http://pvol.ehu.eus). We have complemented the study with Hubble Space Telescope WFC3 camera images taken in the 0.275 - 0.89 μm wavelength spectral range during the OPAL program on 9 February 2016. The PlanetCam images have been calibrated in radiance using spectrophotometric standard stars providing absolute reflectivity across the disk in a large series of broadband and narrowband filters sensitive to the altitude distribution and size of aerosols above the ammonia cloud level, and to the spectral dependence of the chromophore coloring agents. The cloud morphology evolution has been studied with an horizontal resolution ranging from 150 to 1000 km. Zonal wind profiles have been retrieved along the whole observing period from tracking cloud motions that span the latitude range from -80° to +77º. Combining all these results we characterized the 3D-dynamical state and cloud and haze distribution in Jupiter's atmosphere in the altitude range between 10 mbar and 1.5 bar before and during Juno initial exploration.

  10. A short-term ensemble wind speed forecasting system for wind power applications

    NASA Astrophysics Data System (ADS)

    Baidya Roy, S.; Traiteur, J. J.; Callicutt, D.; Smith, M.

    2011-12-01

    This study develops an adaptive, blended forecasting system to provide accurate wind speed forecasts 1 hour ahead of time for wind power applications. The system consists of an ensemble of 21 forecasts with different configurations of the Weather Research and Forecasting Single Column Model (WRFSCM) and a persistence model. The ensemble is calibrated against observations for a 2 month period (June-July, 2008) at a potential wind farm site in Illinois using the Bayesian Model Averaging (BMA) technique. The forecasting system is evaluated against observations for August 2008 at the same site. The calibrated ensemble forecasts significantly outperform the forecasts from the uncalibrated ensemble while significantly reducing forecast uncertainty under all environmental stability conditions. The system also generates significantly better forecasts than persistence, autoregressive (AR) and autoregressive moving average (ARMA) models during the morning transition and the diurnal convective regimes. This forecasting system is computationally more efficient than traditional numerical weather prediction models and can generate a calibrated forecast, including model runs and calibration, in approximately 1 minute. Currently, hour-ahead wind speed forecasts are almost exclusively produced using statistical models. However, numerical models have several distinct advantages over statistical models including the potential to provide turbulence forecasts. Hence, there is an urgent need to explore the role of numerical models in short-term wind speed forecasting. This work is a step in that direction and is likely to trigger a debate within the wind speed forecasting community.

  11. Wind Speed and Sea State Dependencies of Air-Sea Gas Transfer: Results From the High Wind Speed Gas Exchange Study (HiWinGS)

    NASA Astrophysics Data System (ADS)

    Blomquist, B. W.; Brumer, S. E.; Fairall, C. W.; Huebert, B. J.; Zappa, C. J.; Brooks, I. M.; Yang, M.; Bariteau, L.; Prytherch, J.; Hare, J. E.; Czerski, H.; Matei, A.; Pascal, R. W.

    2017-10-01

    A variety of physical mechanisms are jointly responsible for facilitating air-sea gas transfer through turbulent processes at the atmosphere-ocean interface. The nature and relative importance of these mechanisms evolves with increasing wind speed. Theoretical and modeling approaches are advancing, but the limited quantity of observational data at high wind speeds hinders the assessment of these efforts. The HiWinGS project successfully measured gas transfer coefficients (k660) with coincident wave statistics under conditions with hourly mean wind speeds up to 24 m s-1 and significant wave heights to 8 m. Measurements of k660 for carbon dioxide (CO2) and dimethylsulfide (DMS) show an increasing trend with respect to 10 m neutral wind speed (U10N), following a power law relationship of the form: k660 CO2˜U10N1.68 and k660 dms˜U10N1.33. Among seven high wind speed events, CO2 transfer responded to the intensity of wave breaking, which depended on both wind speed and sea state in a complex manner, with k660 CO2 increasing as the wind sea approaches full development. A similar response is not observed for DMS. These results confirm the importance of breaking waves and bubble injection mechanisms in facilitating CO2 transfer. A modified version of the Coupled Ocean-Atmosphere Response Experiment Gas transfer algorithm (COAREG ver. 3.5), incorporating a sea state-dependent calculation of bubble-mediated transfer, successfully reproduces the mean trend in observed k660 with wind speed for both gases. Significant suppression of gas transfer by large waves was not observed during HiWinGS, in contrast to results from two prior field programs.

  12. A new method for wind speed forecasting based on copula theory.

    PubMed

    Wang, Yuankun; Ma, Huiqun; Wang, Dong; Wang, Guizuo; Wu, Jichun; Bian, Jinyu; Liu, Jiufu

    2018-01-01

    How to determine representative wind speed is crucial in wind resource assessment. Accurate wind resource assessments are important to wind farms development. Linear regressions are usually used to obtain the representative wind speed. However, terrain flexibility of wind farm and long distance between wind speed sites often lead to low correlation. In this study, copula method is used to determine the representative year's wind speed in wind farm by interpreting the interaction of the local wind farm and the meteorological station. The result shows that the method proposed here can not only determine the relationship between the local anemometric tower and nearby meteorological station through Kendall's tau, but also determine the joint distribution without assuming the variables to be independent. Moreover, the representative wind data can be obtained by the conditional distribution much more reasonably. We hope this study could provide scientific reference for accurate wind resource assessments. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Indian Ocean zonal mode activity in 20th century observations and simulations

    NASA Astrophysics Data System (ADS)

    Sendelbeck, Anja; Mölg, Thomas

    2016-04-01

    The Indian Ocean zonal mode (IOZM) is a coupled ocean-atmosphere system with anomalous cooling in the east, warming in the west and easterly wind anomalies, resulting in a complete reversal of the climatological zonal sea surface temperature (SST) gradient. The IOZM has a strong influence on East African climate by causing anomalously strong October - December (OND) precipitation. Using observational data and historical CMIP5 (Coupled Model Intercomparison Project phase 5) model output, the September - November (SON) dipole mode index (DMI), OND East African precipitation and SON zonal wind index (ZWI) are calculated. We pay particular attention to detrending SSTs for calculating the DMI, which seems to have been neglected in some published research. The ZWI is defined as the area-averaged zonal wind component at 850 hPa over the central Indian Ocean. Regression analysis is used to evaluate the models' capability to represent the IOZM and its impact on east African climate between 1948 and 2005. Simple correlations are calculated between SST, zonal wind and precipitation to show their interdependence. High correlation in models implies a good representation of the influence of IOZM on East African climate variability and our goal is to detect the models with the highest correlation coefficients. In future research, these model data might be used to investigate the impact of IOZM on the East African climate variability in the late 20's century with regard to anthropogenic causes and internal variability.

  14. Gas transfer velocities measured at low wind speed over a lake

    USGS Publications Warehouse

    Crusius, John; Wanninkhof, R.

    2003-01-01

    The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1-min-averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10-m height, U10: (1) a bilinear dependence with a break in the slope at ???3.7 m s-1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 3.7 m s-1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ???3.7 m s-1 are virtually identical to the theoretical predictions for transfer across a smooth surface.

  15. Gas exchange-wind speed relation measured with sulfur hexafluoride on a lake

    NASA Technical Reports Server (NTRS)

    Wanninkhof, R.; Broecker, W. S.; Ledwell, J. R.

    1985-01-01

    Gas-exchange processes control the uptake and release of various gases in natural systems such as oceans, rivers, and lakes. Not much is known about the effect of wind speed on gas exchange in such systems. In the experiment described here, sulfur hexafluoride was dissolved in lake water, and the rate of escape of the gas with wind speed (at wind speeds up to 6 meters per second) was determined over a 1-month period. A sharp change in the wind speed dependence of the gas-exchange coefficient was found at wind speeds of about 2.4 meters per second, in agreement with the results of wind-tunnel studies. However the gas-exchange coefficients at wind speeds above 3 meters per second were smaller than those observed in wind tunnels and are in agreement with earlier lake and ocean results.

  16. MEASUREMENT OF WIND SPEED FROM COOLING LAKE THERMAL IMAGERY

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Garrett, A; Robert Kurzeja, R; Eliel Villa-Aleman, E

    2009-01-20

    The Savannah River National Laboratory (SRNL) collected thermal imagery and ground truth data at two commercial power plant cooling lakes to investigate the applicability of laboratory empirical correlations between surface heat flux and wind speed, and statistics derived from thermal imagery. SRNL demonstrated in a previous paper [1] that a linear relationship exists between the standard deviation of image temperature and surface heat flux. In this paper, SRNL will show that the skewness of the temperature distribution derived from cooling lake thermal images correlates with instantaneous wind speed measured at the same location. SRNL collected thermal imagery, surface meteorology andmore » water temperatures from helicopters and boats at the Comanche Peak and H. B. Robinson nuclear power plant cooling lakes. SRNL found that decreasing skewness correlated with increasing wind speed, as was the case for the laboratory experiments. Simple linear and orthogonal regression models both explained about 50% of the variance in the skewness - wind speed plots. A nonlinear (logistic) regression model produced a better fit to the data, apparently because the thermal convection and resulting skewness are related to wind speed in a highly nonlinear way in nearly calm and in windy conditions.« less

  17. A novel application of artificial neural network for wind speed estimation

    NASA Astrophysics Data System (ADS)

    Fang, Da; Wang, Jianzhou

    2017-05-01

    Providing accurate multi-steps wind speed estimation models has increasing significance, because of the important technical and economic impacts of wind speed on power grid security and environment benefits. In this study, the combined strategies for wind speed forecasting are proposed based on an intelligent data processing system using artificial neural network (ANN). Generalized regression neural network and Elman neural network are employed to form two hybrid models. The approach employs one of ANN to model the samples achieving data denoising and assimilation and apply the other to predict wind speed using the pre-processed samples. The proposed method is demonstrated in terms of the predicting improvements of the hybrid models compared with single ANN and the typical forecasting method. To give sufficient cases for the study, four observation sites with monthly average wind speed of four given years in Western China were used to test the models. Multiple evaluation methods demonstrated that the proposed method provides a promising alternative technique in monthly average wind speed estimation.

  18. The GalileoJupiter Probe Doppler Wind Experiment

    NASA Astrophysics Data System (ADS)

    Atkinson, D. H.

    2001-09-01

    The GalileoJupiter atmospheric entry probe was launched along with the Galileoorbiter spacecraft from Cape Canaveral in Florida, USA, on October 18, 1989. Following a cruise of greater than six years, the probe arrived at Jupiter on December 7, 1995. During its 57-minute descent, instruments on the probe studied the atmospheric composition and structure, the clouds, lightning, and energy structure of the upper Jovian atmosphere. One of the two radio channels over which the experiment data was transmitted to the orbiter was driven by an ultrastable oscillator. All motions of the probe and orbiter, including the speed of probe descent, Jupiter's rotation, and the atmospheric winds, contributed to a Doppler shift of the probe radio frequency. By accurately measuring the frequency of the probe radio signal, an accurate time history of the probe-orbiter relative motions could be reconstructed. Knowledge of the nominal probe and orbiter trajectories allowed the nominal Doppler shift to be removed from the probe radio frequency leaving a measurable frequency residual arising primarily from the zonal winds in Jupiter's atmosphere, and micromotions of the probe arising from probe spin, swing under the parachute, atmospheric turbulence, and aerodynamic effects. Assuming that the zonal horizontal winds dominate the residual probe motion, a profile of frequency residuals was generated. Inversion of the frequency residuals resulted in the first in situ measurements of the vertical profile of Jupiter's deep zonal winds. It is found that beneath 700 mb, the winds are strong and prograde, rising rapidly to 170 m/s between 1 and 4 bars. Beneath 4 bars to 21 bars, the depth at which the link with the probe was lost, the winds remain constant and strong. When corrections for the high temperatures encountered by the probe are considered, there is no evidence of diminishing or strengthening of the zonal winds in the deepest regions explored by the Galileoprobe. Following the wind

  19. Idealized models of the joint probability distribution of wind speeds

    NASA Astrophysics Data System (ADS)

    Monahan, Adam H.

    2018-05-01

    The joint probability distribution of wind speeds at two separate locations in space or points in time completely characterizes the statistical dependence of these two quantities, providing more information than linear measures such as correlation. In this study, we consider two models of the joint distribution of wind speeds obtained from idealized models of the dependence structure of the horizontal wind velocity components. The bivariate Rice distribution follows from assuming that the wind components have Gaussian and isotropic fluctuations. The bivariate Weibull distribution arises from power law transformations of wind speeds corresponding to vector components with Gaussian, isotropic, mean-zero variability. Maximum likelihood estimates of these distributions are compared using wind speed data from the mid-troposphere, from different altitudes at the Cabauw tower in the Netherlands, and from scatterometer observations over the sea surface. While the bivariate Rice distribution is more flexible and can represent a broader class of dependence structures, the bivariate Weibull distribution is mathematically simpler and may be more convenient in many applications. The complexity of the mathematical expressions obtained for the joint distributions suggests that the development of explicit functional forms for multivariate speed distributions from distributions of the components will not be practical for more complicated dependence structure or more than two speed variables.

  20. The vertical structure of Jupiter and Saturn zonal winds from nonlinear simulations of major vortices and planetary-scale disturbances

    NASA Astrophysics Data System (ADS)

    Garcia-Melendo, E.; Legarreta, J.; Sanchez-Lavega, A.

    2012-12-01

    Direct measurements of the structure of the zonal winds of Jupiter and Saturn below the upper cloud layer are very difficult to retrieve. Except from the vertical profile at a Jupiter hot spot obtained from the Galileo probe in 1995 and measurements from cloud tracking by Cassini instruments just below the upper cloud, no other data are available. We present here our inferences of the vertical structure of Jupiter and Saturn zonal wind across the upper troposphere (deep down to about 10 bar level) obtained from nonlinear simulations using the EPIC code of the stability and interactions of large-scale vortices and planetary-scale disturbances in both planets. Acknowledgements: This work has been funded by Spanish MICIIN AYA2009-10701 with FEDER support, Grupos Gobierno Vasco IT-464-07 and UPV/EHU UFI11/55. [1] García-Melendo E., Sánchez-Lavega A., Dowling T.., Icarus, 176, 272-282 (2005). [2] García-Melendo E., Sánchez-Lavega A., Hueso R., Icarus, 191, 665-677 (2007). [3] Sánchez-Lavega A., et al., Nature, 451, 437- 440 (2008). [4] Sánchez-Lavega A., et al., Nature, 475, 71-74 (2011).

  1. Dynamical relationship between wind speed magnitude and meridional temperature contrast: Application to an interannual oscillation in Venusian middle atmosphere GCM

    NASA Astrophysics Data System (ADS)

    Yamamoto, Masaru; Takahashi, Masaaki

    2018-03-01

    We derive simple dynamical relationships between wind speed magnitude and meridional temperature contrast. The relationship explains scatter plot distributions of time series of three variables (maximum zonal wind speed UMAX, meridional wind speed VMAX, and equator-pole temperature contrast dTMAX), which are obtained from a Venus general circulation model with equatorial Kelvin-wave forcing. Along with VMAX and dTMAX, UMAX likely increases with the phase velocity and amplitude of a forced wave. In the scatter diagram of UMAX versus dTMAX, points are plotted along a linear equation obtained from a thermal-wind relationship in the cloud layer. In the scatter diagram of VMAX versus UMAX, the apparent slope is somewhat steep in the high UMAX regime, compared with the low UMAX regime. The scatter plot distributions are qualitatively consistent with a quadratic equation obtained from a diagnostic equation of the stream function above the cloud top. The plotted points in the scatter diagrams form a linear cluster for weak wave forcing, whereas they form a small cluster for strong wave forcing. An interannual oscillation of the general circulation forming the linear cluster in the scatter diagram is apparent in the experiment of weak 5.5-day wave forcing. Although a pair of equatorial Kelvin and high-latitude Rossby waves with a same period (Kelvin-Rossby wave) produces equatorward heat and momentum fluxes in the region below 60 km, the equatorial wave does not contribute to the long-period oscillation. The interannual fluctuation of the high-latitude jet core leading to the time variation of UMAX is produced by growth and decay of a polar mixed Rossby-gravity wave with a 14-day period.

  2. Observing Equatorial Thermospheric Winds and Temperatures with a New Mapping Technique

    NASA Astrophysics Data System (ADS)

    Faivre, M. W.; Meriwether, J. W.; Sherwood, P.; Veliz, O.

    2005-12-01

    Application of the Fabry-Perot interferometer (FPI) at Arequipa, Peru (16.4S, 71.4 W) to measure the Doppler shifts and Doppler broadenings in the equatorial O(1D) 630-nm nightglow has resulted in numerous detections of a large-scale thermospheric phenomenon called the Midnight Temperature Maximum (MTM). A recent detector upgrade with a CCD camera has improved the accuracy of these measurements by a factor of 5. Temperature increases of 50 to 150K have been measured during nights in April and July, 2005, with error bars less than 10K after averaging in all directions. Moreover, the meridional wind measurements show evidence for a flow reversal from equatorward to poleward near local midnight for such events. A new observing strategy based upon the pioneering work of Burnside et al.[1981] maps the equatorial wind and temperature fields by observing in eight equally-spaced azimuth directions, each with a zenith angle of 60 degrees. Analysis of the data obtained with this technique gives the mean wind velocities in the meridional and zonal directions as well as the horizontal gradients of the wind field for these directions. Significant horizontal wind gradients are found for the meridional direction but not for the zonal direction. The zonal wind blows eastward throughout the night with a maximum speed of ~150 m/s near the middle of the night and then decreases towards zero just before dawn. In general, the fastest poleward meridional wind is observed near mid-evening. By the end of the night, the meridional flow tends to be more equatorward at speeds of about 50 m/s. Using the assumption that local time and longitude are equivalent over a period of 30 minutes, a map of the horizontal wind field vector field is constructed over a range of 12 degrees latitude centered at 16.5 S. Comparison between MTM nights and quiet nights (no MTM) revealed significant differences in the horizontal wind fields. Using the method of Fourier decomposition of the line-of-sight winds

  3. A hybrid wavelet transform based short-term wind speed forecasting approach.

    PubMed

    Wang, Jujie

    2014-01-01

    It is important to improve the accuracy of wind speed forecasting for wind parks management and wind power utilization. In this paper, a novel hybrid approach known as WTT-TNN is proposed for wind speed forecasting. In the first step of the approach, a wavelet transform technique (WTT) is used to decompose wind speed into an approximate scale and several detailed scales. In the second step, a two-hidden-layer neural network (TNN) is used to predict both approximated scale and detailed scales, respectively. In order to find the optimal network architecture, the partial autocorrelation function is adopted to determine the number of neurons in the input layer, and an experimental simulation is made to determine the number of neurons within each hidden layer in the modeling process of TNN. Afterwards, the final prediction value can be obtained by the sum of these prediction results. In this study, a WTT is employed to extract these different patterns of the wind speed and make it easier for forecasting. To evaluate the performance of the proposed approach, it is applied to forecast Hexi Corridor of China's wind speed. Simulation results in four different cases show that the proposed method increases wind speed forecasting accuracy.

  4. A Hybrid Wavelet Transform Based Short-Term Wind Speed Forecasting Approach

    PubMed Central

    Wang, Jujie

    2014-01-01

    It is important to improve the accuracy of wind speed forecasting for wind parks management and wind power utilization. In this paper, a novel hybrid approach known as WTT-TNN is proposed for wind speed forecasting. In the first step of the approach, a wavelet transform technique (WTT) is used to decompose wind speed into an approximate scale and several detailed scales. In the second step, a two-hidden-layer neural network (TNN) is used to predict both approximated scale and detailed scales, respectively. In order to find the optimal network architecture, the partial autocorrelation function is adopted to determine the number of neurons in the input layer, and an experimental simulation is made to determine the number of neurons within each hidden layer in the modeling process of TNN. Afterwards, the final prediction value can be obtained by the sum of these prediction results. In this study, a WTT is employed to extract these different patterns of the wind speed and make it easier for forecasting. To evaluate the performance of the proposed approach, it is applied to forecast Hexi Corridor of China's wind speed. Simulation results in four different cases show that the proposed method increases wind speed forecasting accuracy. PMID:25136699

  5. Wind speed time series reconstruction using a hybrid neural genetic approach

    NASA Astrophysics Data System (ADS)

    Rodriguez, H.; Flores, J. J.; Puig, V.; Morales, L.; Guerra, A.; Calderon, F.

    2017-11-01

    Currently, electric energy is used in practically all modern human activities. Most of the energy produced came from fossil fuels, making irreversible damage to the environment. Lately, there has been an effort by nations to produce energy using clean methods, such as solar and wind energy, among others. Wind energy is one of the cleanest alternatives. However, the wind speed is not constant, making the planning and operation at electric power systems a difficult activity. Knowing in advance the amount of raw material (wind speed) used for energy production allows us to estimate the energy to be generated by the power plant, helping the maintenance planning, the operational management, optimal operational cost. For these reasons, the forecast of wind speed becomes a necessary task. The forecast process involves the use of past observations from the variable to forecast (wind speed). To measure wind speed, weather stations use devices called anemometers, but due to poor maintenance, connection error, or natural wear, they may present false or missing data. In this work, a hybrid methodology is proposed, and it uses a compact genetic algorithm with an artificial neural network to reconstruct wind speed time series. The proposed methodology reconstructs the time series using a ANN defined by a Compact Genetic Algorithm.

  6. SeaWinds Radar Clocks Hurricane Dora Wind Speeds

    NASA Image and Video Library

    1999-08-25

    The SeaWinds instrument onboard NASA new QuikScat ocean-viewing satellite captured this image of Hurricane Dora in the eastern tropical Pacific Ocean on August 10, as it was blowing at speeds of nearly 40 meters per second 90 miles per hour.

  7. Sensitivity of Gravity Wave Fluxes to Interannual Variations in Tropical Convection and Zonal Wind.

    PubMed

    Alexander, M Joan; Ortland, David A; Grimsdell, Alison W; Kim, Ji-Eun

    2017-09-01

    Using an idealized model framework with high-frequency tropical latent heating variability derived from global satellite observations of precipitation and clouds, the authors examine the properties and effects of gravity waves in the lower stratosphere, contrasting conditions in an El Niño year and a La Niña year. The model generates a broad spectrum of tropical waves including planetary-scale waves through mesoscale gravity waves. The authors compare modeled monthly mean regional variations in wind and temperature with reanalyses and validate the modeled gravity waves using satellite- and balloon-based estimates of gravity wave momentum flux. Some interesting changes in the gravity spectrum of momentum flux are found in the model, which are discussed in terms of the interannual variations in clouds, precipitation, and large-scale winds. While regional variations in clouds, precipitation, and winds are dramatic, the mean gravity wave zonal momentum fluxes entering the stratosphere differ by only 11%. The modeled intermittency in gravity wave momentum flux is shown to be very realistic compared to observations, and the largest-amplitude waves are related to significant gravity wave drag forces in the lowermost stratosphere. This strong intermittency is generally absent or weak in climate models because of deficiencies in parameterizations of gravity wave intermittency. These results suggest a way forward to improve model representations of the lowermost stratospheric quasi-biennial oscillation winds and teleconnections.

  8. A reward semi-Markov process with memory for wind speed modeling

    NASA Astrophysics Data System (ADS)

    Petroni, F.; D'Amico, G.; Prattico, F.

    2012-04-01

    The increasing interest in renewable energy leads scientific research to find a better way to recover most of the available energy. Particularly, the maximum energy recoverable from wind is equal to 59.3% of that available (Betz law) at a specific pitch angle and when the ratio between the wind speed in output and in input is equal to 1/3. The pitch angle is the angle formed between the airfoil of the blade of the wind turbine and the wind direction. Old turbine and a lot of that actually marketed, in fact, have always the same invariant geometry of the airfoil. This causes that wind turbines will work with an efficiency that is lower than 59.3%. New generation wind turbines, instead, have a system to variate the pitch angle by rotating the blades. This system able the wind turbines to recover, at different wind speed, always the maximum energy, working in Betz limit at different speed ratios. A powerful system control of the pitch angle allows the wind turbine to recover better the energy in transient regime. A good stochastic model for wind speed is then needed to help both the optimization of turbine design and to assist the system control to predict the value of the wind speed to positioning the blades quickly and correctly. The possibility to have synthetic data of wind speed is a powerful instrument to assist designer to verify the structures of the wind turbines or to estimate the energy recoverable from a specific site. To generate synthetic data, Markov chains of first or higher order are often used [1,2,3]. In particular in [1] is presented a comparison between a first-order Markov chain and a second-order Markov chain. A similar work, but only for the first-order Markov chain, is conduced by [2], presenting the probability transition matrix and comparing the energy spectral density and autocorrelation of real and synthetic wind speed data. A tentative to modeling and to join speed and direction of wind is presented in [3], by using two models, first

  9. Flying with the wind: scale dependency of speed and direction measurements in modelling wind support in avian flight.

    PubMed

    Safi, Kamran; Kranstauber, Bart; Weinzierl, Rolf; Griffin, Larry; Rees, Eileen C; Cabot, David; Cruz, Sebastian; Proaño, Carolina; Takekawa, John Y; Newman, Scott H; Waldenström, Jonas; Bengtsson, Daniel; Kays, Roland; Wikelski, Martin; Bohrer, Gil

    2013-01-01

    Understanding how environmental conditions, especially wind, influence birds' flight speeds is a prerequisite for understanding many important aspects of bird flight, including optimal migration strategies, navigation, and compensation for wind drift. Recent developments in tracking technology and the increased availability of data on large-scale weather patterns have made it possible to use path annotation to link the location of animals to environmental conditions such as wind speed and direction. However, there are various measures available for describing not only wind conditions but also the bird's flight direction and ground speed, and it is unclear which is best for determining the amount of wind support (the length of the wind vector in a bird's flight direction) and the influence of cross-winds (the length of the wind vector perpendicular to a bird's direction) throughout a bird's journey. We compared relationships between cross-wind, wind support and bird movements, using path annotation derived from two different global weather reanalysis datasets and three different measures of direction and speed calculation for 288 individuals of nine bird species. Wind was a strong predictor of bird ground speed, explaining 10-66% of the variance, depending on species. Models using data from different weather sources gave qualitatively similar results; however, determining flight direction and speed from successive locations, even at short (15 min intervals), was inferior to using instantaneous GPS-based measures of speed and direction. Use of successive location data significantly underestimated the birds' ground and airspeed, and also resulted in mistaken associations between cross-winds, wind support, and their interactive effects, in relation to the birds' onward flight. Wind has strong effects on bird flight, and combining GPS technology with path annotation of weather variables allows us to quantify these effects for understanding flight behaviour. The

  10. Nonparametric Stochastic Model for Uncertainty Quantifi cation of Short-term Wind Speed Forecasts

    NASA Astrophysics Data System (ADS)

    AL-Shehhi, A. M.; Chaouch, M.; Ouarda, T.

    2014-12-01

    Wind energy is increasing in importance as a renewable energy source due to its potential role in reducing carbon emissions. It is a safe, clean, and inexhaustible source of energy. The amount of wind energy generated by wind turbines is closely related to the wind speed. Wind speed forecasting plays a vital role in the wind energy sector in terms of wind turbine optimal operation, wind energy dispatch and scheduling, efficient energy harvesting etc. It is also considered during planning, design, and assessment of any proposed wind project. Therefore, accurate prediction of wind speed carries a particular importance and plays significant roles in the wind industry. Many methods have been proposed in the literature for short-term wind speed forecasting. These methods are usually based on modeling historical fixed time intervals of the wind speed data and using it for future prediction. The methods mainly include statistical models such as ARMA, ARIMA model, physical models for instance numerical weather prediction and artificial Intelligence techniques for example support vector machine and neural networks. In this paper, we are interested in estimating hourly wind speed measures in United Arab Emirates (UAE). More precisely, we predict hourly wind speed using a nonparametric kernel estimation of the regression and volatility functions pertaining to nonlinear autoregressive model with ARCH model, which includes unknown nonlinear regression function and volatility function already discussed in the literature. The unknown nonlinear regression function describe the dependence between the value of the wind speed at time t and its historical data at time t -1, t - 2, … , t - d. This function plays a key role to predict hourly wind speed process. The volatility function, i.e., the conditional variance given the past, measures the risk associated to this prediction. Since the regression and the volatility functions are supposed to be unknown, they are estimated using

  11. Self-organization of large-scale ULF electromagnetic wave structures in their interaction with nonuniform zonal winds in the ionospheric E region

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Aburjania, G. D.; Chargazia, Kh. Z.

    A study is made of the generation and subsequent linear and nonlinear evolution of ultralow-frequency planetary electromagnetic waves in the E region of a dissipative ionosphere in the presence of a nonuniform zonal wind (a sheared flow). Hall currents flowing in the E region and such permanent global factors as the spatial nonuniformity of the geomagnetic field and of the normal component of the Earth's angular velocity give rise to fast and slow planetary-scale electromagnetic waves. The efficiency of the linear amplification of planetary electromagnetic waves in their interaction with a nonuniform zonal wind is analyzed. When there are shearedmore » flows, the operators of linear problems are non-self-conjugate and the corresponding eigenfunctions are nonorthogonal, so the canonical modal approach is poorly suited for studying such motions and it is necessary to utilize the so-called nonmodal mathematical analysis. It is shown that, in the linear evolutionary stage, planetary electromagnetic waves efficiently extract energy from the sheared flow, thereby substantially increasing their amplitude and, accordingly, energy. The criterion for instability of a sheared flow in an ionospheric medium is derived. As the shear instability develops and the perturbation amplitude grows, a nonlinear self-localization mechanism comes into play and the process ends with the self-organization of nonlinear, highly localized, solitary vortex structures. The system thus acquires a new degree of freedom, thereby providing a new way for the perturbation to evolve in a medium with a sheared flow. Depending on the shape of the sheared flow velocity profile, nonlinear structures can be either purely monopole vortices or vortex streets against the background of the zonal wind. The accumulation of such vortices can lead to a strongly turbulent state in an ionospheric medium.« less

  12. On the vertical wind shear of Saturn's Equatorial Jet at cloud level

    NASA Astrophysics Data System (ADS)

    Sánchez-Lavega, A.; Pérez-Hoyos, S.

    2005-08-01

    With the aim of retrieving the altitude of cloud features used as zonal wind tracers in Saturn's atmosphere, we have reanalyzed three different sets of photometric and calibrated data corresponding to the Voyager epoch 1979-1981 (ground-based in 1979, Voyager 2 PPS and ISS observations in 1981), and we have analyze a new set of Hubble Space Telescope images for 2004. This analysis is put in the perspective of our previous HST study for 1994-2003 (Pérez-Hoyos et al., Icarus, 176, 155. 2005). A common result is found that the individual cloud tracers are embedded within a variable tropospheric haze. According to our models, the Voyager 2 ISS images locate the cloud tracers moving with zonal velocities of 455 to 465 (± 2) m/s at a pressure level of 360 ± 140 mbar. For HST observations, the cloud tracers moving with zonal wind speeds of 280 ± 10 m/s, locate at a pressure level of about 50 ± 10 mbar. All these values are calculated in the latitude 3 deg North. The speed difference, if interpreted as a vertical wind shear (Porco et al., Science, 307, 1226. 2005), requires a change of 90 m/s per scale height, two times greater than that estimated from Cassini CIRS data (Flasar et al., Science, 307, 1247, 2005). We also perform an initial guess on Cassini ISS vertical sounding levels, retrieving values compatible with the HST ones but not with Voyager wind measurements. We conclude that the wind speed velocity differences measured between 1979-81 and 2004 in the upper troposphere cannot be solely explained as a wind shear effect and demand dynamical processes. We discuss the possible action of Rossby waves or an intrinsic circulation change in the ammonia cloud layer and above, following a large period of equatorial storm activity. Acknowledgments: This work was supported by MCYT AYA2003-03216, FEDER, and Grupos UPV 15946/2004. S.P.-H. acknowledges a PhD fellowship from the Spanish MEC and R. H. a post-doc contract from Gobierno Vasco.

  13. Longitudinal differences and inter-annual variations of zonal wind in the tropical stratosphere and troposphere

    NASA Astrophysics Data System (ADS)

    Reddy, C. A.; Raghava Reddi, C.

    1986-12-01

    A quantitative assessment has been made of the longitude-dependent differences and the interannual variations of the zonal wind components in the equatorial stratosphere and troposphere, from the analysis of rocket and balloon data for 1979 and 1980 for three stations near ±8.5° latitude (Ascension Island at 14.4°W, Thumba at 76.9°E and Kwajalein at 67.7°E) and two stations near 21.5° latitude (Barking Sands at 159.6°W and Balasore at 86.9°E). The longitude-dependent differences are found to be about 10-20 m s -1 (amounting to 50-200% in some cases) for the semi-annual oscillation (SAO) and the annual oscillation (AO) amplitudes, depending upon the altitude and latitude. Inter-annual variations of about 10 m s -1 also exist in both oscillations. The phase of the SAO exhibits an almost 180° shift at Kwajalein compared to that at the other two stations near 8.5°, while the phase of the AO is independent of longitude, in the stratosphere. The amplitude and phase of the quasi-biennial oscillation (QBO) are found to be almost independent of longitude in the 18-38 km range, but above 40 km height the QBO amplitude and phase have different values in different longitude sectors for the three stations near ±8.5° latitude. The mean zonal wind shows no change from 1979 to 1980, but in the troposphere at 8.5° latitude strong easterlies prevail in the Indian zone, in contrast to the westerlies at the Atlantic and Pacific stations.

  14. First and second order semi-Markov chains for wind speed modeling

    NASA Astrophysics Data System (ADS)

    Prattico, F.; Petroni, F.; D'Amico, G.

    2012-04-01

    The increasing interest in renewable energy leads scientific research to find a better way to recover most of the available energy. Particularly, the maximum energy recoverable from wind is equal to 59.3% of that available (Betz law) at a specific pitch angle and when the ratio between the wind speed in output and in input is equal to 1/3. The pitch angle is the angle formed between the airfoil of the blade of the wind turbine and the wind direction. Old turbine and a lot of that actually marketed, in fact, have always the same invariant geometry of the airfoil. This causes that wind turbines will work with an efficiency that is lower than 59.3%. New generation wind turbines, instead, have a system to variate the pitch angle by rotating the blades. This system able the wind turbines to recover, at different wind speed, always the maximum energy, working in Betz limit at different speed ratios. A powerful system control of the pitch angle allows the wind turbine to recover better the energy in transient regime. A good stochastic model for wind speed is then needed to help both the optimization of turbine design and to assist the system control to predict the value of the wind speed to positioning the blades quickly and correctly. The possibility to have synthetic data of wind speed is a powerful instrument to assist designer to verify the structures of the wind turbines or to estimate the energy recoverable from a specific site. To generate synthetic data, Markov chains of first or higher order are often used [1,2,3]. In particular in [3] is presented a comparison between a first-order Markov chain and a second-order Markov chain. A similar work, but only for the first-order Markov chain, is conduced by [2], presenting the probability transition matrix and comparing the energy spectral density and autocorrelation of real and synthetic wind speed data. A tentative to modeling and to join speed and direction of wind is presented in [1], by using two models, first

  15. Wind speed affects prey-catching behaviour in an orb web spider.

    PubMed

    Turner, Joe; Vollrath, Fritz; Hesselberg, Thomas

    2011-12-01

    Wind has previously been shown to influence the location and orientation of spider web sites and also the geometry and material composition of constructed orb webs. We now show that wind also influences components of prey-catching behaviour within the web. A small wind tunnel was used to generate different wind speeds. Araneus diadematus ran more slowly towards entangled Drosophila melanogaster in windy conditions, which took less time to escape the web. This indicates a lower capture probability and a diminished overall predation efficiency for spiders at higher wind speeds. We conclude that spiders' behaviour of taking down their webs as wind speed increases may therefore not be a response only to possible web damage.

  16. Wind speed affects prey-catching behaviour in an orb web spider

    NASA Astrophysics Data System (ADS)

    Turner, Joe; Vollrath, Fritz; Hesselberg, Thomas

    2011-12-01

    Wind has previously been shown to influence the location and orientation of spider web sites and also the geometry and material composition of constructed orb webs. We now show that wind also influences components of prey-catching behaviour within the web. A small wind tunnel was used to generate different wind speeds. Araneus diadematus ran more slowly towards entangled Drosophila melanogaster in windy conditions, which took less time to escape the web. This indicates a lower capture probability and a diminished overall predation efficiency for spiders at higher wind speeds. We conclude that spiders' behaviour of taking down their webs as wind speed increases may therefore not be a response only to possible web damage.

  17. Statistical Compression of Wind Speed Data

    NASA Astrophysics Data System (ADS)

    Tagle, F.; Castruccio, S.; Crippa, P.; Genton, M.

    2017-12-01

    In this work we introduce a lossy compression approach that utilizes a stochastic wind generator based on a non-Gaussian distribution to reproduce the internal climate variability of daily wind speed as represented by the CESM Large Ensemble over Saudi Arabia. Stochastic wind generators, and stochastic weather generators more generally, are statistical models that aim to match certain statistical properties of the data on which they are trained. They have been used extensively in applications ranging from agricultural models to climate impact studies. In this novel context, the parameters of the fitted model can be interpreted as encoding the information contained in the original uncompressed data. The statistical model is fit to only 3 of the 30 ensemble members and it adequately captures the variability of the ensemble in terms of seasonal internannual variability of daily wind speed. To deal with such a large spatial domain, it is partitioned into 9 region, and the model is fit independently to each of these. We further discuss a recent refinement of the model, which relaxes this assumption of regional independence, by introducing a large-scale component that interacts with the fine-scale regional effects.

  18. Flying with the wind: Scale dependency of speed and direction measurements in modelling wind support in avian flight

    USGS Publications Warehouse

    Safi, Kamran; Kranstauber, Bart; Weinzierl, Rolf P.; Griffin, Larry; Reese, Eileen C.; Cabot, David; Cruz, Sebastian; Proaño, Carolina; Takekawa, John Y.; Newman, Scott H.; Waldenström, Jonas; Bengtsson, Daniel; Kays, Roland; Wikelski, Martin; Bohrer, Gil

    2013-01-01

    Background: Understanding how environmental conditions, especially wind, influence birds' flight speeds is a prerequisite for understanding many important aspects of bird flight, including optimal migration strategies, navigation, and compensation for wind drift. Recent developments in tracking technology and the increased availability of data on large-scale weather patterns have made it possible to use path annotation to link the location of animals to environmental conditions such as wind speed and direction. However, there are various measures available for describing not only wind conditions but also the bird's flight direction and ground speed, and it is unclear which is best for determining the amount of wind support (the length of the wind vector in a bird’s flight direction) and the influence of cross-winds (the length of the wind vector perpendicular to a bird’s direction) throughout a bird's journey.Results: We compared relationships between cross-wind, wind support and bird movements, using path annotation derived from two different global weather reanalysis datasets and three different measures of direction and speed calculation for 288 individuals of nine bird species. Wind was a strong predictor of bird ground speed, explaining 10-66% of the variance, depending on species. Models using data from different weather sources gave qualitatively similar results; however, determining flight direction and speed from successive locations, even at short (15 min intervals), was inferior to using instantaneous GPS-based measures of speed and direction. Use of successive location data significantly underestimated the birds' ground and airspeed, and also resulted in mistaken associations between cross-winds, wind support, and their interactive effects, in relation to the birds' onward flight.Conclusions: Wind has strong effects on bird flight, and combining GPS technology with path annotation of weather variables allows us to quantify these effects for

  19. Effective wind speed estimation: Comparison between Kalman Filter and Takagi-Sugeno observer techniques.

    PubMed

    Gauterin, Eckhard; Kammerer, Philipp; Kühn, Martin; Schulte, Horst

    2016-05-01

    Advanced model-based control of wind turbines requires knowledge of the states and the wind speed. This paper benchmarks a nonlinear Takagi-Sugeno observer for wind speed estimation with enhanced Kalman Filter techniques: The performance and robustness towards model-structure uncertainties of the Takagi-Sugeno observer, a Linear, Extended and Unscented Kalman Filter are assessed. Hence the Takagi-Sugeno observer and enhanced Kalman Filter techniques are compared based on reduced-order models of a reference wind turbine with different modelling details. The objective is the systematic comparison with different design assumptions and requirements and the numerical evaluation of the reconstruction quality of the wind speed. Exemplified by a feedforward loop employing the reconstructed wind speed, the benefit of wind speed estimation within wind turbine control is illustrated. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

  20. [Effects of wind speed on drying processes of fuelbeds composed of Mongolian oak broad-leaves.

    PubMed

    Zhang, Li Bin; Sun, Ping; Jin, Sen

    2016-11-18

    Water desorption processes of fuel beds with Mongolian oak broad-leaves were observed under conditions with various wind speeds but nearly constant air temperature and humidity. The effects of wind speed on drying coefficients of fuel beds with various moisture contents were analyzed. Three phases of drying process, namely high initial moisture content (>75%) of phase 1, transition state of phase 2, and equilibrium phase III could be identified. During phase 1, water loss rate under higher wind speed was higher than that under lower wind speed. Water loss rate under higher wind speed was lower than that under lower wind speed during phase 2. During phase 3, water loss rates under different wind speeds were similar. The wind effects decreased with the decrease of fuel moisture. The drying coefficient of the Mongolian oak broad-leaves fuel beds was affected by wind speed and fuel bed compactness, and the interaction between these two factors. The coefficient increased with wind speed roughly in a monotonic cubic polynomial form.

  1. Winds in the Middle Cloud Deck From the Near-IR Imaging by the Venus Monitoring Camera Onboard Venus Express

    NASA Astrophysics Data System (ADS)

    Khatuntsev, I. V.; Patsaeva, M. V.; Titov, D. V.; Ignatiev, N. I.; Turin, A. V.; Fedorova, A. A.; Markiewicz, W. J.

    2017-11-01

    For more than 8 years the Venus Monitoring Camera (VMC) onboard the Venus Express orbiter performed continuous imaging of the Venus cloud layer in UV, visible and near-IR filters. We applied the correlation approach to sequences of the near-IR images at 965 nm to track cloud features and determine the wind field in the middle and lower cloud (49-57 km). From the VMC images that spanned from December of 2006 through August of 2013 we derived zonal and meridional components of the wind field. In low-to-middle latitudes (5-65°S) the velocity of the retrograde zonal wind was found to be 68-70 m/s. The meridional wind velocity slowly decreases from peak value of +5.8 ± 1.2 m/s at 15°S to 0 at 65-70°S. The mean meridional speed has a positive sign at 5-65°S suggesting equatorward flow. This result, together with the earlier measurements of the poleward flow at the cloud tops, indicates the presence of a closed Hadley cell in the altitude range 55-65 km. Long-term variations of zonal and meridional velocity components were found during 1,200 Earth days of observation. At 20° ± 5°S the zonal wind speed increases from -67.18 ± 1.81 m/s to -77.30 ± 2.49 m/s. The meridional wind gradually increases from +1.30 ± 1.82 m/s to +8.53 ± 2.14 m/s. Following Bertaux et al. (2016) we attribute this long-term trend to the influence from the surface topography on the dynamical process in the atmosphere via the upward propagation of gravity waves that became apparent in the VMC observations due to slow drift of the Venus Express orbit over Aphrodite Terra.

  2. Evaluating anemometer drift: A statistical approach to correct biases in wind speed measurement

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, Cesar; Asin, Jesus; McVicar, Tim R.; Minola, Lorenzo; Lopez-Moreno, Juan I.; Vicente-Serrano, Sergio M.; Chen, Deliang

    2018-05-01

    Recent studies on observed wind variability have revealed a decline (termed "stilling") of near-surface wind speed during the last 30-50 years over many mid-latitude terrestrial regions, particularly in the Northern Hemisphere. The well-known impact of cup anemometer drift (i.e., wear on the bearings) on the observed weakening of wind speed has been mentioned as a potential contributor to the declining trend. However, to date, no research has quantified its contribution to stilling based on measurements, which is most likely due to lack of quantification of the ageing effect. In this study, a 3-year field experiment (2014-2016) with 10-minute paired wind speed measurements from one new and one malfunctioned (i.e., old bearings) SEAC SV5 cup anemometer which has been used by the Spanish Meteorological Agency in automatic weather stations since mid-1980s, was developed for assessing for the first time the role of anemometer drift on wind speed measurement. The results showed a statistical significant impact of anemometer drift on wind speed measurements, with the old anemometer measuring lower wind speeds than the new one. Biases show a marked temporal pattern and clear dependency on wind speed, with both weak and strong winds causing significant biases. This pioneering quantification of biases has allowed us to define two regression models that correct up to 37% of the artificial bias in wind speed due to measurement with an old anemometer.

  3. Substorm-related thermospheric density and wind disturbances

    NASA Astrophysics Data System (ADS)

    Ritter, P.; Luhr, H.; Doornbos, E. N.

    2009-12-01

    The input of energy and momentum from the magnetosphere is most efficiently coupled into the high latitude ionosphere-thermosphere. The phenomenon we are focusing on here is the magnetospheric substorm. This paper presents substorm related observations of the thermosphere derived from the CHAMP satellite. With its sensitive accelerometer the satellite can measure the air density and zonal winds. Based on a large number of substorm events the average high and low latitude thermosphere response to substorm onsets was deduced. During magnetic substorms the thermospheric density is enhanced first at high latitudes. Then the disturbance travels at sonic speed to lower latitudes, and 3-4 hours later the bulge reaches the equator on the night side. Under the influence of the Coriolis force the traveling atmospheric disturbance (TAD) is deflected westward. In accordance with present-day atmospheric models the disturbance zonal wind velocities during substorms are close to zero near the equator before midnight and attain moderate westward velocities after midnight. In general, the wind system is only weakly perturbed by substorms.

  4. Observed surface wind speed declining induced by urbanization in East China

    NASA Astrophysics Data System (ADS)

    Li, Zhengquan; Song, Lili; Ma, Hao; Xiao, Jingjing; Wang, Kuo; Chen, Lian

    2018-02-01

    Monthly wind data from 506 meteorological stations and ERA-Interim reanalysis during 1991-2015, are used to examine the surface wind trend over East China. Furthermore, combining the urbanization information derived from the DMSP/OLS nighttime light data during 1992-2013, the effects of urbanization on surface wind change are investigated by applying the observation minus reanalysis (OMR) method. The results show that the observed surface wind speed over East China is distinctly weakening with a rate of -0.16 m s-1 deca-1 during 1991-2015, while ERA-Interim wind speed does not have significant decreasing or increasing trend in the same period. The observed surface wind declining is mainly attributed to underlying surface changes of stations observational areas that were mostly induced by the urbanization in East China. Moreover, the wind declining intensity is closely related to the urbanization rhythms. The OMR annual surface wind speeds of Rhythm-VS, Rhythm-S, Rhythm-M, Rhythm-F and Rhythm-VF, have decreasing trends with the rates of -0.02 to -0.09, -0.16 to -0.26, -0.22 to -0.30, -0.26 to -0.36 and -0.33 to -0.51 m s-1 deca-1, respectively. The faster urbanization rhythm is, the stronger wind speed weakening presents. Additionally urban expansion is another factor resulted in the observed surface wind declining.

  5. Relationship between eastern tropical Pacific cooling and recent trends in the Southern Hemisphere zonal-mean circulation

    NASA Astrophysics Data System (ADS)

    Clem, Kyle R.; Renwick, James A.; McGregor, James

    2017-07-01

    During 1979-2014, eastern tropical Pacific sea surface temperatures significantly cooled, which has generally been attributed to the transition of the Pacific Decadal Oscillation to its negative phase after 1999. We find the eastern tropical Pacific cooling to be associated with: (1) an intensified Walker Circulation during austral summer (December-February, DJF) and autumn (March-May, MAM); (2) a weakened South Pacific Hadley cell and subtropical jet during MAM; and (3) a strengthening of the circumpolar westerlies between 50 and 60°S during DJF and MAM. Observed cooling in the eastern tropical Pacific is linearly congruent with 60-80 % of the observed Southern Hemisphere positive zonal-mean zonal wind trend between 50 and 60°S during DJF ( 35 % of the interannual variability), and around half of the observed positive zonal-mean zonal wind trend during MAM ( 15 % of the interannual variability). Although previous studies have linked the strengthened DJF and MAM circumpolar westerlies to stratospheric ozone depletion and increasing greenhouse gases, we note that the continuation of the positive SAM trends into the twenty-first century is partially associated with eastern tropical Pacific cooling, especially during MAM when zonal wind anomalies associated with eastern tropical Pacific cooling project strongly onto the observed trends. Outside of DJF and MAM, eastern tropical Pacific cooling is associated with opposing zonal wind anomalies over the Pacific and Indian sectors, which we infer is the reason for the absence of significant positive SAM trends outside of DJF and MAM despite significant eastern tropical Pacific cooling seen during all seasons.

  6. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 5 2011-07-01 2011-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test...

  7. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 5 2010-07-01 2010-07-01 false Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test...

  8. A Model Study of Zonal Forcing in the Equatorial Stratosphere by Convectively Induced Gravity Waves

    NASA Technical Reports Server (NTRS)

    Alexander, M. J.; Holton, James R.

    1997-01-01

    A two-dimensional cloud-resolving model is used to examine the possible role of gravity waves generated by a simulated tropical squall line in forcing the quasi-biennial oscillation (QBO) of the zonal winds in the equatorial stratosphere. A simulation with constant background stratospheric winds is compared to simulations with background winds characteristic of the westerly and easterly QBO phases, respectively. In all three cases a broad spectrum of both eastward and westward propagating gravity waves is excited. In the constant background wind case the vertical momentum flux is nearly constant with height in the stratosphere, after correction for waves leaving the model domain. In the easterly and westerly shear cases, however, westward and eastward propagating waves, respectively, are strongly damped as they approach their critical levels, owing to the strongly scale-dependent vertical diffusion in the model. The profiles of zonal forcing induced by this wave damping are similar to profiles given by critical level absorption, but displaced slightly downward. The magnitude of the zonal forcing is of order 5 m/s/day. It is estimated that if 2% of the area of the Tropics were occupied by storms of similar magnitude, mesoscale gravity waves could provide nearly 1/4 of the zonal forcing required for the QBO.

  9. Self-Powered Wind Sensor System for Detecting Wind Speed and Direction Based on a Triboelectric Nanogenerator.

    PubMed

    Wang, Jiyu; Ding, Wenbo; Pan, Lun; Wu, Changsheng; Yu, Hua; Yang, Lijun; Liao, Ruijin; Wang, Zhong Lin

    2018-04-24

    The development of the Internet of Things has brought new challenges to the corresponding distributed sensor systems. Self-powered sensors that can perceive and respond to environmental stimuli without an external power supply are highly desirable. In this paper, a self-powered wind sensor system based on an anemometer triboelectric nanogenerator (a-TENG, free-standing mode) and a wind vane triboelectric nanogenerator (v-TENG, single-electrode mode) is proposed for simultaneously detecting wind speed and direction. A soft friction mode is adopted instead of a typical rigid friction for largely enhancing the output performance of the TENG. The design parameters including size, unit central angle, and applied materials are optimized to enhance sensitivity, resolution, and wide measurement scale. The optimized a-TENG could deliver an open-circuit voltage of 88 V and short-circuit current of 6.3 μA, corresponding to a maximum power output of 0.47 mW (wind speed of 6.0 m/s), which is capable of driving electronics for data transmission and storage. The current peak value of the a-TENG signal is used for analyzing wind speed for less energy consumption. Moreover, the output characteristics of a v-TENG are further explored, with six actual operation situations, and the v-TENG delivers fast response to the incoming wind and accurately outputs the wind direction data. As a wind sensor system, wind speed ranging from 2.7 to 8.0 m/s can be well detected (consistent with a commercial sensor) and eight regular directions can be monitored. Therefore, the fabricated wind sensor system has great potential in wireless environmental monitoring applications.

  10. Multiple and variable speed electrical generator systems for large wind turbines

    NASA Technical Reports Server (NTRS)

    Andersen, T. S.; Hughes, P. S.; Kirschbaum, H. S.; Mutone, G. A.

    1982-01-01

    A cost effective method to achieve increased wind turbine generator energy conversion and other operational benefits through variable speed operation is presented. Earlier studies of multiple and variable speed generators in wind turbines were extended for evaluation in the context of a specific large sized conceptual design. System design and simulation have defined the costs and performance benefits which can be expected from both two speed and variable speed configurations.

  11. Reduced wind speed improves plant growth in a desert city.

    PubMed

    Bang, Christofer; Sabo, John L; Faeth, Stanley H

    2010-06-10

    The often dramatic effects of urbanization on community and ecosystem properties, such as primary productivity, abundances, and diversity are now well-established. In most cities local primary productivity increases and this extra energy flows upwards to alter diversity and relative abundances in higher trophic levels. The abiotic mechanisms thought to be responsible for increases in urban productivity are altered temperatures and light regimes, and increased nutrient and water inputs. However, another abiotic factor, wind speed, is also influenced by urbanization and well known for altering primary productivity in agricultural systems. Wind effects on primary productivity have heretofore not been studied in the context of urbanization. We designed a field experiment to test if increased plant growth often observed in cities is explained by the sheltering effects of built structures. Wind speed was reduced by protecting Encelia farinosa (brittlebush) plants in urban, desert remnant and outlying desert localities via windbreaks while controlling for water availability and nutrient content. In all three habitats, we compared E. farinosa growth when protected by experimental windbreaks and in the open. E. farinosa plants protected against ambient wind in the desert and remnant areas grew faster in terms of biomass and height than exposed plants. As predicted, sheltered plants did not differ from unprotected plants in urban areas where wind speed is already reduced. Our results indicate that reductions in wind speed due to built structures in cities contribute to increased plant productivity and thus also to changes in abundances and diversity of higher trophic levels. Our study emphasizes the need to incorporate wind speed in future urban ecological studies, as well as in planning for green space and sustainable cities.

  12. Variability of Wind Speeds and Power over Europe

    NASA Astrophysics Data System (ADS)

    Tambke, J.; von Bremen, L.; de Decker, J.; Schmidt, M.; Steinfeld, G.; Wolff, J.-O.

    2010-09-01

    This study comprises two parts: First, we describe the vertical wind speed and turbulence profiles that result from our improved PBL scheme and compare it to observations and 1-dimensional approaches (Monin-Obukhov etc.). Second, we analyse the spatio-temporal correlations in our meso-scale simulations for the years 2004 to 2007 over entire Europe, with special focus on the Irish, North and Baltic Sea. 1.) Vertical Wind Speed Profiles The vertical wind profile above the sea has to be modelled with high accuracy for tip heights up to 160m in order to achieve precise wind resource assessments, to calculate loads and wakes of wind turbines as well as for reliable short-term wind power forecasts. We present an assessment of different models for wind profiles in unstable, neutral and stable thermal stratification. The meso-scale models comprise MM5, WRF and COSMO-EU (LME). Both COSMO-EU from the German Weather Service DWD and WRF use a turbulence closure of 2.5th order - and lead to similar results. Especially the limiting effect of low boundary layer heights on the wind shear in very stable stratification is well captured. In our new WRF-formulation for the mixing length in the Mellor-Yamada-Janjic (MYJ) parameterisation of the Planetary Boundary Layer (PBL-scheme), the master length scale itself depends on the Monin-Obukhov-Length as a parameter for the heat flux effects on the turbulent mixing. This new PBL-scheme shows a better performance for all weather conditions than the original MYJ-scheme. Apart from the low-boundary-layer-effect in very stable situations (which are seldom), standard Monin-Obukhov formulations in combination with the Charnock relation for the sea surface roughness show good agreement with the FINO1-data (German Bight). Interesting results were achieved with two more detailed micro-scale approaches: - the parameterization proposed by Pena, Gryning and Hasager [BLM 2008] that depends on the boundary layer height - our ICWP-model, were the flux

  13. 11. INTERIOR VIEW OF 8FOOT HIGH SPEED WIND TUNNEL. SAME ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. INTERIOR VIEW OF 8-FOOT HIGH SPEED WIND TUNNEL. SAME CAMERA POSITION AS VA-118-B-10 LOOKING IN THE OPPOSITE DIRECTION. - NASA Langley Research Center, 8-Foot High Speed Wind Tunnel, 641 Thornell Avenue, Hampton, Hampton, VA

  14. Influence of Wind Speed on RGB-D Images in Tree Plantations

    PubMed Central

    Andújar, Dionisio; Dorado, José; Bengochea-Guevara, José María; Conesa-Muñoz, Jesús; Fernández-Quintanilla, César; Ribeiro, Ángela

    2017-01-01

    Weather conditions can affect sensors’ readings when sampling outdoors. Although sensors are usually set up covering a wide range of conditions, their operational range must be established. In recent years, depth cameras have been shown as a promising tool for plant phenotyping and other related uses. However, the use of these devices is still challenged by prevailing field conditions. Although the influence of lighting conditions on the performance of these cameras has already been established, the effect of wind is still unknown. This study establishes the associated errors when modeling some tree characteristics at different wind speeds. A system using a Kinect v2 sensor and a custom software was tested from null wind speed up to 10 m·s−1. Two tree species with contrasting architecture, poplars and plums, were used as model plants. The results showed different responses depending on tree species and wind speed. Estimations of Leaf Area (LA) and tree volume were generally more consistent at high wind speeds in plum trees. Poplars were particularly affected by wind speeds higher than 5 m·s−1. On the contrary, height measurements were more consistent for poplars than for plum trees. These results show that the use of depth cameras for tree characterization must take into consideration wind conditions in the field. In general, 5 m·s−1 (18 km·h−1) could be established as a conservative limit for good estimations. PMID:28430119

  15. Performance study of personal inhalable aerosol samplers at ultra-low wind speeds.

    PubMed

    Sleeth, Darrah K; Vincent, James H

    2012-03-01

    The assessment of personal inhalable aerosol samplers in a controlled laboratory setting has not previously been carried out at the ultra-low wind speed conditions that represent most modern workplaces. There is currently some concern about whether the existing inhalable aerosol convention is appropriate at these low wind speeds and an alternative has been suggested. It was therefore important to assess the performance of the most common personal samplers used to collect the inhalable aerosol fraction, especially those that were designed to match the original curve. The experimental set-up involved use of a hybrid ultra-low speed wind tunnel/calm air chamber and a rotating, heating breathing mannequin to measure the inhalable fraction of aerosol exposure. The samplers that were tested included the Institute of Occupational Medicine (IOM), Button, and GSP inhalable samplers as well as the closed-face cassette sampler that has been (and still is) widely used by occupational hygienists in many countries. The results showed that, down to ∼0.2 m s(-1), the samplers matched the current inhalability criterion relatively well but were significantly greater than this at the lowest wind speed tested. Overall, there was a significant effect of wind speed on sampling efficiency, with lower wind speeds clearly associated with an increase in sampling efficiency.

  16. Higher-than-predicted saltation threshold wind speeds on Titan.

    PubMed

    Burr, Devon M; Bridges, Nathan T; Marshall, John R; Smith, James K; White, Bruce R; Emery, Joshua P

    2015-01-01

    Titan, the largest satellite of Saturn, exhibits extensive aeolian, that is, wind-formed, dunes, features previously identified exclusively on Earth, Mars and Venus. Wind tunnel data collected under ambient and planetary-analogue conditions inform our models of aeolian processes on the terrestrial planets. However, the accuracy of these widely used formulations in predicting the threshold wind speeds required to move sand by saltation, or by short bounces, has not been tested under conditions relevant for non-terrestrial planets. Here we derive saltation threshold wind speeds under the thick-atmosphere, low-gravity and low-sediment-density conditions on Titan, using a high-pressure wind tunnel refurbished to simulate the appropriate kinematic viscosity for the near-surface atmosphere of Titan. The experimentally derived saltation threshold wind speeds are higher than those predicted by models based on terrestrial-analogue experiments, indicating the limitations of these models for such extreme conditions. The models can be reconciled with the experimental results by inclusion of the extremely low ratio of particle density to fluid density on Titan. Whereas the density ratio term enables accurate modelling of aeolian entrainment in thick atmospheres, such as those inferred for some extrasolar planets, our results also indicate that for environments with high density ratios, such as in jets on icy satellites or in tenuous atmospheres or exospheres, the correction for low-density-ratio conditions is not required.

  17. Bernoulli-Langevin Wind Speed Model for Simulation of Storm Events

    NASA Astrophysics Data System (ADS)

    Fürstenau, Norbert; Mittendorf, Monika

    2016-12-01

    We present a simple nonlinear dynamics Langevin model for predicting the instationary wind speed profile during storm events typically accompanying extreme low-pressure situations. It is based on a second-degree Bernoulli equation with δ-correlated Gaussian noise and may complement stationary stochastic wind models. Transition between increasing and decreasing wind speed and (quasi) stationary normal wind and storm states are induced by the sign change of the controlling time-dependent rate parameter k(t). This approach corresponds to the simplified nonlinear laser dynamics for the incoherent to coherent transition of light emission that can be understood by a phase transition analogy within equilibrium thermodynamics [H. Haken, Synergetics, 3rd ed., Springer, Berlin, Heidelberg, New York 1983/2004.]. Evidence for the nonlinear dynamics two-state approach is generated by fitting of two historical wind speed profiles (low-pressure situations "Xaver" and "Christian", 2013) taken from Meteorological Terminal Air Report weather data, with a logistic approximation (i.e. constant rate coefficients k) to the solution of our dynamical model using a sum of sigmoid functions. The analytical solution of our dynamical two-state Bernoulli equation as obtained with a sinusoidal rate ansatz k(t) of period T (=storm duration) exhibits reasonable agreement with the logistic fit to the empirical data. Noise parameter estimates of speed fluctuations are derived from empirical fit residuals and by means of a stationary solution of the corresponding Fokker-Planck equation. Numerical simulations with the Bernoulli-Langevin equation demonstrate the potential for stochastic wind speed profile modeling and predictive filtering under extreme storm events that is suggested for applications in anticipative air traffic management.

  18. Does the scatterometer see wind speed or friction velocity?

    NASA Technical Reports Server (NTRS)

    Donelan, M. A.; Pierson, W. J., Jr.

    1984-01-01

    Studies of radar backscatter from the sea surface are referred either to the wind speed, U, or friction velocity, u(sub *). Bragg scattering theory suggests that these variations in backscatter are directly related to the height of the capillary-gravity waves modulated by the larger waves in tilt and by straining of the short wave field. The question then arises as to what characteristic of the wind field is most probably correlated with the wave number spectrum of the capillary-gravity waves. The justification for selecting U as the appropriate meteorological parameter to be associated with backscatter from L-band to Ku-band are reviewed. Both theoretical reasons and experimental evidence are used to demonstrate that the dominant parameter is U/C(lambda) where U is the wind speed at a height of about lambda/2 for waves having a phase speed of C(lambda).

  19. Performance Investigation of A Mix Wind Turbine Using A Clutch Mechanism At Low Wind Speed Condition

    NASA Astrophysics Data System (ADS)

    Jamanun, M. J.; Misaran, M. S.; Rahman, M.; Muzammil, W. K.

    2017-07-01

    Wind energy is one of the methods that generates energy from sustainable resources. This technology has gained prominence in this era because it produces no harmful product to the society. There is two fundamental type of wind turbine are generally used this day which is Horizontal axis wind turbine (HAWT) and Vertical axis wind turbine (VAWT). The VAWT technology is more preferable compare to HAWT because it gives better efficiency and cost effectiveness as a whole. However, VAWT is known to have distinct disadvantage compared to HAWT; self-start ability and efficiency at low wind speed condition. Different solution has been proposed to solve these issues which includes custom design blades, variable angle of attack mechanism and mix wind turbine. A new type of clutch device was successfully developed in UMS to be used in a mix Savonius-Darrieus wind turbine configuration. The clutch system which barely audible when in operation compared to a ratchet clutch system interconnects the Savonius and Darrieus rotor; allowing the turbine to self-start at low wind speed condition as opposed to a standalone Darrieus turbine. The Savonius height were varied at three different size in order to understand the effect of the Savonius rotor to the mix wind turbine performance. The experimental result shows that the fabricated Savonius rotor show that the height of the Savonius rotor affecting the RPM for the turbine. The swept area (SA), aspect ratio (AR) and tip speed ratio (TSR) also calculated in this paper. The highest RPM recorded in this study is 90 RPM for Savonius rotor 0.22-meter height at 2.75 m/s. The Savonius rotor 0.22-meter also give the highest TSR for each range of speed from 0.75 m/s, 1.75 m/s and 2.75 m/s where it gives 1.03 TSR, 0.76 TSR, and 0.55 TSR.

  20. Direct Torque Control of a Small Wind Turbine with a Sliding-Mode Speed Controller

    NASA Astrophysics Data System (ADS)

    Sri Lal Senanayaka, Jagath; Karimi, Hamid Reza; Robbersmyr, Kjell G.

    2016-09-01

    In this paper. the method of direct torque control in the presence of a sliding-mode speed controller is proposed for a small wind turbine being used in water heating applications. This concept and control system design can be expanded to grid connected or off-grid applications. Direct torque control of electrical machines has shown several advantages including very fast dynamics torque control over field-oriented control. Moreover. the torque and flux controllers in the direct torque control algorithms are based on hvsteretic controllers which are nonlinear. In the presence of a sliding-mode speed control. a nonlinear control system can be constructed which is matched for AC/DC conversion of the converter that gives fast responses with low overshoots. The main control objectives of the proposed small wind turbine can be maximum power point tracking and soft-stall power control. This small wind turbine consists of permanent magnet synchronous generator and external wind speed. and rotor speed measurements are not required for the system. However. a sensor is needed to detect the rated wind speed overpass events to activate proper speed references for the wind turbine. Based on the low-cost design requirement of small wind turbines. an available wind speed sensor can be modified. or a new sensor can be designed to get the required measurement. The simulation results will be provided to illustrate the excellent performance of the closed-loop control system in entire wind speed range (4-25 m/s).

  1. Solar wind structure suggested by bimodal correlations of solar wind speed and density between the spacecraft SOHO and Wind

    NASA Astrophysics Data System (ADS)

    Ogilvie, K. W.; Coplan, M. A.; Roberts, D. A.; Ipavich, F.

    2007-08-01

    We calculate the cross-spacecraft maximum lagged-cross-correlation coefficients for 2-hour intervals of solar wind speed and density measurements made by the plasma instruments on the Solar and Heliospheric Observatory (SOHO) and Wind spacecraft over the period from 1996, the minimum of solar cycle 23, through the end of 2005. During this period, SOHO was located at L1, about 200 R E upstream from the Earth, while Wind spent most of the time in the interplanetary medium at distances of more than 100 R E from the Earth. Yearly histograms of the maximum, time-lagged correlation coefficients for both the speed and density are bimodal in shape, suggesting the existence of two distinct solar wind regimes. The larger correlation coefficients we suggest are due to structured solar wind, including discontinuities and shocks, while the smaller are likely due to Alfvénic turbulence. While further work will be required to firmly establish the physical nature of the two populations, the results of the analysis are consistent with a solar wind that consists of turbulence from quiet regions of the Sun interspersed with highly filamentary structures largely convected from regions in the inner solar corona. The bimodal appearance of the distributions is less evident in the solar wind speed than in the density correlations, consistent with the observation that the filamentary structures are convected with nearly constant speed by the time they reach 1 AU. We also find that at solar minimum the fits for the density correlations have smaller high-correlation components than at solar maximum. We interpret this as due to the presence of more relatively uniform Alfvénic regions at solar minimum than at solar maximum.

  2. Temporal and radial variation of the solar wind temperature-speed relationship

    NASA Astrophysics Data System (ADS)

    Elliott, H. A.; Henney, C. J.; McComas, D. J.; Smith, C. W.; Vasquez, B. J.

    2012-09-01

    The solar wind temperature (T) and speed (V) are generally well correlated at ˜1 AU, except in Interplanetary Coronal Mass Ejections where this correlation breaks down. We perform a comprehensive analysis of both the temporal and radial variation in the temperature-speed (T-V) relationship of the non-transient wind, and our analysis provides insight into both the causes of the T-V relationship and the sources of the temperature variability. Often at 1 AU the speed-temperature relationship is well represented by a single linear fit over a speed range spanning both the slow and fast wind. However, at times the fast wind from coronal holes can have a different T-V relationship than the slow wind. A good example of this was in 2003 when there was a very large and long-lived outward magnetic polarity coronal hole at low latitudes that emitted wind with speeds as fast as a polar coronal hole. The long-lived nature of the hole made it possible to clearly distinguish that some holes can have a different T-V relationship. In an earlier ACE study, we found that both the compressions and rarefactions T-V curves are linear, but the compression curve is shifted to higher temperatures. By separating compressions and rarefactions prior to determining the radial profiles of the solar wind parameters, the importance of dynamic interactions on the radial evolution of the solar wind parameters is revealed. Although the T-V relationship at 1 AU is often well described by a single linear curve, we find that the T-V relationship continually evolves with distance. Beyond ˜2.5 AU the differences between the compressions and rarefactions are quite significant and affect the shape of the overall T-V distribution to the point that a simple linear fit no longer describes the distribution well. Since additional heating of the ambient solar wind outside of interaction regions can be associated with Alfvénic fluctuations and the turbulent energy cascade, we also estimate the heating rate

  3. An examination of loads and responses of a wind turbine undergoing variable-speed operation

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wright, A.D.; Buhl, M.L. Jr.; Bir, G.S.

    1996-11-01

    The National Renewable Energy Laboratory has recently developed the ability to predict turbine loads and responses for machines undergoing variable-speed operation. The wind industry has debated the potential benefits of operating wind turbine sat variable speeds for some time. Turbine system dynamic responses (structural response, resonance, and component interactions) are an important consideration for variable-speed operation of wind turbines. The authors have implemented simple, variable-speed control algorithms for both the FAST and ADAMS dynamics codes. The control algorithm is a simple one, allowing the turbine to track the optimum power coefficient (C{sub p}). The objective of this paper is tomore » show turbine loads and responses for a particular two-bladed, teetering-hub, downwind turbine undergoing variable-speed operation. The authors examined the response of the machine to various turbulent wind inflow conditions. In addition, they compare the structural responses under fixed-speed and variable-speed operation. For this paper, they restrict their comparisons to those wind-speed ranges for which limiting power by some additional control strategy (blade pitch or aileron control, for example) is not necessary. The objective here is to develop a basic understanding of the differences in loads and responses between the fixed-speed and variable-speed operation of this wind turbine configuration.« less

  4. Solar wind speed and He I (1083 nm) absorption line intensity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hakamada, Kazuyuki; Kojima, Masayoshi; Kakinuma, Takakiyo

    1991-04-01

    Since the pattern of the solar wind was relatively steady during Carrington rotations 1,748 through 1,752 in 1984, an average distribution of the solar windspeed on a so-called source surface can be constructed by superposed epoch analysis of the wind values estimated by the interplanetary scintillation observations. The average distribution of the solar wind speed is then projected onto the photosphere along magnetic field lines computed by a so-called potential model with the line-of-sight components of the photospheric magnetic fields. The solar wind speeds projected onto the photosphere are compared with the intensities of the He I (1,083 nm) absorptionmore » line at the corresponding locations in the chromosphere. The authors found that there is a linear relation between the speeds and the intensities. Since the intensity of the He I (1,083 nm) absorption line is coupled with the temperature of the corona, this relation suggests that some physical mechanism in or above the photosphere accelerates coronal plasmas to the solar wind speed in regions where the temperature is low. Further, it is suggested that the efficiency of the solar wind acceleration decreases as the coronal temperature increases.« less

  5. Aerodynamic performance of a low-speed wind tunnel.

    PubMed

    Frechen, F-B; Frey, M; Wett, M; Löser, C

    2004-01-01

    The determination of the odour mass flow emitted from a source is a very important step and forms the basis for all subsequent considerations and calculations. Wastewater treatment plants, as well as waste treatment facilities, consist of different kinds of odour sources. Unfortunately, most of the sources are passive sources, where no outward air flow-rate can be measured, but where odorants are obviously emitted. Thus, a type of sampling is required that allows to measure the emitted odour flow-rate (OFR). To achieve this, different methods are in use worldwide. Besides indirect methods, such as micrometeorological atmospheric dispersion models, which have not been used in Germany (in other countries due to different problems, direct methods are also used). Direct measurements include hood methods, commonly divided into static flux chambers, dynamic flux chambers and wind tunnels. The wind tunnel that we have been operating in principle since 1983 is different from all subsequent presented wind tunnels, in that we operate it at a considerably lower wind speed than the others. To describe the behaviour of this wind tunnel, measurement of the flow pattern in this low-speed tunnel are under way, and some initial results are presented here.

  6. Hurricane Imaging Radiometer (HIRAD) Wind Speed Retrievals and Assessment Using Dropsondes

    NASA Technical Reports Server (NTRS)

    Cecil, Daniel J.; Biswas, Sayak K.

    2018-01-01

    The Hurricane Imaging Radiometer (HIRAD) is an experimental C-band passive microwave radiometer designed to map the horizontal structure of surface wind speed fields in hurricanes. New data processing and customized retrieval approaches were developed after the 2015 Tropical Cyclone Intensity (TCI) experiment, which featured flights over Hurricanes Patricia, Joaquin, Marty, and the remnants of Tropical Storm Erika. These new approaches produced maps of surface wind speed that looked more realistic than those from previous campaigns. Dropsondes from the High Definition Sounding System (HDSS) that was flown with HIRAD on a WB-57 high altitude aircraft in TCI were used to assess the quality of the HIRAD wind speed retrievals. The root mean square difference between HIRAD-retrieved surface wind speeds and dropsonde-estimated surface wind speeds was 6.0 meters per second. The largest differences between HIRAD and dropsonde winds were from data points where storm motion during dropsonde descent compromised the validity of the comparisons. Accounting for this and for uncertainty in the dropsonde measurements themselves, we estimate the root mean square error for the HIRAD retrievals as around 4.7 meters per second. Prior to the 2015 TCI experiment, HIRAD had previously flown on the WB-57 for missions across Hurricanes Gonzalo (2014), Earl (2010), and Karl (2010). Configuration of the instrument was not identical to the 2015 flights, but the methods devised after the 2015 flights may be applied to that previous data in an attempt to improve retrievals from those cases.

  7. Monthly and annual percentage levels of wind speed differences computed by using FPS-16 radar/Jimsphere wind profile data from Cape Kennedy, Florida

    NASA Technical Reports Server (NTRS)

    Susko, M.; Kaufman, J. W.

    1973-01-01

    The percentage levels of wind speed differences are presented computed from sequential FPS-16 radar/Jimsphere wind profiles. The results are based on monthly profiles obtained from December 1964 to July 1970 at Cape Kennedy, Florida. The profile sequences contain a series of three to ten Jimspheres released at approximately 1.5-hour intervals. The results given are the persistence analysis of wind speed difference at 1.5-hour intervals to a maximum time interval of 12 hours. The monthly percentage of wind speed differences and the annual percentage of wind speed differences are tabulated. The percentage levels are based on the scalar wind speed changes calculated over an altitude interval of approximately 50 meters and printed out every 25 meters as a function of initial wind speed within each five-kilometer layer from near sea level to 20 km. In addition, analyses were made of the wind speed difference for the 0.2 to 1 km layer as an aid for studies associated with take-off and landing of the space shuttle.

  8. Effects of wind speed on aerosol spray penetration in adult mosquito bioassay cages.

    PubMed

    Hoffmann, W Clint; Fritz, Bradley K; Farooq, Muhammad; Cooperband, Miriam F

    2008-09-01

    Bioassay cages are commonly used to assess efficacy of insecticides against adult mosquitoes in the field. To correlate adult mortality readings to insecticidal efficacy and/or spray application parameters properly, it is important to know how the cage used in the bioassay interacts with the spray cloud containing the applied insecticide. This study compared the size of droplets, wind speed, and amount of spray material penetrating cages and outside of cages in a wind tunnel at different wind speeds. Two bioassay cages, Center for Medical, Agricultural and Veterinary Entomology (CMAVE) and Circle, were evaluated. The screen materials used on these cages reduced the size of droplets, wind speed, and amount of spray material inside the cages as compared to the spray cloud and wind velocity outside of the cages. When the wind speed in the dispersion tunnel was set at 0.6 m/sec (1.3 mph), the mean wind speed inside of the CMAVE Bioassay Cage and Circle Cage was 0.045 m/sec (0.10 mph) and 0.075 m/sec (0.17 mph), respectively. At air velocities of 2.2 m/sec (4.9 mph) in the dispersion tunnel, the mean wind speed inside of the CMAVE Bioassay Cage and Circle Cage was 0.83 m/sec (1.86 mph) and 0.71 m/sec (1.59 mph), respectively. Consequently, there was a consistent 50-70% reduction of spray material penetrating the cages compared to the spray cloud that approached the cages. These results provide a better understanding of the impact of wind speed, cage design, and construction on ultra-low-volume spray droplets.

  9. Two Capacitive Micro-Machined Ultrasonic Transducers for Wind Speed Measurement

    PubMed Central

    Bui, Gia Thinh; Jiang, Yu-Tsung; Pang, Da-Chen

    2016-01-01

    This paper presents a new wind speed measurement method using a single capacitive micro-machined ultrasonic transducer (CMUT). The CMUT was arranged perpendicular to the direction of the wind flow, and a reflector was set up a short distance away, facing the CMUT. To reduce the size, weight, cost, and power consumption of conventional ultrasonic anemometers this study proposes two CMUT designs for the measurement of wind speed using either the amplitude of the signal or the time of flight (TOF). Each CMUT with a double array element design can transmit and receive signals in five different operation modes. Experiments showed that the two CMUT designs utilizing the TOF were better than those utilizing the amplitude of the signal for wind speed measurements ranging from 1 m/s to 10 m/s, providing a measurement error of less than 0.2 m/s. These results indicate that the sensitivity of the TOF is independent of the five operation modes. PMID:27271625

  10. Two Capacitive Micro-Machined Ultrasonic Transducers for Wind Speed Measurement.

    PubMed

    Bui, Gia Thinh; Jiang, Yu-Tsung; Pang, Da-Chen

    2016-06-02

    This paper presents a new wind speed measurement method using a single capacitive micro-machined ultrasonic transducer (CMUT). The CMUT was arranged perpendicular to the direction of the wind flow, and a reflector was set up a short distance away, facing the CMUT. To reduce the size, weight, cost, and power consumption of conventional ultrasonic anemometers this study proposes two CMUT designs for the measurement of wind speed using either the amplitude of the signal or the time of flight (TOF). Each CMUT with a double array element design can transmit and receive signals in five different operation modes. Experiments showed that the two CMUT designs utilizing the TOF were better than those utilizing the amplitude of the signal for wind speed measurements ranging from 1 m/s to 10 m/s, providing a measurement error of less than 0.2 m/s. These results indicate that the sensitivity of the TOF is independent of the five operation modes.

  11. Mean wind speed persistence over China

    NASA Astrophysics Data System (ADS)

    Jiang, Lei

    2018-07-01

    The wind speed persistence is an important factor in the assessment of wind energy potential. In this paper, we explore the persistence of Mean Wind Speed (MWS) with many years of record using Detrended Fluctuation Analysis (DFA) over China. The results illustrate that there exist irregular high-frequency fluctuations for daily MWS anomaly records. Long-term persistence of MWS is found for all meteorological observed sites. We also make some numerical tests in order to verify the significance of long-term persistence by shuffling the data records many times. These facts prove that the MWS anomaly records have long-term persistence over all the stations in China. The mean value 0.64 in DFA-exponents for all stations over China is also obviously higher than the value 0.53 according to interval threshold of 95% confidence level after shuffling the MWS records many times. In addition, the values of scaling exponent vary from station to station over China. Long-term persistence of MWS in spatial distributions seems to be downward trends from east to west China. Many factors may affect long-term persistence of MWS such as southwest monsoon, Tibetan Plateau landform and atmosphere-ocean-land interaction and so on. Possible physical mechanism need further analysis in the future.

  12. Plant Gas Exchange at High Wind Speeds 1

    PubMed Central

    Caldwell, Martyn M.

    1970-01-01

    High altitude Rhododendron ferrugineum L. and Pinus cembra L. seedlings were exposed to winds at 15 meters per second for 24-hour periods. Wind-sensitive stomata of Rhododendron seedlings immediately initiated a closing response which resulted in decreased photosynthesis and an even greater reduction in transpiration. Stomatal aperture and transpiration rates of P. cembra were only slightly reduced by high speed winds. However, photosynthesis was substantially reduced because of changes in needle display to available irradiation. PMID:16657501

  13. UDE-based control of variable-speed wind turbine systems

    NASA Astrophysics Data System (ADS)

    Ren, Beibei; Wang, Yeqin; Zhong, Qing-Chang

    2017-01-01

    In this paper, the control of a PMSG (permanent magnet synchronous generator)-based variable-speed wind turbine system with a back-to-back converter is considered. The uncertainty and disturbance estimator (UDE)-based control approach is applied to the regulation of the DC-link voltage and the control of the RSC (rotor-side converter) and the GSC (grid-side converter). For the rotor-side controller, the UDE-based vector control is developed for the RSC with PMSG control to facilitate the application of the MPPT (maximum power point tracking) algorithm for the maximum wind energy capture. For the grid-side controller, the UDE-based vector control is developed to control the GSC with the power reference generated by a UDE-based DC-link voltage controller. Compared with the conventional vector control, the UDE-based vector control can achieve reliable current decoupling control with fast response. Moreover, the UDE-based DC-link voltage regulation can achieve stable DC-link voltage under model uncertainties and external disturbances, e.g. wind speed variations. The effectiveness of the proposed UDE-based control approach is demonstrated through extensive simulation studies in the presence of coupled dynamics, model uncertainties and external disturbances under varying wind speeds. The UDE-based control is able to generate more energy, e.g. by 5% for the wind profile tested.

  14. Mitigating the negative impacts of tall wind turbines on bats: Vertical activity profiles and relationships to wind speed

    PubMed Central

    Nusslé, Sébastien; Miltner, Daniela; Kohle, Oliver; Glaizot, Olivier; Braunisch, Veronika; Obrist, Martin K.; Arlettaz, Raphaël

    2018-01-01

    Wind turbines represent a source of hazard for bats, especially through collision with rotor blades. With increasing technical development, tall turbines (rotor-swept zone 50–150 m above ground level) are becoming widespread, yet we lack quantitative information about species active at these heights, which impedes proposing targeted mitigation recommendations for bat-friendly turbine operation. We investigated vertical activity profiles of a bat assemblage, and their relationships to wind speed, within a major valley of the European Alps where tall wind turbines are being deployed. To monitor bat activity we installed automatic recorders at sequentially increasing heights from ground level up to 65 m, with the goal to determine species-specific vertical activity profiles and to link them to wind speed. Bat call sequences were analysed with an automatic algorithm, paying particular attention to mouse-eared bats (Myotis myotis and Myotis blythii) and the European free-tailed bat (Tadarida teniotis), three locally rare species. The most often recorded bats were the Common pipistrelle (Pipistrellus pipistrellus) and Savi’s pipistrelle (Hypsugo savii). Mouse-eared bats were rarely recorded, and mostly just above ground, appearing out of risk of collision. T. teniotis had a more evenly distributed vertical activity profile, often being active at rotor level, but its activity at that height ceased above 5 ms-1 wind speed. Overall bat activity in the rotor-swept zone declined with increasing wind speed, dropping below 5% above 5.4 ms-1. Collision risk could be drastically reduced if nocturnal operation of tall wind turbines would be restricted to wind speeds above 5 ms-1. Such measure should be implemented year-round because T. teniotis remains active in winter. This operational restriction is likely to cause only small energy production losses at these tall wind turbines, although further analyses are needed to assess these losses precisely. PMID:29561851

  15. Mitigating the negative impacts of tall wind turbines on bats: Vertical activity profiles and relationships to wind speed.

    PubMed

    Wellig, Sascha D; Nusslé, Sébastien; Miltner, Daniela; Kohle, Oliver; Glaizot, Olivier; Braunisch, Veronika; Obrist, Martin K; Arlettaz, Raphaël

    2018-01-01

    Wind turbines represent a source of hazard for bats, especially through collision with rotor blades. With increasing technical development, tall turbines (rotor-swept zone 50-150 m above ground level) are becoming widespread, yet we lack quantitative information about species active at these heights, which impedes proposing targeted mitigation recommendations for bat-friendly turbine operation. We investigated vertical activity profiles of a bat assemblage, and their relationships to wind speed, within a major valley of the European Alps where tall wind turbines are being deployed. To monitor bat activity we installed automatic recorders at sequentially increasing heights from ground level up to 65 m, with the goal to determine species-specific vertical activity profiles and to link them to wind speed. Bat call sequences were analysed with an automatic algorithm, paying particular attention to mouse-eared bats (Myotis myotis and Myotis blythii) and the European free-tailed bat (Tadarida teniotis), three locally rare species. The most often recorded bats were the Common pipistrelle (Pipistrellus pipistrellus) and Savi's pipistrelle (Hypsugo savii). Mouse-eared bats were rarely recorded, and mostly just above ground, appearing out of risk of collision. T. teniotis had a more evenly distributed vertical activity profile, often being active at rotor level, but its activity at that height ceased above 5 ms-1 wind speed. Overall bat activity in the rotor-swept zone declined with increasing wind speed, dropping below 5% above 5.4 ms-1. Collision risk could be drastically reduced if nocturnal operation of tall wind turbines would be restricted to wind speeds above 5 ms-1. Such measure should be implemented year-round because T. teniotis remains active in winter. This operational restriction is likely to cause only small energy production losses at these tall wind turbines, although further analyses are needed to assess these losses precisely.

  16. An Analysis of Peak Wind Speed Data from Collocated Mechanical and Ultrasonic Anemometers

    NASA Technical Reports Server (NTRS)

    Short, David A.; Wells, Leonard A.; Merceret, Francis J.; Roeder, William P.

    2005-01-01

    This study focuses on a comparison of peak wind speeds reported by mechanical and ultrasonic anemometers at Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC) on the east central coast of Florida and Vandenberg Air Force Base (VAFB) on the central coast of California. The legacy mechanical wind instruments on CCAFS/KSC and VAFB weather towers are being changed from propeller-and-vane (CCAFS/KSC) and cup-and-vane (VAFB) sensors to ultrasonic sensors under the Range Standardization and Automation (RSA) program. The wind tower networks on KSC/CCAFS and VAFB have 41 and 27 towers, respectively. Launch Weather Officers, forecasters, and Range Safety analysts at both locations need to understand the performance of the new wind sensors for a myriad of reasons that include weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The Legacy sensors measure wind speed and direction mechanically. The ultrasonic RSA sensors have no moving parts. Ultrasonic sensors were originally developed to measure very light winds (Lewis and Dover 2004). The technology has evolved and now ultrasonic sensors provide reliable wind data over a broad range of wind speeds. However, because ultrasonic sensors respond more quickly than mechanical sensors to rapid fluctuations in speed, characteristic of gusty wind conditions, comparisons of data from the two sensor types have shown differences in the statistics of peak wind speeds (Lewis and Dover 2004). The 45th Weather Squadron (45 WS) and the 30 WS requested the Applied Meteorology Unit (AMU) to compare data from RSA and Legacy sensors to determine if there are significant differences in peak wind speed information from the two systems.

  17. Equinoctial asymmetry in the zonal distribution of scintillation as observed by GPS receivers in Indonesia

    NASA Astrophysics Data System (ADS)

    Abadi, P.; Otsuka, Y.; Shiokawa, K.; Husin, A.; Liu, Huixin; Saito, S.

    2017-08-01

    We investigate the azimuthal distribution of amplitude scintillation observed by Global Positioning System (GPS) ground receivers at Pontianak (0.0°S, 109.3°E; magnetic latitude: 9.8°S) and Bandung (6.9°S, 107.6°E; magnetic latitude: 16.7°S) in Indonesia in March and September from 2011 to 2015. The scintillation is found to occur more to the west than to the east in March at both stations, whereas no such zonal difference is found in September. We also analyze the zonal scintillation drift as estimated using three closely spaced single-frequency GPS receivers at Kototabang (0.2°S, 100.3°E; magnetic latitude: 9.9°S) in Indonesia during 2003-2015 and the zonal thermospheric neutral wind as measured by the CHAMP satellite at longitudes of 90°-120°E during 2001-2008. We find that the velocities of both the zonal scintillation drift and the neutral wind decrease with increasing latitudes. Interestingly, the latitudinal gradients of both the zonal scintillation drift and the neutral wind are steeper in March than in September. These steeper March gradients may be responsible for the increased westward altitudinal and latitudinal tilting of plasma bubbles in March. This equinoctial asymmetry could be responsible for the observed westward bias in scintillation in March, because the scintillation is more likely to occur when radio waves pass through longer lengths of plasma irregularities in the plasma bubbles.

  18. Effect of wind speed on performance of a solar-pv array

    USDA-ARS?s Scientific Manuscript database

    Thousands of solar photovoltaic (PV) arrays have been installed over the past few years, but the effect of wind speed on the predicted performance of PV arrays is not usually considered by installers. An increase in wind speed will cool the PV array, and the electrical power of the PV modules will ...

  19. Stability Augmentation of Wind Farm using Variable Speed Permanent Magnet Synchronous Generator

    NASA Astrophysics Data System (ADS)

    Rosyadi, Marwan; Muyeen, S. M.; Takahashi, Rion; Tamura, Junji

    This paper presents a new control strategy of variable speed permanent magnet wind generator for stability augmentation of wind farm including fixed speed wind turbine with Induction Generator (IG). A new control scheme is developed for two levels back-to-back converters of Permanent Magnet Synchronous Generator (PMSG), by which both active and reactive powers delivered to the grid can be controlled easily. To avoid the converter damage, the DC link protection controller is also proposed in order to protect the dc link circuit during fault condition. To evaluate the control capability of the proposed controllers, simulations are performed on two model systems composed of wind farms connected to an infinite bus. From transient and steady state analyses by using PSCAD/EMTDC, it is concluded that the proposed control scheme is very effective to improve the stability of wind farm for severe network disturbance and randomly fluctuating wind speed.

  20. Power Smoothing of a Variable-Speed Wind Turbine Generator in Association With the Rotor-Speed-Dependent Gain

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kim, Yeonhee; Kang, Moses; Muljadi, Eduard

    This paper proposes a power-smoothing scheme for a variable-speed wind turbine generator (WTG) that can smooth out the WTG's fluctuating power caused by varying wind speeds, and thereby keep the system frequency within a narrow range. The proposed scheme employs an additional loop based on the system frequency deviation that operates in conjunction with the maximum power point tracking (MPPT) control loop. Unlike the conventional, fixed-gain scheme, its control gain is modified with the rotor speed. In the proposed scheme, the control gain is determined by considering the ratio of the output of the additional loop to that of themore » MPPT loop. To improve the contribution of the scheme toward maintaining the frequency while ensuring the stable operation of WTGs, in the low rotor speed region, the ratio is set to be proportional to the rotor speed; in the high rotor speed region, the ratio remains constant. The performance of the proposed scheme is investigated under varying wind conditions for the IEEE 14-bus system. The simulation results demonstrate that the scheme successfully operates regardless of the output power fluctuation of a WTG by adjusting the gain with the rotor speed, and thereby improves the frequency-regulating capability of a WTG.« less

  1. Increased Surface Wind Speeds Follow Diminishing Arctic Sea Ice

    NASA Astrophysics Data System (ADS)

    Mioduszewski, J.; Vavrus, S. J.; Wang, M.; Holland, M. M.; Landrum, L.

    2017-12-01

    Projections of Arctic sea ice through the end of the 21st century indicate the likelihood of a strong reduction in ice area and thickness in all seasons, leading to a substantial thermodynamic influence on the overlying atmosphere. This is likely to have an effect on winds over the Arctic Basin, due to changes in atmospheric stability and/or baroclinicity. Prior research on future Arctic wind changes is limited and has focused mainly on the practical impacts on wave heights in certain seasons. Here we attempt to identify patterns and likely mechanisms responsible for surface wind changes in all seasons across the Arctic, particularly those associated with sea ice loss in the marginal ice zone. Sea level pressure, near-surface (10 m) and upper-air (850 hPa) wind speeds, and lower-level dynamic and thermodynamic variables from the Community Earth System Model Large Ensemble Project (CESM-LE) were analyzed for the periods 1971-2000 and 2071-2100 to facilitate comparison between a present-day and future climate. Mean near-surface wind speeds over the Arctic Ocean are projected to increase by late century in all seasons but especially during autumn and winter, when they strengthen by up to 50% locally. The most extreme wind speeds in the 90th percentile change even more, increasing in frequency by over 100%. The strengthened winds are closely linked to decreasing lower-tropospheric stability resulting from the loss of sea ice cover and consequent surface warming (locally over 20 ºC warmer in autumn and winter). A muted pattern of these future changes is simulated in CESM-LE historical runs from 1920-2005. The enhanced winds near the surface are mostly collocated with weaker winds above the boundary layer during autumn and winter, implying more vigorous vertical mixing and a drawdown of high-momentum air.The implications of stronger future winds include increased coastal hazards and the potential for a positive feedback with sea ice by generating higher winds and

  2. Aeolian saltation on Mars at low wind speeds

    NASA Astrophysics Data System (ADS)

    Sullivan, R.; Kok, J. F.

    2017-10-01

    Laboratory experiments indicate that the fluid threshold friction speed, u*tf, required to initiate fully developed aeolian saltation is much higher on Mars than on Earth. A discrepancy exists between Mars climate models that do not predict winds this strong and observations that sand-sized particles are indeed moving. This paper describes how wind friction speeds well below u*tf, but above the impact threshold, u*ti, required to sustain saltation, can initiate sustained saltation on Mars, but at relatively low flux. Numerical experiments indicate that a sand grain on Mars mobilized sporadically between u*ti and u*tf will develop, over fetch lengths longer than generally available within low-pressure wind tunnels, trajectories capable of splashing grains that propagate saltation and collectively form a cluster of saltating grains that migrate downwind together. The passage of a saltation cluster should leave behind a narrow zone of affected surface grains. The cumulative effect of many clusters represents a low-flux phenomenon that should produce slow changes to aeolian bedforms over periods in which winds remain close to u*ti and never or rarely reach u*tf. Field evidence from small impact ripples along rover traverses is consistent with effects of saltation at these low friction speeds, without obvious evidence for events ≥u*tf. The potential utility of this grain mobility process is that it can operate entirely at more common winds well below u*tf and so help explain widespread sand movements observed on Mars wherever evidence might be mostly absent for u*tf being exceeded.

  3. Generation and Validation of Spatial Distribution of Hourly Wind Speed Time-Series using Machine Learning

    NASA Astrophysics Data System (ADS)

    Veronesi, F.; Grassi, S.

    2016-09-01

    Wind resource assessment is a key aspect of wind farm planning since it allows to estimate the long term electricity production. Moreover, wind speed time-series at high resolution are helpful to estimate the temporal changes of the electricity generation and indispensable to design stand-alone systems, which are affected by the mismatch of supply and demand. In this work, we present a new generalized statistical methodology to generate the spatial distribution of wind speed time-series, using Switzerland as a case study. This research is based upon a machine learning model and demonstrates that statistical wind resource assessment can successfully be used for estimating wind speed time-series. In fact, this method is able to obtain reliable wind speed estimates and propagate all the sources of uncertainty (from the measurements to the mapping process) in an efficient way, i.e. minimizing computational time and load. This allows not only an accurate estimation, but the creation of precise confidence intervals to map the stochasticity of the wind resource for a particular site. The validation shows that machine learning can minimize the bias of the wind speed hourly estimates. Moreover, for each mapped location this method delivers not only the mean wind speed, but also its confidence interval, which are crucial data for planners.

  4. Assessing the Impact of Different Measurement Time Intervals on Observed Long-Term Wind Speed Trends

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, C.; Vicente-Serrano, S. M.; McVicar, T.; Jerez, S.; Revuelto, J.; López Moreno, J. I.

    2014-12-01

    During the last two decades climate studies have reported a tendency toward a decline in measured near-surface wind speed in some regions of Europe, North America, Asia and Australia. This weakening in observed wind speed has been recently termed "global stilling", showing a worldwide average trend of -0.140 m s-1 dec-1 during last 50-years. The precise cause of the "global stilling" remains largely uncertain and has been hypothetically attributed to several factors, mainly related to: (i) an increasing surface roughness (i.e. forest growth, land use changes, and urbanization); (ii) a slowdown in large-scale atmospheric circulation; (iii) instrumental drifts and technological improvements, maintenance, and shifts in measurements sites and calibration issues; (iv) sunlight dimming due to air pollution; and (v) astronomical changes. This study proposed a novel investigation aimed at analyzing how different measurement time intervals used to calculate a wind speed series can affect the sign and magnitude of long-term wind speed trends. For instance, National Weather Services across the globe estimate daily average wind speed using different time intervals and formulae that may affect the trend results. Firstly, we carried out a comprehensive review of wind studies reporting the sign and magnitude of wind speed trend and the sampling intervals used. Secondly, we analyzed near-surface wind speed trends recorded at 59 land-based stations across Spain comparing monthly mean wind speed series obtained from: (a) daily mean wind speed data averaged from standard 10-min mean observations at 0000, 0700, 1300 and 1800 UTC; and (b) average wind speed of 24 hourly measurements (i.e., wind run measurements) from 0000 to 2400 UTC. Thirdly and finally, we quantified the impact of anemometer drift (i.e. bearing malfunction) by presenting preliminary results (1-year of paired measurements) from a comparison of one new anemometer sensor against one malfunctioned anenometer sensor due

  5. Short, large amplitude speed enhancements in the near-Sun fast solar wind

    NASA Astrophysics Data System (ADS)

    Horbury, T. S.; Matteini, L.; Stansby, D.

    2018-04-01

    We report the presence of intermittent, short discrete enhancements in plasma speed in the near-Sun high speed solar wind. Lasting tens of seconds to minutes in spacecraft measurements at 0.3 AU, speeds inside these enhancements can reach 1000 km/s, corresponding to a kinetic energy up to twice that of the bulk high speed solar wind. These events, which occur around 5% of the time, are Alfvénic in nature with large magnetic field deflections and are the same temperature as the surrounding plasma, in contrast to the bulk fast wind which has a well-established positive speed-temperature correlation. The origin of these speed enhancements is unclear but they may be signatures of discrete jets associated with transient events in the chromosphere or corona. Such large short velocity changes represent a measurement and analysis challenge for the upcoming Parker Solar Probe and Solar Orbiter missions.

  6. Dual stator winding variable speed asynchronous generator: optimal design and experiments

    NASA Astrophysics Data System (ADS)

    Tutelea, L. N.; Deaconu, S. I.; Popa, G. N.

    2015-06-01

    In the present paper is carried out a theoretical and experimental study of dual stator winding squirrel cage asynchronous generator (DSWA) behavior in the presence of saturation regime (non-sinusoidal) due to the variable speed operation. The main aims are the determination of the relations of calculating the equivalent parameters of the machine windings to optimal design using a Matlab code. Issue is limited to three phase range of double stator winding cage-induction generator of small sized powers, the most currently used in the small adjustable speed wind or hydro power plants. The tests were carried out using three-phase asynchronous generator having rated power of 6 [kVA].

  7. Short-term wind speed prediction based on the wavelet transformation and Adaboost neural network

    NASA Astrophysics Data System (ADS)

    Hai, Zhou; Xiang, Zhu; Haijian, Shao; Ji, Wu

    2018-03-01

    The operation of the power grid will be affected inevitably with the increasing scale of wind farm due to the inherent randomness and uncertainty, so the accurate wind speed forecasting is critical for the stability of the grid operation. Typically, the traditional forecasting method does not take into account the frequency characteristics of wind speed, which cannot reflect the nature of the wind speed signal changes result from the low generality ability of the model structure. AdaBoost neural network in combination with the multi-resolution and multi-scale decomposition of wind speed is proposed to design the model structure in order to improve the forecasting accuracy and generality ability. The experimental evaluation using the data from a real wind farm in Jiangsu province is given to demonstrate the proposed strategy can improve the robust and accuracy of the forecasted variable.

  8. Coronal holes and high-speed wind streams

    NASA Technical Reports Server (NTRS)

    Zirker, J. B.

    1977-01-01

    Coronal holes, regions of unusually low density and low temperature in the solar corona, are identified as Bartel's M regions, i.e., sources of high-speed wind streams that produce recurrent geomagnetic variations. Throughout the Skylab period the polar caps of the sun were coronal holes, and at lower latitudes the most persistent and recurrent holes were equatorial extensions of the polar caps. The holes rotated 'rigidly' at the equatorial synodic rate. They formed in regions of unipolar photospheric magnetic field, and their internal magnetic fields diverged rapidly with increasing distance from the sun. The geometry of the magnetic field in the inner corona seems to control both the physical properties of the holes and the global distribution of high-speed wind streams in the heliosphere. Phenomenological models for the birth and decay of coronal holes have been proposed.

  9. Comparison of Speed-Up Over Hills Derived from Wind-Tunnel Experiments, Wind-Loading Standards, and Numerical Modelling

    NASA Astrophysics Data System (ADS)

    Safaei Pirooz, Amir A.; Flay, Richard G. J.

    2018-03-01

    We evaluate the accuracy of the speed-up provided in several wind-loading standards by comparison with wind-tunnel measurements and numerical predictions, which are carried out at a nominal scale of 1:500 and full-scale, respectively. Airflow over two- and three-dimensional bell-shaped hills is numerically modelled using the Reynolds-averaged Navier-Stokes method with a pressure-driven atmospheric boundary layer and three different turbulence models. Investigated in detail are the effects of grid size on the speed-up and flow separation, as well as the resulting uncertainties in the numerical simulations. Good agreement is obtained between the numerical prediction of speed-up, as well as the wake region size and location, with that according to large-eddy simulations and the wind-tunnel results. The numerical results demonstrate the ability to predict the airflow over a hill with good accuracy with considerably less computational time than for large-eddy simulation. Numerical simulations for a three-dimensional hill show that the speed-up and the wake region decrease significantly when compared with the flow over two-dimensional hills due to the secondary flow around three-dimensional hills. Different hill slopes and shapes are simulated numerically to investigate the effect of hill profile on the speed-up. In comparison with more peaked hill crests, flat-topped hills have a lower speed-up at the crest up to heights of about half the hill height, for which none of the standards gives entirely satisfactory values of speed-up. Overall, the latest versions of the National Building Code of Canada and the Australian and New Zealand Standard give the best predictions of wind speed over isolated hills.

  10. Wind speed reductions by large-scale wind turbine deployments lower turbine efficiencies and set low generation limits

    PubMed Central

    Miller, Lee M.; Kleidon, Axel

    2016-01-01

    Wind turbines generate electricity by removing kinetic energy from the atmosphere. Large numbers of wind turbines are likely to reduce wind speeds, which lowers estimates of electricity generation from what would be presumed from unaffected conditions. Here, we test how well wind power limits that account for this effect can be estimated without explicitly simulating atmospheric dynamics. We first use simulations with an atmospheric general circulation model (GCM) that explicitly simulates the effects of wind turbines to derive wind power limits (GCM estimate), and compare them to a simple approach derived from the climatological conditions without turbines [vertical kinetic energy (VKE) estimate]. On land, we find strong agreement between the VKE and GCM estimates with respect to electricity generation rates (0.32 and 0.37 We m−2) and wind speed reductions by 42 and 44%. Over ocean, the GCM estimate is about twice the VKE estimate (0.59 and 0.29 We m−2) and yet with comparable wind speed reductions (50 and 42%). We then show that this bias can be corrected by modifying the downward momentum flux to the surface. Thus, large-scale limits to wind power use can be derived from climatological conditions without explicitly simulating atmospheric dynamics. Consistent with the GCM simulations, the approach estimates that only comparatively few land areas are suitable to generate more than 1 We m−2 of electricity and that larger deployment scales are likely to reduce the expected electricity generation rate of each turbine. We conclude that these atmospheric effects are relevant for planning the future expansion of wind power. PMID:27849587

  11. Interplanetary gas. XX - Does the radial solar wind speed increase with latitude

    NASA Technical Reports Server (NTRS)

    Brandt, J. C.; Harrington, R. S.; Roosen, R. G.

    1975-01-01

    The astrometric technique used to derive solar wind speeds from ionic comet-tail orientations has been used to test the suggestion that the radial solar wind speed is higher near the solar poles than near the equator. We find no evidence for the suggested latitude variation.

  12. Substorm-related thermospheric density and wind disturbances derived from CHAMP observations

    NASA Astrophysics Data System (ADS)

    Ritter, P.; Lühr, H.; Doornbos, E.

    2010-06-01

    The input of energy and momentum from the magnetosphere is most efficiently coupled into the high latitude ionosphere-thermosphere. The phenomenon we are focusing on here is the magnetospheric substorm. This paper presents substorm related observations of the thermosphere derived from the CHAMP satellite. With its sensitive accelerometer the satellite can measure the air density and zonal winds. Based on a large number of substorm events the average high and low latitude thermospheric response to substorm onsets was deduced. During magnetic substorms the thermospheric density is enhanced first at high latitudes. Then the disturbance travels at an average speed of 650 m/s to lower latitudes, and 3-4 h later the bulge reaches the equator on the night side. Under the influence of the Coriolis force the travelling atmospheric disturbance (TAD) is deflected westward. In accordance with present-day atmospheric models the disturbance zonal wind velocities during substorms are close to zero near the equator before midnight and attain moderate westward velocities after midnight. In general, the wind system is only weakly perturbed (Δvy<20 m/s) by substorms.

  13. Wind Speed Measurement by Paper Anemometer

    ERIC Educational Resources Information Center

    Zhong, Juhua; Cheng, Zhongqi; Guan, Wenchuan

    2011-01-01

    A simple wind speed measurement device, a paper anemometer, is fabricated based on the theory of standing waves. In providing the working profile of the paper anemometer, an experimental device is established, which consists of an anemometer sensor, a sound sensor, a microphone, paper strips, a paper cup, and sonic acquisition software. It shows…

  14. Analysis of the Flicker Level Produced by a Fixed-Speed Wind Turbine

    NASA Astrophysics Data System (ADS)

    Suppioni, Vinicius; P. Grilo, Ahda

    2013-10-01

    In this article, the analysis of the flicker emission during continuous operation of a mid-scale fixed-speed wind turbine connected to a distribution system is presented. Flicker emission is investigated based on simulation results, and the dependence of flicker emission on short-circuit capacity, grid impedance angle, mean wind speed, and wind turbulence is analyzed. The simulations were conducted in different programs in order to provide a more realistic wind emulation and detailed model of mechanical and electrical components of the wind turbine. Such aim is accomplished by using FAST (Fatigue, Aerodynamics, Structures, and Turbulence) to simulate the mechanical parts of the wind turbine, Simulink/MatLab to simulate the electrical system, and TurbSim to obtain the wind model. The results show that, even for a small wind generator, the flicker level can limit the wind power capacity installed in a distribution system.

  15. Changes in wind speed and extremes in Beijing during 1960-2008 based on homogenized observations

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Yan, Zhongwei; Tu, Kai; Liu, Weidong; Wang, Yingchun

    2011-03-01

    Daily observations of wind speed at 12 stations in the Greater Beijing Area during 1960-2008 were homogenized using the Multiple Analysis of Series for Homogenization method. The linear trends in the regional mean annual and seasonal (winter, spring, summer and autumn) wind speed series were -0.26, -0.39, -0.30, -0.12 and -0.22 m s-1 (10 yr)-1, respectively. Winter showed the greatest magnitude in declining wind speed, followed by spring, autumn and summer. The annual and seasonal frequencies of wind speed extremes (days) also decreased, more prominently for winter than for the other seasons. The declining trends in wind speed and extremes were formed mainly by some rapid declines during the 1970s and 1980s. The maximum declining trend in wind speed occurred at Chaoyang (CY), a station within the central business district (CBD) of Beijing with the highest level of urbanization. The declining trends were in general smaller in magnitude away from the city center, except for the winter case in which the maximum declining trend shifted northeastward to rural Miyun (MY). The influence of urbanization on the annual wind speed was estimated to be about -0.05 m s-1 (10 yr)-1 during 1960-2008, accounting for around one fifth of the regional mean declining trend. The annual and seasonal geostrophic wind speeds around Beijing, based on daily mean sea level pressure (MSLP) from the ERA-40 reanalysis dataset, also exhibited decreasing trends, coincident with the results from site observations. A comparative analysis of the MSLP fields between 1966-1975 and 1992-2001 suggested that the influences of both the winter and summer monsoons on Beijing were weaker in the more recent of the two decades. It is suggested that the bulk of wind in Beijing is influenced considerably by urbanization, while changes in strong winds or wind speed extremes are prone to large-scale climate change in the region.

  16. Multifractal analysis of the time series of daily means of wind speed in complex regions

    NASA Astrophysics Data System (ADS)

    Laib, Mohamed; Golay, Jean; Telesca, Luciano; Kanevski, Mikhail

    2018-04-01

    In this paper, we applied the multifractal detrended fluctuation analysis to the daily means of wind speed measured by 119 weather stations distributed over the territory of Switzerland. The analysis was focused on the inner time fluctuations of wind speed, which could be more linked with the local conditions of the highly varying topography of Switzerland. Our findings point out to a persistent behaviour of all the measured wind speed series (indicated by a Hurst exponent significantly larger than 0.5), and to a high multifractality degree indicating a relative dominance of the large fluctuations in the dynamics of wind speed, especially in the Swiss plateau, which is comprised between the Jura and Alp mountain ranges. The study represents a contribution to the understanding of the dynamical mechanisms of wind speed variability in mountainous regions.

  17. A storm severity index based on return levels of wind speeds

    NASA Astrophysics Data System (ADS)

    Becker, Nico; Nissen, Katrin M.; Ulbrich, Uwe

    2015-04-01

    European windstorms related to extra-tropical cyclones cause considerable damages to infrastructure during the winter season. Leckebusch et al. (2008) introduced a storm severity index (SSI) based on the exceedances of the local 98th percentile of wind speeds. The SSI is based on the assumption that (insured) damage usually occurs within the upper 2%-quantile of the local wind speed distribution (i.e. if the 98th percentile is exceeded). However, critical infrastructure, for example related to the power network or the transportation system, is usually designed to withstand wind speeds reaching the local 50-year return level, which is much higher than the 98th percentile. The aim of this work is to use the 50-year return level to develop a modified SSI, which takes into account only extreme wind speeds relevant to critical infrastructure. As a first step we use the block maxima approach to estimate the spatial distribution of return levels by fitting the generalized extreme value (GEV) distribution to the wind speeds retrieved from different reanalysis products. We show that the spatial distributions of the 50-year return levels derived from different reanalyses agree well within large parts of Europe. The differences between the reanalyses are largely within the range of the uncertainty intervals of the estimated return levels. As a second step the exceedances of the 50-year return level are evaluated and compared to the exceedances of the 98th percentiles for different extreme European windstorms. The areas where the wind speeds exceed the 50-year return level in the reanalysis data do largely agree with the areas where the largest damages were reported, e.g. France in the case of "Lothar" and "Martin" and Central Europe in the case of "Kyrill". Leckebusch, G. C., Renggli, D., & Ulbrich, U. (2008). Development and application of an objective storm severity measure for the Northeast Atlantic region. Meteorologische Zeitschrift, 17(5), 575-587.

  18. Wind speed reductions by large-scale wind turbine deployments lower turbine efficiencies and set low generation limits.

    PubMed

    Miller, Lee M; Kleidon, Axel

    2016-11-29

    Wind turbines generate electricity by removing kinetic energy from the atmosphere. Large numbers of wind turbines are likely to reduce wind speeds, which lowers estimates of electricity generation from what would be presumed from unaffected conditions. Here, we test how well wind power limits that account for this effect can be estimated without explicitly simulating atmospheric dynamics. We first use simulations with an atmospheric general circulation model (GCM) that explicitly simulates the effects of wind turbines to derive wind power limits (GCM estimate), and compare them to a simple approach derived from the climatological conditions without turbines [vertical kinetic energy (VKE) estimate]. On land, we find strong agreement between the VKE and GCM estimates with respect to electricity generation rates (0.32 and 0.37 W e m -2 ) and wind speed reductions by 42 and 44%. Over ocean, the GCM estimate is about twice the VKE estimate (0.59 and 0.29 W e m -2 ) and yet with comparable wind speed reductions (50 and 42%). We then show that this bias can be corrected by modifying the downward momentum flux to the surface. Thus, large-scale limits to wind power use can be derived from climatological conditions without explicitly simulating atmospheric dynamics. Consistent with the GCM simulations, the approach estimates that only comparatively few land areas are suitable to generate more than 1 W e m -2 of electricity and that larger deployment scales are likely to reduce the expected electricity generation rate of each turbine. We conclude that these atmospheric effects are relevant for planning the future expansion of wind power.

  19. Three-dimensional vapor intrusion modeling approach that combines wind and stack effects on indoor, atmospheric, and subsurface domains.

    PubMed

    Shirazi, Elham; Pennell, Kelly G

    2017-12-13

    Vapor intrusion (IV) exposure risks are difficult to characterize due to the role of atmospheric, building and subsurface processes. This study presents a three-dimensional VI model that extends the common subsurface fate and transport equations to incorporate wind and stack effects on indoor air pressure, building air exchange rate (AER) and indoor contaminant concentration to improve VI exposure risk estimates. The model incorporates three modeling programs: (1) COMSOL Multiphysics to model subsurface fate and transport processes, (2) CFD0 to model atmospheric air flow around the building, and (3) CONTAM to model indoor air quality. The combined VI model predicts AER values, zonal indoor air pressures and zonal indoor air contaminant concentrations as a function of wind speed, wind direction and outdoor and indoor temperature. Steady state modeling results for a single-story building with a basement demonstrate that wind speed, wind direction and opening locations in a building play important roles in changing the AER, indoor air pressure, and indoor air contaminant concentration. Calculated indoor air pressures ranged from approximately -10 Pa to +4 Pa depending on weather conditions and building characteristics. AER values, mass entry rates and indoor air concentrations vary depending on weather conditions and building characteristics. The presented modeling approach can be used to investigate the relationship between building features, AER, building pressures, soil gas concentrations, indoor air concentrations and VI exposure risks.

  20. Recent recovery of surface wind speed after decadal decrease: a focus on South Korea

    NASA Astrophysics Data System (ADS)

    Kim, JongChun; Paik, Kyungrock

    2015-09-01

    We investigate the multi-decadal variability of observed surface wind speed around South Korea. It is found that surface wind speed exhibits decreasing trend from mid-1950s until 2003, which is similar with the trends reported for other parts of the world. However, the decreasing trend ceases and becomes unclear since then. It is revealed that decreasing wind speed until 2003 is strongly associated with the decreasing trend of the spatial variance in both atmospheric pressure and air temperature across the East Asia for the same period. On the contrary, break of decreasing trend in surface wind speed since 2003 is associated with increasing spatial variance in surface temperature over the East Asia. Ground observation shows that surface wind speed and air temperature exhibit highly negative correlations for both summer and winter prior to 2003. However, since 2003, the correlations differ between seasons. We suggest that mechanisms behind the recent wind speed trend are different between summer and winter. This is on the basis of an interesting finding that air temperature has decreased while surface temperature has increased during winter months since 2003. We hypothesize that such contrasting temperature trends indicate more frequent movement of external cold air mass into the region since 2003. We also hypothesize that increasing summer wind speed is driven by intrusion of warm air mass into the region which is witnessed via increasing spatial variance in surface temperature across East Asia and the fact that both air and surface temperature rise together.

  1. One- to two-month oscillations in SSMI surface wind speed in western tropical Pacific Ocean

    NASA Technical Reports Server (NTRS)

    Collins, Michael L.; Stanford, John L.; Halpern, David

    1994-01-01

    The 10-m wind speed over the ocean can be estimated from microwave brightness temperature measurements recorded by the Special Sensor Microwave Imager (SSMI) instrument mounted on a polar-orbiting spacecraft. Four-year (1988-1991) time series of average daily 1 deg x 1 deg SSMI wind speeds were analyzed at selected sites in the western tropical Pacific Ocean. One- to two-month period wind speed oscillations with amplitudes statistically significant at the 95% confidence level were observed near Kanton, Eniwetok, Guam, and Truk. This is the first report of such an oscillation in SSMI wind speeds.

  2. Multi-step-ahead Method for Wind Speed Prediction Correction Based on Numerical Weather Prediction and Historical Measurement Data

    NASA Astrophysics Data System (ADS)

    Wang, Han; Yan, Jie; Liu, Yongqian; Han, Shuang; Li, Li; Zhao, Jing

    2017-11-01

    Increasing the accuracy of wind speed prediction lays solid foundation to the reliability of wind power forecasting. Most traditional correction methods for wind speed prediction establish the mapping relationship between wind speed of the numerical weather prediction (NWP) and the historical measurement data (HMD) at the corresponding time slot, which is free of time-dependent impacts of wind speed time series. In this paper, a multi-step-ahead wind speed prediction correction method is proposed with consideration of the passing effects from wind speed at the previous time slot. To this end, the proposed method employs both NWP and HMD as model inputs and the training labels. First, the probabilistic analysis of the NWP deviation for different wind speed bins is calculated to illustrate the inadequacy of the traditional time-independent mapping strategy. Then, support vector machine (SVM) is utilized as example to implement the proposed mapping strategy and to establish the correction model for all the wind speed bins. One Chinese wind farm in northern part of China is taken as example to validate the proposed method. Three benchmark methods of wind speed prediction are used to compare the performance. The results show that the proposed model has the best performance under different time horizons.

  3. Electron bulk speed lags the protons in the collisionless solar wind

    NASA Astrophysics Data System (ADS)

    Tong, Y.; Bale, S. D.; Salem, C. S.; Pulupa, M.

    2017-12-01

    We use a large, statistical set of in situ measurements of the solar wind electron distribution from the Wind/3DP instrument to show that the magnetic field-aligned core electron-proton drift speed tend to small values at high collisionality and asymptotes towards a large limiting value in the collisionless limit. This collisionless drift-limit, when normalized to the local Alfven speed is large and may drive instabilities.

  4. Evaluation of SEASAT-A SMMR derived wind speed measurements

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Wind speeds derived from versions of the least-squares and regression algorithms developed after the JASIN Workshop were evaluated. The accuracy of scanning multichannel microwave radiometer (SMMR) wind retrievals was determined in terms of the intrinsic accuracy of a baseline surface truth data set in favorable conditions. Effects which degrade the wind retrievals or introduce biases were identified and assessed. The performance of the SMMR in storms was ascertained with particular emphasis on the effects of rain.

  5. Velocity Measurement Systems for a Low-speed Wind Tunnel

    DTIC Science & Technology

    2015-04-29

    Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 wind tunnel PIV hot wire particle image velocimetry REPORT DOCUMENTATION PAGE 11. SPONSOR...Velocity Measurement Systems for a Low-speed Wind Tunnel Report Title Funds were provided by the ARO for the purchase of TSI hot- wire anemometer equipment...implemented. In the summer of 2011, the focus of the summer camp was on wind turbines , and for the last two summers, the STEM outreach camp has studied

  6. Impact of Stratospheric Ozone Zonal Asymmetries on the Tropospheric Circulation

    NASA Technical Reports Server (NTRS)

    Tweedy, Olga; Waugh, Darryn; Li, Feng; Oman, Luke

    2015-01-01

    The depletion and recovery of Antarctic ozone plays a major role in changes of Southern Hemisphere (SH) tropospheric climate. Recent studies indicate that the lack of polar ozone asymmetries in chemistry climate models (CCM) leads to a weaker and warmer Antarctic vortex, and smaller trends in the tropospheric mid-latitude jet and the surface pressure. However, the tropospheric response to ozone asymmetries is not well understood. In this study we report on a series of integrations of the Goddard Earth Observing System Chemistry Climate Model (GEOS CCM) to further examine the effect of zonal asymmetries on the state of the stratosphere and troposphere. Integrations with the full, interactive stratospheric chemistry are compared against identical simulations using the same CCM except that (1) the monthly mean zonal mean stratospheric ozone from first simulation is prescribed and (2) ozone is relaxed to the monthly mean zonal mean ozone on a three day time scale. To analyze the tropospheric response to ozone asymmetries, we examine trends and quantify the differences in temperatures, zonal wind and surface pressure among the integrations.

  7. Polymer Piezoelectric Energy Harvesters for Low Wind Speed

    DOE PAGES

    Li, Dong Jun; Hong, Seungbum; Gu, Shiyuan; ...

    2014-01-06

    We fabricated polymer piezoelectric energy harvesters (PEHs) that can generate electric power at wind speed of less than 4.7 m/s due to their high sensitivity to wind. In order to optimize their operating conditions, we evaluated three distinct PEH operation modes under the boundary conditions of single-side clamping. We found that a PEH connected to an external load of 120 kΩ shows the largest output power of 0.98 μW at 3.9m/s, with wind incident on its side (mode I). We attribute this result to large bending and torsion involved in this operation mode.

  8. 11- and 22-year variations of the cosmic ray density and of the solar wind speed

    NASA Technical Reports Server (NTRS)

    Chirkov, N. P.

    1985-01-01

    Cosmic ray density variations for 17-21 solar activity cycles and the solar wind speed for 20-21 events are investigated. The 22-year solar wind speed recurrence was found in even and odd cycles. The 22-year variations of cosmic ray density were found to be opposite that of solar wind speed and solar activity. The account of solar wind speed in 11-year variations significantly decreases the modulation region of cosmic rays when E = 10-20 GeV.

  9. High wind speeds prevent formation of a distinct bacterioneuston community in the sea-surface microlayer

    PubMed Central

    Stolle, Christian; Giebel, Helge-Ansgar; Brinkhoff, Thorsten; Ribas-Ribas, Mariana; Hodapp, Dorothee; Wurl, Oliver

    2017-01-01

    Abstract The sea-surface microlayer (SML) at the boundary between atmosphere and hydrosphere represents a demanding habitat for bacteria. Wind speed is a crucial but poorly studied factor for its physical integrity. Increasing atmospheric burden of CO2, as suggested for future climate scenarios, may particularly act on this habitat at the air–sea interface. We investigated the effect of increasing wind speeds and different pCO2 levels on SML microbial communities in a wind-wave tunnel, which offered the advantage of low spatial and temporal variability. We found that enrichment of bacteria in the SML occurred solely at a U10 wind speed of ≤5.6 m s−1 in the tunnel and ≤4.1 m s−1 in the Baltic Sea. High pCO2 levels further intensified the bacterial enrichment in the SML during low wind speed. In addition, low wind speed and pCO2 induced the formation of a distinctive bacterial community as revealed by 16S rRNA gene fingerprints and influenced the presence or absence of individual taxonomic units within the SML. We conclude that physical stability of the SML below a system-specific wind speed threshold induces specific bacterial communities in the SML entailing strong implications for ecosystem functioning by wind-driven impacts on habitat properties, gas exchange and matter cycling processes. PMID:28369320

  10. High wind speeds prevent formation of a distinct bacterioneuston community in the sea-surface microlayer.

    PubMed

    Rahlff, Janina; Stolle, Christian; Giebel, Helge-Ansgar; Brinkhoff, Thorsten; Ribas-Ribas, Mariana; Hodapp, Dorothee; Wurl, Oliver

    2017-05-01

    The sea-surface microlayer (SML) at the boundary between atmosphere and hydrosphere represents a demanding habitat for bacteria. Wind speed is a crucial but poorly studied factor for its physical integrity. Increasing atmospheric burden of CO2, as suggested for future climate scenarios, may particularly act on this habitat at the air-sea interface. We investigated the effect of increasing wind speeds and different pCO2 levels on SML microbial communities in a wind-wave tunnel, which offered the advantage of low spatial and temporal variability. We found that enrichment of bacteria in the SML occurred solely at a U10 wind speed of ≤5.6 m s-1 in the tunnel and ≤4.1 m s-1 in the Baltic Sea. High pCO2 levels further intensified the bacterial enrichment in the SML during low wind speed. In addition, low wind speed and pCO2 induced the formation of a distinctive bacterial community as revealed by 16S rRNA gene fingerprints and influenced the presence or absence of individual taxonomic units within the SML. We conclude that physical stability of the SML below a system-specific wind speed threshold induces specific bacterial communities in the SML entailing strong implications for ecosystem functioning by wind-driven impacts on habitat properties, gas exchange and matter cycling processes. © FEMS 2017.

  11. Flight measurement and analysis of AAFE RADSCAT wind speed signature of the ocean

    NASA Technical Reports Server (NTRS)

    Schroeder, L. C.; Jones, W. L.; Schaffner, P. R.; Mitchell, J. L.

    1984-01-01

    The advanced aerospace flight experiment radiometer scatterometer (AAFE RADSCAT) which was developed as a research tool to evaluate the use of microwave frequency remote sensors to provide wind speed information at the ocean surface is discussed. The AAFE RADSCAT helped establish the feasibility of the satellite scatterometer for measuring both wind speed and direction. The most important function of the AAFE RADSCAT was to provide a data base of ocean normalized radar cross section (NRCS) measurements as a function of surface wind vector at 13.9 GHz. The NRCS measurements over a wide parametric range of incidence angles, azimuth angles, and winds were obtained in a series of RADSCAT aircraft missions. The obtained data base was used to model the relationship between k sub u band radar signature and ocean surface wind vector. The models developed therefrom are compared with those used for inversion of the SEASAT-A satellite scatterometer (SASS) radar measurements to wind speeds.

  12. Estimation of wind speeds inside Super Typhoon Nepartak from AMSR2 low-frequency brightness temperatures

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Yin, Xiaobin; Shi, Hanqing; Wang, Zhenzhan; Xu, Qing

    2018-04-01

    Accurate estimations of typhoon-level winds are highly desired over the western Pacific Ocean. A wind speed retrieval algorithm is used to retrieve the wind speeds within Super Typhoon Nepartak (2016) using 6.9- and 10.7-GHz brightness temperatures from the Japanese Advanced Microwave Scanning Radiometer 2 (AMSR2) sensor on board the Global Change Observation Mission-Water 1 (GCOM-W1) satellite. The results show that the retrieved wind speeds clearly represent the intensification process of Super Typhoon Nepartak. A good agreement is found between the retrieved wind speeds and the Soil Moisture Active Passive wind speed product. The mean bias is 0.51 m/s, and the root-mean-square difference is 1.93 m/s between them. The retrieved maximum wind speeds are 59.6 m/s at 04:45 UTC on July 6 and 71.3 m/s at 16:58 UTC on July 6. The two results demonstrate good agreement with the results reported by the China Meteorological Administration and the Joint Typhoon Warning Center. In addition, Feng-Yun 2G (FY-2G) satellite infrared images, Feng-Yun 3C (FY-3C) microwave atmospheric sounder data, and AMSR2 brightness temperature images are also used to describe the development and structure of Super Typhoon Nepartak.

  13. Climatology of the relationship of cusp-related density anomaly with zonal wind and large-scale FAC based on CHAMP observations: IMF By and solar cycle dependence

    NASA Astrophysics Data System (ADS)

    Kervalishvili, Guram; Lühr, Hermann

    2014-05-01

    We present climatology of the relationship of cusp-related density enhancement with the neutral zonal wind velocity, large-scale field-aligned current (FAC), small-scale FAC, and electron temperature using the superposed epoch analysis (SEA) method. The dependence of these variables on the interplanetary magnetic field (IMF) By component orientation and solar cycle are of particular interest. In addition, the obtained results of relative density enhancement (ρrel), zonal wind, electron temperature and FAC are subdivided into three local seasons of 130 days each: local winter (1 January ±65 days), combined equinoxes (1 April ±32 days and 1 October ±32 days), and local summer (1 July ±65 days). Our investigation is based on CHAMP satellite observations and NASA/GSFC's OMNI online data set for solar maximum (Mar/2002-2007) and minimum (Mar/2004-2009) conditions in the Northern Hemisphere. The SEA technique uses the time and location of the thermospheric mass density anomaly peaks as reference parameters. The relative amplitude of cusp-related density enhancement does on average not depend on the IMF By orientation, solar cycle phase, and local season. Also, it is apparent that the IMF By amplitude does not have a big influence on the relative amplitude of the density anomaly. Conversely, there exists a good correlation between ρrel and the negative amplitude of IMF Bz prevailing about half an hour earlier. In the cusp region, both large-scale FAC distribution and thermospheric zonal wind velocity exhibit a clear dependence on the IMF By orientation. In the case of positive (negative) IMF By there is a systematic imbalance between downward (upward) and upward (downward) FACs peaks equatorward and poleward of the reference point, respectively. The zonal wind velocity is directed towards west i.e. towards dawn in a geomagnetic latitude-magnetic local time (MLat-MLT) frame. This is true for all local seasons and solar conditions. The thermospheric density

  14. Near-surface wind speed statistical distribution: comparison between ECMWF System 4 and ERA-Interim

    NASA Astrophysics Data System (ADS)

    Marcos, Raül; Gonzalez-Reviriego, Nube; Torralba, Verónica; Cortesi, Nicola; Young, Doo; Doblas-Reyes, Francisco J.

    2017-04-01

    In the framework of seasonal forecast verification, knowing whether the characteristics of the climatological wind speed distribution, simulated by the forecasting systems, are similar to the observed ones is essential to guide the subsequent process of bias adjustment. To bring some light about this topic, this work assesses the properties of the statistical distributions of 10m wind speed from both ERA-Interim reanalysis and seasonal forecasts of ECMWF system 4. The 10m wind speed distribution has been characterized in terms of the four main moments of the probability distribution (mean, standard deviation, skewness and kurtosis) together with the coefficient of variation and goodness of fit Shapiro-Wilks test, allowing the identification of regions with higher wind variability and non-Gaussian behaviour at monthly time-scales. Also, the comparison of the predicted and observed 10m wind speed distributions has been measured considering both inter-annual and intra-seasonal variability. Such a comparison is important in both climate research and climate services communities because it provides useful climate information for decision-making processes and wind industry applications.

  15. Processed Movie of Zonal Jets

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This movie is a manipulated sequence showing motions in Jupiter's atmosphere over the course of five days beginning Oct. 1, 2000, as seen by a camera on NASA's Cassini spacecraft, using a blue filter.

    Beginning with seven images taken at uneven time intervals, this sequence was made by using information on wind speeds derived from actual Jupiter images to create evenly spaced time steps throughout. The final result is a smooth movie sequence consisting of both real and false frames.

    The view is of the opposite side of the planet from Jupiter's Great Red Spot. The region shown reaches from 50 degrees north to 50 degrees south of Jupiter's equator, and extends 100 degrees east-to-west, about one-quarter of Jupiter's circumference. The smallest features are about 500 kilometers (about 300 miles) across.

    Towards the end of the sequence, a shadow appears from one of Jupiter's moons, Europa.

    The movie shows the remains of a historic merger that began several years ago, when three white oval storms that had existed for 60 years merged into two, then one. The resulting oval is visible in the lower left portion of the movie.

    The movie also shows zonal jets that circle the planet on constant latitudes. Winds seen moving toward the left (westward) correspond to features that are rotating a little slower than Jupiter's magnetic field, and winds moving the opposite direction correspond to features that are rotating a little faster than the magnetic field. Since Jupiter has no solid surface, the rotation of the magnetic field is the point of reference for the rotation of the planet.

    Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.

  16. Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank

    NASA Technical Reports Server (NTRS)

    Wanninkhof, Richard H.; Bliven, L. F.

    1991-01-01

    The relationships between the gas exchange, wind speed, friction velocity, and radar backscatter from the water surface was investigated using data obtained in a large water tank in the Delft (Netherlands) wind-wave tunnel, filled with water supersaturated with SF6, N2O, and CH4. Results indicate that the gas-transfer velocities of these substances were related to the wind speed with a power law dependence. Microwave backscatter from water surface was found to be related to gas transfer velocities by a relationship in the form k(gas) = a 10 exp (b A0), where k is the gas transfer velocity for the particular gas, the values of a and b are obtained from a least squares fit of the average backscatter cross section and gas transfer at 80 m, and A0 is the directional (azimuthal) averaged return.

  17. A level 2 wind speed retrieval algorithm for the CYGNSS mission

    NASA Astrophysics Data System (ADS)

    Clarizia, Maria Paola; Ruf, Christopher; O'Brien, Andrew; Gleason, Scott

    2014-05-01

    The NASA EV-2 Cyclone Global Navigation Satellite System (CYGNSS) is a spaceborne mission focused on tropical cyclone (TC) inner core process studies. CYGNSS consists of a constellation of 8 microsatellites, which will measure ocean surface wind speed in all precipitating conditions, including those experienced in the TC eyewall, and with sufficient frequency to resolve genesis and rapid intensification. It does so through the use of an innovative remote sensing technique, known as Global Navigation Satellite System-Reflectometry, or GNSS-R. GNSS-R uses signals of opportunity from navigation constellations (e.g. GPS, GLONASS, Galileo), scattered by the surface of the ocean, to retrieve the surface wind speed. The dense space-time sampling capabilities, the ability of L-band signals to penetrate well through rain, and the possibility of simple, low-cost/low-power GNSS receivers, make GNSS-R ideal for the CYGNSS goals. Here we present an overview of a Level 2 (L2) wind speed retrieval algorithm, which would be particularly suitable for CYGNSS, and could be used to estimate winds from GNSS-R in general. The approach makes use of two different observables computed from 1-second Level 2a (L2a) delay-Doppler Maps (DDMs) of radar cross section. The first observable is called Delay-Doppler Map Average (DDMA), and it's the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second is called the Leading Edge Slope (LES), and it's the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of delays and Doppler frequencies, to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km x 25 km. If the observable from the 1-second DDM corresponds to a resolution higher than the specified one, time-averaging between

  18. Spatio-temporal modelling of wind speed variations and extremes in the Caribbean and the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Rychlik, Igor; Mao, Wengang

    2018-02-01

    The wind speed variability in the North Atlantic has been successfully modelled using a spatio-temporal transformed Gaussian field. However, this type of model does not correctly describe the extreme wind speeds attributed to tropical storms and hurricanes. In this study, the transformed Gaussian model is further developed to include the occurrence of severe storms. In this new model, random components are added to the transformed Gaussian field to model rare events with extreme wind speeds. The resulting random field is locally stationary and homogeneous. The localized dependence structure is described by time- and space-dependent parameters. The parameters have a natural physical interpretation. To exemplify its application, the model is fitted to the ECMWF ERA-Interim reanalysis data set. The model is applied to compute long-term wind speed distributions and return values, e.g., 100- or 1000-year extreme wind speeds, and to simulate random wind speed time series at a fixed location or spatio-temporal wind fields around that location.

  19. Influence of wind speed averaging on estimates of dimethylsulfide emission fluxes

    DOE PAGES

    Chapman, E. G.; Shaw, W. J.; Easter, R. C.; ...

    2002-12-03

    The effect of various wind-speed-averaging periods on calculated DMS emission fluxes is quantitatively assessed. Here, a global climate model and an emission flux module were run in stand-alone mode for a full year. Twenty-minute instantaneous surface wind speeds and related variables generated by the climate model were archived, and corresponding 1-hour-, 6-hour-, daily-, and monthly-averaged quantities calculated. These various time-averaged, model-derived quantities were used as inputs in the emission flux module, and DMS emissions were calculated using two expressions for the mass transfer velocity commonly used in atmospheric models. Results indicate that the time period selected for averaging wind speedsmore » can affect the magnitude of calculated DMS emission fluxes. A number of individual marine cells within the global grid show DMS emissions fluxes that are 10-60% higher when emissions are calculated using 20-minute instantaneous model time step winds rather than monthly-averaged wind speeds, and at some locations the differences exceed 200%. Many of these cells are located in the southern hemisphere where anthropogenic sulfur emissions are low and changes in oceanic DMS emissions may significantly affect calculated aerosol concentrations and aerosol radiative forcing.« less

  20. A statistical examination of Nimbus 7 SMMR data and remote sensing of sea surface temperature, liquid water content in the atmosphere and surfaces wind speed

    NASA Technical Reports Server (NTRS)

    Prabhakara, C.; Wang, I.; Chang, A. T. C.; Gloersen, P.

    1982-01-01

    Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) brightness temperature measurements over the global oceans have been examined with the help of statistical and empirical techniques. Such analyses show that zonal averages of brightness temperature measured by SMMR, over the oceans, on a large scale are primarily influenced by the water vapor in the atmosphere. Liquid water in the clouds and rain, which has a much smaller spatial and temporal scale, contributes substantially to the variability of the SMMR measurements within the latitudinal zones. The surface wind not only increases the surface emissivity but through its interactions with the atmosphere produces correlations, in the SMMR brightness temperature data, that have significant meteorological implications. It is found that a simple meteorological model can explain the general characteristics of the SMMR data. With the help of this model methods to infer over the global oceans, the surface temperature, liquid water content in the atmosphere, and surface wind speed are developed. Monthly mean estimates of the sea surface temperature and surface winds are compared with the ship measurements. Estimates of liquid water content in the atmosphere are consistent with earlier satellite measurements.

  1. Should future wind speed changes be taken into account in wind farm development?

    NASA Astrophysics Data System (ADS)

    Devis, Annemarie; Van Lipzig, Nicole P. M.; Demuzere, Matthias

    2018-06-01

    Accurate wind resource assessments are crucial in the development of wind farm projects. However, it is common practice to estimate the wind yield over the next 20 years from short-term measurements and reanalysis data of the past 20 years, even though wind climatology is expected to change under the future climate. The present work examines future changes in wind power output over Europe using an ensemble of ESMs. The power output is calculated using the entire wind speed PDF and a non-constant power conversion coefficient. Based on this method, the ESM ensemble projects changes in near-future power outputs with a spatially varying magnitude between ‑12% and 8%. The most extreme changes occur over the Mediterranean region. For the first time, the sensitivity of these future change in power output to the type of wind turbine is also investigated. The analysis reveals that the projected wind power changes may vary in up to half of their magnitude, depending on the type of turbine and region of interest. As such, we recommend that wind industries fully account for projected near-future changes in wind power output by taking them into account as a well-defined loss/gain and uncertainty when estimating the yield of a future wind farm.

  2. Why do modelled and observed surface wind stress climatologies differ in the trade wind regions?

    NASA Astrophysics Data System (ADS)

    Simpson, I.; Bacmeister, J. T.; Sandu, I.; Rodwell, M. J.

    2017-12-01

    Global climate models (GCMs) exhibit stronger easterly zonal surface wind stress and near surface winds in the Northern Hemisphere (NH) trade winds than observationally constrained reanalyses or other observational products. A comparison, between models and reanalyses, of the processes that contribute to the zonal mean, vertically integrated balance of momentum, reveals that this wind stress discrepancy cannot be explained by either the resolved dynamics or parameterized tendencies that are common to each. Rather, a substantial residual exists in the momentum balance of the reanalyses, pointing toward a role for the analysis increments. Indeed, they are found to systematically weaken the NH near surface easterlies in winter, thereby reducing the surface wind stress. Similar effects are found in the Southern Hemisphere and further analysis of the spatial structure and seasonality of these increments, demonstrates that they act to weaken the near surface flow over much of the low latitude oceans in both summer and winter. This suggests an erroneous /missing process in GCMs that constitutes a missing drag on the low level zonal flow over oceans. Either this indicates a mis-representation of the drag between the surface and the atmosphere, or a missing internal atmospheric process that amounts to an additional drag on the low level zonal flow. If the former is true, then observation based surface stress products, which rely on similar drag formulations to GCMs, may be underestimating the strength of the easterly surface wind stress.

  3. Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang

    2017-08-01

    This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.

  4. Wind speed variability over the Canary Islands, 1948-2014: focusing on trend differences at the land-ocean interface and below-above the trade-wind inversion layer

    NASA Astrophysics Data System (ADS)

    Azorin-Molina, Cesar; Menendez, Melisa; McVicar, Tim R.; Acevedo, Adrian; Vicente-Serrano, Sergio M.; Cuevas, Emilio; Minola, Lorenzo; Chen, Deliang

    2018-06-01

    This study simultaneously examines wind speed trends at the land-ocean interface, and below-above the trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of trade-winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981-2014), including one mountain weather station (Izaña) located above the trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948-2014; and SeaWind II at 15 km for 1989-2014). The results revealed a widespread significant negative trend of trade-winds over ocean for 1948-2014, whereas no significant trends were detected for 1989-2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter-spring-autumn; significant in April and September) of trade-winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.

  5. Vibration-based angular speed estimation for multi-stage wind turbine gearboxes

    NASA Astrophysics Data System (ADS)

    Peeters, Cédric; Leclère, Quentin; Antoni, Jérôme; Guillaume, Patrick; Helsen, Jan

    2017-05-01

    Most processing tools based on frequency analysis of vibration signals are only applicable for stationary speed regimes. Speed variation causes the spectral content to smear, which encumbers most conventional fault detection techniques. To solve the problem of non-stationary speed conditions, the instantaneous angular speed (IAS) is estimated. Wind turbine gearboxes however are typically multi-stage gearboxes, consisting of multiple shafts, rotating at different speeds. Fitting a sensor (e.g. a tachometer) to every single stage is not always feasible. As such there is a need to estimate the IAS of every single shaft based on the vibration signals measured by the accelerometers. This paper investigates the performance of the multi-order probabilistic approach for IAS estimation on experimental case studies of wind turbines. This method takes into account the meshing orders of the gears present in the system and has the advantage that a priori it is not necessary to associate harmonics with a certain periodic mechanical event, which increases the robustness of the method. It is found that the MOPA has the potential to easily outperform standard band-pass filtering techniques for speed estimation. More knowledge of the gearbox kinematics is beneficial for the MOPA performance, but even with very little knowledge about the meshing orders, the MOPA still performs sufficiently well to compete with the standard speed estimation techniques. This observation is proven on two different data sets, both originating from vibration measurements on the gearbox housing of a wind turbine.

  6. Efficacy of spatial averaging of infrasonic pressure in varying wind speeds.

    PubMed

    DeWolf, Scott; Walker, Kristoffer T; Zumberge, Mark A; Denis, Stephane

    2013-06-01

    Wind noise reduction (WNR) is important in the measurement of infrasound. Spatial averaging theory led to the development of rosette pipe arrays. The efficacy of rosettes decreases with increasing wind speed and only provides a maximum of ~20 dB WNR due to a maximum size limitation. An Optical Fiber Infrasound Sensor (OFIS) reduces wind noise by instantaneously averaging infrasound along the sensor's length. In this study two experiments quantify the WNR achieved by rosettes and OFISs of various sizes and configurations. Specifically, it is shown that the WNR for a circular OFIS 18 m in diameter is the same as a collocated 32-inlet pipe array of the same diameter. However, linear OFISs ranging in length from 30 to 270 m provide a WNR of up to ~30 dB in winds up to 5 m/s. The measured WNR is a logarithmic function of the OFIS length and depends on the orientation of the OFIS with respect to wind direction. OFISs oriented parallel to the wind direction achieve ~4 dB greater WNR than those oriented perpendicular to the wind. Analytical models for the rosette and OFIS are developed that predict the general observed relationships between wind noise reduction, frequency, and wind speed.

  7. Computational studies of horizontal axis wind turbines in high wind speed condition using advanced turbulence models

    NASA Astrophysics Data System (ADS)

    Benjanirat, Sarun

    Next generation horizontal-axis wind turbines (HAWTs) will operate at very high wind speeds. Existing engineering approaches for modeling the flow phenomena are based on blade element theory, and cannot adequately account for 3-D separated, unsteady flow effects. Therefore, researchers around the world are beginning to model these flows using first principles-based computational fluid dynamics (CFD) approaches. In this study, an existing first principles-based Navier-Stokes approach is being enhanced to model HAWTs at high wind speeds. The enhancements include improved grid topology, implicit time-marching algorithms, and advanced turbulence models. The advanced turbulence models include the Spalart-Allmaras one-equation model, k-epsilon, k-o and Shear Stress Transport (k-o-SST) models. These models are also integrated with detached eddy simulation (DES) models. Results are presented for a range of wind speeds, for a configuration termed National Renewable Energy Laboratory Phase VI rotor, tested at NASA Ames Research Center. Grid sensitivity studies are also presented. Additionally, effects of existing transition models on the predictions are assessed. Data presented include power/torque production, radial distribution of normal and tangential pressure forces, root bending moments, and surface pressure fields. Good agreement was obtained between the predictions and experiments for most of the conditions, particularly with the Spalart-Allmaras-DES model.

  8. Ship-borne measurements of aerosol optical depth over remote oceans and its dependence on wind speed

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P. L.; Quinn, P.; Sciare, J.; Gulev, S. K.; Piketh, S.; Losno, R.; Kinne, S. A.; Radionov, V. F.

    2011-12-01

    Aerosol production sources over the World Ocean and various factors determining aerosol spatial and temporal distribution are important for understanding the Earth's radiation budget and aerosol-cloud interactions. Sea-salt aerosol production, being a major source of aerosol over remote oceans, depends on surface wind speed. Recently in a number of publications the effect of wind speed on aerosol optical depth (AOD) has been presented utilizing coastal, island-based and satellite-based AOD measurements. However, the influence of wind speed on the columnar optical depth is still poorly understood, because not all factors and precursors influencing AOD dependence can be accounted for. The Maritime Aerosol Network (a component of AERONET) data archive provides an excellent opportunity to analyze in depth a relationship between ship-based AOD measurements and wind speed. We considered only data presumably not influenced by urban/industrial continental sources, dust outbreaks, biomass burning, or glaciers and pack ice. Additional restrictions imposed on the data set were acceptance of only points taken not closer than two degrees from the nearest landmass. We present analyses on the effect of surface (deck-level) wind speed (acquired onboard, modeled by NCEP, measured from satellite) on AOD and its spectral dependence. Latitudinal comparison of measured onboard and modeled wind speeds showed relatively small bias, which was higher at high latitudes. Instantaneous AOD measurements and daily means yielded similar relationships with various wind speed subsets (instantaneous ship-based and NCEP, averaged over previous 24 hours, steady, satellite retrieved). We compared regression statistics of optical parameters versus wind speed presented in various papers and based on various satellite and sunphotometer measurements. Overall, despite certain scatter, the current work and a majority of publications showed consistent patterns, with the AOD versus wind speed (range 2-16 m

  9. Solar Wind Speed Structure in the Inner Corona at 3-12 Ro

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1995-01-01

    Estimates of solar wind speed obtained by Armstrong et al. [1986] based on 1983 VLA multiple-station intensity scintillation measurements inside 12 R(sub o) have been correlated with the electron density structure observed in white-light coronagraph measurements. The observed large- scale and apparently systematic speed variations are found to depend primarily on changes in heliographic latitude and longitude, which leads to the first results on large-scale speed structure in the acceleration region of the solar wind. Over an equatorial hole, solar wind speed is relatively steady, with peak-to-peak variations of 50 km/s and an average of 230 km/s. In contrast, the near-Sun flow speed across the streamer belt shows regular large-scale variations in the range of 100-300 km/s. Based on four groups of data, the gradient is 36 km/s per degree in heliocentric coordinates (corresponding to a rise of 260 km/s over a spatial distance on the Sun of two arcmin) with a standard deviation of 2.4 km/s per degree. The lowest speeds most likely coincide with the stalks of coronal streamers observed in white-light measurements. The detection of significant wind shear over the streamer belt is consistent with in situ and scintillation measurements showing that the density spectrum has a power-law form characteristic of fully developed turbulence over a much broader range of scales than in neighboring regions.

  10. Gust wind tunnel study on ballast pick-up by high-speed trains

    NASA Astrophysics Data System (ADS)

    Navarro-Medina, F.; Sanz-Andres, A.; Perez-Grande, I.

    2012-01-01

    This paper describes the experimental setup, procedure, and results obtained, concerning the dynamics of a body lying on a floor, attached to a hinge, and exposed to an unsteady flow, which is a model of the initiation of rotational motion of ballast stones due to the wind generated by the passing of a high-speed train. The idea is to obtain experimental data to support the theoretical model developed in Sanz-Andres and Navarro-Medina (J Wind Eng Ind Aerodyn 98, 772-783, (2010), aimed at analyzing the initial phase of the ballast train-induced-wind erosion (BATIWE) phenomenon. The experimental setup is based on an open circuit, closed test section, low-speed wind tunnel, with a new sinusoidal gust generator mechanism concept, designed and built at the IDR/UPM. The tunnel's main characteristic is the ability to generate a flow with a uniform velocity profile and sinusoidal time fluctuation of the speed. Experimental results and theoretical model predictions are in good agreement.

  11. Observed variability in the upper layers at the Equator, 90°E in the Indian Ocean during 2001-2008, 1: zonal currents

    NASA Astrophysics Data System (ADS)

    Rao, R. R.; Horii, T.; Masumoto, Y.; Mizuno, K.

    2017-08-01

    The observed variability of zonal currents (ZC) at the Equator, 90°E shows a strong seasonal cycle in the near-surface 40-350 m water column with periodic east-west reversals most pronounced at semiannual frequency. Superposed on this, a strong intraseasonal variability of 30-90 day periodicity is also prominently seen in the near-surface layer (40-80 m) almost throughout the year with the only exception of February-March. An eastward flowing equatorial undercurrent (EUC) is present in the depth range of 80-160 m during March-April and October-November. The observed intraseasonal variability in the near-surface layer is primarily determined by the equatorial zonal westerly wind bursts (WWBs) through local frictional coupling between the zonal flow in the surface layer and surface zonal winds and shows large interannual variability. The eastward flowing EUC maintained by the ZPG set up by the east-west slope of the thermocline remotely controlled by the zonal wind (ZW) and zonally propagating wave fields also shows significant interannual variability. This observed variability on interannual time scales appears to be controlled by the corresponding variability in the alongshore winds off the Somalia coast during the preceding boreal winter, the ZW field along the equator, and the associated zonally propagating Kelvin and Rossby waves. The salinity induced vertical stratification observed in the near-surface layer through barrier layer thickness (BLT) effects also shows a significant influence on the ZC field on intraseasonal time scale. Interestingly, among all the 8 years (2001-2008), relatively weaker annual cycle is seen in both ZC in the 40-350 m water column and boreal spring sea surface temperature (SST) only during 2001 and 2008 along the equator caused through propagating wave dynamics.

  12. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr Inlet...

  13. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr Inlet...

  14. 40 CFR Table F-2 to Subpart F of... - Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test F Table F-2 to Subpart F... Part 53—Particle Sizes and Wind Speeds for Full Wind Tunnel Test, Wind Tunnel Inlet Aspiration Test, and Static Chamber Test Primary Partical Mean Size a (µm) Full Wind Tunnel Test 2 km/hr 24 km/hr Inlet...

  15. Equatorial Winds on Saturn and the Stratospheric Oscillation

    NASA Technical Reports Server (NTRS)

    Li, Liming; Jian, Xun; Ingersoll, Andrew P.; DelGenio, Anthony D.; Porco, Carolyn C.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.; Conrath, Barney J.; Gierasch, Peter J.; hide

    2011-01-01

    The zonal jets on the giant planets are generally thought to be stable with time. Recently, there are still some debates about the general thought. Here, we report a significant temporal variation of the equatorial jet at high-altitude on Saturn. Long-term (2004-2009) observations by Cassini reveal that wind speed at the 60-mbar level increased from 270 m/s in 2004 to 290 m/s in 2008, while the wind speed has been mostly constant over time at the 500-mbar level in the southern equatorial region. The Cassini observations further reveal that the equatorial jet intensified approximately 60 m/s in the stratosphere (1-5 mbar) from 2005 to 2008. The fact that the wind acceleration is weaker at the 60-mbar level (approximately 20 m/s) than at the 1-mbar level (approximately 60 m/s) demonstrates that the equatorial oscillation is damped when it propagates downwards to the tropopause around 60 mbar. The direct measurement of the varying equatorial jet around the tropopause also serves as a key boundary condition when deriving the thermal wind fields in the stratosphere.

  16. Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

    Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and strongermore » entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ≳50 gm –2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. Here, we find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from

  17. Wind speed response of marine non-precipitating stratocumulus clouds over a diurnal cycle in cloud-system resolving simulations

    DOE PAGES

    Kazil, Jan; Feingold, Graham; Yamaguchi, Takanobu

    2016-05-12

    Observed and projected trends in large-scale wind speed over the oceans prompt the question: how do marine stratocumulus clouds and their radiative properties respond to changes in large-scale wind speed? Wind speed drives the surface fluxes of sensible heat, moisture, and momentum and thereby acts on cloud liquid water path (LWP) and cloud radiative properties. We present an investigation of the dynamical response of non-precipitating, overcast marine stratocumulus clouds to different wind speeds over the course of a diurnal cycle, all else equal. In cloud-system resolving simulations, we find that higher wind speed leads to faster boundary layer growth and strongermore » entrainment. The dynamical driver is enhanced buoyant production of turbulence kinetic energy (TKE) from latent heat release in cloud updrafts. LWP is enhanced during the night and in the morning at higher wind speed, and more strongly suppressed later in the day. Wind speed hence accentuates the diurnal LWP cycle by expanding the morning–afternoon contrast. The higher LWP at higher wind speed does not, however, enhance cloud top cooling because in clouds with LWP ≳50 gm –2, longwave emissions are insensitive to LWP. This leads to the general conclusion that in sufficiently thick stratocumulus clouds, additional boundary layer growth and entrainment due to a boundary layer moistening arises by stronger production of TKE from latent heat release in cloud updrafts, rather than from enhanced longwave cooling. Here, we find that large-scale wind modulates boundary layer decoupling. At nighttime and at low wind speed during daytime, it enhances decoupling in part by faster boundary layer growth and stronger entrainment and in part because shear from large-scale wind in the sub-cloud layer hinders vertical moisture transport between the surface and cloud base. With increasing wind speed, however, in decoupled daytime conditions, shear-driven circulation due to large-scale wind takes over from

  18. Dependence of the Normalized Radar Cross Section of Water Waves on Bragg Wavelength-Wind Speed Sensitivity

    NASA Technical Reports Server (NTRS)

    Long, David G.; Collyer, R. Scott; Reed, Ryan; Arnold, David V.

    1996-01-01

    Measurements of the normalized radar cross section (sigma(sup o)) made by the YSCAT ultrawideband scatterometer during an extended deployment on the Canada Centre for Inland Waters(CCIW) Research Tower located at Lake Ontario are analyzed and compared with anemometer wind measurements to study the sensitivity of (sigma(sup o)) to the wind speed as a function of the Bragg wavelength. This paper concentrates on upwind and downwind azimuth angles in the wind speed range of 4.5-12 m/s. While YSCAT collected measurements of sigma(sup o) at a variety of frequencies and incidence angles, this paper focuses on frequencies of 2.0, 3.05, 5.30, 10.02, and 14.0 GHz and incidence angles within the Bragg regime, 30-50 deg. Adopting a power law model to describe the relationship between sigma(sup o) and wind speed, both wind speed exponents and upwind/downwind (u/d) ratios of sigma(sup o) are found using least squares linear regression. The analysis of the wind speed exponents and u/d ratios show that shorter Bragg wavelengths (Lambda less than 4 cm) are the most sensitive to wind speed and direction. Additionally, vertical polarization (V-pol) sigma(sup o) is shown to be more sensitive to wind speed than horizontal polarization (H-pol) sigma(sup o), while the H-pol u/d ratio is larger than the V-pol u/d ratio.

  19. Homogenization of Tianjin monthly near-surface wind speed using RHtestsV4 for 1951-2014

    NASA Astrophysics Data System (ADS)

    Si, Peng; Luo, Chuanjun; Liang, Dongpo

    2018-05-01

    Historical Chinese surface meteorological records provided by the special fund for basic meteorological data from the National Meteorological Information Center (NMIC) were processed to produce accurate wind speed data. Monthly 2-min near-surface wind speeds from 13 observation stations in Tianjin covering 1951-2014 were homogenized using RHtestV4 combined with their metadata. Results indicate that 10 stations had significant breakpoints—77% of the Tianjin stations—suggesting that inhomogeneity was common in the Tianjin wind speed series. Instrument change accounted for most changes, based on the metadata, including changes in type and height, especially for the instrument type. Average positive quantile matching (QM) adjustments were more than negative adjustments at 10 stations; positive biases with a probability density of 0.2 or more were mainly concentrates in the range 0.2 m s-1 to 1.2 m s-1, while the corresponding negative biases were mainly in the range -0.1 to -1.2 m s-1. Here, changes in variances and trends in the monthly mean surface wind speed series at 10 stations before and after adjustment were compared. Climate characteristics of wind speed in Tianjin were more reasonably reflected by the adjusted data; inhomogeneity in wind speed series was largely corrected. Moreover, error analysis reveals that there was a high consistency between the two datasets here and that from the NMIC, with the latter as the reference. The adjusted monthly near-surface wind speed series shows a certain reliability for the period 1951-2014 in Tianjin.

  20. Ensemble Nonlinear Autoregressive Exogenous Artificial Neural Networks for Short-Term Wind Speed and Power Forecasting.

    PubMed

    Men, Zhongxian; Yee, Eugene; Lien, Fue-Sang; Yang, Zhiling; Liu, Yongqian

    2014-01-01

    Short-term wind speed and wind power forecasts (for a 72 h period) are obtained using a nonlinear autoregressive exogenous artificial neural network (ANN) methodology which incorporates either numerical weather prediction or high-resolution computational fluid dynamics wind field information as an exogenous input. An ensemble approach is used to combine the predictions from many candidate ANNs in order to provide improved forecasts for wind speed and power, along with the associated uncertainties in these forecasts. More specifically, the ensemble ANN is used to quantify the uncertainties arising from the network weight initialization and from the unknown structure of the ANN. All members forming the ensemble of neural networks were trained using an efficient particle swarm optimization algorithm. The results of the proposed methodology are validated using wind speed and wind power data obtained from an operational wind farm located in Northern China. The assessment demonstrates that this methodology for wind speed and power forecasting generally provides an improvement in predictive skills when compared to the practice of using an "optimal" weight vector from a single ANN while providing additional information in the form of prediction uncertainty bounds.

  1. Ensemble Nonlinear Autoregressive Exogenous Artificial Neural Networks for Short-Term Wind Speed and Power Forecasting

    PubMed Central

    Lien, Fue-Sang; Yang, Zhiling; Liu, Yongqian

    2014-01-01

    Short-term wind speed and wind power forecasts (for a 72 h period) are obtained using a nonlinear autoregressive exogenous artificial neural network (ANN) methodology which incorporates either numerical weather prediction or high-resolution computational fluid dynamics wind field information as an exogenous input. An ensemble approach is used to combine the predictions from many candidate ANNs in order to provide improved forecasts for wind speed and power, along with the associated uncertainties in these forecasts. More specifically, the ensemble ANN is used to quantify the uncertainties arising from the network weight initialization and from the unknown structure of the ANN. All members forming the ensemble of neural networks were trained using an efficient particle swarm optimization algorithm. The results of the proposed methodology are validated using wind speed and wind power data obtained from an operational wind farm located in Northern China. The assessment demonstrates that this methodology for wind speed and power forecasting generally provides an improvement in predictive skills when compared to the practice of using an “optimal” weight vector from a single ANN while providing additional information in the form of prediction uncertainty bounds. PMID:27382627

  2. Contraction design for small low-speed wind tunnels

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1988-01-01

    An iterative design procedure was developed for two- or three-dimensional contractions installed on small, low-speed wind tunnels. The procedure consists of first computing the potential flow field and hence the pressure distributions along the walls of a contraction of given size and shape using a three-dimensional numerical panel method. The pressure or velocity distributions are then fed into two-dimensional boundary layer codes to predict the behavior of the boundary layers along the walls. For small, low-speed contractions it is shown that the assumption of a laminar boundary layer originating from stagnation conditions at the contraction entry and remaining laminar throughout passage through the successful designs if justified. This hypothesis was confirmed by comparing the predicted boundary layer data at the contraction exit with measured data in existing wind tunnels. The measured boundary layer momentum thicknesses at the exit of four existing contractions, two of which were 3-D, were found to lie within 10 percent of the predicted values, with the predicted values generally lower. From the contraction wall shapes investigated, the one based on a fifth-order polynomial was selected for installation on a newly designed mixing layer wind tunnel.

  3. Contraction design for small low-speed wind tunnels

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1988-01-01

    An iterative design procedure was developed for 2- or 3-dimensional contractions installed on small, low speed wind tunnels. The procedure consists of first computing the potential flow field and hence the pressure distributions along the walls of a contraction of given size and shape using a 3-dimensional numerical panel method. The pressure or velocity distributions are then fed into 2-dimensional boundary layer codes to predict the behavior of the boundary layers along the walls. For small, low speed contractions, it is shown that the assumption of a laminar boundary layer originating from stagnation conditions at the contraction entry and remaining laminar throughout passage through the successful designs is justified. This hypothesis was confirmed by comparing the predicted boundary layer data at the contraction exit with measured data in existing wind tunnels. The measured boundary layer momentum thicknesses at the exit of four existing contractions, two of which were 3-D, were found to lie within 10 percent of the predicted values, with the predicted values generally lower. From the contraction wall shapes investigated, the one based on a 5th order polynomial was selected for newly designed mixing wind tunnel installation.

  4. Zonally averaged model of dynamics, chemistry and radiation for the atmosphere

    NASA Technical Reports Server (NTRS)

    Tung, K. K.

    1985-01-01

    A nongeostrophic theory of zonally averaged circulation is formulated using the nonlinear primitive equations on a sphere, taking advantage of the more direct relationship between the mean meridional circulation and diabatic heating rate which is available in isentropic coordinates. Possible differences between results of nongeostrophic theory and the commonly used geostrophic formulation are discussed concerning: (1) the role of eddy forcing of the diabatic circulation, and (2) the nonlinear nearly inviscid limit vs the geostrophic limit. Problems associated with the traditional Rossby number scaling in quasi-geostrophic formulations are pointed out and an alternate, more general scaling based on the smallness of mean meridional to zonal velocities for a rotating planet is suggested. Such a scaling recovers the geostrophic balanced wind relationship for the mean zonal flow but reveals that the mean meridional velocity is in general ageostrophic.

  5. Comparative study of chaotic features in hourly wind speed using recurrence quantification analysis

    NASA Astrophysics Data System (ADS)

    Adeniji, A. E.; Olusola, O. I.; Njah, A. N.

    2018-02-01

    Due to the shortage in electricity supply in Nigeria, there is a need to improve the alternative power generation from wind energy by analysing the wind speed data available in some parts of the country, for a better understanding of its underlying dynamics for the purpose of good prediction and modelling. The wind speed data used in this study were collected over a period of two years by National Space Research and Development Agency (NASRDA) from five different stations in the tropics namely; Abuja (7050'02.09"N and 6004'29.97"E), Akungba (6059'05.40"N and 5035'52.23"E), Nsukka (6051'28.14"N and 7024'28.15"E), Port Harcourt (4047'05.41"N and 6059'30.62"E), and Yola (9017'33.58"N and 12023'26.69"E). In this paper, recurrence plot (RP) and recurrence quantification analysis (RQA) are applied to investigate a non-linear deterministic dynamical process and non-stationarity in hourly wind speed data from the study areas. Using RQA for each month of the two years, it is observed that wind speed data for the wet months exhibit higher chaoticity than that of the dry months for all the stations, due to strong and weak monsoonal effect during the wet and dry seasons respectively. The results show that recurrence techniques are able to identify areas and periods for which the harvest of wind energy for power generation is good (high predictability) and poor (low predictability) in the study areas. This work also validates the RQA measures (Lmax, DET and ENT) used and establishes that they are similar/related as they give similar results for the dynamical characterization of the wind speed data.

  6. The Role of Reversed Equatorial Zonal Transport in Terminating an ENSO Event

    NASA Astrophysics Data System (ADS)

    Chen, H. C.; Hu, Z. Z.; Huang, B.; Sui, C. H.

    2016-02-01

    In this study, we demonstrate that a sudden reversal of anomalous equatorial zonal current at the peaking ENSO phase triggers the rapid termination of an ENSO event. Throughout an ENSO cycle, the anomalous equatorial zonal current is strongly controlled by the concavity of the anomalous thermocline meridional structure near the equator. During the ENSO developing phase, the anomalous zonal current in the central and eastern Pacific generally enhances the ENSO growth through its zonal SST advection. In the mature phase of ENSO, however, the equatorial thermocline depth anomalies are reflected in the eastern Pacific and slowly propagate westward off the equator in both hemispheres. As a result, the concavity of the thermocline anomalies near the equator is reversed, i.e., the off-equatorial thermocline depth anomalies become higher than that on the equator for El Niño events and lower for La Niño events. This meridional change of thermocline structure reverses zonal transport rapidly in the central-to-eastern equatorial Pacific, which weakens the ENSO SST anomalies by reversed advection. More importantly, the reversed zonal mass transport weakens the existing zonal tilting of equatorial thermocline and suppresses the thermocline feedback. Both processes are concentrated in the eastern equatorial Pacific and can be effective on subseasonal time scales. These current reversal effects are built-in to the ENSO peak phase and independent of the zonal wind effect on thermocline slope. It functions as an oceanic control on ENSO evolution during both El Niño and La Niña events.

  7. The Radial Variation of the Solar Wind Temperature-Speed Relationship

    NASA Astrophysics Data System (ADS)

    Elliott, H. A.; McComas, D. J.

    2010-12-01

    Generally, the solar wind temperature (T) and speed (V) are well correlated except in Interplanetary Coronal Mass Ejections where this correlation breaks down. We have shown that at 1 AU the speed-temperature relationship is often well represented by a linear fit for a speed range spanning both the slow and fast wind. By examining all of the ACE and OMNI measurements, we found that when coronal holes are large the fast wind can have a different T-V relationship than the slow wind. The best example of this was in 2003 when there was a very large and long-lived outward polarity coronal hole at low latitudes. The long-lived nature of the hole made it possible to clearly distinguish that large holes can have a different T-V relationship. We found it to be rare that holes are large enough and last long enough to have enough data points to clearly demonstrate this effect. In this study we compare the 2003 coronal hole observations from ACE with the Ulysses polar coronal hole measurements. In an even earlier ACE study we found that both the compressions and rarefactions curves are linear, but the compression curve is shifted to higher temperatures. In this presentation we use Helios, Ulysses, and ACE measurements to examine how the T-V relationship varies with distance. The dynamic evolution of the solar wind parameters is revealed when we first separate compressions and rarefactions and then determine the radial profiles of the solar wind parameters. We find that T-V relationship varies with distance and in particular beyond 3 AU the differences between the compressions and rarefactions are quite important and at such distances a simple linear fit does not represent the T-V distribution very well.

  8. Drag Corrections in High-Speed Wind Tunnels

    NASA Technical Reports Server (NTRS)

    Ludwieg, H.

    1947-01-01

    In the vicinity of a body in a wind tunnel the displacement effect of the wake, due to the finite dimensions of the stream, produces a pressure gradient which evokes a change of drag. In incompressible flow this change of drag is so small, in general, that one does not have to take it into account in wind-tunnel measurements; however, in compressible flow it beoomes considerably larger, so that a correction factor is necessary for measured values. Correction factors for a closed tunnel and an open jet with circular cross sections are calculated and compared with the drag - corrections already bown for high-speed tunnnels.

  9. Air/sea DMS gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-05-01

    Shipboard measurements of eddy covariance DMS air/sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air/sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near surface water side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air/sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  10. Observations of Martian surface winds at the Viking Lander 1 site

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Murphy, J.R.; Leovy, C.B.; Tillman, J.E.

    1990-08-30

    Partial failure of the wind instrumentation on the Viking Lander 1 (VL1) in the Martian subtropics (22.5{degree}N) has limited previous analyses of meteorological data for this site. The authors describe a method for reconstructing surface winds using data from the partially failed sensor and present and analyze a time series of wind, pressure, and temperature at the site covering 350 Mars days (sols). At the beginning of the mission during early summer, winds were controlled by regional topography, but they soon underwent a transition to a regime controlled by the Hadley circulation. Diurnal and semidiurnal wind oscillations and synoptic variationsmore » have been analyzed and compared with the corresponding variations at the Viking Lander 2 middle latitude site (48{degree}N). Diurnal wind oscillations were controlled primarily by regional topography and boundary layer forcing, although a global mode may have been influencing them during two brief episodes. Semidiurnal wind oscillations were controlled by the westward propagating semidiurnal tide from sol 210 onward. Comparison of the synoptic variations at the two sites suggests that the same eastward propagating wave trains were present at both sites, at least following the first 1977 great dust storm, but discordant inferred zonal wave numbers and phase speeds at the two sites cast doubt on the zonal wave numbers deduced from analyses of combined wind and pressure data, particularly at the VL1 site where the signal to noise ratio of the dominant synoptic waves is relatively small.« less

  11. Wind structure and small-scale wind variability in the stratosphere and mesosphere during the November 1980 Energy Budget Campaign

    NASA Technical Reports Server (NTRS)

    Schmidlin, F. J.; Carlson, M.; Rees, D.; Offermann, D.; Philbrick, C. R.; Widdel, H. U.

    1982-01-01

    Rocket observations made from two sites in northern Scandinavia between November 6 and December 1, 1980, as part of the Energy Budget Campaign are discussed. It was found that significant vertical and temporal changes in the wind structure were present and that they coincided with different geomagnetic conditions, that is, quiet and enhanced. Before November 16, the meridional wind component above 60 km was found to be positive (southerly), whereas the magnitude of the zonal wind component increased with altitude. After November 16 the meridional component became negative (northerly), and the magnitude of the zonal wind component was observed to decrease with altitude. Time sections of the perturbations of the zonal wind reveal the presence of vertically propagating waves, suggesting gravity wave activity. The waves are found to increase in wavelength from 3-4 km near 40 km to more than 12 km near 80 km. The observational techniques made use of chaff foil, chemical trails, inflatable spheres, and parachutes.

  12. Examples of the Influence of Turbine Wakes on Downwind Power Output, Surface Wind Speed, Turbulence and Flow Convergence in Large Wind Farms

    NASA Astrophysics Data System (ADS)

    Takle, E. S.; Rajewski, D. A.; Lundquist, J. K.; Doorenbos, R. K.

    2014-12-01

    We have analyzed turbine power and concurrent wind speed, direction and turbulence data from surface 10-m flux towers in a large wind farm for experiments during four summer periods as part of the Crop Wind Energy Experiment (CWEX). We use these data to analyze surface differences for a near-wake (within 2.5 D of the turbine line), far wake (17 D downwind of the turbine line), and double wake (impacted by two lines of turbines about 34 D downwind of the first turbine line) locations. Composites are categorized by10 degree directional intervals and three ambient stability categories as defined by Rajewski et al. (2013): neutral (|z/L|<0.05), stable (z/L>0.05) and unstable (z/L<-0.05), where z is the height of the measurement and L is the Monin-Obhukov length. The dominant influence of the turbines is under stably stratified conditions (i. e., mostly at night). A 25% to 40% increase in mean wind speed occurs when turbine wakes are moving over the downwind station at a distance of 2.8 D and 5.4 D (D = fan diameter). For the double wake condition (flux station leeward of two lines of turbines) we find a daytime (unstable conditions) speed reduction of 20% for southerly wind, but for nighttime (stable conditions) the surface speeds are enhancedby 40-60% for SSW-SW winds. The speedup is reduced as wind directions shift to the west. We interpret these speed variations as due to the rotation of the wake and interaction (or not) with higher speed air above the rotor layer in highly sheared nocturnal low-level jet conditions. From a cluster of flux stations and three profiling lidars deployed within and around a cluster of turbines in 2013 (CWEX-13) we found evidence of mesoscale influences. In particular, surface convergence (wind direction deflection of 10-20 degrees) was observed during periods of low nighttime winds (hub-height winds of 4-6 m/s) with power reduction of 50-75%. This is consistent with a similar range of deflection observed from a line of turbines in CWEX

  13. High Resolution Wind Direction and Speed Information for Support of Fire Operations

    Treesearch

    B.W. Butler; J.M. Forthofer; M.A. Finney; L.S. Bradshaw; R. Stratton

    2006-01-01

    Computational Fluid Dynamics (CFD) technology has been used to model wind speed and direction in mountainous terrain at a relatively high resolution compared to other readily available technologies. The process termed “gridded wind” is not a forecast, but rather represents a method for calculating the influence of terrain on general wind flows. Gridded wind simulations...

  14. Control strategy for a variable-speed wind energy conversion system

    NASA Technical Reports Server (NTRS)

    Jacob, A.; Veillette, D.; Rajagopalan, V.

    1979-01-01

    A control concept for a variable-speed wind energy conversion system is proposed, for which a self-exited asynchronous cage generator is used along with a system of thyristor converters. The control loops are the following: (1) regulation of the entrainment speed as function of available mechanical energy by acting on the resistance couple of the asynchronous generator; (2) control of electric power delivered to the asynchronous machine, functioning as a motor, for start-up of the vertical axis wind converter; and (3) limitation of the slip value, and by consequence, of the induction currents in the presence of sudden variations of input parameters.

  15. Seasonality, interannual variability, and linear tendency of wind speeds in the northeast Brazil from 1986 to 2011.

    PubMed

    Torres Silva dos Santos, Alexandre; Moisés Santos e Silva, Cláudio

    2013-01-01

    Wind speed analyses are currently being employed in several fields, especially in wind power generation. In this study, we used wind speed data from records of Universal Fuess anemographs at an altitude of 10 m from 47 weather stations of the National Institute of Meteorology (Instituto Nacional de Meteorologia-INMET) from January 1986 to December 2011. The objective of the study was to investigate climatological aspects and wind speed trends. To this end, the following methods were used: filling of missing data, descriptive statistical calculations, boxplots, cluster analysis, and trend analysis using the Mann-Kendall statistical method. The seasonal variability of the average wind speeds of each group presented higher values for winter and spring and lower values in the summer and fall. The groups G1, G2, and G5 showed higher annual averages in the interannual variability of wind speeds. These observed peaks were attributed to the El Niño and La Niña events, which change the behavior of global wind circulation and influence wind speeds over the region. Trend analysis showed more significant negative values for the G3, G4, and G5 groups for all seasons of the year and in the annual average for the period under study.

  16. Seasonality, Interannual Variability, and Linear Tendency of Wind Speeds in the Northeast Brazil from 1986 to 2011

    PubMed Central

    Santos e Silva, Cláudio Moisés

    2013-01-01

    Wind speed analyses are currently being employed in several fields, especially in wind power generation. In this study, we used wind speed data from records of Universal Fuess anemographs at an altitude of 10 m from 47 weather stations of the National Institute of Meteorology (Instituto Nacional de Meteorologia-INMET) from January 1986 to December 2011. The objective of the study was to investigate climatological aspects and wind speed trends. To this end, the following methods were used: filling of missing data, descriptive statistical calculations, boxplots, cluster analysis, and trend analysis using the Mann-Kendall statistical method. The seasonal variability of the average wind speeds of each group presented higher values for winter and spring and lower values in the summer and fall. The groups G1, G2, and G5 showed higher annual averages in the interannual variability of wind speeds. These observed peaks were attributed to the El Niño and La Niña events, which change the behavior of global wind circulation and influence wind speeds over the region. Trend analysis showed more significant negative values for the G3, G4, and G5 groups for all seasons of the year and in the annual average for the period under study. PMID:24250267

  17. Wind speed and power characteristics of Kalasin province, Thailand

    NASA Astrophysics Data System (ADS)

    Polnumtiang, Supachai; Tangchaichit, Kiatfa

    2018-05-01

    This paper presents a wind energy assessment of Kalasin province in the Upper North-Eastern region of Thailand. Four year wind data were recorded continuously from January 2012 to December 2015 at different heights of 60, 90 and 120 m above ground level (AGL). The mean wind speeds were found to be 3.14, 3.63 and 3.94 m/s at 60, 90 and 120 m AGL, respectively. The majority of wind directions for this region are distributed from the East to South directions. The highest wind power density was observed in the summer season, followed by winter and rainy seasons, in order. Four commercial wind turbines were selected to estimate energy yield output using the WAsP 10.0 software application; the results show that VESTAS with rated power of 2.0 MW was estimated to give 2,747 MWh/year with the highest capacity factor of 15.68%.

  18. Power Maximization Control of Variable Speed Wind Generation System Using Permanent Magnet Synchronous Generator

    NASA Astrophysics Data System (ADS)

    Morimoto, Shigeo; Nakamura, Tomohiko; Takeda, Yoji

    This paper proposes the sensorless output power maximization control of the wind generation system. A permanent magnet synchronous generator (PMSG) is used as a variable speed generator in the proposed system. The generator torque is suitably controlled according to the generator speed and thus the power from a wind turbine settles down on the maximum power point by the proposed MPPT control method, where the information of wind velocity is not required. Moreover, the maximum available generated power is obtained by the optimum current vector control. The current vector of PMSG is optimally controlled according to the generator speed and the required torque in order to minimize the losses of PMSG considering the voltage and current constraints. The proposed wind power generation system can be achieved without mechanical sensors such as a wind velocity detector and a position sensor. Several experimental results show the effectiveness of the proposed control method.

  19. Development of Wind Speed Retrieval from Cross-Polarization Chinese Gaofen-3 Synthetic Aperture Radar in Typhoons

    PubMed Central

    Yuan, Xinzhe; Sun, Jian; Zhou, Wei; Zhang, Qingjun

    2018-01-01

    The purpose of our work is to determine the feasibility and effectiveness of retrieving sea surface wind speeds from C-band cross-polarization (herein vertical-horizontal, VH) Chinese Gaofen-3 (GF-3) SAR images in typhoons. In this study, we have collected three GF-3 SAR images acquired in Global Observation (GLO) and Wide ScanSAR (WSC) mode during the summer of 2017 from the China Sea, which includes the typhoons Noru, Doksuri and Talim. These images were collocated with wind simulations at 0.12° grids from a numeric model, called the Regional Assimilation and Prediction System-Typhoon model (GRAPES-TYM). Recent research shows that GRAPES-TYM has a good performance for typhoon simulation in the China Sea. Based on the dataset, the dependence of wind speed and of radar incidence angle on normalized radar cross (NRCS) of VH-polarization GF-3 SAR have been investigated, after which an empirical algorithm for wind speed retrieval from VH-polarization GF-3 SAR was tuned. An additional four VH-polarization GF-3 SAR images in three typhoons, Noru, Hato and Talim, were investigated in order to validate the proposed algorithm. SAR-derived winds were compared with measurements from Windsat winds at 0.25° grids with wind speeds up to 40 m/s, showing a 5.5 m/s root mean square error (RMSE) of wind speed and an improved RMSE of 5.1 m/s wind speed was achieved compared with the retrieval results validated against GRAPES-TYM winds. It is concluded that the proposed algorithm is a promising potential technique for strong wind retrieval from cross-polarization GF-3 SAR images without encountering a signal saturation problem. PMID:29385068

  20. Temporal and spatial variation of maximum wind speed days during the past 20 years in major cities of Xinjiang

    NASA Astrophysics Data System (ADS)

    Baidourela, Aliya; Jing, Zhen; Zhayimu, Kahaer; Abulaiti, Adili; Ubuli, Hakezi

    2018-04-01

    Wind erosion and sandstorms occur in the neighborhood of exposed dust sources. Wind erosion and desertification increase the frequency of dust storms, deteriorate air quality, and damage the ecological environment and agricultural production. The Xinjiang region has a relatively fragile ecological environment. Therefore, the study of the characteristics of maximum wind speed and wind direction in this region is of great significance to disaster prevention and mitigation, the management of activated dunes, and the sustainable development of the region. Based on the latest data of 71 sites in Xinjiang, this study explores the temporal evolution and spatial distribution of maximum wind speed in Xinjiang from 1993 to 2013, and highlights the distribution of annual and monthly maximum wind speed and the characteristics of wind direction in Xinjiang. Between 1993 and 2013, Ulugchat County exhibited the highest number of days with the maximum wind speed (> 17 m/s), while Wutian exhibited the lowest number. In Xinjiang, 1999 showed the highest number of maximum wind speed days (257 days), while 2013 showed the lowest number (69 days). Spring and summer wind speeds were greater than those in autumn and winter. There were obvious differences in the direction of maximum wind speed in major cities and counties of Xinjiang. East of the Tianshan Mountains, maximum wind speeds are mainly directed southeast and northeast. North and south of the Tianshan Mountains, they are mainly directed northwest and northeast, while west of the Tianshan Mountains, they are mainly directed southeast and northwest.

  1. Solar-QBO Interaction and Its Impact on Stratospheric Ozone in a Zonally Averaged Photochemical Transport Model of the Middle Atmosphere

    DTIC Science & Technology

    2007-08-28

    Solar- QBO interaction and its impact on stratospheric ozone in a zonally averaged photochemical transport model of the middle atmosphere J. P...investigate the solar cycle modulation of the quasi-biennial oscillation ( QBO ) in stratospheric zonal winds and its impact on stratospheric ozone with an...updated version of the zonally averaged CHEM2D middle atmosphere model. We find that the duration of the westerly QBO phase at solar maximum is 3 months

  2. Intercomparison of wind speeds inferred by the SASS, altimeter, and SMMR

    NASA Technical Reports Server (NTRS)

    Wentz, F. J.; Cardone, V. J.; Fedor, L. S.

    1982-01-01

    The operational theory, control algorithms, and comparisons with surface-determined wind speeds for the scatterometer (SASS), altimeter (ALT), and passive microwave radiometer (SMMR) on board the Seasat satellite are presented. Radiative scattering combining specular reflections and Bragg resonance scattering are noted to occur at tilting waves and sea foam, two conditions highly correlated with wind speed. SASS scans swaths of 70, 200, and 700 km from nadir, the SMMR covers a 150 km strip. Normalized radar sections are derived from the SASS and ALT telemetry, and brightness temperature from the SMMR. ALT winds were found to be biased about 3 m/sec low, while intercomparison between the SMMR and SASS data showed a mean difference of 0.3 m/sec with a standard deviation from measured winds of 1.7 m/sec or less. The effects of land thermal emissions, rain, and sun glint are discussed, and good viewing conditions are concluded to result in 2 m/sec accuracy.

  3. Solar Wind Helium Abundance as a Function of Speed and Heliographic Latitude: Variation through a Solar Cycle

    NASA Technical Reports Server (NTRS)

    Kasper, J. C.; Stenens, M. L.; Stevens, M. L.; Lazarus, A. J.; Steinberg, J. T.; Ogilvie, Keith W.

    2006-01-01

    We present a study of the variation of the relative abundance of helium to hydrogen in the solar wind as a function of solar wind speed and heliographic latitude over the previous solar cycle. The average values of A(sub He), the ratio of helium to hydrogen number densities, are calculated in 25 speed intervals over 27-day Carrington rotations using Faraday Cup observations from the Wind spacecraft between 1995 and 2005. The higher speed and time resolution of this study compared to an earlier work with the Wind observations has led to the discovery of three new aspects of A(sub He), modulation during solar minimum from mid-1995 to mid-1997. First, we find that for solar wind speeds between 350 and 415 km/s, A(sub He), varies with a clear six-month periodicity, with a minimum value at the heliographic equatorial plane and a typical gradient of 0.01 per degree in latitude. For the slow wind this is a 30% effect. We suggest that the latitudinal gradient may be due to an additional dependence of coronal proton flux on coronal field strength or the stability of coronal loops. Second, once the gradient is subtracted, we find that A(sub He), is a remarkably linear function of solar wind speed. Finally, we identify a vanishing speed, at which A(sub He), is zero, is 259 km/s and note that this speed corresponds to the minimum solar wind speed observed at one AU. The vanishing speed may be related to previous theoretical work in which enhancements of coronal helium lead to stagnation of the escaping proton flux. During solar maximum the A(sub He), dependences on speed and latitude disappear, and we interpret this as evidence of two source regions for slow solar wind in the ecliptic plane, one being the solar minimum streamer belt and the other likely being active regions.

  4. Level-crossing statistics of the horizontal wind speed in the planetary surface boundary layer

    NASA Astrophysics Data System (ADS)

    Edwards, Paul J.; Hurst, Robert B.

    2001-09-01

    The probability density of the times for which the horizontal wind remains above or below a given threshold speed is of some interest in the fields of renewable energy generation and pollutant dispersal. However there appear to be no analytic or conceptual models which account for the observed power law form of the distribution of these episode lengths over a range of over three decades, from a few tens of seconds to a day or more. We reanalyze high resolution wind data and demonstrate the fractal character of the point process generated by the wind speed level crossings. We simulate the fluctuating wind speed by a Markov process which approximates the characteristics of the real (non-Markovian) wind and successfully generates a power law distribution of episode lengths. However, fundamental questions concerning the physical basis for this behavior and the connection between the properties of a continuous-time stochastic process and the fractal statistics of the point process generated by its level crossings remain unanswered.

  5. Passive air sampling using semipermeable membrane devices at different wind-speeds in situ calibrated by performance reference compounds.

    PubMed

    Söderström, Hanna S; Bergqvist, Per-Anders

    2004-09-15

    Semipermeable membrane devices (SPMDs) are passive samplers used to measure the vapor phase of organic pollutants in air. This study tested whether extremely high wind-speeds during a 21-day sampling increased the sampling rates of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), and whether the release of performance reference compounds (PRCs) was related to the uptakes at different wind-speeds. Five samplers were deployed in an indoor, unheated, and dark wind tunnel with different wind-speeds at each site (6-50 m s(-1)). In addition, one sampler was deployed outside the wind tunnel and one outside the building. To test whether a sampler, designed to reduce the wind-speeds, decreased the uptake and release rates, each sampler in the wind tunnel included two SPMDs positioned inside a protective device and one unprotected SPMD outside the device. The highest amounts of PAHs and PCBs were found in the SPMDs exposed to the assumed highest wind-speeds. Thus, the SPMD sampling rates increased with increasing wind-speeds, indicating that the uptake was largely controlled by the boundary layer at the membrane-air interface. The coefficient of variance (introduced by the 21-day sampling and the chemical analysis) for the air concentrations of three PAHs and three PCBs, calculated using the PRC data, was 28-46%. Thus, the PRCs had a high ability to predict site effects of wind and assess the actual sampling situation. Comparison between protected and unprotected SPMDs showed that the sampler design reduced the wind-speed inside the devices and thereby the uptake and release rates.

  6. Variable speed generator technology options for wind turbine generators

    NASA Technical Reports Server (NTRS)

    Lipo, T. A.

    1995-01-01

    The electrical system options for variable speed operation of a wind turbine generator are treated in this paper. The key operating characteristics of each system are discussed and the major advantages and disadvantages of each are identified

  7. Validation of odor concentration from mechanical-biological treatment piles using static chamber and wind tunnel with different wind speed values.

    PubMed

    Szyłak-Szydłowski, Mirosław

    2017-09-01

    The basic principle of odor sampling from surface sources is based primarily on the amount of air obtained from a specific area of the ground, which acts as a source of malodorous compounds. Wind tunnels and flux chambers are often the only available, direct method of evaluating the odor fluxes from small area sources. There are currently no widely accepted chamber-based methods; thus, there is still a need for standardization of these methods to ensure accuracy and comparability. Previous research has established that there is a significant difference between the odor concentration values obtained using the Lindvall chamber and those obtained by a dynamic flow chamber. Thus, the present study compares sampling methods using a streaming chamber modeled on the Lindvall cover (using different wind speeds), a static chamber, and a direct sampling method without any screens. The volumes of chambers in the current work were similar, ~0.08 m 3 . This study was conducted at the mechanical-biological treatment plant in Poland. Samples were taken from a pile covered by the membrane. Measured odor concentration values were between 2 and 150 ou E /m 3 . Results of the study demonstrated that both chambers can be used interchangeably in the following conditions: odor concentration is below 60 ou E /m 3 , wind speed inside the Lindvall chamber is below 0.2 m/sec, and a flow value is below 0.011 m 3 /sec. Increasing the wind speed above the aforementioned value results in significant differences in the results obtained between those methods. In all experiments, the results of the concentration of odor in the samples using the static chamber were consistently higher than those from the samples measured in the Lindvall chamber. Lastly, the results of experiments were employed to determine a model function of the relationship between wind speed and odor concentration values. Several researchers wrote that there are no widely accepted chamber-based methods. Also, there is still a

  8. Air-sea dimethylsulfide (DMS) gas transfer in the North Atlantic: evidence for limited interfacial gas exchange at high wind speed

    NASA Astrophysics Data System (ADS)

    Bell, T. G.; De Bruyn, W.; Miller, S. D.; Ward, B.; Christensen, K.; Saltzman, E. S.

    2013-11-01

    Shipboard measurements of eddy covariance dimethylsulfide (DMS) air-sea fluxes and seawater concentration were carried out in the North Atlantic bloom region in June/July 2011. Gas transfer coefficients (k660) show a linear dependence on mean horizontal wind speed at wind speeds up to 11 m s-1. At higher wind speeds the relationship between k660 and wind speed weakens. At high winds, measured DMS fluxes were lower than predicted based on the linear relationship between wind speed and interfacial stress extrapolated from low to intermediate wind speeds. In contrast, the transfer coefficient for sensible heat did not exhibit this effect. The apparent suppression of air-sea gas flux at higher wind speeds appears to be related to sea state, as determined from shipboard wave measurements. These observations are consistent with the idea that long waves suppress near-surface water-side turbulence, and decrease interfacial gas transfer. This effect may be more easily observed for DMS than for less soluble gases, such as CO2, because the air-sea exchange of DMS is controlled by interfacial rather than bubble-mediated gas transfer under high wind speed conditions.

  9. Extended Statistical Short-Range Guidance for Peak Wind Speed Analyses at the Shuttle Landing Facility: Phase II Results

    NASA Technical Reports Server (NTRS)

    Lambert, Winifred C.

    2003-01-01

    This report describes the results from Phase II of the AMU's Short-Range Statistical Forecasting task for peak winds at the Shuttle Landing Facility (SLF). The peak wind speeds are an important forecast element for the Space Shuttle and Expendable Launch Vehicle programs. The 45th Weather Squadron and the Spaceflight Meteorology Group indicate that peak winds are challenging to forecast. The Applied Meteorology Unit was tasked to develop tools that aid in short-range forecasts of peak winds at tower sites of operational interest. A seven year record of wind tower data was used in the analysis. Hourly and directional climatologies by tower and month were developed to determine the seasonal behavior of the average and peak winds. Probability density functions (PDF) of peak wind speed were calculated to determine the distribution of peak speed with average speed. These provide forecasters with a means of determining the probability of meeting or exceeding a certain peak wind given an observed or forecast average speed. A PC-based Graphical User Interface (GUI) tool was created to display the data quickly.

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

    NASA Astrophysics Data System (ADS)

    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.

  11. An Improved Wind Speed Retrieval Algorithm For The CYGNSS Mission

    NASA Astrophysics Data System (ADS)

    Ruf, C. S.; Clarizia, M. P.

    2015-12-01

    The NASA spaceborne Cyclone Global Navigation Satellite System (CYGNSS) mission is a constellation of 8 microsatellites focused on tropical cyclone (TC) inner core process studies. CYGNSS will be launched in October 2016, and will use GPS-Reflectometry (GPS-R) to measure ocean surface wind speed in all precipitating conditions, and with sufficient frequency to resolve genesis and rapid intensification. Here we present a modified and improved version of the current baseline Level 2 (L2) wind speed retrieval algorithm designed for CYGNSS. An overview of the current approach is first presented, which makes use of two different observables computed from 1-second Level 1b (L1b) delay-Doppler Maps (DDMs) of radar cross section. The first observable, the Delay-Doppler Map Average (DDMA), is the averaged radar cross section over a delay-Doppler window around the DDM peak (i.e. the specular reflection point coordinate in delay and Doppler). The second, the Leading Edge Slope (LES), is the leading edge of the Integrated Delay Waveform (IDW), obtained by integrating the DDM along the Doppler dimension. The observables are calculated over a limited range of time delays and Doppler frequencies to comply with baseline spatial resolution requirements for the retrieved winds, which in the case of CYGNSS is 25 km. In the current approach, the relationship between the observable value and the surface winds is described by an empirical Geophysical Model Function (GMF) that is characterized by a very high slope in the high wind regime, for both DDMA and LES observables, causing large errors in the retrieval at high winds. A simple mathematical modification of these observables is proposed, which linearizes the relationship between ocean surface roughness and the observables. This significantly reduces the non-linearity present in the GMF that relate the observables to the wind speed, and reduces the root-mean square error between true and retrieved winds, particularly in the high wind

  12. The Impacts of Wind Speed Trends and Long-term Variability in Relation to Hydroelectric Reservoir Inflows on Wind Power in the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Cross, B.; Kohfeld, K. E.; Cooper, A.; Bailey, H. J.; Rucker, M.

    2013-12-01

    The use of wind power is growing rapidly in the Pacific Northwest (PNW ) due to environmental concerns, decreasing costs of implementation, strong wind speeds, and a desire to diversify electricity sources to minimize the impacts of streamflow variability on electricity prices and system flexibility. In hydroelectric dominated systems, like the PNW, the benefits of wind power can be maximized by accounting for the relationship between long term variability in wind speeds and reservoir inflows. Clean energy policies in British Columbia make the benefits of increased wind power generation during low streamflow periods particularly large, by preventing the overbuilding of marginal hydroelectric projects. The goal of this work was to quantify long-term relationships between wind speed and streamflow behavior in British Columbia. Wind speed data from the North American Regional Reanalysis (NARR) and cumulative usable inflows (CUI) from BC Hydro were used to analyze 10m wind speed and density (WD) trends, WD-CUI correlations, and WD anomalies during low and high inflow periods in the PNW (40°N to 65°N, 110°W to 135°W) from 1979-2010. Statistically significant positive wind speed and density trends were found for most of the PNW, with the largest increases along the Pacific Coast. CUI-WD correlations were weakly positive for most regions, with the highest values along the US coast (r ~0.55), generally weaker correlations to the north, and negative correlations (r ~ -0.25) along BC's North Coast. When considering seasonal relationships, the Spring freshet was coincident with lower WD anomalies west of the Rocky Mountains and higher WDs to the east. A similar but opposite pattern was observed for low inflow winter months. When considering interannual variability, lowest inflow years experienced positive WD anomalies (up to 40% increases) for the North Coast. In highest inflow years, positive WD anomalies were widespread in the US and for smaller patches of central BC

  13. Spatial distribution of threshold wind speeds for dust outbreaks in northeast Asia

    NASA Astrophysics Data System (ADS)

    Kimura, Reiji; Shinoda, Masato

    2010-01-01

    Asian windblown dust events cause human and animal health effects and agricultural damage in dust source areas such as China and Mongolia and cause "yellow sand" events in Japan and Korea. It is desirable to develop an early warning system to help prevent such damage. We used our observations at a Mongolian station together with data from previous studies to model the spatial distribution of threshold wind speeds for dust events in northeast Asia (35°-45°N and 100°-115°E). Using a map of Normalized Difference Vegetation Index (NDVI), we estimated spatial distributions of vegetation cover, roughness length, threshold friction velocity, and threshold wind speed. We also recognized a relationship between NDVI in the dust season and maximum NDVI in the previous year. Thus, it may be possible to predict the threshold wind speed in the next dust season using the maximum NDVI in the previous year.

  14. CONSTRAINING HIGH-SPEED WINDS IN EXOPLANET ATMOSPHERES THROUGH OBSERVATIONS OF ANOMALOUS DOPPLER SHIFTS DURING TRANSIT

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Miller-Ricci Kempton, Eliza; Rauscher, Emily, E-mail: ekempton@ucolick.org

    2012-06-01

    Three-dimensional (3D) dynamical models of hot Jupiter atmospheres predict very strong wind speeds. For tidally locked hot Jupiters, winds at high altitude in the planet's atmosphere advect heat from the day side to the cooler night side of the planet. Net wind speeds on the order of 1-10 km s{sup -1} directed towards the night side of the planet are predicted at mbar pressures, which is the approximate pressure level probed by transmission spectroscopy. These winds should result in an observed blueshift of spectral lines in transmission on the order of the wind speed. Indeed, Snellen et al. recently observedmore » a 2 {+-} 1 km s{sup -1} blueshift of CO transmission features for HD 209458b, which has been interpreted as a detection of the day-to-night (substellar to anti-stellar) winds that have been predicted by 3D atmospheric dynamics modeling. Here, we present the results of a coupled 3D atmospheric dynamics and transmission spectrum model, which predicts the Doppler-shifted spectrum of a hot Jupiter during transit resulting from winds in the planet's atmosphere. We explore four different models for the hot Jupiter atmosphere using different prescriptions for atmospheric drag via interaction with planetary magnetic fields. We find that models with no magnetic drag produce net Doppler blueshifts in the transmission spectrum of {approx}2 km s{sup -1} and that lower Doppler shifts of {approx}1 km s{sup -1} are found for the higher drag cases, results consistent with-but not yet strongly constrained by-the Snellen et al. measurement. We additionally explore the possibility of recovering the average terminator wind speed as a function of altitude by measuring Doppler shifts of individual spectral lines and spatially resolving wind speeds across the leading and trailing terminators during ingress and egress.« less

  15. Flow-Visualization Techniques Used at High Speed by Configuration Aerodynamics Wind-Tunnel-Test Team

    NASA Technical Reports Server (NTRS)

    Lamar, John E. (Editor)

    2001-01-01

    This paper summarizes a variety of optically based flow-visualization techniques used for high-speed research by the Configuration Aerodynamics Wind-Tunnel Test Team of the High-Speed Research Program during its tenure. The work of other national experts is included for completeness. Details of each technique with applications and status in various national wind tunnels are given.

  16. Two Machine Learning Approaches for Short-Term Wind Speed Time-Series Prediction.

    PubMed

    Ak, Ronay; Fink, Olga; Zio, Enrico

    2016-08-01

    The increasing liberalization of European electricity markets, the growing proportion of intermittent renewable energy being fed into the energy grids, and also new challenges in the patterns of energy consumption (such as electric mobility) require flexible and intelligent power grids capable of providing efficient, reliable, economical, and sustainable energy production and distribution. From the supplier side, particularly, the integration of renewable energy sources (e.g., wind and solar) into the grid imposes an engineering and economic challenge because of the limited ability to control and dispatch these energy sources due to their intermittent characteristics. Time-series prediction of wind speed for wind power production is a particularly important and challenging task, wherein prediction intervals (PIs) are preferable results of the prediction, rather than point estimates, because they provide information on the confidence in the prediction. In this paper, two different machine learning approaches to assess PIs of time-series predictions are considered and compared: 1) multilayer perceptron neural networks trained with a multiobjective genetic algorithm and 2) extreme learning machines combined with the nearest neighbors approach. The proposed approaches are applied for short-term wind speed prediction from a real data set of hourly wind speed measurements for the region of Regina in Saskatchewan, Canada. Both approaches demonstrate good prediction precision and provide complementary advantages with respect to different evaluation criteria.

  17. Results of a zonally truncated three-dimensional model of the Venus middle atmosphere

    NASA Technical Reports Server (NTRS)

    Newman, M.

    1992-01-01

    Although the equatorial rotational speed of the solid surface of Venus is only 4 m s(exp-1), the atmospheric rotational speed reaches a maximum of approximately 100 m s(exp-1) near the equatorial cloud top level (65 to 70 km). This phenomenon, known as superrotation, is the central dynamical problem of the Venus atmosphere. We report here the results of numerical simulations aimed at clarifying the mechanism for maintaining the equatorial cloud top rotation. Maintenance of an equatorial rotational speed maximum above the surface requires waves or eddies that systematically transport angular momentum against its zonal mean gradient. The zonally symmetric Hadley circulation is driven thermally and acts to reduce the rotational speed at the equatorial cloud top level; thus wave or eddy transport must counter this tendency as well as friction. Planetary waves arising from horizontal shear instability of the zonal flow (barotropic instability) could maintain the equatorial rotation by transporting angular momentum horizontally from midlatitudes toward the equator. Alternatively, vertically propagating waves could provide the required momentum source. The relative motion between the rotating atmosphere and the pattern of solar heating, which as a maximum where solar radiation is absorbed near the cloud tops, drives diurnal and semidiurnal thermal tides that propagate vertically away from the cloud top level. The effect of this wave propagation is to transport momentum toward the cloud top level at low latitudes and accelerate the mean zonal flow there. We employ a semispectral primitive equation model with a zonal mean flow and zonal wavenumbers 1 and 2. These waves correspond to the diurnal and semidiurnal tides, but they can also be excited by barotropic or baroclinic instability. Waves of higher wavenumbers and interactions between the waves are neglected. Symmetry about the equator is assumed, so the model applies to one hemisphere and covers the altitude range 30 to

  18. A generalized model for the air-sea transfer of dimethyl sulfide at high wind speeds

    NASA Astrophysics Data System (ADS)

    Vlahos, Penny; Monahan, Edward C.

    2009-11-01

    The air-sea exchange of dimethyl sulfide (DMS) is an important component of ocean biogeochemistry and global climate models. Both laboratory experiments and field measurements of DMS transfer rates have shown that the air-sea flux of DMS is analogous to that of other significant greenhouse gases such as CO2 at low wind speeds (<10 m/s) but that these DMS transfer rates may diverge from other gases as wind speeds increase. Herein we provide a mechanism that predicts the attenuation of DMS transfer rates at high wind speeds. The model is based on the amphiphilic nature of DMS that leads to transfer delay at the water-bubble interface and becomes significant at wind speeds above >10 m/s. The result is an attenuation of the dimensionless Henry's Law constant (H) where (Heff = H/(1 + (Cmix/Cw) ΦB) by a solubility enhancement Cmix/Cw, and the fraction of bubble surface area per m2 surface ocean.

  19. Effect of Wind Speed and Relative Humidity on Atmospheric Dust Concentrations in Semi-Arid Climates

    PubMed Central

    Csavina, Janae; Field, Jason; Félix, Omar; Corral-Avitia, Alba Y.; Sáez, A. Eduardo; Betterton, Eric A.

    2014-01-01

    Atmospheric particulate have deleterious impacts on human health. Predicting dust and aerosol emission and transport would be helpful to reduce harmful impacts but, despite numerous studies, prediction of dust events and contaminant transport in dust remains challenging. In this work, we show that relative humidity and wind speed are both determinants in atmospheric dust concentration. Observations of atmospheric dust concentrations in Green Valley, AZ, USA, and Juárez, Chihuahua, México, show that PM10 concentrations are not directly correlated with wind speed or relative humidity separately. However, selecting the data for high wind speeds (> 4 m/s at 10 m elevation), a definite trend is observed between dust concentration and relative humidity: dust concentration increases with relative humidity, reaching a maximum around 25% and it subsequently decreases with relative humidity. Models for dust storm forecasting may be improved by utilizing atmospheric humidity and wind speed as main drivers for dust generation and transport. PMID:24769193

  20. A framework for estimating stratospheric wind speeds from unknown sources and application to the 2010 December 25 bolide

    NASA Astrophysics Data System (ADS)

    Arrowsmith, Stephen J.; Marcillo, Omar; Drob, Douglas P.

    2013-10-01

    We present a methodology for infrasonic remote sensing of winds in the stratosphere that does not require discrete ground-truth events. Our method uses measured time delays between arrays of sensors to provide group velocities (referred to here as celerities) and then minimizes the difference between observed and predicted celerities by perturbing an initial atmospheric specification. Because we focus on interarray propagation effects, it is not necessary to simulate the full propagation path from source to receiver. This feature allows us to use a relatively simple forward model that is applicable over short-regional distances. By focusing on stratospheric returns, we show that our non-linear inversion scheme converges much better if the starting model contains a strong stratospheric duct. Using the Horizontal Wind Model (HWM)/Mass Spectrometer Incoherent Scatter (MSISE) empirical climatology as a starting model, we demonstrate that the inversion scheme is robust to large uncertainties in backazimuth, but that uncertainties in the measured trace velocity and celerity require the use of prior constraints to ensure suitable convergence. The inversion of synthetic data, using realistic estimates of measurement error, shows that our scheme will nevertheless improve upon a starting model under most scenarios. The inversion scheme is applied to infrasound data recorded from a large event on 2010 December 25, which is presumed to be a bolide, using data from a nine-element infrasound network in Utah. We show that our recorded data require a stronger zonal wind speed in the stratosphere than is present in the HWM profile, and are more consistent with the Ground-to-Space (G2S) profile.

  1. Online Bayesian Learning with Natural Sequential Prior Distribution Used for Wind Speed Prediction

    NASA Astrophysics Data System (ADS)

    Cheggaga, Nawal

    2017-11-01

    Predicting wind speed is one of the most important and critic tasks in a wind farm. All approaches, which directly describe the stochastic dynamics of the meteorological data are facing problems related to the nature of its non-Gaussian statistics and the presence of seasonal effects .In this paper, Online Bayesian learning has been successfully applied to online learning for three-layer perceptron's used for wind speed prediction. First a conventional transition model based on the squared norm of the difference between the current parameter vector and the previous parameter vector has been used. We noticed that the transition model does not adequately consider the difference between the current and the previous wind speed measurement. To adequately consider this difference, we use a natural sequential prior. The proposed transition model uses a Fisher information matrix to consider the difference between the observation models more naturally. The obtained results showed a good agreement between both series, measured and predicted. The mean relative error over the whole data set is not exceeding 5 %.

  2. Efficient Low-Speed Flight in a Wind Field

    NASA Technical Reports Server (NTRS)

    Feldman, Michael A.

    1996-01-01

    A new software tool was needed for flight planning of a high altitude, low speed unmanned aerial vehicle which would be flying in winds close to the actual airspeed of the vehicle. An energy modeled NLP (non-linear programming) formulation was used to obtain results for a variety of missions and wind profiles. The energy constraint derived included terms due to the wind field and the performance index was a weighted combination of the amount of fuel used and the final time. With no emphasis on time and with no winds the vehicle was found to fly at maximum lift to drag velocity, V(sub md). When flying in tail winds the velocity was less than V(sub md), while flying in head winds the velocity was higher than V(sub md). A family of solutions was found with varying times of flight and varying fuel amounts consumed which will aid the operator in choosing a flight plan depending on a desired landing time. At certain parts of the flight, the turning terms in the energy constraint equation were found to be significant. An analysis of a simpler vertical plane cruise optimal control problem was used to explain some of the characteristics of the vertical plane NLP results.

  3. Estimation of the high-spatial-resolution variability in extreme wind speeds for forestry applications

    NASA Astrophysics Data System (ADS)

    Venäläinen, Ari; Laapas, Mikko; Pirinen, Pentti; Horttanainen, Matti; Hyvönen, Reijo; Lehtonen, Ilari; Junila, Päivi; Hou, Meiting; Peltola, Heli M.

    2017-07-01

    The bioeconomy has an increasing role to play in climate change mitigation and the sustainable development of national economies. In Finland, a forested country, over 50 % of the current bioeconomy relies on the sustainable management and utilization of forest resources. Wind storms are a major risk that forests are exposed to and high-spatial-resolution analysis of the most vulnerable locations can produce risk assessment of forest management planning. In this paper, we examine the feasibility of the wind multiplier approach for downscaling of maximum wind speed, using 20 m spatial resolution CORINE land-use dataset and high-resolution digital elevation data. A coarse spatial resolution estimate of the 10-year return level of maximum wind speed was obtained from the ERA-Interim reanalyzed data. Using a geospatial re-mapping technique the data were downscaled to 26 meteorological station locations to represent very diverse environments. Applying a comparison, we find that the downscaled 10-year return levels represent 66 % of the observed variation among the stations examined. In addition, the spatial variation in wind-multiplier-downscaled 10-year return level wind was compared with the WAsP model-simulated wind. The heterogeneous test area was situated in northern Finland, and it was found that the major features of the spatial variation were similar, but in some locations, there were relatively large differences. The results indicate that the wind multiplier method offers a pragmatic and computationally feasible tool for identifying at a high spatial resolution those locations with the highest forest wind damage risks. It can also be used to provide the necessary wind climate information for wind damage risk model calculations, thus making it possible to estimate the probability of predicted threshold wind speeds for wind damage and consequently the probability (and amount) of wind damage for certain forest stand configurations.

  4. Effect of Wind Speed on Aerosol Optical Depth over Remote Oceans, Based on Data from the Maritime Aerosol Network

    NASA Technical Reports Server (NTRS)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; hide

    2012-01-01

    The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (approx. 0.004 - 0.005), even for strong winds over 10m/s. The relationships show significant scatter (correlation coefficients typically in the range 0.3 - 0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

  5. Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; Quinn, P. K.; Sciare, J.; Gulev, S. K.; Piketh, S.; Losno, R.; Kinne, S.; Radionov, V. F.

    2011-12-01

    The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (∼0.004-0.005), even for strong winds over 10 m s-1. The relationships show significant scatter (correlation coefficients typically in the range 0.3-0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used.

  6. Effect of wind speed on aerosol optical depth over remote oceans, based on data from the Maritime Aerosol Network

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; Quinn, P. K.; Sciare, J.; Gulev, S. K.; Piketh, S.; Losno, R.; Kinne, S.; Radionov, V. F.

    2012-02-01

    The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (~0.004-0.005), even for strong winds over 10 m s-1. The relationships show significant scatter (correlation coefficients typically in the range 0.3-0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used.

  7. Understanding the Benefits and Limitations of Increasing Maximum Rotor Tip Speed for Utility-Scale Wind Turbines

    NASA Astrophysics Data System (ADS)

    Ning, A.; Dykes, K.

    2014-06-01

    For utility-scale wind turbines, the maximum rotor rotation speed is generally constrained by noise considerations. Innovations in acoustics and/or siting in remote locations may enable future wind turbine designs to operate with higher tip speeds. Wind turbines designed to take advantage of higher tip speeds are expected to be able to capture more energy and utilize lighter drivetrains because of their decreased maximum torque loads. However, the magnitude of the potential cost savings is unclear, and the potential trade-offs with rotor and tower sizing are not well understood. A multidisciplinary, system-level framework was developed to facilitate wind turbine and wind plant analysis and optimization. The rotors, nacelles, and towers of wind turbines are optimized for minimum cost of energy subject to a large number of structural, manufacturing, and transportation constraints. These optimization studies suggest that allowing for higher maximum tip speeds could result in a decrease in the cost of energy of up to 5% for land-based sites and 2% for offshore sites when using current technology. Almost all of the cost savings are attributed to the decrease in gearbox mass as a consequence of the reduced maximum rotor torque. Although there is some increased energy capture, it is very minimal (less than 0.5%). Extreme increases in tip speed are unnecessary; benefits for maximum tip speeds greater than 100-110 m/s are small to nonexistent.

  8. Wind-tunnel measurement of noise emitted by helicopter rotors at high speed

    NASA Astrophysics Data System (ADS)

    Prieur, J.

    Measurements of high-speed impulsive helicopter rotor noise in a wind-tunnel are presented. High-speed impulsive noise measurements have been performed in 1988 in the ONERA S2ch wind-tunnel, fitted with an acoustic lining, on two types of rotors. They show that substantial noise reduction is obtained with sweptback tips, initially designed for aerodynamic purposes, which lower transonic effects on the advancing blade tip. Emphasis is placed on the necessity of taking into account the acoustic annoyance problem, using noise prediction tools, when designing new helicopter blades.

  9. Ockham's Razorblade Shaving Wind-Induced Circulation

    NASA Astrophysics Data System (ADS)

    Bergmann, Juan Carlos

    2010-05-01

    Terrestrial physical oceanography is fortunate because of the existence of the continents that divide the low-latitude oceans into basins. At first glance, the previous statement appears to be not obvious because an ocean-planet should be much simpler to describe. Simple-case explanation is the central aspect of Ockham's Razorblade: If a theory fails to describe the most-simple case properly, the theory is, at least, ‘not good'. Also Descartes' methodical rules take the most-simple case as starting point. The analysis of wind-induced circulation on an ocean-planet will support the initial statement. Earth's south hemisphere is dominated by the oceans. The continents' influence on the zonal-average zonal-wind climate is relatively small. Therefore, South Hemisphere's zonal wind pattern is a relatively good proxy for that of an ocean planet. Application of this wind-stress pattern to an ocean planet yields reasonable meridional mass-flow results from the polar-regions down to the high-pressure belts: Down-welling and up-welling of water-mass are approximately balanced. However, the entire tropical circulation can in principle not be closed because there is only down-welling - even if the extreme down-welling in the equatorial belt (± 8°, with a singularity at the equator) is disregarded. The only input to the calculations is the observed terrestrial south-hemisphere zonal wind-stress pattern. Meridional stress is irrelevant because it produces a closed zonal Ekman-transport around the ocean planet (sic!). Vertical mass-transport is calculated from the divergence of the wind-induced meridional Ekman-mass-transport, which in its turn is a necessary consequence of angular-momentum conservation. No assumptions are made on how the return-flows at depth are forced because the wind-force equations cannot contribute hereto. This circumstance expresses a fundamental difference to atmospheric circulation, where mechanical forcing is caused by the pressure-fields that

  10. Unusual behavior of quiet-time zonal and vertical plasma drift velocities over Jicamarca during the recent extended solar minimum of 2008

    NASA Astrophysics Data System (ADS)

    Santos, Ângela M.; Abdu, Mangalathayil A.; Souza, Jonas R.; Batista, Inez S.; Sobral, José H. A.

    2017-11-01

    The influence of the recent deep and prolonged solar minimum on the daytime zonal and vertical plasma drift velocities during quiet time is investigated in this work. Analyzing the data obtained from incoherent scatter radar from Jicamarca (11.95° S, 76.87° W) we observe an anomalous behavior of the zonal plasma drift during June 2008 characterized by lower than usual daytime westward drift and its early afternoon reversal to eastward. As a case study the zonal drift observed on 24 June 2008 is modeled using a realistic low-latitude ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE (SUPIM-INPE). The results show that an anomalously low zonal wind was mainly responsible for the observed anomalous behavior in the zonal drift. A comparative study of the vertical plasma drifts obtained from magnetometer data for some periods of maximum (2000-2002) and minimum solar activity (1998, 2008, 2010) phases reveal a considerable decrease on the E-region conductivity and the dynamo electric field during 2008. However, we believe that the contribution of these characteristics to the unusual behavior of the zonal plasma drift is significantly smaller than that arising from the anomalously low zonal wind. The SUPIM-INPE result of the critical frequency of the F layer (foF2) over Jicamarca suggested a lower radiation flux than that predicted by solar irradiance model (SOLAR2000) for June 2008.

  11. The climatology of low-latitude ionospheric densities and zonal drifts from IMAGE-FUV.

    NASA Astrophysics Data System (ADS)

    Immel, T. J.; Sagawa, E.; Frey, H. U.; Mende, S. B.; Patel, J.

    2004-12-01

    The IMAGE satellite was the first dedicated to magnetospheric imaging, but has also provided numerous images of the nightside ionosphere with its Far-Ultraviolet (FUV) spectrographic imager. Nightside emissions of O I at 135.6-nm originating away from the aurora are due to recombination of ionospheric O+, and vary in intensity with (O+)2. IMAGE-FUV, operating in a highly elliptical orbit with apogee at middle latitudes and >7 Re altitude, measures this emission globally with 100-km resolution. During each 14.5 hour orbit, IMAGE-FUV is able to monitor nightside ionospheric densities for up to 6-7 hours. Hundreds of low-latitude ionospheric bubbles, their development and drift speed, and a variety of other dynamical variations in brightness and morphology of the equatorial anomalies have been observed during this mission. Furthermore, the average global distribution of low-latitude ionospheric plasma densities can be determined in 3 days. Imaging data collected from February through June of 2002 are used to compile a dataset containing a variety of parameters (e.g., latitude and brightness of peak plasma density, zonal bubble drift speed) which can be drawn from for climatological studies. Recent results indicate that the average ground speed of low-latitude zonal plasma drifts vary with longitude by up to 50%, and that a periodic variation in ionospheric densities with longitude suggests the influence of a lower-thermospheric non-migrating tide with wave number = 4 on ionospheric densities. An excellent correlation between zonal drift speed and the magnetic storm index Dst is also found.

  12. Performance of Statistical Temporal Downscaling Techniques of Wind Speed Data Over Aegean Sea

    NASA Astrophysics Data System (ADS)

    Gokhan Guler, Hasan; Baykal, Cuneyt; Ozyurt, Gulizar; Kisacik, Dogan

    2016-04-01

    Wind speed data is a key input for many meteorological and engineering applications. Many institutions provide wind speed data with temporal resolutions ranging from one hour to twenty four hours. Higher temporal resolution is generally required for some applications such as reliable wave hindcasting studies. One solution to generate wind data at high sampling frequencies is to use statistical downscaling techniques to interpolate values of the finer sampling intervals from the available data. In this study, the major aim is to assess temporal downscaling performance of nine statistical interpolation techniques by quantifying the inherent uncertainty due to selection of different techniques. For this purpose, hourly 10-m wind speed data taken from 227 data points over Aegean Sea between 1979 and 2010 having a spatial resolution of approximately 0.3 degrees are analyzed from the National Centers for Environmental Prediction (NCEP) The Climate Forecast System Reanalysis database. Additionally, hourly 10-m wind speed data of two in-situ measurement stations between June, 2014 and June, 2015 are considered to understand effect of dataset properties on the uncertainty generated by interpolation technique. In this study, nine statistical interpolation techniques are selected as w0 (left constant) interpolation, w6 (right constant) interpolation, averaging step function interpolation, linear interpolation, 1D Fast Fourier Transform interpolation, 2nd and 3rd degree Lagrange polynomial interpolation, cubic spline interpolation, piecewise cubic Hermite interpolating polynomials. Original data is down sampled to 6 hours (i.e. wind speeds at 0th, 6th, 12th and 18th hours of each day are selected), then 6 hourly data is temporally downscaled to hourly data (i.e. the wind speeds at each hour between the intervals are computed) using nine interpolation technique, and finally original data is compared with the temporally downscaled data. A penalty point system based on

  13. In situ observations of the influence of a large onshore wind farm on near-surface temperature, turbulence intensity and wind speed profiles

    NASA Astrophysics Data System (ADS)

    Smith, Craig M.; Barthelmie, R. J.; Pryor, S. C.

    2013-09-01

    Observations of wakes from individual wind turbines and a multi-megawatt wind energy installation in the Midwestern US indicate that directly downstream of a turbine (at a distance of 190 m, or 2.4 rotor diameters (D)), there is a clear impact on wind speed and turbulence intensity (TI) throughout the rotor swept area. However, at a downwind distance of 2.1 km (26 D downstream of the closest wind turbine) the wake of the whole wind farm is not evident. There is no significant reduction of hub-height wind speed or increase in TI especially during daytime. Thus, in high turbulence regimes even very large wind installations may have only a modest impact on downstream flow fields. No impact is observable in daytime vertical potential temperature gradients at downwind distances of >2 km, but at night the presence of the wind farm does significantly decrease the vertical gradients of potential temperature (though the profile remains stably stratified), largely by increasing the temperature at 2 m.

  14. [Measurement of Speed and Direction of Ocean Surface Winds Using Quik Scat Scatterometer

    NASA Technical Reports Server (NTRS)

    Stiles, Bryan; Pollard, Brian

    2000-01-01

    The SeaWinds on QuikSCAT scatterometer was developed by NASA JPL to measure the speed and direction of ocean surface winds. Simulations performed to estimate the performance of the instrument prior to its launch have indicated that the mid-swath accuracy is worse than that of the rest of the swath. This behavior is a general characteristic of scanning pencil beam scatterometers. For SeaWinds, the accuracy of the rest of the swath, and the size of the swath are such that the instrument meets its science requirements despite mid-swath shortcomings. However, by understanding the problem at mid-swath, we can improve the performance there as well. We discuss the underlying causes of the problem in detail and propose a new wind retrieval algorithm which improves mid-swath performance. The directional discrimination ability of the instrument varies with cross track distance wind speed, and direction. By estimating the range of likely wind directions for each measurement cell, one can optimally apply information from neighboring cells where necessary in order to reduce random wind direction errors without significantly degrading the resolution of the resultant wind field. In this manner we are able to achieve mid-swath RMS wind direction errors as low as 15 degrees for low winds and 10 degrees for moderate to high winds, while at the same time preserving high resolution structures such as cyclones and fronts.

  15. Evaluation of flow quality in two large NASA wind tunnels at transonic speeds

    NASA Technical Reports Server (NTRS)

    Harvey, W. D.; Stainback, P. C.; Owen, F. K.

    1980-01-01

    Wind tunnel testing of low drag airfoils and basic transition studies at transonic speeds are designed to provide high quality aerodynamic data at high Reynolds numbers. This requires that the flow quality in facilities used for such research be excellent. To obtain a better understanding of the characteristics of facility disturbances and identification of their sources for possible facility modification, detailed flow quality measurements were made in two prospective NASA wind tunnels. Experimental results are presented of an extensive and systematic flow quality study of the settling chamber, test section, and diffuser in the Langley 8 foot transonic pressure tunnel and the Ames 12 foot pressure wind tunnel. Results indicate that the free stream velocity and pressure fluctuation levels in both facilities are low at subsonic speeds and are so high as to make it difficult to conduct meaningful boundary layer control and transition studies at transonic speeds.

  16. Small Horizontal Axis Wind Turbine under High Speed Operation: Study of Power Evaluation

    NASA Astrophysics Data System (ADS)

    Moh. M. Saad, Magedi; Mohd, Sofian Bin; Zulkafli, Mohd Fadhli Bin; Abdullah, Aslam Bin; Rahim, Mohammad Zulafif Bin; Subari, Zulkhairi Bin; Rosly, Nurhayati Binti

    2017-10-01

    Mechanical energy is produced through the rotation of wind turbine blades by air that convert the mechanical energy into electrical energy. Wind turbines are usually designed to be use for particular applications and design characteristics may vary depending on the area of use. The variety of applications is reflected on the size of turbines and their infrastructures, however, performance enhancement of wind turbine may start by analyzing the small horizontal axis wind turbine (SHAWT) under high wind speed operation. This paper analyzes the implementations of SHAWT turbines and investigates their performance in both simulation and real life. Depending on the real structure of the rotor geometry and aerodynamic test, the power performance of the SHAWT was simulated using ANSYS-FLUENT software at different wind speed up to 33.33 m/s (120km/h) in order to numerically investigate the actual turbine operation. Dynamic mesh and user define function (UDF) was used for revolving the rotor turbine via wind. Simulation results were further validated by experimental data and hence good matching was yielded. And for reducing the energy producing cost, car alternator was formed to be used as a small horizontal wind turbine. As a result, alternator-based turbine system was found to be a low-cost solution for exploitation of wind energy.

  17. Prediction and analysis of infra and low-frequency noise of upwind horizontal axis wind turbine using statistical wind speed model

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lee, Gwang-Se; Cheong, Cheolung, E-mail: ccheong@pusan.ac.kr

    Despite increasing concern about low-frequency noise of modern large horizontal-axis wind turbines (HAWTs), few studies have focused on its origin or its prediction methods. In this paper, infra- and low-frequency (the ILF) wind turbine noise are closely examined and an efficient method is developed for its prediction. Although most previous studies have assumed that the ILF noise consists primarily of blade passing frequency (BPF) noise components, these tonal noise components are seldom identified in the measured noise spectrum, except for the case of downwind wind turbines. In reality, since modern HAWTs are very large, during rotation, a single blade ofmore » the turbine experiences inflow with variation in wind speed in time as well as in space, breaking periodic perturbations of the BPF. Consequently, this transforms acoustic contributions at the BPF harmonics into broadband noise components. In this study, the ILF noise of wind turbines is predicted by combining Lowson’s acoustic analogy with the stochastic wind model, which is employed to reproduce realistic wind speed conditions. In order to predict the effects of these wind conditions on pressure variation on the blade surface, unsteadiness in the incident wind speed is incorporated into the XFOIL code by varying incident flow velocities on each blade section, which depend on the azimuthal locations of the rotating blade. The calculated surface pressure distribution is subsequently used to predict acoustic pressure at an observing location by using Lowson’s analogy. These predictions are compared with measured data, which ensures that the present method can reproduce the broadband characteristics of the measured low-frequency noise spectrum. Further investigations are carried out to characterize the IFL noise in terms of pressure loading on blade surface, narrow-band noise spectrum and noise maps around the turbine.« less

  18. 9x15 Low Speed Wind Tunnel Improvements Update

    NASA Technical Reports Server (NTRS)

    Stephens, David

    2017-01-01

    The 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic Wind Tunnel (8x6 SWT). The 9x15 LSWT was designed for performance testing of VSTOL aircraft models, but with the addition of the current acoustic treatment in 1986 the tunnel been used principally for acoustic and performance testing of aircraft propulsion systems. The present document describes an anticipated acoustic upgrade to be completed in 2018.

  19. Statistical Post-Processing of Wind Speed Forecasts to Estimate Relative Economic Value

    NASA Astrophysics Data System (ADS)

    Courtney, Jennifer; Lynch, Peter; Sweeney, Conor

    2013-04-01

    The objective of this research is to get the best possible wind speed forecasts for the wind energy industry by using an optimal combination of well-established forecasting and post-processing methods. We start with the ECMWF 51 member ensemble prediction system (EPS) which is underdispersive and hence uncalibrated. We aim to produce wind speed forecasts that are more accurate and calibrated than the EPS. The 51 members of the EPS are clustered to 8 weighted representative members (RMs), chosen to minimize the within-cluster spread, while maximizing the inter-cluster spread. The forecasts are then downscaled using two limited area models, WRF and COSMO, at two resolutions, 14km and 3km. This process creates four distinguishable ensembles which are used as input to statistical post-processes requiring multi-model forecasts. Two such processes are presented here. The first, Bayesian Model Averaging, has been proven to provide more calibrated and accurate wind speed forecasts than the ECMWF EPS using this multi-model input data. The second, heteroscedastic censored regression is indicating positive results also. We compare the two post-processing methods, applied to a year of hindcast wind speed data around Ireland, using an array of deterministic and probabilistic verification techniques, such as MAE, CRPS, probability transform integrals and verification rank histograms, to show which method provides the most accurate and calibrated forecasts. However, the value of a forecast to an end-user cannot be fully quantified by just the accuracy and calibration measurements mentioned, as the relationship between skill and value is complex. Capturing the full potential of the forecast benefits also requires detailed knowledge of the end-users' weather sensitive decision-making processes and most importantly the economic impact it will have on their income. Finally, we present the continuous relative economic value of both post-processing methods to identify which is more

  20. How El Niño can be used to improve wind speed seasonal skill?

    NASA Astrophysics Data System (ADS)

    Gonzalez-Reviriego, Nube; Marcos, Raül; Doblas-Reyes, Francisco J.; Torralba, Verónica; Cortesi, Nicola; Lee, Doo Young; Soret, Albert

    2017-04-01

    The potential benefit of seasonal wind speed forecasts for the energy sector has been recently discussed (Torralba et al. 2016, Buontempo et al. 2016). Nevertheless, the lack of skill over several inland areas and especially at high lead times, can limit the application of these seasonal probabilistic forecasts. By using a simple methodology approach, this study aims to illustrate how the scientific user-driven research, conducted in a context of climate services, should play a role in the improvement of the wind speed seasonal forecast skill. In this framework the results obtained from the correlation coefficients between the ensemble mean prediction of the ECMWF System 4 and the observed wind speeds are compared with the results from the correlations between the wind speed constructed from the seasonal predicted El Niño index and the observations. An improvement of the skill at lead times ranging from 1 up to 5 months is measured over several regions such as Northern United States, Canada, Uruguay and Argentina. The added value of this constructed wind speed predictions is found in those areas over the world where the seasonal prediction system is not able to reproduce correctly the teleconnections of El Niño. Buontempo C, Hanlon H.M., Bruno Soares M., Christel I., Soubeyroux J-M., Viel C., Calmanti S, Bosi L., Falloon P., Palin E.J., Vanvyve E., Torralba V., Gonzalez-Reviriego N., Doblas-Reyes F.J., Pope E.C.D., Newton P. and Liggins F., 2016: What have we learnt from EUPORIAS climate service prototypes? Climate Services (Submitted) Torralba V., Doblas-Reyes F.J., Macleod D., Christel I. and Davis M., 2016: Seasonal climate prediction: a new source of information for the management of wind energy resources. Journal of Applied Meteorology and Climatology (Submitted)

  1. Association between wind speed and the occurrence of sickle cell acute painful episodes: results of a case-crossover study

    PubMed Central

    Nolan, Vikki G.; Zhang, Yuqing; Lash, Timothy; Sebastiani, Paola; Steinberg, Martin H.

    2015-01-01

    Summary The role of the weather as a trigger of sickle cell acute painful episodes has long been debated. To more accurately describe the role of the weather as a trigger of painful events, we conducted a case-crossover study of the association between local weather conditions and the occurrence of painful episodes. From the Cooperative Study of Sickle Cell Disease, we identified 813 patients with sickle cell anaemia who had 3570 acute painful episodes. We found an association between wind speed and the onset of pain, specifically wind speed during the 24-h period preceding the onset of pain. Analysing wind speed as a categorical trait, showed a 13% increase (95% confidence interval: 3%, 24%) in odds of pain, when comparing the high wind speed to lower wind speed (P = 0.007). In addition, the association between wind speed and painful episodes was found to be stronger among men, particularly those in the warmer climate regions of the United States. These results are in agreement with another study that found an association between wind speed and hospital visits for pain in the United Kingdom, and lends support to physiological and clinical studies that have suggested that skin cooling is associated with sickle vasoocclusion and perhaps pain. PMID:18729854

  2. Association between wind speed and the occurrence of sickle cell acute painful episodes: results of a case-crossover study.

    PubMed

    Nolan, Vikki G; Zhang, Yuqing; Lash, Timothy; Sebastiani, Paola; Steinberg, Martin H

    2008-11-01

    The role of the weather as a trigger of sickle cell acute painful episodes has long been debated. To more accurately describe the role of the weather as a trigger of painful events, we conducted a case-crossover study of the association between local weather conditions and the occurrence of painful episodes. From the Cooperative Study of Sickle Cell Disease, we identified 813 patients with sickle cell anaemia who had 3570 acute painful episodes. We found an association between wind speed and the onset of pain, specifically wind speed during the 24-h period preceding the onset of pain. Analysing wind speed as a categorical trait, showed a 13% increase (95% confidence interval: 3%, 24%) in odds of pain, when comparing the high wind speed to lower wind speed (P = 0.007). In addition, the association between wind speed and painful episodes was found to be stronger among men, particularly those in the warmer climate regions of the United States. These results are in agreement with another study that found an association between wind speed and hospital visits for pain in the United Kingdom, and lends support to physiological and clinical studies that have suggested that skin cooling is associated with sickle vasoocclusion and perhaps pain.

  3. Reduced Solar Wind Speeds at New Horizons Beyond 30 AU

    NASA Astrophysics Data System (ADS)

    Elliott, H. A.; McComas, D. J.; Zirnstein, E.; Delamere, P. A.; Bagenal, F.; Stern, A.; Weaver, H. A., Jr.; Young, L. A.; Ennico Smith, K.; Olkin, C.

    2017-12-01

    Prior comparisons between Voyager 2 and IMP 8 observations found the solar wind had clearly decrease by 8% at a distance of 25 AU. Since mid-2016 solar rotation averaged speeds at New Horizons have been elevated relative to speeds observed in 2014 and 2015. However, we find a clear decrease in the New Horizons speeds beyond 30 AU when compared to those of ACE near Earth. At distances between 30-38.5 AU the relative speed reduction is in the 8-11% range. We will further this work by also comparing with available STEREO observations. By including STEREO, we can assess how sensitive the speed comparisons are to longitude separations and determine the appropriate time scale to average over.

  4. [Comfort of crew and passengers and atmospheric pressure, noise, wind speed in high-speed train of Shijiazhuang-Taiyuan passenger dedicated line].

    PubMed

    Zhai, Yi-biao; Huo, Wei; Liu, Qiao-ying; Chen, Bao-shan; Zhang, Jin-long; Shi, Lei

    2012-11-01

    To explore the crew and passengers' comfort on the Shijiazhuang-Taiyuan passenger dedicated line and physical factors, such as air pressure, noise, wind speed. Comfort investigation of all the crew (n = 244) and passengers (n = 377) on the Shijiazhuang-Taiyuan passenger dedicated line at speed of 250 km/h and 200 km/h and the detection of the air pressure, noise and wind speed were performed in 2011. Significantly higher ratio of comfortable feeling, lower ratio of seriously discomfortable feeling were observed in crew and passengers at 200 km/h compared with those at 250 km/h (P < 0.05), as well as rapid disappearance of discomfortable feeling in crew (P < 0.05) and significantly higher ratio of lightly discomfortable feeling and lower ratios of tinnitus and eardrum discomfort induced by air pressure and noise in passengers at 200 km/h. No significant difference was observed in ear discomfort induced by air pressure and noise among crew, and the duration of disappearance of discomfortable feeling among passengers between 200 km/h and 250 km/h. The noise in carriages exceeded the related standard when the high-speed train passing through the tunnels. The individuals feel more comfortable at 200 km/h than 250 km/h in this line., which may be related with rapid variation of wind speed and noise when the train passes through the tunnels with high speed.

  5. The Partition Between Terminal Speed and Mass Loss: Thin, Thick, and Rotating Line-Driven Winds

    NASA Astrophysics Data System (ADS)

    Gayley, K. G.; Onifer, A. J.

    2003-01-01

    Steady-state supersonic line-driven winds are important contributors to wind-blown bubbles in star forming regions. The key input to the bubble in the energy-conserving phase is the wind kinetic-energy flux, which involves both the mass-loss rate and the terminal speed. However, these quantities are themselves self-consistent parameters of the line-driving process, so relate to each other and to the resulting wind optical depth. This complex interrelation between optical depth, mass-loss, and wind speed lies at the heart of line-driven wind theory. Drawing on the successes and insights of ``CAK'' theory, I will convey a simplified view of how to unite these processes using the concept of effective opacity, with attention to the ramifications for nonspherical nebular and wind-blown structures. Recent extensions to nongray optically thick environments such as Wolf-Rayet winds and supernovae are also discussed.

  6. Wind Tunnel Studies in Aerodynamic Phenomena at High Speed

    NASA Technical Reports Server (NTRS)

    Caldwell, F W; Fales, E N

    1921-01-01

    A great amount of research and experimental work has been done and fair success obtained in an effort to place airplane and propeller design upon an empirical basis. However, one can not fail to be impressed by the apparent lack of data available toward establishing flow phenomena upon a rational basis, such that they may be interpreted in terms of the laws of physics. With this end in view it was the object of the authors to design a wind tunnel differing from the usual type especially in regard to large power and speed of flow. This report describes the wind tunnel at Mccook Field and gives the results of experiments conducted in testing the efficiency of the wind tunnel.

  7. A conceptual framework for evaluating variable speed generator options for wind energy applications

    NASA Technical Reports Server (NTRS)

    Reddoch, T. W.; Lipo, T. A.; Hinrichsen, E. N.; Hudson, T. L.; Thomas, R. J.

    1995-01-01

    Interest in variable speed generating technology has accelerated as greater emphasis on overall efficiency and superior dynamic and control properties in wind-electric generating systems are sought. This paper reviews variable speed technology options providing advantages and disadvantages of each. Furthermore, the dynamic properties of variable speed systems are contrasted with synchronous operation. Finally, control properties of variable speed systems are examined.

  8. Hurricane Imaging Radiometer Wind Speed and Rain Rate Retrievals during the 2010 GRIP Flight Experiment

    NASA Technical Reports Server (NTRS)

    Sahawneh, Saleem; Farrar, Spencer; Johnson, James; Jones, W. Linwood; Roberts, Jason; Biswas, Sayak; Cecil, Daniel

    2014-01-01

    Microwave remote sensing observations of hurricanes, from NOAA and USAF hurricane surveillance aircraft, provide vital data for hurricane research and operations, for forecasting the intensity and track of tropical storms. The current operational standard for hurricane wind speed and rain rate measurements is the Stepped Frequency Microwave Radiometer (SFMR), which is a nadir viewing passive microwave airborne remote sensor. The Hurricane Imaging Radiometer, HIRAD, will extend the nadir viewing SFMR capability to provide wide swath images of wind speed and rain rate, while flying on a high altitude aircraft. HIRAD was first flown in the Genesis and Rapid Intensification Processes, GRIP, NASA hurricane field experiment in 2010. This paper reports on geophysical retrieval results and provides hurricane images from GRIP flights. An overview of the HIRAD instrument and the radiative transfer theory based, wind speed/rain rate retrieval algorithm is included. Results are presented for hurricane wind speed and rain rate for Earl and Karl, with comparison to collocated SFMR retrievals and WP3D Fuselage Radar images for validation purposes.

  9. Hurricane Imaging Radiometer (HIRAD) Wind Speed Retrieval Assessment with Dropsondes

    NASA Technical Reports Server (NTRS)

    Cecil, Daniel J.; Biswas, Sayak K.

    2017-01-01

    Map surface wind speed over wide swath (approximately 50-60 km, for aircraft greater than FL600) in hurricanes. Provide research data for understanding hurricane structure, and intensity change. Enable improved forecasts, warnings, and decision support.

  10. Stochastic simulation of predictive space–time scenarios of wind speed using observations and physical model outputs

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bessac, Julie; Constantinescu, Emil; Anitescu, Mihai

    We propose a statistical space-time model for predicting atmospheric wind speed based on deterministic numerical weather predictions and historical measurements. We consider a Gaussian multivariate space-time framework that combines multiple sources of past physical model outputs and measurements in order to produce a probabilistic wind speed forecast within the prediction window. We illustrate this strategy on wind speed forecasts during several months in 2012 for a region near the Great Lakes in the United States. The results show that the prediction is improved in the mean-squared sense relative to the numerical forecasts as well as in probabilistic scores. Moreover, themore » samples are shown to produce realistic wind scenarios based on sample spectra and space-time correlation structure.« less

  11. Stochastic simulation of predictive space–time scenarios of wind speed using observations and physical model outputs

    DOE PAGES

    Bessac, Julie; Constantinescu, Emil; Anitescu, Mihai

    2018-03-01

    We propose a statistical space-time model for predicting atmospheric wind speed based on deterministic numerical weather predictions and historical measurements. We consider a Gaussian multivariate space-time framework that combines multiple sources of past physical model outputs and measurements in order to produce a probabilistic wind speed forecast within the prediction window. We illustrate this strategy on wind speed forecasts during several months in 2012 for a region near the Great Lakes in the United States. The results show that the prediction is improved in the mean-squared sense relative to the numerical forecasts as well as in probabilistic scores. Moreover, themore » samples are shown to produce realistic wind scenarios based on sample spectra and space-time correlation structure.« less

  12. Remote sensing of mesospheric winds with the High-Resolution Doppler Imager

    NASA Technical Reports Server (NTRS)

    Hays, Paul B.; Abreu, V. J.; Burrage, M. D.; Gell, D. A.; Grassi, H. J.; Marshall, A. R.; Morton, Y. T.; Ortland, D. A.; Skinner, W. R.; Wu, D. L.

    1992-01-01

    Observations of the winds in the upper atmosphere obtained with the High-Resolution Doppler Imager (HRDI) on the Upper Atmosphere Research Satellite (UARS) are discussed. This instrument is a very stable high-resolution triple-etalon Fabry-Perot interferometer, which is used to observe the slight Doppler shifts of absorption and emission lines in the O2 Atmospheric bands induced by atmospheric motions. Preliminary observations indicate that the winds in the mesosphere and lower thermosphere are a mixture of migrating and non-migrating tides, and planetary-scale waves. The mean meridional winds are dominated by the 1,1 diurnal tide which is easily extracted from the daily zonal means of the satellite observations. The daily mean zonal winds are a mixture of the diurnal tide and a zonal flow which is consistent with theoretical expectations.

  13. Cosmic ray modulation by high-speed solar wind fluxes

    NASA Technical Reports Server (NTRS)

    Dorman, L. I.; Kaminer, N. S.; Kuzmicheva, A. E.; Mymrina, N. V.

    1985-01-01

    Cosmic ray intensity variations connected with recurrent high-speed fluxes (HSF) of solar wind are investigated. The increase of intensity before the Earth gets into a HSF, north-south anisotropy and diurnal variation of cosmic rays inside a HSF as well as the characteristics of Forbush decreases are considered.

  14. Mesospheric circulation at the cloud top level of Venus according to Venus Monitoring Camera images

    NASA Astrophysics Data System (ADS)

    Khatuntsev, Igor; Patsaeva, Marina; Ignatiev, Nikolay; Titov, Dmitri; Markiewicz, Wojciech; Turin, Alexander

    We present results of wind speed measurements at the cloud top level of Venus derived from manual cloud tracking in the UV (365 nm) and IR (965 nm) channels of the Venus Monitoring Camera Experiment (VMC) [1] on board the Venus Express mission. Cloud details have a maximal contrast in the UV range. More then 90 orbits have been processed. 30000 manual vectors were obtained. The period of the observations covers more than 4 venusian year. Zonal wind speed demonstrates the local solar time dependence. Possible diurnal and semidiurnal components are observed [2]. According to averaged latitude profile of winds at level of the upper clouds: -The zonal speed is slightly increasing by absolute values from 90 on the equator to 105 m/s at latitudes —47 degrees; -The period of zonal rotation has the maximum at the equator (5 earth days). It has the minimum (3 days) at altitudes —50 degrees. After minimum periods are slightly increasing toward the South pole; -The meridional speed has a value 0 on the equator, and then it is linear increasing up to 10 m/s (by absolute value) at 50 degrees latitude. "-" denotes movement from the equator to the pole. -From 50 to 80 degrees the meridional speed is again decreasing by absolute value up to 0. IR (965+10 nm) day side images can be used for wind tracking. The obtained speed of the zonal wind in the low and middle latitudes are systematically less than the wind speed derived from the UV images. The average zonal speed obtained from IR day side images in the low and average latitudes is about 65-70 m/s. The given fact can be interpreted as observation of deeper layers of mesosphere in the IR range in comparison with UV. References [1] Markiewicz W. J. et al. (2007) Planet. Space Set V55(12). P.1701-1711. [2] Moissl R., et al. (2008) J. Geophys. Res. 2008. doi:10.1029/2008JE003117. V.113.

  15. Jet and storm track variability and change: adiabatic QG zonal averages and beyond... (Invited)

    NASA Astrophysics Data System (ADS)

    Robinson, W. A.

    2013-12-01

    The zonally averaged structures of extratropical jets and stormtracks, their slow variations, and their responses to climate change are all tightly constrained on the one hand by thermal wind balance and the necessary application of eddy torques to produce zonally averaged meridional motion, and, on the other hand, by the necessity that eddies propagate upshear to extract energy from the mean flow. Combining these constraints with the well developed theory of linear Rossby-wave propagation on zonally symmetric basic states has led to a large and growing number of plausible mechanisms to explain observed and modeled jet/storm track variability and responses to climate change and idealized forcing. Hidden within zonal averages is the reality that most baroclinic eddy activity is destroyed at the same latitude at which is generated: from one end to another of the fixed stormtracks in the Northern Hemisphere and baroclinic wave packets in the Southern Hemisphere. Ignored within adiabatic QG theory is the reality that baroclinic eddies gain significant energy from latent heating that involves sub-syntopic scale structures and dynamics. Here we use results from high-resolution regional and global simulations of the Northern Hemisphere storm tracks to explore the importance of non-zonal and diabatic dynamics in influencing jet change and variability and their influences on the much-studied zonal means.

  16. Orbiting observatory SOHO finds source of high-speed "wind" blowing from the Sun

    NASA Astrophysics Data System (ADS)

    1999-02-01

    "The search for the source of the solar wind has been like the hunt for the source of the Nile," said Dr. Don Hassler of the Southwest Research Institute, Boulder, Colorado, lead author of the paper in Science. "For 30 years, scientists have observed high-speed solar wind coming from regions in the solar atmosphere with open magnetic field lines, called coronal holes. However, only recently, with the observations from SOHO, have we been able to measure the detailed structure of this source region". The solar wind comes in two varieties : high-speed and low-speed. The low-speed solar wind moves at "only" 1.5 million kilometres per hour, while the high-speed wind is even faster, moving at speeds as high as 3 million kilometres per hour. As it flows past Earth, the solar wind changes the shape and structure of the Earth's magnetic field. In the past, the solar wind didn't affect us directly, but as we become increasingly dependent on advanced technology, we become more susceptible to its effects. Researchers are learning that variations in the solar wind flow can cause dramatic changes in the shape of the Earth's magnetic field, which can damage satellites and disrupt communications and electrical power systems. The nature and origin of the solar wind is one of the main mysteries ESA's solar observatory SOHO was designed to solve. It has long been thought that the solar wind flows from coronal holes; what is new is the discovery that these outflows are concentrated in specific patches at the edges of the honeycomb-shaped magnetic fields. Just below the surface of the Sun there are large convection cells, and each cell has a magnetic field associated with it. "If one thinks of these cells as paving stones in a patio, then the solar wind is breaking through like grass around the edges, concentrated in the corners where the paving stones meet", said Dr. Helen Mason, University of Cambridge, England, and co-author of the paper to appear in Science. "However, at speeds

  17. Numerical study on the impact of ground heating and ambient wind speed on flow fields in street canyons

    NASA Astrophysics Data System (ADS)

    Li, Lei; Yang, Lin; Zhang, Li-Jie; Jiang, Yin

    2012-11-01

    The impact of ground heating on flow fields in street canyons under different ambient wind speed conditions was studied based on numerical methods. A series of numerical tests were performed, and three factors including height-to-width (H/W) ratio, ambient wind speed and ground heating intensity were taken into account. Three types of street canyon with H/W ratios of 0.5, 1.0 and 2.0, respectively, were used in the simulation and seven speed values ranging from 0.0 to 3.0 m s-1 were set for the ambient wind speed. The ground heating intensity, which was defined as the difference between the ground temperature and air temperature, ranged from 10 to 40 K with an increase of 10 K in the tests. The results showed that under calm conditions, ground heating could induce circulation with a wind speed of around 1.0 m s-1, which is enough to disperse pollutants in a street canyon. It was also found that an ambient wind speed threshold may exist for street canyons with a fixed H/W ratio. When ambient wind speed was lower than the threshold identified in this study, the impact of the thermal effect on the flow field was obvious, and there existed a multi-vortex flow pattern in the street canyon. When the ambient wind speed was higher than the threshold, the circulation pattern was basically determined by dynamic effects. The tests on the impact of heating intensity showed that a higher ground heating intensity could strengthen the vortical flow within the street canyon, which would help improve pollutant diffusion capability in street canyons.

  18. Measurement of winds in Venus' upper mesosphere based on Doppler shifts of the 2.6-mm (C-12)O line

    NASA Technical Reports Server (NTRS)

    Shah, Kathryn P.; Muhleman, Duane O.; Berge, Glenn L.

    1991-01-01

    Venus observations conducted in 1988 at the first rotational transition of (C-12)O finely sampled this absorption line by means of a 32-channel filter bank; with this spatial and spectral resolution, it proved possible to measure Doppler shifts of the absorption line across the planet due to strong winds in Venus' upper mesosphere. The Doppler shifts change in a way that is indicative of westward horizontal winds. The radial wind speeds from the Doppler shifts were smoothed to reduce noise and then fitted in least-squares fashion to canonical forms of the lower atmosphere's westward zonal flow. The two flows exhibit a high correlation in orientation.

  19. An Intelligent Ensemble Neural Network Model for Wind Speed Prediction in Renewable Energy Systems.

    PubMed

    Ranganayaki, V; Deepa, S N

    2016-01-01

    Various criteria are proposed to select the number of hidden neurons in artificial neural network (ANN) models and based on the criterion evolved an intelligent ensemble neural network model is proposed to predict wind speed in renewable energy applications. The intelligent ensemble neural model based wind speed forecasting is designed by averaging the forecasted values from multiple neural network models which includes multilayer perceptron (MLP), multilayer adaptive linear neuron (Madaline), back propagation neural network (BPN), and probabilistic neural network (PNN) so as to obtain better accuracy in wind speed prediction with minimum error. The random selection of hidden neurons numbers in artificial neural network results in overfitting or underfitting problem. This paper aims to avoid the occurrence of overfitting and underfitting problems. The selection of number of hidden neurons is done in this paper employing 102 criteria; these evolved criteria are verified by the computed various error values. The proposed criteria for fixing hidden neurons are validated employing the convergence theorem. The proposed intelligent ensemble neural model is applied for wind speed prediction application considering the real time wind data collected from the nearby locations. The obtained simulation results substantiate that the proposed ensemble model reduces the error value to minimum and enhances the accuracy. The computed results prove the effectiveness of the proposed ensemble neural network (ENN) model with respect to the considered error factors in comparison with that of the earlier models available in the literature.

  20. An Intelligent Ensemble Neural Network Model for Wind Speed Prediction in Renewable Energy Systems

    PubMed Central

    Ranganayaki, V.; Deepa, S. N.

    2016-01-01

    Various criteria are proposed to select the number of hidden neurons in artificial neural network (ANN) models and based on the criterion evolved an intelligent ensemble neural network model is proposed to predict wind speed in renewable energy applications. The intelligent ensemble neural model based wind speed forecasting is designed by averaging the forecasted values from multiple neural network models which includes multilayer perceptron (MLP), multilayer adaptive linear neuron (Madaline), back propagation neural network (BPN), and probabilistic neural network (PNN) so as to obtain better accuracy in wind speed prediction with minimum error. The random selection of hidden neurons numbers in artificial neural network results in overfitting or underfitting problem. This paper aims to avoid the occurrence of overfitting and underfitting problems. The selection of number of hidden neurons is done in this paper employing 102 criteria; these evolved criteria are verified by the computed various error values. The proposed criteria for fixing hidden neurons are validated employing the convergence theorem. The proposed intelligent ensemble neural model is applied for wind speed prediction application considering the real time wind data collected from the nearby locations. The obtained simulation results substantiate that the proposed ensemble model reduces the error value to minimum and enhances the accuracy. The computed results prove the effectiveness of the proposed ensemble neural network (ENN) model with respect to the considered error factors in comparison with that of the earlier models available in the literature. PMID:27034973

  1. A Comparison of Wind Speed Data from Mechanical and Ultrasonic Anemometers

    NASA Technical Reports Server (NTRS)

    Short, D.; Wells, L.; Merceret, F.; Roeder, W. P.

    2006-01-01

    This study compared the performance of mechanical and ultrasonic anemometers at the Eastern Range (ER; Kennedy Space Center and Cape Canaveral Air Force Station on Florida's Atlantic coast) and the Western Range (WR; Vandenberg Air Force Base on California's Pacific coast). Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at the ER and WR for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The current ER and WR weather tower wind instruments are being changed from the current propeller-and-vane (ER) and cup-and-vane (WR) sensors to ultrasonic sensors through the Range Standardization and Automation (RSA) program. The differences between mechanical and ultrasonic techniques have been found to cause differences in the statistics of peak wind speed in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between RSA and current sensors to determine if there are significant differences. Approximately 3 weeks of Legacy and RSA wind data from each range were used in the study, archived during May and June 2005. The ER data spanned the full diurnal cycle, while the WR data was confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on 5 different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The 10 towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The RSA sensors were collocated at the same vertical levels as the present sensors and typically within 15 ft horizontally of each another. Data from a total of 53 RSA ultrasonic sensors, collocated with present sensors were compared. The 1-minute average wind speed/direction and the 1

  2. Examination of the wind speed limit function in the Rothermel surface fire spread model

    Treesearch

    Patricia L. Andrews; Miguel G. Cruz; Richard C. Rothermel

    2013-01-01

    The Rothermel surface fire spread model includes a wind speed limit, above which predicted rate of spread is constant. Complete derivation of the wind limit as a function of reaction intensity is given, along with an alternate result based on a changed assumption. Evidence indicates that both the original and the revised wind limits are too restrictive. Wind limit is...

  3. An Analysis of Peak Wind Speed Data from Collocated Mechanical and Ultrasonic Anemometers

    NASA Technical Reports Server (NTRS)

    Short, David A.; Wells, Leonard; Merceret, Francis J.; Roeder, William P.

    2007-01-01

    This study compared peak wind speeds reported by mechanical and ultrasonic anemometers at Cape Canaveral Air Force Station and Kennedy Space Center (CCAFS/KSC) on the east central coast of Florida and Vandenberg Air Force Base (VAFB) on the central coast of California. Launch Weather Officers, forecasters, and Range Safety analysts need to understand the performance of wind sensors at CCAFS/KSC and VAFB for weather warnings, watches, advisories, special ground processing operations, launch pad exposure forecasts, user Launch Commit Criteria (LCC) forecasts and evaluations, and toxic dispersion support. The legacy CCAFS/KSC and VAFB weather tower wind instruments are being changed from propeller-and-vane (CCAFS/KSC) and cup-and-vane (VAFB) sensors to ultrasonic sensors under the Range Standardization and Automation (RSA) program. Mechanical and ultrasonic wind measuring techniques are known to cause differences in the statistics of peak wind speed as shown in previous studies. The 45th Weather Squadron (45 WS) and the 30th Weather Squadron (30 WS) requested the Applied Meteorology Unit (AMU) to compare data between the RSA ultrasonic and legacy mechanical sensors to determine if there are significant differences. Note that the instruments were sited outdoors under naturally varying conditions and that this comparison was not designed to verify either technology. Approximately 3 weeks of mechanical and ultrasonic wind data from each range from May and June 2005 were used in this study. The CCAFS/KSC data spanned the full diurnal cycle, while the VAFB data were confined to 1000-1600 local time. The sample of 1-minute data from numerous levels on five different towers on each range totaled more than 500,000 minutes of data (482,979 minutes of data after quality control). The ten towers were instrumented at several levels, ranging from 12 ft to 492 ft above ground level. The ultrasonic sensors were collocated at the same vertical levels as the mechanical sensors and

  4. Statistical Short-Range Guidance for Peak Wind Speed Forecasts on Kennedy Space Center/Cape Canaveral Air Force Station: Phase I Results

    NASA Technical Reports Server (NTRS)

    Lambert, Winifred C.; Merceret, Francis J. (Technical Monitor)

    2002-01-01

    This report describes the results of the ANU's (Applied Meteorology Unit) Short-Range Statistical Forecasting task for peak winds. The peak wind speeds are an important forecast element for the Space Shuttle and Expendable Launch Vehicle programs. The Keith Weather Squadron and the Spaceflight Meteorology Group indicate that peak winds are challenging to forecast. The Applied Meteorology Unit was tasked to develop tools that aid in short-range forecasts of peak winds at tower sites of operational interest. A 7 year record of wind tower data was used in the analysis. Hourly and directional climatologies by tower and month were developed to determine the seasonal behavior of the average and peak winds. In all climatologies, the average and peak wind speeds were highly variable in time. This indicated that the development of a peak wind forecasting tool would be difficult. Probability density functions (PDF) of peak wind speed were calculated to determine the distribution of peak speed with average speed. These provide forecasters with a means of determining the probability of meeting or exceeding a certain peak wind given an observed or forecast average speed. The climatologies and PDFs provide tools with which to make peak wind forecasts that are critical to safe operations.

  5. Smoothing Control of Wind Farm Output by Using Kinetic Energy of Variable Speed Wind Power Generators

    NASA Astrophysics Data System (ADS)

    Sato, Daiki; Saitoh, Hiroumi

    This paper proposes a new control method for reducing fluctuation of power system frequency through smoothing active power output of wind farm. The proposal is based on the modulation of rotaional kinetic energy of variable speed wind power generators through power converters between permanent magnet synchronous generators (PMSG) and transmission lines. In this paper, the proposed control is called Fluctuation Absorption by Flywheel Characteristics control (FAFC). The FAFC can be easily implemented by adding wind farm output signal to Maximum Power Point Tracking control signal through a feedback control loop. In order to verify the effectiveness of the FAFC control, a simulation study was carried out. In the study, it was assumed that the wind farm consisting of PMSG type wind power generator and induction machine type wind power generaotors is connected with a power sysem. The results of the study show that the FAFC control is a useful method for reducing the impacts of wind farm output fluctuation on system frequency without additional devices such as secondary battery.

  6. On the Relationship Between Solar Wind Speed, Geomagnetic Activity, and the Solar Cycle Using Annual Values

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    The aa index can be decomposed into two separate components: the leading sporadic component due to solar activity as measured by sunspot number and the residual or recurrent component due to interplanetary disturbances, such as coronal holes. For the interval 1964-2006, a highly statistically important correlation (r = 0.749) is found between annual averages of the aa index and the solar wind speed (especially between the residual component of aa and the solar wind speed, r = 0.865). Because cyclic averages of aa (and the residual component) have trended upward during cycles 11-23, cyclic averages of solar wind speed are inferred to have also trended upward.

  7. Determination of transport wind speed in the gaussian plume diffusion equation for low-lying point sources

    NASA Astrophysics Data System (ADS)

    Wang, I. T.

    A general method for determining the effective transport wind speed, overlineu, in the Gaussian plume equation is discussed. Physical arguments are given for using the generalized overlineu instead of the often adopted release-level wind speed with the plume diffusion equation. Simple analytical expressions for overlineu applicable to low-level point releases and a wide range of atmospheric conditions are developed. A non-linear plume kinematic equation is derived using these expressions. Crosswind-integrated SF 6 concentration data from the 1983 PNL tracer experiment are used to evaluate the proposed analytical procedures along with the usual approach of using the release-level wind speed. Results of the evaluation are briefly discussed.

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

    NASA Astrophysics Data System (ADS)

    Yuan, Wei

    2015-04-01

    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 autumn

  9. Assessing simulated summer 10-m wind speed over China: influencing processes and sensitivities to land surface schemes

    NASA Astrophysics Data System (ADS)

    Zeng, Xin-Min; Wang, Ming; Wang, Ning; Yi, Xiang; Chen, Chaohui; Zhou, Zugang; Wang, Guiling; Zheng, Yiqun

    2018-06-01

    We assessed the sensitivity of 10-m wind speed to land surface schemes (LSSs) and the processes affecting wind speed in China during the summer of 2003 using the ARWv3 mesoscale model. The derived hydrodynamic equation, which directly reflects the effects of the processes that drive changes in the full wind speed, shows that the convection term CON (the advection effect) plays the smallest role; thus, the summer 10-m wind speed is largely dominated by the pressure gradient (PRE) and the diffusion (DFN) terms, and the equation shows that both terms are highly sensitive to the choice of LSS within the studied subareas (i.e., Northwest China, East China, and the Tibetan Plateau). For example, Northwest China had the largest DFN, with a PRE four times that of CON and the highest sensitivity of PRE to the choice of LSS, as indicated by a difference index value of 63%. Moreover, we suggest that two types of mechanisms, direct and indirect effects, affect the 10-m wind speed. Through their simulated surface fluxes (mainly the sensible heat flux), the different LSSs directly provide different amounts of heat to the surface air at local scales, which influences atmospheric stratification and the characteristics of downward momentum transport. Meanwhile, through the indirect effect, the LSS-induced changes in surface fluxes can significantly modify the distributions of the temperature and pressure fields in the lower atmosphere over larger scales. These changes alter the thermal and geostrophic winds, respectively, as well as the 10-m wind speed. Due to the differences in land properties and climates, the indirect effect (e.g., PRE) can be greater than the direct effect (e.g., DFN).

  10. The impact of changing wind speeds on gas transfer and its effect on global air-sea CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Wanninkhof, R.; Triñanes, J.

    2017-06-01

    An increase in global wind speeds over time is affecting the global uptake of CO2 by the ocean. We determine the impact of changing winds on gas transfer and CO2 uptake by using the recently updated, global high-resolution, cross-calibrated multiplatform wind product (CCMP-V2) and a fixed monthly pCO2 climatology. In particular, we assess global changes in the context of regional wind speed changes that are attributed to large-scale climate reorganizations. The impact of wind on global CO2 gas fluxes as determined by the bulk formula is dependent on several factors, including the functionality of the gas exchange-wind speed relationship and the regional and seasonal differences in the air-water partial pressure of CO2 gradient (ΔpCO2). The latter also controls the direction of the flux. Fluxes out of the ocean are influenced more by changes in the low-to-intermediate wind speed range, while ingassing is impacted more by changes in higher winds because of the regional correlations between wind and ΔpCO2. Gas exchange-wind speed parameterizations with a quadratic and third-order polynomial dependency on wind, each of which meets global constraints, are compared. The changes in air-sea CO2 fluxes resulting from wind speed trends are greatest in the equatorial Pacific and cause a 0.03-0.04 Pg C decade-1 increase in outgassing over the 27 year time span. This leads to a small overall decrease of 0.00 to 0.02 Pg C decade-1 in global net CO2 uptake, contrary to expectations that increasing winds increase net CO2 uptake.Plain Language SummaryThe effects of changing <span class="hlt">winds</span> are isolated from the total change in trends in global air-sea CO2 fluxes over the last 27 years. The overall effect of increasing <span class="hlt">winds</span> over time has a smaller impact than expected as the impact in regions of outgassing is greater than for the regions acting as a CO2 sink.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830013439','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830013439"><span>Linear retrieval and global measurements of <span class="hlt">wind</span> <span class="hlt">speed</span> from the Seasat SMMR</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pandey, P. C.</p> <p>1983-01-01</p> <p>Retrievals of <span class="hlt">wind</span> <span class="hlt">speed</span> (WS) from Seasat Scanning Multichannel Microwave Radiometer (SMMR) were performed using a two-step statistical technique. Nine subsets of two to five SMMR channels were examined for <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval. These subsets were derived by using a leaps and bound procedure based on the coefficient of determination selection criteria to a statistical data base of brightness temperatures and geophysical parameters. Analysis of Monsoon Experiment and ocean station PAPA data showed a strong correlation between sea surface temperature and water vapor. This relation was used in generating the statistical data base. Global maps of WS were produced for one and three month periods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6593974-soil-tillage-windbreak-effects-millet-cowpea-wind-speed-evaporation-wind-erosion','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6593974-soil-tillage-windbreak-effects-millet-cowpea-wind-speed-evaporation-wind-erosion"><span>Soil tillage and windbreak effects on millet and cowpea: I. <span class="hlt">Wind</span> <span class="hlt">speed</span>, evaporation, and <span class="hlt">wind</span> erosion</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Banzhaf, J.; Leihner, D.E.; Buerkert, A.</p> <p></p> <p>Deforestation, overgrazing, and declining soil regeneration periods have resulted in increased <span class="hlt">wind</span> erosion problems in dry areas of the West African Sahel, but little is known about the bio-physical factors involved. This research was conducted to determine the effects of ridging and four different windbreak spacings on <span class="hlt">wind</span> erosion, potential evaporation, and soil water reserves. A field trial was conducted from 1985 to 1987 on 12 ha of a Psammentic Paleustalf in Southern Niger. Millet, Pennisetum glaucum (L.), and cowpea, Vigna unguiculata (L.) Walp., were seeded in strips on flat and ridged soil. Windbreaks of savannah vegetation were spaced atmore » 6, 20, 40, and 90 m. The effects of ridging on <span class="hlt">wind</span> <span class="hlt">speed</span>, evaporation, and <span class="hlt">wind</span> erosion were small and mostly non-significant. However, average <span class="hlt">wind</span> <span class="hlt">speed</span> at 0.3 m above ground in the center of cowpea and millet strips was significantly reduced from 2.8 to 2.1 m s[sup [minus]1] as windbreak distances narrowed from 90 to 6 m. As a consequence, potential evaporation declined by 15% and the amount of windblown soil particles by 50% in ridged and by 70% in flat treatments. Despite reduced potential evaporation, average subsoil water reserves were 14 mm smaller in the 6- than in the 20-m windbreak spacing indicating excessive water extraction by the windbreak vegetation. Thus, establishing windbreaks with natural savannah vegetation may require a careful consideration of the agronomic benefits and costs to competing crops. 21 refs., 5 figs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27457932','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27457932"><span>Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale <span class="hlt">wind</span> <span class="hlt">speed</span> and direction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yonehara, Yoshinari; Goto, Yusuke; Yoda, Ken; Watanuki, Yutaka; Young, Lindsay C; Weimerskirch, Henri; Bost, Charles-André; Sato, Katsufumi</p> <p>2016-08-09</p> <p>Ocean surface <span class="hlt">winds</span> are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface <span class="hlt">winds</span> measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of <span class="hlt">wind</span> that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface <span class="hlt">winds</span>. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground <span class="hlt">speed</span> fluctuated presumably due to tail <span class="hlt">winds</span> and head <span class="hlt">winds</span>. Taking advantage of the ground <span class="hlt">speed</span> difference in relation to flight direction, we reliably estimated <span class="hlt">wind</span> <span class="hlt">speed</span> and direction experienced by the birds. These bird-based <span class="hlt">wind</span> velocities were significantly correlated with <span class="hlt">wind</span> velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution <span class="hlt">wind</span> observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface <span class="hlt">winds</span>, potentially complementing conventional <span class="hlt">wind</span> measurements by covering spatial and temporal measurement gaps.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4987799','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4987799"><span>Flight paths of seabirds soaring over the ocean surface enable measurement of fine-scale <span class="hlt">wind</span> <span class="hlt">speed</span> and direction</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yonehara, Yoshinari; Goto, Yusuke; Yoda, Ken; Watanuki, Yutaka; Young, Lindsay C.; Weimerskirch, Henri; Bost, Charles-André; Sato, Katsufumi</p> <p>2016-01-01</p> <p>Ocean surface <span class="hlt">winds</span> are an essential factor in understanding the physical interactions between the atmosphere and the ocean. Surface <span class="hlt">winds</span> measured by satellite scatterometers and buoys cover most of the global ocean; however, there are still spatial and temporal gaps and finer-scale variations of <span class="hlt">wind</span> that may be overlooked, particularly in coastal areas. Here, we show that flight paths of soaring seabirds can be used to estimate fine-scale (every 5 min, ∼5 km) ocean surface <span class="hlt">winds</span>. Fine-scale global positioning system (GPS) positional data revealed that soaring seabirds flew tortuously and ground <span class="hlt">speed</span> fluctuated presumably due to tail <span class="hlt">winds</span> and head <span class="hlt">winds</span>. Taking advantage of the ground <span class="hlt">speed</span> difference in relation to flight direction, we reliably estimated <span class="hlt">wind</span> <span class="hlt">speed</span> and direction experienced by the birds. These bird-based <span class="hlt">wind</span> velocities were significantly correlated with <span class="hlt">wind</span> velocities estimated by satellite-borne scatterometers. Furthermore, extensive travel distances and flight duration of the seabirds enabled a wide range of high-resolution <span class="hlt">wind</span> observations, especially in coastal areas. Our study suggests that seabirds provide a platform from which to measure ocean surface <span class="hlt">winds</span>, potentially complementing conventional <span class="hlt">wind</span> measurements by covering spatial and temporal measurement gaps. PMID:27457932</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050199461','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050199461"><span>Abe Silverstein 10- by 10-Foot Supersonic <span class="hlt">Wind</span> Tunnel Validated for Low-<span class="hlt">Speed</span> (Subsonic) Operation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoffman, Thomas R.</p> <p>2001-01-01</p> <p>The NASA Glenn Research Center and Lockheed Martin Corporation tested an aircraft model in two <span class="hlt">wind</span> tunnels to compare low-<span class="hlt">speed</span> (subsonic) flow characteristics. Objectives of the test were to determine and document the similarities and uniqueness of the tunnels and to validate that Glenn's 10- by 10-Foot Supersonic <span class="hlt">Wind</span> Tunnel (10x10 SWT) is a viable low-<span class="hlt">speed</span> test facility. Results from two of Glenn's <span class="hlt">wind</span> tunnels compare very favorably and show that the 10x10 SWT is a viable low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel. The Subsonic Comparison Test was a joint effort by NASA and Lockheed Martin using the Lockheed Martin's Joint Strike Fighter Concept Demonstration Aircraft model. Although Glenn's 10310 and 836 SWT's have many similarities, they also have unique characteristics. Therefore, test data were collected for multiple model configurations at various vertical locations in the test section, starting at the test section centerline and extending into the ceiling and floor boundary layers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930044056&hterms=State+flow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DState%2Bflow','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930044056&hterms=State+flow&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3DState%2Bflow"><span>On radiating baroclinic instability of <span class="hlt">zonally</span> varying flow</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Finley, Catherine A.; Nathan, Terrence R.</p> <p>1993-01-01</p> <p>A quasi-geostrophic, two-layer, beta-plane model is used to study the baroclinic instability characteristics of a <span class="hlt">zonally</span> inhomogeneous flow. It is assumed that the disturbance varied slowly in the cross-stream direction, and the stability problem was formulated as a 1D initial value problem. Emphasis is placed on determining how the vertically averaged <span class="hlt">wind</span>, local maximum in vertical <span class="hlt">wind</span> shear, and length of the locally supercritical region combine to yield local instabilities. Analysis of the local disturbance energetics reveals that, for slowly varying basic states, the baroclinic energy conversion predominates within the locally unstable region. Using calculations of the basic state tendencies, it is shown that the net effect of the local instabilities is to redistribute energy from the baroclinic to the barotropic component of the basic state flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16319831','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16319831"><span>The vertical profile of <span class="hlt">winds</span> on Titan.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bird, M K; Allison, M; Asmar, S W; Atkinson, D H; Avruch, I M; Dutta-Roy, R; Dzierma, Y; Edenhofer, P; Folkner, W M; Gurvits, L I; Johnston, D V; Plettemeier, D; Pogrebenko, S V; Preston, R A; Tyler, G L</p> <p>2005-12-08</p> <p>One of Titan's most intriguing attributes is its copious but featureless atmosphere. The Voyager 1 fly-by and occultation in 1980 provided the first radial survey of Titan's atmospheric pressure and temperature and evidence for the presence of strong <span class="hlt">zonal</span> <span class="hlt">winds</span>. It was realized that the motion of an atmospheric probe could be used to study the <span class="hlt">winds</span>, which led to the inclusion of the Doppler <span class="hlt">Wind</span> Experiment on the Huygens probe. Here we report a high resolution vertical profile of Titan's <span class="hlt">winds</span>, with an estimated accuracy of better than 1 m s(-1). The <span class="hlt">zonal</span> <span class="hlt">winds</span> were prograde during most of the atmospheric descent, providing in situ confirmation of superrotation on Titan. A layer with surprisingly slow <span class="hlt">wind</span>, where the velocity decreased to near zero, was detected at altitudes between 60 and 100 km. Generally weak <span class="hlt">winds</span> (approximately 1 m s(-1)) were seen in the lowest 5 km of descent.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.7763G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.7763G"><span>The turbulence structure of katabatic flows below and above <span class="hlt">wind-speed</span> maximum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grachev, Andrey; Leo, Laura; Di Sabatino, Silvana; Fernando, Harindra; Pardyjak, Eric; Fairall, Christopher</p> <p>2015-04-01</p> <p>Measurements of atmospheric small-scale turbulence made over the complex-terrain at the US Army Dugway Proving Grounds in Utah during the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program are used to describe the turbulence structure of katabatic flows. Turbulent and mean meteorological data were continuously measured at multiple levels (up to seven) on four towers deployed along East lower slope (2-4 degrees) of Granite Mountain. The multi-level, multi-tower observations obtained during a 30-day long MATERHORN-Fall field campaign in September-October 2102 allow studying temporal and spatial structure of nocturnal slope flows in detail. In this study, we focus on the various statistics (fluxes, variances, spectra, cospectra, etc.) of the small-scale turbulence of katabatic <span class="hlt">winds</span>. Observed vertical profiles of velocity, turbulent fluxes, and other quantities show steep gradients near the surface but in the layer above the slope jet these variables vary with height more slowly than near the surface. It is found that vertical momentum flux and horizontal heat (buoyancy) flux in a slope-following coordinate system change their sign below and above the <span class="hlt">wind</span> maximum of a katabatic flow. The vertical momentum flux is directed downward (upward) whereas the horizontal heat flux is downslope (upslope) below (above) the <span class="hlt">wind</span> maximum. Our study, therefore, suggests that a position of the jet <span class="hlt">speed</span> maximum can be derived from linear interpolation between positive and negative values of the momentum flux (or the horizontal heat flux) and determination of a height where a flux becomes zero. It is shown that the standard deviations of all <span class="hlt">wind</span> <span class="hlt">speed</span> components (and therefore the turbulent kinetic energy) and the dissipation rate of turbulent kinetic energy have a local minimum, whereas the standard deviation of air temperature has an absolute maximum at the height of <span class="hlt">wind</span> <span class="hlt">speed</span> maximum. We report several cases when the destructive effect of vertical heat</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000085897','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000085897"><span>Comparison Between Sea Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> Estimates From Reflected GPS Signals and Buoy Measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Garrison, James L.; Katzberg, Steven J.; Zavorotny, Valery U.</p> <p>2000-01-01</p> <p>Reflected signals from the Global Positioning System (GPS) have been collected from an aircraft at approximately 3.7 km altitude on 5 different days. Estimation of surface <span class="hlt">wind</span> <span class="hlt">speed</span> by matching the shape of the reflected signal correlation function against analytical models was demonstrated. <span class="hlt">Wind</span> <span class="hlt">speed</span> obtained from this method agreed with that recorded from buoys to with a bias of less than 0.1 m/s, and with a standard derivation of 1.3 meters per second.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005IJBm...49..139D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005IJBm...49..139D"><span>Transport of airborne pollen into the city of Thessaloniki: the effects of <span class="hlt">wind</span> direction, <span class="hlt">speed</span> and persistence</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Damialis, Athanasios; Gioulekas, Dimitrios; Lazopoulou, Chariklia; Balafoutis, Christos; Vokou, Despina</p> <p>2005-01-01</p> <p>We examined the effect of the <span class="hlt">wind</span> vector analyzed into its three components (direction, <span class="hlt">speed</span> and persistence), on the circulation of pollen from differe nt plant taxa prominent in the Thessaloniki area for a 4-year period (1996- 1999). These plant taxa were Ambrosia spp., Artemisia spp., Chenopodiaceae, spp., Cupressaceae, Olea europaea, Pinaceae, Platanus spp., Poaceae, Populus spp., Quercus spp., and Urticaceae. Airborne pollen of Cupressaceae, Urticaceae, Quercus spp. and O. europaea make up approximately 70% of the total average annual pollen counts. The set of data that we worked with represented days without precipitation and time intervals during which <span class="hlt">winds</span> blew from the same direction for at least 4 consecutive hours. We did this in order to study the effect of the different <span class="hlt">wind</span> components independently of precipitation, and to avoid secondary effects produced by pollen resuspension phenomena. Factorial regression analysis among the summed bi-hourly pollen counts for each taxon and the values of <span class="hlt">wind</span> <span class="hlt">speed</span> and persistence per <span class="hlt">wind</span> direction gave significant results in 22 cases (combinations of plant taxa and <span class="hlt">wind</span> directions). The pollen concentrations of all taxa correlated significantly with at least one of the three <span class="hlt">wind</span> components. In seven out of the 22 taxon-<span class="hlt">wind</span> direction combinations, the pollen counts correlated positively with <span class="hlt">wind</span> persistence, whereas this was the case for only two of the taxon-<span class="hlt">wind</span> <span class="hlt">speed</span> combinations. In seven cases, pollen counts correlated with the interaction effect of <span class="hlt">wind</span> <span class="hlt">speed</span> and persistence. This shows the importance of <span class="hlt">wind</span> persistence in pollen transport, particularly when weak <span class="hlt">winds</span> prevail for a considerable part of the year, as is the case for Thessaloniki. Medium/long-distance pollen transport was evidenced for Olea (NW, SW directions), Corylus (NW, SW), Poaceae (SW) and Populus (NW).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790041961&hterms=Electromagnetic+Spectrum&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DElectromagnetic%2BSpectrum','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790041961&hterms=Electromagnetic+Spectrum&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DElectromagnetic%2BSpectrum"><span>Proton-driven electromagnetic instabilities in high-<span class="hlt">speed</span> solar <span class="hlt">wind</span> streams</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Abraham-Shrauner, B.; Asbridge, J. R.; Bame, S. J.; Feldman, W. C.</p> <p>1979-01-01</p> <p>Electromagnetic instabilities of the field-aligned, right-hand circularly polarized magnetosonic wave and the left-hand circularly polarized Alfven wave driven by two drifted proton components are analyzed for model parameters determined from Imp 7 solar <span class="hlt">wind</span> proton data measured during high-<span class="hlt">speed</span> flow conditions. Growth rates calculated using bi-Lorentzian forms for the main and beam proton as well as core and halo electron velocity distributions do not differ significantly from those calculated using bi-Maxwellian forms. Using distribution parameters determined from 17 measured proton spectra, we show that considering the uncertainties the magnetosonic wave may be linearly stable and the Alfven wave is linearly unstable. Because proton velocity distribution function shapes are observed to persist for times long compared to the proton gyroperiod, the latter result suggests that linear stability theory fails for proton-driven ion cyclotron waves in the high-<span class="hlt">speed</span> solar <span class="hlt">wind</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..12212378H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..12212378H"><span>The Relationship of High-Latitude Thermospheric <span class="hlt">Wind</span> With Ionospheric Horizontal Current, as Observed by CHAMP Satellite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huang, Tao; Lühr, Hermann; Wang, Hui; Xiong, Chao</p> <p>2017-12-01</p> <p>The relationship between high-latitude ionospheric currents (Hall current and field-aligned current) and thermospheric <span class="hlt">wind</span> is investigated. The 2-D patterns of horizontal <span class="hlt">wind</span> 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 <span class="hlt">wind</span> velocity patterns. The duskside <span class="hlt">wind</span> vortex as well as the antisunward <span class="hlt">wind</span> 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 <span class="hlt">zonal</span> <span class="hlt">wind</span> and equivalent current are anticorrelated, and both of them form a vortical flow pattern for different activity levels. The currents and <span class="hlt">zonal</span> <span class="hlt">wind</span> are intensified with the increase of merging electric field. However, on the dawnside, where the relation is less clear, antisunward <span class="hlt">zonal</span> <span class="hlt">winds</span> dominate. Plasma drift seems to play a less important role for the <span class="hlt">wind</span> than neutral forces in this sector. In the noon sector, the best anticorrelation between equivalent current and <span class="hlt">wind</span> 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 <span class="hlt">zonal</span> <span class="hlt">wind</span> intensity shows little dependence on seasons. Our results indicate that the plasma drift and the neutral forces are of comparable influence on the <span class="hlt">zonal</span> <span class="hlt">wind</span> at CHAMP altitude in the noon sector.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013MS%26E...52e2011E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013MS%26E...52e2011E"><span>Statistical analysis of low frequency vibrations in variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbines</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Escaler, X.; Mebarki, T.</p> <p>2013-12-01</p> <p>The spectral content of the low frequency vibrations in the band from 0 to 10 Hz measured in full scale <span class="hlt">wind</span> turbines has been statistically analyzed as a function of the whole range of steady operating conditions. Attention has been given to the amplitudes of the vibration peaks and their dependency on rotating <span class="hlt">speed</span> and power output. Two different <span class="hlt">wind</span> turbine models of 800 and 2000 kW have been compared. For each model, a sample of units located in the same <span class="hlt">wind</span> farm and operating during a representative period of time have been considered. A condition monitoring system installed in each <span class="hlt">wind</span> turbine has been used to register the axial acceleration on the gearbox casing between the intermediate and the high <span class="hlt">speed</span> shafts. The average frequency spectrum has permitted to identify the vibration signature and the position of the first tower natural frequency in both models. The evolution of the vibration amplitudes at the rotor rotating frequency and its multiples has shown that the tower response is amplified by resonance conditions in one of the models. So, it is concluded that a continuous measurement and control of low frequency vibrations is required to protect the turbines against harmful vibrations of this nature.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22654136-role-coronal-alfven-speed-modulating-solar-wind-helium-abundance','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22654136-role-coronal-alfven-speed-modulating-solar-wind-helium-abundance"><span>ROLE OF THE CORONAL ALFVÉN <span class="hlt">SPEED</span> IN MODULATING THE SOLAR-<span class="hlt">WIND</span> HELIUM ABUNDANCE</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wang, Y.-M., E-mail: yi.wang@nrl.navy.mil</p> <p></p> <p>The helium abundance He/H in the solar <span class="hlt">wind</span> is relatively constant at ∼0.04 in high-<span class="hlt">speed</span> streams, but varies in phase with the sunspot number in slow <span class="hlt">wind</span>, from ∼0.01 at solar minimum to ∼0.04 at maximum. Suggested mechanisms for helium fractionation have included frictional coupling to protons and resonant interactions with high-frequency Alfvénic fluctuations. We compare He/H measurements during 1995–2015 with coronal parameters derived from source-surface extrapolations of photospheric field maps. We find that the near-Earth helium abundance is an increasing function of the magnetic field strength and Alfvén <span class="hlt">speed</span> v {sub A} in the outer corona, while being onlymore » weakly correlated with the proton flux density. Throughout the solar cycle, fast <span class="hlt">wind</span> is associated with short-term increases in v {sub A} near the source surface; resonance with Alfvén waves, with v {sub A} and the relative <span class="hlt">speed</span> of α -particles and protons decreasing with increasing heliocentric distance, may then lead to enhanced He/H at 1 au. The modulation of helium in slow <span class="hlt">wind</span> reflects the tendency for the associated coronal Alfvén <span class="hlt">speeds</span> to rise steeply from sunspot minimum, when this <span class="hlt">wind</span> is concentrated around the source-surface neutral line, to sunspot maximum, when the source-surface field attains its peak strengths. The helium abundance near the source surface may represent a balance between collisional decoupling from protons and Alfvén wave acceleration.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFMGC13K0885Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFMGC13K0885Z"><span>The Influence of Spatial Resolutions on the Retrieval Accuracy of Sea Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> with Cross-polarized C-band SAR images</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, K.; Han, B.; Mansaray, L. R.; Xu, X.; Guo, Q.; Jingfeng, H.</p> <p>2017-12-01</p> <p>Synthetic aperture radar (SAR) instruments on board satellites are valuable for high-resolution <span class="hlt">wind</span> field mapping, especially for coastal studies. Since the launch of Sentinel-1A on April 3, 2014, followed by Sentinel-1B on April 25, 2016, large amount of C-band SAR data have been added to a growing accumulation of SAR datasets (ERS-1/2, RADARSAT-1/2, ENVISAT). These new developments are of great significance for a wide range of applications in coastal sea areas, especially for high spatial resolution <span class="hlt">wind</span> resource assessment, in which the accuracy of retrieved <span class="hlt">wind</span> fields is extremely crucial. Recently, it is reported that <span class="hlt">wind</span> <span class="hlt">speeds</span> can also be retrieved from C-band cross-polarized SAR images, which is an important complement to <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval from co-polarization. However, there is no consensus on the optimal resolution for <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval from cross-polarized SAR images. This paper presents a comparison strategy for investigating the influence of spatial resolutions on sea surface <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval accuracy with cross-polarized SAR images. Firstly, for <span class="hlt">wind</span> <span class="hlt">speeds</span> retrieved from VV-polarized images, the optimal geophysical C-band model (CMOD) function was selected among four CMOD functions. Secondly, the most suitable C-band cross-polarized ocean (C-2PO) model was selected between two C-2POs for the VH-polarized image dataset. Then, the VH-<span class="hlt">wind</span> <span class="hlt">speeds</span> retrieved by the selected C-2PO were compared with the VV-polarized sea surface <span class="hlt">wind</span> <span class="hlt">speeds</span> retrieved using the optimal CMOD, which served as reference, at different spatial resolutions. Results show that the VH-polarized <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval accuracy increases rapidly with the decrease in spatial resolutions from 100 m to 1000 m, with a drop in RMSE of 42%. However, the improvement in <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval accuracy levels off with spatial resolutions decreasing from 1000 m to 5000 m. This demonstrates that the pixel spacing of 1 km may be the compromising choice for the tradeoff between the spatial</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014BoLMe.150..381W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014BoLMe.150..381W"><span>Numerical Simulations of Laminar Air-Water Flow of a Non-linear Progressive Wave at Low <span class="hlt">Wind</span> <span class="hlt">Speed</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wen, X.; Mobbs, S.</p> <p>2014-03-01</p> <p>A numerical simulation for two-dimensional laminar air-water flow of a non-linear progressive water wave with large steepness is performed when the background <span class="hlt">wind</span> <span class="hlt">speed</span> varies from zero to the wave phase <span class="hlt">speed</span>. It is revealed that in the water the difference between the analytical solution of potential flow and numerical solution of viscous flow is very small, indicating that both solutions of the potential flow and viscous flow describe the water wave very accurately. In the air the solutions of potential and viscous flows are very different due to the effects of viscosity. The velocity distribution in the airflow is strongly influenced by the background <span class="hlt">wind</span> <span class="hlt">speed</span> and it is found that three <span class="hlt">wind</span> <span class="hlt">speeds</span>, , (the maximum orbital velocity of a water wave), and (the wave phase <span class="hlt">speed</span>), are important in distinguishing different features of the flow patterns.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19880005129','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19880005129"><span><span class="hlt">Wind</span> regime peculiarities in the lower thermosphere in the winter of 1983/84</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lysenko, I. A.; Makarov, N. A.; Portnyagin, Yu. I.; Petrov, B. I.; Greisiger, K. M.; Schminder, R.; Kurschner, D.</p> <p>1987-01-01</p> <p>Temporal variations of prevailing <span class="hlt">winds</span> at 90 to 100 km obtained from measurements carried out in winter 1983 to 1984 at three sites in the USSR and two sites in East Germany are reported. These variations are compared with those of the thermal stratospheric regime. Measurements were carried out using the drifts D2 method (meteor <span class="hlt">wind</span> radar) and the D1 method (ionospheric drifts). Temporal variations of <span class="hlt">zonal</span> and meridional prevailing <span class="hlt">wind</span> components for all the sites are given. Also presented are <span class="hlt">zonal</span> <span class="hlt">wind</span> data obtained using the partial reflection <span class="hlt">wind</span> radar. <span class="hlt">Wind</span> velocity values were obtained by averaging data recorded at between 105 and 91 km altitude. <span class="hlt">Wind</span> velocity data averaged in such a way can be related to about the same height interval to which the data obtained by the meteor radar and ionospheric methods at other sites, i.e., the mean height of the meteor zone (about 95 km). The results presented show that there are significant fluctuations about the seasonal course of both <span class="hlt">zonal</span> and meridional prevailing <span class="hlt">winds</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20170009793','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20170009793"><span>Observed Trend in Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> Over the Conterminous USA and CMIP5 Simulations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hashimoto, Hirofumi; Nemani, Ramakrishna R.</p> <p>2016-01-01</p> <p>There has been no spatial surface <span class="hlt">wind</span> map even over the conterminous USA due to the difficulty of spatial interpolation of <span class="hlt">wind</span> field. As a result, the reanalysis data were often used to analyze the statistics of spatial pattern in surface <span class="hlt">wind</span> <span class="hlt">speed</span>. Unfortunately, no consistent trend in <span class="hlt">wind</span> field was found among the available reanalysis data, and that obstructed the further analysis or projection of spatial pattern of <span class="hlt">wind</span> <span class="hlt">speed</span>. In this study, we developed the methodology to interpolate the observed <span class="hlt">wind</span> <span class="hlt">speed</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4095901','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4095901"><span>High-fidelity simulations of unsteady civil aircraft aerodynamics: stakes and perspectives. Application of <span class="hlt">zonal</span> detached eddy simulation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Deck, Sébastien; Gand, Fabien; Brunet, Vincent; Ben Khelil, Saloua</p> <p>2014-01-01</p> <p>This paper provides an up-to-date survey of the use of <span class="hlt">zonal</span> detached eddy simulations (ZDES) for unsteady civil aircraft applications as a reflection on the stakes and perspectives of the use of hybrid methods in the framework of industrial aerodynamics. The issue of <span class="hlt">zonal</span> or non-<span class="hlt">zonal</span> treatment of turbulent flows for engineering applications is discussed. The ZDES method used in this article and based on a fluid problem-dependent <span class="hlt">zonalization</span> is briefly presented. Some recent landmark achievements for conditions all over the flight envelope are presented, including low-<span class="hlt">speed</span> (aeroacoustics of high-lift devices and landing gear), cruising (engine–airframe interactions), propulsive jets and off-design (transonic buffet and dive manoeuvres) applications. The implications of such results and remaining challenges in a more global framework are further discussed. PMID:25024411</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=365845','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=365845"><span>Isolation of Intact Chloroplasts from Euglena gracilis by <span class="hlt">Zonal</span> Centrifugation 1</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vasconcelos, Aurea; Pollack, Marilyn; Mendiola, Leticia R.; Hoffmann, H.-P.; Brown, D. H.; Price, C. A.</p> <p>1971-01-01</p> <p>Chloroplasts were separated from Euglena gracilis by <span class="hlt">zonal</span> centrifugation at low <span class="hlt">speed</span> in density gradients of Ficoll or dextran. The chloroplasts were intact by the criteria of ultrastructure and their content of ribulose diphosphate carboxylase and soluble protein. The chloroplasts also contained ribosomes and ribosomal RNA uncontaminated by the corresponding cytoplasmic particles. Images PMID:16657599</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930090989','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930090989"><span>A Free-flight <span class="hlt">Wind</span> Tunnel for Aerodynamic Testing at Hypersonic <span class="hlt">Speeds</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Seiff, Alvin</p> <p>1954-01-01</p> <p>The supersonic free-flight <span class="hlt">wind</span> tunnel is a facility at the Ames Laboratory of the NACA in which aerodynamic test models are gun-launched at high <span class="hlt">speed</span> and directed upstream through the test section of a supersonic <span class="hlt">wind</span> tunnel. In this way, test Mach numbers up to 10 have been attained and indications are that still higher <span class="hlt">speeds</span> will be realized. An advantage of this technique is that the air and model temperatures simulate those of flight through the atmosphere. Also the Reynolds numbers are high. Aerodynamic measurements are made from photographic observation of the model flight. Instruments and techniques have been developed for measuring the following aerodynamic properties: drag, initial lift-curve slope, initial pitching-moment-curve slope, center of pressure, skin friction, boundary-layer transition, damping in roll, and aileron effectiveness. (author)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050147488&hterms=saber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsaber','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050147488&hterms=saber&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsaber"><span><span class="hlt">Zonal</span>-Mean Temperature Variations Inferred from SABER Measurements on TIMED Compared with UARS Observations</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Huang, Frank T.; Mayr, Hans; Russell, James; Mlynczak, Marty; Reber, Carl A.</p> <p>2005-01-01</p> <p>In the Numerical Spectral Model (NSM, Mayr et al., 2003), small-scale gravity waves propagating in the north/south direction can generate <span class="hlt">zonal</span> mean (m = 0) meridional <span class="hlt">wind</span> oscillations with periods between 2 and 4 months. These oscillations tend to be confined to low latitudes and have been interpreted to be the meridional counterpart of the wave-driven Quasi Biennial Oscillation in the <span class="hlt">zonal</span> circulation. Wave driven meridional <span class="hlt">winds</span> across the equator should generate, due to dynamical heating and cooling, temperature oscillations with opposite phase in the two hemispheres. We have analyzed SABER temperature measurements in the altitude range between 55 and 95 km to investigate the existence such variations. Because there are also strong tidal signatures (up to approximately 20 K) in the data, our algorithm estimates both mean values and tides together from the data. Based on SABER temperature data, the intra-annual variations with periods between 2 and 4 months can have amplitudes up to 5 K or more, depending on the altitude. Their amplitudes are in qualitative agreement with those inferred Erom UARS data (from different years). The SABER temperature variations also reveal pronounced hemispherical asymmetries, which are qualitatively consistent with wave driven meridional <span class="hlt">wind</span> oscillations across the equator. Oscillations with similar periods have been seen in the meridional <span class="hlt">winds</span> based on UARS data (Huang and Reber, 2003).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MeScT..26i5305B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MeScT..26i5305B"><span>Pulse-burst PIV in a high-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Beresh, Steven; Kearney, Sean; Wagner, Justin; Guildenbecher, Daniel; Henfling, John; Spillers, Russell; Pruett, Brian; Jiang, Naibo; Slipchenko, Mikhail; Mance, Jason; Roy, Sukesh</p> <p>2015-09-01</p> <p>Time-resolved particle image velocimetry (TR-PIV) has been achieved in a high-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel, providing velocity field movies of compressible turbulence events. The requirements of high-<span class="hlt">speed</span> flows demand greater energy at faster pulse rates than possible with the TR-PIV systems developed for low-<span class="hlt">speed</span> flows. This has been realized using a pulse-burst laser to obtain movies at up to 50 kHz, with higher <span class="hlt">speeds</span> possible at the cost of spatial resolution. The constraints imposed by use of a pulse-burst laser are limited burst duration of 10.2 ms and a low duty cycle for data acquisition. Pulse-burst PIV has been demonstrated in a supersonic jet exhausting into a transonic crossflow and in transonic flow over a rectangular cavity. The velocity field sequences reveal the passage of turbulent structures and can be used to find velocity power spectra at every point in the field, providing spatial distributions of acoustic modes. The present work represents the first use of TR-PIV in a high-<span class="hlt">speed</span> ground-test facility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MAP...130..311L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MAP...130..311L"><span>The impact of urbanization on <span class="hlt">wind</span> <span class="hlt">speed</span> and surface aerodynamic characteristics in Beijing during 1991-2011</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liu, Junkai; Gao, Zhiqiu; Wang, Linlin; Li, Yubin; Gao, Chloe Y.</p> <p>2018-06-01</p> <p>Urbanization has a significant influence on climate and meteorological conditions through altering surface aerodynamic characteristics. Based on observational data collected at 15 levels on a 325 m meteorological tower in Beijing during 1991-2011, changes in <span class="hlt">wind</span> <span class="hlt">speed</span>, vertical profile, aerodynamic roughness length (z0), and zero-plane displacement height (zd) were analyzed. Decreasing trends were observed predominantly during this period, especially for levels between 65 and 140 m where the largest decreasing rates often occur. The annual and seasonal (spring, summer, autumn, and winter) mean <span class="hlt">wind</span> <span class="hlt">speeds</span> at 15 levels all present decreasing trends with average rates of 0.029, 0.024, 0.023, 0.040, and 0.019 m s-1 a-1, respectively. The decreases in strong <span class="hlt">wind</span> categories contribute most to the reduction of mean <span class="hlt">wind</span> <span class="hlt">speed</span>. Furthermore, in 2005-2011, the diurnal maximum <span class="hlt">wind</span> <span class="hlt">speeds</span> at lower levels tend to appear earlier as compared to those in 1991-1997, while the patterns of diurnal cycle between different levels become more similar in these periods. Besides, the phenomena of "kink" in <span class="hlt">wind</span> profiles are visible in various atmospheric stabilities, and the average height of a kink has increased from about 40 m to nearly 80 m associated with urbanization during 1991-2011. In addition, the results of z0 and zd calculated using the <span class="hlt">wind</span> profile method vary with <span class="hlt">wind</span> directions due to surface heterogeneity and that larger values often occur along with southerly <span class="hlt">winds</span>. Both z0 and zd show increasing trends in different sectors during 1991-2011, and the annual mean z0 and zd have increased from less than 1 m to greater than 2 m, and from less than 10 m to greater than 20 m, respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6721191-experiments-tropical-stratospheric-mean-wind-variations-spectral-general-circulation-model','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6721191-experiments-tropical-stratospheric-mean-wind-variations-spectral-general-circulation-model"><span>Experiments on tropical stratospheric mean-<span class="hlt">wind</span> variations in a spectral general circulation model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Hamilton, K.; Yuan, L.</p> <p>1992-12-15</p> <p>A 30-level version of the rhomboidal-15 GFDL spectral climate model was constructed with roughly 2-km vertical resolution. This model fails to produce a realistic quasi-biennial oscillation (QBO) in the tropical stratosphere. Several simulations were conducted in which the <span class="hlt">zonal</span>-mean <span class="hlt">winds</span> and temperatures in the equatorial lower and middle stratosphere were instantaneously perturbed and the model was integrated while the mean state relaxed toward its equilibrium. The time scale for the mean <span class="hlt">wind</span> relaxation varied from over one month at 40 km to a few months in the lower stratosphere. The <span class="hlt">wind</span> relaxations in the model also displayed the downward phasemore » propagation characteristic of QBO <span class="hlt">wind</span> reversals, and mean <span class="hlt">wind</span> anomalies of opposite sign to the imposed perturbation appear at higher levels. In the GCM the downward propagation is clear only above about 20 mb. Detailed investigations were made of the <span class="hlt">zonal</span>-mean <span class="hlt">zonal</span> momentum budget in the equatorial stratosphere. The mean flow relaxations above 20 mb were mostly driven by the vertical Eliassen-Palm flux convergence. The anomalies in the horizontal Eliassen-Palm fluxes from extratropical planetary waves were found to be the dominant effect forcing the mean flow to its equilibrium at altitudes below 20 mb. The vertical eddy momentum fluxes near the equator in the model were decomposed using space-time Fourier analysis. While total fluxes associated with easterly and westerly waves are comparable to those used in simple mechanistic models of the QBO, the GCM has its flux spread over a broad range of wavenumbers and phase <span class="hlt">speeds</span>. The effects of vertical resolution were studied by repeating part of the control integration with a 69-level version of the model with greatly enhance vertical resolution in the lower and middle stratosphere. The results showed that there is almost no sensitivity of the simulation in the tropical stratosphere to the increased vertical resolution. 34 refs., 16 figs., 3 tabs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950033274&hterms=atmosphere+wind+profile&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Datmosphere%2Bwind%2Bprofile','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950033274&hterms=atmosphere+wind+profile&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Datmosphere%2Bwind%2Bprofile"><span>Zero potential vorticity envelopes for the <span class="hlt">zonal</span>-mean velocity of the Venus/Titan atmospheres</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Allison, Michael; Del Genio, Anthony D.; Zhou, Wei</p> <p>1994-01-01</p> <p>The diagnostic analysis of numerical simulations of the Venus/Titan <span class="hlt">wind</span> regime reveals an overlooked constraint upon the latitudinal structure of their <span class="hlt">zonal</span>-mean angular momentum. The numerical experiments, as well as the limited planetary observations, are approximately consistent with the hypothesis that within the latitudes bounded by the <span class="hlt">wind</span> maxima the total Ertel potential vorticity associated with the <span class="hlt">zonal</span>-mean motion is approximately well mixed with respect to the neutral equatorial value for a stable circulation. The implied latitudinal profile of angular momentum is of the form M equal to or less than M(sub e)(cos lambda)(exp 2/Ri), where lambda is the latitude and Ri the local Richardson number, generally intermediate between the two extremes of uniform angular momentum (Ri approaches infinity) and uniform angular velocity (Ri = 1). The full range of angular momentum profile variation appears to be realized within the observed meridional - vertical structure of the Venus atmosphere, at least crudely approaching the implied relationship between stratification and <span class="hlt">zonal</span> velocity there. While not itself indicative of a particular eddy mechanism or specific to atmospheric superrotation, the zero potential vorticity (ZPV) constraint represents a limiting bound for the eddy - mean flow adjustment of a neutrally stable baroclinic circulation and may be usefully applied to the diagnostic analysis of future remote sounding and in situ measurements from planetary spacecraft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28701505','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28701505"><span>Remotely sensed <span class="hlt">wind</span> <span class="hlt">speed</span> predicts soaring behaviour in a wide-ranging pelagic seabird.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gibb, Rory; Shoji, Akiko; Fayet, Annette L; Perrins, Chris M; Guilford, Tim; Freeman, Robin</p> <p>2017-07-01</p> <p>Global <span class="hlt">wind</span> patterns affect flight strategies in many birds, including pelagic seabirds, many of which use <span class="hlt">wind</span>-powered soaring to reduce energy costs during at-sea foraging trips and migration. Such long-distance movement patterns are underpinned by local interactions between <span class="hlt">wind</span> conditions and flight behaviour, but these fine-scale relationships are far less well understood. Here we show that remotely sensed ocean <span class="hlt">wind</span> <span class="hlt">speed</span> and direction are highly significant predictors of soaring behaviour in a migratory pelagic seabird, the Manx shearwater ( Puffinus puffinus ). We used high-frequency GPS tracking data (10 Hz) and statistical behaviour state classification to identify two energetic modes in at-sea flight, corresponding to flap-like and soar-like flight. We show that soaring is significantly more likely to occur in tailwinds and crosswinds above a <span class="hlt">wind</span> <span class="hlt">speed</span> threshold of around 8 m s -1 , suggesting that these conditions enable birds to reduce metabolic costs by preferentially soaring over flapping. Our results suggest a behavioural mechanism by which <span class="hlt">wind</span> conditions may shape foraging and migration ecology in pelagic seabirds, and thus indicate that shifts in <span class="hlt">wind</span> patterns driven by climate change could impact this and other species. They also emphasize the emerging potential of high-frequency GPS biologgers to provide detailed quantitative insights into fine-scale flight behaviour in free-living animals. © 2017 The Author(s).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...833L..21W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...833L..21W"><span>Role of the Coronal Alfvén <span class="hlt">Speed</span> in Modulating the Solar-<span class="hlt">wind</span> Helium Abundance</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, Y.-M.</p> <p>2016-12-01</p> <p>The helium abundance He/H in the solar <span class="hlt">wind</span> is relatively constant at ˜0.04 in high-<span class="hlt">speed</span> streams, but varies in phase with the sunspot number in slow <span class="hlt">wind</span>, from ˜0.01 at solar minimum to ˜0.04 at maximum. Suggested mechanisms for helium fractionation have included frictional coupling to protons and resonant interactions with high-frequency Alfvénic fluctuations. We compare He/H measurements during 1995-2015 with coronal parameters derived from source-surface extrapolations of photospheric field maps. We find that the near-Earth helium abundance is an increasing function of the magnetic field strength and Alfvén <span class="hlt">speed</span> v A in the outer corona, while being only weakly correlated with the proton flux density. Throughout the solar cycle, fast <span class="hlt">wind</span> is associated with short-term increases in v A near the source surface; resonance with Alfvén waves, with v A and the relative <span class="hlt">speed</span> of α-particles and protons decreasing with increasing heliocentric distance, may then lead to enhanced He/H at 1 au. The modulation of helium in slow <span class="hlt">wind</span> reflects the tendency for the associated coronal Alfvén <span class="hlt">speeds</span> to rise steeply from sunspot minimum, when this <span class="hlt">wind</span> is concentrated around the source-surface neutral line, to sunspot maximum, when the source-surface field attains its peak strengths. The helium abundance near the source surface may represent a balance between collisional decoupling from protons and Alfvén wave acceleration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050176059','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050176059"><span>Nature and Variability of Coronal Streamers and their Relationship to the Slow <span class="hlt">Speed</span> <span class="hlt">Wind</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Strachan, Leonard</p> <p>2005-01-01</p> <p>NASA Grant NAG5-12781 is a study on the "Nature and Variability of Coronal Streamers and their Relationship to the Slow <span class="hlt">Speed</span> <span class="hlt">Wind</span>." The two main goals of this study are to identify: 1) Where in the streamer structure does the solar <span class="hlt">wind</span> originate, and 2) What coronal conditions are responsible for the variability of the slow <span class="hlt">speed</span> <span class="hlt">wind</span>. To answer the first question, we examined the mostly closed magnetic field regions in streamer cores to search for evidence of outflow. Preliminary results from the OVI Doppler dimming ratios indicates that most of the flow originates from the edges of coronal streamers but this idea should be confirmed by a comparison of the coronal plasma properties with in situ solar <span class="hlt">wind</span> data. To answer the second question, the work performed thus far suggests that solar minimum streamers have larger perpendicular velocity distributions than do solar maximum streamers. If it can be shown that solar minimum streamers also produce higher solar <span class="hlt">wind</span> <span class="hlt">speeds</span> then this would suggest that streamers and coronal holes have similar solar <span class="hlt">wind</span> acceleration mechanisms. The key to both questions lie in the analysis of the in situ solar <span class="hlt">wind</span> data sets. This work was not able to be completed during the period of performance and therefore the grant was formally extended for an additional year at no cost to NASA. We hope to have final results and a publication by the end of the calendar year 2004. The SAO personnel involved in the research are Leonard Strachan (PI), Mari Paz Miralles, Alexander Panasyuk, and a Southern University student Michael Baham.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130010684','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130010684"><span>Statistical Short-Range Guidance for Peak <span class="hlt">Wind</span> <span class="hlt">Speed</span> Forecasts at Edwards Air Force Base, CA</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dreher, Joseph; Crawford, Winifred; Lafosse, Richard; Hoeth, Brian; Burns, Kerry</p> <p>2008-01-01</p> <p>The peak <span class="hlt">winds</span> near the surface are an important forecast element for Space Shuttle landings. As defined in the Shuttle Flight Rules (FRs), there are peak <span class="hlt">wind</span> thresholds that cannot be exceeded in order to ensure the safety of the shuttle during landing operations. The National Weather Service Spaceflight Meteorology Group (SMG) is responsible for weather forecasts for all shuttle landings. They indicate peak <span class="hlt">winds</span> are a challenging parameter to forecast. To alleviate the difficulty in making such <span class="hlt">wind</span> forecasts, the Applied Meteorology Unit (AMTJ) developed a personal computer based graphical user interface (GUI) for displaying peak <span class="hlt">wind</span> climatology and probabilities of exceeding peak-<span class="hlt">wind</span> thresholds for the Shuttle Landing Facility (SLF) at Kennedy Space Center. However, the shuttle must land at Edwards Air Force Base (EAFB) in southern California when weather conditions at Kennedy Space Center in Florida are not acceptable, so SMG forecasters requested that a similar tool be developed for EAFB. Marshall Space Flight Center (MSFC) personnel archived and performed quality control of 2-minute average and 10-minute peak <span class="hlt">wind</span> <span class="hlt">speeds</span> at each tower adjacent to the main runway at EAFB from 1997- 2004. They calculated <span class="hlt">wind</span> climatologies and probabilities of average peak <span class="hlt">wind</span> occurrence based on the average <span class="hlt">speed</span>. The climatologies were calculated for each tower and month, and were stratified by hour, direction, and direction/hour. For the probabilities of peak <span class="hlt">wind</span> occurrence, MSFC calculated empirical and modeled probabilities of meeting or exceeding specific 10-minute peak <span class="hlt">wind</span> <span class="hlt">speeds</span> using probability density functions. The AMU obtained and reformatted the data into Microsoft Excel PivotTables, which allows users to display different values with point-click-drag techniques. The GUT was then created from the PivotTables using Visual Basic for Applications code. The GUI is run through a macro within Microsoft Excel and allows forecasters to quickly display and</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.2503S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.2503S"><span>Disturbance <span class="hlt">zonal</span> and vertical plasma drifts in the Peruvian sector during solar minimum phases</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Santos, A. M.; Abdu, M. A.; Souza, J. R.; Sobral, J. H. A.; Batista, I. S.</p> <p>2016-03-01</p> <p>In the present work, we investigate the behavior of the equatorial F region <span class="hlt">zonal</span> plasma drifts over the Peruvian region under magnetically disturbed conditions during two solar minimum epochs, one of them being the recent prolonged solar activity minimum. The study utilizes the vertical and <span class="hlt">zonal</span> components of the plasma drifts measured by the Jicamarca (11.95°S; 76.87°W) incoherent scatter radar during two events that occurred on 10 April 1997 and 24 June 2008 and model calculation of the <span class="hlt">zonal</span> drift in a realistic ionosphere simulated by the Sheffield University Plasmasphere-Ionosphere Model-INPE. Two main points are focused: (1) the connection between electric fields and plasma drifts under prompt penetration electric field during a disturbed periods and (2) anomalous behavior of daytime <span class="hlt">zonal</span> drift in the absence of any magnetic storm. A perfect anticorrelation between vertical and <span class="hlt">zonal</span> drifts was observed during the night and in the initial and growth phases of the magnetic storm. For the first time, based on a realistic low-latitude ionosphere, we will show, on a detailed quantitative basis, that this anticorrelation is driven mainly by a vertical Hall electric field induced by the primary <span class="hlt">zonal</span> electric field in the presence of an enhanced nighttime E region ionization. It is shown that an increase in the field line-integrated Hall-to-Pedersen conductivity ratio (∑H/∑P), which can arise from precipitation of energetic particles in the region of the South American Magnetic Anomaly, is capable of explaining the observed anticorrelation between the vertical and <span class="hlt">zonal</span> plasma drifts. Evidence for the particle ionization is provided from the occurrence of anomalous sporadic E layers over the low-latitude station, Cachoeira Paulista (22.67°S; 44.9°W)—Brazil. It will also be shown that the <span class="hlt">zonal</span> plasma drift reversal to eastward in the afternoon two hours earlier than its reference quiet time pattern is possibly caused by weakening of the <span class="hlt">zonal</span> <span class="hlt">wind</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JMS...168...38D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JMS...168...38D"><span>Two decades [1992-2012] of surface <span class="hlt">wind</span> analyses based on satellite scatterometer observations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Desbiolles, Fabien; Bentamy, Abderrahim; Blanke, Bruno; Roy, Claude; Mestas-Nuñez, Alberto M.; Grodsky, Semyon A.; Herbette, Steven; Cambon, Gildas; Maes, Christophe</p> <p>2017-04-01</p> <p>Surface <span class="hlt">winds</span> (equivalent neutral <span class="hlt">wind</span> velocities at 10 m) from scatterometer missions since 1992 have been used to build up a 20-year climate series. Optimal interpolation and kriging methods have been applied to continuously provide surface <span class="hlt">wind</span> <span class="hlt">speed</span> and direction estimates over the global ocean on a regular grid in space and time. The use of other data sources such as radiometer data (SSM/I) and atmospheric <span class="hlt">wind</span> reanalyses (ERA-Interim) has allowed building a blended product available at 1/4° spatial resolution and every 6 h from 1992 to 2012. Sampling issues throughout the different missions (ERS-1, ERS-2, QuikSCAT, and ASCAT) and their possible impact on the homogeneity of the gridded product are discussed. In addition, we assess carefully the quality of the blended product in the absence of scatterometer data (1992 to 1999). Data selection experiments show that the description of the surface <span class="hlt">wind</span> is significantly improved by including the scatterometer <span class="hlt">winds</span>. The blended <span class="hlt">winds</span> compare well with buoy <span class="hlt">winds</span> (1992-2012) and they resolve finer spatial scales than atmospheric reanalyses, which make them suitable for studying air-sea interactions at mesoscale. The seasonal cycle and interannual variability of the product compare well with other long-term <span class="hlt">wind</span> analyses. The product is used to calculate 20-year trends in <span class="hlt">wind</span> <span class="hlt">speed</span>, as well as in <span class="hlt">zonal</span> and meridional <span class="hlt">wind</span> components. These trends show an important asymmetry between the southern and northern hemispheres, which may be an important issue for climate studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AGUFM.A51E0162M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AGUFM.A51E0162M"><span>Sea spray contributions to the air-sea fluxes at moderate and hurricane <span class="hlt">wind</span> <span class="hlt">speeds</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mueller, J. A.; Veron, F.</p> <p>2009-12-01</p> <p>At sufficiently high <span class="hlt">wind</span> <span class="hlt">speed</span> conditions, the surface of the ocean separates to form a substantial number of sea spray drops, which can account for a significant fraction of the total air-sea surface area and thus make important contributions to the aggregate air-sea momentum, heat and mass fluxes. Although consensus around the qualitative impacts of these drops has been building in recent years, the quantification of their impacts has remained elusive. Ultimately, the spray-mediated fluxes depend on three controlling factors: the number and size of drops formed at the surface, the duration of suspension within the atmospheric marine boundary layer, and the rate of momentum, heat and mass transfer between the drops and the atmosphere. While the latter factor can be estimated from an established, physically-based theory, the estimates for the former two are not well established. Using a recent, physically-based model of the sea spray source function along with the results from Lagrangian stochastic simulations of individual drops, we estimate the aggregate spray-mediated fluxes, finding reasonable agreement with existing models and estimates within the empirical range of <span class="hlt">wind</span> <span class="hlt">speed</span> conditions. At high <span class="hlt">wind</span> <span class="hlt">speed</span> conditions that are outside the empirical range, however, we find somewhat lower spray-mediated fluxes than previously reported in the literature, raising new questions about the relative air-sea fluxes at high <span class="hlt">wind</span> <span class="hlt">speeds</span> as well as the development and sustainment of hurricanes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19830025552','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19830025552"><span>Solar <span class="hlt">wind</span> iron abundance variations at solar <span class="hlt">wind</span> <span class="hlt">speeds</span> up to 600 km s sup -1, 1972 to 1976</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mitchell, D. G.; Roelof, E. C.; Bame, S. J.</p> <p>1982-01-01</p> <p>The Fe/H ratios in the peaks of high <span class="hlt">speed</span> streams (HSS) were analyzed during the decline of Solar Cycle 20 and the following minimum (October 1972 to December 1976). The response of the 50 to 200 keV ion channel of the APL/JHU energetic particle experiment (EPE) on IMP-7 and 8 was utilized to solar <span class="hlt">wind</span> iron ions at high solar <span class="hlt">wind</span> <span class="hlt">speeds</span> (V or = 600 km/sec). Fe measurements with solar <span class="hlt">wind</span> H and He parameters were compared from the Los Alamos National Laboratory (LANL) instruments on the same spacecraft. In general, the Fe distribution parameters (bulk velocity, flow direction, temperature) are found to be similar to the LANL He parameters. Although the average Fe/H ration in many steady HSS peaks agrees within observational uncertainties with the nominal coronal ratio of 4.7 x 0.00001, abundance variations of a factor of up to 6 are obtained across a given coronal-hole associated HSS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28925942','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28925942"><span>Application of Surface Protective Coating to Enhance Environment-Withstanding Property of the MEMS 2D <span class="hlt">Wind</span> Direction and <span class="hlt">Wind</span> <span class="hlt">Speed</span> Sensor.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shin, Kyu-Sik; Lee, Dae-Sung; Song, Sang-Woo; Jung, Jae Pil</p> <p>2017-09-19</p> <p>In this study, a microelectromechanical system (MEMS) two-dimensional (2D) <span class="hlt">wind</span> direction and <span class="hlt">wind</span> <span class="hlt">speed</span> sensor consisting of a square heating source and four thermopiles was manufactured using the heat detection method. The heating source and thermopiles of the manufactured sensor must be exposed to air to detect <span class="hlt">wind</span> <span class="hlt">speed</span> and <span class="hlt">wind</span> direction. Therefore, there are concerns that the sensor could be contaminated by deposition or adhesion of dust, sandy dust, snow, rain, and so forth, in the air, and that the membrane may be damaged by physical shock. Hence, there was a need to protect the heating source, thermopiles, and the membrane from environmental and physical shock. The upper protective coating to protect both the heating source and thermopiles and the lower protective coating to protect the membrane were formed by using high-molecular substances such as SU-8, Teflon and polyimide (PI). The sensor characteristics with the applied protective coatings were evaluated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26804750','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26804750"><span>Variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine control by discrete-time sliding mode approach.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Torchani, Borhen; Sellami, Anis; Garcia, Germain</p> <p>2016-05-01</p> <p>The aim of this paper is to propose a new design variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine control by discrete-time sliding mode approach. This methodology is designed for linear saturated system. The saturation constraint is reported on inputs vector. To this end, the back stepping design procedure is followed to construct a suitable sliding manifold that guarantees the attainment of a stabilization control objective. It is well known that the mechanisms are investigated in term of the most proposed assumptions to deal with the damping, shaft stiffness and inertia effect of the gear. The objectives are to synthesize robust controllers that maximize the energy extracted from <span class="hlt">wind</span>, while reducing mechanical loads and rotor <span class="hlt">speed</span> tracking combined with an electromagnetic torque. Simulation results of the proposed scheme are presented. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4311S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4311S"><span>Climate projection of synoptic patterns forming extremely high <span class="hlt">wind</span> <span class="hlt">speed</span> over the Barents Sea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Surkova, Galina; Krylov, Aleksey</p> <p>2017-04-01</p> <p>Frequency of extreme weather events is not very high, but their consequences for the human well-being may be hazardous. These seldom events are not always well simulated by climate models directly. Sometimes it is more effective to analyze numerical projection of large-scale synoptic event generating extreme weather. For example, in mid-latitude surface <span class="hlt">wind</span> <span class="hlt">speed</span> depends mainly on the sea level pressure (SLP) field - its configuration and horizontal pressure gradient. This idea was implemented for analysis of extreme <span class="hlt">wind</span> <span class="hlt">speed</span> events over the Barents Sea. The calendar of high surface <span class="hlt">wind</span> <span class="hlt">speed</span> V (10 m above the surface) was prepared for events with V exceeding 99th percentile value in the central part of the Barents Sea. Analysis of probability distribution function of V was carried out on the base of ERA-Interim reanalysis data (6-hours, 0.75x0.75 degrees of latitude and longitude) for the period 1981-2010. Storm <span class="hlt">wind</span> events number was found to be 240 days. Sea level pressure field over the sea and surrounding area was selected for each storm <span class="hlt">wind</span> event. For the climate of the future (scenario RCP8.5), projections of SLP from CMIP5 numerical experiments were used. More than 20 climate models results of projected SLP (2006-2100) over the Barents Sea were correlated with modern storm <span class="hlt">wind</span> SLP fields. Our calculations showed the positive tendency of annual frequency of storm SLP patterns over the Barents Sea by the end of 21st century.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ApJ...748..143K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ApJ...748..143K"><span>On the Variation of <span class="hlt">Zonal</span> Gravity Coefficients of a Giant Planet Caused by Its Deep <span class="hlt">Zonal</span> Flows</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kong, Dali; Zhang, Keke; Schubert, Gerald</p> <p>2012-04-01</p> <p>Rapidly rotating giant planets are usually marked by the existence of strong <span class="hlt">zonal</span> flows at the cloud level. If the <span class="hlt">zonal</span> flow is sufficiently deep and strong, it can produce hydrostatic-related gravitational anomalies through distortion of the planet's shape. This paper determines the <span class="hlt">zonal</span> gravity coefficients, J 2n , n = 1, 2, 3, ..., via an analytical method taking into account rotation-induced shape changes by assuming that a planet has an effective uniform density and that the <span class="hlt">zonal</span> flows arise from deep convection and extend along cylinders parallel to the rotation axis. Two different but related hydrostatic models are considered. When a giant planet is in rigid-body rotation, the exact solution of the problem using oblate spheroidal coordinates is derived, allowing us to compute the value of its <span class="hlt">zonal</span> gravity coefficients \\bar{J}_{2n}, n=1,2,3, \\dots, without making any approximation. When the deep <span class="hlt">zonal</span> flow is sufficiently strong, we develop a general perturbation theory for estimating the variation of the <span class="hlt">zonal</span> gravity coefficients, \\Delta {J}_{2n}={J}_{2n}-\\bar{J}_{2n}, n=1,2,3, \\dots, caused by the effect of the deep <span class="hlt">zonal</span> flows for an arbitrarily rapidly rotating planet. Applying the general theory to Jupiter, we find that the deep <span class="hlt">zonal</span> flow could contribute up to 0.3% of the J 2 coefficient and 0.7% of J 4. It is also found that the shape-driven harmonics at the 10th <span class="hlt">zonal</span> gravity coefficient become dominant, i.e., \\Delta {J}_{2n} \\,{\\ge}\\, \\bar{J}_{2n} for n >= 5.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.753k2007A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.753k2007A"><span><span class="hlt">Speed</span> and Torque Control Strategies for Loss Reduction of Vertical Axis <span class="hlt">Wind</span> Turbines</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Argent, Michael; McDonald, Alasdair; Leithead, Bill; Giles, Alexander</p> <p>2016-09-01</p> <p>This paper builds on the work into modelling the generator losses for Vertical Axis <span class="hlt">Wind</span> Turbines from their intrinsic torque cycling to investigate the effects of aerodynamic inefficiencies caused by the varying rotational <span class="hlt">speed</span> resulting from different torque control strategies to the cyclic torque. This is achieved by modelling the wake that builds up from the rotation of the VAWT rotor to investigate how the wake responds to a changing rotor <span class="hlt">speed</span> and how this in turn affects the torque produced by the blades as well as the corresponding change in generator losses and any changes to the energy extracted by the <span class="hlt">wind</span> turbine rotor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..1616978D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..1616978D"><span>Influence of time scale <span class="hlt">wind</span> <span class="hlt">speed</span> data on sustainability analysis for irrigating greenhouse crops</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Díaz Méndez, Rodrigo; García Llaneza, Joaquín; Peillón, Manuel; Perdigones, Alicia; Sanchez, Raul; Tarquis, Ana M.; Garcia, Jose Luis</p> <p>2014-05-01</p> <p>Appropriate water supply at crop/farm level, with suitable costs, is becoming more and more important. Energy management is closely related to water supply in this context, being <span class="hlt">wind</span> energy one of the options to be considered, using <span class="hlt">wind</span> pumps for irrigation water supply. Therefore, it is important to characterize the <span class="hlt">wind</span> <span class="hlt">speed</span> frequency distribution to study the technical feasibility to use its energy for irrigation management purpose. The general objective of this present research is to analyze the impact of time scale recorded <span class="hlt">wind</span> <span class="hlt">speed</span> data in the sustainability for tomato (Solanum lycopersicum L.) grown under greenhouse at Cuban conditions using drip irrigation system. For this porpoise, a daily estimation balance between water needs and water availability was used to evaluate the feasibility of the most economic windmill irrigation system. Several factors were included: <span class="hlt">wind</span> velocity (W, m/s) in function of the time scale averaged, flow supplied by the <span class="hlt">wind</span> pump as a function of the elevation height (H, m) and daily greenhouse evapotranspiration. Monthly volumes of water required for irrigation (Dr, m3/ha) and in the water tank (Vd, m3), as well as the monthly irrigable area (Ar, ha), were estimated by cumulative deficit water budgeting taking in account these factors. Three-hourly <span class="hlt">wind</span> velocity (W3h, m/s) data from 1992 till 2008 was available for this study. The original data was grouped in six and twelve hourly data (W6h and W12h respectively) as well as daily data (W24h). For each time scale the daily estimation balance was applied. A comparison of the results points out a need for at least three-hourly data to be used mainly in the months in which mean <span class="hlt">wind</span> <span class="hlt">speed</span> are close or below the pumps threshold <span class="hlt">speed</span> to start-up functioning. References Manuel Esteban Peillon Mesa, Ana Maria Tarquis Alfonso, José Luis García Fernández, and Raúl Sánchez Calvo. The use of <span class="hlt">wind</span> pumps for irrigating greenhouse tomato crops: a case study in Cuba. Geophysical</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25615732','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25615732"><span>Pose measurement method and experiments for high-<span class="hlt">speed</span> rolling targets in a <span class="hlt">wind</span> tunnel.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun</p> <p>2014-12-12</p> <p>High-precision <span class="hlt">wind</span> tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-<span class="hlt">speed</span> pose vision measurement method is proposed for high-<span class="hlt">speed</span> and rolling targets in a supersonic <span class="hlt">wind</span> tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-<span class="hlt">speed</span> image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-<span class="hlt">speed</span> targets in the laboratory and in a supersonic <span class="hlt">wind</span> tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4299094','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4299094"><span>Pose Measurement Method and Experiments for High-<span class="hlt">Speed</span> Rolling Targets in a <span class="hlt">Wind</span> Tunnel</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun</p> <p>2014-01-01</p> <p>High-precision <span class="hlt">wind</span> tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-<span class="hlt">speed</span> pose vision measurement method is proposed for high-<span class="hlt">speed</span> and rolling targets in a supersonic <span class="hlt">wind</span> tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-<span class="hlt">speed</span> image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-<span class="hlt">speed</span> targets in the laboratory and in a supersonic <span class="hlt">wind</span> tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°. PMID:25615732</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.1245B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.1245B"><span>The Huygens Doppler <span class="hlt">Wind</span> Experiment: Ten Years Ago</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bird, Michael; Dutta-Roy, Robin; Dzierma, Yvonne; Atkinson, David; Allison, Michael; Asmar, Sami; Folkner, William; Preston, Robert; Plettemeier, Dirk; Tyler, Len; Edenhofer, Peter</p> <p>2015-04-01</p> <p>The Huygens Doppler <span class="hlt">Wind</span> Experiment (DWE) achieved its primary scientific goal: the derivation of Titan's vertical <span class="hlt">wind</span> profile from the start of Probe descent to the surface. The carrier frequency of the ultra-stable Huygens radio signal at 2040 MHz was recorded using special narrow-band receivers at two large radio telescopes on Earth: the Green Bank Telescope in West Virginia and the Parkes Radio Telescope in Australia. Huygens drifted predominantly eastward during the parachute descent, providing the first in situ confirmation of Titan's prograde super-rotational <span class="hlt">zonal</span> <span class="hlt">winds</span>. A region of surprisingly weak <span class="hlt">wind</span> with associated strong vertical shear reversal was discovered within the range of altitudes from 65 to 100 km. Below this level, the <span class="hlt">zonal</span> <span class="hlt">wind</span> subsided monotonically from 35 m/s to about 7 km, at which point it reversed direction. The vertical profile of the near-surface <span class="hlt">winds</span> implies the existence of a planetary boundary layer. Recent results on Titan atmospheric circulation within the context of the DWE will be reviewed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..15.2354M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..15.2354M"><span>Coherency Between Volume Transport in the Antarctic Circumpolar Current and Southern Hemisphere <span class="hlt">Winds</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Makowski, Jessica; Chambers, Don; Bonin, Jennifer</p> <p>2013-04-01</p> <p>Previous studies have suggested that ocean bottom pressure (OBP) can be used to measure the transport variability of the Antarctic Circumpolar Current (ACC). The OBP observations from the Gravity Recovery and Climate Experiment (GRACE) will be used to calculate transport along the 150°E longitude choke point, between Antarctica and Australia. We will examine whether <span class="hlt">zonally</span> averaged <span class="hlt">wind</span> stress, <span class="hlt">wind</span> stress curl, or local <span class="hlt">zonal</span> <span class="hlt">winds</span> are more coherent with <span class="hlt">zonal</span> mass transport variability. Preliminary studies suggest that seasonal variation in transport across 150°E is more correlated with <span class="hlt">winds</span> along and north of the northern front of the ACC: the Sub Tropical front (STF). It also appears that interannual variations in transport along 150°E are related to <span class="hlt">wind</span> variations south of the STF and centered south of the Sub Antarctic Front (SAF). We have observed a strong anti-correlation across the SAF, in the Indian Ocean, which suggests <span class="hlt">wind</span> stress curl may also be responsible for transport variations. Preliminary results will be presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060041678&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060041678&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS"><span>Distant Tail Behavior During High <span class="hlt">Speed</span> Solar <span class="hlt">Wind</span> Streams and Magnetic Storms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ho, C. M.; Tsurutani, B. T.</p> <p>1997-01-01</p> <p>We have examined the ISEE 3 distant tail data during three intense magnetic storms and have identified the tail response to high-<span class="hlt">speed</span> solar <span class="hlt">wind</span> streams, interplanetary magnetic clouds, and near-Earth storms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900000729','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900000729"><span>Large-scale Advanced Prop-fan (LAP) high <span class="hlt">speed</span> <span class="hlt">wind</span> tunnel test report</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Campbell, William A.; Wainauski, Harold S.; Arseneaux, Peter J.</p> <p>1988-01-01</p> <p>High <span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel testing of the SR-7L Large Scale Advanced Prop-Fan (LAP) is reported. The LAP is a 2.74 meter (9.0 ft) diameter, 8-bladed tractor type rated for 4475 KW (6000 SHP) at 1698 rpm. It was designated and built by Hamilton Standard under contract to the NASA Lewis Research Center. The LAP employs thin swept blades to provide efficient propulsion at flight <span class="hlt">speeds</span> up to Mach .85. Testing was conducted in the ONERA S1-MA Atmospheric <span class="hlt">Wind</span> Tunnel in Modane, France. The test objectives were to confirm that the LAP is free from high <span class="hlt">speed</span> classical flutter, determine the structural and aerodynamic response to angular inflow, measure blade surface pressures (static and dynamic) and evaluate the aerodynamic performance at various blade angles, rotational <span class="hlt">speeds</span> and Mach numbers. The measured structural and aerodynamic performance of the LAP correlated well with analytical predictions thereby providing confidence in the computer prediction codes used for the design. There were no signs of classical flutter throughout all phases of the test up to and including the 0.84 maximum Mach number achieved. Steady and unsteady blade surface pressures were successfully measured for a wide range of Mach numbers, inflow angles, rotational <span class="hlt">speeds</span> and blade angles. No barriers were discovered that would prevent proceeding with the PTA (Prop-Fan Test Assessment) Flight Test Program scheduled for early 1987.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850012157','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850012157"><span>Large Scale Winter Time Disturbances in Meteor <span class="hlt">Winds</span> over Central and Eastern Europe</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Greisiger, K. M.; Portnyagin, Y. I.; Lysenko, I. A.</p> <p>1984-01-01</p> <p>Daily <span class="hlt">zonal</span> <span class="hlt">wind</span> data of the four pre-MAP-winters 1978/79 to 1981/82 obtained over Central Europe and Eastern Europe by the radar meteor method were studied. Available temperature and satellite radiance data of the middle and upper stratosphere were used for comparison, as well as <span class="hlt">wind</span> data from Canada. The existence or nonexistence of coupling between the observed large scale <span class="hlt">zonal</span> <span class="hlt">wind</span> disturbances in the upper mesopause region (90 to 100 km) and corresponding events in the stratosphere are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1361550','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1361550"><span>Synthetic <span class="hlt">wind</span> <span class="hlt">speed</span> scenarios generation for probabilistic analysis of hybrid energy systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chen, Jun; Rabiti, Cristian</p> <p></p> <p>Hybrid energy systems consisting of multiple energy inputs and multiple energy outputs have been proposed to be an effective element to enable ever increasing penetration of clean energy. In order to better understand the dynamic and probabilistic behavior of hybrid energy systems, this paper proposes a model combining Fourier series and autoregressive moving average (ARMA) to characterize historical weather measurements and to generate synthetic weather (e.g., <span class="hlt">wind</span> <span class="hlt">speed</span>) data. In particular, Fourier series is used to characterize the seasonal trend in historical data, while ARMA is applied to capture the autocorrelation in residue time series (e.g., measurements minus seasonal trends).more » The generated synthetic <span class="hlt">wind</span> <span class="hlt">speed</span> data is then utilized to perform probabilistic analysis of a particular hybrid energy system con guration, which consists of nuclear power plant, <span class="hlt">wind</span> farm, battery storage, natural gas boiler, and chemical plant. As a result, requirements on component ramping rate, economic and environmental impacts of hybrid energy systems, and the effects of deploying different sizes of batteries in smoothing renewable variability, are all investigated.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1361550-synthetic-wind-speed-scenarios-generation-probabilistic-analysis-hybrid-energy-systems','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1361550-synthetic-wind-speed-scenarios-generation-probabilistic-analysis-hybrid-energy-systems"><span>Synthetic <span class="hlt">wind</span> <span class="hlt">speed</span> scenarios generation for probabilistic analysis of hybrid energy systems</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Chen, Jun; Rabiti, Cristian</p> <p>2016-11-25</p> <p>Hybrid energy systems consisting of multiple energy inputs and multiple energy outputs have been proposed to be an effective element to enable ever increasing penetration of clean energy. In order to better understand the dynamic and probabilistic behavior of hybrid energy systems, this paper proposes a model combining Fourier series and autoregressive moving average (ARMA) to characterize historical weather measurements and to generate synthetic weather (e.g., <span class="hlt">wind</span> <span class="hlt">speed</span>) data. In particular, Fourier series is used to characterize the seasonal trend in historical data, while ARMA is applied to capture the autocorrelation in residue time series (e.g., measurements minus seasonal trends).more » The generated synthetic <span class="hlt">wind</span> <span class="hlt">speed</span> data is then utilized to perform probabilistic analysis of a particular hybrid energy system con guration, which consists of nuclear power plant, <span class="hlt">wind</span> farm, battery storage, natural gas boiler, and chemical plant. As a result, requirements on component ramping rate, economic and environmental impacts of hybrid energy systems, and the effects of deploying different sizes of batteries in smoothing renewable variability, are all investigated.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110023417','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110023417"><span>On the Relationship Between High <span class="hlt">Speed</span> Solar <span class="hlt">Wind</span> Streams and Radiation Belt Electron Fluxes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zheng, Yihua</p> <p>2011-01-01</p> <p>Both past and recent research results indicate that solar <span class="hlt">wind</span> <span class="hlt">speed</span> has a close connection to radiation belt electron fluxes [e.g., Paulikas and Blake, 1979; Reeves et aI., 2011]: a higher solar <span class="hlt">wind</span> <span class="hlt">speed</span> is often associated with a higher level of radiation electron fluxes. But the relationship can be very complex [Reeves et aI., 2011]. The study presented here provides further corroboration of this viewpoint by emphasizing the importance of a global perspective and time history. We find that all the events during years 2010 and 2011 where the >0.8 MeV integral electron flux exceeds 10(exp 5) particles/sq cm/sr/s (pfu) at GEO orbit are associated with the high <span class="hlt">speed</span> streams (HSS) following the onset of the Stream Interaction Region (SIR), with most of them belonging to the long-lasting Corotating Interaction Region (CIR). Our preliminary results indicate that during HSS events, a maximum <span class="hlt">speed</span> of 700 km/s and above is a sufficient but not necessary condition for the > 0.8 MeV electron flux to reach 10(exp 5) pfu. But in the exception cases of HSS events where the electron flux level exceeds the 10(exp 5) pfu value but the maximum solar <span class="hlt">wind</span> <span class="hlt">speed</span> is less than 700 km/s, a prior impact can be noted either from a CME or a transient SIR within 3-4 days before the arrival of the HSS - stressing the importance of time history. Through superposed epoch analysis and studies providing comparisons with the CME events and the HSS events where the flux level fails to reach the 10(exp 5) pfu, we will present the quantitative assessment of behaviors and relationships of various quantities, such as the time it takes to reach the flux threshold value from the stream interface and its dependence on different physical parameters (e.g., duration of the HSS event, its maximum or average of the solar <span class="hlt">wind</span> <span class="hlt">speed</span>, IMF Bz, Kp). The ultimate goal is to apply what is derived to space weather forecasting.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25024411','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25024411"><span>High-fidelity simulations of unsteady civil aircraft aerodynamics: stakes and perspectives. Application of <span class="hlt">zonal</span> detached eddy simulation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Deck, Sébastien; Gand, Fabien; Brunet, Vincent; Ben Khelil, Saloua</p> <p>2014-08-13</p> <p>This paper provides an up-to-date survey of the use of <span class="hlt">zonal</span> detached eddy simulations (ZDES) for unsteady civil aircraft applications as a reflection on the stakes and perspectives of the use of hybrid methods in the framework of industrial aerodynamics. The issue of <span class="hlt">zonal</span> or non-<span class="hlt">zonal</span> treatment of turbulent flows for engineering applications is discussed. The ZDES method used in this article and based on a fluid problem-dependent <span class="hlt">zonalization</span> is briefly presented. Some recent landmark achievements for conditions all over the flight envelope are presented, including low-<span class="hlt">speed</span> (aeroacoustics of high-lift devices and landing gear), cruising (engine-airframe interactions), propulsive jets and off-design (transonic buffet and dive manoeuvres) applications. The implications of such results and remaining challenges in a more global framework are further discussed. © 2014 The Author(s) Published by the Royal Society. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20050019654','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20050019654"><span>Comparison of Drop and <span class="hlt">Wind</span>-Tunnel Experiments on Bomb Drag at High Subsonic <span class="hlt">Speeds</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gothert, B.</p> <p>1948-01-01</p> <p>The drag coefficients of bombs at high velocities velocity of fall was 97 percent of the <span class="hlt">speed</span> of sound) (the highest are determined by drop tests and compared with measurements taken in the DVL high-<span class="hlt">speed</span> closed <span class="hlt">wind</span> tunnel and the open jet at AVA - Gottingen.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20539506','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20539506"><span>Derivation of atmospheric extinction profiles and <span class="hlt">wind</span> <span class="hlt">speed</span> over the ocean from a satellite-borne lidar.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Weinman, J A</p> <p>1988-10-01</p> <p>A simulated analysis is presented that shows that returns from a single-frequency space-borne lidar can be combined with data from conventional visible satellite imagery to yield profiles of aerosol extinction coefficients and the <span class="hlt">wind</span> <span class="hlt">speed</span> at the ocean surface. The optical thickness of the aerosols in the atmosphere can be derived from visible imagery. That measurement of the total optical thickness can constrain the solution to the lidar equation to yield a robust estimate of the extinction profile. The specular reflection of the lidar beam from the ocean can be used to determine the <span class="hlt">wind</span> <span class="hlt">speed</span> at the sea surface once the transmission of the atmosphere is known. The impact on the retrieved aerosol profiles and surface <span class="hlt">wind</span> <span class="hlt">speed</span> produced by errors in the input parameters and noise in the lidar measurements is also considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920033132&hterms=deming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddeming','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920033132&hterms=deming&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Ddeming"><span>Absolute <span class="hlt">wind</span> velocities in the lower thermosphere of Venus using infrared heterodyne spectroscopy</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Goldstein, Jeffrey J.; Mumma, Michael J.; Kostiuk, Theodor; Deming, Drake; Espenak, Fred; Zipoy, David</p> <p>1991-01-01</p> <p>NASA's IR Telescope Facility and the McMath Solar Telescope have yielded absolute <span class="hlt">wind</span> velocities in the Venus thermosphere for December 1985 to March 1987 with sufficient spatial resolution for circulation model discrimination. A qualitative analysis of beam-integrated <span class="hlt">winds</span> indicates subsolar-to-antisolar circulation in the lower thermosphere; horizontal <span class="hlt">wind</span> velocity was derived from a two-parameter model <span class="hlt">wind</span> field of subsolar-antisolar and <span class="hlt">zonal</span> components. A unique model fit common to all observing periods possessed 120 m/sec subsolar-antisolar and 25 m/sec <span class="hlt">zonal</span> retrograde components, consistent with the Bougher et al. (1986, 1988) hydrodynamical models for 110 km.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JQSRT.188...52Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JQSRT.188...52Y"><span>Development of a mobile Doppler lidar system for <span class="hlt">wind</span> and temperature measurements at 30-70 km</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yan, Zhaoai; Hu, Xiong; Guo, Wenjie; Guo, Shangyong; Cheng, Yongqiang; Gong, Jiancun; Yue, Jia</p> <p>2017-02-01</p> <p>A mobile Doppler lidar system has been developed to simultaneously measure <span class="hlt">zonal</span> and meridional <span class="hlt">winds</span> and temperature from 30 to 70 km. Each of the two <span class="hlt">zonal</span> and meridional <span class="hlt">wind</span> subsystems employs a 15 W power, 532 nm laser and a 1 m diameter telescope. Iodine vapor filters are used to stabilize laser frequency and to detect the Doppler shift of backscattered signal. The integration method is used for temperature measurement. Experiments were carried out using the mobile Doppler lidar in August 2014 at Qinghai, China (91°E, 38°N). The <span class="hlt">zonal</span> <span class="hlt">wind</span> was measured from 20 to 70 km at a 3 km spatial resolution and 2 h temporal resolution. The measurement error is about 0.5 m/s at 30 km, and 10 m/s at 70 km. In addition, the temperature was measured from 30 to 70 km at 1 km spatial resolution and 1 h temporal resolution. The temperature measurement error is about 0.4 K at 30 km, and 8.0 K at 70 km. Comparison of the lidar results with the temperature of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), the <span class="hlt">zonal</span> <span class="hlt">wind</span> of the Modern-Era Retrospective Analysis for Re-search and Applications (MERRA), and radiosonde <span class="hlt">zonal</span> <span class="hlt">wind</span> shows good agreement, indicating that the Doppler lidar results are reliable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950032354&hterms=solar+intensity+measurement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsolar%2Bintensity%2Bmeasurement','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950032354&hterms=solar+intensity+measurement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsolar%2Bintensity%2Bmeasurement"><span>Latitudinal variation of <span class="hlt">speed</span> and mass flux in the acceleration region of the solar <span class="hlt">wind</span> inferred from spectral broadening measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Woo, Richard; Goldstein, Richard M.</p> <p>1994-01-01</p> <p>Spectral broadening measurements conducted at S-band (13-cm wavelength) during solar minimum conditions in the heliocentric distance range of 3-8 R(sub O) by Mariner 4, Pioneer 10, Mariner 10, Helios 1, Helios 2, and Viking have been combined to reveal a factor of 2.6 reduction in bandwidth from equator to pole. Since spectral broadening bandwidth depends on electron density fluctuation and solar <span class="hlt">wind</span> <span class="hlt">speed</span>, and latitudinal variation of the former is available from coherence bandwidth measurements, the remote sensing spectral broadening measurements provide the first determination of the latitudinal variation of solar <span class="hlt">wind</span> <span class="hlt">speed</span> in the acceleration region. When combined with electron density measurements deduced from white-light coronagraphs, this result also leads to the first determination of the latitudinal variation of mass flux in the acceleration region. From equator to pole, solar <span class="hlt">wind</span> <span class="hlt">speed</span> increases by a factor of 2.2, while mass flux decreases by a factor of 2.3. These results are consistent with measurements of solar <span class="hlt">wind</span> <span class="hlt">speed</span> by multi-station intensity scintillation measurements, as well as measurements of mass flux inferred from Lyman alpha observations, both of which pertain to the solar <span class="hlt">wind</span> beyond 0.5 AU. The spectral broadening observations, therefore, strengthen earlier conclusions about the latitudinal variation of solar <span class="hlt">wind</span> <span class="hlt">speed</span> and mass flux, and reinforce current solar coronal models and their implications for solar <span class="hlt">wind</span> acceleration and solar <span class="hlt">wind</span> modeling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750003859','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750003859"><span>A <span class="hlt">wind</span>-tunnel investigation of parameters affecting helicopter directional control at low <span class="hlt">speeds</span> in ground effect</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yeager, W. T., Jr.; Young, W. H., Jr.; Mantay, W. R.</p> <p>1974-01-01</p> <p>An investigation was conducted in the Langley full-scale tunnel to measure the performance of several helicopter tail-rotor/fin configurations with regard to directional control problems encountered at low <span class="hlt">speeds</span> in ground effect. Tests were conducted at <span class="hlt">wind</span> azimuths of 0 deg to 360 deg in increments of 30 deg and 60 deg and at <span class="hlt">wind</span> <span class="hlt">speeds</span> from 0 to 35 knots. The results indicate that at certain combinations of <span class="hlt">wind</span> <span class="hlt">speed</span> and <span class="hlt">wind</span> azimuth, large increases in adverse fin force require correspondingly large increases in the tail-rotor thrust, collective pitch, and power required to maintain yaw trim. Changing the tail-rotor direction of rotation to top blade aft for either a pusher tail rotor (tail-rotor wake blowing away from fin) or a tractor tail rotor (tail-rotor wake blowing against fin) will alleviate this problem. For a pusher tail rotor at 180 deg <span class="hlt">wind</span> azimuth, increases in the fin/tail-rotor gap were not found to have any significant influence on the overall vehicle directional control capability. Changing the tail rotor to a higher position was found to improve tail-rotor performance for a fin-off configuration at a <span class="hlt">wind</span> azimuth of 180 deg. A V-tail configuration with a pusher tail rotor with top blade aft direction of rotation was found to be the best configuration with regard to overall directional control capability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19980201248','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19980201248"><span>Application of Rapid Prototyping Methods to High-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel Testing</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Springer, A. M.</p> <p>1998-01-01</p> <p>This study was undertaken in MSFC's 14-Inch Trisonic <span class="hlt">Wind</span> Tunnel to determine if rapid prototyping methods could be used in the design and manufacturing of high <span class="hlt">speed</span> <span class="hlt">wind</span> tunnel models in direct testing applications, and if these methods would reduce model design/fabrication time and cost while providing models of high enough fidelity to provide adequate aerodynamic data, and of sufficient strength to survive the test environment. Rapid prototyping methods utilized to construct <span class="hlt">wind</span> tunnel models in a wing-body-tail configuration were: fused deposition method using both ABS plastic and PEEK as building materials, stereolithography using the photopolymer SL-5170, selective laser sintering using glass reinforced nylon, and laminated object manufacturing using plastic reinforced with glass and 'paper'. This study revealed good agreement between the SLA model, the metal model with an FDM-ABS nose, an SLA nose, and the metal model for most operating conditions, while the FDM-ABS data diverged at higher loading conditions. Data from the initial SLS model showed poor agreement due to problems in post-processing, resulting in a different configuration. A second SLS model was tested and showed relatively good agreement. It can be concluded that rapid prototyping models show promise in preliminary aerodynamic development studies at subsonic, transonic, and supersonic <span class="hlt">speeds</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018IzAOP..54..127N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018IzAOP..54..127N"><span>On the Development of Models for Height Profiles of the <span class="hlt">Wind</span> <span class="hlt">Speed</span> in the Atmospheric Surface Layer</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nikolaev, V. G.; Ganaga, S. V.; Kudryashov, Yu. I.; Nikolaev, V. V.</p> <p>2018-03-01</p> <p>The reliability of the known models of a height profile of the <span class="hlt">wind</span> <span class="hlt">speed</span> V( h) in the atmospheric boundary layer (ABL) and near-surface layer (NSL) is analyzed using the data of long-term ABL measurements accumulated in Russia in the state network of meteorological and aerological stations and the data of multilevel measurements at mast <span class="hlt">wind</span>-measuring complexes. A new multilayer semiempirical model of V( h) is proposed which is based on aerodynamic and physical representations of the ABL vertical structure and relies on the hypothesis that <span class="hlt">wind-speed</span> profiles providing the minimum <span class="hlt">wind</span> friction on the ground and satisfying the conditions of profile smoothness are feasible in the ABL. This model ensures the best agreement with the data of meteorological, aerological, and mast <span class="hlt">wind</span> measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/37282','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/37282"><span>Mean <span class="hlt">wind</span> <span class="hlt">speed</span> below building height in residential neighborhoods with different tree densities</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>G.M. Heisler</p> <p>1990-01-01</p> <p>There is little available knowledge of the absolute or relative effects of trees and buildings on <span class="hlt">wind</span> at or below building height in residential neighborhoods. In this study, mean <span class="hlt">wind</span> <span class="hlt">speed</span> was measured at a height of 6.6 ft (2 m) in neighborhoods of single-family houses. BuIlding densities ranged between 6% and 12% of the land ares, and tree-cover densities were...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1982SoEn...29..363C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1982SoEn...29..363C"><span>The spectrum of <span class="hlt">wind</span> <span class="hlt">speed</span> fluctuations encountered by a rotating blade of a <span class="hlt">wind</span> energy conversion system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Connell, J. R.</p> <p>1982-01-01</p> <p>The results of anemometer, hot-wire anemometer, and laser anemometer array and crosswind sampling of <span class="hlt">wind</span> <span class="hlt">speed</span> and turbulence in an area swept by intermediate-to-large <span class="hlt">wind</span> turbine blades are presented, with comparisons made with a theoretical model for the <span class="hlt">wind</span> fluctuations. A rotating frame of reference was simulated by timing the anemometric readings at different points of the actuator disk area to coincide with the moment a turbine blade would pass through the point. The hot-wire sensors were mounted on an actual rotating boom, while the laser scanned the <span class="hlt">wind</span> velocity field in a vertical crosswind circle. The midfrequency region of the turbulence spectrum was found to be depleted, with energy shifted to the high end of the spectrum, with an additional peak at the rotation frequency of the rotor. A model is developed, assuming homogeneous, isotropic turbulence, to reproduce the observed spectra and verify and extend scaling relations using turbine and atmospheric length and time scales. The model is regarded as useful for selecting <span class="hlt">wind</span> turbine hub heights and rotor rotation rates.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19750022660','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19750022660"><span>The nature of multiple solutions for surface <span class="hlt">wind</span> <span class="hlt">speed</span> over the oceans from scatterometer measurements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Price, J. C.</p> <p>1975-01-01</p> <p>The satellite SEASAT-A will carry a radar scatterometer in order to measure microwave backscatter from the sea surface. From pairs of radar measurements at angles separated by 90 deg in azimuth the surface <span class="hlt">wind</span> <span class="hlt">speed</span> and direction may be inferred, though not uniquely. The character of the solutions for <span class="hlt">wind</span> <span class="hlt">speed</span> and direction is displayed, as well as the nature of the ambiguities of these solutions. An economical procedure for handling such data is described, plus a criterion for the need for conventional (surface) data in order to resolve the ambiguities of solutions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950023922','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950023922"><span>An atlas of monthly mean distributions of SSMI surface <span class="hlt">wind</span> <span class="hlt">speed</span>, AVHRR/2 sea surface temperature, AMI surface <span class="hlt">wind</span> velocity, TOPEX/POSEIDON sea surface height, and ECMWF surface <span class="hlt">wind</span> velocity during 1993</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Halpern, D.; Fu, L.; Knauss, W.; Pihos, G.; Brown, O.; Freilich, M.; Wentz, F.</p> <p>1995-01-01</p> <p>The following monthly mean global distributions for 1993 are presented with a common color scale and geographical map: 10-m height <span class="hlt">wind</span> <span class="hlt">speed</span> estimated from the Special Sensor Microwave Imager (SSMI) on a United States (U.S.) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) satellite; 10-m height <span class="hlt">wind</span> <span class="hlt">speed</span> and direction estimated from the Active Microwave Instrument (AMI) on the European Space Agency (ESA) European Remote Sensing (ERS-1) satellite; sea surface height estimated from the joint U.S.-France Topography Experiment (TOPEX)/POSEIDON spacecraft; and 10-m height <span class="hlt">wind</span> <span class="hlt">speed</span> and direction produced by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of annual mean, monthly mean, and sampling distributions are displayed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvE..94f7001A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvE..94f7001A"><span>Comment on "Critical <span class="hlt">wind</span> <span class="hlt">speed</span> at which trees break"</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Albrecht, Axel; Badel, Eric; Bonnesoeur, Vivien; Brunet, Yves; Constant, Thiéry; Défossez, Pauline; de Langre, Emmanuel; Dupont, Sylvain; Fournier, Meriem; Gardiner, Barry; Mitchell, Stephen J.; Moore, John R.; Moulia, Bruno; Nicoll, Bruce C.; Niklas, Karl J.; Schelhaas, Mart-Jan; Spatz, Hans-Christof; Telewski, Frank W.</p> <p>2016-12-01</p> <p>Virot et al. [E. Virot et al., Phys. Rev. E 93, 023001 (2016), 10.1103/PhysRevE.93.023001] assert that the critical <span class="hlt">wind</span> <span class="hlt">speed</span> at which ⩾50% of all trees in a population break is ≈42 m/s, regardless of tree characteristics. We show that empirical data do not support this assertion, and that the assumptions underlying the theory used by Virot et al. are inconsistent with the biomechanics of trees.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AtmEn.160...70M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AtmEn.160...70M"><span>Influence of <span class="hlt">wind-speed</span> on short-duration NO2 measurements using Palmes and Ogawa passive diffusion samplers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Masey, Nicola; Gillespie, Jonathan; Heal, Mathew R.; Hamilton, Scott; Beverland, Iain J.</p> <p>2017-07-01</p> <p>We assessed the precision and accuracy of nitrogen dioxide (NO2) concentrations over 2-day, 3-day and 7-day exposure periods measured with the following types of passive diffusion samplers: standard (open) Palmes tubes; standard Ogawa samplers with commercially-prepared Ogawa absorbent pads (Ogawa[S]); and modified Ogawa samplers with absorbent-impregnated stainless steel meshes normally used in Palmes tubes (Ogawa[P]). We deployed these passive samplers close to the inlet of a chemiluminescence NO2 analyser at an urban background site in Glasgow, UK over 32 discrete measurement periods. Duplicate relative standard deviation was <7% for all passive samplers. The Ogawa[P], Ogawa[S] and Palmes samplers explained 93%, 87% and 58% of temporal variation in analyser concentrations respectively. Uptake rates for Palmes and Ogawa[S] samplers were positively and linearly associated with <span class="hlt">wind-speed</span> (P < 0.01 and P < 0.05 respectively). Computation of adjusted uptake rates using average <span class="hlt">wind-speed</span> observed during each sampling period increased the variation in analyser concentrations explained by Palmes and Ogawa[S] estimates to 90% and 92% respectively, suggesting that measurements can be corrected for shortening of diffusion path lengths due to <span class="hlt">wind-speed</span> to improve the accuracy of estimates of short-term NO2 exposure. Monitoring situations where it is difficult to reliably estimate <span class="hlt">wind-speed</span> variations, e.g. across multiple sites with different unknown exposures to local <span class="hlt">winds</span>, and personal exposure monitoring, are likely to benefit from protection of these sampling devices from the effects of <span class="hlt">wind</span>, for example by use of a mesh or membrane across the open end. The uptake rate of Ogawa[P] samplers was not associated with <span class="hlt">wind-speed</span> resulting in a high correlation between estimated concentrations and observed analyser concentrations. The use of Palmes meshes in Ogawa[P] samplers reduced the cost of sampler preparation and removed uncertainty associated with the unknown</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01187&hterms=background+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbackground%2Bwind','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01187&hterms=background+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbackground%2Bwind"><span><span class="hlt">Wind</span> Patterns in Jupiter's Equatorial Region (Time set 1)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p><span class="hlt">Wind</span> patterns of Jupiter's equatorial region. This mosaic covers an area of 34,000 kilometers by 22,000 kilometers and was taken using the 756 nanometer (nm) near-infrared continuum filter. The dark region near the center of the mosaic is an equatorial 'hotspot' similar to the Galileo Probe entry site. The near-infrared continuum filter shows the features of Jupiter's main visible cloud deck.<p/>Jupiter's atmospheric circulation is dominated by alternating jets of east/west (<span class="hlt">zonal</span>) <span class="hlt">winds</span>. The bands have different widths and <span class="hlt">wind</span> <span class="hlt">speeds</span> but have remained constant as long as telescopes and spacecraft have measured them. The top half of these mosaics lies within Jupiter's North Equatorial Belt, a westward (left) current. The bottom half shows part of the Equatorial Zone, a fast moving eastward current. The clouds near the hotspot are the fastest moving features in these mosaics, moving at about 100 meters per second, or 224 miles per hour.<p/>Superimposed on the <span class="hlt">zonal</span> <span class="hlt">wind</span> currents is the Jovian 'weather'. The arrows show the <span class="hlt">winds</span> measured by an observer moving eastward (right) at the <span class="hlt">speed</span> of the hotspot. (The observer's perspective is that the hotspot is 'still' while the rest of the planet moves around it.) Clouds south of the hotspot appear to be moving towards it, as seen in the flow aligned with cloud streaks to the southwest and in the clockwise flow to the southeast. Interestingly, there is little cloud motion away from the hotspot in any direction. This is consistent with the idea that dry air is converging over this region and sinking, maintaining the cloud-free nature of the hotspot.<p/>North is at the top. The mosaic covers latitudes 1 to 19 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.<p/>The Jet Propulsion Laboratory, Pasadena, CA</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A31H2278W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A31H2278W"><span>Drivers and seasonal predictability of extreme <span class="hlt">wind</span> <span class="hlt">speeds</span> in the ECMWF System 4 and a statistical model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Walz, M. A.; Donat, M.; Leckebusch, G. C.</p> <p>2017-12-01</p> <p>As extreme <span class="hlt">wind</span> <span class="hlt">speeds</span> are responsible for large socio-economic losses in Europe, a skillful prediction would be of great benefit for disaster prevention as well as for the actuarial community. Here we evaluate patterns of large-scale atmospheric variability and the seasonal predictability of extreme <span class="hlt">wind</span> <span class="hlt">speeds</span> (e.g. >95th percentile) in the European domain in the dynamical seasonal forecast system ECMWF System 4, and compare to the predictability based on a statistical prediction model. The dominant patterns of atmospheric variability show distinct differences between reanalysis and ECMWF System 4, with most patterns in System 4 extended downstream in comparison to ERA-Interim. The dissimilar manifestations of the patterns within the two models lead to substantially different drivers associated with the occurrence of extreme <span class="hlt">winds</span> in the respective model. While the ECMWF System 4 is shown to provide some predictive power over Scandinavia and the eastern Atlantic, only very few grid cells in the European domain have significant correlations for extreme <span class="hlt">wind</span> <span class="hlt">speeds</span> in System 4 compared to ERA-Interim. In contrast, a statistical model predicts extreme <span class="hlt">wind</span> <span class="hlt">speeds</span> during boreal winter in better agreement with the observations. Our results suggest that System 4 does not seem to capture the potential predictability of extreme <span class="hlt">winds</span> that exists in the real world, and therefore fails to provide reliable seasonal predictions for lead months 2-4. This is likely related to the unrealistic representation of large-scale patterns of atmospheric variability. Hence our study points to potential improvements of dynamical prediction skill by improving the simulation of large-scale atmospheric dynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780041990&hterms=joint+inversion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Djoint%2Binversion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780041990&hterms=joint+inversion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Djoint%2Binversion"><span>An empirical model for ocean radar backscatter and its application in inversion routine to eliminate <span class="hlt">wind</span> <span class="hlt">speed</span> and direction effects</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dome, G. J.; Fung, A. K.; Moore, R. K.</p> <p>1977-01-01</p> <p>Several regression models were tested to explain the <span class="hlt">wind</span> direction dependence of the 1975 JONSWAP (Joint North Sea Wave Project) scatterometer data. The models consider the radar backscatter as a harmonic function of <span class="hlt">wind</span> direction. The constant term accounts for the major effect of <span class="hlt">wind</span> <span class="hlt">speed</span> and the sinusoidal terms for the effects of direction. The fundamental accounts for the difference in upwind and downwind returns, while the second harmonic explains the upwind-crosswind difference. It is shown that a second harmonic model appears to adequately explain the angular variation. A simple inversion technique, which uses two orthogonal scattering measurements, is also described which eliminates the effect of <span class="hlt">wind</span> <span class="hlt">speed</span> and direction. Vertical polarization was shown to be more effective in determining both <span class="hlt">wind</span> <span class="hlt">speed</span> and direction than horizontal polarization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160014909','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160014909"><span>9x15 Low <span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel Acoustic Improvements</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stark, David; Stephens, David</p> <p>2016-01-01</p> <p>The 9- by 15-Foot Low <span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel (9x15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic <span class="hlt">Wind</span> Tunnel (8x6 SWT). The 8x6 SWT was completed in 1949 and acoustically treated to mitigate community noise issues in 1950. This treatment included the addition of a large muffler downstream of the 8x6 SWT test section and diffuser. The 9x15 LSWT was designed for performance testing of VSTOL aircraft models, but with the addition of the current acoustic treatment in 1986 the tunnel has been used principally for acoustic and performance testing of aircraft propulsions systems. The present document describes an anticipated acoustic upgrade to be completed in 2017.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19840062881&hterms=sass&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsass','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19840062881&hterms=sass&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dsass"><span>The effects of the variations in sea surface temperature and atmospheric stability in the estimation of average <span class="hlt">wind</span> <span class="hlt">speed</span> by SEASAT-SASS</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, W. T.</p> <p>1984-01-01</p> <p>The average <span class="hlt">wind</span> <span class="hlt">speeds</span> from the scatterometer (SASS) on the ocean observing satellite SEASAT are found to be generally higher than the average <span class="hlt">wind</span> <span class="hlt">speeds</span> from ship reports. In this study, two factors, sea surface temperature and atmospheric stability, are identified which affect microwave scatter and, therefore, wave development. The problem of relating satellite observations to a fictitious quantity, such as the neutral <span class="hlt">wind</span>, that has to be derived from in situ observations with models is examined. The study also demonstrates the dependence of SASS <span class="hlt">winds</span> on sea surface temperature at low <span class="hlt">wind</span> <span class="hlt">speeds</span>, possibly due to temperature-dependent factors, such as water viscosity, which affect wave development.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3815045','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3815045"><span>World's first telepathology experiments employing <span class="hlt">WINDS</span> ultra-high-<span class="hlt">speed</span> internet satellite, nicknamed “KIZUNA”</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sawai, Takashi; Uzuki, Miwa; Miura, Yasuhiro; Kamataki, Akihisa; Matsumura, Tsubasa; Saito, Kenji; Kurose, Akira; Osamura, Yoshiyuki R.; Yoshimi, Naoki; Kanno, Hiroyuki; Moriya, Takuya; Ishida, Yoji; Satoh, Yohichi; Nakao, Masahiro; Ogawa, Emiko; Matsuo, Satoshi; Kasai, Hiroyuki; Kumagai, Kazuhiro; Motoda, Toshihiro; Hopson, Nathan</p> <p>2013-01-01</p> <p>Background: Recent advances in information technology have allowed the development of a telepathology system involving high-<span class="hlt">speed</span> transfer of high-volume histological figures via fiber optic landlines. However, at present there are geographical limits to landlines. The Japan Aerospace Exploration Agency (JAXA) has developed the “Kizuna” ultra-high <span class="hlt">speed</span> internet satellite and has pursued its various applications. In this study we experimented with telepathology in collaboration with JAXA using Kizuna. To measure the functionality of the Wideband InterNet working engineering test and Demonstration Satellite (<span class="hlt">WINDS</span>) ultra-high <span class="hlt">speed</span> internet satellite in remote pathological diagnosis and consultation, we examined the adequate data transfer <span class="hlt">speed</span> and stability to conduct telepathology (both diagnosis and conferencing) with functionality, and ease similar or equal to telepathology using fiber-optic landlines. Materials and Methods: We performed experiments for 2 years. In year 1, we tested the usability of the <span class="hlt">WINDS</span> for telepathology with real-time video and virtual slide systems. These are state-of-the-art technologies requiring massive volumes of data transfer. In year 2, we tested the usability of the <span class="hlt">WINDS</span> for three-way teleconferencing with virtual slides. Facilities in Iwate (northern Japan), Tokyo, and Okinawa were connected via the <span class="hlt">WINDS</span> and voice conferenced while remotely examining and manipulating virtual slides. Results: Network function parameters measured using ping and Iperf were within acceptable limits. However; stage movement, zoom, and conversation suffered a lag of approximately 0.8 s when using real-time video, and a delay of 60-90 s was experienced when accessing the first virtual slide in a session. No significant lag or inconvenience was experienced during diagnosis and conferencing, and the results were satisfactory. Our hypothesis was confirmed for both remote diagnosis using real-time video and virtual slide systems, and also for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790031432&hterms=lemons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlemons','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790031432&hterms=lemons&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dlemons"><span>Electron heating within interaction zones of simple high-<span class="hlt">speed</span> solar <span class="hlt">wind</span> streams</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Feldman, W. C.; Asbridge, J. R.; Bame, S. J.; Gosling, J. T.; Lemons, D. S.</p> <p>1978-01-01</p> <p>In the present paper, electron heating within the high-<span class="hlt">speed</span> portions of three simple stream-stream interaction zones is studied to further our understanding of the physics of heat flux regulation in interplanetary space. To this end, the thermal signals present in the compressions at the leading edges of the simple high-<span class="hlt">speed</span> streams are analyzed, showing that the data are inconsistent with the Spitzer conductivity. Instead, a polynomial law is found to apply. Its implication concerning the mechanism of interplanetary heat conduction is discussed, and the results of applying this conductivity law to high-<span class="hlt">speed</span> flows inside of 1 AU are studied. A self-consistent model of the radial evolution of electrons in the high-<span class="hlt">speed</span> solar <span class="hlt">wind</span> is proposed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JGRA..119.4981Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JGRA..119.4981Y"><span>A preliminary study of thermosphere and mesosphere <span class="hlt">wind</span> observed by Fabry-Perot over Kelan, China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yu, Tao; Huang, Cong; Zhao, Guangxin; Mao, Tian; Wang, Yungang; Zeng, Zhongcao; Wang, Jingsong; Xia, Chunliang</p> <p>2014-06-01</p> <p>A Fabry-Perot interferometer (FPI) system was deployed in Kelan (38.7°N, 111.6°E), center China in November 2011, which observes the airglows at wavelengths of 892.0 nm, 557.7 nm, and 630.0 nm from OH and OI emissions in the upper atmosphere, to derive the <span class="hlt">wind</span> and temperature at heights around 87 km, 97 km, and 250 km, respectively. From late 2011 through 2013 a series of more than 4500 measurements at each height are validated according to manufacture data quality criteria. By using these data, the morphology of <span class="hlt">wind</span> in the mesosphere and thermosphere is investigated in this study. Preliminary results are as follows: (1) As for the diurnal variation, meridional and <span class="hlt">zonal</span> <span class="hlt">winds</span> at heights of 87 km and 97 km, which are derived through 892.0 nm and 557.7 nm airglows, usually range from -50 m/s to 30 m/s and -50 m/s to 50 m/s, respectively, with typical random errors of about 6-10 m/s at 87 km and 2-3 m/s at 97 km. Meridional <span class="hlt">winds</span> usually are northward at dusk, southward at middle night, and back to northward at dawn; and <span class="hlt">zonal</span> <span class="hlt">winds</span> usually are eastward at dusk, westward at middle night, and back to eastward at dawn. The monthly mean <span class="hlt">winds</span> are in good agreement with those of HWM93 results. Meridional and <span class="hlt">zonal</span> <span class="hlt">winds</span> at a height of 250 km, which are derived through 630.0 nm nightglow, range from -110 m/s to 80 m/s with typical random errors of about 8-10 m/s. Meridional <span class="hlt">winds</span> usually are northward at dusk, southward at middle night, and back to northward at dawn; and <span class="hlt">zonal</span> <span class="hlt">winds</span> usually are eastward at dusk, zero at middle night, and westward at dawn; and they are also well consistent with HWM93 results. (2) As for the seasonal variation, meridional <span class="hlt">winds</span> at the heights of 87 km and 97 km have a visible annual variation at 12-17 LT and with a little semiannual variation at all other hours, but the <span class="hlt">zonal</span> <span class="hlt">winds</span> at the heights of 87 km and 97 km have a semiannual variation all night. The seasonal dependence of the <span class="hlt">winds</span>, both meridional and <span class="hlt">zonal</span> <span class="hlt">winds</span>, at the height</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=PIA01113&hterms=background+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbackground%2Bwind','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=PIA01113&hterms=background+wind&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dbackground%2Bwind"><span><span class="hlt">Winds</span> Near Jupiter's Belt-Zone Boundary</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1997-01-01</p> <p>Time Sequence of a belt-zone boundary near Jupiter's equator. These mosaics show Jupiter's appearance at 757 nanometers (near-infrared) and were taken nine hours apart. Images at 757 nanometers show features of Jupiter's primary visible cloud deck.<p/>Jupiter's atmospheric circulation is dominated by alternating jets of east/west (<span class="hlt">zonal</span>) <span class="hlt">winds</span>. The bands have different widths and <span class="hlt">wind</span> <span class="hlt">speeds</span> but have remained constant as long as telescopes and spacecraft have measured them. A strong eastward jet is made visible as it stretches the clouds just below the center of this mosaic. The maximum <span class="hlt">wind</span> <span class="hlt">speed</span> of this jet is 128 meters per second (286 miles per hour). Features on this jet move about one quarter of the width of the mosaic. All the features visible in these mosaics are moving eastward (right).<p/>North is at the top. The mosaic covers latitudes -13 to +3 degrees and is centered at longitude 282 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on November 5th, 1996, at a range of 1.2 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft.<p/>The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.<p/>This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1342994-sensitivity-turbine-height-wind-speeds-parameters-planetary-boundary-layer-surface-layer-schemes-weather-research-forecasting-model','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1342994-sensitivity-turbine-height-wind-speeds-parameters-planetary-boundary-layer-surface-layer-schemes-weather-research-forecasting-model"><span>Sensitivity of turbine-height <span class="hlt">wind</span> <span class="hlt">speeds</span> to parameters in planetary boundary-layer and surface-layer schemes in the weather research and forecasting model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Yang, Ben; Qian, Yun; Berg, Larry K.; ...</p> <p>2016-07-21</p> <p>We evaluate the sensitivity of simulated turbine-height <span class="hlt">wind</span> <span class="hlt">speeds</span> to 26 parameters within the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height <span class="hlt">wind</span> <span class="hlt">speeds</span>. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. Themore » parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height <span class="hlt">wind</span> <span class="hlt">speeds</span>. A larger Prandtl number results in smaller nighttime <span class="hlt">wind</span> <span class="hlt">speeds</span>. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of <span class="hlt">wind</span> <span class="hlt">speed</span>. All of the above parameters significantly affect the vertical profiles of <span class="hlt">wind</span> <span class="hlt">speed</span> and the magnitude of <span class="hlt">wind</span> shear. Lastly, the relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/1342994','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/1342994"><span>Sensitivity of turbine-height <span class="hlt">wind</span> <span class="hlt">speeds</span> to parameters in planetary boundary-layer and surface-layer schemes in the weather research and forecasting model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Yang, Ben; Qian, Yun; Berg, Larry K.</p> <p></p> <p>We evaluate the sensitivity of simulated turbine-height <span class="hlt">wind</span> <span class="hlt">speeds</span> to 26 parameters within the Mellor–Yamada–Nakanishi–Niino (MYNN) planetary boundary-layer scheme and MM5 surface-layer scheme of the Weather Research and Forecasting model over an area of complex terrain. An efficient sampling algorithm and generalized linear model are used to explore the multiple-dimensional parameter space and quantify the parametric sensitivity of simulated turbine-height <span class="hlt">wind</span> <span class="hlt">speeds</span>. The results indicate that most of the variability in the ensemble simulations is due to parameters related to the dissipation of turbulent kinetic energy (TKE), Prandtl number, turbulent length scales, surface roughness, and the von Kármán constant. Themore » parameter associated with the TKE dissipation rate is found to be most important, and a larger dissipation rate produces larger hub-height <span class="hlt">wind</span> <span class="hlt">speeds</span>. A larger Prandtl number results in smaller nighttime <span class="hlt">wind</span> <span class="hlt">speeds</span>. Increasing surface roughness reduces the frequencies of both extremely weak and strong airflows, implying a reduction in the variability of <span class="hlt">wind</span> <span class="hlt">speed</span>. All of the above parameters significantly affect the vertical profiles of <span class="hlt">wind</span> <span class="hlt">speed</span> and the magnitude of <span class="hlt">wind</span> shear. Lastly, the relative contributions of individual parameters are found to be dependent on both the terrain slope and atmospheric stability.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990JGR....9522275B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990JGR....9522275B"><span>Seasat scatterometer versus scanning multichannel microwave radiometer <span class="hlt">wind</span> <span class="hlt">speeds</span>: A comparison on a global scale</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Boutin, J.; Etcheto, J.</p> <p>1990-12-01</p> <p>The <span class="hlt">wind</span> <span class="hlt">speeds</span> obtained from the Seasat A scatterometer system (SASS) and scanning multichannel microwave radiometer (SMMR) using two different algorithms were compared on a global scale. The temperature dependence of the sea surface emissivity was shown to be incorrectly modelled. After correcting this effect, regional differences up to ± 3 m s-1 are still observed between both instruments, even though they balance in global averaging, resulting in no bias between the global data sets. Validation experiments of satellite <span class="hlt">wind</span> <span class="hlt">speeds</span> should take into account this possibility of regional biases and insure the validity of the measurements everywhere in the global ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=350708','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=350708"><span>Effect of windbreaks on <span class="hlt">wind</span> <span class="hlt">speed</span> and canker incidence on grapefruit</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>For fresh grapefruit, the goal is to maximize pack-out by minimizing canker lesions on fruit. The objective of these trials was to determine the relationship between <span class="hlt">wind</span> <span class="hlt">speed</span> and incidence and severity of citrus canker on 5 to 7 yr-old Ruby Red grapefruit trees located in two trial blocks (~4.5 ha...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780022201','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780022201"><span>Self streamlining <span class="hlt">wind</span> tunnel: Further low <span class="hlt">speed</span> testing and final design studies for the transonic facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wolf, S. W. D.</p> <p>1978-01-01</p> <p>Work was continued with the low <span class="hlt">speed</span> self streamlining <span class="hlt">wind</span> tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional <span class="hlt">wind</span> tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air <span class="hlt">speeds</span> to investigate the effects of such changes (perhaps through changes in Reynold's number and freestream turbulence levels) on airfoil data and wall contours. Mechanical design analyses for the transonic self-streamlining <span class="hlt">wind</span> tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility, which will eventually allow on-line computer operation of the <span class="hlt">wind</span> tunnel, was outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713810D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713810D"><span>Application of stochastic methods for <span class="hlt">wind</span> <span class="hlt">speed</span> forecasting and <span class="hlt">wind</span> turbines design at the area of Thessaly, Greece</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dimitriadis, Panayiotis; Lazaros, Lappas; Daskalou, Olympia; Filippidou, Ariadni; Giannakou, Marianna; Gkova, Eleni; Ioannidis, Romanos; Polydera, Angeliki; Polymerou, Eleni; Psarrou, Eleftheria; Vyrini, Alexandra; Papalexiou, Simon; Koutsoyiannis, Demetris</p> <p>2015-04-01</p> <p>Several methods exist for estimating the statistical properties of <span class="hlt">wind</span> <span class="hlt">speed</span>, most of them being deterministic or probabilistic, disregarding though its long-term behaviour. Here, we focus on the stochastic nature of <span class="hlt">wind</span>. After analyzing several historical timeseries at the area of interest (AoI) in Thessaly (Greece), we show that a Hurst-Kolmogorov (HK) behaviour is apparent. Thus, disregarding the latter could lead to unrealistic predictions and <span class="hlt">wind</span> load situations, causing some impact on the energy production and management. Moreover, we construct a stochastic model capable of preserving the HK behaviour and we produce synthetic timeseries using a Monte-Carlo approach to estimate the future <span class="hlt">wind</span> loads in the AoI. Finally, we identify the appropriate types of <span class="hlt">wind</span> turbines for the AoI (based on the IEC 61400 standards) and propose several industrial solutions. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1261443-frequency-regulation-oscillation-damping-contributions-variable-speed-wind-generators-eastern-interconnection-ei','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1261443-frequency-regulation-oscillation-damping-contributions-variable-speed-wind-generators-eastern-interconnection-ei"><span>Frequency Regulation and Oscillation Damping Contributions of Variable-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Generators in the U.S. Eastern Interconnection (EI)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Liu, Yong; Gracia, Jose R,; King, Jr, Thomas J.; ...</p> <p>2014-05-16</p> <p>The U.S. Eastern Interconnection (EI) is one of the largest electric power grids in the world and is expected to have difficulties in dealing with frequency regulation and oscillation damping issues caused by the increasing <span class="hlt">wind</span> power. On the other side, variable-<span class="hlt">speed</span> <span class="hlt">wind</span> generators can actively engage in frequency regulation or oscillation damping with supplementary control loops. This paper creates a 5% <span class="hlt">wind</span> power penetration simulation scenario based on the 16 000-bus EI system dynamic model and developed the user-defined <span class="hlt">wind</span> electrical control model in PSS (R) E that incorporates additional frequency regulation and oscillation damping control loops. We evaluatedmore » the potential contributions of variable-<span class="hlt">speed</span> <span class="hlt">wind</span> generations to the EI system frequency regulation and oscillation damping, and simulation results demonstrate that current and future penetrations of <span class="hlt">wind</span> power are promising in the EI system frequency regulation and oscillation damping.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/22218477-zonal-flow-pattern-formation','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/22218477-zonal-flow-pattern-formation"><span><span class="hlt">Zonal</span> flow as pattern formation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Parker, Jeffrey B.; Krommes, John A.</p> <p>2013-10-15</p> <p><span class="hlt">Zonal</span> flows are well known to arise spontaneously out of turbulence. We show that for statistically averaged equations of the stochastically forced generalized Hasegawa-Mima model, steady-state <span class="hlt">zonal</span> flows, and inhomogeneous turbulence fit into the framework of pattern formation. There are many implications. First, the wavelength of the <span class="hlt">zonal</span> flows is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20130001913','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20130001913"><span>Observations of C-Band Brightness Temperature and Ocean Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> and Rain Rate in Hurricanes Earl And Karl (2010)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, Timothy; James, Mark; Roberts, Brent J.; Biswax, Sayak; Uhlhorn, Eric; Black, Peter; Linwood Jones, W.; Johnson, Jimmy; Farrar, Spencer; Sahawneh, Saleem</p> <p>2012-01-01</p> <p>Ocean surface emission is affected by: a) Sea surface temperature. b) <span class="hlt">Wind</span> <span class="hlt">speed</span> (foam fraction). c) Salinity After production of calibrated Tb fields, geophysical fields <span class="hlt">wind</span> <span class="hlt">speed</span> and rain rate (or column) are retrieved. HIRAD utilizes NASA Instrument Incubator Technology: a) Provides unique observations of sea surface <span class="hlt">wind</span>, 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 <span class="hlt">wind</span> <span class="hlt">speed</span>, b) Version 2: dual ]pol for ocean <span class="hlt">wind</span> 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.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760004998','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760004998"><span>An experimental study of several <span class="hlt">wind</span> tunnel wall configurations using two V/STOL model configurations. [low <span class="hlt">speed</span> <span class="hlt">wind</span> tunnels</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Binion, T. W., Jr.</p> <p>1975-01-01</p> <p>Experiments were conducted in the low <span class="hlt">speed</span> <span class="hlt">wind</span> tunnel using two V/STOL models, a jet-flap and a jet-in-fuselage configuration, to search for a <span class="hlt">wind</span> tunnel wall configuration to minimize wall interference on V/STOL models. Data were also obtained on the jet-flap model with a uniform slotted wall configuration to provide comparisons between theoretical and experimental wall interference. A test section configuration was found which provided some data in reasonable agreement with interference-free results over a wide range of momentum coefficients.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMEP51F..06G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMEP51F..06G"><span>Shelter Index and a simple <span class="hlt">wind</span> <span class="hlt">speed</span> parameter to characterize vegetation control of sand transport threshold and Flu</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gillies, J. A.; Nield, J. M.; Nickling, W. G.; Furtak-Cole, E.</p> <p>2014-12-01</p> <p><span class="hlt">Wind</span> erosion and dust emissions occur in many dryland environments from a range of surfaces with different types and amounts of vegetation. Understanding how vegetation modulates these processes remains a research challenge. Here we present results from a study that examines the relationship between an index of shelter (SI=distance from a point to the nearest upwind vegetation/vegetation height) and particle threshold expressed as the ratio of <span class="hlt">wind</span> <span class="hlt">speed</span> measured at 0.45 times the mean plant height divided by the <span class="hlt">wind</span> <span class="hlt">speed</span> at 17 m when saltation commences, and saltation flux. The results are used to evaluate SI as a parameter to characterize the influence of vegetation on local <span class="hlt">winds</span> and sediment transport conditions. <span class="hlt">Wind</span> <span class="hlt">speed</span>, <span class="hlt">wind</span> direction, saltation activity and point saltation flux were measured at 35 locations in defined test areas (~13,000 m2) in two vegetation communities: mature streets of mesquite covered nebkhas and incipient nebkhas dominated by low mesquite plants. Measurement positions represent the most open areas, and hence those places most susceptible to <span class="hlt">wind</span> erosion among the vegetation elements. Shelter index was calculated for each measurement position for each 10° <span class="hlt">wind</span> direction bin using digital elevation models for each site acquired using terrestrial laser scanning. SI can show the susceptibility to <span class="hlt">wind</span> erosion at different time scales, i.e., event, seasonal, or annual, but in a supply-limited system it can fail to define actual flux amounts due to a lack of knowledge of the distribution of sediment across the surface of interest with respect to the patterns of SI.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.4545K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.4545K"><span>Is there any trend change in <span class="hlt">wind</span> <span class="hlt">speed</span> in the mid- 1990s in the stratosphere?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Krizan, Peter</p> <p>2017-04-01</p> <p>This poster tries to explain the reasons for trend change of the stratospheric <span class="hlt">wind</span> <span class="hlt">speed</span> in the mid-1990s. In the areas of negative (positive) <span class="hlt">wind</span> <span class="hlt">speed</span> trend before 1995 the positive (negative) trend is observed after this point Similar change is observed also for total ozone where we observe negative trend before 1995 and positive one after. We use MERRA reanalysis monthly means of the geopotential height from January to March. We suppose the position and strength of polar vortex and Aleutian high plays here very important role.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017FrME...12..377H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017FrME...12..377H"><span>Power maximization of variable-<span class="hlt">speed</span> variable-pitch <span class="hlt">wind</span> turbines using passive adaptive neural fault tolerant control</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Habibi, Hamed; Rahimi Nohooji, Hamed; Howard, Ian</p> <p>2017-09-01</p> <p>Power maximization has always been a practical consideration in <span class="hlt">wind</span> turbines. The question of how to address optimal power capture, especially when the system dynamics are nonlinear and the actuators are subject to unknown faults, is significant. This paper studies the control methodology for variable-<span class="hlt">speed</span> variable-pitch <span class="hlt">wind</span> turbines including the effects of uncertain nonlinear dynamics, system fault uncertainties, and unknown external disturbances. The nonlinear model of the <span class="hlt">wind</span> turbine is presented, and the problem of maximizing extracted energy is formulated by designing the optimal desired states. With the known system, a model-based nonlinear controller is designed; then, to handle uncertainties, the unknown nonlinearities of the <span class="hlt">wind</span> turbine are estimated by utilizing radial basis function neural networks. The adaptive neural fault tolerant control is designed passively to be robust on model uncertainties, disturbances including <span class="hlt">wind</span> <span class="hlt">speed</span> and model noises, and completely unknown actuator faults including generator torque and pitch actuator torque. The Lyapunov direct method is employed to prove that the closed-loop system is uniformly bounded. Simulation studies are performed to verify the effectiveness of the proposed method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMOS43A1255H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMOS43A1255H"><span>Walker Circulation, El Niño and La Niña</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Halpern, D.</p> <p>2014-12-01</p> <p>Ocean surface <span class="hlt">wind</span> vector is likely the critical variable to predict onset, maintenance and dissipation of El Niño and La Niña. Analyses of Sea<span class="hlt">Winds</span> and ASCAT 10-m height (called "surface") vector <span class="hlt">winds</span> in the Atlantic, Indian and Pacific Oceans from 1°S-1°N during March 2000 - June 2011 revealed the longitudinal distribution of the surface <span class="hlt">zonal</span> <span class="hlt">wind</span> component associated with the Walker Circulation. In the Pacific Ocean east of 140°E and west of 85°W, the mean <span class="hlt">wind</span> direction was westward towards the maritime continent with maximum mean <span class="hlt">zonal</span> <span class="hlt">wind</span> <span class="hlt">speed</span> (- 6.5 m s-1) at 150°W; east of 85°W the mean direction was toward the convection zone over South America. Four El Niños and five La Niñas occurred from March 2000 - June 2011. In the Pacific from 150°E to 160°W, the average El Niño (La Niña) westward <span class="hlt">wind</span> <span class="hlt">speed</span> was 2 m s-1 (1 m s-1) smaller (larger) than normal. In the west Pacific, the variation in westward <span class="hlt">wind</span> <span class="hlt">speeds</span> in El Niño and La Niña conditions relative to normal conditions would be expected to substantially uplift the thermocline during El Niño compared to La Niña, which is consistent with conventional wisdom. In the east Pacific from 130°W - 100°W, average El Niño westward <span class="hlt">wind</span> <span class="hlt">speeds</span> were less than normal and La Niña conditions by 0.5 m s-1 and 1 m s-1, respectively. The "central" Pacific nature of the El Niños may have influenced the smaller difference between El Niño and La Niña westward <span class="hlt">wind</span> <span class="hlt">speeds</span> in the east Pacific compared to the west Pacific. Analyses of longitudinal distributions of thermocline depths will be discussed. Surface <span class="hlt">zonal</span> <span class="hlt">wind</span> <span class="hlt">speeds</span> in the Atlantic and Indian Oceans showed no evidence of El Niño and La Niña; surface meridional <span class="hlt">winds</span> showed an apparent response in the Indian and Pacific Oceans but not in the Atlantic Ocean. At 700-m height, the MISR <span class="hlt">zonal</span> <span class="hlt">wind</span> component in the Atlantic, Indian and Pacific Oceans had similar features as those at the surface, except in the east Pacific where the westward</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ESASP.740E..68G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ESASP.740E..68G"><span>Use of the Azimuth Wavelength Cut-Off to Retrieve the Sea Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> from Sentinel 1 and COSMO-SkyMed SAR Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grieco, G.; Nirchio, F.; Montuori, A.; Migliaccio, M.; Lin, W.; Portabella, M.</p> <p>2016-08-01</p> <p>The dependency of the azimuth wavelength cut-off on the <span class="hlt">wind</span> <span class="hlt">speed</span> has been studied through a dataset of Sentinel-1 multi look SAR images co-located with <span class="hlt">wind</span> <span class="hlt">speed</span> measurements, significant wave height and mean wave direction from ECMWF operational output.A Geophysical Model Function (GMF) has been fitted and a retrieval exercise has been done comparing the results to a set of independent <span class="hlt">wind</span> <span class="hlt">speed</span> scatterometer measurements of the Chinese mission HY-2A. The preliminary results show that the dependency of the azimuth cut-off on the <span class="hlt">wind</span> <span class="hlt">speed</span> is linear only for fully developed sea states and that the agreement between the retrieved values and the measurements is good especially for high <span class="hlt">wind</span> <span class="hlt">speed</span>.A similar approach has been used to assess the dependency of the azimuth cut-off also for X-band COSMO-SkyMed data. The dataset is still incomplete but the preliminary results show a similar trend.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26271035','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26271035"><span>The Impacts of <span class="hlt">Wind</span> <span class="hlt">Speed</span> Trends and 30-Year Variability in Relation to Hydroelectric Reservoir Inflows on <span class="hlt">Wind</span> Power in the Pacific Northwest.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cross, Benjamin D; Kohfeld, Karen E; Bailey, Joseph; Cooper, Andrew B</p> <p>2015-01-01</p> <p>In hydroelectric dominated systems, the value and benefits of energy are higher during extended dry periods and lower during extended or extreme wet periods. By accounting for regional and temporal differences in the relationship between <span class="hlt">wind</span> <span class="hlt">speed</span> and reservoir inflow behavior during <span class="hlt">wind</span> farm site selection, the benefits of energy diversification can be maximized. The goal of this work was to help maximize the value of <span class="hlt">wind</span> power by quantifying the long-term (30-year) relationships between <span class="hlt">wind</span> <span class="hlt">speed</span> and streamflow behavior, using British Columbia (BC) and the Pacific Northwest (PNW) as a case study. Clean energy and self-sufficiency policies in British BC make the benefits of increased generation during low streamflow periods particularly large. <span class="hlt">Wind</span> density (WD) estimates from a height of 10m (North American Regional Reanalysis, NARR) were correlated with cumulative usable inflows (CUI) for BC (collected from BC Hydro) for 1979-2010. The strongest WD-CUI correlations were found along the US coast (r ~0.55), whereas generally weaker correlations were found in northern regions, with negative correlations (r ~ -0.25) along BC's North Coast. Furthermore, during the lowest inflow years, WD anomalies increased by up to 40% above average values for the North Coast. Seasonally, high flows during the spring freshet were coincident with widespread negative WD anomalies, with a similar but opposite pattern for low inflow winter months. These poorly or negatively correlated sites could have a moderating influence on climate related variability in provincial electricity supply, by producing greater than average generation in low inflow years and reduced generation in wet years. <span class="hlt">Wind</span> <span class="hlt">speed</span> and WD trends were also analyzed for all NARR grid locations, which showed statistically significant positive trends for most of the PNW and the largest increases along the Pacific Coast.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4535905','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4535905"><span>The Impacts of <span class="hlt">Wind</span> <span class="hlt">Speed</span> Trends and 30-Year Variability in Relation to Hydroelectric Reservoir Inflows on <span class="hlt">Wind</span> Power in the Pacific Northwest</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cross, Benjamin D.; Kohfeld, Karen E.; Bailey, Joseph; Cooper, Andrew B.</p> <p>2015-01-01</p> <p>In hydroelectric dominated systems, the value and benefits of energy are higher during extended dry periods and lower during extended or extreme wet periods. By accounting for regional and temporal differences in the relationship between <span class="hlt">wind</span> <span class="hlt">speed</span> and reservoir inflow behavior during <span class="hlt">wind</span> farm site selection, the benefits of energy diversification can be maximized. The goal of this work was to help maximize the value of <span class="hlt">wind</span> power by quantifying the long-term (30-year) relationships between <span class="hlt">wind</span> <span class="hlt">speed</span> and streamflow behavior, using British Columbia (BC) and the Pacific Northwest (PNW) as a case study. Clean energy and self-sufficiency policies in British BC make the benefits of increased generation during low streamflow periods particularly large. <span class="hlt">Wind</span> density (WD) estimates from a height of 10m (North American Regional Reanalysis, NARR) were correlated with cumulative usable inflows (CUI) for BC (collected from BC Hydro) for 1979–2010. The strongest WD-CUI correlations were found along the US coast (r ~0.55), whereas generally weaker correlations were found in northern regions, with negative correlations (r ~ -0.25) along BC’s North Coast. Furthermore, during the lowest inflow years, WD anomalies increased by up to 40% above average values for the North Coast. Seasonally, high flows during the spring freshet were coincident with widespread negative WD anomalies, with a similar but opposite pattern for low inflow winter months. These poorly or negatively correlated sites could have a moderating influence on climate related variability in provincial electricity supply, by producing greater than average generation in low inflow years and reduced generation in wet years. <span class="hlt">Wind</span> <span class="hlt">speed</span> and WD trends were also analyzed for all NARR grid locations, which showed statistically significant positive trends for most of the PNW and the largest increases along the Pacific Coast. PMID:26271035</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110008803','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110008803"><span>Observations During GRIP from HIRAD: Ocean Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> and Rain Rate</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Miller, Timothy L.; James, M. W.; Jones, L.; Ruf, C. S.; Uhlhorn, E. W.; Bailey, M. C.; Buckley, C. D.; Simmons, D. E.; Johnstone, S.; Peterson, A.; <a style="text-decoration: none; " href="javascript:void(0); " onClick="displayelement('author_20110008803'); toggleEditAbsImage('author_20110008803_show'); toggleEditAbsImage('author_20110008803_hide'); "> <img style="display:inline; width:12px; height:12px; " src="images/arrow-up.gif" width="12" height="12" border="0" alt="hide" id="author_20110008803_show"> <img style="width:12px; height:12px; display:none; " src="images/arrow-down.gif" width="12" height="12" border="0" alt="hide" id="author_20110008803_hide"></p> <p>2011-01-01</p> <p>HIRAD (Hurricane Imaging Radiometer) flew on the WB-57 during NASA's GRIP (Genesis and Rapid Intensification Processes) campaign in August - September of 2010. HIRAD is a new C-band radiometer using a synthetic thinned array radiometer (STAR) technology to obtain cross-track resolution of approximately 3 degrees, out to approximately 60 degrees to each side of nadir. By obtaining measurements of emissions at 4, 5, 6, and 6.6 GHz, observations of ocean surface <span class="hlt">wind</span> <span class="hlt">speed</span> and rain rate can be inferred. This 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. The advantage of HIRAD over SFMR is that HIRAD can observe a +/- 60-degree swath, rather than a single footprint at nadir angle. Results from the flights during the GRIP campaign will be shown, including images of brightness temperatures, <span class="hlt">wind</span> <span class="hlt">speed</span>, and rain rate. To the extent possible, comparisons will be made with observations from other instruments on the GRIP campaign, for which HIRAD observations are either directly comparable or are complementary. Potential impacts on operational ocean surface <span class="hlt">wind</span> analyses and on numerical weather forecasts will also be discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930063212&hterms=Administration+concept&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAdministration%2Bconcept','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930063212&hterms=Administration+concept&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DAdministration%2Bconcept"><span>Low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel test results of the Canard Rotor/Wing concept</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bass, Steven M.; Thompson, Thomas L.; Rutherford, John W.; Swanson, Stephen</p> <p>1993-01-01</p> <p>The Canard Rotor/Wing (CRW), a high-<span class="hlt">speed</span> rotorcraft concept, was tested at the National Aeronautics and Space Administration (NASA) Ames Research Center's 40- by 80-Foot <span class="hlt">Wind</span> Tunnel in Mountain View, California. The 1/5-scale model was tested to identify certain low-<span class="hlt">speed</span>, fixed-wing, aerodynamic characteristics of the configuration and investigate the effectiveness of two empennages, an H-Tail and a T-Tail. The paper addresses the principal test objectives and the results achieved in the <span class="hlt">wind</span> tunnel test. These are summarized as: i) drag build-up and differences between the H-Tail and T-Tail configuration, ii) longitudinal stability of the H-Tail and T-Tail configurations in the conversion and cruise modes, iii) control derivatives for the canard and elevator in the conversion and cruise modes, iv) aerodynamic characteristics of varying the rotor/wing azimuth position, and v) canard and tail lift/trim capability for conversion conditions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850005137','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850005137"><span>Multisensor satellite data integration for sea surface <span class="hlt">wind</span> <span class="hlt">speed</span> and direction determination</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Glackin, D. L.; Pihos, G. G.; Wheelock, S. L.</p> <p>1984-01-01</p> <p>Techniques to integrate meteorological data from various satellite sensors to yield a global measure of sea surface <span class="hlt">wind</span> <span class="hlt">speed</span> and direction for input to the Navy's operational weather forecast models were investigated. The sensors were launched or will be launched, specifically the GOES visible and infrared imaging sensor, the Nimbus-7 SMMR, and the DMSP SSM/I instrument. An algorithm for the extrapolation to the sea surface of <span class="hlt">wind</span> directions as derived from successive GOES cloud images was developed. This <span class="hlt">wind</span> veering algorithm is relatively simple, accounts for the major physical variables, and seems to represent the best solution that can be found with existing data. An algorithm for the interpolation of the scattered observed data to a common geographical grid was implemented. The algorithm is based on a combination of inverse distance weighting and trend surface fitting, and is suited to combing <span class="hlt">wind</span> data from disparate sources.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/861052','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/861052"><span>Low <span class="hlt">Wind</span> <span class="hlt">Speed</span> Turbine Project Phase II: The Application of Medium-Voltage Electrical Apparatus to the Class of Variable <span class="hlt">Speed</span> Multi-Megawatt Low <span class="hlt">Wind</span> <span class="hlt">Speed</span> Turbines; 15 June 2004--30 April 2005</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Erdman, W.; Behnke, M.</p> <p>2005-11-01</p> <p>Kilowatt ratings of modern <span class="hlt">wind</span> turbines have progressed rapidly from 50 kW to 1,800 kW over the past 25 years, with 3.0- to 7.5-MW turbines expected in the next 5 years. The premise of this study is simple: The rapid growth of <span class="hlt">wind</span> turbine power ratings and the corresponding growth in turbine electrical generation systems and associated controls are quickly making low-voltage (LV) electrical design approaches cost-ineffective. This report provides design detail and compares the cost of energy (COE) between commercial LV-class <span class="hlt">wind</span> power machines and emerging medium-voltage (MV)-class multi-megawatt <span class="hlt">wind</span> technology. The key finding is that a 2.5% reductionmore » in the COE can be achieved by moving from LV to MV systems. This is a conservative estimate, with a 3% to 3.5% reduction believed to be attainable once purchase orders to support a 250-turbine/year production level are placed. This evaluation considers capital costs as well as installation, maintenance, and training requirements for <span class="hlt">wind</span> turbine maintenance personnel. Subsystems investigated include the generator, pendant cables, variable-<span class="hlt">speed</span> converter, and padmount transformer with switchgear. Both current-source and voltage-source converter/inverter MV topologies are compared against their low-voltage, voltage-source counterparts at the 3.0-, 5.0-, and 7.5-MW levels.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780022531','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780022531"><span>Estimates of oceanic surface <span class="hlt">wind</span> <span class="hlt">speed</span> and direction using orthogonal beam scatterometer measurements and comparison of recent sea scattering theories</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Moore, R. K.; Fung, A. K.; Dome, G. J.; Birrer, I. J.</p> <p>1978-01-01</p> <p>The <span class="hlt">wind</span> direction properties of radar backscatter from the sea were empirically modelled using a cosine Fourier series through the 4th harmonic in <span class="hlt">wind</span> direction (referenced to upwind). A comparison with 1975 JONSWAP (Joint North Sea Wave Project) scatterometer data, at incidence angles of 40 and 65, indicates that effects to third and fourth harmonics are negligible. Another important result is that the Fourier coefficients through the second harmonic are related to <span class="hlt">wind</span> <span class="hlt">speed</span> by a power law expression. A technique is also proposed to estimate the <span class="hlt">wind</span> <span class="hlt">speed</span> and direction over the ocean from two orthogonal scattering measurements. A comparison between two different types of sea scatter theories, one type presented by the work of Wright and the other by that of Chan and Fung, was made with recent scatterometer measurements. It demonstrates that a complete scattering model must include some provisions for the anisotropic characteristics of the sea scatter, and use a sea spectrum which depends upon <span class="hlt">wind</span> <span class="hlt">speed</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006AdSpR..38.2610A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006AdSpR..38.2610A"><span>Theoretical and experimental <span class="hlt">zonal</span> drift velocities of the ionospheric plasma bubbles over the Brazilian region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Arruda, Daniela C. S.; Sobral, J. H. A.; Abdu, M. A.; Castilho, Vivian M.; Takahashi, H.; Medeiros, A. F.; Buriti, R. A.</p> <p>2006-01-01</p> <p>This work presents equatorial ionospheric plasma bubble <span class="hlt">zonal</span> drift velocity observations and their comparison with model calculations. The bubble <span class="hlt">zonal</span> velocities were measured using airglow OI630 nm all-sky digital images and the model calculations were performed taking into account flux-tube integrated Pedersen conductivity and conductivity weighted neutral <span class="hlt">zonal</span> <span class="hlt">winds</span>. The digital images were obtained from an all-sky imaging system operated over the low-latitude station Cachoeira Paulista (Geogr. 22.5S, 45W, dip angle 31.5S) during the period from October 1998 to August 2000. Out of the 138 nights of imager observation, 29 nights with the presence of plasma bubbles are used in this study. These 29 nights correspond to geomagnetically rather quiet days (∑K P < 24+) and were grouped according to season. During the early night hours, the calculated <span class="hlt">zonal</span> drift velocities were found to be larger than the experimental values. The best matching between the calculated and observed <span class="hlt">zonal</span> velocities were seen to be for a few hours around midnight. The model calculation showed two humps around 20 LT and 24 LT that were not present in the data. Average decelerations obtained from linear regression between 20 LT and 24 LT were found to be: (a) Spring 1998, -8.61 ms -1 h -1; (b) Summer 1999, -0.59 ms -1 h -1; (c) Spring 1999, -11.72 ms -1 h -1; and (d) Summer 2000, -8.59 ms -1 h -1. Notice that Summer and Winter here correspond to southern hemisphere Summer and Winter, not northern hemisphere.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780019198','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780019198"><span>Self streamlining <span class="hlt">wind</span> tunnel: Further low <span class="hlt">speed</span> testing and final design studies for the transonic facility</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wolf, S. W. D.</p> <p>1977-01-01</p> <p>Work has continued with the low <span class="hlt">speed</span> self streamlining <span class="hlt">wind</span> tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional <span class="hlt">wind</span> tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air <span class="hlt">speeds</span> to investigate the effects of such changes on airfoil data and wall contours. Mechanical design analyses for the transonic self streamlining <span class="hlt">wind</span> tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility is outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AeoRe..12..135G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AeoRe..12..135G"><span><span class="hlt">Wind</span> <span class="hlt">speed</span> and sediment transport recovery in the lee of a vegetated and denuded nebkha within a nebkha dune field</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gillies, John A.; Nield, Joanna M.; Nickling, William G.</p> <p>2014-03-01</p> <p>Field observations of scaled <span class="hlt">wind</span> <span class="hlt">speed</span> and sand transport recovery in the lee of a nebka within a field of nebkhas and then subsequently for the nebkha denuded of its vegetation cover were collected. The measurements of <span class="hlt">wind</span> <span class="hlt">speed</span> at 0.4 times the element height indicate that for both conditions <span class="hlt">wind</span> <span class="hlt">speed</span> recovery in the lee is exponential. The porous vegetation cover influences the rate of this recovery being more gradual for the vegetated form. The return to equilibrium <span class="hlt">wind</span> <span class="hlt">speed</span> occurs in both cases at approximately eight element heights. For either case the recovery of shear stress and the return to a constant value occurs much closer to the bluff body form than has been described for porous fences. The recovery of sand transport in the lee appears to be more rapid for the un-vegetated condition, which corresponds to the observed faster rate of <span class="hlt">wind</span> <span class="hlt">speed</span> increase. The observations did not show a continual increase in saltation flux with increasing downwind distance due to the increasing shear stress downwind and the increase that may be expected due to the fetch effect. The change in saltation flux with downwind distance was controlled by the sediment supply, which diminished with downwind distance. The interaction of a changing shear stress and the zone of influence created by the <span class="hlt">wind</span> as it interacts with the roughness dimensions, along with the distribution of sediment available for transport bring increased complexity to modeling sand flux for this type of environment over different temporal scales.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AIPC.1734c0011D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AIPC.1734c0011D"><span>Evaluation of the variability of <span class="hlt">wind</span> <span class="hlt">speed</span> at different heights and its impact on the receiver efficiency of central receiver systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Delgado, A.; Gertig, C.; Blesa, E.; Loza, A.; Hidalgo, C.; Ron, R.</p> <p>2016-05-01</p> <p>Typical plant configurations for Central Receiver Systems (CRS) are comprised of a large field of heliostats which concentrate solar irradiation onto the receiver, which is elevated hundreds of meters above the ground. <span class="hlt">Wind</span> <span class="hlt">speed</span> changes with altitude above ground, impacting on the receiver thermal efficiency due to variations of the convective heat losses. In addition, the physical properties of air vary at high altitudes to a significant degree, which should be considered in the thermal losses calculation. DNV GL has long-reaching experience in <span class="hlt">wind</span> energy assessment with reliable methodologies to reduce the uncertainty of the determination of the <span class="hlt">wind</span> regime. As a part of this study, DNV GL estimates the <span class="hlt">wind</span> <span class="hlt">speed</span> at high altitude for different sites using two methods, a detailed estimation applying the best practices used in the <span class="hlt">wind</span> energy sector based on measurements from various <span class="hlt">wind</span> sensors and a simplified estimation applying the power law (1, 2) using only one <span class="hlt">wind</span> measurement and a representative value for the surface roughness. As a result of the study, a comparison of the <span class="hlt">wind</span> <span class="hlt">speed</span> estimation considering both methods is presented and the impact on the receiver performance for the evaluated case is estimated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AdSpR..45...18H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AdSpR..45...18H"><span>Cosmic ray modulation with a Fisk-type heliospheric magnetic field and a latitude-dependent solar <span class="hlt">wind</span> <span class="hlt">speed</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hitge, M.; Burger, R. A.</p> <p>2010-01-01</p> <p>The effect of a latitude-dependent solar <span class="hlt">wind</span> <span class="hlt">speed</span> on a Fisk heliospheric magnetic field [Fisk, L. A. Motion of the footpoints of heliospheric magnetic field lines at the Sun: implications for recurrent energetic particle events at high heliographic latitudes. J. Geophys. Res. 101, 15547-15553, 1996] was first discussed by Schwadron and Schwadron and McComas [Schwadron, N.A. An explanation for strongly underwound magnetic field in co-rotating rarefaction regions and its relationship to footpoint motion on the the sun. Geophys. Res. Lett. 29, 1-8, 2002. and Schwadron, N.A., McComas, D.J. Heliospheric “FALTS”: favored acceleration locations at the termination shock. Geophys. Res. Lett. 30, 41-1, 2003]. Burger and Sello [Burger, R.A., Sello, P.C. The effect on cosmic ray modulation of a Parker field modified by a latitudinal-dependent solar <span class="hlt">wind</span> <span class="hlt">speed</span>. Adv. Space Res. 35, 643-646, 2005] found a significant effect for a simplified 2D version of a latitude-dependent Fisk-type field while Miyake and Yanagita [Miyake, S., Yanagita, S. The effect of a modified Parker field on the modulation of the galactic cosmic rays. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, 445-448, 2007] found a smaller effect. The current report improves on a previous attempt Hitge and Burger [Hitge, M., Burger, R.A. The effect of a latitude-dependent solar <span class="hlt">wind</span> <span class="hlt">speed</span> on cosmic-ray modulation in a Fisk-type heliospheric magnetic field. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, pp. 449-450, 2007] where the global change in the solar <span class="hlt">wind</span> <span class="hlt">speed</span> and not the local <span class="hlt">speed</span> gradient was emphasized. The sheared Fisk field of Schwadron and McComas [Schwadron, N.A., McComas, D.J. Heliospheric “FALTS”: Favored acceleration locations at the termination shock. Geophys. Res. Lett. 30, 41-1, 2003.) is similar to the current Schwadron-Parker hybrid field. Little difference is found between the effects of a Parker field and a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890015750','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890015750"><span>Low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel performance of high-<span class="hlt">speed</span> counterrotation propellers at angle-of-attack</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hughes, Christopher E.; Gazzaniga, John A.</p> <p>1989-01-01</p> <p>The low-<span class="hlt">speed</span> aerodynamic performance characteristics of two advanced counterrotation pusher-propeller configurations with cruise design Mach numbers of 0.72 were investigated in the NASA Lewis 9- by 15-Foot Low-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel. The tests were conducted at Mach number 0.20, which is representative of the aircraft take-off/landing flight regime. The investigation determined the effect of nonuniform inflow on the propeller performance characteristics for several blade angle settings and a range of rotational <span class="hlt">speeds</span>. The inflow was varied by yawing the propeller model to angle-of-attack by as much as plus or minus 16 degrees and by installing on the counterrotation propeller test rig near the propeller rotors a model simulator of an aircraft engine support pylon and fuselage. The results of the investigation indicated that the low-<span class="hlt">speed</span> performance of the counterrotation propeller configurations near the take-off target operating points were reasonable and were fairly insensitive to changes in model angle-of-attack without the aircraft pylon/fuselage simulators installed on the propeller test rig. When the aircraft pylon/fuselage simulators were installed, small changes in propeller performance were seen at zero angle-of-attack, but fairly large changes in total power coefficient and very large changes of aft-to-forward-rotor torque ratio were produced when the propeller model was taken to angle-of-attack. The propeller net efficiency, though, was fairly insensitive to any changes in the propeller flowfield conditions near the take-off target operating points.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1409495-investigation-high-speed-shaft-bearing-loads-wind-turbine-gearboxes-through-dynamometer-testing','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1409495-investigation-high-speed-shaft-bearing-loads-wind-turbine-gearboxes-through-dynamometer-testing"><span>Investigation of high-<span class="hlt">speed</span> shaft bearing loads in <span class="hlt">wind</span> turbine gearboxes through dynamometer testing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Guo, Yi; Keller, Jonathan</p> <p>2017-11-10</p> <p>Many <span class="hlt">wind</span> turbine gearboxes require repair or replacement well before reaching the end of their design life. The most common failure is bearing axial cracks, commonly called white etching cracks (WECs), which typically occur in the inner raceways of the high-<span class="hlt">speed</span> parallel-stage rolling element bearings. Although the root causes of WECs are debated, one theory is that they are related to routine dynamic operating conditions and occasional transient events prevalent in <span class="hlt">wind</span> turbines that can result in high bearing stress and sliding of the rolling elements. Here, this paper examined <span class="hlt">wind</span> turbine gearbox high-<span class="hlt">speed</span> shaft bearing loads and stresses throughmore » modeling and full-scale dynamometer testing. Bearing outer race loads were directly measured and predicted using a variety of modeling tools in normal operations, misaligned conditions, and transient events particularly prone to bearing sliding. Test data and models of bearing loads were well correlated. Neither operational misalignment due to rotor moments nor static generator misalignment affected the bearing loads when compared with pure-torque conditions. Thus, it is not likely that generator misalignment is a causal factor of WECs. In contrast, during transient events, the bearings experienced alternating periods of high stress, torque reversals, and loads under the minimum requisite at high rotating <span class="hlt">speeds</span> while showing indications of sliding, all of which could be related to the formation of WECs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1409495-investigation-high-speed-shaft-bearing-loads-wind-turbine-gearboxes-through-dynamometer-testing','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1409495-investigation-high-speed-shaft-bearing-loads-wind-turbine-gearboxes-through-dynamometer-testing"><span>Investigation of high-<span class="hlt">speed</span> shaft bearing loads in <span class="hlt">wind</span> turbine gearboxes through dynamometer testing</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Guo, Yi; Keller, Jonathan</p> <p></p> <p>Many <span class="hlt">wind</span> turbine gearboxes require repair or replacement well before reaching the end of their design life. The most common failure is bearing axial cracks, commonly called white etching cracks (WECs), which typically occur in the inner raceways of the high-<span class="hlt">speed</span> parallel-stage rolling element bearings. Although the root causes of WECs are debated, one theory is that they are related to routine dynamic operating conditions and occasional transient events prevalent in <span class="hlt">wind</span> turbines that can result in high bearing stress and sliding of the rolling elements. Here, this paper examined <span class="hlt">wind</span> turbine gearbox high-<span class="hlt">speed</span> shaft bearing loads and stresses throughmore » modeling and full-scale dynamometer testing. Bearing outer race loads were directly measured and predicted using a variety of modeling tools in normal operations, misaligned conditions, and transient events particularly prone to bearing sliding. Test data and models of bearing loads were well correlated. Neither operational misalignment due to rotor moments nor static generator misalignment affected the bearing loads when compared with pure-torque conditions. Thus, it is not likely that generator misalignment is a causal factor of WECs. In contrast, during transient events, the bearings experienced alternating periods of high stress, torque reversals, and loads under the minimum requisite at high rotating <span class="hlt">speeds</span> while showing indications of sliding, all of which could be related to the formation of WECs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4570394','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4570394"><span>An Auto-Tuning PI Control System for an Open-Circuit Low-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel Designed for Greenhouse Technology</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Espinoza, Karlos; Valera, Diego L.; Torres, José A.; López, Alejandro; Molina-Aiz, Francisco D.</p> <p>2015-01-01</p> <p><span class="hlt">Wind</span> tunnels are a key experimental tool for the analysis of airflow parameters in many fields of application. Despite their great potential impact on agricultural research, few contributions have dealt with the development of automatic control systems for <span class="hlt">wind</span> tunnels in the field of greenhouse technology. The objective of this paper is to present an automatic control system that provides precision and <span class="hlt">speed</span> of measurement, as well as efficient data processing in low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel experiments for greenhouse engineering applications. The system is based on an algorithm that identifies the system model and calculates the optimum PI controller. The validation of the system was performed on a cellulose evaporative cooling pad and on insect-proof screens to assess its response to perturbations. The control system provided an accuracy of <0.06 m·s−1 for airflow <span class="hlt">speed</span> and <0.50 Pa for pressure drop, thus permitting the reproducibility and standardization of the tests. The proposed control system also incorporates a fully-integrated software unit that manages the tests in terms of airflow <span class="hlt">speed</span> and pressure drop set points. PMID:26274962</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26274962','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26274962"><span>An Auto-Tuning PI Control System for an Open-Circuit Low-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel Designed for Greenhouse Technology.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Espinoza, Karlos; Valera, Diego L; Torres, José A; López, Alejandro; Molina-Aiz, Francisco D</p> <p>2015-08-12</p> <p><span class="hlt">Wind</span> tunnels are a key experimental tool for the analysis of airflow parameters in many fields of application. Despite their great potential impact on agricultural research, few contributions have dealt with the development of automatic control systems for <span class="hlt">wind</span> tunnels in the field of greenhouse technology. The objective of this paper is to present an automatic control system that provides precision and <span class="hlt">speed</span> of measurement, as well as efficient data processing in low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel experiments for greenhouse engineering applications. The system is based on an algorithm that identifies the system model and calculates the optimum PI controller. The validation of the system was performed on a cellulose evaporative cooling pad and on insect-proof screens to assess its response to perturbations. The control system provided an accuracy of <0.06 m·s(-1) for airflow <span class="hlt">speed</span> and <0.50 Pa for pressure drop, thus permitting the reproducibility and standardization of the tests. The proposed control system also incorporates a fully-integrated software unit that manages the tests in terms of airflow <span class="hlt">speed</span> and pressure drop set points.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060036922&hterms=solar+intensity+measurement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsolar%2Bintensity%2Bmeasurement','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060036922&hterms=solar+intensity+measurement&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dsolar%2Bintensity%2Bmeasurement"><span>Solar <span class="hlt">Wind</span> <span class="hlt">Speed</span> Structure in the Inner Corona at 3-12R(sub)O</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Woo, R.</p> <p>1995-01-01</p> <p>Estimates of solar <span class="hlt">wind</span> <span class="hlt">speed</span> obtained by Armstrong et al. [1986] based on 1983 VLA multiple-station intensity scintillation measurements inside 12 R(sub)O have been compared with white light coronagraph measurements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060036372&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060036372&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS"><span>(abstract) The Distant Tail Behavior During High <span class="hlt">Speed</span> Solar <span class="hlt">Wind</span> Streams and Magnetic Storms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ho, C. M.; Tsurutani, B. T.</p> <p>1996-01-01</p> <p>We have examined the ISEE-3 distant tail data during three intense magnetic storms and have identified the tail response to high <span class="hlt">speed</span> solar <span class="hlt">wind</span> streams, interplanetary magnetic clouds, and near-Earth storms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.7680K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.7680K"><span>High <span class="hlt">speed</span> video shooting with continuous-wave laser illumination in laboratory modeling of <span class="hlt">wind</span> - wave interaction</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kandaurov, Alexander; Troitskaya, Yuliya; Caulliez, Guillemette; Sergeev, Daniil; Vdovin, Maxim</p> <p>2014-05-01</p> <p>Three examples of usage of high-<span class="hlt">speed</span> video filming in investigation of <span class="hlt">wind</span>-wave interaction in laboratory conditions is described. Experiments were carried out at the <span class="hlt">Wind</span> - wave stratified flume of IAP RAS (length 10 m, cross section of air channel 0.4 x 0.4 m, <span class="hlt">wind</span> velocity up to 24 m/s) and at the Large Air-Sea Interaction Facility (LASIF) - MIO/Luminy (length 40 m, cross section of air channel 3.2 x 1.6 m, <span class="hlt">wind</span> velocity up to 10 m/s). A combination of PIV-measurements, optical measurements of water surface form and wave gages were used for detailed investigation of the characteristics of the <span class="hlt">wind</span> flow over the water surface. The modified PIV-method is based on the use of continuous-wave (CW) laser illumination of the airflow seeded by particles and high-<span class="hlt">speed</span> video. During the experiments on the <span class="hlt">Wind</span> - wave stratified flume of IAP RAS Green (532 nm) CW laser with 1.5 Wt output power was used as a source for light sheet. High <span class="hlt">speed</span> digital camera Videosprint (VS-Fast) was used for taking visualized air flow images with the frame rate 2000 Hz. Velocity air flow field was retrieved by PIV images processing with adaptive cross-correlation method on the curvilinear grid following surface wave profile. The mean <span class="hlt">wind</span> velocity profiles were retrieved using conditional in phase averaging like in [1]. In the experiments on the LASIF more powerful Argon laser (4 Wt, CW) was used as well as high-<span class="hlt">speed</span> camera with higher sensitivity and resolution: Optronics Camrecord CR3000x2, frame rate 3571 Hz, frame size 259×1696 px. In both series of experiments spherical 0.02 mm polyamide particles with inertial time 7 ms were used for seeding airflow. New particle seeding system based on utilization of air pressure is capable of injecting 2 g of particles per second for 1.3 - 2.4 s without flow disturbance. Used in LASIF this system provided high particle density on PIV-images. In combination with high-resolution camera it allowed us to obtain momentum fluxes directly from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1411325-evaluation-different-inertial-control-methods-variable-speed-wind-turbines-simulated-fatigue-aerodynamic-structures-turbulence-fast','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1411325-evaluation-different-inertial-control-methods-variable-speed-wind-turbines-simulated-fatigue-aerodynamic-structures-turbulence-fast"><span>Evaluation of different inertial control methods for variable-<span class="hlt">speed</span> <span class="hlt">wind</span> turbines simulated by fatigue, aerodynamic, structures and turbulence (FAST)</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Wang, Xiao; Gao, Wenzhong; Scholbrock, Andrew</p> <p></p> <p>To mitigate the degraded power system inertia and undesirable primary frequency response caused by large-scale <span class="hlt">wind</span> power integration, the frequency support capabilities of variable-<span class="hlt">speed</span> <span class="hlt">wind</span> turbines is studied in this work. This is made possible by controlled inertial response, which is demonstrated on a research turbine - controls advanced research turbine, 3-bladed (CART3). Two distinct inertial control (IC) methods are analysed in terms of their impacts on the grids and the response of the turbine itself. The released kinetic energy in the IC methods are determined by the frequency measurement or shaped active power reference in the turbine <span class="hlt">speed</span>-power plane.more » The <span class="hlt">wind</span> turbine model is based on the high-fidelity turbine simulator fatigue, aerodynamic, structures and turbulence, which constitutes the aggregated <span class="hlt">wind</span> power plant model with the simplified power converter model. The IC methods are implemented over the baseline CART3 controller, evaluated in the modified 9-bus and 14-bus testing power grids considering different <span class="hlt">wind</span> <span class="hlt">speeds</span> and different <span class="hlt">wind</span> power penetration levels. The simulation results provide various insights on designing such kinds of ICs. The authors calculate the short-term dynamic equivalent loads and give a discussion about the turbine structural loadings related to the inertial response.« less</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/871802','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/871802"><span>Variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generator with zero-sequence filter</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Muljadi, Eduard</p> <p>1998-01-01</p> <p>A variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator <span class="hlt">windings</span> of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator <span class="hlt">windings</span>. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/879425','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/879425"><span>Variable <span class="hlt">Speed</span> <span class="hlt">Wind</span> Turbine Generator with Zero-sequence Filter</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Muljadi, Eduard</p> <p>1998-08-25</p> <p>A variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator <span class="hlt">windings</span> of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator <span class="hlt">windings</span>. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/672660','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/biblio/672660"><span>Variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generator with zero-sequence filter</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Muljadi, E.</p> <p>1998-08-25</p> <p>A variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generator system to convert mechanical power into electrical power or energy and to recover the electrical power or energy in the form of three phase alternating current and return the power or energy to a utility or other load with single phase sinusoidal waveform at sixty (60) hertz and unity power factor includes an excitation controller for generating three phase commanded current, a generator, and a zero sequence filter. Each commanded current signal includes two components: a positive sequence variable frequency current signal to provide the balanced three phase excitation currents required in the stator <span class="hlt">windings</span> of the generator to generate the rotating magnetic field needed to recover an optimum level of real power from the generator; and a zero frequency sixty (60) hertz current signal to allow the real power generated by the generator to be supplied to the utility. The positive sequence current signals are balanced three phase signals and are prevented from entering the utility by the zero sequence filter. The zero sequence current signals have zero phase displacement from each other and are prevented from entering the generator by the star connected stator <span class="hlt">windings</span>. The zero sequence filter allows the zero sequence current signals to pass through to deliver power to the utility. 14 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15903865','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15903865"><span>Dynamics of <span class="hlt">zonal</span> flows in helical systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sugama, H; Watanabe, T-H</p> <p>2005-03-25</p> <p>A theory for describing collisionless long-time behavior of <span class="hlt">zonal</span> flows in helical systems is presented and its validity is verified by gyrokinetic-Vlasov simulation. It is shown that, under the influence of particles trapped in helical ripples, the response of <span class="hlt">zonal</span> flows to a given source becomes weaker for lower radial wave numbers and deeper helical ripples while a high-level <span class="hlt">zonal</span>-flow response, which is not affected by helical-ripple-trapped particles, can be maintained for a longer time by reducing their bounce-averaged radial drift velocity. This implies a possibility that helical configurations optimized for reducing neoclassical ripple transport can simultaneously enhance <span class="hlt">zonal</span> flows which lower anomalous transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=338029','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=338029"><span>Effect of windbreaks on <span class="hlt">wind</span> <span class="hlt">speed</span> and citrus canker incidence on grapefruit</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>For fresh grapefruit the goal is to maximize pack-out by minimizing canker lesions on fruit. The objective of these trials was to determine the relationship between <span class="hlt">wind</span> <span class="hlt">speed</span> and incidence and severity of citrus canker on 5 to 7 yr-old ‘Ruby Red’ grapefruit trees located in two trial blocks (~4.5 h...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110012864&hterms=wave+oscillation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dwave%2Boscillation','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110012864&hterms=wave+oscillation&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dwave%2Boscillation"><span>Evolution of the Equatorial Oscillation in Saturn's Stratosphere Between 2005 and 2010 from Cassini/CIRS Limb Data Analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Guerlet, S.; Fouchet, T.; Bezard, B.; Flasar, F. M.; Simon-Miller, A. A.</p> <p>2011-01-01</p> <p>We present an analysis of thermal infrared spectra acquired in limb viewing geometry by Cassini/CIRS in February 2010. We retrieve vertical profiles of Saturn's stratospheric temperature from 20 hPa to 10 (exp -2) hPa, at 9 latitudes between 20 deg N and 20 deg S. Using the gradient thermal <span class="hlt">wind</span> equation, we derive a map of the <span class="hlt">zonal</span> <span class="hlt">wind</span> field. Both the temperature and the <span class="hlt">zonal</span> <span class="hlt">wind</span> vertical profiles exhibit an oscillation in the equatorial region. These results are compared to the temperature and <span class="hlt">zonal</span> <span class="hlt">wind</span> maps obtained from 2005-2006 CIRS limb data, when this oscillation was first reported. In both epochs, strong temperature anomalies at the equator (up to 20K) are consistent with adiabatic heating (cooling) due to a sinking (rising) motion at a <span class="hlt">speed</span> of 0.1 - 0.2 mm/s. Finally, we show that the altitude of the maximum eastward <span class="hlt">wind</span> has moved downwards by 1.3 scale heights in 4.2 years, hence with a 'phase' <span class="hlt">speed</span> of approximately 0.5 mm/s. This rate is consistent with the estimated period of 14.7 years for the equatorial oscillation, and requires a local <span class="hlt">zonal</span> acceleration of 1.1 x 10(exp -6) m.s(exp -2) at the 2.5 hPa pressure level. This downward propagation of the oscillation is consistent with it being driven by absorption of upwardly propagating waves.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19850048413&hterms=scandinavia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dscandinavia','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19850048413&hterms=scandinavia&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dscandinavia"><span><span class="hlt">Wind</span> structure and variability in the middle atmosphere during the November 1980 energy budget campaign</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Schmidlin, F. J.; Carlson, M.; Rees, D.; Offermann, D.; Philbrick, C. R.; Widdel, H. U.</p> <p>1985-01-01</p> <p>Between November 6 and December 1, 1980 series of rocket observations were obtained from two sites in northern Scandinavia (68 deg N) as part of the Energy Budget Campaign, revealing the presence of significant vertical and temporal changes in the <span class="hlt">wind</span> structure. These changes coincided with different geomagnetic conditions, i.e. quiet and enhanced. Large amounts of rocket data were gathered from high latitudes over such a short interval of time. Prior to November 16 the meridional <span class="hlt">wind</span> component above 60 km was found to be positive (southerly), while the magnitude of the <span class="hlt">zonal</span> <span class="hlt">wind</span> component incresed with altitude. After November 16 the meridional component became negative (northerly) and the magnitude of the <span class="hlt">zonal</span> <span class="hlt">wind</span> component was noted to decrease with altitude. Time-sections of the perturbations of the <span class="hlt">zonal</span> <span class="hlt">wind</span> show the presence of vertically propagating waves, which suggest gravity wave activity. These waves increase in length from 1 km near 30 km to over 12 km near 80 km. The observational techniques employed Andoya (69 deg N), Norway, and Esrange (67.9 deg N), Sweden, consisted of chaff foil, instrumented rigid spheres, chemical trails, inflatable spheres and parachutes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/7200700-slotted-wall-research-disk-parachute-models-low-speed-wind-tunnel','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/7200700-slotted-wall-research-disk-parachute-models-low-speed-wind-tunnel"><span>Slotted-wall research with disk and parachute models in a low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Macha, J.M.; Buffington, R.J.; Henfling, J.L.</p> <p>1990-01-01</p> <p>An experimental investigation of slotted-wall blockage interference has been conducted using disk and parachute models in a low <span class="hlt">speed</span> <span class="hlt">wind</span> tunnel. Test section open area ratio, model geometric blockage ratio, and model location along the length of the test section were systematically varied. Resulting drag coefficients were compared to each other and to interference-free measurements obtained in a much larger <span class="hlt">wind</span> tunnel where the geometric blockage ratio was less than 0.0025. 9 refs., 10 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050169928&hterms=510&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D510','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050169928&hterms=510&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3D510"><span>Drive Motor Improved for 8- by 6-Foot Supersonic <span class="hlt">Wind</span> Tunnel/9- by 15-Foot Low-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel Complex</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>2005-01-01</p> <p>An operational change made recently in the drive motor system for the 8- by 6-Foot Supersonic <span class="hlt">Wind</span> Tunnel (8x6 SWT)/9- by 15-Foot Low-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel (9x15 LSWT) complex resulted in dramatic power savings and expanded operating range. The 8x6 SWT/9x15 LSWT complex offers a unique combination of <span class="hlt">wind</span> tunnel conditions for both high- and low-<span class="hlt">speed</span> testing. Prior to the work discussed in this article, the 8- by 6-ft test section offered airflows ranging from Mach 0.36 to 2.0. Subsonic testing was done in the 9-ft high, 15-ft wide test area in the return leg of the facility. The air <span class="hlt">speed</span> in this test section can range from 0 to 175 mph (Mach 0.23). In the past, we varied the air <span class="hlt">speed</span> by using a combination of the compressor <span class="hlt">speed</span> and the position of the tunnel flow-control doors. When very slow <span class="hlt">speeds</span> were required in the 9x15 LSWT, these large tunnel flow control doors might be very nearly full open, bleeding off large quantities of air, even with the drive system operating at its previous minimum <span class="hlt">speed</span> of about 510 rpm. Power drawn during this mode of operation varied between 15 and 18 MW/hr, but clearly much of this power was not being used to provide air that would be used for testing in the test section. The air exiting these large doors represented wasted power. Early this year, the facility's tunnel drive system was run on one motor instead of three to see if lower drive <span class="hlt">speeds</span> could be achieved that would, in turn, result in large power savings because unnecessary air would not be blown out of the flow-control doors unnecessarily. In addition, if the drive could be run slower, then slower <span class="hlt">speeds</span> would also be possible in the 8x6 SWT test section as an added benefit. Results of the first tests performed early last year showed that in fact the drive, when operating on only one motor, actually reached a steady-state <span class="hlt">speed</span> of only 337 rpm and drew an amazingly small 6 MW/hr of electrical power. During daytime operation of the drive, this meant that it would be</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018JSWSC...8A..18T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018JSWSC...8A..18T"><span>Coronal hole evolution from multi-viewpoint data as input for a STEREO solar <span class="hlt">wind</span> <span class="hlt">speed</span> persistence model</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Temmer, Manuela; Hinterreiter, Jürgen; Reiss, Martin A.</p> <p>2018-03-01</p> <p>We present a concept study of a solar <span class="hlt">wind</span> forecasting method for Earth, based on persistence modeling from STEREO in situ measurements combined with multi-viewpoint EUV observational data. By comparing the fractional areas of coronal holes (CHs) extracted from EUV data of STEREO and SoHO/SDO, we perform an uncertainty assessment derived from changes in the CHs and apply those changes to the predicted solar <span class="hlt">wind</span> <span class="hlt">speed</span> profile at 1 AU. We evaluate the method for the time period 2008-2012, and compare the results to a persistence model based on ACE in situ measurements and to the STEREO persistence model without implementing the information on CH evolution. Compared to an ACE based persistence model, the performance of the STEREO persistence model which takes into account the evolution of CHs, is able to increase the number of correctly predicted high-<span class="hlt">speed</span> streams by about 12%, and to decrease the number of missed streams by about 23%, and the number of false alarms by about 19%. However, the added information on CH evolution is not able to deliver more accurate <span class="hlt">speed</span> values for the forecast than using the STEREO persistence model without CH information which performs better than an ACE based persistence model. Investigating the CH evolution between STEREO and Earth view for varying separation angles over ˜25-140° East of Earth, we derive some relation between expanding CHs and increasing solar <span class="hlt">wind</span> <span class="hlt">speed</span>, but a less clear relation for decaying CHs and decreasing solar <span class="hlt">wind</span> <span class="hlt">speed</span>. This fact most likely prevents the method from making more precise forecasts. The obtained results support a future L5 mission and show the importance and valuable contribution using multi-viewpoint data.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020062990','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020062990"><span>Comparison of the 10x10 and the 8x6 Supersonic <span class="hlt">Wind</span> Tunnels at the NASA Glenn Research Center for Low-<span class="hlt">Speed</span> (Subsonic) Operation</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoffman, Thomas R.; Johns, Albert L.; Bury, Mark E.</p> <p>2002-01-01</p> <p>NASA Glenn Research Center and Lockheed Martin tested an aircraft model in two <span class="hlt">wind</span> tunnels to compare low-<span class="hlt">speed</span> (subsonic) flow characteristics. Test objectives were to determine and document similarities and uniqueness of the tunnels and to verify that the 10- by 10-Foot Supersonic <span class="hlt">Wind</span> Tunnel (10x10 SWT) is a viable low-<span class="hlt">speed</span> test facility when compared to the 8- by 6-Foot Supersonic <span class="hlt">Wind</span> Tunnel (8x6 SWT). Conclusions are that the data from the two facilities compares very favorably and that the 10-by 10-Foot Supersonic <span class="hlt">Wind</span> Tunnel at NASA Glenn Research Center is a viable low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1988STIN...8825972H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1988STIN...8825972H"><span>Analysis of the electrical harmonic characteristics of a slip recovery variable <span class="hlt">speed</span> generating system for <span class="hlt">wind</span> turbine applications</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Herrera, J. I.; Reddoch, T. W.</p> <p>1988-02-01</p> <p>Variable <span class="hlt">speed</span> electric generating technology can enhance the general use of <span class="hlt">wind</span> energy in electric utility applications. This enhancement results from two characteristic properties of variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire <span class="hlt">wind</span> turbine system, and an improvement in the overall efficiency by using a more sophisticated electrical generator. Electronic converter systems are the focus of this investigation -- in particular, the properties of a wound-rotor induction generator with the slip recovery system and direct-current link converter. Experience with solid-state converter systems in large <span class="hlt">wind</span> turbines is extremely limited. This report presents measurements of electrical performances of the slip recovery system and is limited to the terminal characteristics of the system. Variable <span class="hlt">speed</span> generating systems working effectively in utility applications will require a satisfactory interface between the turbine/generator pair and the utility network. The electrical testing described herein focuses largely on the interface characteristics of the generating system. A MOD-O <span class="hlt">wind</span> turbine was connected to a very strong system; thus, the voltage distortion was low and the total harmonic distortion in the utility voltage was less than 3 percent (within the 5 percent limit required by most utilities). The largest voltage component of a frequency below 60 Hz was 40 dB down from the 60-Hz less than component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.749a2004S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.749a2004S"><span>Preliminary assessment of the variability of UK offshore <span class="hlt">wind</span> <span class="hlt">speed</span> as a function of distance to the coast</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Soler-Bientz, Rolando; Watson, Simon</p> <p>2016-09-01</p> <p>In the UK, there is an interest in the expected offshore <span class="hlt">wind</span> resource given ambitious national plans to expand offshore capacity. There is also an increasing interest in alternative datasets to evaluate <span class="hlt">wind</span> seasonal and inter-annual cycles which can be very useful in the initial stages of the design of <span class="hlt">wind</span> farms in order to identify prospective areas where local measurements can then be applied to determine small-scale variations in the marine <span class="hlt">wind</span> climate. In this paper we analyse both MERRA2 reanalysis data and measured offshore mast data to determine patterns in <span class="hlt">wind</span> <span class="hlt">speed</span> variation and how they change as a function of the distance from the coast. We also identify an empirical expression to estimate <span class="hlt">wind</span> <span class="hlt">speed</span> based on the distance from the coast. From the analysis, it was found that the variations of the seasonal cycles seem to be almost independent of the distance to the nearest shore and that they are an order of magnitude larger than the variations of the diurnal cycles. It was concluded that the diurnal variations decreased to less than a half for places located more than 100km from the nearest shore and that the data from the MERRA2 reanalysis grid points give an under-prediction of the average values of <span class="hlt">wind</span> <span class="hlt">speed</span> for both the diurnal and seasonal cycles. Finally, even though the two offshore masts were almost the same nearest distance from the coast and were geographically relatively close, they exhibited significantly different behaviour in terms of the strength of their diurnal and seasonal cycles which may be due to the distance from the coast for the prevailing <span class="hlt">wind</span> direction being quite different for the two sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=246288','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=246288"><span>Evaluation of spray drift using low <span class="hlt">speed</span> <span class="hlt">wind</span> tunnel measurements and dispersion modeling</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The objective of this work was to evaluate the EPA’s proposed Test Plan for the validation testing of pesticide spray drift reduction technologies (DRTs) for row and field crops, focusing on the evaluation of ground application systems using the low-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel protocols and processing the dat...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011475','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011475"><span>Statistical Short-Range Guidance for Peak <span class="hlt">Wind</span> <span class="hlt">Speed</span> Forecasts at Edwards Air Force Base, CA</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dreher, Joseph G.; Crawford, Winifred; Lafosse, Richard; Hoeth, Brian; Burns, Kerry</p> <p>2009-01-01</p> <p>The peak <span class="hlt">winds</span> near the surface are an important forecast element for space shuttle landings. As defined in the Flight Rules (FR), there are peak <span class="hlt">wind</span> thresholds that cannot be exceeded in order to ensure the safety of the shuttle during landing operations. The National Weather Service Spaceflight Meteorology Group (SMG) is responsible for weather forecasts for all shuttle landings, and is required to issue surface average and 10-minute peak <span class="hlt">wind</span> <span class="hlt">speed</span> forecasts. They indicate peak <span class="hlt">winds</span> are a challenging parameter to forecast. To alleviate the difficulty in making such <span class="hlt">wind</span> forecasts, the Applied Meteorology Unit (AMU) developed a PC-based graphical user interface (GUI) for displaying peak <span class="hlt">wind</span> climatology and probabilities of exceeding peak <span class="hlt">wind</span> thresholds for the Shuttle Landing Facility (SLF) at Kennedy Space Center (KSC; Lambert 2003). However, the shuttle occasionally may land at Edwards Air Force Base (EAFB) in southern California when weather conditions at KSC in Florida are not acceptable, so SMG forecasters requested a similar tool be developed for EAFB.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6289088-solar-cycle-evolution-solar-wind-speed-structure-between-observed-interplanetary-scintillation-method','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6289088-solar-cycle-evolution-solar-wind-speed-structure-between-observed-interplanetary-scintillation-method"><span>Solar cycle evolution of solar <span class="hlt">wind</span> <span class="hlt">speed</span> structure between 1973 and 1985 observed with the interplanetary scintillation method</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Kojima, M.; Kakinuma, T.</p> <p>1987-07-01</p> <p>The solar cycle evolution of solar <span class="hlt">wind</span> <span class="hlt">speed</span> structure was studied for the years from 1973 to 1985 on a basis of interplanetary scintillation observations using a new method for mapping solar <span class="hlt">wind</span> <span class="hlt">speed</span> to the source surface. The major minimum-<span class="hlt">speed</span> regions are distributed along a neutral line through the whole period of a solar cycle: when solar activity is low, they are distributed on the wavy neutral line along the solar equator; in the active phase they also tend to be distributed along the neutral line, which has a large latitudinal amplitude. The minimum-<span class="hlt">speed</span> regions tend to be distributedmore » not only along the neutral line but also at low magnetic intensity regions and/or coronal bright regions which do not correspond to the neutral line. As the polar high-<span class="hlt">speed</span> regions extend equatorward around the minimum phase, the latitudinal gradient of <span class="hlt">speed</span> increases at the boundaries of the low-<span class="hlt">speed</span> region, and the width of the low-<span class="hlt">speed</span> region decreases. One or two years before the minimum of solar activity, two localized minimum-<span class="hlt">speed</span> regions appear on the neutral line, and their locations are longitudinally separated by 180. copyright American Geophysical Union 1987« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010NatGe...3..273S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010NatGe...3..273S"><span><span class="hlt">Zonally</span> asymmetric response of the Southern Ocean mixed-layer depth to the Southern Annular Mode</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sallée, J. B.; Speer, K. G.; Rintoul, S. R.</p> <p>2010-04-01</p> <p>Interactions between the atmosphere and ocean are mediated by the mixed layer at the ocean surface. The depth of this layer is determined by <span class="hlt">wind</span> forcing and heating from the atmosphere. Variations in mixed-layer depth affect the rate of exchange between the atmosphere and deeper ocean, the capacity of the ocean to store heat and carbon and the availability of light and nutrients to support the growth of phytoplankton. However, the response of the Southern Ocean mixed layer to changes in the atmosphere is not well known. Here we analyse temperature and salinity data from Argo profiling floats to show that the Southern Annular Mode (SAM), the dominant mode of atmospheric variability in the Southern Hemisphere, leads to large-scale anomalies in mixed-layer depth that are <span class="hlt">zonally</span> asymmetric. From a simple heat budget of the mixed layer we conclude that meridional <span class="hlt">winds</span> associated with departures of the SAM from <span class="hlt">zonal</span> symmetry cause anomalies in heat flux that can, in turn, explain the observed changes of mixed-layer depth and sea surface temperature. Our results suggest that changes in the SAM, including recent and projected trends attributed to human activity, drive variations in Southern Ocean mixed-layer depth, with consequences for air-sea exchange, ocean sequestration of heat and carbon, and biological productivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/420358','SCIGOV-STC'); return false;" href="https://www.osti.gov/servlets/purl/420358"><span>Analytical expressions for maximum <span class="hlt">wind</span> turbine average power in a Rayleigh <span class="hlt">wind</span> regime</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Carlin, P.W.</p> <p></p> <p>Average or expectation values for annual power of a <span class="hlt">wind</span> turbine in a Rayleigh <span class="hlt">wind</span> regime are calculated and plotted as a function of cut-out <span class="hlt">wind</span> <span class="hlt">speed</span>. This <span class="hlt">wind</span> <span class="hlt">speed</span> is expressed in multiples of the annual average <span class="hlt">wind</span> <span class="hlt">speed</span> at the turbine installation site. To provide a common basis for comparison of all real and imagined turbines, the Rayleigh-Betz <span class="hlt">wind</span> machine is postulated. This machine is an ideal <span class="hlt">wind</span> machine operating with the ideal Betz power coefficient of 0.593 in a Rayleigh probability <span class="hlt">wind</span> regime. All other average annual powers are expressed in fractions of that power. Cases consideredmore » include: (1) an ideal machine with finite power and finite cutout <span class="hlt">speed</span>, (2) real machines operating in variable <span class="hlt">speed</span> mode at their maximum power coefficient, and (3) real machines operating at constant <span class="hlt">speed</span>.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....10857P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....10857P"><span>Seasonal forecasting of high <span class="hlt">wind</span> <span class="hlt">speeds</span> over Western Europe</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palutikof, J. P.; Holt, T.</p> <p>2003-04-01</p> <p>As financial losses associated with extreme weather events escalate, there is interest from end users in the forestry and insurance industries, for example, in the development of seasonal forecasting models with a long lead time. This study uses exceedences of the 90th, 95th, and 99th percentiles of daily maximum <span class="hlt">wind</span> <span class="hlt">speed</span> over the period 1958 to present to derive predictands of winter <span class="hlt">wind</span> extremes. The source data is the 6-hourly NCEP Reanalysis gridded surface <span class="hlt">wind</span> field. Predictor variables include principal components of Atlantic sea surface temperature and several indices of climate variability, including the NAO and SOI. Lead times of up to a year are considered, in monthly increments. Three regression techniques are evaluated; multiple linear regression (MLR), principal component regression (PCR), and partial least squares regression (PLS). PCR and PLS proved considerably superior to MLR with much lower standard errors. PLS was chosen to formulate the predictive model since it offers more flexibility in experimental design and gave slightly better results than PCR. The results indicate that winter windiness can be predicted with considerable skill one year ahead for much of coastal Europe, but that this deteriorates rapidly in the hinterland. The experiment succeeded in highlighting PLS as a very useful method for developing more precise forecasting models, and in identifying areas of high predictability.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.fs.usda.gov/treesearch/pubs/42116','TREESEARCH'); return false;" href="https://www.fs.usda.gov/treesearch/pubs/42116"><span>How well can we measure the vertical <span class="hlt">wind</span> <span class="hlt">speed</span>? Implications for fluxes of energy and mass</span></a></p> <p><a target="_blank" href="http://www.fs.usda.gov/treesearch/">Treesearch</a></p> <p>John Kochendorfer; Tilden P. Meyers; John Frank; William J. Massman; Mark W. Heuer</p> <p>2012-01-01</p> <p>Sonic anemometers are capable of measuring the <span class="hlt">wind</span> <span class="hlt">speed</span> in all three dimensions at high frequencies (10­50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, <span class="hlt">wind</span>-velocity measurement errors from a three-dimensional sonic anemometer with a nonorthogonal transducer...</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFM.P11C0128F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFM.P11C0128F"><span>Low-latitude Temperatures, Pressures, and <span class="hlt">Winds</span> on Saturn from Cassini Radio Occultations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Flasar, F. M.; Schinder, P. J.; Kliore, A. J.; French, R. G.; Marouf, E. A.; Nagy, A.; Rappaport, N. J.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D. U.; Goltz, G. L.; Johnston, D. V.; Rochblatt, D.; McGhee, C. A.</p> <p>2005-12-01</p> <p>We present results from 12 ingress and egress soundings done within 10 degrees of Saturn's equator. Above the 100-mbar level, near the tropopause, the vertical profiles of temperature are marked by undulatory structure that may be associated with vertically propagating waves. Below the 200-mbar level, in the upper troposphere, the vertical profiles are smoother, and the overall trend of temperatures is to increase away from the equator. This implies a decay of the <span class="hlt">zonal</span> <span class="hlt">winds</span> with altitude. The <span class="hlt">zonal</span> <span class="hlt">winds</span> can actually be inferred directly from the meridional gradient in pressure, without the need of a boundary condition on the <span class="hlt">winds</span>. We summarize results of these calculations. This is of interest because recent cloud tracking studies have indicated lower equatorial <span class="hlt">winds</span> than found earlier, but whether this indicates a real change in the <span class="hlt">winds</span> at a given altitude or a change in the altitudes of the features tracked is controversial.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20140010287','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20140010287"><span><span class="hlt">Wind</span> Retrieval Algorithms for the IWRAP and HIWRAP Airborne Doppler Radars with Applications to Hurricanes</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Guimond, Stephen Richard; Tian, Lin; Heymsfield, Gerald M.; Frasier, Stephen J.</p> <p>2013-01-01</p> <p>Algorithms for the retrieval of atmospheric <span class="hlt">winds</span> in precipitating systems from downward-pointing, conically-scanning airborne Doppler radars are presented. The focus in the paper is on two radars: the Imaging <span class="hlt">Wind</span> and Rain Airborne Profiler(IWRAP) and the High-altitude IWRAP (HIWRAP). The IWRAP is a dual-frequency (Cand Ku band), multi-beam (incidence angles of 30 50) system that flies on the NOAAWP-3D aircraft at altitudes of 2-4 km. The HIWRAP is a dual-frequency (Ku and Kaband), dual-beam (incidence angles of 30 and 40) system that flies on the NASA Global Hawk aircraft at altitudes of 18-20 km. Retrievals of the three Cartesian <span class="hlt">wind</span> components over the entire radar sampling volume are described, which can be determined using either a traditional least squares or variational solution procedure. The random errors in the retrievals are evaluated using both an error propagation analysis and a numerical simulation of a hurricane. These analyses show that the vertical and along-track <span class="hlt">wind</span> errors have strong across-track dependence with values of 0.25 m s-1 at nadir to 2.0 m s-1 and 1.0 m s-1 at the swath edges, respectively. The across-track <span class="hlt">wind</span> errors also have across-track structure and are on average, 3.0 3.5 m s-1 or 10 of the hurricane <span class="hlt">wind</span> <span class="hlt">speed</span>. For typical rotated figure four flight patterns through hurricanes, the <span class="hlt">zonal</span> and meridional <span class="hlt">wind</span> <span class="hlt">speed</span> errors are 2 3 m s-1.Examples of measured data retrievals from IWRAP during an eyewall replacement cycle in Hurricane Isabel (2003) and from HIWRAP during the development of Tropical Storm Matthew (2010) are shown.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996AtmEn..30.4077P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996AtmEn..30.4077P"><span>Ozone gradients in a spruce forest stand in relation to <span class="hlt">wind</span> <span class="hlt">speed</span> and time of the day</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pleijel, H.; Wallin, G.; Karlsson, P. E.; Skärby, L.</p> <p></p> <p>Ozone concentrations were measured outside and inside a 60-year-old 15-20 m tall spruce forest at a <span class="hlt">wind</span>-exposed forest edge in southwest Sweden, at 3 and 13 m height 15 m outside the forest, and at 3 and 13 m height inside the forest 45 m from the forest edge. Measurements at 3 m were made with three replicate tubes on each site, the replicates being separated by 10 m. In addition, horizontal and vertical <span class="hlt">wind</span> <span class="hlt">speeds</span> were measured at 8 m height outside and inside the forest. During daytime, the concentrations inside the forest were generally slightly lower. Negative ozone concentration gradients from the open field into the forest were observed at 3 m height when the <span class="hlt">wind</span> <span class="hlt">speed</span> was below approximately 1.5 m s -1. At very low <span class="hlt">wind</span> <span class="hlt">speeds</span>, mainly occurring during the night, the ozone concentrations at 3 m height were frequently higher inside the forest than outside the forest. This may be caused by a very large aerodynamic resistance to ozone deposition, due to very small air movements inside the forest under stable conditions. It is concluded that ozone uptake by the trees is likely to be very small at night, even if stomata are not entirely closed. Results from open-top chamber experiments are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=115386&Lab=NRMRL&keyword=electronics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=115386&Lab=NRMRL&keyword=electronics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>FUZZY LOGIC BASED INTELLIGENT CONTROL OF A VARIABLE <span class="hlt">SPEED</span> CAGE MACHINE <span class="hlt">WIND</span> GENERATION SYSTEM</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The paper describes a variable-<span class="hlt">speed</span> <span class="hlt">wind</span> generation system where fuzzy logic principles are used to optimize efficiency and enhance performance control. A squirrel cage induction generator feeds the power to a double-sided pulse width modulated converter system which either pump...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950013378','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950013378"><span>Improved <span class="hlt">Speed</span> Control System for the 87,000 HP <span class="hlt">Wind</span> Tunnel Drive</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Becks, Edward A.; Bencic, Timothy J.; Blumenthal, Philip Z.</p> <p>1995-01-01</p> <p>This paper describes the design, installation, and integrated systems tests for a new drive motor <span class="hlt">speed</span> control system which was part of a recent rehab project for the NASA Lewis 8x6 Supersonic <span class="hlt">Wind</span> Tunnel. The tunnel drive consists of three mechanically-coupled 29,000 HP wound rotor induction motors driving an axial flow compressor. Liquid rheostats are used to vary the impedance of the rotor circuits, thus varying the <span class="hlt">speed</span> of the drive system. The new design utilizes a distributed digital control system with a dual touch screen CRT operator console to provide alarm monitoring, logging, and trending. The liquid rheostats are driven by brushtype servomotor systems with magnetostrictive linear displacement transducers used for position feedback. The new system achieved all goals for <span class="hlt">speed</span> variations with load, motor load balance, and control of total power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995inin.symp....7B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995inin.symp....7B"><span>Improved <span class="hlt">speed</span> control system for the 87,000 HP <span class="hlt">wind</span> tunnel drive</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Becks, Edward A.; Bencic, Timothy J.; Blumenthal, Philip Z.</p> <p>1995-01-01</p> <p>This paper describes the design, installation, and integrated systems tests for a new drive motor <span class="hlt">speed</span> control system which was part of a recent rehab project for the NASA Lewis 8x6 Supersonic <span class="hlt">Wind</span> Tunnel. The tunnel drive consists of three mechanically-coupled 29,000 HP wound rotor induction motors driving an axial flow compressor. Liquid rheostats are used to vary the impedance of the rotor circuits, thus varying the <span class="hlt">speed</span> of the drive system. The new design utilizes a distributed digital control system with a dual touch screen CRT operator console to provide alarm monitoring, logging, and trending. The liquid rheostats are driven by brushtype servomotor systems with magnetostrictive linear displacement transducers used for position feedback. The new system achieved all goals for <span class="hlt">speed</span> variations with load, motor load balance, and control of total power.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007RaSc...42.6008K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007RaSc...42.6008K"><span>Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 1. Comparison of <span class="hlt">wind</span> measurements with MF spaced antenna radar system</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kumar, Karanam Kishore; Ramkumar, Geetha; Shelbi, S. T.</p> <p>2007-12-01</p> <p>In the present communication, initial results from the allSKy interferometric METeor (SKiYMET) radar installed at Thumba (8.5°N, 77°E) are presented. The meteor radar system provides hourly <span class="hlt">zonal</span> and meridional <span class="hlt">winds</span> in the mesosphere lower thermosphere (MLT) region. The meteor radar measured <span class="hlt">zonal</span> and meridional <span class="hlt">winds</span> are compared with nearby MF radar at Tirunalveli (8.7°N, 77.8°E). The present study provided an opportunity to compare the <span class="hlt">winds</span> measured by the two different techniques, namely, interferometry and spaced antenna drift methods. Simultaneous <span class="hlt">wind</span> measurements for a total number of 273 days during September 2004 to May 2005 are compared. The comparison showed a very good agreement between these two techniques in the height region 82-90 km and poor agreement above this height region. In general, the <span class="hlt">zonal</span> <span class="hlt">winds</span> compare very well as compared to the meridional <span class="hlt">winds</span>. The observed discrepancies in the <span class="hlt">wind</span> comparison above 90 km are discussed in the light of existing limitations of both the radars. The detailed analysis revealed the consistency of the measured <span class="hlt">winds</span> by both the techniques. However, the discrepancies are observed at higher altitudes and are attributed to the contamination of MF radar neutral <span class="hlt">wind</span> measurements with Equatorial Electro Jet (EEJ) induced inospheric drifts rather than the limitations of the spaced antenna technique. The comparison of diurnal variation of <span class="hlt">zonal</span> <span class="hlt">winds</span> above 90 km measured by both the radars is in reasonably good agreement in the absence of EEJ (during local nighttime). It is also been noted that the difference in the <span class="hlt">zonal</span> <span class="hlt">wind</span> measurements by both the radars is directly related to the strength of EEJ, which is a noteworthy result from the present study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25309005','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25309005"><span>Study of the effect of <span class="hlt">wind</span> <span class="hlt">speed</span> on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa</p> <p>2014-01-01</p> <p>In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of <span class="hlt">wind</span> <span class="hlt">speed</span> on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a <span class="hlt">wind</span> tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the <span class="hlt">wind</span> <span class="hlt">speed</span> increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high <span class="hlt">wind</span> <span class="hlt">speeds</span> the evaporation rate becomes less dependent on the <span class="hlt">wind</span> <span class="hlt">speed</span>. On the contrary, the impact of <span class="hlt">wind</span> <span class="hlt">speed</span> on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4171757','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4171757"><span>Study of the effect of <span class="hlt">wind</span> <span class="hlt">speed</span> on evaporation from soil through integrated modeling of the atmospheric boundary layer and shallow subsurface</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Davarzani, Hossein; Smits, Kathleen; Tolene, Ryan M; Illangasekare, Tissa</p> <p>2014-01-01</p> <p>In an effort to develop methods based on integrating the subsurface to the atmospheric boundary layer to estimate evaporation, we developed a model based on the coupling of Navier-Stokes free flow and Darcy flow in porous medium. The model was tested using experimental data to study the effect of <span class="hlt">wind</span> <span class="hlt">speed</span> on evaporation. The model consists of the coupled equations of mass conservation for two-phase flow in porous medium with single-phase flow in the free-flow domain under nonisothermal, nonequilibrium phase change conditions. In this model, the evaporation rate and soil surface temperature and relative humidity at the interface come directly from the integrated model output. To experimentally validate numerical results, we developed a unique test system consisting of a <span class="hlt">wind</span> tunnel interfaced with a soil tank instrumented with a network of sensors to measure soil-water variables. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process with good accuracy. Increasing the <span class="hlt">wind</span> <span class="hlt">speed</span> increases the first stage evaporation rate and decreases the transition time between two evaporative stages (soil water flow to vapor diffusion controlled) at low velocity values; then, at high <span class="hlt">wind</span> <span class="hlt">speeds</span> the evaporation rate becomes less dependent on the <span class="hlt">wind</span> <span class="hlt">speed</span>. On the contrary, the impact of <span class="hlt">wind</span> <span class="hlt">speed</span> on second stage evaporation (diffusion-dominant stage) is not significant. We found that the thermal and solute dispersion in free-flow systems has a significant influence on drying processes from porous media and should be taken into account. PMID:25309005</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27812298','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27812298"><span>Mixture EMOS model for calibrating ensemble forecasts of <span class="hlt">wind</span> <span class="hlt">speed</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Baran, S; Lerch, S</p> <p>2016-03-01</p> <p>Ensemble model output statistics (EMOS) is a statistical tool for post-processing forecast ensembles of weather variables obtained from multiple runs of numerical weather prediction models in order to produce calibrated predictive probability density functions. The EMOS predictive probability density function is given by a parametric distribution with parameters depending on the ensemble forecasts. We propose an EMOS model for calibrating <span class="hlt">wind</span> <span class="hlt">speed</span> forecasts based on weighted mixtures of truncated normal (TN) and log-normal (LN) distributions where model parameters and component weights are estimated by optimizing the values of proper scoring rules over a rolling training period. The new model is tested on <span class="hlt">wind</span> <span class="hlt">speed</span> forecasts of the 50 member European Centre for Medium-range Weather Forecasts ensemble, the 11 member Aire Limitée Adaptation dynamique Développement International-Hungary Ensemble Prediction System ensemble of the Hungarian Meteorological Service, and the eight-member University of Washington mesoscale ensemble, and its predictive performance is compared with that of various benchmark EMOS models based on single parametric families and combinations thereof. The results indicate improved calibration of probabilistic and accuracy of point forecasts in comparison with the raw ensemble and climatological forecasts. The mixture EMOS model significantly outperforms the TN and LN EMOS methods; moreover, it provides better calibrated forecasts than the TN-LN combination model and offers an increased flexibility while avoiding covariate selection problems. © 2016 The Authors Environmetrics Published by JohnWiley & Sons Ltd.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018ClDy...50.4583P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018ClDy...50.4583P"><span>Time evolution of atmospheric parameters and their influence on sea level pressure over the head Bay of Bengal</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Patra, Anindita; Bhaskaran, Prasad K.; Jose, Felix</p> <p>2018-06-01</p> <p>A <span class="hlt">zonal</span> dipole in the observed trends of <span class="hlt">wind</span> <span class="hlt">speed</span> and significant wave height over the Head Bay of Bengal region was recently reported in the literature attributed due to the variations in sea level pressure (SLP). The SLP in turn is governed by prevailing atmospheric conditions such as local temperature, humidity, rainfall, atmospheric pressure, <span class="hlt">wind</span> field distribution, formation of tropical cyclones, etc. The present study attempts to investigate the inter-annual variability of atmospheric parameters and its role on the observed <span class="hlt">zonal</span> dipole trend in sea level pressure, surface <span class="hlt">wind</span> <span class="hlt">speed</span> and significant wave height. It reports on the aspects related to linear trend as well as its spatial variability for several atmospheric parameters: air temperature, geopotential height, omega (vertical velocity), and <span class="hlt">zonal</span> <span class="hlt">wind</span>, over the head Bay of Bengal, by analyzing National Centers for Environmental Prediction (NCEP) Reanalysis 2 dataset covering a period of 38 years (1979-2016). Significant warming from sea level to 200 mb pressure level and thereafter cooling above has been noticed during all the seasons. Warming within the troposphere exhibits spatial difference between eastern and western side of the domain. This led to fall in lower tropospheric geopotential height and its east-west variability, exhibiting a <span class="hlt">zonal</span> dipole pattern across the Head Bay. In the upper troposphere, uplift in geopotential height was found as a result of cooling in higher levels (10-100 mb). Variability in omega also substantiated the observed variations in geopotential height. The study also finds weakening in the upper level westerlies and easterlies. Interestingly, a linear trend in lower tropospheric u-<span class="hlt">wind</span> component also reveals an east-west dipole pattern over the study region. Further, the study corroborates the reported dipole in trends of sea level pressure, <span class="hlt">wind</span> <span class="hlt">speed</span> and significant wave height by evaluating the influence of atmospheric variability on these parameters.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/5059860-analysis-electrical-harmonic-characteristics-slip-recovery-variable-speed-generating-system-wind-turbine-applications','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/5059860-analysis-electrical-harmonic-characteristics-slip-recovery-variable-speed-generating-system-wind-turbine-applications"><span>Analysis of the electrical harmonic characteristics of a slip recovery variable <span class="hlt">speed</span> generating system for <span class="hlt">wind</span> turbine applications</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Herrera, J.I.; Reddoch, T.W.</p> <p>1988-02-01</p> <p>Variable <span class="hlt">speed</span> electric generating technology can enhance the general use of <span class="hlt">wind</span> energy in electric utility applications. This enhancement results from two characteristic properties of variable <span class="hlt">speed</span> <span class="hlt">wind</span> turbine generators: an improvement in drive train damping characteristics, which results in reduced structural loading on the entire <span class="hlt">wind</span> turbine system, and an improvement in the overall efficiency by using a more sophisticated electrical generator. Electronic converter systems are the focus of this investigation -- in particular, the properties of a wound-rotor induction generator with the slip recovery system and direct-current link converter. Experience with solid-state converter systems in large <span class="hlt">wind</span> turbinesmore » is extremely limited. This report presents measurements of electrical performances of the slip recovery system and is limited to the terminal characteristics of the system. Variable <span class="hlt">speed</span> generating systems working effectively in utility applications will require a satisfactory interface between the turbine/generator pair and the utility network. The electrical testing described herein focuses largely on the interface characteristics of the generating system. A MOD-O <span class="hlt">wind</span> turbine was connected to a very strong system; thus, the voltage distortion was low and the total harmonic distortion in the utility voltage was less than 3% (within the 5% limit required by most utilities). The largest voltage component of a frequency below 60 Hz was 40 dB down from the 60-Hz< component. 8 refs., 14 figs., 8 tabs.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ACP....17.9019B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ACP....17.9019B"><span>Estimation of bubble-mediated air-sea gas exchange from concurrent DMS and CO2 transfer velocities at intermediate-high <span class="hlt">wind</span> <span class="hlt">speeds</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bell, Thomas G.; Landwehr, Sebastian; Miller, Scott D.; de Bruyn, Warren J.; Callaghan, Adrian H.; Scanlon, Brian; Ward, Brian; Yang, Mingxi; Saltzman, Eric S.</p> <p>2017-07-01</p> <p>Simultaneous air-sea fluxes and concentration differences of dimethylsulfide (DMS) and carbon dioxide (CO2) were measured during a summertime North Atlantic cruise in 2011. This data set reveals significant differences between the gas transfer velocities of these two gases (Δkw) over a range of <span class="hlt">wind</span> <span class="hlt">speeds</span> up to 21 m s-1. These differences occur at and above the approximate <span class="hlt">wind</span> <span class="hlt">speed</span> threshold when waves begin breaking. Whitecap fraction (a proxy for bubbles) was also measured and has a positive relationship with Δkw, consistent with enhanced bubble-mediated transfer of the less soluble CO2 relative to that of the more soluble DMS. However, the correlation of Δkw with whitecap fraction is no stronger than with <span class="hlt">wind</span> <span class="hlt">speed</span>. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate <span class="hlt">wind</span> <span class="hlt">speeds</span>. Examining the differences between gas transfer velocities of gases with different solubilities is a useful way to detect the impact of bubble-mediated exchange. More simultaneous gas transfer measurements of different solubility gases across a wide range of oceanic conditions are needed to understand the factors controlling the magnitude and scaling of bubble-mediated gas exchange.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014GBioC..28..909R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014GBioC..28..909R"><span>Sensitivity of ocean oxygenation to variations in tropical <span class="hlt">zonal</span> <span class="hlt">wind</span> stress magnitude</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ridder, Nina N.; England, Matthew H.</p> <p>2014-09-01</p> <p>Ocean oxygenation has been observed to have changed over the past few decades and is projected to change further under global climate change due to an interplay of several mechanisms. In this study we isolate the effect of modified tropical surface <span class="hlt">wind</span> stress conditions on the evolution of ocean oxygenation in a numerical climate model. We find that ocean oxygenation varies inversely with low-latitude surface <span class="hlt">wind</span> stress. Approximately one third of this response is driven by sea surface temperature anomalies; the remaining two thirds result from changes in ocean circulation and marine biology. Global mean O2 concentration changes reach maximum values of +4 μM and -3.6 μM in the two most extreme perturbation cases of -30% and +30% <span class="hlt">wind</span> change, respectively. Localized changes lie between +92 μM under 30% reduced <span class="hlt">winds</span> and -56 μM for 30% increased <span class="hlt">winds</span>. Overall, we find that the extent of the global low-oxygen volume varies with the same sign as the <span class="hlt">wind</span> perturbation; namely, weaker <span class="hlt">winds</span> reduce the low-oxygen volume on the global scale and vice versa for increased trade <span class="hlt">winds</span>. We identify two regions, one in the Pacific Ocean off Chile and the other in the Indian Ocean off Somalia, that are of particular importance for the evolution of oxygen minimum zones in the global ocean.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A13G0317P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A13G0317P"><span>Evaluation of NOAA's High Resolution Rapid Refresh (HRRR), 12 km North America Model (NAM12) and 4km North America Model (NAM 4) hub-height <span class="hlt">wind</span> <span class="hlt">speed</span> forecasts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pendergrass, W.; Vogel, C. A.</p> <p>2013-12-01</p> <p>As an outcome of discussions between Duke Energy Generation and NOAA/ARL following the 2009 AMS Summer Community Meeting, in Norman Oklahoma, ARL and Duke Energy Generation (Duke) signed a Cooperative Research and Development Agreement (CRADA) which allows NOAA to conduct atmospheric boundary layer (ABL) research using Duke renewable energy sites as research testbeds. One aspect of this research has been the evaluation of forecast hub-height <span class="hlt">winds</span> from three NOAA atmospheric models. Forecasts of 10m (surface) and 80m (hub-height) <span class="hlt">wind</span> <span class="hlt">speeds</span> from (1) NOAA/GSD's High Resolution Rapid Refresh (HRRR) model, (2) NOAA/NCEP's 12 km North America Model (NAM12) and (3) NOAA/NCEP's 4k high resolution North America Model (NAM4) were evaluated against 18 months of surface-layer <span class="hlt">wind</span> observations collected at the joint NOAA/Duke Energy research station located at Duke Energy's West Texas Ocotillo <span class="hlt">wind</span> farm over the period April 2011 through October 2012. HRRR, NAM12 and NAM4 10m <span class="hlt">wind</span> <span class="hlt">speed</span> forecasts were compared with 10m level <span class="hlt">wind</span> <span class="hlt">speed</span> observations measured on the NOAA/ATDD flux-tower. Hub-height (80m) HRRR , NAM12 and NAM4 forecast <span class="hlt">wind</span> <span class="hlt">speeds</span> were evaluated against the 80m operational PMM27-28 meteorological tower supporting the Ocotillo <span class="hlt">wind</span> farm. For each HRRR update, eight forecast hours (hour 01, 02, 03, 05, 07, 10, 12, 15) plus the initialization hour (hour 00), evaluated. For the NAM12 and NAM4 models forecast hours 00-24 from the 06z initialization were evaluated. Performance measures or skill score based on absolute error 50% cumulative probability were calculated for each forecast hour. HRRR forecast hour 01 provided the best skill score with an absolute <span class="hlt">wind</span> <span class="hlt">speed</span> error within 0.8 m/s of observed 10m <span class="hlt">wind</span> <span class="hlt">speed</span> and 1.25 m/s for hub-height <span class="hlt">wind</span> <span class="hlt">speed</span> at the designated 50% cumulative probability. For both NAM4 and NAM12 models, skill scores were diurnal with comparable best scores observed during the day of 0.7 m/s of observed 10m <span class="hlt">wind</span> <span class="hlt">speed</span> and 1.1 m/s for hub</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.A51A2008K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.A51A2008K"><span>Comparison of <span class="hlt">Wind</span> <span class="hlt">Speeds</span> and Temperatures Simulated by the Local Data Assimilation and Prediction System with Those observed at AWSs in Korea</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>KIM, D. J.; Kim, J.</p> <p>2017-12-01</p> <p>In this study, the characteristics of 10-m <span class="hlt">wind</span> <span class="hlt">speeds</span> and 2-m temperatures predicted by the local data assimilation and prediction system (LDAPS) in Korea meteorological administration (KMA) were analyzed by comparing those observed at automatic weather stations (AWSs). The LDAPS is a currently operating meteorology prediction system with the horizontal resolution of about 1.5 km. We classified the AWSs into four categories (urban, rural, coastal, and mountainous areas) based on the surrounding land-use types and locations of the AWSs and selected 30 AWSs for each category. For each category, we investigated how well the LDAPS predicted 10-m <span class="hlt">wind</span> <span class="hlt">speeds</span> and 2-m temperatures at the AWSs and statistically analyzed the LDAPS characteristics in predicting the meteorological variables. In the mountainous area, the LDAPS underestimated 2-m temperatures due to the resolution and coordinate system of the LDAPS. In the urban area, the LDAPS overestimated the 10-m <span class="hlt">wind</span> <span class="hlt">speeds</span> and underestimated the 2-m temperatures, implying that the LDAPS should consider the physical process to reflect the urban effects on <span class="hlt">wind</span> <span class="hlt">speeds</span> and temperatures in urban areas.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840019220','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840019220"><span>Microwave Remote Sensing of Ocean Surface <span class="hlt">Wind</span> <span class="hlt">Speed</span> and Rain Rates over Tropical Storms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Swift, C. T.; Dehority, D. C.; Black, P. G.; Chien, J. Z.</p> <p>1984-01-01</p> <p>The value of using narrowly spaced frequencies within a microwave band to measure <span class="hlt">wind</span> <span class="hlt">speeds</span> and rain rates over tropical storms with radiometers is reviewed. The technique focuses on results obtained in the overflights of Hurricane Allen during 5 and 8 of August, 1980.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=115123&Lab=NRMRL&keyword=intelligence&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="https://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=115123&Lab=NRMRL&keyword=intelligence&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>FUZZY LOGIC BASED INTELLIGENT CONTROL OF A VARIABLE <span class="hlt">SPEED</span> CAGE MACHINE <span class="hlt">WIND</span> GENERATION SYSTEM</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>The report gives results of a demonstration of the successful application of fuzzy logic to enhance the performance and control of a variable-<span class="hlt">speed</span> <span class="hlt">wind</span> generation system. A squirrel cage induction generator feeds the power to either a double-sided pulse-width modulation converte...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRA..122.2795P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRA..122.2795P"><span>The most intense current sheets in the high-<span class="hlt">speed</span> solar <span class="hlt">wind</span> near 1 AU</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Podesta, John J.</p> <p>2017-03-01</p> <p>Electric currents in the solar <span class="hlt">wind</span> plasma are investigated using 92 ms fluxgate magnetometer data acquired in a high-<span class="hlt">speed</span> stream near 1 AU. The minimum resolvable scale is roughly 0.18 s in the spacecraft frame or, using Taylor's "frozen turbulence" approximation, one proton inertial length di in the plasma frame. A new way of identifying current sheets is developed that utilizes a proxy for the current density J obtained from the derivatives of the three orthogonal components of the observed magnetic field B. The most intense currents are identified as 5σ events, where σ is the standard deviation of the current density. The observed 5σ events are characterized by an average scale size of approximately 3di along the flow direction of the solar <span class="hlt">wind</span>, a median separation of around 50di or 100di along the flow direction of the solar <span class="hlt">wind</span>, and a peak current density on the order of 0.5 pA/cm2. The associated current-carrying structures are consistent with current sheets; however, the planar geometry of these structures cannot be confirmed using single-point, single-spacecraft measurements. If Taylor's hypothesis continues to hold for the energetically dominant fluctuations at kinetic scales 1<kdi≲40, then the results suggest that the most intense current-carrying structures in high-<span class="hlt">speed</span> <span class="hlt">wind</span> occur at electron scales, although the peak current densities at kinetic and electron scales are predicted to be nearly the same as those found in this study.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AGUFM.P13C2569A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AGUFM.P13C2569A"><span>Planetary <span class="hlt">Wind</span> Determination by Doppler Tracking of a Small Entry Probe Network</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Atkinson, D. H.; Asmar, S.; Lazio, J.; Preston, R. A.</p> <p>2017-12-01</p> <p>To understand the origin and chemical/dynamical evolution of planetary atmospheres, measurements of atmospheric chemistries and processes including dynamics are needed. In situ measurements of planetary <span class="hlt">winds</span> have been demonstrated on multiple occasions, including the Pioneer multiprobe and Venera missions to Venus, and the Galileo/Jupiter and Huygens/Titan probes. However, with the exception of Pioneer Venus, the retrieval of the <span class="hlt">zonal</span> (east-west) <span class="hlt">wind</span> profile has been limited to a single atmospheric slice. significantly improved understanding of the global dynamics requires sampling of multiple latitudes, times of day, and seasons. Simultaneous tracking of a small network of probes would enable measurements of spatially distributed <span class="hlt">winds</span> providing a substantially improved characterization of a planet's global atmospheric circulation. Careful selection of descent locations would provide <span class="hlt">wind</span> measurements at latitudes receiving different solar insolations, longitudes reflecting different times of day, and different seasons if both hemispheres are targeted. Doppler <span class="hlt">wind</span> retrievals are limited by the stability of the probe and carrier spacecraft clocks, and must be equipped with an ultrastable oscillator, accelerometers for reconstructing the probe entry trajectory, and pressure / temperature sensors for determination of descent <span class="hlt">speed</span>. A probe were equipped with both absolute and dynamic pressure sensors can measure planet center-relative and atmosphere-relative descent <span class="hlt">speeds</span>, enabling the measurement of vertical <span class="hlt">winds</span> from convection or atmospheric waves. Possible ambiguities arising from the assumption of no north-south <span class="hlt">winds</span> could be removed if the probe were simultaneously tracked from the carrier spacecraft as well as from the Earth or a second spacecraft. The global circulation of an atmosphere comprising waves and flows that vary with location and depth is inherently tied to the thermal, chemical, and energy structure of the atmosphere. <span class="hlt">Wind</span> measurements</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=334054','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=334054"><span>Effect of windbreaks on <span class="hlt">wind</span> <span class="hlt">speed</span> and canker incidence and severity on grapefruit</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>For fresh grapefruit the goal is to maximize pack-out by minimizing canker lesions on fruit. The objective of these trials was to determine the relationship between <span class="hlt">wind</span> <span class="hlt">speed</span> and incidence and severity of canker on 5 to 7 yr-old Ruby Red grapefruit trees located in two trial blocks (~4.5 ha) surrou...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JPhCS.753c2061S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JPhCS.753c2061S"><span><span class="hlt">Wind</span>-tunnel modelling of the tip-<span class="hlt">speed</span> ratio influence on the wake evolution</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Stein, Victor P.; Kaltenbach, Hans-Jakob</p> <p>2016-09-01</p> <p><span class="hlt">Wind</span>-tunnel measurements on the near-wake evolution of a three bladed horizontal axis <span class="hlt">wind</span> turbine model (HAWT) in the scale 1:O(350) operating in uniform flow conditions and within a turbulent boundary layer at different tip <span class="hlt">speed</span> ratios are presented. Operational conditions are chosen to exclude Reynolds number effects regarding the turbulent boundary layer as well as the rotor performance. Triple-wire anemometry is used to measure all three velocity components in the mid-vertical and mid-horizontal plane, covering the range from the near- to the far-wake region. In order to analyse wake properties systematically, power and thrust coefficients of the turbine were measured additionally. It is confirmed that realistic modelling of the wake evolution is not possible in a low-turbulence uniform approach flow. Profiles of mean velocity and turbulence intensity exhibit large deviations between the low-turbulence uniform flow and the turbulent boundary layer, especially in the far-wake region. For nearly constant thrust coefficients differences in the evolution of the near-wake can be identified for tip <span class="hlt">speed</span> ratios in the range from 6.5 to 10.5. It is shown that with increasing downstream distances mean velocity profiles become indistinguishable whereas for turbulence statistics a subtle dependency on the tip <span class="hlt">speed</span> ratio is still noticeable in the far-wake region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930091809','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930091809"><span>An Investigation of the Drag of Windshields in the 8-foot High-<span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Robinson, Russell G; Delano, James B</p> <p>1942-01-01</p> <p>Report presents the results of tests made to determine the drag of closed-cockpit and transport-type windshields. The tests were made at <span class="hlt">speeds</span> corresponding to a Mach number range of approximately 0.25 to 0.58 in the NACA 8-foot high-<span class="hlt">speed</span> <span class="hlt">wind</span> tunnel. This <span class="hlt">speed</span> range corresponds to a test Reynolds number range of 2,510,000 to 4,830,000 based on the mean aerodynamic chord of the full-span model (17.29 in.). The shapes of the windshield proper, the hood, and the tail fairing were systematically varied to include common types and refined design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770037908&hterms=Wave+filter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DWave%2Bfilter','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770037908&hterms=Wave+filter&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DWave%2Bfilter"><span>Short pulse radar used to measure sea surface <span class="hlt">wind</span> <span class="hlt">speed</span> and SWH. [Significant Wave Height</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hammond, D. L.; Mennella, R. A.; Walsh, E. J.</p> <p>1977-01-01</p> <p>A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which <span class="hlt">wind</span> <span class="hlt">speed</span> and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface <span class="hlt">wind</span> <span class="hlt">speed</span>. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20366891','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20366891"><span>Difference in the <span class="hlt">wind</span> <span class="hlt">speeds</span> required for initiation versus continuation of sand transport on mars: implications for dunes and dust storms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kok, Jasper F</p> <p>2010-02-19</p> <p>Much of the surface of Mars is covered by dunes, ripples, and other features formed by the blowing of sand by <span class="hlt">wind</span>, known as saltation. In addition, saltation loads the atmosphere with dust aerosols, which dominate the Martian climate. We show here that saltation can be maintained on Mars by <span class="hlt">wind</span> <span class="hlt">speeds</span> an order of magnitude less than required to initiate it. We further show that this hysteresis effect causes saltation to occur for much lower <span class="hlt">wind</span> <span class="hlt">speeds</span> than previously thought. These findings have important implications for the formation of dust storms, sand dunes, and ripples on Mars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJC....88..193P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJC....88..193P"><span>? stability of <span class="hlt">wind</span> turbine switching control</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Palejiya, Dushyant; Shaltout, Mohamed; Yan, Zeyu; Chen, Dongmei</p> <p>2015-01-01</p> <p>In order to maximise the <span class="hlt">wind</span> energy capture, <span class="hlt">wind</span> turbines are operated at variable <span class="hlt">speeds</span>. Depending on the <span class="hlt">wind</span> <span class="hlt">speed</span>, a turbine switches between two operating modes: a low <span class="hlt">wind</span> <span class="hlt">speed</span> mode and a high <span class="hlt">wind</span> <span class="hlt">speed</span> mode. During the low <span class="hlt">wind</span> <span class="hlt">speed</span> mode, the control objective is to maximise <span class="hlt">wind</span> energy capture by controlling both the blade pitch angle and the electrical generator torque. During the high <span class="hlt">wind</span> <span class="hlt">speed</span> mode, the control goal is to maintain the rated power generation by only adjusting the blade pitch angle. This paper establishes the stability criteria for the switching operation of <span class="hlt">wind</span> turbines using ? gain under the nonlinear control framework. Also, the performance of the <span class="hlt">wind</span> turbine system is analysed by using the step response, a well-known measure for second-order linear systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUFMOS31A1997S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUFMOS31A1997S"><span>Comparison of Sea-Air CO2 Flux Estimates Using Satellite-Based Versus Mooring <span class="hlt">Wind</span> <span class="hlt">Speed</span> Data</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sutton, A. J.; Sabine, C. L.; Feely, R. A.; Wanninkhof, R. H.</p> <p>2016-12-01</p> <p>The global ocean is a major sink of anthropogenic CO2, absorbing approximately 27% of CO2 emissions since the beginning of the industrial revolution. Any variation or change in the ocean CO2 sink has implications for future climate. Observations of sea-air CO2 flux have relied primarily on ship-based underway measurements of partial pressure of CO2 (pCO2) combined with satellite, model, or multi-platform <span class="hlt">wind</span> products. Direct measurements of ΔpCO2 (seawater - air pCO2) and <span class="hlt">wind</span> <span class="hlt">speed</span> from moored platforms now allow for high-resolution CO2 flux time series. Here we present a comparison of CO2 flux calculated from moored ΔpCO2 measured on four moorings in different biomes of the Pacific Ocean in combination with: 1) Cross-Calibrated Multi-Platform (CCMP) <span class="hlt">winds</span> or 2) <span class="hlt">wind</span> <span class="hlt">speed</span> measurements made on ocean reference moorings excluded from the CCMP dataset. Preliminary results show using CCMP <span class="hlt">winds</span> overestimates CO2 flux on average by 5% at the Kuroshio Extension Observatory, Ocean Station Papa, WHOI Hawaii Ocean Timeseries Station, and Stratus. In general, CO2 flux seasonality follows patterns of seawater pCO2 and SST with periods of CO2 outgassing during summer and CO2 uptake during winter at these locations. Any offsets or seasonal biases in CCMP <span class="hlt">winds</span> could impact global ocean sink estimates using this data product. Here we present patterns and trends between the two CO2 flux estimates and discuss the potential implications for tracking variability and change in global ocean CO2 uptake.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/EJ1084632.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/EJ1084632.pdf"><span>Conceptions of Tornado <span class="hlt">Wind</span> <span class="hlt">Speed</span> and Land Surface Interactions among Undergraduate Students in Nebraska</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Van Den Broeke, Matthew S.; Arthurs, Leilani</p> <p>2015-01-01</p> <p>To ascertain novice conceptions of tornado <span class="hlt">wind</span> <span class="hlt">speed</span> and the influence of surface characteristics on tornado occurrence, 613 undergraduate students enrolled in introductory science courses at a large state university in Nebraska were surveyed. Our findings show that students lack understanding of the fundamental concepts that (1) tornadoes are…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25950016','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25950016"><span>Simulation and study of power quality issues in a fixed <span class="hlt">speed</span> <span class="hlt">wind</span> farm substation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Magesh, T; Chellamuthu, C</p> <p>2015-01-01</p> <p>Power quality issues associated with the fixed <span class="hlt">speed</span> <span class="hlt">wind</span> farm substation located at Coimbatore district are investigated as the <span class="hlt">wind</span> generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for <span class="hlt">wind</span>, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled <span class="hlt">wind</span> turbine. Various scenarios and their effects on the performance of the <span class="hlt">wind</span> farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the <span class="hlt">wind</span> farm before implementation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4407622','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4407622"><span>Simulation and Study of Power Quality Issues in a Fixed <span class="hlt">Speed</span> <span class="hlt">Wind</span> Farm Substation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Magesh, T.; Chellamuthu, C.</p> <p>2015-01-01</p> <p>Power quality issues associated with the fixed <span class="hlt">speed</span> <span class="hlt">wind</span> farm substation located at Coimbatore district are investigated as the <span class="hlt">wind</span> generators are tripping frequently. The investigations are carried out using two power quality analyzers, Fluke 435 and Dranetz PX5.8, with one of them connected at group control breaker of the 110 kV feeder and the other at the selected 0.69 kV generator busbar during the period of maximum power generation. From the analysis of the recorded data it is found that sag, swell, and transients are the major events which are responsible for the tripping of the generators. In the present study, simulation models for <span class="hlt">wind</span>, turbine, shaft, pitch mechanism, induction generator, and grid are developed using DIgSILENT. Using the turbine characteristics, a two-dimensional lookup table is designed to generate a reference pitch angle necessary to simulate the power curve of the passive stall controlled <span class="hlt">wind</span> turbine. Various scenarios and their effects on the performance of the <span class="hlt">wind</span> farm are studied and validated with the recorded data and waveforms. The simulation model will be useful for the designers for planning and development of the <span class="hlt">wind</span> farm before implementation. PMID:25950016</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19930015971','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19930015971"><span>Empirical <span class="hlt">wind</span> model for the middle and lower atmosphere. Part 1: Local time average</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hedin, A. E.; Fleming, E. L.; Manson, A. H.; Schmidlin, F. J.; Avery, S. K.; Franke, S. J.</p> <p>1993-01-01</p> <p>The HWM90 thermospheric <span class="hlt">wind</span> model was revised in the lower thermosphere and extended into the mesosphere and lower atmosphere to provide a single analytic model for calculating <span class="hlt">zonal</span> and meridional <span class="hlt">wind</span> profiles representative of the climatological average for various geophysical conditions. Gradient <span class="hlt">winds</span> from CIRA-86 plus rocket soundings, incoherent scatter radar, MF radar, and meteor radar provide the data base and are supplemented by previous data driven model summaries. Low-order spherical harmonics and Fourier series are used to describe the major variations throughout the atmosphere including latitude, annual, semiannual, and longitude (stationary wave 1). The model represents a smoothed compromise between the data sources. Although agreement between various data sources is generally good, some systematic differences are noted, particularly near the mesopause. Root mean square differences between data and model are on the order of 15 m/s in the mesosphere and 10 m/s in the stratosphere for <span class="hlt">zonal</span> <span class="hlt">wind</span>, and 10 m/s and 4 m/s, respectively, for meridional <span class="hlt">wind</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017OptEn..56d4104P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017OptEn..56d4104P"><span>Fast tracking of <span class="hlt">wind</span> <span class="hlt">speed</span> with a differential absorption LiDAR system: first results of an experimental campaign at Stromboli volcano</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parracino, Stefano; Santoro, Simone; Maio, Giovanni; Nuvoli, Marcello; Aiuppa, Alessandro; Fiorani, Luca</p> <p>2017-04-01</p> <p>Carbon dioxide (CO2) is considered a precursor gas of volcanic eruptions by volcanologists. Monitoring the anomalous release of this parameter, we can retrieve useful information for the mitigation of volcanic hazards, such as for air traffic security. From a dataset collected during the Stromboli volcano field campaign, an assessment of the <span class="hlt">wind</span> <span class="hlt">speed</span>, in both horizontal and vertical paths, performing a fast tracking of this parameter was retrieved. This was determined with a newly designed shot-per-shot differential absorption LiDAR system operated in the near-infrared spectral region due to the simultaneous reconstruction of CO2 concentrations and <span class="hlt">wind</span> <span class="hlt">speeds</span>, using the same sample of LiDAR returns. A correlation method was used for the <span class="hlt">wind</span> <span class="hlt">speed</span> retrieval in which the transport of the spatial inhomogeneities of the aerosol backscattering coefficient, along the optical path of the system, was analyzed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1327219-characterization-high-speed-stage-bearing-skidding-wind-turbine-gearboxes-induced-dynamic-electricity-grid-events','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1327219-characterization-high-speed-stage-bearing-skidding-wind-turbine-gearboxes-induced-dynamic-electricity-grid-events"><span>Characterization of the High-<span class="hlt">Speed</span>-Stage Bearing Skidding of <span class="hlt">Wind</span> Turbine Gearboxes Induced by Dynamic Electricity Grid Events</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Helsen, Jan; Guillaume, Patrick; Guo, Yi</p> <p></p> <p>Bearing behavior is an important factor for <span class="hlt">wind</span> turbine drivetrain reliability. Extreme loads and dynamic excitations pose challenges to the bearing design and therefore its performance. Excessive skidding of the bearing rollers should be avoided because it can cause scuffing failures. Excitations coming from <span class="hlt">wind</span> and the electricity grid can subject the drivetrain to fluctuating torque and nontorque loads. <span class="hlt">Wind</span>-induced excitations have been investigated predominantly in literature. However, modern <span class="hlt">wind</span> turbines are subjected more and more to grid-induced loads because of stricter electricity grid regulations. For example, during fault-ride-through events, turbines are required to stay connected for a longer periodmore » of time during the grid failure. This work investigates the influence of electrically induced excitations on the skidding behaviour of the tapered roller bearings on the high-<span class="hlt">speed</span> stage of a <span class="hlt">wind</span> turbine gearbox. This skidding behaviour during dynamic events is described as a potential bearing failure initiator by many researchers; however, only limited full-scale dynamic testing is documented. Therefore, a dedicated gridloss-type event is defined in the paper and conducted in a dynamometer test on a full-scale <span class="hlt">wind</span> turbine nacelle. During the event, a complete electricity grid failure is simulated while the turbine is at rated <span class="hlt">speed</span> and predefined torque levels. Particular focus is on the characterization of the high-<span class="hlt">speed</span> shaft tapered roller bearing slip behavior. Strain-gauge bridges in grooves along the circumference of the outer ring are used to characterize the bearing load zone in detail. It is shown that during the torque reversals of the transient event, roller slip can be induced. This indicates the potential of the applied load case to go beyond the preload of the tapered roller bearing. Furthermore, the relation between the applied torque and skidding level is studied.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/6564874-wind-power-jamaica','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/6564874-wind-power-jamaica"><span><span class="hlt">Wind</span> power in Jamaica</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Chen, A.A.; Daniel, A.R.; Daniel, S.T.</p> <p>1990-01-01</p> <p>Parameters to evaluate the potential for using <span class="hlt">wind</span> energy to generate electricity in Jamaica were obtained. These include the average <span class="hlt">wind</span> power scaled to a height of 20 m at existing weather stations and temporary anemometer sites, the variation in annual and monthly <span class="hlt">wind</span> power, and the frequency distribution of <span class="hlt">wind</span> <span class="hlt">speed</span> and <span class="hlt">wind</span> energy available. Four small commercial turbines were assumed to be operating at some of the sites, and the estimated energy captured by them, the time they operated above their cut-in <span class="hlt">speed</span> and their capacity factors were also determined. Diurnal variations of <span class="hlt">wind</span> <span class="hlt">speed</span> and prevailing windmore » directions are discussed and a map showing <span class="hlt">wind</span> power at various sites was produced. Two stations with long-term averages, Manley and Morant Point, gave results which warranted further investigation. Results from some temporary stations are also encouraging. Mean <span class="hlt">wind</span> <span class="hlt">speeds</span> at two other sites in the Caribbean are given for comparison. A method for estimating the power exponent for scaling the <span class="hlt">wind</span> <span class="hlt">speed</span> from climatic data is described in Appendix 2.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018MS%26E..295a2023W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018MS%26E..295a2023W"><span>Analysis of Failures of High <span class="hlt">Speed</span> Shaft Bearing System in a <span class="hlt">Wind</span> Turbine</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wasilczuk, Michał; Gawarkiewicz, Rafał; Bastian, Bartosz</p> <p>2018-01-01</p> <p>During the operation of <span class="hlt">wind</span> turbines with gearbox of traditional configuration, consisting of one planetary stage and two helical stages high failure rate of high <span class="hlt">speed</span> shaft bearings is observed. Such a high failures frequency is not reflected in the results of standard calculations of bearing durability. Most probably it can be attributed to atypical failure mechanism. The authors studied problems in 1.5 MW <span class="hlt">wind</span> turbines of one of Polish <span class="hlt">wind</span> farms. The analysis showed that the problems of high failure rate are commonly met all over the world and that the statistics for the analysed turbines were very similar. After the study of potential failure mechanism and its potential reasons, modification of the existing bearing system was proposed. Various options, with different bearing types were investigated. Different versions were examined for: expected durability increase, extent of necessary gearbox modifications and possibility to solve existing problems in operation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20060036834&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20060036834&hterms=WIND+STORMS&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DWIND%2BSTORMS"><span>The Distant Tail Behavior During High <span class="hlt">Speed</span> Solar <span class="hlt">Wind</span> Streams and Magnetic Storms</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ho, C. M.; Tsurutani, B. T.</p> <p>1996-01-01</p> <p>We have examined the ISEE-3 distant tail data during three intense (Dst< -100(sub n)T) magnetic storms and have identified the tail response to high <span class="hlt">speed</span> solar <span class="hlt">wind</span> streams, interplanetary magnetic clouds, and near-Earth storms. The three storms have a peak Dst ranging from -150 to -220 nT, and occur on Jan. 9, Feb. 4, and Aug. 8, 1993.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1236155-wind-measurements-from-arc-scans-doppler-wind-lidar','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1236155-wind-measurements-from-arc-scans-doppler-wind-lidar"><span><span class="hlt">Wind</span> Measurements from Arc Scans with Doppler <span class="hlt">Wind</span> Lidar</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Wang, H.; Barthelmie, R. J.; Clifton, Andy; ...</p> <p>2015-11-25</p> <p>When defining optimal scanning geometries for scanning lidars for <span class="hlt">wind</span> energy applications, we found that it is still an active field of research. Our paper evaluates uncertainties associated with arc scan geometries and presents recommendations regarding optimal configurations in the atmospheric boundary layer. The analysis is based on arc scan data from a Doppler <span class="hlt">wind</span> lidar with one elevation angle and seven azimuth angles spanning 30° and focuses on an estimation of 10-min mean <span class="hlt">wind</span> <span class="hlt">speed</span> and direction. When flow is horizontally uniform, this approach can provide accurate <span class="hlt">wind</span> measurements required for <span class="hlt">wind</span> resource assessments in part because of itsmore » high resampling rate. Retrieved <span class="hlt">wind</span> velocities at a single range gate exhibit good correlation to data from a sonic anemometer on a nearby meteorological tower, and vertical profiles of horizontal <span class="hlt">wind</span> <span class="hlt">speed</span>, though derived from range gates located on a conical surface, match those measured by mast-mounted cup anemometers. Uncertainties in the retrieved <span class="hlt">wind</span> velocity are related to high turbulent <span class="hlt">wind</span> fluctuation and an inhomogeneous horizontal <span class="hlt">wind</span> field. Moreover, the radial velocity variance is found to be a robust measure of the uncertainty of the retrieved <span class="hlt">wind</span> <span class="hlt">speed</span> because of its relationship to turbulence properties. It is further shown that the standard error of <span class="hlt">wind</span> <span class="hlt">speed</span> estimates can be minimized by increasing the azimuthal range beyond 30° and using five to seven azimuth angles.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25896122','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25896122"><span>Expertise effects in cutaneous <span class="hlt">wind</span> perception.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pluijms, Joost P; Cañal-Bruland, Rouwen; Bergmann Tiest, Wouter M; Mulder, Fabian A; Savelsbergh, Geert J P</p> <p>2015-08-01</p> <p>We examined whether expertise effects are present in cutaneous <span class="hlt">wind</span> perception. To this end, we presented <span class="hlt">wind</span> stimuli consisting of different <span class="hlt">wind</span> directions and <span class="hlt">speeds</span> in a <span class="hlt">wind</span> simulator. The <span class="hlt">wind</span> simulator generated <span class="hlt">wind</span> stimuli from 16 directions and with three <span class="hlt">speeds</span> by means of eight automotive <span class="hlt">wind</span> fans. Participants were asked to judge cutaneously perceived <span class="hlt">wind</span> directions and <span class="hlt">speeds</span> without having access to any visual or auditory information. Expert sailors (n = 6), trained to make the most effective use of <span class="hlt">wind</span> characteristics, were compared to less-skilled sailors (n = 6) and to a group of nonsailors (n = 6). The results indicated that expert sailors outperformed nonsailors in perceiving <span class="hlt">wind</span> direction (i.e., smaller mean signed errors) when presented with low <span class="hlt">wind</span> <span class="hlt">speeds</span>. This suggests that expert sailors are more sensitive in picking up differences in <span class="hlt">wind</span> direction, particularly when confronted with low <span class="hlt">wind</span> <span class="hlt">speeds</span> that demand higher sensitivity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010DPS....42.1101S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010DPS....42.1101S"><span>Longitudinal Variations in Jupiter's <span class="hlt">Winds</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Simon-Miller, Amy A.; Gierasch, P. J.; Tierney, G.</p> <p>2010-10-01</p> <p>Long-term studies of Jupiter's <span class="hlt">zonal</span> <span class="hlt">wind</span> field revealed temporal variations on the order of 20 to 40 m/s at many latitudes, greater than the typical data uncertainties of 1 to 10 m/s. No definitive periodicities were evident, however, though some latitudinally-confined signals did appear at periods relevant to the Quasi-Quadrennial Oscillation (Simon-Miller & Gierasch, Icarus, in press). As the QQO appears, from vertical temperature profiles, to propagate downward, it is unclear why a signal is not more obvious, unless other processes dominate over possibly weaker forcing from the QQO. An additional complication is that <span class="hlt">zonal</span> <span class="hlt">wind</span> profiles represent an average over some particular set of longitudes for an image pair and most data sets do not offer global <span class="hlt">wind</span> coverage. Even avoiding known features, such as the large anticyclonic vortices especially prevalent in the south, there can be distinct variations in longitude. We present results on the full <span class="hlt">wind</span> field from Voyager and Cassini data, showing apparent longitudinal variations of up to 60 m/s or more. These are particularly obvious near disruptions such as the South Equatorial Disturbance, even when the feature itself is not clearly visible. These two dates represent very different states of the planet for comparison: Voyagers 1 & 2 flew by Jupiter shortly after a global upheaval, while many regions were in a disturbed state, while the Cassini view is typical of a more quiescent period present during much of the 1990s and early 2000s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110005648','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110005648"><span>Longitudinal Variations in Jupiter's <span class="hlt">Winds</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Simon-Miller, Amy A.; Gierasch, P. J.; Tierney, G.</p> <p>2010-01-01</p> <p>Long-term studies of Jupiter's <span class="hlt">zonal</span> <span class="hlt">wind</span> field revealed temporal variations on the order of 20 to 40 m/s at many latitudes, greater than the typical data uncertainties of 1 to 10 m/s. No definitive periodicities were evident, however, though some latitudinally-confined signals did appear at periods relevant to the Quasi- Quadrennial Oscillation (Simon-Miller & Gierasch, Icarus, in press). As the QQO appears, from vertical temperature profiles, to propagate downward, it is unclear why a signal is not more obvious, unless other processes dominate over possibly weaker forcing from the QQO. An additional complication is that <span class="hlt">zonal</span> <span class="hlt">wind</span> profiles represent an average over some particular set of longitudes for an image pair and most data sets do not offer global <span class="hlt">wind</span> coverage. Lien avoiding known features, such as the large anticyclonic vortices especially prevalent in the south, there can be distinct variations in longitude. We present results on the full <span class="hlt">wind</span> field from Voyager and Cassini data, showing apparent longitudinal variations of up to 60 m/s or more. These are particularly obvious near disruptions such as the South Equatorial Disturbance, even when the feature itself is not clearly visible. These two dates represent very different states of the planet for comparison: Voyagers 1 & 2 flew by Jupiter shortly after a global upheaval, while many regions were in a disturbed state, while the Cassini view is typical of a more quiescent period present during much of the 1990s and early 2000s.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27872902','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27872902"><span><span class="hlt">Wind</span> energy potential assessment of Cameroon's coastal regions for the installation of an onshore <span class="hlt">wind</span> farm.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Arreyndip, Nkongho Ayuketang; Joseph, Ebobenow; David, Afungchui</p> <p>2016-11-01</p> <p>For the future installation of a <span class="hlt">wind</span> farm in Cameroon, the <span class="hlt">wind</span> energy potentials of three of Cameroon's coastal cities (Kribi, Douala and Limbe) are assessed using NASA average monthly <span class="hlt">wind</span> data for 31 years (1983-2013) and compared through Weibull statistics. The Weibull parameters are estimated by the method of maximum likelihood, the mean power densities, the maximum energy carrying <span class="hlt">wind</span> <span class="hlt">speeds</span> and the most probable <span class="hlt">wind</span> <span class="hlt">speeds</span> are also calculated and compared over these three cities. Finally, the cumulative <span class="hlt">wind</span> <span class="hlt">speed</span> distributions over the wet and dry seasons are also analyzed. The results show that the shape and scale parameters for Kribi, Douala and Limbe are 2.9 and 2.8, 3.9 and 1.8 and 3.08 and 2.58, respectively. The mean power densities through Weibull analysis for Kribi, Douala and Limbe are 33.7 W/m2, 8.0 W/m2 and 25.42 W/m2, respectively. Kribi's most probable <span class="hlt">wind</span> <span class="hlt">speed</span> and maximum energy carrying <span class="hlt">wind</span> <span class="hlt">speed</span> was found to be 2.42 m/s and 3.35 m/s, 2.27 m/s and 3.03 m/s for Limbe and 1.67 m/s and 2.0 m/s for Douala, respectively. Analysis of the <span class="hlt">wind</span> <span class="hlt">speed</span> and hence power distribution over the wet and dry seasons shows that in the wet season, August is the windiest month for Douala and Limbe while September is the windiest month for Kribi while in the dry season, March is the windiest month for Douala and Limbe while February is the windiest month for Kribi. In terms of mean power density, most probable <span class="hlt">wind</span> <span class="hlt">speed</span> and <span class="hlt">wind</span> <span class="hlt">speed</span> carrying maximum energy, Kribi shows to be the best site for the installation of a <span class="hlt">wind</span> farm. Generally, the <span class="hlt">wind</span> <span class="hlt">speeds</span> at all three locations seem quite low, average <span class="hlt">wind</span> <span class="hlt">speeds</span> of all the three studied locations fall below 4.0m/s which is far below the cut-in <span class="hlt">wind</span> <span class="hlt">speed</span> of many modern <span class="hlt">wind</span> turbines. However we recommend the use of low cut-in <span class="hlt">speed</span> <span class="hlt">wind</span> turbines like the Savonius for stand alone low energy needs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFMNH51D1933B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFMNH51D1933B"><span>Modelling the 2013 Typhoon Haiyan storm surge: Effect of waves, offshore <span class="hlt">winds</span>, tide phase, and translation <span class="hlt">speed</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bilgera, P. H. T.</p> <p>2015-12-01</p> <p>Super Typhoon Haiyan, with <span class="hlt">wind</span> <span class="hlt">speeds</span> exceeding 300 km h-1 (160 knots) generated a storm surge in San Pedro Bay reaching heights of more than 6m in Tacloban City. Delft Dashboard (DDB), an open-source standalone Matlab based graphical user interface linked to the FLOW and WAVE modeling software of Deltares, was used to develop a coupled flow and wave storm surge model to understand the Typhoon Haiyan storm surge development and propagation. Various experiments were designed to determine the effect of waves, the occurrence of offshore <span class="hlt">winds</span> prior to the surge, tidal phase, and typhoon translation <span class="hlt">speed</span> on the surge height. Wave coupling decreased the surge height by about 0.5m probably due to energy dissipation from white capping, bottom friction, and depth-induced breaking. Offshore-directed <span class="hlt">winds</span> before the arrival of the storm eye resulted to receding of the water level in San Pedro and Cancabato Bay, corroborated by eyewitness and tide gauge data. The experiment wherein the offshore <span class="hlt">winds</span> were removed resulted to no water receding and a surge with a smaller and gentler surge front, pointing to the importance of the initial water level drawdown in contributing to the destructive power of the wave front. With regard to tides, the effect in Tacloban was actually neither linear nor additive to the surge, with higher surge coincident to low tides and lower surge coincident to high tides. Lastly, the model run with typhoon having a slower translation <span class="hlt">speed</span> than Haiyan was found to generate higher surges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AGUOSEC34B1174B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AGUOSEC34B1174B"><span>Modelling the 2013 Typhoon Haiyan Storm Surge: Effect of Waves, Offshore <span class="hlt">Winds</span>, Tide Phase, and Translation <span class="hlt">Speed</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bilgera, P. H. T.; Villanoy, C.; Cabrera, O.</p> <p>2016-02-01</p> <p>Super Typhoon Haiyan, with <span class="hlt">wind</span> <span class="hlt">speeds</span> exceeding 300 km h-1 (160 knots) generated a storm surge in San Pedro Bay reaching heights of more than 6m in Tacloban City. Delft Dashboard (DDB), an open-source standalone Matlab based graphical user interface linked to the FLOW and WAVE modeling software of Deltares, was used to develop a coupled flow and wave storm surge model to understand the Typhoon Haiyan storm surge development and propagation. Various experiments were designed to determine the effect of waves, the occurrence of offshore <span class="hlt">winds</span> prior to the surge, tidal phase, and typhoon translation <span class="hlt">speed</span> on the surge height. Wave coupling decreased the surge height by about 0.5m probably due to energy dissipation from white capping, bottom friction, and depth-induced breaking. Offshore-directed <span class="hlt">winds</span> before the arrival of the storm eye resulted to receding of the water level in San Pedro and Cancabato Bay, corroborated by eyewitness and tide gauge data. The experiment wherein the offshore <span class="hlt">winds</span> were removed resulted to no water receding and a surge with a smaller and gentler surge front, pointing to the importance of the initial water level drawdown in contributing to the destructive power of the wave front. With regard to tides, the effect in Tacloban was actually neither linear nor additive to the surge, with higher surge coincident to low tides and lower surge coincident to high tides. Lastly, the model run with typhoon having a slower translation <span class="hlt">speed</span> than Haiyan was found to generate higher surges.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310480K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310480K"><span>Global composites of surface <span class="hlt">wind</span> <span class="hlt">speeds</span> in tropical cyclones based on a 12 year scatterometer database</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Klotz, Bradley W.; Jiang, Haiyan</p> <p>2016-10-01</p> <p>A 12 year global database of rain-corrected satellite scatterometer surface <span class="hlt">winds</span> for tropical cyclones (TCs) is used to produce composites of TC surface <span class="hlt">wind</span> <span class="hlt">speed</span> distributions relative to vertical <span class="hlt">wind</span> shear and storm motion directions in each TC-prone basin and various TC intensity stages. These composites corroborate ideas presented in earlier studies, where maxima are located right of motion in the Earth-relative framework. The entire TC surface <span class="hlt">wind</span> asymmetry is down motion left for all basins and for lower strength TCs after removing the motion vector. Relative to the shear direction, the motion-removed composites indicate that the surface <span class="hlt">wind</span> asymmetry is located down shear left for the outer region of all TCs, but for the inner-core region it varies from left of shear to down shear right for different basin and TC intensity groups. Quantification of the surface <span class="hlt">wind</span> asymmetric structure in further stratifications is a necessary next step for this scatterometer data set.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/biblio/1365828-zonal-flows-turbulence-fluids-plasmas','SCIGOV-STC'); return false;" href="https://www.osti.gov/biblio/1365828-zonal-flows-turbulence-fluids-plasmas"><span><span class="hlt">Zonal</span> Flows and Turbulence in Fluids and Plasmas</span></a></p> <p><a target="_blank" href="http://www.osti.gov/search">DOE Office of Scientific and Technical Information (OSTI.GOV)</a></p> <p>Parker, Jeffrey</p> <p>2014-09-01</p> <p>In geophysical and plasma contexts, <span class="hlt">zonal</span> flows are well known to arise out of turbulence. We elucidate the transition from statistically homogeneous turbulence without <span class="hlt">zonal</span> flows to statistically inhomogeneous turbulence with steady <span class="hlt">zonal</span> flows. Starting from the Hasegawa--Mima equation, we employ both the quasilinear approximation and a statistical average, which retains a great deal of the qualitative behavior of the full system. Within the resulting framework known as CE2, we extend recent understanding of the symmetry-breaking `zonostrophic instability'. Zonostrophic instability can be understood in a very general way as the instability of some turbulent background spectrum to a <span class="hlt">zonally</span> symmetricmore » coherent mode. As a special case, the background spectrum can consist of only a single mode. We find that in this case the dispersion relation of zonostrophic instability from the CE2 formalism reduces exactly to that of the 4-mode truncation of generalized modulational instability. We then show that <span class="hlt">zonal</span> flows constitute pattern formation amid a turbulent bath. Zonostrophic instability is an example of a Type Is instability of pattern-forming systems. The broken symmetry is statistical homogeneity. Near the bifurcation point, the slow dynamics of CE2 are governed by a well-known amplitude equation, the real Ginzburg-Landau equation. The important features of this amplitude equation, and therefore of the CE2 system, are multiple. First, the <span class="hlt">zonal</span> flow wavelength is not unique. In an idealized, infinite system, there is a continuous band of <span class="hlt">zonal</span> flow wavelengths that allow a nonlinear equilibrium. Second, of these wavelengths, only those within a smaller subband are stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets. These behaviors are shown numerically to hold in the CE2 system, and we calculate a stability diagram. The stability diagram is in agreement with direct numerical simulations of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.......165P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.......165P"><span><span class="hlt">Zonal</span> flows and turbulence in fluids and plasmas</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Parker, Jeffrey Bok-Cheung</p> <p></p> <p>In geophysical and plasma contexts, <span class="hlt">zonal</span> flows are well known to arise out of turbulence. We elucidate the transition from statistically homogeneous turbulence without <span class="hlt">zonal</span> flows to statistically inhomogeneous turbulence with steady <span class="hlt">zonal</span> flows. Starting from the Hasegawa--Mima equation, we employ both the quasilinear approximation and a statistical average, which retains a great deal of the qualitative behavior of the full system. Within the resulting framework known as CE2, we extend recent understanding of the symmetry-breaking 'zonostrophic instability'. Zonostrophic instability can be understood in a very general way as the instability of some turbulent background spectrum to a <span class="hlt">zonally</span> symmetric coherent mode. As a special case, the background spectrum can consist of only a single mode. We find that in this case the dispersion relation of zonostrophic instability from the CE2 formalism reduces exactly to that of the 4-mode truncation of generalized modulational instability. We then show that <span class="hlt">zonal</span> flows constitute pattern formation amid a turbulent bath. Zonostrophic instability is an example of a Type I s instability of pattern-forming systems. The broken symmetry is statistical homogeneity. Near the bifurcation point, the slow dynamics of CE2 are governed by a well-known amplitude equation, the real Ginzburg-Landau equation. The important features of this amplitude equation, and therefore of the CE2 system, are multiple. First, the <span class="hlt">zonal</span> flow wavelength is not unique. In an idealized, infinite system, there is a continuous band of <span class="hlt">zonal</span> flow wavelengths that allow a nonlinear equilibrium. Second, of these wavelengths, only those within a smaller subband are stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets. These behaviors are shown numerically to hold in the CE2 system, and we calculate a stability diagram. The stability diagram is in agreement with direct numerical simulations of the quasilinear</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991IJRSP..20...82R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991IJRSP..20...82R"><span><span class="hlt">Winds</span> in the meteor zone over Trivandrum</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reddi, C. R.; Rajeev, K.; Ramakumar, Geetha</p> <p>1991-04-01</p> <p>The height profiles of the <span class="hlt">zonal</span> and meridional <span class="hlt">wind</span> obtained from the meteor <span class="hlt">wind</span> radar data recorded at Trivandrum (8 deg 36 min N, 77 deg E) are presented. Large <span class="hlt">wind</span> shears were found to exist in the meteor zone over Trivandrum. The profiles showed quasi-sinusoidal variations with altitude and vertical wavelength of the oscillation in the range 15-25 km. Further, there was a large day-to-day variability in the profiles obtained for the same local time on consecutive days. The results are discussed in the light of the <span class="hlt">winds</span> due to tides and equatorial waves in the low latitudes. The implications of the large <span class="hlt">wind</span> shears with reference to the local <span class="hlt">wind</span> effects on the equatorial electrojet are outlined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20160006332','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20160006332"><span>9- by 15-Foot Low <span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel Acoustic Improvements Expanded Overview</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stephens, David</p> <p>2016-01-01</p> <p>The 9- by 15-Foot Low <span class="hlt">Speed</span> <span class="hlt">Wind</span> Tunnel (9x15 LSWT) at NASA Glenn Research Center was built in 1969 in the return leg of the 8- by 6-Foot Supersonic <span class="hlt">Wind</span> Tunnel (8x6 SWT). The 8x6 SWT was completed in 1949 and acoustically treated to mitigate community noise issues in 1950. This treatment included the addition of a large muffler downstream of the 8x6 SWT test section and diffuser. The 9x15 LSWT was designed for performance testing of V/STOL aircraft models, but with the addition of the current acoustic treatment in 1986 the tunnel been used principally for acoustic and performance testing of aircraft propulsion systems. The present document describes an anticipated acoustic upgrade to be completed in 2017.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20080021728','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20080021728"><span>Peak <span class="hlt">Wind</span> Tool for General Forecasting</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Barrett, Joe H., III; Short, David</p> <p>2008-01-01</p> <p>This report describes work done by the Applied Meteorology Unit (AMU) in predicting peak <span class="hlt">winds</span> at Kennedy Space Center (KSC) and Cape Canaveral Air Force Station (CCAFS). The 45th Weather Squadron requested the AMU develop a tool to help them forecast the <span class="hlt">speed</span> and timing of the daily peak and average <span class="hlt">wind</span>, from the surface to 300 ft on KSC/CCAFS during the cool season. Based on observations from the KSC/CCAFS <span class="hlt">wind</span> tower network , Shuttle Landing Facility (SLF) surface observations, and CCAFS sounding s from the cool season months of October 2002 to February 2007, the AMU created mul tiple linear regression equations to predict the timing and <span class="hlt">speed</span> of the daily peak <span class="hlt">wind</span> <span class="hlt">speed</span>, as well as the background average <span class="hlt">wind</span> <span class="hlt">speed</span>. Several possible predictors were evaluated, including persistence , the temperature inversion depth and strength, <span class="hlt">wind</span> <span class="hlt">speed</span> at the top of the inversion, <span class="hlt">wind</span> gust factor (ratio of peak <span class="hlt">wind</span> <span class="hlt">speed</span> to average <span class="hlt">wind</span> <span class="hlt">speed</span>), synoptic weather pattern, occurrence of precipitation at the SLF, and strongest <span class="hlt">wind</span> in the lowest 3000 ft, 4000 ft, or 5000 ft.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21195458','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21195458"><span>Application of nonparametric regression methods to study the relationship between NO2 concentrations and local <span class="hlt">wind</span> direction and <span class="hlt">speed</span> at background sites.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Donnelly, Aoife; Misstear, Bruce; Broderick, Brian</p> <p>2011-02-15</p> <p>Background concentrations of nitrogen dioxide (NO(2)) are not constant but vary temporally and spatially. The current paper presents a powerful tool for the quantification of the effects of <span class="hlt">wind</span> direction and <span class="hlt">wind</span> <span class="hlt">speed</span> on background NO(2) concentrations, particularly in cases where monitoring data are limited. In contrast to previous studies which applied similar methods to sites directly affected by local pollution sources, the current study focuses on background sites with the aim of improving methods for predicting background concentrations adopted in air quality modelling studies. The relationship between measured NO(2) concentration in air at three such sites in Ireland and locally measured <span class="hlt">wind</span> direction has been quantified using nonparametric regression methods. The major aim was to analyse a method for quantifying the effects of local <span class="hlt">wind</span> direction on background levels of NO(2) in Ireland. The method was expanded to include <span class="hlt">wind</span> <span class="hlt">speed</span> as an added predictor variable. A Gaussian kernel function is used in the analysis and circular statistics employed for the <span class="hlt">wind</span> direction variable. <span class="hlt">Wind</span> direction and <span class="hlt">wind</span> <span class="hlt">speed</span> were both found to have a statistically significant effect on background levels of NO(2) at all three sites. Frequently environmental impact assessments are based on short term baseline monitoring producing a limited dataset. The presented non-parametric regression methods, in contrast to the frequently used methods such as binning of the data, allow concentrations for missing data pairs to be estimated and distinction between spurious and true peaks in concentrations to be made. The methods were found to provide a realistic estimation of long term concentration variation with <span class="hlt">wind</span> direction and <span class="hlt">speed</span>, even for cases where the data set is limited. Accurate identification of the actual variation at each location and causative factors could be made, thus supporting the improved definition of background concentrations for use in air quality modelling</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2018GeoRL..45.4586S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2018GeoRL..45.4586S"><span>High-Latitude Observations of a Localized <span class="hlt">Wind</span> Wall and Its Coupling to the Lower Thermosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shepherd, Gordon G.; Shepherd, Marianna G.</p> <p>2018-05-01</p> <p>Reversals in the thermospheric <span class="hlt">zonal</span> <span class="hlt">winds</span> at altitudes of 140 to 250 km from eastward to westward have been found at southern geographic latitudes between 60° and 70°. These are confined to a narrow region between 100° and 200° in longitude with <span class="hlt">zonal</span> velocities regularly of -400 m/s, sometimes reaching -600 m/s, so sharply defined that the authors describe it as a "<span class="hlt">wind</span> wall." The observations were made by the <span class="hlt">Wind</span> Imaging Interferometer on National Aeronautics and Space Administration's Upper Atmosphere Research Satellite, and they occur as the field of view crosses the high polar cap <span class="hlt">wind</span> field. The <span class="hlt">wind</span> reversals at the wall boundaries create a convergence on the west side of the wall and a divergence on the east side that potentially generate vertical flows, consistent with observed perturbations in the O(1S) emission rate. They are present about one half of the time in local summer and autumn.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999APS..DPP.FI101D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999APS..DPP.FI101D"><span>Transport in <span class="hlt">zonal</span> flows in analogous geophysical and plasma systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>del-Castillo-Negrete, Diego</p> <p>1999-11-01</p> <p><span class="hlt">Zonal</span> flows occur naturally in the oceans and the atmosphere of planets. Important examples include the <span class="hlt">zonal</span> flows in Jupiter, the stratospheric polar jet in Antarctica, and oceanic jets like the Gulf Stream. These <span class="hlt">zonal</span> flows create transport barriers that have a crucial influence on mixing and confinement (e.g. the ozone depletion in Antarctica). <span class="hlt">Zonal</span> flows also give rise to long-lasting vortices (e.g. the Jupiter red spot) by shear instability. Because of this, the formation and stability of <span class="hlt">zonal</span> flows and their role on transport have been problems of great interest in geophysical fluid dynamics. On the other hand, <span class="hlt">zonal</span> flows have also been observed in fusion plasmas and their impact on the reduction of transport has been widely recognized. Based on the well-known analogy between Rossby waves in quasigeostrophic flows and drift waves in magnetically confined plasmas, I will discuss the relevance to fusion plasmas of models and experiments recently developed in geophysical fluid dynamics. Also, the potential application of plasma physics ideas to geophysical flows will be discussed. The role of shear in the suppression of transport and the effect of <span class="hlt">zonal</span> flows on the statistics of transport will be studied using simplified models. It will be shown how <span class="hlt">zonal</span> flows induce large particle displacements that can be characterized as Lévy flights, and that the trapping effect of vortices combined with the <span class="hlt">zonal</span> flows gives rise to anomalous diffusion and Lévy (non-Gaussian) statistics. The models will be compared with laboratory experiments and with atmospheric and oceanographic qualitative observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790006806','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790006806"><span>Estimation of Venus <span class="hlt">wind</span> velocities from high-resolution infrared spectra. Ph.D. Thesis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Smith, M. A. H.</p> <p>1978-01-01</p> <p><span class="hlt">Zonal</span> velocity profiles in the Venus atmosphere above the clouds were estimated from measured asymmetries of HCl and HF infrared absorption lines in high-resolution Fourier interferometer spectra of the planet. These asymmetries are caused by both pressure-induced shifts in the positions of the hydrogen-halide lines perturbed by CO2 and Doppler shifts due to atmospheric motions. Particularly in the case of the HCl 2-0 band, the effects of the two types of line shifts can be easily isolated, making it possible to estimate a profile of average Venus equatorial <span class="hlt">zonal</span> velocity as a function of pressure in the region roughly 60 to 70 km above the surface of the planet. The mean profiles obtained show strong vertical shear in the Venus <span class="hlt">zonal</span> <span class="hlt">winds</span> near the cloud-top level, and both the magnitude and direction of <span class="hlt">winds</span> at all levels in this region appear to vary greatly with longitude relative to the sub-solar point.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5107252','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5107252"><span>The Impact of Variable <span class="hlt">Wind</span> Shear Coefficients on Risk Reduction of <span class="hlt">Wind</span> Energy Projects</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Thomson, Allan; Yoonesi, Behrang; McNutt, Josiah</p> <p>2016-01-01</p> <p>Estimation of <span class="hlt">wind</span> <span class="hlt">speed</span> at proposed hub heights is typically achieved using a <span class="hlt">wind</span> shear exponent or <span class="hlt">wind</span> shear coefficient (WSC), variation in <span class="hlt">wind</span> <span class="hlt">speed</span> as a function of height. The WSC is subject to temporal variation at low and high frequencies, ranging from diurnal and seasonal variations to disturbance caused by weather patterns; however, in many cases, it is assumed that the WSC remains constant. This assumption creates significant error in resource assessment, increasing uncertainty in projects and potentially significantly impacting the ability to control gird connected <span class="hlt">wind</span> generators. This paper contributes to the body of knowledge relating to the evaluation and assessment of <span class="hlt">wind</span> <span class="hlt">speed</span>, with particular emphasis on the development of techniques to improve the accuracy of estimated <span class="hlt">wind</span> <span class="hlt">speed</span> above measurement height. It presents an evaluation of the use of a variable <span class="hlt">wind</span> shear coefficient methodology based on a distribution of <span class="hlt">wind</span> shear coefficients which have been implemented in real time. The results indicate that a VWSC provides a more accurate estimate of <span class="hlt">wind</span> at hub height, ranging from 41% to 4% reduction in root mean squared error (RMSE) between predicted and actual <span class="hlt">wind</span> <span class="hlt">speeds</span> when using a variable <span class="hlt">wind</span> shear coefficient at heights ranging from 33% to 100% above the highest actual <span class="hlt">wind</span> measurement. PMID:27872898</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4442747','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4442747"><span>Outdoor temperature, precipitation, and <span class="hlt">wind</span> <span class="hlt">speed</span> affect physical activity levels in children: a longitudinal cohort study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Edwards, Nicholas M.; Myer, Gregory D.; Kalkwarf, Heidi J.; Woo, Jessica G.; Khoury, Philip R.; Hewett, Timothy E.; Daniels, Stephen R.</p> <p>2015-01-01</p> <p>Objective Evaluate effects of local weather conditions on physical activity in early childhood. Methods Longitudinal prospective cohort study of 372 children, 3 years old at enrollment, drawn from a major US metropolitan community. Accelerometer-measured (RT3) physical activity was collected every 4 months over 5 years and matched with daily weather measures: day length, heating/cooling degrees (degrees mean temperature < 65°F or ≥ 65°F, respectively), <span class="hlt">wind</span>, and precipitation. Mixed regression analyses, adjusted for repeated measures, were used to test the relationship between weather and physical activity. Results Precipitation and <span class="hlt">wind</span> <span class="hlt">speed</span> were negatively associated with total physical activity and moderate-vigorous physical activity (P<0.0001). Heating and cooling degrees were negatively associated with total physical activity and moderate-vigorous physical activity and positively associated with inactivity (all P<0.0001), independent of age, sex, race, BMI, day length, <span class="hlt">wind</span>, and precipitation. For every 10 additional heating degrees there was a five-minute daily reduction in moderate-vigorous physical activity. For every additional 10 cooling degrees there was a 17-minute reduction in moderate-vigorous physical activity. Conclusions Inclement weather (higher/lower temperature, greater <span class="hlt">wind</span> <span class="hlt">speed</span>, more rain/snow) is associated with less physical activity in young children. These deleterious effects should be considered when planning physical activity research, interventions, and policies. PMID:25423667</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28539514','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28539514"><span><span class="hlt">Wind</span> conditions and geography shape the first outbound migration of juvenile honey buzzards and their distribution across sub-Saharan Africa.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Vansteelant, W M G; Kekkonen, J; Byholm, P</p> <p>2017-05-31</p> <p>Contemporary tracking studies reveal that low migratory connectivity between breeding and non-breeding ranges is common in migrant landbirds. It is unclear, however, how internal factors and early-life experiences of individual migrants shape the development of their migration routes and concomitant population-level non-breeding distributions. Stochastic <span class="hlt">wind</span> conditions and geography may determine whether and where migrants end up by the end of their journey. We tested this hypothesis by satellite-tagging 31 fledgling honey buzzards Pernis apivorus from southern Finland and used a global atmospheric reanalysis model to estimate the <span class="hlt">wind</span> conditions they encountered on their first outbound migration. Migration routes diverged rapidly upon departure and the birds eventually spread out across 3340 km of longitude. Using linear regression models, we show that the birds' longitudinal <span class="hlt">speeds</span> were strongly affected by <span class="hlt">zonal</span> <span class="hlt">wind</span> <span class="hlt">speed</span>, and negatively affected by latitudinal <span class="hlt">wind</span>, with significant but minor differences between individuals. Eventually, 49% of variability in the birds' total longitudinal displacements was accounted for by <span class="hlt">wind</span> conditions on migration. Some birds circumvented the Baltic Sea via Scandinavia or engaged in unusual downwind movements over the Mediterranean, which also affected the longitude at which these individuals arrived in sub-Saharan Africa. To understand why adult migrants use the migration routes and non-breeding sites they use, we must take into account the way in which <span class="hlt">wind</span> conditions moulded their very first journeys. Our results present some of the first evidence into the mechanisms through which low migratory connectivity emerges. © 2017 The Authors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5454264','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5454264"><span><span class="hlt">Wind</span> conditions and geography shape the first outbound migration of juvenile honey buzzards and their distribution across sub-Saharan Africa</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kekkonen, J.; Byholm, P.</p> <p>2017-01-01</p> <p>Contemporary tracking studies reveal that low migratory connectivity between breeding and non-breeding ranges is common in migrant landbirds. It is unclear, however, how internal factors and early-life experiences of individual migrants shape the development of their migration routes and concomitant population-level non-breeding distributions. Stochastic <span class="hlt">wind</span> conditions and geography may determine whether and where migrants end up by the end of their journey. We tested this hypothesis by satellite-tagging 31 fledgling honey buzzards Pernis apivorus from southern Finland and used a global atmospheric reanalysis model to estimate the <span class="hlt">wind</span> conditions they encountered on their first outbound migration. Migration routes diverged rapidly upon departure and the birds eventually spread out across 3340 km of longitude. Using linear regression models, we show that the birds' longitudinal <span class="hlt">speeds</span> were strongly affected by <span class="hlt">zonal</span> <span class="hlt">wind</span> <span class="hlt">speed</span>, and negatively affected by latitudinal <span class="hlt">wind</span>, with significant but minor differences between individuals. Eventually, 49% of variability in the birds' total longitudinal displacements was accounted for by <span class="hlt">wind</span> conditions on migration. Some birds circumvented the Baltic Sea via Scandinavia or engaged in unusual downwind movements over the Mediterranean, which also affected the longitude at which these individuals arrived in sub-Saharan Africa. To understand why adult migrants use the migration routes and non-breeding sites they use, we must take into account the way in which <span class="hlt">wind</span> conditions moulded their very first journeys. Our results present some of the first evidence into the mechanisms through which low migratory connectivity emerges. PMID:28539514</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=227238','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=227238"><span>Process model for ammonia volatilization from anaerobic swine lagoons incorporating varying <span class="hlt">wind</span> <span class="hlt">speeds</span> and biogas bubbling</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>Ammonia volatilization from treatment lagoons varies widely with the total ammonia concentration, pH, temperature, suspended solids, atmospheric ammonia concentration above the water surface, and <span class="hlt">wind</span> <span class="hlt">speed</span>. Ammonia emissions were estimated with a process-based mechanistic model integrating ammonia ...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/servlets/purl/866187','DOE-PATENT-XML'); return false;" href="https://www.osti.gov/servlets/purl/866187"><span><span class="hlt">Wind</span> energy conversion system</span></a></p> <p><a target="_blank" href="http://www.osti.gov/doepatents">DOEpatents</a></p> <p>Longrigg, Paul</p> <p>1987-01-01</p> <p>The <span class="hlt">wind</span> energy conversion system includes a <span class="hlt">wind</span> machine having a propeller connected to a generator of electric power, the propeller rotating the generator in response to force of an incident <span class="hlt">wind</span>. The generator converts the power of the <span class="hlt">wind</span> to electric power for use by an electric load. Circuitry for varying the duty factor of the generator output power is connected between the generator and the load to thereby alter a loading of the generator and the propeller by the electric load. <span class="hlt">Wind</span> <span class="hlt">speed</span> is sensed electro-optically to provide data of <span class="hlt">wind</span> <span class="hlt">speed</span> upwind of the propeller, to thereby permit tip <span class="hlt">speed</span> ratio circuitry to operate the power control circuitry and thereby optimize the tip <span class="hlt">speed</span> ratio by varying the loading of the propeller. Accordingly, the efficiency of the <span class="hlt">wind</span> energy conversion system is maximized.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19890009894','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19890009894"><span><span class="hlt">Wind</span>-Tunnel Results of Advanced High-<span class="hlt">Speed</span> Propellers at Takeoff, Climb, and Landing Mach Numbers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Stefko, George L.; Jeracki, Robert J.</p> <p>1985-01-01</p> <p>Low-<span class="hlt">speed</span> <span class="hlt">wind</span>-tunnel performance tests of two advanced propellers have been completed at the NASA Lewis Research Center as part of the NASA Advanced Turboprop Program. The 62.2 cm (24.5 in.) diameter adjustable-pitch models were tested at Mach numbers typical of takeoff, initial climbout, and landing <span class="hlt">speeds</span> (i.e., from Mach 0.10 to 0.34) at zero angle of attack in the NASA Lewis 10 by 10 Foot Supersonic <span class="hlt">Wind</span> Tunnel. Both models had eight blades and a cruise-design-point operating condition of Mach 0.80, and 10.668 km (35,000 ft) I.S.A. altitude, a 243.8 m/s (800 ft/sec) tip <span class="hlt">speed</span>, and a high power loading of 301 kW/sq m (37.5 shp/sq ft). Each model had its own integrally designed area-ruled spinner, but used the same specially contoured nacelle. These features reduced blade-section Mach numbers and relieved blade-root choking at the cruise condition. No adverse or unusual low-<span class="hlt">speed</span> operating conditions were found during the test with either the straight blade SR-2 or the 45 deg swept SR-3 propeller. Typical efficiencies of the straight and 45 deg swept propellers were 50.2 and 54.9 percent, respectively, at a takeoff condition of Mach 0.20 and 53.7 and 59.1 percent, respectively, at a climb condition of Mach 0.34.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <div class="footer-extlink text-muted" style="margin-bottom:1rem; text-align:center;">Some links on this page may take you to non-federal websites. 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