WorldWideScience

Sample records for wind meridional velocity

  1. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  2. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  3. Wind Diffusivity Current, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  4. Wind Diffusivity Current, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  5. Magnetohydrdodynamic models of coronal transients in the meridional plane. IV. effect of the solar wind

    International Nuclear Information System (INIS)

    Wu, S.T.; Steinolfson, R.S.; Dryer, M.; Tandberg-Hanssen, E.

    1981-01-01

    A two-dimensional, time-dependenct magnetohydrodynamic model in the meridional plane with and without an ambient solar wind in an ambient radial magnetic field has been used to investigate mass motions associated with coronal transients. We show that that solar wind does not significantly affect the general dynamic characteristics of the mass motion. The ambient solar wind, however, increases the velocity of the mass motion and produces a moderate change in the thermodynamic properties of the coronal plasma

  6. Equinoctial asymmetry of a low-latitude ionosphere-thermosphere system and equatorial irregularities: evidence for meridional wind control

    Directory of Open Access Journals (Sweden)

    T. Maruyama

    2009-05-01

    Full Text Available Nocturnal ionospheric height variations were analyzed along the meridian of 100° E by using ionosonde data. Two ionosondes were installed near the magnetic conjugate points at low latitudes, and the third station was situated near the magnetic equator. Ionospheric virtual heights were scaled every 15 min and vertical E×B drift velocities were inferred from the equatorial station. By incorporating the inferred equatorial vertical drift velocity, ionospheric bottom heights with the absence of wind were modeled for the two low-latitude conjugate stations, and the deviation in heights from the model outputs was used to infer the transequatorial meridional thermospheric winds. The results obtained for the September and March equinoxes of years 2004 and 2005, respectively, were compared, and a significant difference in the meridional wind was found. An oscillation with a period of approximately 7 h of the meridional wind existed in both the equinoxes, but its amplitude was larger in September as compared to that in March. When the equatorial height reached the maximum level due to the evening enhancement of the zonal electric field, the transequatorial meridional wind velocity reached approximately 10 and 40 m/s for the March and September equinoxes, respectively. This asymmetry of the ionosphere-thermosphere system was found to be associated with the previously reported equinoctial asymmetry of equatorial ionospheric irregularities; the probability for equatorial irregularities to occur is higher in March as compared to that in September at the Indian to Western Pacific longitudes. Numerical simulations of plasma bubble developments were conducted by incorporating the transequatorial neutral wind effect, and the results showed that the growth time (e-folding time of the bubble was halved when the wind velocity changed from 10 to 40 m/s.

  7. Upgrading the Arecibo Potassium Lidar Receiver for Meridional Wind Measurements

    Science.gov (United States)

    Piccone, A. N.; Lautenbach, J.

    2017-12-01

    Lidar can be used to measure a plethora of variables: temperature, density of metals, and wind. This REU project is focused on the set up of a semi steerable telescope that will allow the measurement of meridional wind in the mesosphere (80-105 km) with Arecibo Observatory's potassium resonance lidar. This includes the basic design concept of a steering system that is able to turn the telescope to a maximum of 40°, alignment of the mirror with the telescope frame to find the correct focusing, and the triggering and programming of a CCD camera. The CCD camera's purpose is twofold: looking though the telescope and matching the stars in the field of view with a star map to accurately calibrate the steering system and determining the laser beam properties and position. Using LabVIEW, the frames from the CCD camera can be analyzed to identify the most intense pixel in the image (and therefore the brightest point in the laser beam or stars) by plotting average pixel values per row and column and locating the peaks of these plots. The location of this pixel can then be plotted, determining the jitter in the laser and position within the field of view of the telescope.

  8. Wind, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Remote Sensing Inc. distributes science quality wind velocity data from the SeaWinds instrument onboard NASA's QuikSCAT satellite. SeaWinds is a microwave...

  9. Intra-seasonal Oscillations (ISO of zonal-mean meridional winds and temperatures as measured by UARS

    Directory of Open Access Journals (Sweden)

    F. T. Huang

    2005-06-01

    Full Text Available Based on an empirical analysis of measurements with the High Resolution Doppler Imager (HRDI on the UARS spacecraft in the upper mesosphere (95km, 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 on an analysis of concurrent UARS temperature measurements, which produces oscillations similar to those seen in the meridional winds. Although the temperature oscillations are observed at lower altitudes (55km, 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.

  10. Wind, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind divergence data originating with wind velocity measurements from the ASCAT instrument onboard EUMETSAT's ASCAT...

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

    Science.gov (United States)

    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.

  12. A seasonal study on the role of h'F/meridional winds in influencing the development of ESF irregularities over Indian sector

    Science.gov (United States)

    Sreekumar, Sreeba; Sripathi, S.

    2017-08-01

    In this paper, we present the seasonal variation of nighttime thermospheric meridional winds over Hyderabad as derived using dual ionosonde observations located at Tirunelveli (8.7°N, 77.7°E, Dip Lat = 0.3°N), an equatorial station and Hyderabad (17.38°N, 78.45°E, Dip Lat = 12°N), a low latitude station, respectively, over the period of April-December 2013 using h'F data as discussed in (Sreekumar and Sripathi, 2016). The calculated winds has been compared with HWM14 wind model. The results show that trends of the derived winds from the ionosonde h'F data matches well with model wind near to midnight hours in all the seasons. However, some dissimilarities were observed during early night hours. Especially, the poleward winds during early night hours for different seasons were not well reproduced by the model. Later, the study is extended to understand the role of meridional winds in causing the variability of ESF occurrence vis a vis h'F. The histogram analysis of h'F vs wind values just before ESF onset reveals that the most probable combination of wind and h'F on the ESF days are centered around 350 km and 50 m/s. Additionally, we also performed Superposed Epoch Analysis (SEA) based on longer and shorter duration ESF events. The analysis reveals the distinct differences in the longer and shorter duration ESF events of Summer and Autumn equinox where the values of h'F as well as meridional winds where such that a steep change in reduction of poleward winds prior to ESF onset supported the longer duration ESF events in both seasons. However, this steep reduction is not so significant for the shorter duration ESF events indicating that meridional winds could play a crucial role in extending the spread F durations in longer duration events. The observations clearly demonstrate the reduction of poleward wind velocities during vernal equinox as compared to Autumn equinox, where larger poleward winds were present around ESF onset times. These observations are

  13. Influence of glacial ice sheets on the Atlantic meridional overturning circulation through surface wind change

    Science.gov (United States)

    Sherriff-Tadano, Sam; Abe-Ouchi, Ayako; Yoshimori, Masakazu; Oka, Akira; Chan, Wing-Le

    2018-04-01

    Coupled modeling studies have recently shown that the existence of the glacial ice sheets intensifies the Atlantic meridional overturning circulation (AMOC). However, most models show a strong AMOC in their simulations of the Last Glacial Maximum (LGM), which is biased compared to reconstructions that indicate both a weaker and stronger AMOC during the LGM. Therefore, a detailed investigation of the mechanism behind this intensification of the AMOC is important for a better understanding of the glacial climate and the LGM AMOC. Here, various numerical simulations are conducted to focus on the effect of wind changes due to glacial ice sheets on the AMOC and the crucial region where the wind modifies the AMOC. First, from atmospheric general circulation model experiments, the effect of glacial ice sheets on the surface wind is evaluated. Second, from ocean general circulation model experiments, the influence of the wind stress change on the AMOC is evaluated by applying wind stress anomalies regionally or at different magnitudes as a boundary condition. These experiments demonstrate that glacial ice sheets intensify the AMOC through an increase in the wind stress at the North Atlantic mid-latitudes, which is induced by the North American ice sheet. This intensification of the AMOC is caused by the increased oceanic horizontal and vertical transport of salt, while the change in sea ice transport has an opposite, though minor, effect. Experiments further show that the Eurasian ice sheet intensifies the AMOC by directly affecting the deep-water formation in the Norwegian Sea.

  14. Effects of Southern Hemisphere Wind Changes on the Meridional Overturning Circulation in Ocean Models.

    Science.gov (United States)

    Gent, Peter R

    2016-01-01

    Observations show that the Southern Hemisphere zonal wind stress maximum has increased significantly over the past 30 years. Eddy-resolving ocean models show that the resulting increase in the Southern Ocean mean flow meridional overturning circulation (MOC) is partially compensated by an increase in the eddy MOC. This effect can be reproduced in the non-eddy-resolving ocean component of a climate model, providing the eddy parameterization coefficient is variable and not a constant. If the coefficient is a constant, then the Southern Ocean mean MOC change is balanced by an unrealistically large change in the Atlantic Ocean MOC. Southern Ocean eddy compensation means that Southern Hemisphere winds cannot be the dominant mechanism driving midlatitude North Atlantic MOC variability.

  15. Solar wind velocity and geomagnetic moment variations

    International Nuclear Information System (INIS)

    Kalinin, Yu.D.; Rozanova, T.S.

    1982-01-01

    The mean year values of the solar wind velocity have been calculated from the mean-year values of a geomagnetic activity index am according to the Svalgard equation of regression for the pe-- riod from 1930 to 1960. For the same years the values of the geomagnetic moment M and separately of its ''inner'' (causes of which'' are inside the Earth) and ''external'' (causes of which are outside the Earth) parts have been calculated from the mean year data of 12 magnetic observatories. The proof of the presence of the 11-year variation in the moment M has been obtained. It is concluded that the 11-year variations in M result from the variations of the solar wind velocity

  16. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  17. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  18. Wind Stress, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Curl

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  19. CHANGES OF THE SOLAR MERIDIONAL VELOCITY PROFILE DURING CYCLE 23 EXPLAINED BY FLOWS TOWARD THE ACTIVITY BELTS

    International Nuclear Information System (INIS)

    Cameron, R. H.; Schuessler, M.

    2010-01-01

    The solar meridional flow is an important ingredient in Babcock-Leighton type models of the solar dynamo. Global variations of this flow have been suggested to explain the variations in the amplitudes and lengths of the activity cycles. Recently, cycle-related variations in the amplitude of the P 1 2 term in the Legendre decomposition of the observed meridional flow have been reported. The result is often interpreted in terms of an overall variation in the flow amplitude during the activity cycle. Using a semi-empirical model based upon the observed distribution of magnetic flux on the solar surface, we show that the reported variations of the P 1 2 term can be explained by the observed localized inflows into the active region belts. No variation of the overall meridional flow amplitude is required.

  20. Meridional transport of magnetic flux in the solar wind between 1 and 10 AU: a theoretical analysis

    International Nuclear Information System (INIS)

    Pizzo, V.J.; Goldstein, B.E.

    1987-01-01

    Pioneer 10 observations suggest that the mean (longitudinally averaged) solar wind azimuthal field strength, B/sub phi/, near the ecliptic plane falls off more rapidly with heliocentric distance than would be expected in a classic Parker expansion, showing a deficit of 10--20% (as compared to the projected 1-AU value) by 10 AU. Though this observational interpretation has been challenged by subsequent analyses of Voyager data, it has nevertheless stimulated efforts to explain the inferred deficit on the basis of systematic north-south magnetic pressure gradients generated by the differential spiral wrapping of magnetic field lines in interplanetary space. We reexamine this issue from the theoretical perspective using a three-dimensional MHD nonlinear numerical model for steady, corotating flow. For realistic solar wind parameters we find that a purely axisymmetric expansion is capable of producing sizable magnetic flux deficits only when there are substantial meridional gradients in mean flow conditions localized about the ecliptic plane near the sun. Even then the match between plausible flow states and significant mean B/sub phi/ deficit is achieved over such a limited parameter range that it is unlikely this mechanism alone can produce deficits of the magnitude inferred from the Pioneer data

  1. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Curl

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  2. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  3. Wind Stress, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind stress data in zonal, meridional, modulus, and wind stress curl sets. This data begins with wind velocity...

  4. Wind Velocity Vertical Extrapolation by Extended Power Law

    Directory of Open Access Journals (Sweden)

    Zekai Şen

    2012-01-01

    Full Text Available Wind energy gains more attention day by day as one of the clean renewable energy resources. We predicted wind speed vertical extrapolation by using extended power law. In this study, an extended vertical wind velocity extrapolation formulation is derived on the basis of perturbation theory by considering power law and Weibull wind speed probability distribution function. In the proposed methodology not only the mean values of the wind speeds at different elevations but also their standard deviations and the cross-correlation coefficient between different elevations are taken into consideration. The application of the presented methodology is performed for wind speed measurements at Karaburun/Istanbul, Turkey. At this location, hourly wind speed measurements are available for three different heights above the earth surface.

  5. Results of verification and investigation of wind velocity field forecast. Verification of wind velocity field forecast model

    International Nuclear Information System (INIS)

    Ogawa, Takeshi; Kayano, Mitsunaga; Kikuchi, Hideo; Abe, Takeo; Saga, Kyoji

    1995-01-01

    In Environmental Radioactivity Research Institute, the verification and investigation of the wind velocity field forecast model 'EXPRESS-1' have been carried out since 1991. In fiscal year 1994, as the general analysis, the validity of weather observation data, the local features of wind field, and the validity of the positions of monitoring stations were investigated. The EXPRESS which adopted 500 m mesh so far was improved to 250 m mesh, and the heightening of forecast accuracy was examined, and the comparison with another wind velocity field forecast model 'SPEEDI' was carried out. As the results, there are the places where the correlation with other points of measurement is high and low, and it was found that for the forecast of wind velocity field, by excluding the data of the points with low correlation or installing simplified observation stations to take their data in, the forecast accuracy is improved. The outline of the investigation, the general analysis of weather observation data and the improvements of wind velocity field forecast model and forecast accuracy are reported. (K.I.)

  6. Effects of increasing tip velocity on wind turbine rotor design.

    Energy Technology Data Exchange (ETDEWEB)

    Resor, Brian Ray [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Maniaci, David Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Berg, Jonathan Charles [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Richards, Phillip William [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2014-05-01

    A reduction in cost of energy from wind is anticipated when maximum allowable tip velocity is allowed to increase. Rotor torque decreases as tip velocity increases and rotor size and power rating are held constant. Reduction in rotor torque yields a lighter weight gearbox, a decrease in the turbine cost, and an increase in the capacity for the turbine to deliver cost competitive electricity. The high speed rotor incurs costs attributable to rotor aero-acoustics and system loads. The increased loads of high speed rotors drive the sizing and cost of other components in the system. Rotor, drivetrain, and tower designs at 80 m/s maximum tip velocity and 100 m/s maximum tip velocity are created to quantify these effects. Component costs, annualized energy production, and cost of energy are computed for each design to quantify the change in overall cost of energy resulting from the increase in turbine tip velocity. High fidelity physics based models rather than cost and scaling models are used to perform the work. Results provide a quantitative assessment of anticipated costs and benefits for high speed rotors. Finally, important lessons regarding full system optimization of wind turbines are documented.

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

    Science.gov (United States)

    2015-04-29

    SECURITY CLASSIFICATION OF: Funds were provided by the ARO for the purchase of TSI hot-wire anemometer equipment and a Dantec particle- image...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...Funds were provided by the Army Research Office for the purchase of TSI hot-wire anemometer equipment and a Dantec particle-image velocimetry system

  8. A method for measuring mean wind velocities in a canyon with tracer balloons

    Science.gov (United States)

    Sheih, C. M.; Billman, B. J.; Depaul, F. T.

    1985-08-01

    A method using balloons as tracers for measuring mean wind velocity in street canyons or mountain valleys has been developed. Tests of the method with numerical experiments showed that the method reproduced an assumed wind field quite well provided that the buoyancy component of the balloon velocity was larger than the downward velocity component of the wind. Tests of the method with measurements of wind velocity in a street canyon of downtown Chicago showed that the method yielded flow patterns quite similar to photographic results of flow visualization of phisical simulations by other investigators. However, no direct measurements of wind velocity were available for quantitative comparison.

  9. Characteristics of Wind Velocity and Temperature Change Near an Escarpment-Shaped Road Embankment

    Directory of Open Access Journals (Sweden)

    Young-Moon Kim

    2014-01-01

    Full Text Available Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small.

  10. Characteristics of Wind Velocity and Temperature Change Near an Escarpment-Shaped Road Embankment

    Science.gov (United States)

    Kim, Young-Moon; You, Ki-Pyo; You, Jang-Youl

    2014-01-01

    Artificial structures such as embankments built during the construction of highways influence the surrounding airflow. Various types of damage can occur due to changes in the wind velocity and temperature around highway embankments. However, no study has accurately measured micrometeorological changes (wind velocity and temperature) due to embankments. This study conducted a wind tunnel test and field measurement to identify changes in wind velocity and temperature before and after the construction of embankments around roads. Changes in wind velocity around an embankment after its construction were found to be influenced by the surrounding wind velocity, wind angle, and the level difference and distance from the embankment. When the level difference from the embankment was large and the distance was up to 3H, the degree of wind velocity declines was found to be large. In changes in reference wind velocities around the embankment, wind velocity increases were not proportional to the rate at which wind velocities declined. The construction of the embankment influenced surrounding temperatures. The degree of temperature change was large in locations with large level differences from the embankment at daybreak and during evening hours when wind velocity changes were small. PMID:25136681

  11. Wind Diffusivity Current, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  12. Wind Diffusivity Current, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  13. The Effect of Wind Velocity on the Cooling Rate of Water

    OpenAIRE

    Shrey Aryan

    2016-01-01

    The effect of wind velocity on the cooling rate of water was investigated by blowing air horizontally over the surface of water contained in a plastic water-bottle cap. The time taken for the temperature to fall to the average of the surrounding and initial temperatures was recorded at different values of wind velocity. It was observed that on increasing the wind velocity, the time taken to achieve average temperature not only decreased but also remained the same after a certain point.

  14. Wind Diffusivity Current, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  15. Ekman Upwelling, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes science quality Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  16. Wind Diffusivity Current, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  17. Semiconductor Laser Lidar Wind Velocity Sensor for Turbine Control

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Hu, Qi; Pedersen, Christian

    2014-01-01

    A dual line-of-sight CW lidar that measures both wind speed and direction is presented . The wind lidar employs a semiconductor laser, which allows for inexpensive remote sensors geared towards enhanced control of wind turbines .......A dual line-of-sight CW lidar that measures both wind speed and direction is presented . The wind lidar employs a semiconductor laser, which allows for inexpensive remote sensors geared towards enhanced control of wind turbines ....

  18. Intraseasonal meridional current variability in the eastern equatorial Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ogata, T.; Sasaki, H.; Murty, V.S.N.; Sarma, M.S.S.; Masumoto, Y.

    values of the Mixed Rossby-gravity wave at 15-d period. This meridional current variability shows large coherence with the local meridional wind stress, suggesting the upper-ocean responses to the local wind-forcing. A part of the energy of the biweekly...

  19. A Model for Determining the Effect of the Wind Velocity on 100 M Sprinting Performance

    Directory of Open Access Journals (Sweden)

    Janjic Natasa

    2017-06-01

    Full Text Available This paper introduces an equation for determining instantaneous and final velocity of a sprinter in a 100 m run completed with a wind resistance ranging from 0.1 to 4.5 m/s. The validity of the equation was verified using the data of three world class sprinters: Carl Lewis, Maurice Green, and Usain Bolt. For the given constant wind velocity with the values + 0.9 and + 1.1 m/s, the wind contribution to the change of sprinter velocity was the same for the maximum as well as for the final velocity. This study assessed how the effect of the wind velocity influenced the change of sprinting velocity. The analysis led to the conclusion that the official limit of safely neglecting the wind influence could be chosen as 1 m/s instead of 2 m/s, if the velocity were presented using three, instead of two decimal digits. This implies that wind velocity should be rounded off to two decimal places instead of the present practice of one decimal place. In particular, the results indicated that the influence of wind on the change of sprinting velocity in the range of up to 2 m/s and was of order of magnitude of 10-3 m/s. This proves that the IAAF Competition Rules correctly neglect the influence of the wind with regard to such velocities. However, for the wind velocity over 2 m/s, the wind influence is of order 10-2 m/s and cannot be neglected.

  20. Wind-induced flow velocity effects on nutrient concentrations at Eastern Bay of Lake Taihu, China.

    Science.gov (United States)

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Jianwei; Gao, Xiaomeng; Wang, Wencai; Acharya, Kumud

    2017-07-01

    Shallow lakes are highly sensitive to respond internal nutrient loading due to wind-induced flow velocity effects. Wind-induced flow velocity effects on nutrient suspension were investigated at a long narrow bay of large shallow Lake Taihu, the third largest freshwater lake in China. Wind-induced reverse/compensation flow and consistent flow field probabilities at vertical column of the water were measured. The probabilities between the wind field and the flow velocities provided a strong correlation at the surface (80.6%) and the bottom (65.1%) layers of water profile. Vertical flow velocity profile analysis provided the evidence of delay response time to wind field at the bottom layer of lake water. Strong wind field generated by the west (W) and west-north-west (WNW) winds produced displaced water movements in opposite directions to the prevailing flow field. An exponential correlation was observed between the current velocities of the surface and the bottom layers while considering wind speed as a control factor. A linear model was developed to correlate the wind field-induced flow velocity impacts on nutrient concentration at the surface and bottom layers. Results showed that dominant wind directions (ENE, E, and ESE) had a maximum nutrient resuspension contribution (nutrient resuspension potential) of 34.7 and 43.6% at the surface and the bottom profile layers, respectively. Total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP) average concentrations were 6.38, 1.5, and 0.03 mg/L during our field experiment at Eastern Bay of Lake Taihu. Overall, wind-induced low-to-moderate hydrodynamic disturbances contributed more in nutrient resuspension at Eastern Bay of Lake Taihu. The present study can be used to understand the linkage between wind-induced flow velocities and nutrient concentrations for shallow lakes (with uniform morphology and deep margins) water quality management and to develop further models.

  1. The Effect of Wind Velocity on the Cooling Rate of Water

    Directory of Open Access Journals (Sweden)

    Shrey Aryan

    2016-01-01

    Full Text Available The effect of wind velocity on the cooling rate of water was investigated by blowing air horizontally over the surface of water contained in a plastic water-bottle cap. The time taken for the temperature to fall to the average of the surrounding and initial temperatures was recorded at different values of wind velocity. It was observed that on increasing the wind velocity, the time taken to achieve average temperature not only decreased but also remained the same after a certain point.

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

    Directory of Open Access Journals (Sweden)

    B. Bavassano

    2009-02-01

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

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

    Directory of Open Access Journals (Sweden)

    B. Bavassano

    2009-02-01

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

  4. MEASUREMENT OF MOTION CORRECTED WIND VELOCITY USING AN AEROSTAT LOFTED SONIC ANEMOMETER

    Science.gov (United States)

    An aerostat-lofted, sonic anemometer was used to determine instantaneous 3 dimensional wind velocities at altitudes relevant to fire plume dispersion modeling. An integrated GPS, inertial measurement unit, and attitude heading and reference system corrected the wind data for th...

  5. Characterization of wind velocities in the wake of a full scale wind turbine using three ground-based synchronized WindScanners

    DEFF Research Database (Denmark)

    Yazicioglu, Hasan; Angelou, Nikolas; Mikkelsen, Torben Krogh

    2016-01-01

    , installed at Risoe test field, has been measured from 0 to 2 diameters downstream. For this, three ground-based synchronised short-range WindScanners and a spinner lidar have been used. The 3D wind velocity field has been reconstructed in horizontal and vertical planes crossing the hub. The 10-min mean...

  6. Solar wind velocity and daily variation of cosmic rays

    International Nuclear Information System (INIS)

    Ahluwalia, H.S.; Riker, J.F.

    1985-01-01

    Recently parameters applicable to the solar wind and the interplanetary magnetic field (IMF) have become much better defined. Superior quality of data bases that are now available, particularly for the post-1971 period, make it possible to believe the long-term trends in the data. These data are correlated with the secular changes observed in the diurnal variation parameters obtained from neutron monitor data at Deep River and underground muon telescope data at Embudo (30 MEW) and Socorro (82 MWE). The annual mean amplitudes appear to have large values during the epochs of high speed solar wind streams. Results are discussed

  7. Characterization of wind velocities in the upstream induction zone of a wind turbine using scanning continuous-wave lidars

    DEFF Research Database (Denmark)

    Simley, Eric; Angelou, Nikolas; Mikkelsen, Torben Krogh

    2016-01-01

    9% and 3% of the freestream longitudinal wind speed were measured for the abovementioned high and low CP values, respectively. Turbulence statistics, calculated using 2.5-min time series, suggest that the standard deviation of the longitudinal wind component decreases close to the rotor, while...... Technical University’s Risø campus is investigated using a scanning Light Detection and Ranging (lidar) system. Three short-range continuous-wave “WindScanner” lidars are positioned in the field around the V27 turbine allowing detection of all three components of the wind velocity vectors within...... the induction zone. The time-averaged mean wind speeds at different locations in the upstream induction zone are measured by scanning a horizontal plane at hub height and a vertical plane centered at the middle of the rotor extending roughly 1.5 rotor diameters (D) upstream of the rotor. Turbulence statistics...

  8. Improved velocity law parameterization for hot star winds (Research Note)

    Czech Academy of Sciences Publication Activity Database

    Krtička, J.; Kubát, Jiří

    2011-01-01

    Roč. 534, October (2011), A97/1-A97/3 ISSN 0004-6361 R&D Projects: GA ČR GA205/08/0003 Institutional research plan: CEZ:AV0Z10030501 Keywords : stars * winds * outflows Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.587, year: 2011

  9. Artificial neural network approach to spatial estimation of wind velocity data

    International Nuclear Information System (INIS)

    Oztopal, Ahmet

    2006-01-01

    In any regional wind energy assessment, equal wind velocity or energy lines provide a common basis for meaningful interpretations that furnish essential information for proper design purposes. In order to achieve regional variation descriptions, there are methods of optimum interpolation with classical weighting functions or variogram methods in Kriging methodology. Generally, the weighting functions are logically and geometrically deduced in a deterministic manner, and hence, they are imaginary first approximations for regional variability assessments, such as wind velocity. Geometrical weighting functions are necessary for regional estimation of the regional variable at a location with no measurement, which is referred to as the pivot station from the measurements of a set of surrounding stations. In this paper, weighting factors of surrounding stations necessary for the prediction of a pivot station are presented by an artificial neural network (ANN) technique. The wind speed prediction results are compared with measured values at a pivot station. Daily wind velocity measurements in the Marmara region from 1993 to 1997 are considered for application of the ANN methodology. The model is more appropriate for winter period daily wind velocities, which are significant for energy generation in the study area. Trigonometric point cumulative semivariogram (TPCSV) approach results are compared with the ANN estimations for the same set of data by considering the correlation coefficient (R). Under and over estimation problems in objective analysis can be avoided by the ANN approach

  10. Ocean Ekman Response to Wind Forcing in Frontal Regions and Implications for Vertical Velocity

    Science.gov (United States)

    Cronin, M. F.; Tozuka, T.

    2016-12-01

    Wind forcing is fundamental to the ocean circulation. According to the classic "Ekman" theory developed in the early twentieth century, wind-induced steady flow spirals to the right of the wind stress in the Northern Hemisphere and to the left in the Southern Hemisphere, resulting in a net wind-forced "Ekman" transport that is 90 degrees to the right of the wind stress in the Northern Hemisphere and to the left in the Southern Hemisphere. This theory, however, assumes that the near-surface ocean is uniform in density (i.e., has no fronts). In frontal regions the surface "geostrophic" currents have a vertical shear aligned with the density front and this oceanic "thermal wind" shear can balance a portion of the surface wind stress. In this study we show that in frontal regions, the classic Ekman response is altered. Surface ocean currents respond to the effective wind stress—the portion of the wind stress that is out of balance with the ocean's surface geostrophic shear. Consequently, the vertical velocity at the base of the mixed layer is better approximated by the curl of the effective wind stress, rather than the full wind stress. Wind blowing along a front can give rise to a local minimum in the effective wind stress and result in a secondary circulation with downwelling on the cold side of the front and upwelling on the warm side. Using data from the high-resolution Japanese Ocean general circulation model For the Earth Simulator (OFES), we show that these frontal effects cannot be ignored in the Tropics or in strong frontal regions in the extratropics, such as found in coastal regions and in western boundary currents of all basins. Furthermore, these frontal effects dominate the classic Ekman response in regions of both hemispheres where trade winds change to westerlies.

  11. Effect of Wind Velocity on Flame Spread in Microgravity

    Science.gov (United States)

    Prasad, Kuldeep; Olson, Sandra L.; Nakamura, Yuji; Fujita, Osamu; Nishizawa, Katsuhiro; Ito, Kenichi; Kashiwagi, Takashi; Simons, Stephen N. (Technical Monitor)

    2002-01-01

    A three-dimensional, time-dependent model is developed describing ignition and subsequent transition to flame spread over a thermally thin cellulosic sheet heated by external radiation in a microgravity environment. A low Mach number approximation to the Navier Stokes equations with global reaction rate equations describing combustion in the gas phase and the condensed phase is numerically solved. The effects of a slow external wind (1-20 cm/s) on flame transition are studied in an atmosphere of 35% oxygen concentration. The ignition is initiated at the center part of the sample by generating a line-shape flame along the width of the sample. The calculated results are compared with data obtained in the 10s drop tower. Numerical results exhibit flame quenching at a wind speed of 1.0 cm/s, two localized flames propagating upstream along the sample edges at 1.5 cm/s, a single line-shape flame front at 5.0 cm/s, three flames structure observed at 10.0 cm/s (consisting of a single line-shape flame propagating upstream and two localized flames propagating downstream along sample edges) and followed by two line-shape flames (one propagating upstream and another propagating downstream) at 20.0 cm/s. These observations qualitatively compare with experimental data. Three-dimensional visualization of the observed flame complex, fuel concentration contours, oxygen and reaction rate isosurfaces, convective and diffusive mass flux are used to obtain a detailed understanding of the controlling mechanism, Physical arguments based on lateral diffusive flux of oxygen, fuel depletion, oxygen shadow of the flame and heat release rate are constructed to explain the various observed flame shapes.

  12. Analysis of wind velocity and release angle effects on discus throw using computational fluid dynamics.

    Science.gov (United States)

    Rouboa, Abel I; Reis, Victor M; Mantha, Vishveshwar R; Marinho, Daniel A; Silva, António J

    2013-01-01

    The aim of this paper is to study the aerodynamics of discus throw. A comparison of numerical and experimental performance of discus throw with and without rotation was carried out using the analysis of lift and drag coefficients. Initial velocity corresponding to variation angle of around 35.5° was simulated. Boundary condition, on the top and bottom boundary edges of computational domain, was imposed in order to eliminate external influences on the discus; a wind resistance was calculated for the velocity values of 25 and 27 m/s. The results indicate that the flight distance (D) was strongly affected by the drag coefficient, the initial velocity, the release angle and the direction of wind velocity. It was observed that these variables change as a function of discus rotation. In this study, results indicate a good agreement of D between experimental values and numerical results.

  13. On a relation of geomagnetic activity, solar wind velocity and irregularity of daily rotation of the Earth

    International Nuclear Information System (INIS)

    Kalinin, Yu.D.; Kiselev, V.M.

    1980-01-01

    A possibility of the presence of statistic relation between the changes of the Earth rotation regime and the mean velocity of solar wind is discussed. The ratio between the solar wind velocity observed and planetary index of geomagnetic activity am is used to determine the annual average values of solar wind velocity beyond the twentieth cycle of solar activity. The restored changes of solar wind velocity are compared with solar conditioned variations of the Earth day duration and it is shown that the correspondence takes place only at frequencies lower the frequency of 11-year cycle [ru

  14. Analysis and forecasting of wind velocity in chetumal, quintana roo, using the single exponential smoothing method

    Energy Technology Data Exchange (ETDEWEB)

    Cadenas, E. [Facultad de Ingenieria Mecanica, Universidad Michoacana de San Nicolas de Hidalgo, Santiago Tapia No. 403, Centro (Mexico); Jaramillo, O.A.; Rivera, W. [Centro de Ivestigacion en Energia, Universidad Nacional Autonoma de Mexico, Apartado Postal 34, Temixco 62580, Morelos (Mexico)

    2010-05-15

    In this paper the analysis and forecasting of wind velocities in Chetumal, Quintana Roo, Mexico is presented. Measurements were made by the Instituto de Investigaciones Electricas (IIE) during two years, from 2004 to 2005. This location exemplifies the wind energy generation potential in the Caribbean coast of Mexico that could be employed in the hotel industry in the next decade. The wind speed and wind direction were measured at 10 m above ground level. Sensors with high accuracy and a low starting threshold were used. The wind velocity was recorded using a data acquisition system supplied by a 10 W photovoltaic panel. The wind speed values were measured with a frequency of 1 Hz and the average wind speed was recorded considering regular intervals of 10 min. First a statistical analysis of the time series was made in the first part of the paper through conventional and robust measures. Also the forecasting of the last day of measurements was made utilizing the single exponential smoothing method (SES). The results showed a very good accuracy of the data with this technique for an {alpha} value of 0.9. Finally the SES method was compared with the artificial neural network (ANN) method showing the former better results. (author)

  15. Filament formation in wind-cloud interactions- II. Clouds with turbulent density, velocity, and magnetic fields

    Science.gov (United States)

    Banda-Barragán, W. E.; Federrath, C.; Crocker, R. M.; Bicknell, G. V.

    2018-01-01

    We present a set of numerical experiments designed to systematically investigate how turbulence and magnetic fields influence the morphology, energetics, and dynamics of filaments produced in wind-cloud interactions. We cover 3D, magnetohydrodynamic systems of supersonic winds impacting clouds with turbulent density, velocity, and magnetic fields. We find that lognormal density distributions aid shock propagation through clouds, increasing their velocity dispersion and producing filaments with expanded cross-sections and highly magnetized knots and subfilaments. In self-consistently turbulent scenarios, the ratio of filament to initial cloud magnetic energy densities is ∼1. The effect of Gaussian velocity fields is bound to the turbulence Mach number: Supersonic velocities trigger a rapid cloud expansion; subsonic velocities only have a minor impact. The role of turbulent magnetic fields depends on their tension and is similar to the effect of radiative losses: the stronger the magnetic field or the softer the gas equation of state, the greater the magnetic shielding at wind-filament interfaces and the suppression of Kelvin-Helmholtz instabilities. Overall, we show that including turbulence and magnetic fields is crucial to understanding cold gas entrainment in multiphase winds. While cloud porosity and supersonic turbulence enhance the acceleration of clouds, magnetic shielding protects them from ablation and causes Rayleigh-Taylor-driven subfilamentation. Wind-swept clouds in turbulent models reach distances ∼15-20 times their core radius and acquire bulk speeds ∼0.3-0.4 of the wind speed in one cloud-crushing time, which are three times larger than in non-turbulent models. In all simulations, the ratio of turbulent magnetic to kinetic energy densities asymptotes at ∼0.1-0.4, and convergence of all relevant dynamical properties requires at least 64 cells per cloud radius.

  16. Sensitivity of stand transpiration to wind velocity in a mixed broadleaved deciduous forest

    Science.gov (United States)

    Dohyoung Kim; Ram Oren; A. Christopher Oishi; Cheng-I Hsieh; Nathan Phillips; Kimberly A. Novick; Paul C. Stoy

    2014-01-01

    Wind velocity (U) within and above forest canopies can alter the coupling between the vapor-saturated sub-stomatal airspace and the drier atmosphere aloft, thereby influencing transpiration rates. In practice, however, the actual increase in transpiration with increasing U depends on the aerodynamic resistance (RA) to vapor transfer compared to canopy resistance to...

  17. Passive A-band Wind Sounder (PAWS) for measuring tropospheric wind velocity profile

    Science.gov (United States)

    Miecznik, Grzegorz; Pierce, Robert; Huang, Pei; Slaymaker, Philip A.; Kaptchen, Paul; Roark, Shane; Johnson, Brian R.; Heath, Donald F.

    2007-09-01

    The Passive A-Band Wind Sounder (PAWS) was funded through NASA's Instrument Incubator Program (IIP) to determine the feasibility of measuring tropospheric wind speed profiles from Doppler shifts in absorption O II A-band. It is being pursued as a low-cost and low-risk alternative capable of providing better wind data than is currently available. The instrument concept is adapted from the Wind Imaging Interferometer (WINDII) sensor on the Upper Atmosphere Research Satellite. The operational concept for PAWS is to view an atmospheric limb over an altitude range from the surface to 20 km with a Doppler interferometer in a sun-synchronous low-earth orbit. Two orthogonal views of the same sampling volume will be used to resolve horizontal winds from measured line-of-sight winds. A breadboard instrument was developed to demonstrate the measurement approach and to optimize the design parameters for the subsequent engineering unit and future flight sensor. The breadboard instrument consists of a telescope, collimator, filter assembly, and Michelson interferometer. The instrument design is guided by a retrieval model, which helps to optimize key parameters, spectral filter and optical path difference in particular.

  18. Computerized system for building 'the rose' of the winds and defining the velocity and the average density of the wind power for a given place

    International Nuclear Information System (INIS)

    Valkov, I.; Dekova, I.; Arnaudov, A.; Kostadinov, A.

    2002-01-01

    This paper considers the structure and the working principle of a computerized system for building 'the rose' of the winds. The behaviour of the system has been experimentally investigated and on the basis of the received data 'the rose' of the winds has been built, a diagram of the average wind velocity at a predefined step in the course of time has been made, and the average density of the wind power has been quantitatively defined. The proposed system enables possibilities for creating a data base of wind parameters, their processing and graphical visualizing of the received results. The system allows to improve the work of devices of wild's wind gauge type. (authors)

  19. Effect of wind turbine surge motion on rotor thrust and induced velocity

    DEFF Research Database (Denmark)

    Vaal, J.B., de; Hansen, Martin Otto Laver; Moan, T.

    2014-01-01

    velocity on a wind turbine rotor is investigated. Specifically, the performance of blade element momentum theory with a quasisteady wake as well as two widely used engineering dynamic inflow models is evaluated. A moving actuator disc model is used as reference, since the dynamics associated with the wake...... will be inherently included in the solution of the associated fluid dynamic problem. Through analysis of integrated rotor loads, induced velocities and aerodynamic damping, it is concluded that typical surge motions are sufficiently slow to not affect the wake dynamics predicted by engineering models significantly...

  20. Development of tunable high pressure CO2 laser for lidar measurements of pollutants and wind velocities

    Science.gov (United States)

    Levine, J. S.; Guerra, M.; Javan, A.

    1980-01-01

    The problem of laser energy extraction at a tunable monochromatic frequency from an energetic high pressure CO2 pulsed laser plasma, for application to remote sensing of atmospheric pollutants by Differential Absorption Lidar (DIAL) and of wind velocities by Doppler Lidar, was investigated. The energy extraction principle analyzed is based on transient injection locking (TIL) at a tunable frequency. Several critical experiments for high gain power amplification by TIL are presented.

  1. Controlled Velocity Testing of an 8-kW Wind Turbine

    Energy Technology Data Exchange (ETDEWEB)

    Larwood, S.; Sencenbaugh, J.; Acker, B.

    2001-07-31

    This paper describes a case study of the controlled-velocity test of an 8-kW wind turbine. The turbine was developed in response to the U.S. Department of Energy's small wind turbine program. As background, the prototype development is discussed. The turbine mechanical and electrical components are described. The turbine was tested on a flatbed truck and driven down an airfield runway at constant relative wind speed. Horizontal furling was used to control over-speed. Various parameters were changed to determine their effects on furling. The testing showed that the machine had insufficient rotor offset for adequate furling. Also, a rotor resonance problem was discovered and remedied. Problems associated with taking the measurements made it difficult to determine if the truck test was a suitable method for code validation. However, qualitative observations gleaned from the testing justified the effort.

  2. Characterization of wind velocities in the wake of a full scale wind turbine using three ground-based synchronized WindScanners

    Science.gov (United States)

    Yazicioglu, Hasan; Angelou, Nikolas; Mikkelsen, Torben; José Trujillo, Juan

    2016-09-01

    The wind energy community is in need of detailed full-field measurements in the wake of wind turbines. Here, three dimensional(3D) wind vector field measurements obtained in the near-wake region behind a full-scale test turbine are presented. Specifically, the wake of a NEG Nordtank turbine, installed at Risoe test field, has been measured from 0 to 2 diameters downstream. For this, three ground-based synchronised short-range WindScanners and a spinner lidar have been used. The 3D wind velocity field has been reconstructed in horizontal and vertical planes crossing the hub. The 10-min mean values of the three wind components reveal detailed information regarding the wake properties while propagating downwind over flat terrain. Furthermore, the wake centre is tracked from the measurements and its meander is investigated as function of yaw misalignment of the turbine. The centre-line wake deficit is calculated both in a Nacelle and Moving Frame of Reference. The results can be used in quantitative validation of numerical wake models.

  3. Spectroscopic Measurements of the Ion Velocity Distribution at the Base of the Fast Solar Wind

    Science.gov (United States)

    Jeffrey, Natasha L. S.; Hahn, Michael; Savin, Daniel W.; Fletcher, Lyndsay

    2018-03-01

    In situ measurements of the fast solar wind reveal non-thermal distributions of electrons, protons, and minor ions extending from 0.3 au to the heliopause. The physical mechanisms responsible for these non-thermal properties and the location where these properties originate remain open questions. Here, we present spectroscopic evidence, from extreme ultraviolet spectroscopy, that the velocity distribution functions (VDFs) of minor ions are already non-Gaussian at the base of the fast solar wind in a coronal hole, at altitudes of thermal equilibrium, (b) fluid motions such as non-Gaussian turbulent fluctuations or non-uniform wave motions, or (c) some combination of both. These observations provide important empirical constraints for the source region of the fast solar wind and for the theoretical models of the different acceleration, heating, and energy deposition processes therein. To the best of our knowledge, this is the first time that the ion VDF in the fast solar wind has been probed so close to its source region. The findings are also a timely precursor to the upcoming 2018 launch of the Parker Solar Probe, which will provide the closest in situ measurements of the solar wind at approximately 0.04 au (8.5 solar radii).

  4. Simulation of Wind Speed Effect on the Fall Velocity of Raindrops

    Directory of Open Access Journals (Sweden)

    Sefri Ayuliana

    2013-08-01

    causes the terminal velocities of raindrops to get larger, and so does their kinetic energy. In that condition, raindrops fall with certain inclination angle. The stronger wind speed, the larger raindrops’ inclination angle and their kinetic energy are when hitting soil surface. Therefore it increases the risk of soil erosion at place where the soil is unstable. Through this study, speed and direction of raindrop when hitting soil surface could be investigated in order to decrease the risk of avalanche at high risk area.

  5. Velocity field and coherent structures in the near wake of a utility-scale wind turbine

    Science.gov (United States)

    Hong, Jiarong; Dasari, Teja; Wu, Yue; Liu, Yun

    2017-11-01

    Super-large-scale particle image velocity (SLPIV) and the associated flow visualization technique using natural snowfall have been shown as an effective tool to probe turbulent velocity field and coherent structures around utility-scale wind turbines (Hong et al. Nature Comm. 2014). Here we present a follow-up study using the data collected during multiple deployments from 2014 to 2016 around the 2.5 MW turbine at EOLOS field station. The data include SLPIV measurements in the near wake of the turbine in a field of view of 120 m (height) x 60 m (width), and the visualization of tip vortex behavior near the bottom blade tip over a broad range of turbine operational conditions. SLPIV results indicate a highly intermittent flow field in the near wake, consisting of both intense wake expansion and contraction events. Such intermittent states of the near wake are shown to be influenced by both the incoming wind conditions and the turbine operation. The visualization of tip vortex behavior demonstrates the presence of the state of consistent vortex formation as well as various types of disturbed vortex states. The occurrence of these states is statistically analyzed and is shown to be correlated with turbine operational and response parameters under different field conditions. National Science Foundation Fluid Dynamics Program.

  6. Extreme bottom velocities induced by wind wave and currents in the Gulf of Gdańsk

    Science.gov (United States)

    Cieślikiewicz, Witold; Dudkowska, Aleksandra; Gic-Grusza, Gabriela; Jędrasik, Jan

    2017-11-01

    The principal goal of this study is to get some preliminary insights about the intensity of water movement generated by wind waves, and due to the currents in the bottom waters of Gulf of Gdańsk, during severe storms. The Gulf of Gdańsk is located in the southern Baltic Sea. This paper presents the results of analysis of wave and current-induced velocities during extreme wind conditions, which are determined based on long-term historical records. The bottom velocity fields originated from wind wave and wind currents, during analysed extreme wind events, are computed independently of each other. The long-term wind wave parameters for the Baltic Sea region are derived from the 44-year hindcast wave database generated in the framework of the project HIPOCAS funded by the European Union. The output from the numerical wave model WAM provides the boundary conditions for the model SWAN operating in high-resolution grid covering the area of the Gulf of Gdańsk. Wind current velocities are calculated with the M3D hydrodynamic model developed in the Institute of Oceanography of the University of Gdańsk based on the POM model. The three dimensional current fields together with trajectories of particle tracers spreading out of bottom boundary layer are modelled, and the calculated fields of bottom velocities are presented in the form of 2D maps. During northerly winds, causing in the Gulf of Gdańsk extreme waves and most significant wind-driven circulation, the wave-induced bottom velocities are greater than velocities due to currents. The current velocities in the bottom layer appeared to be smaller by an order of magnitude than the wave-induced bottom orbital velocities. Namely, during most severe northerly storms analysed, current bottom velocities ranged about 0.1-0.15 m/s, while the root mean square of wave-induced near-seabed velocities reached maximum values of up to 1.4 m/s in the southern part of Gulf of Gdańsk.

  7. Remote Sensing Data in Wind Velocity Field Modelling: a Case Study from the Sudetes (SW Poland)

    Science.gov (United States)

    Jancewicz, Kacper

    2014-06-01

    The phenomena of wind-field deformation above complex (mountainous) terrain is a popular subject of research related to numerical modelling using GIS techniques. This type of modelling requires, as input data, information on terrain roughness and a digital terrain/elevation model. This information may be provided by remote sensing data. Consequently, its accuracy and spatial resolution may affect the results of modelling. This paper represents an attempt to conduct wind-field modelling in the area of the Śnieżnik Massif (Eastern Sudetes). The modelling process was conducted in WindStation 2.0.10 software (using the computable fluid dynamics solver Canyon). Two different elevation models were used: the Global Land Survey Digital Elevation Model (GLS DEM) and Digital Terrain Elevation Data (DTED) Level 2. The terrain roughness raster was generated on the basis of Corine Land Cover 2006 (CLC 2006) data. The output data were post-processed in ArcInfo 9.3.1 software to achieve a high-quality cartographic presentation. Experimental modelling was conducted for situations from 26 November 2011, 25 May 2012, and 26 May 2012, based on a limited number of field measurements and using parameters of the atmosphere boundary layer derived from the aerological surveys provided by the closest meteorological stations. The model was run in a 100-m and 250-m spatial resolution. In order to verify the model's performance, leave-one-out cross-validation was used. The calculated indices allowed for a comparison with results of former studies pertaining to WindStation's performance. The experiment demonstrated very subtle differences between results in using DTED or GLS DEM elevation data. Additionally, CLC 2006 roughness data provided more noticeable improvements in the model's performance, but only in the resolution corresponding to the original roughness data. The best input data configuration resulted in the following mean values of error measure: root mean squared error of velocity

  8. Velocity-intermittency structure for wake flow of the pitched single wind turbine under different inflow conditions

    Science.gov (United States)

    Crist, Ryan; Cal, Raul Bayoan; Ali, Naseem; Rockel, Stanislav; Peinke, Joachim; Hoelling, Michael

    2017-11-01

    The velocity-intermittency quadrant method is used to characterize the flow structure of the wake flow in the boundary layer of a wind turbine array. Multifractal framework presents the intermittency as a pointwise Hölder exponent. A 3×3 wind turbine array tested experimentally provided a velocity signal at a 21×9 downstream location, measured via hot-wire anemometry. The results show a negative correlation between the velocity and the intermittency at the hub height and bottom tip, whereas the top tip regions show a positive correlation. Sweep and ejection based on the velocity and intermittency are dominant downstream from the rotor. The pointwise results reflect large-scale organization of the flow and velocity-intermittency events corresponding to a foreshortened recirculation region near the hub height and the bottom tip.

  9. Analysis of trends between solar wind velocity and energetic electron fluxes at geostationary orbit using the reverse arrangement test

    Science.gov (United States)

    Aryan, Homayon; Boynton, Richard J.; Walker, Simon N.

    2013-02-01

    A correlation between solar wind velocity (VSW) and energetic electron fluxes (EEF) at the geosynchronous orbit was first identified more than 30 years ago. However, recent studies have shown that the relation between VSW and EEF is considerably more complex than was previously suggested. The application of process identification technique to the evolution of electron fluxes in the range 1.8 - 3.5 MeV has also revealed peculiarities in the relation between VSW and EEF at the geosynchronous orbit. It has been revealed that for a constant solar wind density, EEF increase with VSW until a saturation velocity is reached. Beyond the saturation velocity, an increase in VSW is statistically not accompanied with EEF enhancement. The present study is devoted to the investigation of saturation velocity and its dependency upon solar wind density using the reverse arrangement test. In general, the results indicate that saturation velocity increases as solar wind density decreases. This implies that solar wind density plays an important role in defining the relationship between VSW and EEF at the geosynchronous orbit.

  10. Wind direction/velocity and current direction/velocity data from current meter casts in a world wide distribution from 1970-12-06 to 1991-10-01 (NODC Accession 9700218)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Wind direction/velocity and current direction/velocity data were collected using current meter casts in a world wide distribution from December 6, 1970 to October 1,...

  11. AXAOTHER XL -- A spreadsheet for determining doses for incidents caused by tornadoes or high-velocity straight winds

    International Nuclear Information System (INIS)

    Simpkins, A.A.

    1996-09-01

    AXAOTHER XL is an Excel Spreadsheet used to determine dose to the maximally exposed offsite individual during high-velocity straight winds or tornado conditions. Both individual and population doses may be considered. Potential exposure pathways are inhalation and plume shine. For high-velocity straight winds the spreadsheet has the capability to determine the downwind relative air concentration, however for the tornado conditions, the user must enter the relative air concentration. Theoretical models are discussed and hand calculations are performed to ensure proper application of methodologies. A section has also been included that contains user instructions for the spreadsheet

  12. Influence of Rigid Body Motions on Rotor Induced Velocities and Aerodynamic Loads of a Floating Horizontal Axis Wind Turbine

    DEFF Research Database (Denmark)

    de Vaal, Jacobus B.; Hansen, Martin Otto Laver; Moan, Torgeir

    2014-01-01

    This paper discusses the influence of rigid body motions on rotor induced velocities and aerodynamic loads of a floating horizontal axis wind turbine. Analyses are performed with a simplified free wake vortex model specifically aimed at capturing the unsteady and non-uniform inflow typically......, and captures the essential influences of rigid body motions on the rotor loads, induced velocities and wake influence....... experienced by a floating wind turbine. After discussing the simplified model in detail, comparisons are made to a state of the art free wake vortex code, using test cases with prescribed platform motion. It is found that the simplified model compares favourably with a more advanced numerical model...

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

    Directory of Open Access Journals (Sweden)

    J.-L. Caccia

    2004-11-01

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

  14. Effect of wind waves on air-sea gas exchange: proposal of an overall CO2 transfer velocity formula as a function of breaking-wave parameter

    International Nuclear Information System (INIS)

    Zhao, D.; Suzuki, Y.; Komori, S.

    2003-01-01

    A new formula for gas transfer velocity as a function of the breaking-wave parameter is proposed based on correlating gas transfer with whitecap coverage. The new formula for gas transfer across an air-sea interface depends not only on wind speed but also on wind-wave state. At the same wind speed, a higher gas transfer velocity will be obtained for a more developed wind-sea, which is represented by a smaller spectral peak frequency of wind waves. We suggest that the large uncertainties in the traditional relationship of gas transfer velocity with wind speed be ascribed to the neglect of the effect of wind waves. The breaking-wave parameter can be regarded as a Reynolds number that characterizes the intensity of turbulence associated with wind waves in the downward-bursting boundary layer (DBBL). DBBL provides an effective way to exchange gas across the air-sea interface, which might be related to the surface renewal

  15. Regional Analysis of Long-term Local and Synoptic Effects on Wind Velocity and Energy Patterns in Complex Terrain

    Science.gov (United States)

    Belu, R.; Koracin, D. R.

    2017-12-01

    Investments in renewable energy are justified in both environmental and economic terms. Climate change risks call for mitigation strategies aimed to reduce pollutant emissions, while the energy supply is facing high uncertainty by the current or future global economic and political contexts. Wind energy is playing a strategic role in the efforts of any country for sustainable development and energy supply security. Wind energy is a weather and climate-dependent resource, having a natural spatio-temporal variability at time scales ranging from fraction of seconds to seasons and years, while at spatial scales is strongly affected by the topography and vegetation. Main objective of the study is to investigate spatio-temporal characteristics of the wind velocity in the Southwest U.S., that are relevant to wind energy assessment, analysis, development, operation, and grid integration, by using long-term multiple meteorological tower observations. Wind velocity data and other meteorological parameters from five towers, located near Tonopah, Nevada, operated between 2003 to 2008, and from three towers are located in Carson Valley, Nevada, operated between 2006 and 2014 were used in this study. Multi-annual wind speed data collected did not show significant increase trends with increasing elevation; the differences are mainly governed by the topographic complexity, including local atmospheric circulations. Auto- and cross-correlations show a strong coherence between the wind speed and direction with slowly decreasing amplitude of the multi-day periodicity with increasing lag periods. Besides pronounced diurnal periodicity at all locations, detrended fluctuation analysis also showed significant seasonal and annual periodicities, and long-memory persistence with similar characteristics. In spite of significant differences in mean wind speeds among the towers, due to location specifics, the relatively high auto- and cross-correlation coefficients among the towers indicate

  16. Carbon isotope evidence for the latitudinal distribution and wind speed dependence of the air-sea gas transfer velocity

    International Nuclear Information System (INIS)

    Krakauer, Nir Y.

    2006-01-01

    The air-sea gas transfer velocity is an important determinant of the exchange of gases, including CO 2 , between the atmosphere and ocean, but the magnitude of the transfer velocity and what factors control it remains poorly known. Here, we use oceanic and atmospheric observations of 14 C and 13 C to constrain the global mean gas transfer velocity as well as the exponent of its wind speed dependence, utilizing the distinct signatures left by the air-sea exchange of 14 CO 2 and 13 CO 2 . While the atmosphere and ocean inventories of 14 CO 2 and 13 CO 2 constrain the mean gas transfer velocity, the latitudinal pattern in the atmospheric and oceanic 14 C and 13 C distributions contain information about the wind speed dependence. We computed the uptake of bomb 14 C by the ocean for different transfer velocity patterns using pulse response functions from an ocean general circulation model, and evaluated the match between the predicted bomb 14 C concentrations and observationally based estimates for the 1970s-1990s. Using a wind speed climatology based on satellite measurements, we solved either for the best-fit global relationship between gas exchange and mean wind speed or for the mean gas transfer velocity over each of 11 ocean regions. We also compared the predicted consequences of different gas exchange relationships on the rate of change and interhemisphere gradient of 14 C in atmospheric CO 2 with tree-ring and atmospheric measurements. Our results suggest that globally, the dependence of the air-sea gas transfer velocity on wind speed is close to linear, with an exponent of 0.5 ± 0.4, and that the global mean gas transfer velocity at a Schmidt number of 660 is 20 ± 3 cm/hr, similar to the results of previous analyses. We find that the air-sea flux of 13 C estimated from atmosphere and ocean observations also suggests a lower than quadratic dependence of gas exchange on wind speed

  17. Quality and Impact of Indian Doppler Weather Radar Wind Profiles: A Diagnostic Study

    Science.gov (United States)

    Sandeep, A.; Prasad, V. S.; Johny, C. J.

    2017-07-01

    In the tropics, efficient weather forecasts require high-quality vertical profiles of winds to overcome improper coupling of mass and wind fields and balance relationships in the region. The India Meteorological Department (IMD) operates the network of Doppler Weather Radar (DWR) in microwave frequencies (S-band or C-band) at various locations in India. The National Centre for Medium Range Weather Forecasting (NCMRWF) receives the volume velocity processing (VVP) wind profiles from all DWRs through the Global Telecommunication System (GTS) network in near real time. The radar VVP wind is a mean horizontal wind derived at different heights from radial velocities suitable for numerical weather prediction applications. Three numerical experiments, CNTL (without VVP winds), 3DVAR and HYBRID with the assimilation of VVP winds by means of 3-dimensional variational (3dvar) and hybrid data assimilation systems were conducted using the NCMRWF Global Forecast System (NGFS) model. This study had two objectives: (1) quality assessment of VVP winds and (2) investigation of the impact of VVP wind profiles on NGFS model forecast. The quality of VVP wind profiles was assessed against the NGFS model background and radiosonde wind profiles. The absolute values of zonal and meridional wind observation minus background (O-B) increased with the pressure for all DWRs. All radars exhibited the accepted (rejected) ratio as a decreasing (increasing) function of pressure. The resemblance between the zonal and meridional O-B statistics for 3DVAR and HYBRID experiments is apparently remarkable. The accepted VVP winds and radiosonde winds in both experiments (3DVAR and HYBRID) were consistent. The correlation coefficient ( R) was higher at Patna (Patiala) for zonal (meridional) winds in the 3DVAR experiment and at Patna (Jaipur) in the HYBRID experiment. At Chennai, the R value was lower in both the experiments for both wind components. However, because of the assimilation of VVP winds by

  18. Vegetation as an indicator of high wind velocity. Annual progress report, June 15, 1978--March 14, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Hewson, E. W.; Wade, J. E.; Baker, R. W.

    1979-03-01

    The most important results are presented of work completed during the past year of the study Vegetation as an Indicator of High Wind Velocity. The most important achievement during the past year was the completion of a draft of a handbook on the use of trees as an indicator of wind power potential. This handbook describes relationships between mean annual wind speed and indices of wind deformation of two species of trees widely distributed in the western United States. Work during the past year on other species of trees indicates that the techniques calibrated initially for only Douglas-fir and Ponderosa Pine can also be calibrated on other trees including broadleaf trees such as oaks.

  19. Diode laser lidar wind velocity sensor using a liquid-crystal retarder for non-mechanical beam-steering

    DEFF Research Database (Denmark)

    Rodrigo, Peter John; Iversen, Theis Faber Quist; Hu, Qi

    2014-01-01

    the lidar probe beam in two different lines-of-sight (LOS) with a 60° angular separation. Dual-LOS beam-steering isimplemented optically with no moving parts by means of a controllableliquid-crystal retarder (LCR). The LCR switches the polarization betweentwo orthogonal linear states of the lidar beam so......We extend the functionality of a low-cost CW diode lasercoherent lidar from radial wind speed (scalar) sensing to wind velocity(vector) measurements. Both speed and horizontal direction of the wind at~80 m remote distance are derived from two successive radial speedestimates by alternately steering...... it either transmits throughor reflects off a polarization splitter. The room-temperature switching timebetween the two LOS is measured to be in the order of 100μs in one switchdirection but 16 ms in the opposite transition. Radial wind speedmeasurement (at 33 Hz rate) while the lidar beam is repeatedly...

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

    Directory of Open Access Journals (Sweden)

    J.-L. Caccia

    2004-11-01

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

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

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

  1. Influence of the tilting reflection mirror on the temperature and wind velocity retrieved by a polarizing atmospheric Michelson interferometer.

    Science.gov (United States)

    Zhang, Chunmin; Li, Ying

    2012-09-20

    The principles of a polarizing atmospheric Michelson interferometer are outlined. The tilt of its reflection mirror results in deflection of the reflected beam and affects the intensities of the observed inteferogram. This effect is systematically analyzed. Both rectangular and circular apertures are considered. The theoretical expression of the modulation depth and phase of the interferogram are derived. These parameters vary with the inclination angle of the mirror and the distance between the deflection center and the optical axis and significantly influence the retrieved temperature and wind speed. If the wind and temperature errors are required to be less than 3 m/s and 5 K, the deflection angle must be less than 0.5°. The errors are also dependent on the shape of aperture. If the reflection mirror is deflected in one direction, the temperature error is smaller for a circular aperture (1.3 K) than for a rectangular one (2.6 K), but the wind velocity errors are almost the same (less than 3 m/s). If the deflection center and incident light beam are coincident, the temperature errors are 3 × 10(-4) K and 0.45 K for circular and rectangular apertures, respectively. The wind velocity errors are 1.2 × 10(-3) m/s and 0.06 m/s. Both are small. The result would be helpful for theoretical research and development of the static polarization wind imaging interferometer.

  2. Wind stress, curl and vertical velocity in the Bay of Bengal during southwest monsoon, 1984

    Digital Repository Service at National Institute of Oceanography (India)

    Babu, M.T.; Heblekar, A.K.; Murty, C.S.

    Wind distribution observed during southwest monsoon of 1984 has used to derive the mean wind stress for the season at every 1 degree square grid and curl over the Bay of Bengal. Two regions of maximum wind stress are present over the Bay of Bengal...

  3. VLTI-AMBER velocity-resolved aperture-synthesis imaging of η Carinae with a spectral resolution of 12 000. Studies of the primary star wind and innermost wind-wind collision zone

    Science.gov (United States)

    Weigelt, G.; Hofmann, K.-H.; Schertl, D.; Clementel, N.; Corcoran, M. F.; Damineli, A.; de Wit, W.-J.; Grellmann, R.; Groh, J.; Guieu, S.; Gull, T.; Heininger, M.; Hillier, D. J.; Hummel, C. A.; Kraus, S.; Madura, T.; Mehner, A.; Mérand, A.; Millour, F.; Moffat, A. F. J.; Ohnaka, K.; Patru, F.; Petrov, R. G.; Rengaswamy, S.; Richardson, N. D.; Rivinius, T.; Schöller, M.; Teodoro, M.; Wittkowski, M.

    2016-10-01

    Context. The mass loss from massive stars is not understood well. η Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims: We want to investigate the structure and kinematics of η Car's primary star wind and wind-wind collision zone with a high spatial resolution of ~6 mas (~14 au) and high spectral resolution of R = 12 000. Methods: Observations of η Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision. Results: We present velocity-resolved aperture-synthesis images reconstructed in more than 100 different spectral channels distributed across the Brγ 2.166 μm emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately -140 to - 376 km s-1 measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of - 277 km s-1, the position angle of the symmetry axis of the fan is ~126°. The fan-shaped structure extends approximately 8.0 mas (~18.8 au) to the southeast and 5.8 mas (~13.6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three

  4. VLTI-AMBER Velocity-Resolved Aperture-Synthesis Imaging of Eta Carinae with a Spectral Resolution of 12 000: Studies of the Primary Star Wind and Innermost Wind-Wind Collision Zone

    Science.gov (United States)

    Weigelt, G.; Hofmann, K.-H.; Schertl, D.; Clementel, N.; Corcoran, M. F.; Damineli, A.; de Wit, W.-J.; Grellmann, R.; Groh, J.; Guieu, S.; hide

    2016-01-01

    The mass loss from massive stars is not understood well. Eta Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of Car's primary star wind and wind-wind collision zone with a high spatial resolution of approx.6 mas (approx.14 au) and high spectral resolution of R = 12 000. Methods. Observations of Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision. Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 di erent spectral channels distributed across the Br(gamma) 2.166 micron emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately -140 to -376 km/s measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of -277 km/s, the position angle of the symmetry axis of the fan is 126. The fan-shaped structure extends approximately 8.0 mas (approx.18:8 au) to the southeast and 5.8 mas (approx.13:6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three

  5. Field computation of winds-aloft velocities from single theodolite pilot balloon observations

    Science.gov (United States)

    Bill C. Ryan

    1976-01-01

    The ability to determine wind speeds and directions in the first few thousand meters of the atmosphere is important in many forestry operations such as smolce management, aircraft seeding and spraying, prescribed burning, and wildfire suppression. A hand-held electronic calculator can be used to compute winds aloft as balloon observations are taken. Calculations can...

  6. Estimation of wind velocity over a complex terrain using the Generalized Mapping Regressor

    Energy Technology Data Exchange (ETDEWEB)

    Beccali, M.; Marvuglia, A. [Dipartimento di Ricerche Energetiche ed Ambientali (DREAM), Universita degli Studi di Palermo, Viale delle Scienze - edificio 9, 90128 Palermo (Italy); Cirrincione, G. [Department de Genie Electrique, Universite de Picardie Jules Verne, 33, Rue Saint Leu, 80039 Amiens (France); Serporta, C. [ISSIA-CNR (Institute on Intelligent Systems for the Automation), Section of Palermo, Via Dante12, Palermo (Italy)

    2010-03-15

    Wind energy evaluation is an important goal in the conversion of energy systems to more environmentally friendly solutions. In this paper, we present a novel approach to wind speed spatial estimation on the isle of Sicily (Italy): an incremental self-organizing neural network (Generalized Mapping Regressor - GMR) is coupled with exploratory data analysis techniques in order to obtain a map of the spatial distribution of the average wind speed over the entire region. First, the topographic surface of the island was modelled using two different neural techniques and by exploiting the information extracted from a digital elevation model of the region. Then, GMR was used for automatic modelling of the terrain roughness. Afterwards, a statistical analysis of the wind data allowed for the estimation of the parameters of the Weibull wind probability distribution function. In the last sections of the paper, the expected values of the Weibull distributions were regionalized using the GMR neural network. (author)

  7. Estimation of the variations of ventilation rate and indoor radon concentration using the observed wind velocity and indoor-outdoor temperature difference

    International Nuclear Information System (INIS)

    Nagano, Katsuhiro; Inose, Yuichi; Kojima, Hiroshi

    2006-01-01

    The indoor radon concentration in the building depends on the ventilation rate. Measurement results of indoor-outdoor pressure difference showed the ventilation rate correlated closely with the indoor-outdoor pressure difference. The observation results showed that one of factor of indoor-outdoor pressure difference was the wind velocity. When the wind velocity is small, the ventilation rate is affected by the indoor-outdoor temperature difference and the effect depends on the wind velocity. The temporal variation of indoor radon concentration was predicted by the time depending indoor radon balance model and the ventilation rate estimated from the wind velocity and the indoor-outdoor temperature difference. The temporal variations of predicted radon concentration gave good agreement with the experimental values. The measurement method, indoor radon concentration and ventilation rate, factors of temporal variation of ventilation rate, and prediction of indoor radon concentration are reported. (S.Y.)

  8. Magnetic Geared Radial Axis Vertical Wind Turbine for Low Velocity Regimes

    Directory of Open Access Journals (Sweden)

    Wei Wei Teow

    2018-01-01

    Full Text Available In the 21st century, every country is seeking an alternative source of energy especially the renewable sources. There are considerable developments in the wind energy technology in recent years and in more particular on the vertical axis wind turbine (VAWT as they are modular, less installation cost and portable in comparison with that of the horizontal axis wind turbine (HAWT systems. The cut-in speed of a conventional wind turbine is 3.5 m/s to 5 m/s. Mechanical geared generators are commonly found in wind technology to step up power conversion to accommodate the needs of the generator. Wind turbine gearboxes suffer from overload problem and frequent maintenance in spite of the high torque density produced. However, an emerging alternative to gearing system is Magnetic Gear (MG as it offers significant advantages such as free from maintenance and inherent overload protection. In this project, numerical analysis is done on designed magnetic gear greatly affects the performance of the generator in terms of voltage generation. Magnetic flux density is distributed evenly across the generator as seen from the uniform sinusoidal output waveform. Consequently, the interaction of the magnetic flux of the permanent magnets has shown no disturbance to the output of the generator as the voltage generated shows uniform waveform despite the rotational speed of the gears. The simulation is run at low wind speed and the results show that the generator starts generating a voltage of 240 V at a wind speed of 1.04 m/s. This shows great improvement in the operating capability of the wind turbine.

  9. Influence of wind velocity fluctuation on air temperature difference between the fan and ground levels and the effect of frost protective fan operation

    International Nuclear Information System (INIS)

    Araki, T.; Matsuo, K.; Miyama, D.; Sumikawa, O.; Araki, S.

    2008-01-01

    We invested the influence of wind velocity fluctuation on air temperature difference between the fan (4.8 m) and ground levels (0.5 m) and the effect of frost protective fan operation in order to develop a new method to reduce electricity consumption due to frost protective fan operation. The results of the investigations are summarized as follows: (1) Air temperature difference between the fan (4.8 m) and ground levels (0.5 m) was decreased following an increase in wind velocity, and the difference was less than 1°C for a wind velocity more than 3.0 m/s at a height of 6.5 m. (2) When the wind velocity was more than 2-3 m/s, there was hardly any increase in the temperature of the leaves. In contrast, when the wind velocity was less than 2-3 m/s, an increase in the temperature of the leaves was observed. Based on these results, it is possible that when the wind velocity is greater than 2-3 m, it prevents thermal inversion. Therefore, there would be no warmer air for the frost protective fan to return to the tea plants and the air turbulence produced by the frost protective fan would not reach the plants under the windy condition

  10. Hybrid simulations of the expanding solar wind: Temperatures and drift velocities

    Czech Academy of Sciences Publication Activity Database

    Hellinger, Petr; Trávníček, Pavel; Mangeney, A.; Grappin, R.

    2003-01-01

    Roč. 30, č. 5 (2003), s. 15-1-15-4 ISSN 0094-8276 R&D Projects: GA AV ČR IAB3042106 Grant - others:CNRS(FR) PICS 1175 Institutional research plan: CEZ:AV0Z3042911 Keywords : expanding solar wind * hybrid simulations Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.422, year: 2003

  11. Alignment of stress, mean wind, and vertical gradient of the velocity vector

    DEFF Research Database (Denmark)

    Berg, Jacob; Mann, Jakob; Patton, E.G.

    2012-01-01

    In many applications in the atmospheric surface layer the turbulent-viscosity hypothesis is applied, i.e. the stress vector can be described through the vertical gradient of velocity. In the atmospheric surface layer, where the Coriolis force and baroclinic effects are considered negligible...

  12. The role of wind field induced flow velocities in destratification and hypoxia reduction at Meiling Bay of large shallow Lake Taihu, China.

    Science.gov (United States)

    Jalil, Abdul; Li, Yiping; Du, Wei; Wang, Wencai; Wang, Jianwei; Gao, Xiaomeng; Khan, Hafiz Osama Sarwar; Pan, Baozhu; Acharya, Kumud

    2018-01-01

    Wind induced flow velocity patterns and associated thermal destratification can drive to hypoxia reduction in large shallow lakes. The effects of wind induced hydrodynamic changes on destratification and hypoxia reduction were investigated at the Meiling bay (N 31° 22' 56.4″, E 120° 9' 38.3″) of Lake Taihu, China. Vertical flow velocity profile analysis showed surface flow velocities consistency with the wind field and lower flow velocity profiles were also consistent (but with delay response time) when the wind speed was higher than 6.2 m/s. Wind field and temperature found the control parameters for hypoxia reduction and for water quality conditions at the surface and bottom profiles of lake. The critical temperature for hypoxia reduction at the surface and the bottom profile was ≤24.1C° (below which hypoxic conditions were found reduced). Strong prevailing wind field (onshore wind directions ESE, SE, SSE and E, wind speed ranges of 2.4-9.1 m/s) reduced the temperature (22C° to 24.1C°) caused reduction of hypoxia at the near surface with a rise in water levels whereas, low to medium prevailing wind field did not supported destratification which increased temperature resulting in increased hypoxia. Non-prevailing wind directions (offshore) were not found supportive for the reduction of hypoxia in study area due to less variable wind field. Daytime wind field found more variable (as compared to night time) which increased the thermal destratification during daytime and found supportive for destratification and hypoxia reduction. The second order exponential correlation found between surface temperature and Chlorophyll-a (R 2 : 0.2858, Adjusted R-square: 0.2144 RMSE: 4.395), Dissolved Oxygen (R 2 : 0.596, Adjusted R-square: 0.5942, RMSE: 0.3042) concentrations. The findings of the present study reveal the driving mechanism of wind induced thermal destratification and hypoxic conditions, which may further help to evaluate the wind role in eutrophication

  13. Meridional overturning circulation: stability and ocean feedbacks in a box model

    NARCIS (Netherlands)

    Cimatoribus, A.A.; Drijfhout, S.S.; Dijkstra, H.A.|info:eu-repo/dai/nl/073504467

    2014-01-01

    A box model of the inter-hemispheric Atlantic meridional overturning circulation is developed, including a variable pycnocline depth for the tropical and subtropical regions. The circulation is forced by winds over a periodic channel in the south and by freshwater forcing at the surface. The model

  14. Prediction of velocity of the wind generation in Kobe City College of Technology; Kobe Kosen ni okeru furyoku hatsuden no yosoku

    Energy Technology Data Exchange (ETDEWEB)

    Akamatsu, K.; Kanemura, M.; Amako, K.

    1997-11-25

    Wind conditions, such as average wind velocity for 10 minutes, maximum instantaneous wind velocity and wind directions, are measured by the anemometer and anemoscope installed 3m above the roof of the Kobe City College of Technology`s Information Processing Center building, to collect the data necessary to validate possibility of wind power generation, if the wind system is installed in the college site. Monthly availability of power is estimated from the output power characteristics curve for a generator having a rated capacity of 200W and wind velocity data collected for 9 months. It will generate power of only 144kWh, even when operated to give the rated output, or approximately 8.5kWh at the highest in a month, because of availability of wind power limited to around 30% of the total as estimated from the relative frequency distribution. It is therefore desirable to install a number of units having a rated capacity of 200W or else a smaller number of larger units. Assuming that days that give the highest output for 24 hours last 1 month, a power of 54.3kWh will be generated. It is estimated, based on these results, that a hybrid unit, in which a wind power generator installed at a high place is combined with a solar unit, can provide power required for nighttime lighting, if a wind power unit having a rated capacity of 2kW is field-controlled under an optimum condition. 13 figs., 3 tabs.

  15. An atlas of monthly mean distributions of SSMI surface wind speed, AVHRR/2 sea surface temperature, AMI surface wind velocity, TOPEX/POSEIDON sea surface height, and ECMWF surface wind velocity during 1993

    Science.gov (United States)

    Halpern, D.; Fu, L.; Knauss, W.; Pihos, G.; Brown, O.; Freilich, M.; Wentz, F.

    1995-01-01

    The following monthly mean global distributions for 1993 are presented with a common color scale and geographical map: 10-m height wind speed 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 wind speed 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 wind speed and direction produced by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of annual mean, monthly mean, and sampling distributions are displayed.

  16. Tangential discontinuities in the solar wind: Correlated field and velocity changes in the Kelvin-Helmholtz Instability

    International Nuclear Information System (INIS)

    Neugebauer, M.; Alexander, C.J.; Schwenn, R.; Richter, A.K.

    1986-01-01

    Three-dimensional Helios plasma and field data are used to investigate the relative changes in direction of the velocity and magnetic field vectors across tangential discontinuities, (TDs) in the solar wind at solar distances of 0.29--0.50 AU. It is found for tangential discontinuities with both Δv and ΔB/B large that Δv and ΔB are closely aligned with each other, in agreement with the unexpected results of previous studies of tangential discontinuities observed at 1 AU and beyond. It is shown that this effect probably results from the destruction by the Kelvin-Helmholtz instability of TDs for which Δv and ΔB are not aligned. The observed decrease in the number of interplanetary discontinuities with increasing solar distance may be associated with the growth of the Kelvin-Helmholtz instability with decreasing Alfven speed

  17. Evaporation of Arabian light crude oil spilled on sea and on beach sands : influence of solar radiation and wind velocity

    International Nuclear Information System (INIS)

    Bergueiro, J.R.; Marti, A.; Fuertes, A.; Moreno, S.; Guijarro, S.

    1998-01-01

    The evaporation of crude oil resulting from a spill on sea water was studied to develop a simulation model. Evaporation takes place within a complex process of mass and energy transfer. The effects of physical and chemical variables (such as wind velocity and direct and diffused solar radiation) and the environmental conditions of the spillage were also considered. Arabian crude oil was used in the simulation model for crude oil spillage on sea water. An equation for the evaporation process was used to correlate the evaporated fraction of oil as a function of time. The area of spreading was determined as a function of the dominant stage at each moment of spreading. The evaporation of spilled crude oil on beach sand consisting of three different particle sizes was also studied and used for a simulation model for crude oil spillage on a polluted beach. 7 refs., 6 tabs., 10 figs

  18. On the prediction of threshold friction velocity of wind erosion using soil reflectance spectroscopy

    Science.gov (United States)

    Li, Junran; Flagg, Cody B.; Okin, Gregory S.; Painter, Thomas H.; Dintwe, Kebonye; Belnap, Jayne

    2015-01-01

    Current approaches to estimate threshold friction velocity (TFV) of soil particle movement, including both experimental and empirical methods, suffer from various disadvantages, and they are particularly not effective to estimate TFVs at regional to global scales. Reflectance spectroscopy has been widely used to obtain TFV-related soil properties (e.g., moisture, texture, crust, etc.), however, no studies have attempted to directly relate soil TFV to their spectral reflectance. The objective of this study was to investigate the relationship between soil TFV and soil reflectance in the visible and near infrared (VIS–NIR, 350–2500 nm) spectral region, and to identify the best range of wavelengths or combinations of wavelengths to predict TFV. Threshold friction velocity of 31 soils, along with their reflectance spectra and texture were measured in the Mojave Desert, California and Moab, Utah. A correlation analysis between TFV and soil reflectance identified a number of isolated, narrow spectral domains that largely fell into two spectral regions, the VIS area (400–700 nm) and the short-wavelength infrared (SWIR) area (1100–2500 nm). A partial least squares regression analysis (PLSR) confirmed the significant bands that were identified by correlation analysis. The PLSR further identified the strong relationship between the first-difference transformation and TFV at several narrow regions around 1400, 1900, and 2200 nm. The use of PLSR allowed us to identify a total of 17 key wavelengths in the investigated spectrum range, which may be used as the optimal spectral settings for estimating TFV in the laboratory and field, or mapping of TFV using airborne/satellite sensors.

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

    Science.gov (United States)

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

    2013-10-01

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

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

    Directory of Open Access Journals (Sweden)

    G. Stober

    2013-10-01

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

  1. The effect of wind velocity, air temperature and humidity on NH 3 and SO 2 transfer into bean leaves ( phaseolus vulgaris L.)

    Science.gov (United States)

    van Hove, L. W. A.; Vredenberg, W. J.; Adema, E. H.

    The influence of wind velocity, air temperature and vapour pressure deficit of the air (VPD) on NH 3 and SO 2 transfer into bean leaves ( Phaseolus vulgaris L.) was examined using a leaf chamber. The measurements suggested a transition in the properties of the leaf boundary layer at a wind velocity of 0.3-0.4 ms -1 which corresponds to a Recrit value of about 2000. At higher wind velocities the leaf boundary layer resistance ( rb) was 1.5-2 times lower than can be calculated from the theory. Nevertheless, the assessed relationships between rb and wind velocity appeared to be similar to the theoretical derived relationship for rb. The NH 3 flux and in particular the SO 2 flux into the leaf strongly increased at a VPD decline. The increase of the NH 3 flux could be attributed to an increase of the stomatal conductance ( gs). However, the increase of the SO 2 flux could only partly be explained by an increase of gs. An apparent additional uptake was also observed for the NH 3 uptake at a low temperature and VPD. The SO 2 flux was also influenced by air temperature which could be explained by a temperature effect on gs. The results suggest that calculation of the NH 3 and SO 2 flux using data of gs gives a serious understimation of the real flux of these gases into leaves at a low temperature and VPD.

  2. An Estimate of Solar Wind Velocity Profiles in a Coronal Hole and a Coronal Streamer Area (6-40 R(radius symbol)

    Science.gov (United States)

    Patzold, M.; Tsurutani, B. T.; Bird, M. K.

    1995-01-01

    Total electron content data obtained from the Ulysses Solar Corona Experiment (SCE) in 1991 were used to select two data sets, one associated with a coronal hole and the other with coronal streamer crossings. (This is largely equatorial data shortly after solar maximum.) The solar wind velocity profile is estimated for these areas.

  3. RETRACTED: The influence of sand diameter and wind velocity on sand particle lift-off and incident angles in the windblown sand flux

    Science.gov (United States)

    Bo, Tian-Li; Zheng, Xiao-Jing; Duan, Shao-Zhen; Liang, Yi-Rui

    2013-05-01

    This article has been retracted: please see Elsevier Policy on Article Withdrawal. This article has been retracted at the request of the Editors-in-Chief. This article also contains significant similarity with parts of text, written by the same author(s), that have appeared in Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, The influence of wind velocity and sand grain diameter on the falling velocities of sand particles, Powder Technology, Volume 241, June 2013, Pages 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Analysis of sand particles' lift-off and incident velocities in wind-blown sand flux, Acta Mechanica Sinica, April 2013, Volume 29, Issue 2, pp 158-165. Tian-Li Bo, Xiao-Jing Zheng, Shao-Zhen Duan, Yi-Rui Liang, Influence of sand grain diameter and wind velocity on lift-off velocities of sand particles, The European Physical Journal E, May 2013, 36:50. Tian-Li Bo, Shao-Zhen Duan, Xiao-Jing Zheng, Yi-Rui Liang, The influence of sand bed temperature on lift-off and falling parameters in windblown sand flux, Geomorphology, Volume 204, 1 January 2014, Pages 477-484. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

  4. North Pacific Meridional Mode over the Common Era

    Science.gov (United States)

    Sanchez, S. C.; Charles, C. D.; Amaya, D. J.; Miller, A. J.

    2016-12-01

    The Pacific Meridional Mode (PMM) has been increasingly recognized as an influential mode of variability for channeling extratropical anomalies to the equatorial ocean-atmosphere system. The PMM has been identified as an important precursor for ENSO, a source of much decadal power in the tropical Pacific, and is potentially intensifying. It is still unknown why the Pacific Meridional Mode might be intensifying; most arguments center around the changing mean state associated with anthropogenic global warming. There are a number of processes by which the background state could influence the PMM: altering the location of trade winds, the characteristics of stochastic forcing, the sensitivity of latent heat flux to surface wind anomalies, the wind response to SST anomalies, or changing the Intertropical Convergence Zone (ITCZ) structure. Recent work has found that the PMM is particularly sensitive to ITCZ shifts in intensity and location (using a simple linear coupled model, [Martinez-Villalobos and Vimont 2016]). Over the last millennium the ITCZ has experienced epochs of notable latitudinal shifts to balance the cross equatorial energy transport. Here we investigate how the strength of the PMM may have varied with these shifts in the ITCZ over the Common Era using the CESM-Last Millennium Ensemble (LME). We assess the strength of the PMM pathway by the degree of air-sea coupling and the amplitude of tropical decadal variability. We expect the ITCZ location and the degree of air-sea coupling (WES feedback) to play a critical role in determining the effectiveness and intensity of the PMM pathway. We verify our inferences in the LME with coral paleoproxy records from the central tropical Pacific. Chiefly we target records from the Line Islands (spanning 1°N to 6°N) to infer variations in the location of the ITCZ and the amplitude of decadal variability. This work enables us to discuss the idea of an intensifying PMM in a more historical context.

  5. Seasonal variations in the equatorial thermospheric wind measured at Arequipa, Peru

    Energy Technology Data Exchange (ETDEWEB)

    Biondi, M.A.; Merriwether, J.W.; Fejer, B.G.; Gonzalez, S.A.

    1990-08-01

    Studies have been carried out Arequipa, Peru, of the seasonal variations in the thermospheric winds at moderate solar flux levels and geomagnetic activity. Fabry-Perot interferometer measurements of the doppler shifts in the 630.0 nm nightglow emission line from March to August 1983 and from April to October 1988 have yielded monthly-average meridional winds that are nearly zero (<50 m/s) and possible fluctuating in direction through much of the night but develop a southward flow at 50 - 100 m/s in the early and the late night from May onward. The average zonal winds are eastward throughout the night, reaching peak velocities before local midnight and then decreasing. The peak velocities increase to a maximum around the June solstice. The winds are generally stronger in 1988 than in 1983, even thought the solar EUV fluxes are comparable fro both years. Comparison of the present results with earlier satellite measurements, as embodied in the Horizontal Wind Model of Hedin et al., reveals generally satisfactory agreement at the equinox and June solstice, except for the June 1988 period. NCAR Therospheric General Circulation Model, calculated for similar solar flux levels, yields meridional and zonal wind variations which exhibit the same temporal behaviors but generally smaller values than the present measurements.

  6. Pulling the Meridional Overturning Circulation From the South DESC0005100

    Energy Technology Data Exchange (ETDEWEB)

    Cessi, Paola [Univ. of California, San Diego, CA (United States); Wolfe, Christopher L. [Scripps Inst. of Oceanography, San Diego, CA (United States)

    2015-11-25

    This project concerned the Atlantic Meridional Overturning Circulation (AMOC), its stability, variability and sensitivity to atmospheric forcing, both mechanical (wind-stress) and thermodynamical (heat and freshwater surface fluxes). The focus of the study is the interhemispheric cell in the largely adiabatic regime, where the flow is characterized by a descending branch in the high latitudes of the North Atlantic and the upwelling branch in the Antarctic Circumpolar Current (ACC) region of the Southern Ocean. These two end points are connected by shared isopycnals along which the flow takes place. The approach is to systematically study the amplitude and frequency of the AMOC’s response to localized buoyancy with an ocean-only model in both coarse and high-resolution configurations, analyzed with innovative diagnostics, focused on the “residual overturning circulation” (ROC), which is the proper measure of the transport of heat and other tracers.

  7. On the stability of the Atlantic meridional overturning circulation

    Science.gov (United States)

    Hofmann, Matthias; Rahmstorf, Stefan

    2009-01-01

    One of the most important large-scale ocean current systems for Earth's climate is the Atlantic meridional overturning circulation (AMOC). Here we review its stability properties and present new model simulations to study the AMOC's hysteresis response to freshwater perturbations. We employ seven different versions of an Ocean General Circulation Model by using a highly accurate tracer advection scheme, which minimizes the problem of numerical diffusion. We find that a characteristic freshwater hysteresis also exists in the predominantly wind-driven, low-diffusion limit of the AMOC. However, the shape of the hysteresis changes, indicating that a convective instability rather than the advective Stommel feedback plays a dominant role. We show that model errors in the mean climate can make the hysteresis disappear, and we investigate how model innovations over the past two decades, like new parameterizations and mixing schemes, affect the AMOC stability. Finally, we discuss evidence that current climate models systematically overestimate the stability of the AMOC. PMID:19897722

  8. Estimation of bubble-mediated air–sea gas exchange from concurrent DMS and CO2 transfer velocities at intermediate–high wind speeds

    Directory of Open Access Journals (Sweden)

    T. G. Bell

    2017-07-01

    Full Text Available 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 wind speeds up to 21 m s−1. These differences occur at and above the approximate wind speed 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 wind speed. Models used to estimate bubble-mediated transfer from in situ whitecap fraction underpredict the observations, particularly at intermediate wind speeds. 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.

  9. F-Region Neutral Winds Obtained from the Thermospheric Wind Assimilation Model (TWAM).

    Science.gov (United States)

    Molina, I.; Scherliess, L.; Lomidze, L.

    2017-12-01

    Thermospheric neutral winds play a major role in the transport of energy and momentum in the Earth's upper atmosphere. They are also responsible for changes in the composition of the thermosphere and affect the dynamics and morphology of the ionospheric plasma. However, direct observations of the winds are limited both temporally and spatially, which makes global studies very difficult. On the other hand, ionospheric measurements are relatively easier to make and there is a very good distribution of various instruments worldwide. Data assimilation is a technique that combines information from observations and a physical model. Observed data are assimilated into the model as a constraint for the physical equations that describe the dynamics of the system, which allows estimates of unobserved driving forces, e.g., the neutral wind. The Thermospheric Wind Assimilation Model (TWAM) is a data assimilation model that uses the output of the Global Assimilation of Ionospheric Measurements Full Physics (GAIM-FP) model. GAIM-FP is an ionospheric data assimilation model that is based on an ensemble Kalman filter. The ionosphere and plasmasphere electron density and its associated errors are evolved using a physics-based Ionosphere-Plasmasphere Model which solves the ion and electron continuity and momentum equations numerically. TWAM uses an implicit Kalman filter and combines the magnetic meridional winds from GAIM-FP with the equation of motion of the neutral gas. TWAM also uses information from GAIM-FP about the 3-D electron density and ion diffusion velocities. The output of the model is the global zonal and meridional thermospheric neutral winds at low and mid latitudes. This approach has been successfully used to investigate the climatology of thermospheric neutral winds and the physical mechanisms that drive the Weddell Sea Anomaly. We present the first results of our efforts to develop TWAM to use it to analyze day-to-day quiet time data.

  10. Demonstration of synchronised scanning Lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

    Science.gov (United States)

    van Dooren, M. F.; Kühn, M.; PetroviĆ, V.; Bottasso, C. L.; Campagnolo, F.; Sjöholm, M.; Angelou, N.; Mikkelsen, T.; Croce, A.; Zasso, A.

    2016-09-01

    This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dual- Lidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of Lidar scanning to measuring small scale wind flow effects. The downsides of Lidar with respect to the hot wire probes are the larger measurement probe volume and the loss of some measurements due to moving blades. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning, and the fact that remote sensing techniques do not disturb the flow while measuring. The research campaign revealed a high potential for using short-range WindScanner Lidar for accurately measuring small scale flow structures in a wind tunnel.

  11. UARS Wind Imaging Interferometer (WINDII) Level 3AL V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The Wind Imaging Interferometer (WINDII) Level 3AL data product consists of daily, 4 degree increment latitude-ordered vertical profiles of meridional and zonal wind...

  12. UARS Wind Imaging Interferometer (WINDII) Level 3AT V001

    Data.gov (United States)

    National Aeronautics and Space Administration — The Wind Imaging Interferometer (WINDII) Level 3AT data product consists of daily, 65.536 second interval time-ordered vertical profiles of meridional and zonal wind...

  13. Inferences of the deep solar meridional flow

    Science.gov (United States)

    Böning, Vincent G. A.

    2017-10-01

    Understanding the solar meridional flow is important for uncovering the origin of the solar activity cycle. Yet, recent helioseismic estimates of this flow have come to conflicting conclusions in deeper layers of the solar interior, i.e., at depths below about 0.9 solar radii. The aim of this thesis is to contribute to a better understanding of the deep solar meridional flow. Time-distance helioseismology is the major method for investigating this flow. In this method, travel times of waves propagating between pairs of locations on the solar surface are measured. Until now, the travel-time measurements have been modeled using the ray approximation, which assumes that waves travel along infinitely thin ray paths between these locations. In contrast, the scattering of the full wave field in the solar interior due to the flow is modeled in first order by the Born approximation. It is in general a more accurate model of the physics in the solar interior. In a first step, an existing model for calculating the sensitivity of travel-time measurements to solar interior flows using the Born approximation is extended from Cartesian to spherical geometry. The results are succesfully compared to the Cartesian ones and are tested for self-consistency. In a second step, the newly developed model is validated using an existing numerical simulation of linear wave propagation in the Sun. An inversion of artificial travel times for meridional flow shows excellent agreement for noiseless data and reproduces many features in the input flow profile in the case of noisy data. Finally, the new method is used to infer the deep meridional flow. I used Global Oscillation Network Group (GONG) data that were earlier analyzed using the ray approximation and I employed the same Substractive Optimized Local Averaging (SOLA) inversion technique as in the earlier study. Using an existing formula for the covariance of travel-time measurements, it is shown that the assumption of uncorrelated errors

  14. Climatology of Neutral vertical winds in the midlatitude thermosphere

    Science.gov (United States)

    Kerr, R.; Kapali, S.; Riccobono, J.; Migliozzi, M. A.; Noto, J.; Brum, C. G. M.; Garcia, R.

    2017-12-01

    More than one thousand measurements of neutral vertical winds, relative to an assumed average of 0 m/s during a nighttime period, have been made at Arecibo Observatory and the Millstone Hill Optical Facility since 2012, using imaging Fabry-Perot interferometers. These instruments, tuned to the 630 nm OI emission, are carefully calibrated for instrumental frequency drift using frequency stabilized lasers, allowing isolation of Doppler motion in the zenith with 1-2 m/s accuracy. As one example of the results, relative vertical winds at Arecibo during quiet geomagnetic conditions near winter solstice 2016, range ±70 m/s and have a one standard deviation statistical variability of ±34 m/s. This compares with a ±53 m/s deviation from the average meridional wind, and a ±56 m/s deviation from the average zonal wind measured during the same period. Vertical neutral wind velocities for all periods range from roughly 30% - 60% of the horizontal velocity domain at Arecibo. At Millstone Hill, the vertical velocities relative to horizontal velocities are similar, but slightly smaller. The midnight temperature maximum at Arecibo is usually correlated with a surge in the upward wind, and vertical wind excursions of more than 80 m/s are common during magnetic storms at both sites. Until this compilation of vertical wind climatology, vertical motions of the neutral atmosphere outside of the auroral zone have generally been assumed to be very small compared to horizontal transport. In fact, excursions from small vertical velocities in the mid-latitude thermosphere near the F2 ionospheric peak are common, and are not isolated events associated with unsettled geomagnetic conditions or other special dynamic conditions.

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

    Science.gov (United States)

    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.

  16. Mathematical Modeling for Lateral Displacement Induced by Wind Velocity Using Monitoring Data Obtained from Main Girder of Sutong Cable-Stayed Bridge

    Directory of Open Access Journals (Sweden)

    Gao-Xin Wang

    2014-01-01

    Full Text Available Based on the health monitoring system installed on the main span of Sutong Cable-Stayed Bridge, GPS displacement and wind field are real-time monitored and analyzed. According to analytical results, apparent nonlinear correlation with certain discreteness exists between lateral static girder displacement and lateral static wind velocity; thus time series of lateral static girder displacement are decomposed into nonlinear correlation term and discreteness term, nonlinear correlation term of which is mathematically modeled by third-order Fourier series with intervention of lateral static wind velocity and discreteness term of which is mathematically modeled by the combined models of ARMA(7,4 and EGARCH(2,1. Additionally, stable power spectrum density exists in time series of lateral dynamic girder displacement, which can be well described by the fourth-order Gaussian series; thus time series of lateral dynamic girder displacement are mathematically modeled by harmonic superposition function. By comparison and verification between simulative and monitoring lateral girder displacements from September 1 to September 3, the presented mathematical models are effective to simulate time series of lateral girder displacement from main girder of Sutong Cable-Stayed Bridge.

  17. Demonstration of synchronised scanning Lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

    DEFF Research Database (Denmark)

    van Dooren, M F; Kühn, M.; Petrovic, V.

    2016-01-01

    of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of Lidar scanning to measuring small scale wind flow effects. The downsides of Lidar with respect to the hot wire probes are the larger measurement probe volume and the loss of some measurements due......-range WindScanner Lidars to demonstrate the benefits of synchronised scanning Lidars in such experimental surroundings for the first time. The dualLidar system can provide fully synchronised trajectory scans with sampling time scales ranging from seconds to minutes. First, staring mode measurements were...... compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement...

  18. Meridional Flow Observations: Implications for the current Flux Transport Models

    International Nuclear Information System (INIS)

    Gonzalez Hernandez, Irene; Komm, Rudolf; Kholikov, Shukur; Howe, Rachel; Hill, Frank

    2011-01-01

    Meridional circulation has become a key element in the solar dynamo flux transport models. Available helioseismic observations from several instruments, Taiwan Oscillation Network (TON), Global Oscillation Network Group (GONG) and Michelson Doppler Imager (MDI), have made possible a continuous monitoring of the solar meridional flow in the subphotospheric layers for the last solar cycle, including the recent extended minimum. Here we review some of the meridional circulation observations using local helioseismology techniques and relate them to magnetic flux transport models.

  19. Device for the acquisition and visualization in real time of the velocity and direction of wind in a radiological post stage

    International Nuclear Information System (INIS)

    Ledo P, L.M.; Guibert G, R.; Dominguez L, O.; Alonso A, D.; Ramos V, E.O.

    2006-01-01

    The work shows the development, construction and post stage of a device dedicated to the acquisition and transmission in real time of the information on the behavior of the meteorological variables: velocity and wind direction. It is introduced for the first time in an observation position the automatic monitoring, in real time, using the tools that it offers the digitalisation of the information and the computation. The obtained data are registered in a PC, its are visualized appropriately and can be objects of later analysis. It was developed the application program Autoclima for such purpose. (Author)

  20. Currents, Geostrophic, Aviso, 0.25 degrees, Global, Meridional

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Aviso Meridional Geostrophic Current is inferred from Sea Surface Height Deviation, climatological dynamic height, and basic fluid mechanics.

  1. South Atlantic meridional transports from NEMO-based simulations and reanalyses

    Science.gov (United States)

    Mignac, Davi; Ferreira, David; Haines, Keith

    2018-02-01

    The meridional heat transport (MHT) of the South Atlantic plays a key role in the global heat budget: it is the only equatorward basin-scale ocean heat transport and it sets the northward direction of the global cross-equatorial transport. Its strength and variability, however, are not well known. The South Atlantic transports are evaluated for four state-of-the-art global ocean reanalyses (ORAs) and two free-running models (FRMs) in the period 1997-2010. All products employ the Nucleus for European Modelling of the Oceans (NEMO) model, and the ORAs share very similar configurations. Very few previous works have looked at ocean circulation patterns in reanalysis products, but here we show that the ORA basin interior transports are consistently improved by the assimilated in situ and satellite observations relative to the FRMs, especially in the Argo period. The ORAs also exhibit systematically higher meridional transports than the FRMs, which is in closer agreement with observational estimates at 35 and 11° S. However, the data assimilation impact on the meridional transports still greatly varies among the ORAs, leading to differences up to ˜ 8 Sv and 0.4 PW in the South Atlantic Meridional Overturning Circulation and the MHTs, respectively. We narrow this down to large inter-product discrepancies in the western boundary currents (WBCs) at both upper and deep levels explaining up to ˜ 85 % of the inter-product differences in MHT. We show that meridional velocity differences, rather than temperature differences, in the WBCs drive ˜ 83 % of this MHT spread. These findings show that the present ocean observation network and data assimilation schemes can be used to consistently constrain the South Atlantic interior circulation but not the overturning component, which is dominated by the narrow western boundary currents. This will likely limit the effectiveness of ORA products for climate or decadal prediction studies.

  2. Superposed epoch analysis of vertical ion velocity, electron temperature, field-aligned current, and thermospheric wind in the dayside auroral region as observed by DMSP and CHAMP

    Science.gov (United States)

    Kervalishvili, G.; Lühr, H.

    2016-12-01

    This study reports on the results obtained by a superposed epoch analysis (SEA) method applied to the electron temperature, vertical ion velocity, field-aligned current (FAC), and thermospheric zonal wind velocity at high-latitudes in the Northern Hemisphere. The SEA study is performed in a magnetic latitude versus magnetic local time (MLat-MLT) frame. The obtained results are based on observations collected during the years 2001-2005 by the CHAMP and DMSP (F13 and F15) satellites. The dependence on interplanetary magnetic field (IMF) orientations is also investigated using data from the NASA/GSFC's OMNI database. Further, the obtained results are subdivided into three Lloyd seasons of 130 days each, which are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32days), and local summer (1 July ± 65 days). A period of 130 days is needed by the CHAMP satellite to pass through all local times. The time and location of the electron temperature peaks from CHAMP measurements near the cusp region are used as the reference parameter for the SEA method to investigate the relationship between the electron temperature and other ionospheric quantities. The SEA derived MLat profiles of the electron temperature show a seasonal dependence, increasing from winter to summer, as expected. But, the temperature rise (difference between the reference temperature peak and the background electron temperature) strongly decreases towards local summer. The SEA derived MLat profiles of the ion vertical velocity at DMSP altitude show the same seasonal behaviour as the electron temperature rice. There exists a clear linear relation between these two variables with a quiet large correlation coefficient value, >0.9. The SEA derived MLat profiles of both, thermospheric zonal wind velocity and FAC, show a clear IMF By orientation dependence for all local seasons. The zonal wind velocity is prominently directed towards west in the MLat-MLT frame

  3. Study on the Influence of Velocity, Turbulence Intensity and Temperature on Ammonia Emission Rate in a Wind Tunnel

    DEFF Research Database (Denmark)

    Rong, Li; Nielsen, P V; Zhang, Guo-Qiang

    2009-01-01

    Odor emissions from manure in livestock buildings are an important issue which concerns the human health and air quality as well as animals. Ammonia is one of the most important odors in pig houses. The objective of this paper is to investigate the influence of local velocity, turbulence intensit...

  4. Natural Surfactant Enrichments in the Atlantic Ocean Between 50°N and 50°S: Data from the Atlantic Meridional Transect, Oct-Nov 2014

    Science.gov (United States)

    Sabbaghzadeh, B.; Upstill-Goddard, R. C.; Nightingale, P. D.; Beale, R.

    2016-02-01

    Surfactants that decrease air-sea gas exchange by suppressing the gas transfer velocity (kw) show variable enrichments in the sea surface microlayer (SML) relative to the underlying water. This reflects variability in the rates of surfactant production and consumption. Total surfactant activity (SA: equivalent to Triton-X-100, mgL -1) was determined daily between the UK and the Falkland Islands, during cruise 24 of the Atlantic Meridional Transect programme (AMT 24). Samples were simultaneously obtained from the SML (Garrett screen), from the ship's underway system (inlet at 7m) and in hydrocasts to 500m. SA analysis was by hanging mercury drop electrode polarography (Metrohm 797 VA Computrace). SA enrichment factors (EF: SML SA / underlying water SA) >1 were observed at most locations, showing the SML to be consistently SA-enriched along the entire cruise transect. The persistence of these enrichments up to wind speeds 12m s-¹ support previous conclusions regarding the stability of the SML under high winds. More specifically, SA in the SML was up to four-fold higher in the Atlantic Northern Hemisphere than in the Atlantic Southern Hemisphere. Even so, EF values were not significantly different between the two hemispheres (p >0.05). These various findings have potentially important implications for kw variability across ocean basin scales.

  5. Evidence that a Deep Meridional Flow Sets the Sunspot Cycle Period

    Science.gov (United States)

    Hathaway, David H.; Nandy, D.; Wilson, R. M.; Reichmann, E. J.

    2003-01-01

    Sunspots appear on the Sun in two bands on either side of the equator that drift toward lower latitudes as each sunspot cycle progresses. We examine the equatorward drift of the centroid of the sunspot area in each hemisphere from 1874 to 2002 and find that the drift rate slows as the centroid approaches the equator. We compare the drift rate at sunspot cycle maximum to the cycle-period for each hemisphere and find a highly significant anti-correlation: hemispheres with faster drift rates have shorter periods. These observations are. consistent with an equatorward meridional counterflow, deep within the Sun, as the primary driver of the equatorward migration and the period associated with the sunspot cycle. We also find that the drift rate at maximum is significantly correlated with the amplitude of the following cycle, a prediction of dynamo models that employ a deep equatorward meridional flow. Our results indicate an amplitude of about 1.2 m/s for the meridional flow velocity at the base of the solar convection zone.

  6. UARS Wind Imaging Interferometer (WINDII) Level 3AL V011 (UARWI3AL) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — The Wind Imaging Interferometer (WINDII) Level 3AL data product consists of daily, 4 degree increment latitude-ordered vertical profiles of meridional and zonal wind...

  7. UARS Wind Imaging Interferometer (WINDII) Level 3AT V011 (UARWI3AT) at GES DISC

    Data.gov (United States)

    National Aeronautics and Space Administration — The Wind Imaging Interferometer (WINDII) Level 3AT data product consists of daily, 65.536 second interval time-ordered vertical profiles of meridional and zonal wind...

  8. Development of tunable high pressure CO2 laser for lidar measurements of pollutants and wind velocities, January 1976 to December 1977

    Science.gov (United States)

    Javan, A.

    1979-01-01

    A tunable multiatmospheric pulsed CO2 laser with emphasis on experimental features and supporting theoretical analyses important to differential absorption lidar and Doppler lidar measurement of pollutants and wind velocities is reported. The energy deposition and the means to produce the uniform high density plasma in the multiatmospheric medium, through UV preionization of an organic seed gas is discussed. Design features of the pulsed CO2 laser are presented. The radiative processes which are operative and prevent the laser from breaking into oscillations in a large number of modes over its broad amplification bandwidth are described. The mode competition for the transient pulsed laser oscillation in a standing wave and traveling wave ring laser configuration is discussed and contrasted with the approach to steady state oscillations. The latter findings are important to transient injection locking for production of a highly stable pulsed CO2 laser output.

  9. X-RAY HIGH-RESOLUTION SPECTROSCOPY REVEALS FEEDBACK IN A SEYFERT GALAXY FROM AN ULTRA-FAST WIND WITH COMPLEX IONIZATION AND VELOCITY STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Longinotti, A. L. [Catedrática CONACYT—Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis E. Erro 1, Tonantzintla, Puebla, C.P. 72840, México (Mexico); Krongold, Y. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apartado Postal 70264, 04510 Mexico D.F. (Mexico); Guainazzi, M.; Santos-Lleo, M.; Rodriguez-Pascual, P. [ESAC, P.O. Box, 78 E-28691 Villanueva de la Cañada, Madrid (Spain); Giroletti, M. [INAF Osservatorio di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Panessa, F. [INAF—Istituto di Astrofisica e Planetologia Spaziali di Roma (IAPS), Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Costantini, E. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands)

    2015-11-10

    Winds outflowing from active galactic nuclei (AGNs) may carry significant amounts of mass and energy out to their host galaxies. In this paper we report the detection of a sub-relativistic outflow observed in the narrow line Seyfert 1 galaxy IRAS 17020+4544 as a series of absorption lines corresponding to at least five absorption components with an unprecedented wide range of associated column densities and ionization levels and velocities in the range of 23,000–33,000 km s{sup −1}, detected at X-ray high spectral resolution (E/ΔE ∼ 1000) with the ESA's observatory XMM-Newton. The charge states of the material constituting the wind clearly indicate a range of low to moderate ionization states in the outflowing gas and column densities that are significantly lower than observed in highly ionized ultra-fast outflows. We estimate that at least one of the outflow components may carry sufficient energy to substantially suppress star formation and heat the gas in the host galaxy. IRAS 17020+4544 therefore provides an interesting example of feedback by a moderately luminous AGN that is hosted in a spiral galaxy, a case barely envisaged in most evolution models, which often predict that feedback processes take place in massive elliptical galaxies hosting luminous quasars in a post-merger phase.

  10. The role of the meridional sea surface temperature gradient in controlling the Caribbean low-level jet

    Science.gov (United States)

    Maldonado, Tito; Rutgersson, Anna; Caballero, Rodrigo; Pausata, Francesco S. R.; Alfaro, Eric; Amador, Jorge

    2017-06-01

    The Caribbean low-level jet (CLLJ) is an important modulator of regional climate, especially precipitation, in the Caribbean and Central America. Previous work has inferred, due to their semiannual cycle, an association between CLLJ strength and meridional sea surface temperature (SST) gradients in the Caribbean Sea, suggesting that the SST gradients may control the intensity and vertical shear of the CLLJ. In addition, both the horizontal and vertical structure of the jet have been related to topographic effects via interaction with the mountains in Northern South America (NSA), including funneling effects and changes in the meridional geopotential gradient. Here we test these hypotheses, using an atmospheric general circulation model to perform a set of sensitivity experiments to examine the impact of both SST gradients and topography on the CLLJ. In one sensitivity experiment, we remove the meridional SST gradient over the Caribbean Sea and in the other, we flatten the mountains over NSA. Our results show that the SST gradient and topography have little or no impact on the jet intensity, vertical, and horizontal wind shears, contrary to previous works. However, our findings do not discount a possible one-way coupling between the SST and the wind over the Caribbean Sea through friction force. We also examined an alternative approach based on barotropic instability to understand the CLLJ intensity, vertical, and horizontal wind shears. Our results show that the current hypothesis about the CLLJ must be reviewed in order to fully understand the atmospheric dynamics governing the Caribbean region.

  11. Erratum: Evidence That a Deep Meridional Flow Sets the Sunspot Cycle Period

    Science.gov (United States)

    Hathaway, David H.; Nandy, Dibyendu; Wilson, Robert M.; Reichmann, Edwin J.

    2004-01-01

    An error was made in entering the data. This changes the results concerning the length of the time lag between the variations in the meridional flow speed and those in the cycle amplitude. The final paragraph on page 667 should read: Finally, we study the relationship between the drift velocities and the amplitudes of the hemisphere/cycles. We compare the drift velocity at the maximum of the cycle to the amplitude of that cycle for that hemisphere. There is a positive (0.5) and significant (95%) correlation between the two. However, an even stronger relationship is found between the drift velocity and the amplitude of the N + 2 cycle. The correlation is stronger (0.7) and more significant (99%), as shown. This relationship is suggestive of a "memory" in the solar cycle, again a property of dynamo models that use meridional circulation. Indeed, the two-cycle lag is precisely the relationship found by Charbonneau & Dikpati. This behavior is, however, more difficult to interpret, and we elaborate on this in the next section. In either case, these correlations only explain part of the variance in cycle amplitude (25% for the current cycle and 50% for the N + 2 cycle). Obviously, other mechanisms, such as variations in the gradient in the rotation rate, also contribute to the cycle amplitude variations. Our investigation of possible connections between drift rates and the amplitudes of the N + 1 and N + 3 cycles gives no significant correlations at these alternative time lags.

  12. Demonstration and uncertainty analysis of synchronised scanning lidar measurements of 2D velocity fields in a boundary-layer wind tunnel

    OpenAIRE

    Dooren, Marijn F.; Campagnolo, Filippo; Sjöholm, Mikael; Angelou, Nikolas; Mikkelsen, Torben; Kühn, Martin

    2017-01-01

    This paper combines the research methodologies of scaled wind turbine model experiments in wind tunnels with short-range WindScanner lidar measurement technology. The wind tunnel at the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner lidars to demonstrate the benefits of synchronised scanning lidars in such experimental surroundings for the first time. The dual-lidar system can provide fully synchronised trajectory scans with sampling timescal...

  13. Dynamics of the Thermohaline Circulation under Wind forcing

    OpenAIRE

    Gao, Hongjun; Duan, Jinqiao

    2001-01-01

    The ocean thermohaline circulation, also called meridional overturning circulation, is caused by water density contrasts. This circulation has large capacity of carrying heat around the globe and it thus affects the energy budget and further affects the climate. We consider a thermohaline circulation model in the meridional plane under external wind forcing. We show that, when there is no wind forcing, the stream function and the density fluctuation (under appropriate metrics) tend to zero ex...

  14. Nonspherical Radiation Driven Wind Models Applied to Be Stars

    Science.gov (United States)

    Arauxo, F. X.

    1990-11-01

    ABSTRACT. In this work we present a model for the structure of a radiatively driven wind in the meridional plane of a hot star. Rotation effects and simulation of viscous forces were included in the motion equations. The line radiation force is considered with the inclusion of the finite disk correction in self-consistent computations which also contain gravity darkening as well as distortion of the star by rotation. An application to a typical BlV star leads to mass-flux ratios between equator and pole of the order of 10 and mass loss rates in the range 5.l0 to Mo/yr. Our envelope models are flattened towards the equator and the wind terminal velocities in that region are rather high (1000 Km/s). However, in the region near the star the equatorial velocity field is dominated by rotation. RESUMEN. Se presenta un modelo de la estructura de un viento empujado radiativamente en el plano meridional de una estrella caliente. Se incluyeron en las ecuaciones de movimiento los efectos de rotaci6n y la simulaci6n de fuerzas viscosas. Se consider6 la fuerza de las lineas de radiaci6n incluyendo la correcci6n de disco finito en calculos autoconsistentes los cuales incluyen oscurecimiento gravitacional asi como distorsi6n de la estrella por rotaci6n. La aplicaci6n a una estrella tipica BlV lleva a cocientes de flujo de masa entre el ecuador y el polo del orden de 10 de perdida de masa en el intervalo 5.l0 a 10 Mo/ano. Nuestros modelos de envolvente estan achatados hacia el ecuador y las velocidads terminales del viento en esa regi6n son bastante altas (1000 Km/s). Sin embargo, en la regi6n cercana a la estrella el campo de velocidad ecuatorial esta dominado por la rotaci6n. Key words: STARS-BE -- STARS-WINDS

  15. Oxygen variability and meridional oxygen supply in the tropical North East Atlantic oxygen minimum zone

    Science.gov (United States)

    Hahn, Johannes; Brandt, Peter; Greatbatch, Richard J.; Krahmann, Gerd; Körtzinger, Arne

    2013-04-01

    The oxygen minimum zone (OMZ) of the tropical North East Atlantic (TNEA) is located between the oxygen-rich equatorial region and the Cape Verde Frontal Zone at about 20°N in a depth range of 300 - 700 m. Its horizontal extent is predominantly defined by the North Equatorial Current and by the equatorial zonal current system ventilating the region to the north and south of the OMZ, respectively. The interior of the OMZ is characterized by a sluggish flow regime, where mesoscale eddies play a major role in the ventilation. In this study we focus on the oxygen variability in the TNEA as well as the eddy driven lateral ventilation of the TNEA OMZ across its southern boundary. During recent years an intense measurement program was executed along 23°W cutting meridionally through the TNEA OMZ. Hydrographic and velocity data has been acquired from ship sections and moorings, together covering the latitude range between 6°S and 14°N with particularly high meridional resolution of shipboard and high temporal resolution of moored observations. Based on shipboard data we derived a meridional section of oxygen variance, which reveals numerous local maxima of oxygen variability. Exemplary, strong oxygen variability is observed at the upper (300m, 5° - 12°N) and the southern boundary (400m - 700m, 5°N - 8°N) of the OMZ, whereas the interior of the OMZ is characterized by weak variability. An application of the extended Osborn-Cox model shows that the strong oxygen variability at the southern boundary is mainly generated by mesoscale eddies. The strong variability at the upper boundary is generated by mesoscale eddies as well as microscale turbulence. We apply two methods to estimate the meridional oxygen flux: 1) a flux gradient parameterization and 2) a correlation of oxygen and velocity mooring time series. From the analysis of the 5°N mooring data we find a northward oxygen flux directed towards the OMZ at its core depth, that is mainly due to variability of

  16. Meridional flow and differential rotation by gravity darkening in fast rotating solar-type stars

    Science.gov (United States)

    Rüdiger, G.; Küker, M.

    2002-04-01

    An explanation is presented for the rather strong total surface differential rotation of the observed very young solar-type stars like AB Dor and PZ Tel. Due to its rapid rotation, a non-uniform energy flux leaves the stellar core so that the outer convection zone is non-uniformly heated from below. Due to this ``gravity darkening'' of the equator, a meridional flow is created flowing equatorwards at the surface and thus accelerating the equatorial rotation. The effect linearly grows with the normalized pole-equator difference, epsilon , of the heat-flux at the bottom of the convection zone. A rotation rate of about 9 h leads to epsilon =0.1 for a solar-type star. In this case the resulting equator-pole differences of the angular velocity at the stellar surface, delta Omega , varies from unobservable 0.005 day-1 to the (desired) value of 0.03 day-1 when the dimensionless diffusivity factors cnu and cchi vary between 1 and 0.1 (standard value cnu =~ cchi =~ 0.3, see Table \\ref{tab1}). In all cases the related temperature differences between pole and equator at the surface are unobservably small. The (clockwise) meridional circulation which we obtain flows opposite to the (counterclockwise) circulation appearing as a byproduct in the Lambda -theory of the non-uniform rotation in outer convection zones. The consequences of this situation for those dynamo theories of stellar activity are discussed that work with the meridional circulation as the dominant magnetic-advection effect in latitude to produce the solar-like form of the butterfly diagram.

  17. A modelling study of the Bjerknes compensation in the meridional heat transport in a freshening ocean

    Directory of Open Access Journals (Sweden)

    Haijun Yang

    2013-05-01

    Full Text Available The compensation between the meridional heat transports in the atmosphere and ocean is studied through a coupled model's water-hosing experiments. It is found that the atmospheric heat transport (AHT change compensates the oceanic heat transport (OHT change very well in the extratropics, while the former over-compensates the latter in the tropics. Similar to previous studies, the fresh water input in the high latitude Atlantic weakens the Atlantic meridional overturning circulation and thus the northward Atlantic OHT significantly, leading to a warming (cooling in sea surface temperature in the Southern (Northern Hemisphere and in turn a southward shift of atmospheric convection. This results in an enhanced Hadley Cell (HC and stronger northward AHT, compensating the reduced Atlantic OHT. Meanwhile, the wind-driven Subtropical Cell in the Indo-Pacific oceans is enhanced in response to the HC change, increasing the northward OHT in the Indo-Pacific, which partly offsets the reduced OHT in the Atlantic. The response in the Indo-Pacific is responsible for the overcompensation of the AHT to the global OHT. The Held's mechanism works very well in the tropical Indo-Pacific in our experiments. This is substantially different from previous studies.

  18. Assessing the vegetation canopy influences on wind flow using wind ...

    Indian Academy of Sciences (India)

    The effectiveness of vegetation in reducing wind ... Wind erosion; roughness length; shear velocity ratio; shear stress ratio; roughness density; wind tunnel. J. Earth .... flow direction induced by its kinematic viscosity. An increase in shear stress causes a proportional increase in the height-dependent change in wind velocity.

  19. Wind energy in Mediterranean Basin

    International Nuclear Information System (INIS)

    Gaudiosi, G.

    1991-01-01

    In its examination of wind energy potential in the Mediterranean Basin, this paper provides brief notes on the Basin's geography; indicates power production and demand; describes the area's wind characteristics and wind monitoring activities; illustrates wind velocity distributions; estimates local wind power production potential; reviews the Basin's wind energy marketing situation and each bordering country's wind energy programs; surveys installed wind energy farms; and assesses national research and commercialization efforts

  20. AIRS observations of seasonal variability in meridional temperature ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 122; Issue 1. AIRS observations of seasonal variability in meridional temperature gradient over Indian region at 100 hPa. A Gupta S K Dhaka V Panwar R Bhatnagar V Kumar Savita M Datta S K Dash. Volume 122 Issue 1 February 2013 pp 201-213 ...

  1. Link between convection and meridional gradient of sea surface ...

    Indian Academy of Sciences (India)

    . Resolution. URL. SST. TMI ... In this paper, we use satellite data for SST and rainfall to show that there exists a strong relationship between convec- tion and the meridional gradient of SST in the bay. We show that convection sets in within a ...

  2. AIRS observations of seasonal variability in meridional temperature ...

    Indian Academy of Sciences (India)

    Meridional temperature gradient; Atmospheric Infra Red Sounder (AIRS) data; Indian summer monsoon; .... fine scale earlier in this region, due to paucity of data. 2. Data. We have used AIRS (AIRX3STM) version 5 level. 3 research quality product (http://airs.jpl.nasa. ..... regional information as we are presenting in this.

  3. Mean winds in the MLT, the SQBO and MSAO over Ascension Island (8° S, 14° W

    Directory of Open Access Journals (Sweden)

    K. A. Day

    2013-09-01

    Full Text Available Mean winds in the mesosphere and lower thermosphere (MLT over Ascension Island (8° S, 14° W have been measured at heights of approximately 80–100 km by a meteor radar. The results presented in this study are from the interval October 2001 to December 2011. In all years, the monthly-mean meridional winds display a clear annual oscillation. Typically, these winds are found to be southward during April–October, when they reach velocities of up to about −23 m s−1, and northward throughout the rest of the year, when they reach velocities up to about 16 m s−1. The monthly-mean zonal winds are generally westward throughout most of the year and reach velocities of up to about −46 m s−1. However, eastward winds are observed in May–August and again in December at the lower heights observed. These eastward winds reach a maximum at heights of about 86 km with velocities of up to about 36 m s−1, but decay quickly at heights above and below that level. The mesospheric semi-annual oscillation (MSAO is clearly apparent in the observed monthly-mean zonal winds. The winds in first westward phase of the MSAO are observed to be much stronger than in the second phase. The westward phase of the MSAO is found to maximise at heights of about 84 km with typical first-phase wind velocities reaching about −35 m s−1. These meteor-radar observations have been compared to the HWM-07 empirical model. The observed meridional winds are found to be generally more southward than those of the model during May–August, when at the lower heights observed the model suggests there will be only weakly southward, or even northward, winds. The zonal monthly-mean winds are in generally good agreement, although in the model they are somewhat less westward than those observed. Throughout the observations there were eight occasions in which the first westward phase of the MSAO was observed. Strikingly, in 2002 there was an event in which the westward winds during the

  4. Demonstration and uncertainty analysis of synchronised scanning lidar measurements of 2-D velocity fields in a boundary-layer wind tunnel

    Directory of Open Access Journals (Sweden)

    M. F. van Dooren

    2017-06-01

    Full Text Available This paper combines the research methodologies of scaled wind turbine model experiments in wind tunnels with short-range WindScanner lidar measurement technology. The wind tunnel at the Politecnico di Milano was equipped with three wind turbine models and two short-range WindScanner lidars to demonstrate the benefits of synchronised scanning lidars in such experimental surroundings for the first time. The dual-lidar system can provide fully synchronised trajectory scans with sampling timescales ranging from seconds to minutes. First, staring mode measurements were compared to hot-wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u and v components of the wind speed, respectively, validating the 2-D measurement capability of the lidar scanners. Subsequently, the measurement of wake profiles on a line as well as wake area scans were executed to illustrate the applicability of lidar scanning to the measurement of small-scale wind flow effects. An extensive uncertainty analysis was executed to assess the accuracy of the method. The downsides of lidar with respect to the hot-wire probes are the larger measurement probe volume, which compromises the ability to measure turbulence, and the possible loss of a small part of the measurements due to hard target beam reflection. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning and the fact that remote sensing techniques do not disturb the flow during measuring. The research campaign revealed a high potential for using short-range synchronised scanning lidars to measure the flow around wind turbines in a wind tunnel and increased the knowledge about the corresponding uncertainties.

  5. Program to determine space vehicle response to wind turbulence

    Science.gov (United States)

    Wilkening, H. D.

    1972-01-01

    Computer program was developed as prelaunch wind monitoring tool for Saturn 5 vehicle. Program accounts for characteristic wind changes including turbulence power spectral density, wind shear, peak wind velocity, altitude, and wind direction using stored variational statistics.

  6. Extreme winds in Denmark

    DEFF Research Database (Denmark)

    Kristensen, L.; Rathmann, O.; Hansen, S.O.

    2000-01-01

    ), Kegnaes (7 yr), Sprogo (20 yr), and Tystofte (16 yr). The measured data are wind speed, wind direction, temperature and pressure. The wind records are cleaned for terrain effects by means of WASP (Mortensew ct al., Technical Report I-666 (EN), Riso National Laboratory, 1993. Vol. 2. User's Guide......): assuming geostrophic balance, all the wind-velocity data are transformed to friction velocity u(*) and direction at standard conditions by means of the geostrophic drag law for neutral stratification. The basic wind velocity in 30 degrees sectors are obtained through ranking of the largest values...... of the friction velocity pressure pu(*)(2)/2 taken once every two months. The main conclusion is that the basic wind velocity is significantly larger at the west coast of Jutland (25 +/- 1 m/s) than at any of the other sites (22 +/- 1 m/s). These results are in agreement with those obtained by Jensen and Franck...

  7. Meridional Motions and Reynolds Stress Determined by Using Kanzelhöhe Drawings and White Light Solar Images from 1964 to 2016

    Science.gov (United States)

    Ruždjak, Domagoj; Sudar, Davor; Brajša, Roman; Skokić, Ivica; Poljančić Beljan, Ivana; Jurdana-Šepić, Rajka; Hanslmeier, Arnold; Veronig, Astrid; Pötzi, Werner

    2018-04-01

    Sunspot position data obtained from Kanzelhöhe Observatory for Solar and Environmental Research (KSO) sunspot drawings and white light images in the period 1964 to 2016 were used to calculate the rotational and meridional velocities of the solar plasma. Velocities were calculated from daily shifts of sunspot groups and an iterative process of calculation of the differential rotation profiles was used to discard outliers. We found a differential rotation profile and meridional motions in agreement with previous studies using sunspots as tracers and conclude that the quality of the KSO data is appropriate for analysis of solar velocity patterns. By analyzing the correlation and covariance of meridional velocities and rotation rate residuals we found that the angular momentum is transported towards the solar equator. The magnitude and latitudinal dependence of the horizontal component of the Reynolds stress tensor calculated is sufficient to maintain the observed solar differential rotation profile. Therefore, our results confirm that the Reynolds stress is the dominant mechanism responsible for transport of angular momentum towards the solar equator.

  8. Atlantic Meridional Overturning Circulation slowdown cooled the subtropical ocean.

    Science.gov (United States)

    Cunningham, Stuart A; Roberts, Christopher D; Frajka-Williams, Eleanor; Johns, William E; Hobbs, Will; Palmer, Matthew D; Rayner, Darren; Smeed, David A; McCarthy, Gerard

    2013-12-16

    [1] Observations show that the upper 2 km of the subtropical North Atlantic Ocean cooled throughout 2010 and remained cold until at least December 2011. We show that these cold anomalies are partly driven by anomalous air-sea exchange during the cold winters of 2009/2010 and 2010/2011 and, more surprisingly, by extreme interannual variability in the ocean's northward heat transport at 26.5°N. This cooling driven by the ocean's meridional heat transport affects deeper layers isolated from the atmosphere on annual timescales and water that is entrained into the winter mixed layer thus lowering winter sea surface temperatures. Here we connect, for the first time, variability in the northward heat transport carried by the Atlantic Meridional Overturning Circulation to widespread sustained cooling of the subtropical North Atlantic, challenging the prevailing view that the ocean plays a passive role in the coupled ocean-atmosphere system on monthly-to-seasonal timescales.

  9. Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene

    OpenAIRE

    Burls, Natalie J.; Fedorov, Alexey V.; Sigman, Daniel M.; Jaccard, Samuel L.; Tiedemann, Ralf; Haug, Gerald H.

    2017-01-01

    An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, theworld's largest ocean, where relatively fresh surface waters inhibitNorth Pacific deep convection. We present complementary measurement and modeling evidence that the warm, similar to 400-ppmv (parts per million by volume) CO2 world ...

  10. Statistical modeling of temperature, humidity and wind fields in the atmospheric boundary layer over the Siberian region

    Science.gov (United States)

    Lomakina, N. Ya.

    2017-11-01

    The work presents the results of the applied climatic division of the Siberian region into districts based on the methodology of objective classification of the atmospheric boundary layer climates by the "temperature-moisture-wind" complex realized with using the method of principal components and the special similarity criteria of average profiles and the eigen values of correlation matrices. On the territory of Siberia, it was identified 14 homogeneous regions for winter season and 10 regions were revealed for summer. The local statistical models were constructed for each region. These include vertical profiles of mean values, mean square deviations, and matrices of interlevel correlation of temperature, specific humidity, zonal and meridional wind velocity. The advantage of the obtained local statistical models over the regional models is shown.

  11. Techno-Economic and dynamic analysis of low velocity wind turbines for rural electrification in agricultural area of Ratchaburi Province, Thailand

    Science.gov (United States)

    Lipirodjanapong, Sumate; Namboonruang, Weerapol

    2017-07-01

    This paper presents the analysis of potential wind speed of electrical power generating using for agriculture in Ratchaburi province, Thailand. The total area is 1,900 square kilometers. First of all, the agriculture electrical load (AEL) data was investigated from all farming districts in Ratchaburi. Subsequently, the load data was analyzed and classified by the load power and energy consumption at individual district. The wind turbine generator (WTG) at capacity rate of 200w, 500w, 1,000w, and 2,000w were adopted to implement for the AEL in each area at wind speed range of 3 to 6 m/s. This paper shows the approach based on the wind speed at individual district to determine the capacity of WTG using the capacitor factor (CF) and the cost of energy (COE) in baht per unit under different WTG value rates. Ten locations for wind station installations are practical investigated. Results show that for instance, the Damnoen Sa-duak (DN-04) one of WTG candidate site is identically significant for economic investment of installing rated WTG. The results of COE are important to determine whether a wind site is good or not.

  12. Added damping of a wind turbine rotor : Two-dimensional discretization expressing the nonlinear wind-force dependency

    NARCIS (Netherlands)

    Van der Male, P.; Van Dalen, K.N.; Metrikine, A.

    2014-01-01

    In determining wind forces on wind turbine blades, and subsequently on the tower and the foundation, the blade response velocity cannot be neglected. This velocity alters the wind force, which depends on the wind velocity relative to that of the blades This blade response velocity component of the

  13. Extreme winds in Denmark

    DEFF Research Database (Denmark)

    Kristensen, L.; Rathmann, O.; Hansen, S.O.

    1999-01-01

    Wind-speed data from four sites in Denmark have been analyzed in order to obtain estimates of the basic wind velocity, defined as the 50-year wind speed (ten minute averages) under standard conditions, i.e. 10 meter over a homogeneous terrain with the roughness length 0.05 m. The sites are Skjern...

  14. Extreme winds in Denmark

    DEFF Research Database (Denmark)

    Kristensen, L.; Rathmann, Ole; Hansen, S.O.

    1999-01-01

    Wind-speed data from four sites in Denmark have been analyzed in order to obtain estimates of the basic wind velocity which is defined as the 50-year wind speed under standard conditions, i.e. ten-minute averages at the height 10 m over a uniform terrainwith the roughness length 0.05 m. The sites...

  15. Peran Kecepatan Angin Terhadap Peningkatan Kenyamanan Termis Manusia Di Lingkungan Beriklim Tropis Lembab (the Role of Wind Velocity on Increasing Human Thermal Comfort in Hot and Humid Environment)

    OpenAIRE

    Sangkertadi, Sangkertadi

    2006-01-01

    The most important factors which influence the condition of thermal comfort are clothing, temperature, humidity, air velocity, and types of activities. In hot and humid climate, feeling of comfort are associated with sweating. Air velocity can cool building occupants by increasing convective and evaporative heat loses. This paper intends to explore the techniques for evaluating of thermal comfort especially with introduction of PMV and DISC scales for the tropical humid environment. The study...

  16. Gas dynamics in the inner few AU around the Herbig B[e] star MWC297. Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging

    Science.gov (United States)

    Hone, Edward; Kraus, Stefan; Kreplin, Alexander; Hofmann, Karl-Heinz; Weigelt, Gerd; Harries, Tim; Kluska, Jacques

    2017-10-01

    Aims: Circumstellar accretion disks and outflows play an important role in star formation. By studying the continuum and Brγ-emitting region of the Herbig B[e] star MWC297 with high-spectral and high-spatial resolution we aim to gain insight into the wind-launching mechanisms in young stars. Methods: We present near-infrared AMBER (R = 12 000) and CRIRES (R = 100 000) observations of the Herbig B[e] star MWC297 in the hydrogen Brγ-line. Using the VLTI unit telescopes, we obtained a uv-coverage suitable for aperture synthesis imaging. We interpret our velocity-resolved images as well as the derived two-dimensional photocenter displacement vectors, and fit kinematic models to our visibility and phase data in order to constrain the gas velocity field on sub-AU scales. Results: The measured continuum visibilities constrain the orientation of the near-infrared-emitting dust disk, where we determine that the disk major axis is oriented along a position angle of 99.6 ± 4.8°. The near-infrared continuum emission is 3.6 × more compact than the expected dust-sublimation radius, possibly indicating the presence of highly refractory dust grains or optically thick gas emission in the inner disk. Our velocity-resolved channel maps and moment maps reveal the motion of the Brγ-emitting gas in six velocity channels, marking the first time that kinematic effects in the sub-AU inner regions of a protoplanetary disk could be directly imaged. We find a rotation-dominated velocity field, where the blue- and red-shifted emissions are displaced along a position angle of 24° ± 3° and the approaching part of the disk is offset west of the star. The visibility drop in the line as well as the strong non-zero phase signals can be modeled reasonably well assuming a Keplerian velocity field, although this model is not able to explain the 3σ difference that we measure between the position angle of the line photocenters and the position angle of the dust disk. We find that the fit can be

  17. Active Pacific meridional overturning circulation (PMOC) during the warm Pliocene.

    Science.gov (United States)

    Burls, Natalie J; Fedorov, Alexey V; Sigman, Daniel M; Jaccard, Samuel L; Tiedemann, Ralf; Haug, Gerald H

    2017-09-01

    An essential element of modern ocean circulation and climate is the Atlantic meridional overturning circulation (AMOC), which includes deep-water formation in the subarctic North Atlantic. However, a comparable overturning circulation is absent in the Pacific, the world's largest ocean, where relatively fresh surface waters inhibit North Pacific deep convection. We present complementary measurement and modeling evidence that the warm, ~400-ppmv (parts per million by volume) CO 2 world of the Pliocene supported subarctic North Pacific deep-water formation and a Pacific meridional overturning circulation (PMOC) cell. In Pliocene subarctic North Pacific sediments, we report orbitally paced maxima in calcium carbonate accumulation rate, with accompanying pigment and total organic carbon measurements supporting deep-ocean ventilation-driven preservation as their cause. Together with high accumulation rates of biogenic opal, these findings require vigorous bidirectional communication between surface waters and interior waters down to ~3 km in the western subarctic North Pacific, implying deep convection. Redox-sensitive trace metal data provide further evidence of higher Pliocene deep-ocean ventilation before the 2.73-Ma (million years) transition. This observational analysis is supported by climate modeling results, demonstrating that atmospheric moisture transport changes, in response to the reduced meridional sea surface temperature gradients of the Pliocene, were capable of eroding the halocline, leading to deep-water formation in the western subarctic Pacific and a strong PMOC. This second Northern Hemisphere overturning cell has important implications for heat transport, the ocean/atmosphere cycle of carbon, and potentially the equilibrium response of the Pacific to global warming.

  18. Los testimonios de Marte en la Meseta Meridional

    Directory of Open Access Journals (Sweden)

    Julián Hurtado Aguña

    2001-01-01

    Full Text Available Marte, fue una de las más importantes divinidades romanas presentes en Híspanla. Dentro de la Meseta meridional sus testimonios aparecen en algunas localidades de la provincia de Madrid, como Alcalá de Henares, Talamanca del Jarama o Collado Villalba, estando ausentes en otras partes de esta región. Especialmente importante es la presencia de inscripciones dedicadas a Marte en la ciudad romana de Complutum (Alcalá de Henares, donde sus dedicantes pudieran pertenecer en algún caso al grupo social de los libertos.One oí the most important román divinities in Híspanla was Mars. His testimonies in the Meridional Plateau are in some villages of Madrid's province, as Alcalá de Henares, Talamanca del Jarama or Collado Villalba, and they are not in other places of this reglan. Specially important is ttie presence of inscriptions to Mars in ttie román town of Complutum (Alcalá de Henares, wtiere his devotes could belong to the social freedmans group.

  19. Radial Transport and Meridional Circulation in Accretion Disks

    Energy Technology Data Exchange (ETDEWEB)

    Philippov, Alexander A. [Department of Astrophysical Sciences, Princeton University, Ivy Lane, Princeton, NJ 08540 (United States); Rafikov, Roman R., E-mail: sashaph@princeton.edu [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States)

    2017-03-10

    Radial transport of particles, elements and fluid driven by internal stresses in three-dimensional (3D) astrophysical accretion disks is an important phenomenon, potentially relevant for the outward dust transport in protoplanetary disks, origin of the refractory particles in comets, isotopic equilibration in the Earth–Moon system, etc. To gain better insight into these processes, we explore the dependence of meridional circulation in 3D disks with shear viscosity on their thermal stratification, and demonstrate a strong effect of the latter on the radial flow. Previous locally isothermal studies have normally found a pattern of the radial outflow near the midplane, switching to inflow higher up. Here we show, both analytically and numerically, that a flow that is inward at all altitudes is possible in disks with entropy and temperature steeply increasing with height. Such thermodynamic conditions may be typical in the optically thin, viscously heated accretion disks. Disks in which these conditions do not hold should feature radial outflow near the midplane, as long as their internal stress is provided by the shear viscosity. Our results can also be used for designing hydrodynamical disk simulations with a prescribed pattern of the meridional circulation.

  20. PERAN KECEPATAN ANGIN TERHADAP PENINGKATAN KENYAMANAN TERMIS MANUSIA DI LINGKUNGAN BERIKLIM TROPIS LEMBAB (The Role of Wind Velocity on Increasing Human Thermal Comfort in Hot and Humid Environment

    Directory of Open Access Journals (Sweden)

    Sangkertadi Sangkertadi

    2006-07-01

    Full Text Available ABSTRAK Faktor utama yang mempengaruhi persepsi kenyamanan termis pada manusia adalah : pakaian, suhu, kelembaban dan kecepatan udara sekitar, serta jenis aktivitasnya. Di daerah beriklim panas dan lembab, rasa tidak nyaman berkaitan erat dengan keluarnya keringat. Angin dengan debit dan kecepatan tertentu dapat difungsikan untuk mendinginkan penghuni bangunan melalui proses evaporasi keringat dan proses perpindahan kalor secara konvektif. Tulisan ini menyajikan pendalaman tentang teknik mengevaluasi tingkat kenyamanan termis manusia di daerah beriklim tropis lembab khususnya dengan menggunakan skala DISC dan PMV. Studi ini difokuskan pada pengaruh kecepatan angin untuk meningkatkan kenyamanan termis manusia. Metode yang dipakai adalah simulasi numerik dengan menggunakan sejumlah persamaan praktis untuk penghitungan kenyamanan termis.   ABSTRACT The most important factors which influence the condition of thermal comfort are clothing, temperature, humidity, air velocity, and types of activities. In hot and humid climate, feeling of comfort are associated with sweating. Air velocity can cool building occupants by increasing convective and evaporative heat loses. This paper intends to explore the techniques for evaluating of thermal comfort especially with introduction of PMV and DISC scales for the tropical humid environment. The study is focused on the influence of air velocity to the scale number of both DSC and PMV. A simple numerical simulation with some of empirical correlations are used to estimate the index of thermal comfort

  1. Anelastic Models of Fully-Convective Stars: Differential Rotation, Meridional Circulation and Residual Entropy

    Science.gov (United States)

    Sainsbury-Martinez, Felix; Browning, Matthew; Miesch, Mark; Featherstone, Nicholas A.

    2018-01-01

    Low-Mass stars are typically fully convective, and as such their dynamics may differ significantly from sun-like stars. Here we present a series of 3D anelastic HD and MHD simulations of fully convective stars, designed to investigate how the meridional circulation, the differential rotation, and residual entropy are affected by both varying stellar parameters, such as the luminosity or the rotation rate, and by the presence of a magnetic field. We also investigate, more specifically, a theoretical model in which isorotation contours and residual entropy (σ‧ = σ ‑ σ(r)) are intrinsically linked via the thermal wind equation (as proposed in the Solar context by Balbus in 2009). We have selected our simulation parameters in such as way as to span the transition between Solar-like differential rotation (fast equator + slow poles) and ‘anti-Solar’ differential rotation (slow equator + fast poles), as characterised by the convective Rossby number and △Ω. We illustrate the transition from single-celled to multi-celled MC profiles, and from positive to negative latitudinal entropy gradients. We show that an extrapolation involving both TWB and the σ‧/Ω link provides a reasonable estimate for the interior profile of our fully convective stars. Finally, we also present a selection of MHD simulations which exhibit an almost unsuppressed differential rotation profile, with energy balances remaining dominated by kinetic components.

  2. A finite volume code for meridional circulation in stars

    CERN Document Server

    Talon, S; Michaud, G; Richer, J

    2003-01-01

    To understand the driving of both meridional circulation and differential rotation in radiative envelopes of stars, one has to solve for 3D mass, momentum, and energy conservation equations for a compressible gas in a central gravity field. In this study, we propose a novel finite volume technique that uses Cartesian geometry thus reducing greatly the complexity of spherical operators. The boundary conditions are efficiently imposed at the surface of the star using the fictitious points technique. We use the anelastic approximation and the Poisson equation for pressure is solved by the Jacobi method which preserves natural symmetries. We present analytical test cases of the fictitious domain technique, and show our results of asymptotic circulation in a model with little stratification and a large viscosity.

  3. Effects of solar proton events in the mesosphere/lower thermosphere region according to the data of meteo radar wind measurements at high and middle latitudes

    Science.gov (United States)

    Trifonov, A. N.; Makarov, N. A.; Merzlyakov, E. G.

    2016-03-01

    Data from meteo radar measurements of the wind in the mesosphere/lower thermosphere region at high latitudes of the Southern Hemisphere (Molodezhnaya station, 68° S, 45° E) and at middle latitudes of the Northern Hemisphere (Obninsk station, 55° N, 37° E) during solar proton events that took place in 1989, 1991, 2000, 2005, and 2012 are analyzed in the paper. In 1989 and 1991, we succeeded in observing the response to solar proton evens at both stations simultaneously. The results show that solar proton events lead to a change in the wind regime of the mesosphere and lower thermosphere. At high latitudes of the Southern Hemisphere, significant changes are observed in the values of the velocities of the meridional and zonal components of the prevailing wind. In the case of powerful solar proton events, the amplitude of the semidiurnal tide grows in the vicinity of the proton flux maximum. The response to these events depends on the season. The reaction of the prevailing wind at middle latitudes shows the same features as the reaction of the wind at high latitudes. However no unambiguous response of the tide amplitude is observed. In the summer season, even powerful events (for example, in July 2000) cause no changes in the wind regime parameters in the midlatitude region of the mesosphere/lower thermosphere.

  4. Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas

    Directory of Open Access Journals (Sweden)

    F. Fécan

    1999-01-01

    Full Text Available Large-scale simulation of the soil-derived dust emission in semi-arid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (characterized by the moisture tension are the main factor responsible for the increase of the wind erosion threshold observed when the soil moisture increases. When the soil moisture content is close to but smaller than the maximum amount of adsorbed water, w' (depending on the soil texture, these capillary forces are considered as not strong enough to significantly increase the erosion threshold. An expression of the moisture tension as a function of soil moisture and w' is derived from retention curves. From this expression, a parametrization of the ratio of the wet to dry erosion thresholds has been developed as a function of soil moisture and soil texture. The coefficients of this parametrization have been determined by using experimental data from the literature. An empirical relationship between w' and soil clay content has been established. The erosion threshold ratios simulated for different soil textures were found to be in good agreement with the experimental data.Key words. Atmospheric composition and structure (Aerosols and particles · Hydrology (soil moisture

  5. Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas

    Energy Technology Data Exchange (ETDEWEB)

    Fecan, F.; Marticorena, B.; Bergametti, G. [Paris-7 Univ. (France). Lab. Interuniversitaire des Systemes Atmospheriques

    1999-01-01

    Large-scale simulation of the soil-derived dust emission in semiarid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (characterized by the moisture tension) are the main factor responsible for the increase of the wind erosion threshold observed when the soil moisture increases. When the soil moisture content is close to but smaller than the maximum amount of adsorbed water, w` (depending on the soil texture), these capillary forces are considered as not strong enough to significantly increase the erosion threshold. An expression of the moisture tension as a function of soil moisture and w` is derived from retention curves. From this expression, a parametrization of the ratio of the wet to dry erosion thresholds has been developed as a function of soil moisture and soil texture. The coefficients of this parametrization have been determined by using experimental data from the literature. An empirical relationship between w` and soil clay content has been established. The erosion threshold ratios simulated for different soil textures were found to be in good agreement with the experimental data. (orig.) 24 refs.

  6. Parametrization of the increase of the aeolian erosion threshold wind friction velocity due to soil moisture for arid and semi-arid areas

    Directory of Open Access Journals (Sweden)

    F. Fécan

    Full Text Available Large-scale simulation of the soil-derived dust emission in semi-arid regions needs to account for the influence of the soil moisture on the wind erosion threshold. Soil water retention consists of molecular adsorption on the soil grain surface and capillary forces between the grain. Interparticle capillary forces (characterized by the moisture tension are the main factor responsible for the increase of the wind erosion threshold observed when the soil moisture increases. When the soil moisture content is close to but smaller than the maximum amount of adsorbed water, w' (depending on the soil texture, these capillary forces are considered as not strong enough to significantly increase the erosion threshold. An expression of the moisture tension as a function of soil moisture and w' is derived from retention curves. From this expression, a parametrization of the ratio of the wet to dry erosion thresholds has been developed as a function of soil moisture and soil texture. The coefficients of this parametrization have been determined by using experimental data from the literature. An empirical relationship between w' and soil clay content has been established. The erosion threshold ratios simulated for different soil textures were found to be in good agreement with the experimental data.

    Key words. Atmospheric composition and structure (Aerosols and particles · Hydrology (soil moisture

  7. Wind, QuikSCAT SeaWinds, 0.25 degrees, Global, Science Quality, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Remote Sensing Inc. distributes science quality wind velocity data from the SeaWinds instrument onboard NASA's QuikSCAT satellite. SeaWinds is a microwave...

  8. Wind turbine

    Science.gov (United States)

    Cheney, Jr., Marvin C.

    1982-01-01

    A wind turbine of the type having an airfoil blade (15) mounted on a flexible beam (20) and a pitch governor (55) which selectively, torsionally twists the flexible beam in response to wind turbine speed thereby setting blade pitch, is provided with a limiter (85) which restricts unwanted pitch change at operating speeds due to torsional creep of the flexible beam. The limiter allows twisting of the beam by the governor under excessive wind velocity conditions to orient the blades in stall pitch positions, thereby preventing overspeed operation of the turbine. In the preferred embodiment, the pitch governor comprises a pendulum (65,70) which responds to changing rotor speed by pivotal movement, the limiter comprising a resilient member (90) which engages an end of the pendulum to restrict further movement thereof, and in turn restrict beam creep and unwanted blade pitch misadjustment.

  9. Meridional circulation in rotating stars. VII. The effects of chemical inhomogeneities

    International Nuclear Information System (INIS)

    Tassoul, M.; Tassoul, J.

    1984-01-01

    In this paper we discuss the effects of a gradient of mean molecular weight μ on the rotationally driven currents that pervade the radiative zone of a single, nonmagnetic, main-sequence star. Detailed numerical calculations are made for the hydrogen-burning core of a solar-type star, assuming that departures from spherical symmetry are not too large. It is found that meridional streaming virtually dies out from the center outward as the μ-gradient grows in a leisurely fashion. This prevents a substantial mixing of matter between the inner (inhomogeneous) and outer (homogeneous) regions in the radiative zone, although the inner region may be penetrated to some degree. To first order in the ratio of the centrifugal force to gravity at the equator, this pattern of circulation is independent of the mean angular velocity. To this order, then, there is no critical rotation rate above which unimpeded mixing may take place. These quantitative results are compared with diverse statements that can be found in the phenomenological literature on rotational mixing

  10. Demonstration and uncertainty analysis of synchronised scanning lidar measurements of 2-D velocity fields in a boundary-layer wind tunnel

    DEFF Research Database (Denmark)

    van Dooren, Marijn Floris; Campagnolo, Filippo; Sjöholm, Mikael

    2017-01-01

    to demonstrate the benefits of synchronised scanning lidars in such experimental surroundings for the first time. The duallidar system can provide fully synchronised trajectory scans with sampling timescales ranging from seconds to minutes. First, staring mode measurements were compared to hot-wire probe...... as wake area scans were executed to illustrate the applicability of lidar scanning to the measurement of small-scale wind flow effects. An extensive uncertainty analysis was executed to assess the accuracy of the method. The downsides of lidar with respect to the hotwire probes are the larger measurement...... probe volume, which compromises the ability to measure turbulence, and the possible loss of a small part of the measurements due to hard target beam reflection. In contrast, the benefits are the high flexibility in conducting both point measurements and area scanning and the fact that remote sensing...

  11. Interannual to Decadal Variability of Meridional Transports Across the SAMOC Basin Wide Array (SAMBA) in Simulations with an Eddy-resolving Global Ocean Model

    Science.gov (United States)

    Campos, E. J.; Ambrizzi, T.

    2016-02-01

    Results of numerical experiments with ocean general circulation models show increasing trends in the Agulhas leakage and in the meridional heat transport in the South Atlantic. To further investigate impacts of interannual to interdecadal changes in the wind forcing on the circulation and meridional transports in the South Atlantic, a set of simulations is conducted with an eddy-resolving global implementation of the Hybrid Coordinate Ocean Model (HYCOM). Firstly, a climatological experiment is run, forced with monthly means of the NCEP Reanalysis products, with no interannual variability. The last ten years of a two-decades run are then analyzed. The mean circulation patterns in the South Atlantic are well represented, as compared with observations and results of other models. The outputs show no long term trends, ruling out the hypothesis of any noticeable model's internal drift. Another experiments is then run, forced with interannual variability, from 1949 to the present. The results are compared with those of the climatological experiment, focusing on the circulation, the inter-ocean exchanges, the Agulhas leakage and the meridional transports in the South Atlantic.

  12. Data-driven wind plant control

    NARCIS (Netherlands)

    Gebraad, P.M.O.

    2014-01-01

    Each wind turbine in a cluster of wind turbines (a wind power plant) can influence the performance of other turbines through the wake that forms downstream of its rotor. The wake has a reduced wind velocity, since the turbine extracts energy from the flow, and the obstruction by the wind turbine

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

    NARCIS (Netherlands)

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

    2016-01-01

    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

  14. Meridional Flow Variations in Cycles 23 and 24: Active Latitude Control of Sunspot Cycle Amplitudes

    Science.gov (United States)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    We have measured the meridional motions of magnetic elements observed in the photosphere over sunspot cycles 23 and 24 using magnetograms from SOHO/MDI and SDO/HMI. Our measurements confirm the finding of Komm, Howard, and Harvey (1993) that the poleward meridional flow weakens at cycle maxima. Our high spatial and temporal resolution analyses show that this variation is in the form of a superimposed inflow toward the active latitudes. This inflow is weaker in cycle 24 when compared to the inflow in 23, the stronger cycle. This systematic modulation of the meridional flow can modulate the amplitude of the following sunspot cycle through its influence on the Sun's polar fields.

  15. A multimodel comparison of centennial Atlantic meridional overturning circulation variability

    Energy Technology Data Exchange (ETDEWEB)

    Menary, Matthew B.; Vellinga, Michael; Palmer, Matthew D. [Met Office Hadley Centre, Exeter, Devon (United Kingdom); Park, Wonsun; Latif, Mojib [IFM-GEOMAR, Leibniz-Institut fuer Meereswissenschaften, Kiel (Germany); Lohmann, Katja; Jungclaus, Johann H. [Max Planck Inst Meteorol, Hamburg (Germany)

    2012-06-15

    A mechanism contributing to centennial variability of the Atlantic Meridional Overturning Circulation (AMOC) is tested with multi-millennial control simulations of several coupled general circulation models (CGCMs). These are a substantially extended integration of the 3rd Hadley Centre Coupled Climate Model (HadCM3), the Kiel Climate Model (KCM), and the Max Plank Institute Earth System Model (MPI-ESM). Significant AMOC variability on time scales of around 100 years is simulated in these models. The centennial mechanism links changes in the strength of the AMOC with oceanic salinities and surface temperatures, and atmospheric phenomena such as the Intertropical Convergence Zone (ITCZ). 2 of the 3 models reproduce all aspects of the mechanism, with the third (MPI-ESM) reproducing most of them. A comparison with a high resolution paleo-proxy for Sea Surface Temperatures (SSTs) north of Iceland over the last 4,000 years, also linked to the ITCZ, suggests that elements of this mechanism may also be detectable in the real world. (orig.)

  16. Late Holocene sea level variability and Atlantic Meridional Overturning Circulation

    Science.gov (United States)

    Cronin, Thomas M.; Farmer, Jesse R.; Marzen, R. E.; Thomas, E.; Varekamp, J.C.

    2014-01-01

    Pre-twentieth century sea level (SL) variability remains poorly understood due to limits of tide gauge records, low temporal resolution of tidal marsh records, and regional anomalies caused by dynamic ocean processes, notably multidecadal changes in Atlantic Meridional Overturning Circulation (AMOC). We examined SL and AMOC variability along the eastern United States over the last 2000 years, using a SL curve constructed from proxy sea surface temperature (SST) records from Chesapeake Bay, and twentieth century SL-sea surface temperature (SST) relations derived from tide gauges and instrumental SST. The SL curve shows multidecadal-scale variability (20–30 years) during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA), as well as the twentieth century. During these SL oscillations, short-term rates ranged from 2 to 4 mm yr−1, roughly similar to those of the last few decades. These oscillations likely represent internal modes of climate variability related to AMOC variability and originating at high latitudes, although the exact mechanisms remain unclear. Results imply that dynamic ocean changes, in addition to thermosteric, glacio-eustatic, or glacio-isostatic processes are an inherent part of SL variability in coastal regions, even during millennial-scale climate oscillations such as the MCA and LIA and should be factored into efforts that use tide gauges and tidal marsh sediments to understand global sea level rise.

  17. Meridional equatorial electrojet current in the American sector

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.

    Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  18. Meridional equatorial electrojet current in the American sector

    Directory of Open Access Journals (Sweden)

    R. G. Rastogi

    1999-02-01

    Full Text Available Huancayo is the only equatorial electrojet station where the daytime increase of horizontal geomagnetic field (H is associated with a simultaneous increase of eastward geomagnetic field (Y. It is shown that during the counter electrojet period when ∆H is negative, ∆Y also becomes negative. Thus, the diurnal variation of ∆Y at equatorial latitudes is suggested to be a constituent part of the equatorial electrojet current system. Solar flares are known to increase the H field at an equatorial station during normal electrojet conditions (nej. At Huancayo, situated north of the magnetic equator, the solar flare effect, during nej, consists of positive impulses in H and Y and negative impulse in Z field. During counter electrojet periods (cej, a solar flare produces a negative impulse in H and Y and a positive impulse in Z at Huancayo. It is concluded that both the zonal and meridional components of the equatorial electrojet in American longitudes, as in Indian longitudes, flows in the same, E region of the ionosphere.Key words. Geomagnetism and paleomagnetism (dynamo theories · Ionosphere (equatorial ionosphere; ionosphere disturbances

  19. A Numerical Study on the Impeller Meridional Curvature of High Pressure Multistage Pump

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Deok Su; Jean, Sang Gyu; Mamatov, Sanjar [Hyosung Goodsprings, Inc., Busan (Korea, Republic of); Park, Warn Gyu [Pusan Nat’l Univ., Busan (Korea, Republic of)

    2017-07-15

    This paper presents the hydraulic design an impeller and radial diffuser of a high-pressure multistage pump for reverse osmosis. The flow distribution and hydraulic performance for the meridional design of the impeller were analyzed numerically. Optimization was conducted based on the response surface method by varying the hub and shroud meridional curvatures, while maintaining the impeller outlet diameter, outlet width, and eye diameter constant. The analysis results of the head and efficiency with the variation in the impeller meridional profile showed that angle of the front shroud near the impeller outlet (εDs) had the highest effect on head increase, while the hub inlet length (d1i) and shroud curvature (Rds) had the highest effect on efficiency. From the meridional profile variation, an approximately 0.5% increase in efficiency was observed compared with the base model (case 25).

  20. Currents, HF Radio-derived, SF Bay Outlet, Normal Model, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements, with missing values filled in by a normal...

  1. Currents, HF Radio-derived, SF Bay Outlet, 1 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 1 hour average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN EXPERIMENTAL...

  2. Currents, HF Radio-derived, Monterey Bay, 25 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 25 hour running average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN...

  3. Currents, HF Radio-derived, Ano Nuevo, 25 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 25 hour running average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN...

  4. Currents, HF Radio-derived, Ano Nuevo, 1 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 1 hour average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN EXPERIMENTAL...

  5. Currents, HF Radio-derived, Monterey Bay, 1 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 1 hour average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN EXPERIMENTAL...

  6. Currents, HF Radio-derived, Bodega Bay, 1 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 1 hour average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN EXPERIMENTAL...

  7. Currents, HF Radio-derived, SF Bay, 33 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 33 hour running average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN...

  8. Currents, HF Radio-derived, SF Bay, 25 hr, Meridional, EXPERIMENTAL

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The data is the 25 hour running average of the meridional component of ocean surface currents derived from High Frequency Radio-derived measurements. THIS IS AN...

  9. Variability of the Atlantic meridional overturning circulation in the last millennium and two IPCC scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Pablo; Montoya, Marisa; Gonzalez-Rouco, Fidel [Universidad Complutense de Madrid, Ciudad Universitaria, Dpto. Astrofisica y Ciencias de la Atmosfera/Instituto de Geociencias, Facultad de Ciencias Fisicas, Madrid (Spain); Universidad Complutense de Madrid, Ciudad Universitaria, Instituto de Geociencias (UCM-CSIC), Facultad de Ciencias Fisicas, Madrid (Spain); Mignot, Juliette [IPSL/LOCEAN, UPMC/CNRS/IRD/MNHN, Universite Pierre et Marie Curie, Paris Cedex 05 (France); Legutke, Stephanie [Deutsches Klimarechenzentrum (DKRZ), Hamburg (Germany)

    2012-05-15

    The variability of the Atlantic meridional overturning circulation (AMOC) is investigated in several climate simulations with the ECHO-G atmosphere-ocean general circulation model, including two forced integrations of the last millennium, one millennial-long control run, and two future scenario simulations of the twenty-first century. This constitutes a new framework in which the AMOC response to future climate change conditions is addressed in the context of both its past evolution and its natural variability. The main mechanisms responsible for the AMOC variability at interannual and multidecadal time scales are described. At high frequencies, the AMOC is directly responding to local changes in the Ekman transport, associated with three modes of climate variability: El Nino-Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and the East Atlantic (EA) pattern. At low frequencies, the AMOC is largely controlled by convection activity south of Greenland. Again, the atmosphere is found to play a leading role in these variations. Positive anomalies of convection are preceded in 1 year by intensified zonal winds, associated in the forced runs to a positive NAO-like pattern. Finally, the sensitivity of the AMOC to three different forcing factors is investigated. The major impact is associated with increasing greenhouse gases, given their strong and persistent radiative forcing. Starting in the Industrial Era and continuing in the future scenarios, the AMOC experiences a final decrease of up to 40% with respect to the preindustrial average. Also, a weak but significant AMOC strengthening is found in response to the major volcanic eruptions, which produce colder and saltier surface conditions over the main convection regions. In contrast, no meaningful impact of the solar forcing on the AMOC is observed. Indeed, solar irradiance only affects convection in the Nordic Seas, with a marginal contribution to the AMOC variability in the ECHO-G runs. (orig.)

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

    Directory of Open Access Journals (Sweden)

    W. Yuan

    2013-08-01

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

  11. Interpreting the implied meridional oceanic energy transport in AMIP

    International Nuclear Information System (INIS)

    Randall, D.A.; Gleckler, P.J.

    1993-09-01

    The Atmospheric Model Intercomparison Project (AMIP) was outlined in Paper No. CLIM VAR 2.3 (entitled open-quote The validation of ocean surface heat fluxes in AMIP') of these proceedings. Preliminary results of AMIP subproject No. 5 were also summarized. In particular, zonally averaged ocean surface heat fluxes resulting from various AMIP simulations were intercompared, and to the extent possible they were validated with uncertainties in observationally-based estimates of surface heat fluxes. The intercomparison is continued in this paper by examining the Oceanic Meridional Energy Transport (OMET) implied by the net surface heat fluxes of the AMIP simulations. As with the surface heat fluxes of the AMIP simulations. As with the surface heat fluxes, the perspective here will be very cursory. The annual mean implied ocean heat transport can be estimated by integrating the zonally averaged net ocean surface heat flux, N sfc , from one pole to the other. In AGCM simulations (and perhaps reality), the global mean N sfc is typically not in exact balance when averaged over one or more years. Because of this, an important assumption must be made about changes in the distribution of energy in the oceans. Otherwise, the integration will yield a non-zero transport at the endpoint of integration (pole) which is not physically realistic. Here the authors will only look at 10-year means of the AMIP runs, and for simplicity they assume that any long term imbalance in the global averaged N sfc will be sequestered (or released) over the global ocean. Tests have demonstrated that the treatment of how the global average energy imbalance is assumed to be distributed is important, especially when the long term imbalances are in excess of 10 W m -2 . However, this has not had a substantial impact on the qualitative features of the implied heat transport of the AMIP simulations examined thus far

  12. Multi-point optimization on meridional shape of a centrifugal pump impeller for performance improvement

    International Nuclear Information System (INIS)

    Pei, Ji; Wang, Wen Jie; Yuan, Shouqi

    2016-01-01

    A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Qd, 1.0Qd and 1.62Qd were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution, streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement

  13. Wind flow through shrouded wind turbines

    Science.gov (United States)

    2017-03-01

    velocity and model angle were varied . Additionally, static wall pressures and cross section flow were studied with the addition of a screen. The pressure...the geometry of a wind lens or flange on the shroud and a gradually diverging shape, proved to accelerate the flow through the duct. 14. SUBJECT...Tunnel velocity and model angle were varied . Additionally, static wall pressures and cross section flow were studied with the addition of a screen. The

  14. Role of Wind Tunnels in Aircraft Design

    Indian Academy of Sciences (India)

    large wind tunnels simulating the actual flight conditions as nearly as possible. Often, several wind tunnels ... wind tunnel tests can be 'scaled' to the actual velocity and actual body size using suitable scaling laws. A typical wind tunnel consists ofa test section ... tion and control positions. Some of this instrumentation like six.

  15. Orbital velocity

    OpenAIRE

    Modestino, Giuseppina

    2016-01-01

    The trajectory and the orbital velocity are determined for an object moving in a gravitational system, in terms of fundamental and independent variables. In particular, considering a path on equipotential line, the elliptical orbit is naturally traced, verifying evidently the keplerian laws. The case of the planets of the solar system is presented.

  16. Atlantic Meridional Overturning Circulation response to idealized external forcing

    Energy Technology Data Exchange (ETDEWEB)

    Park, W.; Latif, M. [Leibniz-Institut fuer Meereswissenschaften an der Universitaet Kiel, Kiel (Germany)

    2012-10-15

    The response of the Atlantic Meridional Overturning Circulation (AMOC) to idealized external (solar) forcing is studied in terms of the internal (unforced) AMOC modes with the Kiel Climate Model (KCM), a coupled atmosphere-ocean-sea ice general circulation model. The statistical investigation of KCM's internal AMOC variability obtained from a multi-millennial control run yields three distinct modes: a multi-decadal mode with a period of about 60 years, a quasi-centennial mode with a period of about 100 years and a multi-centennial mode with a period of about 300-400 years. Most variance is explained by the multi-centennial mode, and the least by the quasi-centennial mode. The solar constant varies sinusoidally with two different periods (100 and 60 years) in forced runs with KCM. The AMOC response to the external forcing is rather complex and nonlinear. It involves strong changes in the frequency structure of the variability. While the control run depicts multi-timescale behavior, the AMOC variability in the experiment with 100 year forcing period is channeled into a relatively narrow band centered near the forcing period. It is the quasi-centennial AMOC mode with a period of just under 100 years which is excited, although it is heavily damped in the control run. Thus, the quasi-centennial mode retains its period which does not correspond exactly to the forcing period. Surprisingly, the quasi-centennial mode is also most strongly excited when the forcing period is set to 60 years, the period of the multi-decadal mode which is rather prominent in the control run. It is largely the spatial structure of the forcing rather than its period that determines which of the three internal AMOC modes is excited. The results suggest that we need to understand the full modal structure of the internal AMOC variability in order to understand the circulation's response to external forcing. This could be a challenge for climate models: we cannot necessarily expect that the

  17. Contrasting meridional structures of stratospheric and tropospheric planetary wave variability in the Northern Hemisphere

    Directory of Open Access Journals (Sweden)

    Cheng Sun

    2014-11-01

    Full Text Available The meridional structures of stratospheric and tropospheric planetary wave variability (PWV over the Northern Hemisphere (NH extratropics were investigated and compared using reanalysis data. By performing the spherical double Fourier series expansion of geopotential height data, the horizontal structures of PWV at each vertical level could be examined in the two-dimensional (2D wavenumber (zonal and meridional wavenumbers space. Comparing the amplitudes of wave components during the last three decades, the results suggested that the structures of PWV in the NH troposphere significantly differ from the stratospheric counterparts. The PWV in the troposphere shows multiple meridional wave-like structures, most pronounced for the meridional dipole; while in contrast, PWV in the stratosphere mainly shows large-scale zonal wave patterns, dominated by zonal waves 1 and 2, and have little wave-like fluctuation in the latitudinal direction. The dominant patterns of the NH PWV also show contrasting features of meridional structure between the stratosphere and the troposphere. As represented in the 2D wavenumber space, the leading two empirical orthogonal functions of PWV in the stratosphere largely exhibit the zonal wave 1 pattern, while those in the troposphere clearly show meridional wave-like structures and are dominated by the dipole. The refractive index was derived based on the zonal mean basic state to qualitatively interpret the observational findings. The results suggested that the basic state in the NH troposphere is much more favourable for latitudinally propagating stationary waves than the stratosphere. The difference in meridional structure between stratospheric and tropospheric planetary waves can be well captured in a linear baroclinic model with the observed zonal mean basic state. Furthermore, both theoretical and modelling analyses demonstrated that the fact that zonal wave patterns are preferred in the NH stratosphere may be partly

  18. Noise from wind turbines

    International Nuclear Information System (INIS)

    Andersen, B.; Jakobsen, J.

    1992-11-01

    Based on a previous project concerning the calculation of the amount of noise emanating from wind turbine arrays, this one examines the subject further by investigating whether there could be significant differences in the amount of noise made by individual wind turbines in an array, and whether the noise is transmitted in varying directions - so that when it is carried in the same direction as the wind blows it would appear to be louder. The aim was also to determine whether the previously used method of calculation lacked precision. It was found that differences in noise niveaux related to individual wind turbines were insignificant and that noise was not so loud when it was not borne in the direction of the wind. It was necessary to change the method of calculation as reckoning should include the influence of the terrain, wind velocity and distance. The measuring and calculation methods are exemplified and the resulting measurements are presented in detail. (AB)

  19. ESTIMATING THE DEEP SOLAR MERIDIONAL CIRCULATION USING MAGNETIC OBSERVATIONS AND A DYNAMO MODEL: A VARIATIONAL APPROACH

    Energy Technology Data Exchange (ETDEWEB)

    Hung, Ching Pui; Jouve, Laurène; Brun, Allan Sacha [Laboratoire AIM Paris-Saclay, CEA/IRFU Université Paris-Diderot CNRS/INSU, F-91191 Gif-Sur-Yvette (France); Fournier, Alexandre [Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot UMR 7154 CNRS, F-75005 Paris (France); Talagrand, Olivier [Laboratoire de météorologie dynamique, UMR 8539, Ecole Normale Supérieure, Paris Cedex 05 (France)

    2015-12-01

    We show how magnetic observations of the Sun can be used in conjunction with an axisymmetric flux-transport solar dynamo model in order to estimate the large-scale meridional circulation throughout the convection zone. Our innovative approach rests on variational data assimilation, whereby the distance between predictions and observations (measured by an objective function) is iteratively minimized by means of an optimization algorithm seeking the meridional flow that best accounts for the data. The minimization is performed using a quasi-Newton technique, which requires knowledge of the sensitivity of the objective function to the meridional flow. That sensitivity is efficiently computed via the integration of the adjoint flux-transport dynamo model. Closed-loop (also known as twin) experiments using synthetic data demonstrate the validity and accuracy of this technique for a variety of meridional flow configurations, ranging from unicellular and equatorially symmetric to multicellular and equatorially asymmetric. In this well-controlled synthetic context, we perform a systematic study of the behavior of our variational approach under different observational configurations by varying their spatial density, temporal density, and noise level, as well as the width of the assimilation window. We find that the method is remarkably robust, leading in most cases to a recovery of the true meridional flow to within better than 1%. These encouraging results are a first step toward using this technique to (i) better constrain the physical processes occurring inside the Sun and (ii) better predict solar activity on decadal timescales.

  20. Wind energy

    International Nuclear Information System (INIS)

    Anon.

    1992-01-01

    This chapter discusses the role wind energy may have in the energy future of the US. The topics discussed in the chapter include historical aspects of wind energy use, the wind energy resource, wind energy technology including intermediate-size and small wind turbines and intermittency of wind power, public attitudes toward wind power, and environmental, siting and land use issues

  1. Meridional Motion and Reynolds Stress from Debrecen Photoheliographic Data

    Czech Academy of Sciences Publication Activity Database

    Sudar, D.; Brajša, R.; Skokić, Ivica; Beljan, I.P.; Woehl, H.

    2017-01-01

    Roč. 292, č. 7 (2017), 86/1-86/13 ISSN 0038-0938 R&D Projects: GA MŠk(CZ) 7E13003 EU Projects: European Commission(XE) 312495 - SOLARNET Institutional support: RVO:67985815 Keywords : sunspots * rotation * velocity fields Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics OBOR OECD: Astronomy (including astrophysics,space science) Impact factor: 2.682, year: 2016

  2. Surface changes in the North Atlantic meridional overturning circulation during the last millennium

    DEFF Research Database (Denmark)

    Wanamaker, Jr., Alan D.; Butler, Paul G.; Scourse, James D.

    2012-01-01

    the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation......Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance...... of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning...

  3. Surface changes in the North Atlantic meridional overturning circulation during the last millennium

    Science.gov (United States)

    Wanamaker, Alan D.; Butler, Paul G.; Scourse, James D.; Heinemeier, Jan; Eiríksson, Jón; Knudsen, Karen Luise; Richardson, Christopher A.

    2012-01-01

    Despite numerous investigations, the dynamical origins of the Medieval Climate Anomaly and the Little Ice Age remain uncertain. A major unresolved issue relating to internal climate dynamics is the mode and tempo of Atlantic meridional overturning circulation variability, and the significance of decadal-to-centennial scale changes in Atlantic meridional overturning circulation strength in regulating the climate of the last millennium. Here we use the time-constrained high-resolution local radiocarbon reservoir age offset derived from an absolutely dated annually resolved shell chronology spanning the past 1,350 years, to reconstruct changes in surface ocean circulation and climate. The water mass tracer data presented here from the North Icelandic shelf, combined with previously published data from the Arctic and subtropical Atlantic, show that surface Atlantic meridional overturning circulation dynamics likely amplified the relatively warm conditions during the Medieval Climate Anomaly and the relatively cool conditions during the Little Ice Age within the North Atlantic sector. PMID:22692542

  4. Escleroplastia meridional: A propósito de un caso en 1999 Meridional scleroplasty: With regard to a case in 1999

    Directory of Open Access Journals (Sweden)

    Enrique J. Machado Fernández

    2000-06-01

    Full Text Available En este artículo se presenta un caso reciente de rechazo al aloplante utilizado para escleroplastia meridional. Se refieren las características del cuadro clínico presentado y su tratamiento. Además, se expresan consideraciones basadas en datos estadísticos y hallazgos anatomopatológicos que fundamentan la suspensión de la práctica de esta técnica en el Centro de Microcirugía Ocular.In present paper, authors present a recent case of rejection to allograft used to meridional scleroplasty. Festures of clinical picture and its treatment are related. Furthermore, we express statistical data based on considerations and anatomic-pathologic findings supporting suspension of practice of this technique in Center of Microsurgery of Eye.

  5. Effects of the Observed Meridional Flow Variations since 1996 on the Sun's Polar Fields

    Science.gov (United States)

    Hathaway, David H.; Upton, Lisa

    2013-01-01

    The cause of the low and extended minimum in solar activity between Sunspot Cycles 23 and 24 was the small size of Sunspot Cycle 24 itself - small cycles start late and leave behind low minima. Cycle 24 is small because the polar fields produced during Cycle 23 were substantially weaker than those produced during the previous cycles and those (weak) polar fields are the seeds for the activity of the following cycle. The polar fields are produced by the latitudinal transport of magnetic flux that emerged in low-latitude active regions. The polar fields thus depend upon the details of both the flux emergence and the flux transport. We have measured the flux transport flows (differential rotation, meridional flow, and supergranules) since 1996 and find systematic and substantial variation in the meridional flow alone. Here we present experiments using a Surface Flux Transport Model in which magnetic field data from SOHO/MDI and SDO/HMI are assimilated into the model only at latitudes between 45-degrees north and south of the equator (this assures that the details of the active region flux emergence are well represented). This flux is then transported in both longitude and latitude by the observed flows. In one experiment the meridional flow is given by the time averaged (and north-south symmetric) meridional flow profile. In the second experiment the time-varying and north-south asymmetric meridional flow is used. Differences between the observed polar fields and those produced in these two experiments allow us to ascertain the effects of these meridional flow variations on the Sun s polar fields.

  6. Improvements in launchings and recipients of PIG in Malha de Gasodutos Nordeste Meridional; Melhorias nos lancamentos e recebedores de PIG da Malha de Gasodutos Nordeste Meridional

    Energy Technology Data Exchange (ETDEWEB)

    Maciel, Jairo A.C.; Lemos, Francisco A.C.; Lima, Artur W.R. de S. [PETROBRAS Transporte S.A. (TRANSPETRO), Rio de Janeiro, RJ (Brazil)

    2012-07-01

    This paper describes the study that resulted in the preparation of a project for improvement of launchers and receivers of PIG in facilities maintained and operated by PETROBRAS S.A. (TRANSPETRO) in the Malha de Gasodutos Nordeste Meridional (Malha NEM). The improvements are part of the component in cleaner production system and reduce the risks of accidents and the costs of hazardous waste management.

  7. Mechanisms of meridional transport processes in the tropical Atlantic; Mechanismen meridionaler Transportprozesse im tropischen Atlantik

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, J.

    2001-07-01

    Meridional transport processes of water masses and tracers in the subtropical and tropical Atlantic are investigated using a regional eddy resolving model of the wind driven and thermohaline circulation. Analytical emphasis is on float simulations in the model which, complementary to Eulerian means, represent the Lagrangian view and give further insight into the spreading and pathways of characteristic water masses in this area. In the tropics and subtropics shallow 3-dimensional circulation cells are superimposed on the northward warm water transfer within the deep reaching thermohaline overturning cell (MOC) as part of the global ''Conveyor Belt''. Under present-day climate conditions the model shows that the equatorial thermocline is exclusively ventilated by subsurface flow within the tropical-subtropical cell (STC) of the South Atlantic. Only with a prescribed ''Conveyor-off''-Mode the STC of the North Atlantic contributes to this ventilation process with equal amounts. Throughout the year the interhemispheric transport of surface and central water masses of South Atlantic origin into the Caribbean Sea is dominated by zonal detours to the east as a consequence of the interplay of several retroflection events occuring in the North Atlantic. The eulerian mean flow field in the deep layer postulates the interhemispheric mass transport into the South Atlantic to be confined entirely to the western boundary, whereas Lagrangian means indicate intermittent eastward excursions along the equator, related to seasonally alternating zonal currents due to long Rossby waves. It was suggested that the observed characteristic eastward maximum of tracer concentrations along the equator is a consequence of rectifying effects of single or interacting equatorial waves. The model does not validate this hypothesis. The response to transport anomalies of subpolar origin and long periodicity is subject to different time-scales in both

  8. Analysis of Wind Energy Potential and Vibrations Caused by Wind Turbine on Its Basement

    Czech Academy of Sciences Publication Activity Database

    Kaláb, Z.; Hanslian, David; Stolárik, M.; Pinka, M.

    2014-01-01

    Roč. 19, č. 3 (2014), s. 151-159 ISSN 1335-1788 Institutional support: RVO:68378289 Keywords : wind turbine * wind energy potential * wind map * wind map * experimental measurement * vibration velocity Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.329, year: 2014 http://actamont.tuke.sk/pdf/2014/n3/6kalab.pdf

  9. Wind data for wind driven plant. [site selection for optimal performance

    Science.gov (United States)

    Stodhart, A. H.

    1973-01-01

    Simple, averaged wind velocity data provide information on energy availability, facilitate generator site selection and enable appropriate operating ranges to be established for windpowered plants. They also provide a basis for the prediction of extreme wind speeds.

  10. Comparison of wind and wind shear climatologies derived from high-resolution radiosondes and the ECMWF model

    Science.gov (United States)

    Houchi, K.; Stoffelen, A.; Marseille, G. J.; de Kloe, J.

    2010-11-01

    The climatology of atmospheric horizontal wind and its vertical gradient, i.e., wind shear, is characterized as a function of climate region. For a better representation of the average atmospheric wind and shear and their variabilities, high-resolution radiosonde wind profiles up to about 30 km altitude are compared with the collocated operational ECMWF model for short-range forecast winds. Statistics of zonal and meridional winds are established from both data sets. The results show mainly similarity in the probability distributions of the modeled and observed horizontal winds, practically at all levels of the atmosphere, while at the same time the vertical shear of the wind is substantially underestimated in the model. The comparison of shear statistics of radiosonde and ECMWF model winds shows that the model wind shear mean and variability are on average a factor of 2.5 (zonal) and 3 (meridional) smaller than of radiosondes in the free troposphere, while in the stratosphere, the planetary boundary layer results are more variable. By applying vertical averaging to the radiosonde data, it is found that the effective vertical resolution of the ECMWF model is typically 1.7 km. Moreover, it is found for individually collocated radiosonde model wind and shear profiles that the model wind may lack in some cases variability larger than 5 m s-1 and 0.015 s-1, respectively, due mainly to the effect of lacking vertical resolution, in particular near the jets. Besides the general importance of this study in highlighting the difference in the representation of the atmospheric wind shear by model and observations, it is more specifically relevant for the future Atmospheric Dynamics Mission (ADM-Aeolus) of the European Space Agency due for launch in 2012. The results presented here are used to generate a realistic global atmospheric database, which is necessary to conduct simulations of the Aeolus Doppler wind lidar in order optimize its vertical sampling and processing.

  11. Interdecadal Change in the Relationship Between the North Pacific Oscillation and the Pacific Meridional Mode and Its Impact on ENSO

    Science.gov (United States)

    Shin, So-Jung; An, Soon-Il

    2018-02-01

    Two leading but independent modes of Northern Pacific atmospheric circulation: the North Pacific Oscillation (NPO) and the Pacific Meridional Mode (PMM), are known external triggers of the El Niño-Southern Oscillation (ENSO) by the sequential migration of sea surface temperature (SST) anomalies into the tropics possibly by means of wind-evaporation-SST (WES) feedbacks. Because of the similar roles of NPO and PMM, most previous studies have explored them with no separation. Here, we investigate their independent and combined effects in triggering ENSO, and find that when the NPO and PMM occur simultaneously during spring, ENSO or ENSO-like SST anomalies are generated during the following winter; whereas when either the NPO or PMM occur alone, ENSO events rarely occur. Furthermore, the relationship between NPO and PMM shows noticeable interdecadal variability, which is related to decadal changes in the mean upper-level jet stream over the North Pacific. Changes in the upper-level jet stream modify the location of the center of the Aleutian Low, which plays a role in bridging the NPO and PMM processes, especially when it migrates to the southwest. The period when NPO and PMM are well correlated coincides somewhat with the active ENSO period, and vice versa, indicating that a more efficient trigger due to combined NPO-PMM processes results in a higher variation of ENSO. Finally, analysis of the coupled model control simulations strongly supports our observational analysis results.

  12. Impact of the GeoMIP G1 sunshade geoengineering experiment on the Atlantic meridional overturning circulation

    Science.gov (United States)

    Hong, Yu; Moore, John C.; Jevrejeva, Svetlana; Ji, Duoying; Phipps, Steven J.; Lenton, Andrew; Tilmes, Simone; Watanabe, Shingo; Zhao, Liyun

    2017-03-01

    We analyze the multi-earth system model responses of ocean temperatures and the Atlantic Meridional Overturning Circulation (AMOC) under an idealized solar radiation management scenario (G1) from the Geoengineering Model Intercomparison Project. All models simulate warming of the northern North Atlantic relative to no geoengineering, despite geoengineering substantially offsetting the increases in mean global ocean temperatures. Increases in the temperature of the North Atlantic Ocean at the surface (˜0.25 K) and at a depth of 500 m (˜0.10 K) are mainly due to a 10 Wm-2 reduction of total heat flux from ocean to atmosphere. Although the AMOC is slightly reduced under the solar dimming scenario, G1, relative to piControl, it is about 37% stronger than under abrupt4 × CO2 . The reduction of the AMOC under G1 is mainly a response to the heat flux change at the northern North Atlantic rather than to changes in the water flux and the wind stress. The AMOC transfers heat from tropics to high latitudes, helping to warm the high latitudes, and its strength is maintained under solar dimming rather than weakened by greenhouse gas forcing acting alone. Hence the relative reduction in high latitude ocean temperatures provided by solar radiation geoengineering, would tend to be counteracted by the correspondingly active AMOC circulation which furthermore transports warm surface waters towards the Greenland ice sheet, warming Arctic sea ice and permafrost.

  13. Sensing the wind profile

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo

    This thesis consists of two parts. The first is a synopsis of the theoretical progress of the study that is based on a number of journal papers. The papers, which constitute the second part of the report, aim to analyze, measure, and model the wind prole in and beyond the surface layer by combining...... measurements are averaged for several stability conditions and compare well with the surface-layer wind profile. At Høvsøre, it is sufficient to scale the wind speed with the surface friction velocity, whereas at Horns Rev a new scaling is added, due to the variant roughness length. This new scaling is coupled...

  14. Dependence of optimal wind turbine spacing on wind farm length

    NARCIS (Netherlands)

    Stevens, Richard Johannes Antonius Maria

    2016-01-01

    Recent large eddy simulations have led to improved parameterizations of the effective roughness height of wind farms. This effective roughness height can be used to predict the wind velocity at hub-height as function of the geometric mean of the spanwise and streamwise turbine spacings and the

  15. Interdecadal North-Atlantic meridional overturning circulation variability in EC-EARTH

    NARCIS (Netherlands)

    Wouters, B.; Drijfhout, D.; Hazeleger, W.

    2012-01-01

    The Atlantic meridional overturning circulation (AMOC) in a 600 years pre-industrial run of the newly developed EC-EARTH model features marked interdecadal variability with a dominant time-scale of 50–60 years. An oscillation of approximately 2 Sverdrup (1 Sv = 106 m3 s-1) is identified, which

  16. Meridional gradients of light absorbing carbon over northern Europe

    International Nuclear Information System (INIS)

    Baumgardner, D; Kok, G; Kraemer, M; Weidle, F

    2008-01-01

    In situ measurements have been made in the upper troposphere of the properties of particles containing light absorbing carbon (LAC). These measurements, made in late November 2006 over northern Europe, show that the average LAC mass concentration varies between 1 and 5 ng m -3 over a latitude range 50 deg. to 70 deg. N, with maxima at 50 deg. and 66 deg. The relative fraction of all particles larger than 0.1 μm that contain LAC decreases at higher latitudes. The derived extinction coefficient, which also increases with latitude, reaches a maximum of 1.4 Mm -1 at 66 deg. The air mass histories associated with the LAC were evaluated with back trajectory analysis using wind field analysis from the European Center for Median-Range Weather Forecast (ECMWF). A positive correlation exists between the fraction of particles containing LAC and the maximum relative humidity (RH), minimum temperature and maximum number of hours of cloud experienced by the air mass in the 5-10 days prior to being sampled by the aircraft. Air masses arriving from lower altitudes and with trajectories over North America also had larger concentration fractions of LAC. The average LAC mass is in good agreement with previous measurements made over North America for the same latitude range, and the span of values fits best with model predictions of LAC distributions that assume that the LAC transported from surface sources is hydrophobic

  17. Lidar Turbulence Measurements for Wind Energy

    DEFF Research Database (Denmark)

    Mann, Jakob; Sathe, Ameya; Gottschall, Julia

    2012-01-01

    Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the velocity azimuth display technique to measure the velocity vector. The model is developed for the line-of-sight averaging...

  18. Lidar Turbulence Measurements for Wind Energy

    DEFF Research Database (Denmark)

    Mann, Jakob; Sathe, Ameya; Gottschall, Julia

    2012-01-01

    Modeling of the systematic errors in the second-order moments of wind speeds measured by continuous-wave (ZephIR) and pulsed (WindCube) lidars is presented. These lidars use the velocity azimuth display technique to measure the velocity vector. The model is developed for the line-of-sight averagi...

  19. Interconverting the matrix and principal-meridional representations of dioptric power and reduced vergence.

    Science.gov (United States)

    Harris, W F

    2000-11-01

    Converting the traditional representation of power as sphere, cylinder and axis to the dioptric power matrix F is usually performed by means of Long's equations and the reverse process by means of Keating's equations. It is sometimes useful to be able to convert directly between the matrix and power expressed in terms of principal powers F1 and F2 along corresponding principal meridians at angles a1 and a2. The equations for interconverting F and the principal-meridional representation expressed as F1(a1)F2 are presented here. Equivalent equations allow direct interconversion of the reduced vergence matrix L and the principal-meridional representation of vergence L1(a1)L2. Vergence becomes infinite at line and point focuses. Similarly effective power and back- and front-vertex power are infinite for some systems. Nevertheless it is possible unambiguously to represent infinite vergence and vertex power in principal-meridional form. However, information is usually lost in these infinite cases when the principal-meridional representation is converted to the matrix representation, and the former is not recoverable from the latter. As a consequence the matrix representation is usually unsatisfactory for vergences and vertex powers that are infinite. On the other hand, the principal-meridional representation of vergence and power is always satisfactory. If one adopts the position that effective powers and vertex powers are really vergences rather than powers then one concludes that the matrix provides a satisfactory representation for powers of thin systems in general but not for vergences. Implied by a vergence at a point is an interval of Sturm. The equations for characterizing the interval from the reduced vergence are presented.

  20. Mean vertical wind in the mesosphere-lower thermosphere region (80–120 km deduced from the WINDII observations on board UARS

    Directory of Open Access Journals (Sweden)

    V. Fauliot

    1997-09-01

    Full Text Available The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S green-line emission in the Earth's mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.

  1. Mean vertical wind in the mesosphere-lower thermosphere region (80–120 km deduced from the WINDII observations on board UARS

    Directory of Open Access Journals (Sweden)

    V. Fauliot

    Full Text Available The WINDII interferometer placed on board the Upper Atmosphere Research Satellite measures temperature and wind from the O(1S green-line emission in the Earth's mesosphere and lower thermosphere. It is a remote-sensing instrument providing the horizontal wind components. In this study, the vertical winds are derived using the continuity equation. Mean wind annually averaged at equinoxes and solstices is shown. Ascendance and subsidence to the order of 1–2 cm s–1 present a seasonal occurrence at the equator and tropics. Zonal Coriolis acceleration and adiabatic heating and cooling rate associated to the mean meridional and vertical circulations are evaluated. The line emission rate measured together with the horizontal wind shows structures in altitude and latitude correlated with the meridional and vertical wind patterns. The effect of wind advection is discussed.

  2. Mean winds of the mesosphere and lower thermosphere at 52° N in the period 1988–2000

    Directory of Open Access Journals (Sweden)

    H. R. Middleton

    Full Text Available A meteor radar in the UK (near 52° N has been used to measure the mean winds of the mesosphere/lower-thermosphere (MLT region over the period 1988–2000. The seasonal course and interannual variability is characterised and comparisons are made with a number of models. Annual mean wind trends were found to be + 0.37 ms-1 yr-1 for the zonal component and + 0.157 ms-1 yr-1 for the meridional component. Seasonal means revealed significant trends in the case of meridional winds in spring ( + 0.38 ms-1 yr-1 and autumn ( + 0.29 ms-1 yr-1, and zonal winds in summer ( + 0.48 ms-1 yr-1 and autumn ( + 0.38 ms-1 yr-1. Significant correlation coefficients, R, between the sunspot number and seasonal mean wind are found in four instances. In the case of the summer zonal winds, R = + 0.732; for the winter meridional winds, R = - 0.677; for the winter zonal winds, R = - 0.472; and for the autumn zonal winds R = + 0.508.

    Key words. Meteorology and atmospheric dynamics (climatology; general circulation; middle atmospheric dynamics

  3. ESCAPING PARTICLE FLUXES IN THE ATMOSPHERES OF CLOSE-IN EXOPLANETS. II. REDUCED MASS-LOSS RATES AND ANISOTROPIC WINDS

    International Nuclear Information System (INIS)

    Guo, J. H.

    2013-01-01

    In Paper I, we presented a one-dimensional hydrodynamic model for the winds of close-in exoplanets. However, close-in exoplanets are tidally locked and irradiated only on the day sides by their host stars. This requires two-dimensional hydrodynamic models with self-consistent radiative transfer calculations. In this paper, for the tidal-locking (two-dimensional radiative transfer) and non-tidal-locking cases (one-dimensional radiative transfer), we constructed a multi-fluid two-dimensional hydrodynamic model with detailed radiative transfer to depict the escape of particles. We found that the tidal forces (the sum of tidal gravity of the star and centrifugal force due to the planetary rotation) supply significant accelerations and result in anisotropic winds. An important effect of the tidal forces is that it severely depresses the outflow of particles near the polar regions where the density and the radial velocity are a factor of a few (ten) smaller than those of the low-latitude regions. As a consequence, most particles escape the surface of the planet from the regions of low latitude. Comparing the tidal-locking and non-tidal-locking cases, we found that their optical depths are very different so that the flows also emerge with a different pattern. In the case of non-tidal locking, the radial velocities at the base of the wind are higher than the meridional velocities. However, in the case of tidal locking, the meridional velocities dominate the flow at the base of the wind, and they can effectively transfer mass and energy from the day sides to the night sides. Further, we also found that the differences of the winds show a middle extent at large radii. This means that the structure of the wind at the base can be changed by the two-dimensional radiative transfer due to large optical depths, but the extent is reduced with an increase in radius. Because the escape is depressed in the polar regions, the mass-loss rate predicted by the non-tidal-locking model, in

  4. Wind turbine power and sound in relation to atmospheric stability

    NARCIS (Netherlands)

    van den Berg, G. P.

    2008-01-01

    Atmospheric stability cannot, with respect to modem, toll wind turbines, be viewed as a 'small perturbation to a basic neutral state' This can be demonstrated by comparison of measured wind velocity at the height of the rotor with the wind velocity expected in a neutral or 'standard' atmosphere.

  5. Solar Wind Associated with Near Equatorial Coronal Hole M ...

    Indian Academy of Sciences (India)

    2015-05-25

    May 25, 2015 ... pute coronal hole radiative energy near the earth and it is found to be of similar order as that of ... hole and energy due to solar wind, it is conjectured that solar wind might have originated around the ..... velocity Vsw (assuming wind velocity is constant throughout from the source to the place of observation) ...

  6. Wind characteristics and energy potentialities of some selected sites ...

    African Journals Online (AJOL)

    The wind regime as observed in three meteorological stations in the north Cameroon are presented in form of velocity duration curves as well as in form of velocity frequency curves. Monthly average wind speed distributions were determined for each station. Based on the analysed data, the utilisation of wind for power ...

  7. Model of wind shear conditional on turbulence and its impact on wind turbine loads

    DEFF Research Database (Denmark)

    Dimitrov, Nikolay Krasimirov; Natarajan, Anand; Kelly, Mark C.

    2015-01-01

    fatigue load is achieved. The proposed wind shear model based on the wind measurements is thereby probabilistic in definition, with shear jointly distributed with wind turbulence. A simplified model for the wind shear exponent is further derived from the full stochastic model. The fatigue loads over......We analyse high-frequency wind velocity measurements from two test stations over a period of several years and at heights ranging from 60 to 200 m, with the objective to validate wind shear predictions as used in load simulations for wind turbine design. A validated wind shear model is thereby...... different turbine components are evaluated under the full wind measurements, using the developed wind shear model and with standard wind conditions prescribed in the IEC 61400-1 ed. 3. The results display the effect of the Wöhler exponent and reveal that under moderate turbulence, the effect of wind shear...

  8. Wind Energy

    International Nuclear Information System (INIS)

    Rodriguez D, J.M.

    1998-01-01

    The general theory of the wind energy conversion systems is presented. The availability of the wind resource in Colombia and the ranges of the speed of the wind in those which is possible economically to use the wind turbines are described. It is continued with a description of the principal technological characteristics of the wind turbines and are split into wind power and wind-powered pumps; and its use in large quantities grouped in wind farms or in autonomous systems. Finally, its costs and its environmental impact are presented

  9. The influence of meridional ice transport on Europa's ocean stratification and heat content

    Science.gov (United States)

    Zhu, P.; Manucharyan, G.; Thompson, A. F.; Goodman, J. C.; Vance, S.

    2017-12-01

    Jupiter's moon Europa likely hosts a saltwater ocean beneath its icy surface. Geothermal heating and rotating convection in the ocean may drive a global overturning circulation that redistributes heat vertically and meridionally, preferentially warming the ice shell at the equator. Here we assess thepreviously unconstrained influence of ocean-ice coupling on Europa's ocean stratification and heat transport. We demonstrate that a relatively fresh layer can form at the ice-ocean interface due to a meridional ice transport forced by the differential ice shell heating between the equator and the poles. We provide analytical and numerical solutions for the layer's characteristics, highlighting their sensitivity to critical ocean parameters. For a weakly turbulent and highly saline ocean, a strong buoyancy gradient at the base of the freshwater layer can suppress vertical tracer exchange with the deeper ocean. As a result, the freshwater layer permits relatively warm deep ocean temperatures.

  10. Device for the acquisition and visualization in real time of the velocity and direction of wind in a radiological post stage; Dispositivo para la adquisicion y visualizacion en tiempo real de la velocidad y direccion del viento en una posta radiologica

    Energy Technology Data Exchange (ETDEWEB)

    Ledo P, L.M.; Guibert G, R. [CEADEN, Calle 30 No. 502 e/5 y 7 Ave. Miramar, Ciudad La Habana (Cuba); Dominguez L, O.; Alonso A, D.; Ramos V, E.O. [CPHR, Calle 20 No. 4113 e/41 y 47, Playa, 11300 La Habana, A.P. 6195 C.P. 10600 (Cuba)]. e-mail: ledo@ceaden.edu.cu

    2006-07-01

    The work shows the development, construction and post stage of a device dedicated to the acquisition and transmission in real time of the information on the behavior of the meteorological variables: velocity and wind direction. It is introduced for the first time in an observation position the automatic monitoring, in real time, using the tools that it offers the digitalisation of the information and the computation. The obtained data are registered in a PC, its are visualized appropriately and can be objects of later analysis. It was developed the application program Autoclima for such purpose. (Author)

  11. Agrobiodiversity of cactus pear (Opuntia, Cactaceae) in the Meridional Highlands Plateau of Mexico

    OpenAIRE

    Juan Antonio Reyes-Agüero; Juan Rogelio Aguirre Rivera

    2011-01-01

    Mexico is characterized by a remarkable richness of Opuntia, mostly at the Meridional Highlands Plateau; it is also here where the greatest richness of Opuntia variants occurs. Most of these variants have been maintained in homegardens; however, the gathering process which originated these homegardens has been disrupted over the past decades, as a result of social change and the destruction of large wild nopaleras. If the variants still surviving in homegardens are lost, these will be hard to...

  12. The Emergence of the Pacific Meridional Overturning Circulation (PMOC) Paced by Obliquity Cycles during the Pliocene

    Science.gov (United States)

    Burls, N.; Fedorov, A. V.; Sigman, D. M.; Jaccard, S.; Tiedemann, R.; Haug, G. H.

    2016-12-01

    Deep water formation in northern high latitudes, as part of the Atlantic meridional overturning circulation (AMOC), is a critical element of modern ocean circulation and climate. For the warm Pliocene, roughly 4 to 2.8 million years ago, we present measurements and modeling evidence that deep water formation also occurred in the North Pacific, supporting another overturning cell - the Pacific meridional overturning circulation (PMOC). The evidence includes calcium carbonate accumulation in Pliocene subarctic Pacific sediments rivaling that of the modern North Atlantic, with pigment, total organic carbon, and redox-sensitive trace metal measurements supporting deep ocean ventilation as the driver of the enhanced calcium carbonate preservation. Together with high accumulation rates of biogenic opal, this implies a bi-directional communication between surface waters and the waters overlying the deep seafloor, and hence deep convection. A Pliocene-like climate simulation reproduces this deep water formation, with co-occurring Atlantic and Pacific overturning cells. The PMOC emerges as a result of the less intense hydrological cycle under Pliocene conditions characterized by a reduced meridional SST gradient. This weaker hydrological cycle leads to the erosion of the North Pacific halocline, allowing deep convection. Examining the data in more detail shows that, while the opal accumulation rate was continuously high, maxima in calcium carbonate accumulation rate were sharp and intermittent. Most likely, these maxima occurred during Northern Hemisphere summer insolation maxima when, as supported by the modeling results, mid-latitude SSTs in the Northern Hemisphere were at a maximum and the meridional SST gradient was particularly weak. These findings suggest that the climate system fluctuated between periods of strong and weak PMOC during the Pliocene. Such fluctuations appear to be a crucial part of Pliocene climate variability on orbital timescales.

  13. Development of Data Acquisition System for Wind Energy Applications

    OpenAIRE

    西本,澄

    1992-01-01

    A Data acquisiton system developed for wind energy applications will be described in this paper. This system is composed of an anemometer with two blades downwind and a computer which processes wind data. Wind energy calculated from an average wind speed is inaccurate, since wind power increases with the cube of wind velocity. To decide the design and the site for a wind turbine system, it is very important to consider wind data on a long term basis, that is the total wind energy and distribu...

  14. Inverse design-momentum, a method for the preliminary design of horizontal axis wind turbines

    International Nuclear Information System (INIS)

    Battisti, L; Soraperra, G; Fedrizzi, R; Zanne, L

    2007-01-01

    Wind turbine rotor prediction methods based on generalized momentum theory BEM routinely used in industry and vortex wake methods demand the use of airfoil tabulated data and geometrical specifications such as the blade spanwise chord distribution. They belong to the category of 'direct design' methods. When, on the other hand, the geometry is deduced from some design objective, we refer to 'inverse design' methods. This paper presents a method for the preliminary design of wind turbine rotors based on an inverse design approach. For this purpose, a generalized theory was developed without using classical tools such as BEM. Instead, it uses a simplified meridional flow analysis of axial turbomachines and is based on the assumption that knowing the vortex distribution and appropriate boundary conditions is tantamount to knowing the velocity distribution. The simple conservation properties of the vortex components consistently cope with the forces and specific work exchange expressions through the rotor. The method allows for rotor arbitrarily radial load distribution and includes the wake rotation and expansion. Radial pressure gradient is considered in the wake. The capability of the model is demonstrated first by a comparison with the classical actuator disk theory in investigating the consistency of the flow field, then the model is used to predict the blade planform of a commercial wind turbine. Based on these validations, the authors postulate the use of a different vortex distribution (i.e. not-uniform loading) for blade design and discuss the effect of such choices on blade chord and twist, force distribution and power coefficient. In addition to the method's straightforward application to the pre-design phase, the model clearly shows the link between blade geometry and performance allowing quick preliminary evaluation of non uniform loading on blade structural characteristics

  15. Sensing the wind profile

    Energy Technology Data Exchange (ETDEWEB)

    Pena, A.

    2009-03-15

    This thesis consists of two parts. The first is a synopsis of the theoretical progress of the study that is based on a number of journal papers. The papers, which constitute the second part of the report, aim to analyze, measure, and model the wind prole in and beyond the surface layer by combining observations from cup anemometers with lidars. The lidar is necessary to extend the measurements on masts at the Horns Rev offshore wind farm and over at land at Hoevsoere, Denmark. Both sensing techniques show a high degree of agreement for wind speed measurements performed at either sites. The wind speed measurements are averaged for several stability conditions and compare well with the surface-layer wind profile. At Hoevsoere, it is sufficient to scale the wind speed with the surface friction velocity, whereas at Horns Rev a new scaling is added, due to the variant roughness length. This new scaling is coupled to wind prole models derived for flow over the sea and tested against the wind proles up to 160 m at Horns Rev. The models, which account for the boundary-layer height in stable conditions, show better agreement with the measurements than compared to the traditional theory. Mixing-length parameterizations for the neutral wind prole compare well with length-scale measurements up to 300 m at Hoevsoere and 950 m at Leipzig. The mixing-length-derived wind proles strongly deviate from the logarithmic wind prole, but agree better with the wind speed measurements. The length-scale measurements are compared to the length scale derived from a spectral analysis performed up to 160 m at Hoevsoere showing high agreement. Mixing-length parameterizations are corrected to account for stability and used to derive wind prole models. These compared better to wind speed measurements up to 300 m at Hoevsoere than the surface-layer wind prole. The boundary-layer height is derived in nearneutral and stable conditions based on turbulent momentum uxes only and in unstable conditions

  16. Agrobiodiversity of cactus pear (Opuntia, Cactaceae in the Meridional Highlands Plateau of Mexico

    Directory of Open Access Journals (Sweden)

    Juan Antonio Reyes-Agüero

    2011-08-01

    Full Text Available Mexico is characterized by a remarkable richness of Opuntia, mostly at the Meridional Highlands Plateau; it is also here where the greatest richness of Opuntia variants occurs. Most of these variants have been maintained in homegardens; however, the gathering process which originated these homegardens has been disrupted over the past decades, as a result of social change and the destruction of large wild nopaleras. If the variants still surviving in homegardens are lost, these will be hard to recover, that is, the millenary cultural heritage from the human groups that populated the Mexican Meridional Highland Plateau will be lost forever. This situation motivated the preparation of a catalogue that records the diversity of wild and cultivated Opuntia variants living in the meridional Highlands Plateau. To this end, 379 samples were obtained in 29 localities, between 1998 and 2003. The information was processed through Twinspan. All specimens were identified and preserved in herbaria. Botanical keys and descriptions were elaborated. The catalogue includes information on 126 variants comprising 18 species. There were species with only one variant (Opuntia atropes, O. cochinera, O. jaliscana, O. leucotricha, O. rzedowskii and O. velutina, two (O. durangensis, O. lindheimeri, O. phaeacantha and O. robusta, five (O. joconostle and O. lasiacantha, seven (O. chavena, 12 (O. hyptiacantha and O. streptacantha, 15 (O. ficus-indica, 22 (O. albicarpa, and up to 34 (O. megacantha. Additionally, 267 common cactus pear names were related to those variants.

  17. Causes and impacts of changes in the stratospheric meridional circulation in a chemistry-climate model

    Energy Technology Data Exchange (ETDEWEB)

    Garny, Hella

    2011-05-13

    The stratospheric meridional circulation is projected to be subject to changes due to enhanced greenhouse-gas concentrations in the atmosphere. This study aims to diagnose and explain long-term changes in the stratospheric meridional circulation using the chemistry-climate model E39CA. The diagnosed strengthening of the circulation is found to be driven by increases in tropical sea surface temperatures which lead to a strengthening and upward shift of the subtropical jets. This enables enhanced vertical propagation of large scale waves into the lower stratosphere, and therefore stronger local wave forcing of the meridional circulation in the tropical lower stratosphere. The impact of changes in transport on the ozone layer is analysed using a newly developed method that allows the separation of the effects of transport and chemistry changes on ozone. It is found that future changes of mean stratospheric ozone concentrations are largely determined by changes in chemistry, while changes in transport of ozone play a minor role. (orig.)

  18. A tilting wind tunnel for fire behavior studies

    Science.gov (United States)

    David R. Weise

    1994-01-01

    The combined effects of wind velocity and slope on wildland fire behavior can be studied in the laboratory using a tilting wind tunnel. The tilting wind tunnel requires a commercially available fan to induce wind and can be positioned to simulate heading and backing fires spreading up and down slope. The tunnel is portable and can be disassembled for transport using a...

  19. Climatology of thermospheric neutral winds over Oukaïmeden Observatory in Morocco

    Science.gov (United States)

    Kaab, Mohamed; Benkhaldoun, Zouhair; Fisher, Daniel J.; Harding, Brian; Bounhir, Aziza; Makela, Jonathan J.; Laghriyeb, Amine; Malki, Khalifa; Daassou, Ahmed; Lazrek, Mohamed

    2017-01-01

    In order to explore coupling between the thermosphere and ionosphere and to address the lack of data relating to thermospheric neutral winds and temperatures over the African sector, a new system of instruments was installed at the Oukaïmeden Observatory located in the high Atlas Mountains, 75 km south of Marrakesh, Morocco (31.206° N, 7.866° W, 22.84° N magnetic). In this work we present the first multi-year results of the climatology of meridional and zonal winds obtained during the period from January 2014 to February 2016, including observations from 648 nights. The measurements are obtained using an imaging Fabry-Pérot interferometer, which measures the 630.0 nm emissions caused by dissociative recombination of O2+. The basic climatology of the winds is as expected, showing zonal winds that are strongly eastward in the early evening just after sunset with a speed of 50 to 100 m s-1 decreasing in magnitude, and reversing directions in the local summer months, towards sunrise. The meridional winds are slightly poleward in the early evening during the local winter, before reversing directions around 21:00 LT. In the local summer months, the meridional winds are equatorward for the entire night, reaching a maximum equatorward speed of 75 m s-1. We compare the observed climatologies of neutral winds to that provided by the recently updated Horizontal Wind Model (HWM14) in order to validate that model's predictions of the thermospheric wind patterns over the eastern portion of Africa. The model captures much of the features in the observational climatologies. The most notable exception is for the zonal winds during local summer, when the maximum eastward wind in the observations occurs approximately 4 h later than seen in the model results.

  20. Lidar Wind Profiler for the NextGen Airportal Project

    Data.gov (United States)

    National Aeronautics and Space Administration — MassTech, Inc. proposes to develop a Lidar Wind Profiler for standoff sensing of concurrent 3-component wind velocities using an eye-safe, rugged, reliable optical...

  1. Wind noise under a pine tree canopy.

    Science.gov (United States)

    Raspet, Richard; Webster, Jeremy

    2015-02-01

    It is well known that infrasonic wind noise levels are lower for arrays placed in forests and under vegetation than for those in open areas. In this research, the wind noise levels, turbulence spectra, and wind velocity profiles are measured in a pine forest. A prediction of the wind noise spectra from the measured meteorological parameters is developed based on recent research on wind noise above a flat plane. The resulting wind noise spectrum is the sum of the low frequency wind noise generated by the turbulence-shear interaction near and above the tops of the trees and higher frequency wind noise generated by the turbulence-turbulence interaction near the ground within the tree layer. The convection velocity of the low frequency wind noise corresponds to the wind speed above the trees while the measurements showed that the wind noise generated by the turbulence-turbulence interaction is near stationary and is generated by the slow moving turbulence adjacent to the ground. Comparison of the predicted wind noise spectrum with the measured wind noise spectrum shows good agreement for four measurement sets. The prediction can be applied to meteorological estimates to predict the wind noise under other pine forests.

  2. WIND VARIABILITY IN BZ CAMELOPARDALIS

    International Nuclear Information System (INIS)

    Honeycutt, R. K.; Kafka, S.; Robertson, J. W.

    2013-01-01

    Sequences of spectra of the nova-like cataclysmic variable (CV) BZ Cam were acquired on nine nights in 2005-2006 in order to study the time development of episodes of wind activity known to occur frequently in this star. We confirm the results of Ringwald and Naylor that the P-Cygni absorption components of the lines mostly evolve from higher expansion velocity to lower velocity as an episode progresses. We also commonly find blueshifted emission components in the Hα line profile, whose velocities and durations strongly suggest that they are also due to the wind. Curiously, Ringwald and Naylor reported common occurrences of redshifted Hα emission components in their BZ Cam spectra. We have attributed these emission components in Hα to occasions when gas concentrations in the bipolar wind (both front side and back side) become manifested as emission lines as they move beyond the disk's outer edge. We also suggest, based on changes in the P-Cygni profiles during an episode, that the progression from larger to smaller expansion velocities is due to the higher velocity portions of a wind concentration moving beyond the edge of the continuum light of the disk first, leaving a net redward shift of the remaining absorption profile. We derive a new orbital ephemeris for BZ Cam, using the radial velocity of the core of the He I λ5876 line, finding P = 0.15353(4). Using this period, the wind episodes in BZ Cam are found to be concentrated near the inferior conjunction of the emission line source. This result helps confirm that the winds in nova-like CVs are often phase dependent, in spite of the puzzling implication that such winds lack axisymmetry. We argue that the radiation-driven wind in BZ Cam receives an initial boost by acting on gas that has been lifted above the disk by the interaction of the accretion stream with the disk, thereby imposing flickering timescales onto the wind events, as well as leading to an orbital modulation of the wind due to the non

  3. Global empirical wind model for the upper mesosphere/lower thermosphere. I. Prevailing wind

    Directory of Open Access Journals (Sweden)

    Y. I. Portnyagin

    Full Text Available An updated empirical climatic zonally averaged prevailing wind model for the upper mesosphere/lower thermosphere (70-110 km, extending from 80°N to 80°S is presented. The model is constructed from the fitting of monthly mean winds from meteor radar and MF radar measurements at more than 40 stations, well distributed over the globe. The height-latitude contour plots of monthly mean zonal and meridional winds for all months of the year, and of annual mean wind, amplitudes and phases of annual and semiannual harmonics of wind variations are analyzed to reveal the main features of the seasonal variation of the global wind structures in the Northern and Southern Hemispheres. Some results of comparison between the ground-based wind models and the space-based models are presented. It is shown that, with the exception of annual mean systematic bias between the zonal winds provided by the ground-based and space-based models, a good agreement between the models is observed. The possible origin of this bias is discussed.

    Key words: Meteorology and Atmospheric dynamics (general circulation; middle atmosphere dynamics; thermospheric dynamics

  4. MLT winds and diurnal tides at southern low latitudes in the period 1999-2008

    Science.gov (United States)

    Rodrigues de Araujo, Luciana; Takahashi, Hisao; Clemesha, Barclay; Batista, Paulo; Lima, Lourivaldo

    Meteor radar measurements obtained during the time intervals from March 1999 to July 2006 and from September 2007 to October 2008, at Cachoeira Paulista (22.7° S, 45.0° W), Brazil, have been analyzed to investigate long-term trends and solar activity-induced variations in the mesosphere and lower thermosphere region (MLT) dynamics. Regression analyses with a dependence on solar activity and time have revealed a possible effect of the solar cycle upon monthly zonal and meridional wind behavior, in which solar activity may have contributed to weaken eastward winds, increase westward and meridional winds in some height ranges and time periods. Diurnal and semidiurnal tide amplitudes also have been analyzed and the results point out that the diurnal tides for solar minimum years are amplifies, whereas the amplitudes for semidiurnal tides showed an opposite behavior.

  5. Wind Structure and Wind Loading

    DEFF Research Database (Denmark)

    Brorsen, Michael

    The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...... of windhe interaction between wind and structures, where it is shown that wind loading depends strongly on this interaction...

  6. The Dependence of the Peak Velocity of High-Speed Solar Wind Streams as Measured in the Ecliptic by ACE and the STEREO satellites on the Area and Co-Latitude of their Solar Source Coronal Holes

    DEFF Research Database (Denmark)

    Hofmeister, Stefan J.; Veronig, Astrid; Temmer, Manuela

    2018-01-01

    We study the properties of 115 coronal holes in the time‐range from 2010/08 to 2017/03, the peak velocities of the corresponding high‐speed streams as measured in the ecliptic at 1AU, and the corresponding changes of the Kp index as marker of their geo‐effectiveness. We find that the peak velocit...

  7. Wind height distribution influence on offshore wind farm feasibility study

    Science.gov (United States)

    Benassai, Guido; Della Morte, Renata; Matarazzo, Antonio; Cozzolino, Luca

    2015-04-01

    The economic feasibility of offshore wind power utilization depends on the favourable wind conditions offshore as compared to sites on land. The higher wind speeds have to compensate the additional cost of offshore developments. However, not only the mean wind speed is different, but the whole flow regime, as can be seen in the vertical wind speed profile. The commonly used models to describe this profile have been developed mainly for land sites, so they have to be verified on the basis of field data. Monin-Obukhov theory is often used for the description of the wind speed profile at a different height with respect to a measurement height. Starting from the former, , the profile is predicted using two parameters, Obukhov length and sea surface roughness. For situations with near-neutral and stable atmospheric stratification and long (>30km) fetch, the wind speed increase with height is larger than what is predicted from Monin-Obukhov theory. It is also found that this deviation occurs at wind speeds important for wind power utilization, mainly at 5-9 ms-1. In the present study the influence of these aspects on the potential site productivity of an offshore wind farm were investigated, namely the deviation from the theory of Monin-Obukhov due to atmospheric stability and the influence of the fetch length on the Charnock model. Both these physical effects were discussed and examined in view of a feasibility study of a site for offshore wind farm in Southern Italy. Available data consisted of time histories of wind speeds and directions collected by National Tidegauge Network (Rete Mareografica Nazionale) at the height of 10m a.s.l. in ports. The theory of Monin-Obukhov was used to extrapolate the data to the height of the wind blades, while the Charnock model was used to extend the wind speed on the sea surface from the friction velocity on the ground. The models described were used to perform calculations for a feasibility study of an offshore wind farm in Southern

  8. Three-pattern decomposition of global atmospheric circulation: part II—dynamical equations of horizontal, meridional and zonal circulations

    Science.gov (United States)

    Hu, Shujuan; Cheng, Jianbo; Xu, Ming; Chou, Jifan

    2018-04-01

    The three-pattern decomposition of global atmospheric circulation (TPDGAC) partitions three-dimensional (3D) atmospheric circulation into horizontal, meridional and zonal components to study the 3D structures of global atmospheric circulation. This paper incorporates the three-pattern decomposition model (TPDM) into primitive equations of atmospheric dynamics and establishes a new set of dynamical equations of the horizontal, meridional and zonal circulations in which the operator properties are studied and energy conservation laws are preserved, as in the primitive equations. The physical significance of the newly established equations is demonstrated. Our findings reveal that the new equations are essentially the 3D vorticity equations of atmosphere and that the time evolution rules of the horizontal, meridional and zonal circulations can be described from the perspective of 3D vorticity evolution. The new set of dynamical equations includes decomposed expressions that can be used to explore the source terms of large-scale atmospheric circulation variations. A simplified model is presented to demonstrate the potential applications of the new equations for studying the dynamics of the Rossby, Hadley and Walker circulations. The model shows that the horizontal air temperature anomaly gradient (ATAG) induces changes in meridional and zonal circulations and promotes the baroclinic evolution of the horizontal circulation. The simplified model also indicates that the absolute vorticity of the horizontal circulation is not conserved, and its changes can be described by changes in the vertical vorticities of the meridional and zonal circulations. Moreover, the thermodynamic equation shows that the induced meridional and zonal circulations and advection transport by the horizontal circulation in turn cause a redistribution of the air temperature. The simplified model reveals the fundamental rules between the evolution of the air temperature and the horizontal, meridional

  9. Controls on the meridional extent of tropical precipitation and its contraction under global warming

    Science.gov (United States)

    Donohoe, A.

    2017-12-01

    A method for decomposing changes and variability in the spatial structure of tropical precipitation into shifting (meridional translation), contracting, and intensifying modes of variability is introduced. We demonstrate that the shifting mode of tropical precipitation explains very little (20%) more of the tropical precipitation changes and variability. Furthermore, the contraction of tropical precipitation is highly correlated (R2 > 0.95) with an intensification of the precipitation in both the observations and forced modeled simulations. These results suggest that the simultaneous contraction and intensification of tropical precipitation is the dominant mode of variability and changes under external forcing. We speculate that tropical surface temperature controls this concurrent variability. Indeed, models robustly predict that tropical precipitation increases and meridionally contracts in response to increased CO2 and is reduced and meridionally expanded under glacial forcing and boundary conditions. In contrast, the directionality of the tropical precipitation shift is both ambiguous and small in magnitude in response to increased CO2. Furthermore, the ratio of the contraction/expansion to intensification/reduction is consistent in the continuum of climate states from the glacial climate to a modern climate to a 4XCO2 climate suggesting that the intensification and contraction are linked together via a single mechanism. We examine two mechanisms responsible for the contraction of the precipitation under global warming : i. the reduction of the seasonal cycle of energy input to the atmosphere due to sea ice retreat that results in the tropical precipitation remaining closer to the equator during the solsticial seasons and; ii. the increased gross moist stability of the tropical atmosphere as the surface warms resulting in a weaker cross-equatorial Hadley circulation during the solsticial seasons.

  10. Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum

    OpenAIRE

    Felis, Thomas; McGregor, Helen V.; Linsley, Braddock K.; Tudhope, Alexander; Gagan, M. K.; Suzuki, Atsushi; Inoue, Mayuri; Thomas, Alex; Esat, T. M.; Thompson, William G.; Tiwari, Manish; Potts, Don; Mudelsee, Manfred; Yokoyama, Y.; Webster, Jody M.

    2014-01-01

    Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and d18O for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1–2 C larger temperaturedecrease between 17 and 20S about 20,000 to 13,...

  11. MAGNETIC DRAG ON HOT JUPITER ATMOSPHERIC WINDS

    International Nuclear Information System (INIS)

    Perna, Rosalba; Menou, Kristen; Rauscher, Emily

    2010-01-01

    Hot Jupiters, with atmospheric temperatures T ∼> 1000 K, have residual thermal ionization levels sufficient for the interaction of ions with the planetary magnetic field to result in a sizable magnetic drag on the (neutral) atmospheric winds. We evaluate the magnitude of magnetic drag in a representative three-dimensional atmospheric model of the hot Jupiter HD 209458b and find that it is a plausible mechanism to limit wind speeds in this class of atmospheres. Magnetic drag has a strong geometrical dependence, both meridionally and from the dayside to the nightside (in the upper atmosphere), which could have interesting consequences for the atmospheric flow pattern. By extension, close-in eccentric planets with transiently heated atmospheres will experience time-variable levels of magnetic drag. A robust treatment of magnetic drag in circulation models for hot atmospheres may require iterated solutions to the magnetic induction and Saha equations as the hydrodynamic flow is evolved.

  12. Aerodynamic Analysis of a Vertical Axis Wind Turbine in a Diffuser

    NARCIS (Netherlands)

    Geurts, B.M.; Simao Ferreira, C.; Van Bussel, G.J.W.

    Wind energy in the urban environment faces complex and often unfavorable wind conditions. High turbulence, lower average wind velocities and rapid changes in the wind direction are common phenomena in the complex built environments. A possible way to improve the cost-efficiency of urban wind

  13. Magneto-optic Doppler analyzer: a new instrument to measure mesopause winds

    Science.gov (United States)

    Williams, Bifford P.; Tomczyk, Steven

    1996-11-01

    The magneto-optic Doppler analyzer (MODA) is a new type of passive optical instrument that one can use to measure the Doppler shift of the sodium nightglow emitted at approximately 91 km near the mesopause. From this measurement, horizontal wind signatures are inferred. The MODA is based on a sodium vapor magneto-optic filter that provides inherent wavelength stability at a low cost. The instrument has been used to take nightly zonal and meridional wind measurements since October 1994 at Niwot Ridge, Colorado (40 N, 105 W). We obtained an internally consistent wind signal and measured the semidiurnal tide for several seasons.

  14. Meridional lenticular astigmatism associated with bilateral concurrent uveal metastases in renal cell carcinoma

    Directory of Open Access Journals (Sweden)

    Priluck JC

    2012-11-01

    Full Text Available Joshua C Priluck, Sandeep Grover, KV ChalamDepartment of Ophthalmology, University of Florida College of Medicine, Jacksonville, FL, USAPurpose: To demonstrate a case illustrating meridional lenticular astigmatism as a result of renal cell carcinoma uveal metastases.Methods: Case report with images.Results: Clinical findings and diagnostic testing of a patient with acquired meridional lenticular astigmatism are described. The refraction revealed best-corrected visual acuity of 20/20–1 OD (−2.50 + 0.25 × 090 and 20/50 OS (−8.25 + 3.25 × 075. Bilateral concurrent renal cell carcinoma metastases to the choroid and ciliary body are demonstrated by utilizing ultrasonography, ultrawidefield fluorescein angiography, and unique spectral-domain optical coherence tomography.Conclusions: Metastatic disease should be included in the differential of acquired astigmatism. Spectral-domain optical coherence tomography, ultrawidefield fluorescein angiography, and ultrasonography have roles in delineating choroidal metastases.Keywords: astigmatism, metastasis, optical coherence tomography, renal cell carcinoma

  15. An electrical analogy relating the Atlantic multidecadal oscillation to the Atlantic meridional overturning circulation.

    Directory of Open Access Journals (Sweden)

    Bruce E Kurtz

    Full Text Available The Atlantic meridional overturning circulation (AMOC is the northward flow of surface water to subpolar latitudes where deepwater is formed, balanced by southward abyssal flow and upwelling in the vicinity of the Southern Ocean. It is generally accepted that AMOC flow oscillates with a period of 60-80 years, creating a regular variation in North Atlantic sea surface temperature known as the Atlantic multidecadal oscillation (AMO. This article attempts to answer two questions: how is the AMOC driven and why does it oscillate? Using methods commonly employed by chemical engineers for analyzing processes involving flowing liquids, apparently not previously applied to trying to understand the AMOC, an equation is developed for AMOC flow as a function of the meridional density gradient or the corresponding temperature gradient. The equation is based on the similarity between the AMOC and an industrial thermosyphon loop cooler, which circulates a heat transfer liquid without using a mechanical pump. Extending this equation with an analogy between the flow of heat and electricity explains why the AMOC flow oscillates and what determines its period. Calculated values for AMOC flow and AMO oscillation period are in good agreement with measured values.

  16. Meridional distribution and seasonal variation of stable oxygen isotope ratio of precipitation in the Southern Ocean

    Directory of Open Access Journals (Sweden)

    Kayo Nakamura

    2010-07-01

    Full Text Available The stable oxygen isotope ratio(δ^O in precipitation is known to have important meridional and seasonal variations, but there are almost no measurements of δ^O in precipitation over polar oceans. The present research took advantage of 4 opportunities for in situ observations in summer and winter at high latitudes in the Southern Ocean. In addition, we analyzed samples of precipitation at Syowa Station in 2008 to obtain year-round data. Based on these data, we consider the meridional and seasonal variations of δ^O in precipitation over the Southern Ocean. In general, δ^O decreases with increasing latitude, and is lower in winter than in summer. The latitude gradient is stronger in winter. At 60°S, δ^O is -5.4‰ and -11.3‰ in summer and winter, respectively, while the corresponding figures at 66°S are -10.5‰ and -20.8‰. These results will help us understand the mechanisms of the salinity distribution and its variation in the Antarctic Ocean.

  17. Intensification of the meridional temperature gradient in the Great Barrier Reef following the Last Glacial Maximum

    Science.gov (United States)

    Felis, Thomas; McGregor, Helen V.; Linsley, Braddock K.; Tudhope, Alexander W.; Gagan, Michael K.; Suzuki, Atsushi; Inoue, Mayuri; Thomas, Alexander L.; Esat, Tezer M.; Thompson, William G.; Tiwari, Manish; Potts, Donald C.; Mudelsee, Manfred; Yokoyama, Yusuke; Webster, Jody M.

    2014-01-01

    Tropical south-western Pacific temperatures are of vital importance to the Great Barrier Reef (GBR), but the role of sea surface temperatures (SSTs) in the growth of the GBR since the Last Glacial Maximum remains largely unknown. Here we present records of Sr/Ca and δ18O for Last Glacial Maximum and deglacial corals that show a considerably steeper meridional SST gradient than the present day in the central GBR. We find a 1–2 °C larger temperature decrease between 17° and 20°S about 20,000 to 13,000 years ago. The result is best explained by the northward expansion of cooler subtropical waters due to a weakening of the South Pacific gyre and East Australian Current. Our findings indicate that the GBR experienced substantial meridional temperature change during the last deglaciation, and serve to explain anomalous deglacial drying of northeastern Australia. Overall, the GBR developed through significant SST change and may be more resilient than previously thought. PMID:24937320

  18. Dynamics of the global meridional ice flow of Europa's icy shell

    Science.gov (United States)

    Ashkenazy, Yosef; Sayag, Roiy; Tziperman, Eli

    2018-01-01

    Europa is one of the most probable places in the solar system to find extra-terrestrial life1,2, motivating the study of its deep ( 100 km) ocean3-6 and thick icy shell3,7-11. The chaotic terrain patterns on Europa's surface12-15 have been associated with vertical convective motions within the ice8,10. Horizontal gradients of ice thickness16,17 are expected due to the large equator-to-pole gradient of surface temperature and can drive a global horizontal ice flow, yet such a flow and its observable implications have not been studied. We present a global ice flow model for Europa composed of warm, soft ice flowing beneath a cold brittle rigid ice crust3. The model is coupled to an underlying (diffusive) ocean and includes the effect of tidal heating and convection within the ice. We show that Europa's ice can flow meridionally due to pressure gradients associated with equator-to-pole ice thickness differences, which can be up to a few km and can be reduced both by ice flow and due to ocean heat transport. The ice thickness and meridional flow direction depend on whether the ice convects or not; multiple (convecting and non-convecting) equilibria are found. Measurements of the ice thickness and surface temperature from future Europa missions18,19 can be used with our model to deduce whether Europa's icy shell convects and to constrain the effectiveness of ocean heat transport.

  19. Wind power

    International Nuclear Information System (INIS)

    Gipe, P.

    2007-01-01

    This book is a translation of the edition published in the USA under the title of ''wind power: renewable energy for home, farm and business''. In the wake of mass blackouts and energy crises, wind power remains a largely untapped resource of renewable energy. It is a booming worldwide industry whose technology, under the collective wing of aficionados like author Paul Gipe, is coming of age. Wind Power guides us through the emergent, sometimes daunting discourse on wind technology, giving frank explanations of how to use wind technology wisely and sound advice on how to avoid common mistakes. Since the mid-1970's, Paul Gipe has played a part in nearly every aspect of wind energy development from installing small turbines to promoting wind energy worldwide. As an American proponent of renewable energy, Gipe has earned the acclaim and respect of European energy specialists for years, but his arguments have often fallen on deaf ears at home. Today, the topic of wind power is cropping up everywhere from the beaches of Cape Cod to the Oregon-Washington border, and one wind turbine is capable of producing enough electricity per year to run 200 average American households. Now, Paul Gipe is back to shed light on this increasingly important energy source with a revised edition of Wind Power. Over the course of his career, Paul Gipe has been a proponent, participant, observer, and critic of the wind industry. His experience with wind has given rise to two previous books on the subject, Wind Energy Basics and Wind Power for Home and Business, which have sold over 50,000 copies. Wind Power for Home and Business has become a staple for both homeowners and professionals interested in the subject, and now, with energy prices soaring, interest in wind power is hitting an all-time high. With chapters on output and economics, Wind Power discloses how much you can expect from each method of wind technology, both in terms of energy and financial savings. The book updated models

  20. A mixing method for traceable air velocity measurements

    International Nuclear Information System (INIS)

    Sillanpää, S; Heinonen, M

    2008-01-01

    A novel and quite simple method to establish a traceability link between air velocity and the national standards of mass and time is presented in this paper. The method is based on the humidification of flowing air before the blower of a wind tunnel with a known mass flow of water. Then air velocity can be calculated as a function of humidification water flow. The method is compared against a Pitot-tube-based velocity measurement in a wind tunnel at the MIKES. The results of these two different methods agreed well, with a maximum difference of 0.7%

  1. Calculations of the cosmic ray modulation in interplanetary space taking into account the possible dependence of the transport travel for the scattering of the particles and of the velocity of the solar winds on the angles they make with the helioequator plane: The case of isotropic diffusion

    Science.gov (United States)

    Dorman, L. I.; Kobilinski, Z.

    1975-01-01

    The modulation of galactic cosmic rays is studied by the magnetic heterogeneities stream on the assumption that the diffusion coefficient is reduced whereas the solar wind velocity is increased with the growth of the angle between the sun's rotation axis and the direction of solar plasma motion. The stationary plane problem of isotropic diffusion is solved as it applies to two cases: (1) with due account of particle retardation by the antiphermium mechanism; and (2) without an account of the above mechanism. This problem is solved by the grid method in the polar coordinate system. The results of the calculations are followed by a discussion of the method of solution and of the errors.

  2. Solar Wind Variation with the Cycle

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... The average solar wind density, velocity and temperature measured at the Earth's orbit show specific decadal variations and trends, which are of the order of the first tens per cent during the last three solar cycles. Statistical, spectral and correlation characteristics of the solar wind are reviewed with the ...

  3. Effect of fall wind on wind power generation; Furyoku hatsuden ni okeru dashikaze no koka

    Energy Technology Data Exchange (ETDEWEB)

    Nagai, H. [Nihon University, Tokyo (Japan)

    1997-11-25

    Wind conditions in Arakawa Town, Niigata Prefecture, were surveyed by anemometers and anemoscopes installed at 3 different points, and the data are analyzed to develop the prediction model for investigating possibility of introduction of wind mills there. Outlined herein is power generated by fall wind by comparing predicted power availability with the actual results. In order to investigate possibility of power generation by fall wind, the wind conditions and power availability are simulated using the observed wind condition data. Predicted wind velocity involves a large error at a point where frequency of prevailing wind direction is high, and direction in which average wind velocity is high coincides with direction in which land is slanted at a high slope. Fall wind occurs locally for geographical reasons. Location of the wind mill must be carefully considered, because it is complex, although potentially gives a larger quantity of power. A wind mill of 400kW can produce power of around 600MWh annually, when it is located at the suited site confirmed by the wind condition analysis results. 6 refs., 5 figs., 6 tabs.

  4. Comparative study of the behavior of wind-turbines in a wind farm

    Energy Technology Data Exchange (ETDEWEB)

    Migoya, Emilio; Crespo, Antonio; Garcia, Javier; Manuel, Fernando; Jimenez, Angel [Universidad Politecnica de Madrid (UPM), Madrid (Spain). Departamento de Ingenieria Energetica y Fluidomecanica, Laboratorio de Mecanica de Fluidos; Moreno, Fermin [Comision Nacional de la Energia, Madrid (Spain); Costa, Alexandre [Energia Eolica, Division de Energias Renovables, CIEMAT, Madrid (Spain)

    2007-10-15

    The Sotavento wind farm is an experimental wind farm which has different types of wind turbines. It is located in an area whose topography is moderately complex, and where wake effects can be significant. One of the objectives of Sotavento wind farm is to compare the performances of the different machines; particularly regarding power production, maintenance and failures. However, because of wakes and topography, the different machines are not working under identical conditions. Two linearized codes have been used to estimate topography effects: UPMORO and WAsP. For wind directions in which topography is abrupt, the non-linear flow equations have been solved with the commercial code FLUENT, although the results are only qualitatively used. For wake effects, the UPMPARK code has been applied. As a result, the incident velocity over each wind turbine is obtained, and the power production is estimated by means of the power curve of each machine. Experimental measurements give simultaneously the wind characteristics at the measuring stations, the wind velocity, at the nacelle anemometer, and the power production of each wind turbine. These experimental results are employed to validate the numerical predictions. The main objective of this work is to deduce and validate a relationship between the wind characteristics measured in the anemometers and the wind velocity and the power output in each machine. (author)

  5. Optimization of wind speed on dispersion of pollutants using ...

    Indian Academy of Sciences (India)

    https://www.ias.ac.in/article/fulltext/sadh/040/05/1657-1666. Keywords. Receptor model; dispersion model; wind velocity; optimization; coupled model. ... The current research work proposed a coupled receptor-dispersion model to reduce the difference between predicted concentrations through optimized wind velocity used ...

  6. Interannual Variability of the Meridional Width of the Baiu Rainband in June and the Associated Large-Scale Atmospheric Circulations

    Science.gov (United States)

    Tsuji, K.; Tomita, T.

    2016-12-01

    Baiu front, which is defined as a boundary between tropical and polar air masses in the East Asia-western North Pacific sector in boreal early summer, slowly migrates northward with the daily meridional swings. Thus, the interannual variability of meridional width of the baiu rainband reflects the slow northward migration and the daily meridional swings of the baiu front. This study focuses on the meridional width of baiu rainband only in June when the baiu front extends on Japan, and investigates how the width is related to the rainfall of Japan with discussions of associated anomalous large-scale atmospheric circulations. The meridional width of baiu rainband is defined based on the monthly-mean precipitation rate of June, whose threshold is 5mm day-1 that is averaged in 130°-150°E. There is a significant positive correlation between the variations of southern and northern edges of the baiu rainband in June. However, the interannual variance of the southern edge is almost twice larger than that of the northern one. That is, the interannual variability of the meridional width is chiefly caused by the variations of southern edge, and the contribution of northern ones is small. When the meridonal width is narrow (wide), an anomalous anticyclonic (cyclonic) circulation appears to the south of Japan, and the precipitation rate increases (decreases) in the western part of Japan while decreases (increases) in the counterpart. In other words, a local dipole with a node at 140°E appears around Japan in the baiu rainfall anomalies. The anomalous anticyclonic (cyclonic) circulation to the south of Japan, which controls the interannual variability of meridional width of the baiu rainband, is induced by the strength of Indian summer monsoon. When the convective activity of Indian summer monsoon is strong (week), the Tibetan high in the upper troposphere extends more (less) eastward. The induced stronger (weaker) descent leads stronger (weaker) Bonin high in the western

  7. Rotor and wind turbine formalism

    DEFF Research Database (Denmark)

    Branlard, Emmanuel Simon Pierre

    2017-01-01

    The main conventions used in this book for the study of rotors are introduced in this chapter. The main assumptions and notations are provided. The formalism specific to wind turbines is presented. The forces, moments, velocities and dimensionless coefficients used in the study of rotors...

  8. Wind dependence on the flow rate in a natural draught cooling tower

    International Nuclear Information System (INIS)

    Baer, E.; Ernst, G.; Wurz, D.

    1981-01-01

    The efficiency of a natural draught cooling tower depends, among other things, on the effect of the wind on the flow in the tower stack. Determinations were made on a natural draught wet cooling tower 100 metres high, for the purpose of studying this effects. As characteristic quantity, a typical height was determined, the values of which were worked out from the results of the measurements. The efficiency of the stack is affected the most in the case of average wind velocities (when the velocity of the wind is about equal to the mean velocity of the plume). This effect diminishes when the velocity of the wind increases. In the case of average wind velocities, the direction of the wind has an effect, owing to the neighbouring buildings; for slightly greater wind velocities, no effect could be found [fr

  9. Quasi-biennial oscillation signatures in the diurnal tidal winds over Cachoeira Paulista, Brazil

    Science.gov (United States)

    de Araújo, Luciana Rodrigues; Lima, Lourivaldo Mota; Jacobi, Christoph; Batista, Paulo Prado

    2017-03-01

    Mesosphere/lower thermosphere winds obtained by meteor radar over Cachoeira Paulista (22.7° S, 45.0° W), Brazil, have been used to investigate the interannual variability of the diurnal tidal (DT) wind amplitude. The monthly DT displays year to year variations and their amplitudes are strongest during the westerly phase of the quasi-biennial oscillation (QBO) at the 30 hPa level. This can be observed in all seasons in the meridional component, whilst in the zonal component the signal is clearer during austral autumn, when the diurnal tide is strongest in this latitude. The spectrum obtained from the deseasonalized amplitudes shows a peak near 26 months in the meridional component, which can be associated to the stratospheric QBO. The QBO modulation of the DT amplitude shows a quasi-decadal variation, and it is stronger during the maximum of the solar cycle.

  10. Quality assessment of weather radar wind profiles during bird migration

    NARCIS (Netherlands)

    Holleman, I.; van Gasteren, H.; Bouten, W.

    2008-01-01

    Wind profiles from an operational C-band Doppler radar have been combined with data from a bird tracking radar to assess the wind profile quality during bird migration. The weather radar wind profiles (WRWPs) are retrieved using the well-known volume velocity processing (VVP) technique. The X-band

  11. Coastal Ohio Wind Project

    Energy Technology Data Exchange (ETDEWEB)

    Gorsevski, Peter [Bowling Green State Univ., OH (United States); Afjeh, Abdollah [Univ. of Toledo, OH (United States); Jamali, Mohsin [Univ. of Toledo, OH (United States); Bingman, Verner [Bowling Green State Univ., OH (United States)

    2014-04-04

    reduced the wake size and enhanced the vortices in the flow downstream of the turbine-tower compared with the tower alone case. Mean and rms velocity distributions from hot wire anemometer data confirmed that in a downwind configuration, the wake of the tower dominates the flow, thus the flow fields of a tower alone and tower-turbine combinations are nearly the same. For the upwind configuration, the mean velocity shows a narrowing of the wake compared with the tower alone case. The downwind configuration wake persisted longer than that of an upwind configuration; however, it was not possible to quantify this difference because of the size limitation of the wind tunnel downstream of the test section. The water tunnel studies demonstrated that the scale model studies could be used to adequately produce accurate motions to model the motions of a wind turbine platform subject to large waves. It was found that the important factors that affect the platform is whether the platform is submerged or surface piercing. In the former, the loads on the platform will be relatively reduced whereas in the latter case, the structure pierces the wave free surface and gains stiffness and stability. The other important element that affects the movement of the platform is depth of the sea in which the wind turbine will be installed. Furthermore, the wildlife biology component evaluated migratory patterns by different monitoring systems consisting of marine radar, thermal IR camera and acoustic recorders. The types of radar used in the project are weather surveillance radar and marine radar. The weather surveillance radar (1988 Doppler), also known as Next Generation Radar (NEXRAD), provides a network of weather stations in the US. Data generated from this network were used to understand general migratory patterns, migratory stopover habitats, and other patterns caused by the effects of weather conditions. At a local scale our marine radar was used to complement the datasets from NEXRAD and

  12. OCEAN CIRCULATION. Observing the Atlantic Meridional Overturning Circulation yields a decade of inevitable surprises.

    Science.gov (United States)

    Srokosz, M A; Bryden, H L

    2015-06-19

    The importance of the Atlantic Meridional Overturning Circulation (AMOC) heat transport for climate is well acknowledged. Climate models predict that the AMOC will slow down under global warming, with substantial impacts, but measurements of ocean circulation have been inadequate to evaluate these predictions. Observations over the past decade have changed that situation, providing a detailed picture of variations in the AMOC. These observations reveal a surprising degree of AMOC variability in terms of the intraannual range, the amplitude and phase of the seasonal cycle, the interannual changes in strength affecting the ocean heat content, and the decline of the AMOC over the decade, both of the latter two exceeding the variations seen in climate models. Copyright © 2015, American Association for the Advancement of Science.

  13. Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming.

    Science.gov (United States)

    Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli

    2016-03-22

    Interdecadal variability of the Atlantic Meridional Overturning Circulation (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ∼50 y to ∼20 y, and the amplitude is reduced by ∼60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves.

  14. A reconstructed South Atlantic Meridional Overturning Circulation time series since 1870

    Science.gov (United States)

    Lopez, Hosmay; Goni, Gustavo; Dong, Shenfu

    2017-04-01

    This study reconstructs a century-long South Atlantic Meridional Overturning Circulation (SAMOC) index. The reconstruction is possible due to its covariability with sea surface temperature (SST). A singular value decomposition (SVD) method is applied to the correlation matrix of SST and SAMOC. The SVD is performed on the trained period (1993 to present) for which Expendable Bathythermographs and satellite altimetry observations are available. The joint modes obtained are used in the reconstruction of a monthly SAMOC time series from 1870 to present. The reconstructed index is highly correlated to the observational based SAMOC time series during the trained period and provides a long historical estimate. It is shown that the Interdecadal Pacific Oscillation (IPO) is the leading mode of SAMOC-SST covariability, explaining 85% with the Atlantic Niño accounting for less than 10%. The reconstruction shows that SAMOC has recently shifted to an anomalous positive period, consistent with a recent positive shift of the IPO.

  15. Tailoring Meridional and Seasonal Radiative Forcing by Sulfate Aerosol Solar Geoengineering

    Science.gov (United States)

    Dai, Z.; Weisenstein, D. K.; Keith, D. W.

    2018-01-01

    We study the possibility of designing solar radiation management schemes to achieve a desired meridional radiative forcing (RF) profile using a two-dimensional chemistry-transport-aerosol model. Varying SO2 or H2SO4 injection latitude, altitude, and season, we compute RF response functions for a broad range of possible injection schemes, finding that linear combinations of these injection cases can roughly achieve RF profiles that have been proposed to accomplish various climate objectives. Globally averaged RF normalized by the sulfur injection rate (the radiative efficacy) is largest for injections at high altitudes, near the equator, and using emission of H2SO4 vapor into an aircraft wake to produce accumulation-mode particles. There is a trade-off between radiative efficacy and control as temporal and spatial control is best achieved with injections at lower altitudes and higher latitudes. These results may inform studies using more realistic models that couple aerosol microphysics, chemistry, and stratospheric dynamics.

  16. Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming

    Science.gov (United States)

    Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli

    2016-03-01

    Interdecadal variability of the Atlantic Meridional Overturning Circulation (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ˜50 y to ˜20 y, and the amplitude is reduced by ˜60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves.

  17. There is no real evidence for a diminishing trend of the Atlantic meridional overturning circulation

    Directory of Open Access Journals (Sweden)

    A. Parker

    2016-01-01

    Full Text Available The Atlantic Meridional Overturning Circulation (AMOC is part of the great ocean “conveyor belt” that circulates heat around the globe. Since the early 2000s, ocean sensors have started to monitor the AMOC, but the measurements are still far from accurate and the time window does not permit the separation of short term variability from a longer term trend. Other works have claimed that global warming is slowing down the AMOC, based on models and proxies of temperatures. Some other observations demonstrate a stable circulation of the oceans. By using tide gauge data complementing recent satellite and ocean sensor observations, the stability of the AMOC is shown to go back to 1860. It is concluded that no available information has the due accuracy and time coverage to show a clear trend outside the inter-annual and multi-decadal variability in the direction of increasing or decreasing strength over the last decades.

  18. Vertical velocities at an ocean front

    Directory of Open Access Journals (Sweden)

    Pedro Vélez-Belchí

    2001-07-01

    Full Text Available Simple scaling arguments conclude that the dominant motions in the ocean are horizontal. However, the vertical velocity plays a crucial role, connecting the active upper layer with the deep ocean. Vertical velocities are mostly associated with the existence of non-transient atmospheric wind forcing or with the presence of mesoscale features. The former are the well known upwelling areas, usually found at the eastern side of the oceans and characterised by upward vertical velocities. The latter have been observed more recently in a number of areas of the world´s oceans, where the vertical velocity has been found to be of the order of several tens of meters per day, that is, an order of magnitude higher than the largest vertical velocity usually observed in upwelling areas. Nevertheless, at present, vertical velocities cannot be measured and indirect methods are therefore needed to estimate them. In this paper, the vertical velocity field is inferred via the quasi-geostrophic omega equation, using density data from a quasi-permanent upper ocean front located at the northern part of the western Alborán gyre.

  19. Meridional overturning circulation conveys fast acidification to the deep Atlantic Ocean

    Science.gov (United States)

    Perez, Fiz F.; Fontela, Marcos; García-Ibáñez, Maribel I.; Mercier, Herlé; Velo, Anton; Lherminier, Pascale; Zunino, Patricia; de La Paz, Mercedes; Alonso-Pérez, Fernando; Guallart, Elisa F.; Padin, Xose A.

    2018-02-01

    Since the Industrial Revolution, the North Atlantic Ocean has been accumulating anthropogenic carbon dioxide (CO2) and experiencing ocean acidification, that is, an increase in the concentration of hydrogen ions (a reduction in pH) and a reduction in the concentration of carbonate ions. The latter causes the ‘aragonite saturation horizon’—below which waters are undersaturated with respect to a particular calcium carbonate, aragonite—to move to shallower depths (to shoal), exposing corals to corrosive waters. Here we use a database analysis to show that the present rate of supply of acidified waters to the deep Atlantic could cause the aragonite saturation horizon to shoal by 1,000-1,700 metres in the subpolar North Atlantic within the next three decades. We find that, during 1991-2016, a decrease in the concentration of carbonate ions in the Irminger Sea caused the aragonite saturation horizon to shoal by about 10-15 metres per year, and the volume of aragonite-saturated waters to reduce concomitantly. Our determination of the transport of the excess of carbonate over aragonite saturation (xc[CO32-])—an indicator of the availability of aragonite to organisms—by the Atlantic meridional overturning circulation shows that the present-day transport of carbonate ions towards the deep ocean is about 44 per cent lower than it was in preindustrial times. We infer that a doubling of atmospheric anthropogenic CO2 levels—which could occur within three decades according to a ‘business-as-usual scenario’ for climate change—could reduce the transport of xc[CO32-] by 64-79 per cent of that in preindustrial times, which could severely endanger cold-water coral habitats. The Atlantic meridional overturning circulation would also export this acidified deep water southwards, spreading corrosive waters to the world ocean.

  20. The South American Meridional B-field Array (SAMBA) and Pc4-5 Wave Studies

    Science.gov (United States)

    Sterner, N. L.; Zesta, E.; Boudouridis, A.; Moldwin, M.; Yizengaw, E.; Chi, P. J.

    2010-12-01

    The Antarctic continent, the only landmass in the southern polar region, offers the unique opportunity for observations that geomagnetically range from polar latitudes to well into the inner magnetosphere, thus enabling conjugate observations in a wide range of geomagnetic latitudes. The SAMBA (South American Meridional B-field Array) chain is a meridional chain of 12 magnetometers, 11 of them at L=1.1 to L=2.5 along the coast of Chile and in the Antarctica peninsula, and one auroral station along the same meridian. SAMBA is conjugate to the northern hemisphere MEASURE and McMAC chains, offering unique opportunities for inter-hemispheric studies. In particular, we study asymmetries in the power of ULF waves and the role of the ionosphere in such observed asymmetries. Utilizing conjugate magnetometer stations at L=1.7 and L=2.3, we previously demonstrated that the northern hemisphere consistently shows higher ULF wave power. One possible reason for the asymmetry is solar zenith angles differences with the northern hemisphere station being closer to the ecliptic plain and having a higher power ratio. These hemispheric differences were also observed with TEC measurements indicating that the north and south conjugate ionospheres are similarly asymmetric. The initial study was done with Pc3 waves, which include the resonance frequencies for the flux tubes of our conjugate stations. We now extend the study to Pc4 and Pc5 waves that reach the lower latitudes via different mechanisms and compare these waves to the resonant Pc3 waves.

  1. Does δ18O of O2 record meridional shifts in tropical rainfall?

    Directory of Open Access Journals (Sweden)

    A. M. Seltzer

    2017-10-01

    Full Text Available Marine sediments, speleothems, paleo-lake elevations, and ice core methane and δ18O of O2 (δ18Oatm records provide ample evidence for repeated abrupt meridional shifts in tropical rainfall belts throughout the last glacial cycle. To improve understanding of the impact of abrupt events on the global terrestrial biosphere, we present composite records of δ18Oatm and inferred changes in fractionation by the global terrestrial biosphere (ΔεLAND from discrete gas measurements in the WAIS Divide (WD and Siple Dome (SD Antarctic ice cores. On the common WD timescale, it is evident that maxima in ΔεLAND are synchronous with or shortly follow small-amplitude WD CH4 peaks that occur within Heinrich stadials 1, 2, 4, and 5 – periods of low atmospheric CH4 concentrations. These local CH4 maxima have been suggested as markers of abrupt climate responses to Heinrich events. Based on our analysis of the modern seasonal cycle of gross primary productivity (GPP-weighted δ18O of terrestrial precipitation (the source water for atmospheric O2 production, we propose a simple mechanism by which ΔεLAND tracks the centroid latitude of terrestrial oxygen production. As intense rainfall and oxygen production migrate northward, ΔεLAND should decrease due to the underlying meridional gradient in rainfall δ18O. A southward shift should increase ΔεLAND. Monsoon intensity also influences δ18O of precipitation, and although we cannot determine the relative contributions of the two mechanisms, both act in the same direction. Therefore, we suggest that abrupt increases in ΔεLAND unambiguously imply a southward shift of tropical rainfall. The exact magnitude of this shift, however, remains under-constrained by ΔεLAND.

  2. Does δ18O of O2 record meridional shifts in tropical rainfall?

    Science.gov (United States)

    Seltzer, Alan M.; Buizert, Christo; Baggenstos, Daniel; Brook, Edward J.; Ahn, Jinho; Yang, Ji-Woong; Severinghaus, Jeffrey P.

    2017-10-01

    Marine sediments, speleothems, paleo-lake elevations, and ice core methane and δ18O of O2 (δ18Oatm) records provide ample evidence for repeated abrupt meridional shifts in tropical rainfall belts throughout the last glacial cycle. To improve understanding of the impact of abrupt events on the global terrestrial biosphere, we present composite records of δ18Oatm and inferred changes in fractionation by the global terrestrial biosphere (ΔɛLAND) from discrete gas measurements in the WAIS Divide (WD) and Siple Dome (SD) Antarctic ice cores. On the common WD timescale, it is evident that maxima in ΔɛLAND are synchronous with or shortly follow small-amplitude WD CH4 peaks that occur within Heinrich stadials 1, 2, 4, and 5 - periods of low atmospheric CH4 concentrations. These local CH4 maxima have been suggested as markers of abrupt climate responses to Heinrich events. Based on our analysis of the modern seasonal cycle of gross primary productivity (GPP)-weighted δ18O of terrestrial precipitation (the source water for atmospheric O2 production), we propose a simple mechanism by which ΔɛLAND tracks the centroid latitude of terrestrial oxygen production. As intense rainfall and oxygen production migrate northward, ΔɛLAND should decrease due to the underlying meridional gradient in rainfall δ18O. A southward shift should increase ΔɛLAND. Monsoon intensity also influences δ18O of precipitation, and although we cannot determine the relative contributions of the two mechanisms, both act in the same direction. Therefore, we suggest that abrupt increases in ΔɛLAND unambiguously imply a southward shift of tropical rainfall. The exact magnitude of this shift, however, remains under-constrained by ΔɛLAND.

  3. A Tall-Tower Instrument for Mean and Fluctuating Velocity, Fluctuating Temperature and Sensible Heat Flux Measurements

    DEFF Research Database (Denmark)

    Gryning, Sven-Erik; Thomson, D. W.

    1979-01-01

    For an ongoing elevated-source, urban-scale tracer experiment, an instrument system to measure the three-dimensional wind velocity and the turbulent sensible heat flux was developed. The wind velocity was measured with a combination of cup anemometer, propeller (vertical) and vane sensor. The tem......For an ongoing elevated-source, urban-scale tracer experiment, an instrument system to measure the three-dimensional wind velocity and the turbulent sensible heat flux was developed. The wind velocity was measured with a combination of cup anemometer, propeller (vertical) and vane sensor...

  4. Asymmetric response of the Atlantic Meridional Ocean Circulation to freshwater anomalies in a strongly-eddying global ocean model

    NARCIS (Netherlands)

    Brunnabend, Sandra Esther|info:eu-repo/dai/nl/371740878; Dijkstra, Henk A.|info:eu-repo/dai/nl/073504467

    2017-01-01

    The Atlantic Meridional Overturning Circulation (AMOC) responds sensitively to density changes in regions of deepwater formation. In this paper, we investigate the nonlinear response of the AMOC to large amplitude freshwater changes around Greenland using a strongly-eddying global ocean model. Due

  5. Cloud Effects on Meridional Atmospheric Energy Budget Estimated from Clouds and the Earth's Radiant Energy System (CERES) Data

    Science.gov (United States)

    Kato, Seiji; Rose, Fred G.; Rutan, David A.; Charlock, Thomas P.

    2008-01-01

    The zonal mean atmospheric cloud radiative effect, defined as the difference of the top-of-atmosphere (TOA) and surface cloud radiative effects, is estimated from three years of Clouds and the Earth's Radiant Energy System (CERES) data. The zonal mean shortwave effect is small, though it tends to be positive (warming). This indicates that clouds increase shortwave absorption in the atmosphere, especially in midlatitudes. The zonal mean atmospheric cloud radiative effect is, however, dominated by the longwave effect. The zonal mean longwave effect is positive in the tropics and decreases with latitude to negative values (cooling) in polar regions. The meridional gradient of cloud effect between midlatitude and polar regions exists even when uncertainties in the cloud effect on the surface enthalpy flux and in the modeled irradiances are taken into account. This indicates that clouds increase the rate of generation of mean zonal available potential energy. Because the atmospheric cooling effect in polar regions is predominately caused by low level clouds, which tend to be stationary, we postulate that the meridional and vertical gradients of cloud effect increase the rate of meridional energy transport by dynamics in the atmosphere from midlatitude to polar region, especially in fall and winter. Clouds then warm the surface in polar regions except in the Arctic in summer. Clouds, therefore, contribute in increasing the rate of meridional energy transport from midlatitude to polar regions through the atmosphere.

  6. Aeroservoelasticity of wind turbines

    Energy Technology Data Exchange (ETDEWEB)

    Skovmose Kallesoee, B.

    2007-12-14

    This thesis deals with the fundamental aeroelastic interaction between structural motion, Pitch action and control for a wind turbine blade. As wind turbines become larger, the interaction between pitch action, blade motion, aerodynamic forces, and control become even more important to understand and address. The main contribution of this thesis is the development of an aeroelastic blade model which on the one hand includes the important effects of steady state blade deformation, gravity and pitch action, and on the other it is transparent, suitable for analytical analysis and parameter studies, and furthermore linear and therefore suitable for control design. The development of the primary aeroelastic blade model is divided into four steps: 1) Nonlinear partial differential equations (PDEs) of structural blade motion are derived together with equations of pitch action and rotor speed; the individual terms in these equations are discussed and given physical interpretations; 2) Steady state blade deformation and induced velocities are computed by combining the PDEs with a steady state aerodynamic model; 3) Aeroelastic modes of motion are computed by combining the linearized PDEs with a linear unsteady aerodynamic model; this model is used to analyze how blade deformation effects the modes of motion; and 4) the linear aeroelastic blade model is derived by a modal expansion of the linearized PDEs combined with a linear unsteady aerodynamic model. The aeroelastic blade model has many similarities to a 2D blade section model, and it can be used instead of this in many applications, giving a transparent connection to a real wind turbine blade. In this work the aeroelastic blade model is used to analyze interaction between pitch action, blade motion and wind speed variations. Furthermore the model is used to develop a state estimator for estimating the wind speed and wind shear, and to suggest a load reducing controller. The state estimator estimates the wind shear very

  7. The Coincidence Tracker: Electronic Equipment for a Time-of-Flight Wind-Speed Measurement System

    DEFF Research Database (Denmark)

    Fog, Christian

    1982-01-01

    The electronic part of a laser-beam measuring system for wind velocity is described. Pulses of light scattered from aerosols are treated, first in a pair of adaptive filters, then in a tracker that calculates the wind velocity on-line while applying some knowledge about the velocity to be expected...

  8. A 3D Convective Model for the Jovian Wind Bands

    Science.gov (United States)

    Mayr, H. G.; Chan, K. L.

    2004-01-01

    In an earlier paper, we proposed that Jupiter's alternating wind bands are a manifestation of the global interaction between rotation and convection in a shallow layer. The model, however, was obtained from linearization of the 2D equations of motions. At HKUST/Hong Kong, we are now trying to study this problem by rigorous numerical simulation. Using a three-dimensional spectral numerical code, we compute models for the outermost layer of Jupiter's convective envelope. Two cases have been studied. In one the atmospheric pressure varies from 1 to 23 bar, and in the other from 1 to 115 bar. The physical parameters (internal energy flux, rotation rate) are chosen to be close to those expected, but solar heating, chemistry, as well as dynamical influences from deeper layers are ignored. The models generate wind field patterns that contain alternating jet streams with resemblance to the Jovian bands. Instantaneous values of the mean zonal flow at the equator reach 80 m/sec. Yet the mean meridional flows are less than 1% of such value. The meridional temperature profile at the cloud top level also shows a double hump structure of a few degrees (as observed) in the subtropics. Though there is not complete quantitative agreement (caused perhaps by neglected effects like solar radiation), these models demonstrate, in principle, the feasibility of generating a Jovian type wind pattern through the interaction of fast rotation and convection in a thin shell.

  9. Optimization of Wind Farm Layout in Complex Terrain

    DEFF Research Database (Denmark)

    Xu, Chang; Yang, Jianchuan; Li, Chenqi

    2013-01-01

    Microscopic site selection for wind farms in complex terrain is a technological difficulty in the development of onshore wind farms. This paper presented a method for optimizing wind farm layout in complex terrain. This method employed Lissaman and Jensen wake models, took wind velocity distribut......Microscopic site selection for wind farms in complex terrain is a technological difficulty in the development of onshore wind farms. This paper presented a method for optimizing wind farm layout in complex terrain. This method employed Lissaman and Jensen wake models, took wind velocity...... are subject to boundary conditions and minimum distance conditions. The improved genetic algorithm (GA) for real number coding was used to search the optimal result. Then the optimized result was compared to the result from the experienced layout method. Results show the advantages of the present method...

  10. Wind energy

    CERN Document Server

    Woll, Kris

    2016-01-01

    Across the country, huge open spaces are covered in gently turning wind turbines. In Wind Energy, explore how these machines generate electricity, learn about the history of wind power, and discover the latest advances in the field. Easy-to-read text, vivid images, and helpful back matter give readers a clear look at this subject. Features include a table of contents, infographics, a glossary, additional resources, and an index. Aligned to Common Core Standards and correlated to state standards. Core Library is an imprint of Abdo Publishing, a division of ABDO.

  11. Modelling of environmental and climatic problems: Wind and water erosion

    International Nuclear Information System (INIS)

    Aslan, Z.

    2004-01-01

    Magnitude of wind and water erosion mainly depend on wind velocity, rainfall rate, slope and soil characteristics. The main purpose of this lecture is to define the role of small, meso and large scale phenomena (local and synoptic fluctuations) on water and wind erosion. These lecture notes present some results on wind speed simulation and seasonal fluctuations of water deficit for the selected station in different erosion risque and transition regions of Turkey. (author)

  12. Dynamic modelling and robust control of a wind energy conversion system

    NARCIS (Netherlands)

    Steinbuch, M.

    1989-01-01

    The application of wind energy conversion systems for the production of electrical energy requires a cheap and reliable operation. Especially at high wind velocities fluctuations from the wind field result in large mechanical loads of the wind turbine. Also fluctuations in the grid voltage may yield

  13. Influence of El Niño Wind Stress Anomalies on South Brazil Bight Ocean Volume Transports

    Directory of Open Access Journals (Sweden)

    Luiz Paulo de Freitas Assad

    2015-01-01

    Full Text Available The knowledge of wind stress variability could represent an important contribution to understand the variability over upper layer ocean volume transports. The South Brazilian Bight (SBB circulation had been studied by numerous researchers who predominantly attempted to estimate its meridional volume transport. The main objective and contribution of this study is to identify and quantify possible interannual variability in the ocean volume transport in the SBB induced by the sea surface wind stress field. A low resolution ocean global circulation model was implemented to investigate the volume transport variability. The results obtained indicate the occurrence of interannual variability in meridional ocean volume transports along three different zonal sections. These results also indicate the influence of a wind driven large-scale atmospheric process that alters locally the SBB and near-offshore region wind stress field and consequently causes interannual variability in the upper layer ocean volume transports. A strengthening of the southward flow in 25°S and 30°S was observed. The deep layer ocean volume transport in the three monitored sections indicates a potential dominance of other remote ocean processes. A small time lag between the integrated meridional volume transports changes in each monitored zonal section was observed.

  14. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...

  15. Intermittent structures in atmospheric wind fields

    Energy Technology Data Exchange (ETDEWEB)

    Yueksek, Oersan; Muecke, Tanja; Peinke, Joachim [Wind Center for Wind Energy Research, University of Oldenburg (Germany)

    2011-07-01

    For design processes and load calculations of wind energy convertors (WEC) realistic synthetic wind fields are needed. The widely used norm is the standard IEC 61400. The IEC standard considers different simulation methods based on Gaussian statistics. However, the analysis of the measured wind fields by means of velocity increment statistics yields that these do not obey Gaussian statistics but are quite intermittent. The intermittent nature of atmospheric wind affects the whole chain of the wind energy conversion process and is assumed to be a major effect for additional loads and fatigue. A recently proposed method based on continuous time random walks (CTRWs) adequately reproduces the intermittency of turbulent atmospheric velocity increments on small time scales and provides wind fields with the desired high order two point statistics. In this work, we analyze highly time-resolved data sets measured in an extensive grid over the whole rotor plane of a WEC. The atmospheric wind fields are characterized statistically and the dependency of the higher order two point statistics on turbulence intensity, mean wind speed and height is shown. With this knowledge we are able to generate synthetic CTRW wind fields with the correct small scale structure.

  16. The South American Meridional B-field Array (SAMBA) and opportunities for inter- hemispheric studies

    Science.gov (United States)

    Zesta, E.; Boudouridis, A.; Moldwin, M. B.; Weygand, J. M.; Chi, P. J.

    2009-05-01

    The Antarctic continent, the only landmass in the southern polar region, offers the unique opportunity for observations that geomagnetically range from polar latitudes to well into the inner magnetosphere, thus enabling conjugate observations in a wide range of geomagnetic latitudes. The SAMBA (South American Meridional B-field Array) chain is a meridional chain of 12 magnetometers, 11 of them at L=1.1 to L=2.5 along the coast of Chile and in the Antarctica peninsula, and one auroral station along the same meridian. SAMBA is ideal for low and mid-latitude studies of geophysical events and ULF waves. It is conjugate to the northern hemisphere MEASURE and McMAC chains, offering unique opportunities for inter-hemispheric studies. We use 5 of the SAMBA stations and a number of conjugate stations from the Northern hemisphere to determine the field line resonance (FLR) frequency of closely spaced flux tubes in the inner magnetosphere. Standard inversion techniques are used to derive the equatorial mass density of these flux tubes from the FLRs. From our conjugate pairs we find, surprisingly, that the derived mass density of closely spaced flux tubes, from L=1.6 to L=2.5, drops at a rate that cannot be predicted by any of the existing models or agree with past observations. We also study asymmetries in the power of Pc3 waves. We find that during northern summer solstice the waves are significantly stronger at the northern conjugate point, while during northern winter solstice the wave power is comparable over both conjugate points. Finally, using the SAMBA auroral station, WSD, along with all available southern auroral stations we calculate a southern AE index and its direct conjugate northern AE index and compare both with the standard AE index. We explore under what conditions the north-south asymmetries in the AE calculation are due to the significant gap of auroral stations in the Southern hemisphere and under what conditions the asymmetries have a geophysical source.

  17. Impact of the Indonesian Throughflow on the Atlantic Meridional Overturning Circulation

    Science.gov (United States)

    Le Bars, Dewi; Dijkstra, Henk

    2014-05-01

    Understanding the mechanisms controlling the strength and variability of the Atlantic Meridional Overturning Circulation (AMOC) is one of the main topics of climate science and in particular physical oceanography. Current simple representations of the global ocean overturning separates the surface return flow to the Atlantic basin into a cold water path through the Drake Passage and a warm water path through the Indonesian Throughflow and Agulhas leakage. The relative importance of these two paths has been investigated in non-eddying ocean models. In these models the Agulhas retroflection cannot be modelled properly, which leads to an important overestimation of the Agulhas leakage. Furthermore, it seems that the in these models the relation between the meridional density gradient and the overturning strength is greatly simplified and changes significantly when eddies are resolved (Den Toom et al. 2013). As a result, the impact of the Pacific-Indian Oceans exchange through the Indonesian Throughflow on the AMOC is still unknown. To investigate this question we run a state-of-the-art ocean model, the Parallel Ocean Program (POP), globally, at eddy resolving resolution (0.1º). Using climatological forcing from the CORE dataset we perform two simulations of 110 years, a control experiment with realistic coastlines and one in which the Indonesian Passages are closed. Results show that, for a closed Indonesian Throughflow, the Indian Ocean cools down but its salinity increases. The Agulhas leakage reduces also by 3Sv (Le Bars et al. 2013) and the net effect on the south Atlantic is a cooling down and decrease salinity. The anomalies propagate slowly northward and a significant decrease of the AMOC is found at 26ºN after 50 years. This decrease AMOC also leads to reduced northward heat flux in the Atlantic. These processes are investigated with a detailed analysis of the heat and freshwater balances in the Atlantic-Arctic region and in the region south of 34ºS where

  18. Wind, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Modulus

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind divergence data originating with wind velocity measurements from the ASCAT instrument onboard EUMETSAT's ASCAT...

  19. Wind, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Zonal

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind divergence data originating with wind velocity measurements from the ASCAT instrument onboard EUMETSAT's ASCAT...

  20. Wind, METOP ASCAT, 0.25 degrees, Global, Near Real Time, Divergence

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time wind divergence data originating with wind velocity measurements from the ASCAT instrument onboard EUMETSAT's ASCAT...

  1. World Wind

    Data.gov (United States)

    National Aeronautics and Space Administration — World Wind allows any user to zoom from satellite altitude into any place on Earth, leveraging high resolution LandSat imagery and SRTM elevation data to experience...

  2. Impact of the new equation of state of seawater (TEOS-10) on the estimates of water mass mixture and meridional transport in the Atlantic Ocean

    Science.gov (United States)

    Almeida, Lucas; de Azevedo, José Luiz Lima; Kerr, Rodrigo; Araujo, Moacyr; Mata, Mauricio M.

    2018-03-01

    The equation of state of seawater (EOS) provides a simple way to link the properties of seawater that are the most important for ocean dynamics and the ocean-atmosphere climate system. In 2010, the set of equations used to derive all thermodynamic properties of seawater were updated using a thermodynamic approach. The new approach, named TEOS-10, results in better estimates of seawater properties, such as salinity and temperature, when compared to the previous EOS version (EOS-80). Since several physical processes in the oceans are driven by these properties, improvements in the EOS performance are expected to lead to a better and more realistic representation of the ocean. This work focuses on assessing the main differences of the: (i) contribution of water masses to a total mixture, (ii) baroclinic velocity, and (iii) volume and heat transport, as calculated by the EOS-80 and by the TEOS-10, along four zonal transects at 26.5°N, 10°N, 11°S, and 34.5°S in the Atlantic Ocean. The density differences (always between TEOS-10 and EOS-80) increase with depth and hence the results indicate that the most significant difference in the water mass contributions was found for Antarctic Bottom Water. Within that layer, the differences reach up to 10% on its fraction of the mixture when calculated by the TEOS-10, although the difference in the North Atlantic Deep Water contribution was not negligible either. The estimated baroclinic velocities showed considerable differences in all studied areas, being more significant over boundary current systems. The Gulf Stream presented lower velocity, while the Brazil Current presented increasing velocity when using TEOS-10. The comparison between values computed for volume transported by the Atlantic Meridional Overturning Circulation showed a total difference of about +6%, which cannot be neglected when considering the space and time variability involved. The heat transport showed significant differences in the study areas at the

  3. Close binary evolution. II. Impact of tides, wind magnetic braking, and internal angular momentum transport

    Science.gov (United States)

    Song, H. F.; Meynet, G.; Maeder, A.; Ekström, S.; Eggenberger, P.; Georgy, C.; Qin, Y.; Fragos, T.; Soerensen, M.; Barblan, F.; Wade, G. A.

    2018-01-01

    Context. Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. Aims: We study the interactions between the process of wind magnetic braking and tides in close binary systems. Methods: We discuss the evolution of a 10 M⊙ star in a close binary system with a 7 M⊙ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M⊙ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. Results: We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. This "equilibrium angular velocity" is always inferior to the angular orbital velocity. In a given close binary system at this equilibrium stage, the difference between the spin and the orbital angular velocities becomes larger when the mass losses and/or the surface magnetic field increase. The

  4. PREDICTION OF POWER GENERATION OF SMALL SCALE VERTICAL AXIS WIND TURBINE USING FUZZY LOGIC

    Directory of Open Access Journals (Sweden)

    Altab Hossain

    2009-01-01

    Full Text Available Renewable energy from the wind turbine has been focused for the alternative source of power generation due to the following advances of the of the wind turbine. Firstly, the wind turbine is highly efficient and eco-friendly. Secondly, the turbine has the ability to response for the changeable power generation based on the wind velocity and structural framework. However, the competitive efficiency of the wind turbine is necessary to successfully alternate the conventional power sources. The most relevant factor which affects the overall efficiency of the wind turbine is the wind velocity and the relative turbine dimensions. Artificial intelligence systems are widely used technology that can learn from examples and are able to deal with non-linear problems. Compared with traditional approach, fuzzy logic approach is more efficient for the representation, manipulation and utilization. Therefore, the primary purpose of this work was to investigate the relationship between wind turbine power generation and wind velocity, and to illustrate how fuzzy expert system might play an important role in prediction of wind turbine power generation. The main purpose of the measurement over the small scaled prototype vertical axis wind turbine for the wind velocity is to predict the performance of full scaled H-type vertical axis wind turbine. Prediction of power generation at the different wind velocities has been tested at the Thermal Laboratory of Faculty of Engineering, Universiti Industri Selangor (UNISEL and results concerning the daily prediction have been obtained.

  5. 78 FR 29364 - Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4...

    Science.gov (United States)

    2013-05-20

    ...-005, QF07-257-004] Exelon Corporation, Exelon Wind 1, LLC, Exelon Wind 2, LLC, Exelon Wind 3, LLC, Exelon Wind 4, LLC, Exelon Wind 5, LLC, Exelon Wind 6, LLC, Exelon Wind 7, LLC, Exelon Wind 8, LLC, Exelon Wind 9, LLC, Exelon Wind 10, LLC, Exelon Wind 11, LLC, High Plains Wind Power, LLC v. Xcel Energy...

  6. Gas Transfer Velocity in the Presence of Wave Breaking

    Science.gov (United States)

    Li, S.

    2016-02-01

    Wave breaking is known to intensify the gas exchange across the air-sea interface through air entrainment and enhancement of the near-surface turbulence. We proposed a composite model for the gas transfer velocity by examining the near-surface turbulence induced by wave breaking, which was determined based on the combination of the vertical distribution of the turbulence in the wave-affected layer and the breaking wave energy dissipation rate in the wave-breaking layer. The gas transfer velocity was calculated as a function of the air frictional velocity, wave age, and whitecap coverage. The model was validated for both the wind and wave-age dependence against field and laboratory measurements. The results supported the hypothesis that the large uncertainties in the traditional wind speed-based gas transfer velocities at moderate to high wind speeds can be ascribed to the neglect of the wind-wave effect, which is mainly attributed to the whitecap coverage as a function of the wind-wave Reynolds number.

  7. Plausible Effect of Weather on Atlantic Meridional Overturning Circulation with a Coupled General Circulation Model

    Science.gov (United States)

    Liu, Zedong; Wan, Xiuquan

    2018-04-01

    The Atlantic meridional overturning circulation (AMOC) is a vital component of the global ocean circulation and the heat engine of the climate system. Through the use of a coupled general circulation model, this study examines the role of synoptic systems on the AMOC and presents evidence that internally generated high-frequency, synoptic-scale weather variability in the atmosphere could play a significant role in maintaining the overall strength and variability of the AMOC, thereby affecting climate variability and change. Results of a novel coupling technique show that the strength and variability of the AMOC are greatly reduced once the synoptic weather variability is suppressed in the coupled model. The strength and variability of the AMOC are closely linked to deep convection events at high latitudes, which could be strongly affected by the weather variability. Our results imply that synoptic weather systems are important in driving the AMOC and its variability. Thus, interactions between atmospheric weather variability and AMOC may be an important feedback mechanism of the global climate system and need to be taken into consideration in future climate change studies.

  8. Asymmetric Relationship between the Meridional Displacement of the Asian Westerly Jet and the Silk Road Pattern

    Science.gov (United States)

    Hong, Xiaowei; Lu, Riyu; Li, Shuanglin

    2018-04-01

    In previous work, a significant relationship was identified between the meridional displacement of the Asian westerly jet (JMD) and the Silk Road Pattern (SRP) in summer. The present study reveals that this relationship is robust in northward JMD years but absent in southward JMD years. In other words, the amplitude of the SRP increases with northward displacement of the jet but shows little change with southward displacement. Further analysis indicates that, in northward JMD years, the Rossby wave source (RWS) anomalies, which are primarily contributed by the planetary vortex stretching, are significantly stronger around the entrance of the Asian jet, i.e., the Mediterranean Sea-Caspian Sea area, with the spatial distribution being consistent with that related to the SRP. By contrast, in southward JMD years, the RWS anomalies are much weaker. Therefore, this study suggests that the RWS plays a crucial role in inducing the asymmetry of the JMD-SRP relationship. The results imply that climate anomalies may be stronger in strongly northward-displaced JMD years due to the concurrence of the JMD and SRP, and thus more attention should be paid to these years.

  9. Observed decline of the Atlantic Meridional Overturning circulation 2004 to 2012

    Science.gov (United States)

    Cunningham, Stuart; Smeed, David; Johns, William; Meinen, Chris; Rayner, Darren; Moat, Ben; Duchez, Aurelie; Bryden, Harry; Baringer Molly, O.; McCarthy, Gerard

    2014-05-01

    The Atlantic Meridional Overturning Circulation (AMOC) has been observed continuously at 26° N since April 2004. The AMOC and its component parts are monitored by combining a transatlantic array of moored instruments with submarine-cable based measurements of the Gulf Stream and satellite derived Ekman transport. The time series has recently been extended to October 2012 and the results show a downward trend since 2004. From April~2008 to March 2012 the AMOC was an average of 2.7 Sv weaker than in the first four years of observation (95% confidence that the reduction is 0.3 Sv or more). Ekman transport reduced by about 0.2 Sv and the Gulf Stream by 0.5 Sv but most of the change (2.0 Sv) is due to the mid-ocean geostrophic flow. The change of the mid-ocean geostrophic flow represents a strengthening of the subtropical gyre above the thermocline. The increased southward flow of warm waters is balanced by a decrease in the southward flow of Lower North Atlantic Deep Water below 3000 m. The transport of Lower North Atlantic Deep Water slowed by 7% per year (95% confidence that the rate of slowing is greater than 2.5% per year).

  10. Atmospheric deposition of soluble trace elements along the Atlantic Meridional Transect (AMT)

    Science.gov (United States)

    Baker, Alex R.; Jickells, Tim D.

    2017-11-01

    We briefly review the role of atmospheric deposition measurements within the Atlantic Meridional Transect (AMT) programme and then go on to present new data on the soluble concentrations of a range of trace metals (Fe, Al, Mn, Ti, Zn, V, Ni and Cu) and major ions in aerosols collected along the AMT transect. The results allow us to identify emission sources of the trace metals particularly in terms of the relative importance of anthropogenic versus crustal sources. We identify strong gradients in concentrations and deposition for both crustal and anthropogenically sourced metals with much higher inputs to the North Atlantic compared to the South Atlantic, reflecting stronger land based emission sources in the Northern Hemisphere. We suggest anthropogenic sources of Ni and V may include an important component from shipping. We consider the extent to which these gradients are reflected in surface water concentrations of these metals based on the GEOTRACES water column trace metal data. We find there is a clear difference in the concentrations of surface water dissolved Al and Fe between the north and south Atlantic gyres reflecting atmospheric inputs. However for Mn, V or Ni, higher inputs to the North Atlantic compared to the South Atlantic are not clearly reflected in their water column concentrations.

  11. Interdecadal variability of the meridional overturning circulation as an ocean internal mode

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Xiuhua [Universitaet Hamburg, Meteorologisches Institut, Hamburg (Germany); Jungclaus, Johann [Max-Planck-Institut fuer Meteorologie, Hamburg (Germany)

    2008-11-15

    The meridional overturning circulation (MOC) in the coupled ECHAM5/MPIOM exhibits variability at periods of near 30 years and near 60 years. The 30-year variability, referred to as interdecadal variability (IDV), exist in an ocean model driven by climatological atmospheric forcing, suggesting that it is maintained by ocean dynamics; the 60-year variability, the multidecadal variability (MDV), is only observed in the fully coupled model and therefore is interpreted as an atmosphere-ocean coupled mode. The coexistence of the 30-year IDV and the 60-year MDV provides a possible explanation for the widespread time scales observed in climate variables. Further analyses of the climatologically forced ocean model shows that, the IDV is related to the interplay between the horizontal temperature-dominated density gradients and the ocean circulation: temperature anomalies move along the cyclonic subpolar gyre leading to fluctuations in horizontal density gradients and the subsequent weakening and strengthening of the MOC. This result is consistent with that from less complex models, indicating the robustness of the IDV. We further show that, along the North Atlantic Current path, the sea surface temperature anomalies are determined by the slow LSW advection at the intermediate depth. (orig.)

  12. Interdecadal North-Atlantic meridional overturning circulation variability in EC-EARTH

    International Nuclear Information System (INIS)

    Wouters, Bert; Drijfhout, Sybren; Hazeleger, Wilco

    2012-01-01

    The Atlantic meridional overturning circulation (AMOC) in a 600 years pre-industrial run of the newly developed EC-EARTH model features marked interdecadal variability with a dominant time-scale of 50-60 years. An oscillation of approximately 2 Sverdrup (1 Sv = 10 6 m 3 s -1 ) is identified, which manifests itself as a monopole causing the overturning to simultaneously strengthen (/weaken) and deepen (/shallow) as a whole. Eight years before the AMOC peaks, density in the Labrador-Irminger Sea region reaches a maximum, triggering deep water formation. This density change is caused by a counterclockwise advection of temperature and salinity anomalies at lower latitudes, which we relate to the north-south excursions of the subpolar-subtropical gyre boundary and variations in strength and position of the subpolar gyre and the North Atlantic Current. The AMOC fluctuations are not directly forced by the atmosphere, but occur in a delayed response of the ocean to forcing by the North Atlantic Oscillation, which initiates ''intergyre''-gyre fluctuations. Associated with the AMOC is a 60-year sea surface temperature variability in the Atlantic, with a pattern and timescale showing similarities with the real-world Atlantic Multidecadal Variability. This good agreement with observations lends a certain degree of credibility that the mechanism that is described in this article could be seen as representative of the real climate system. (orig.)

  13. Interdecadal North-Atlantic meridional overturning circulation variability in EC-EARTH

    Energy Technology Data Exchange (ETDEWEB)

    Wouters, Bert; Drijfhout, Sybren; Hazeleger, Wilco

    2012-12-15

    The Atlantic meridional overturning circulation (AMOC) in a 600 years pre-industrial run of the newly developed EC-EARTH model features marked interdecadal variability with a dominant time-scale of 50-60 years. An oscillation of approximately 2 Sverdrup (1 Sv = 10{sup 6} m{sup 3} s{sup -1}) is identified, which manifests itself as a monopole causing the overturning to simultaneously strengthen (/weaken) and deepen (/shallow) as a whole. Eight years before the AMOC peaks, density in the Labrador-Irminger Sea region reaches a maximum, triggering deep water formation. This density change is caused by a counterclockwise advection of temperature and salinity anomalies at lower latitudes, which we relate to the north-south excursions of the subpolar-subtropical gyre boundary and variations in strength and position of the subpolar gyre and the North Atlantic Current. The AMOC fluctuations are not directly forced by the atmosphere, but occur in a delayed response of the ocean to forcing by the North Atlantic Oscillation, which initiates ''intergyre''-gyre fluctuations. Associated with the AMOC is a 60-year sea surface temperature variability in the Atlantic, with a pattern and timescale showing similarities with the real-world Atlantic Multidecadal Variability. This good agreement with observations lends a certain degree of credibility that the mechanism that is described in this article could be seen as representative of the real climate system. (orig.)

  14. A coupled model study on the Atlantic Meridional Overturning Circulation under extreme atmospheric CO2 conditions

    Directory of Open Access Journals (Sweden)

    Rita Lecci

    2016-05-01

    Full Text Available This study investigates the climate sensitivity to a strong CO2 atmospheric forcing focusing on the North Atlantic Ocean (NA. The analysis is based on a set of 600 years long experiments performed with a state-of-the-art coupled general circulation model (CGCM with the 1990 reference value of atmospheric CO2 multiplied by 4, 8 and 16. Extreme increases in atmospheric CO2 concentration have been applied to force the climate system towards stable states with different thermo-dynamical properties and analyze how the different resulting oceanic stratification and diffusion affect the Atlantic Meridional Overturning Circulation (AMOC. The AMOC weakens in response to the induced warming with distinctive features in the extreme case: a southward shift of convective sites and the formation of a density front at mid-latitudes. The analysis of the density fluxes reveals that NA loses density at high latitudes and gains it southward of 40°N mainly due to the haline contribution. Our results indicate that the most important processes that control the AMOC are active in the high latitudes and are related to the stability of the water column. The increased ocean stratification stabilizes the ocean interior leading to a decreased vertical diffusivity, a reduction in the formation of deep water and a weaker circulation. In particular, the deep convection collapses mainly in the Labrador Sea as a consequence of the water column stratification under high latitudes freshening.

  15. Reduced interdecadal variability of Atlantic Meridional Overturning Circulation under global warming

    Science.gov (United States)

    Cheng, Jun; Liu, Zhengyu; Zhang, Shaoqing; Liu, Wei; Dong, Lina; Liu, Peng; Li, Hongli

    2016-01-01

    Interdecadal variability of the Atlantic Meridional Overturning Circulation (AMOC-IV) plays an important role in climate variation and has significant societal impacts. Past climate reconstruction indicates that AMOC-IV has likely undergone significant changes. Despite some previous studies, responses of AMOC-IV to global warming remain unclear, in particular regarding its amplitude and time scale. In this study, we analyze the responses of AMOC-IV under various scenarios of future global warming in multiple models and find that AMOC-IV becomes weaker and shorter with enhanced global warming. From the present climate condition to the strongest future warming scenario, on average, the major period of AMOC-IV is shortened from ∼50 y to ∼20 y, and the amplitude is reduced by ∼60%. These reductions in period and amplitude of AMOC-IV are suggested to be associated with increased oceanic stratification under global warming and, in turn, the speedup of oceanic baroclinic Rossby waves. PMID:26951654

  16. On the constancy along cylinders of the angular velocity in the solar convection zone

    International Nuclear Information System (INIS)

    Durney, B.R.

    1976-01-01

    If, in the absence of rotation, the Sun's convection zone is adiabatic and if in the radial and latitudinal equations of motion the main balance of forces is between pressure gradients, Coriolis forces, and buoyancy forces (which is a good approximation if differential rotation is important over the entire convection zone and the large-scale velocities are not too large), then the perturbations in the convective flux and the pole-equator differences in flux (ΔF) are very large in the lower half of the convection zone, unless the angular velocity is constant along cylinders. The meridional velocities associated with this rotation law are not small, however, and could generate a significant ΔF. In this analysis compressibility was taken into account, but the latitudinal and radial dependence of the stabilizing effect of rotation on turbulent convection was neglected

  17. WIND TURBINE OPERATION PARAMETER CHARACTERISTICS AT A GIVEN WIND SPEED

    Directory of Open Access Journals (Sweden)

    Zdzisław Kamiński

    2014-06-01

    Full Text Available This paper discusses the results of the CFD simulation of the flow around Vertical Axis Wind Turbine rotor. The examined rotor was designed following patent application no. 402214. The turbine operation is characterised by parameters, such as opening angle of blades, power, torque, rotational velocity at a given wind velocity. Those parameters have an impact on the performance of entire assembly. The distribution of forces acting on the working surfaces in the turbine can change, depending on the angle of rotor rotation. Moreover, the resultant force derived from the force acting on the oncoming and leaving blades should be as high as possible. Accordingly, those parameters were individually simulated over time for each blade in three complete rotations. The attempts to improve the performance of the entire system resulted in a new research trend to improve the performance of working turbine rotor blades.

  18. Synthetic atmospheric turbulence and wind shear in large eddy simulations of wind turbine wakes

    DEFF Research Database (Denmark)

    Keck, Rolf-Erik; Mikkelsen, Robert Flemming; Troldborg, Niels

    2014-01-01

    of the synthetic methods is found to be adequate to model atmospheric turbulence, and the wake flow results of the model are in good agreement with field data. An investigation is also carried out to estimate the wake transport velocity, used to model wake meandering in lower-order models. The conclusion......A method of generating a synthetic ambient wind field in neutral atmosphere is described and verified for modelling the effect of wind shear and turbulence on a wind turbine wake using the flow solver EllipSys3D. The method uses distributed volume forces to represent turbulent fluctuations...... is that the appropriate transport velocity of the wake lies somewhere between the centre velocity of the wake deficit and the free stream velocity. Copyright © 2013 John Wiley & Sons, Ltd....

  19. The critical ionization velocity

    International Nuclear Information System (INIS)

    Raadu, M.A.

    1980-06-01

    The critical ionization velocity effect was first proposed in the context of space plasmas. This effect occurs for a neutral gas moving through a magnetized plasma and leads to rapid ionization and braking of the relative motion when a marginal velocity, 'the critical velocity', is exceeded. Laboratory experiments have clearly established the significance of the critical velocity and have provided evidence for an underlying mechanism which relies on the combined action of electron impact ionization and a collective plasma interaction heating electrons. There is experimental support for such a mechanism based on the heating of electrons by the modified two-stream instability as part of a feedback process. Several applications to space plasmas have been proposed and the possibility of space experiments has been discussed. (author)

  20. Antarctic Ice Velocity Data

    Data.gov (United States)

    National Aeronautics and Space Administration — This compilation of recent ice velocity data of the Antarctic ice sheet is intended for use by the polar scientific community. The data are presented in tabular form...

  1. High Velocity Gas Gun

    Science.gov (United States)

    1988-01-01

    A video tape related to orbital debris research is presented. The video tape covers the process of loading a High Velocity Gas Gun and firing it into a mounted metal plate. The process is then repeated in slow motion.

  2. Integrated spatial assessment of wind erosion risk in Hungary

    Science.gov (United States)

    Pásztor, László; Négyesi, Gábor; Laborczi, Annamária; Kovács, Tamás; László, Elemér; Bihari, Zita

    2016-11-01

    Wind erosion susceptibility of Hungarian soils was mapped on the national level integrating three factors of the complex phenomenon of deflation (physical soil features, wind characteristics, and land use and land cover). Results of wind tunnel experiments on erodibility of representative soil samples were used for the parametrization of a countrywide map of soil texture compiled for the upper 5 cm layer of soil, which resulted in a map representing threshold wind velocity exceedance. Average wind velocity was spatially estimated with 0.5' resolution using the Meteorological Interpolation based on Surface Homogenised Data Basis (MISH) method elaborated for the spatial interpolation of surface meteorological elements. The probability of threshold wind velocity exceedance was determined based on values predicted by the soil texture map at the grid locations. Ratio values were further interpolated to a finer 1 ha resolution using sand and silt content of the uppermost (0-5 cm) layer of soil as spatial co-variables. Land cover was also taken into account, excluding areas that are not relevant to wind erosion (forests, water bodies, settlements, etc.), to spatially assess the risk of wind erosion. According to the resulting map of wind erosion susceptibility, about 10 % of the total area of Hungary can be identified as susceptible to wind erosion. The map gives more detailed insight into the spatial distribution of wind-affected areas in Hungary compared to previous studies.

  3. Integrated spatial assessment of wind erosion risk in Hungary

    Directory of Open Access Journals (Sweden)

    L. Pásztor

    2016-11-01

    Full Text Available Wind erosion susceptibility of Hungarian soils was mapped on the national level integrating three factors of the complex phenomenon of deflation (physical soil features, wind characteristics, and land use and land cover. Results of wind tunnel experiments on erodibility of representative soil samples were used for the parametrization of a countrywide map of soil texture compiled for the upper 5 cm layer of soil, which resulted in a map representing threshold wind velocity exceedance. Average wind velocity was spatially estimated with 0.5′ resolution using the Meteorological Interpolation based on Surface Homogenised Data Basis (MISH method elaborated for the spatial interpolation of surface meteorological elements. The probability of threshold wind velocity exceedance was determined based on values predicted by the soil texture map at the grid locations. Ratio values were further interpolated to a finer 1 ha resolution using sand and silt content of the uppermost (0–5 cm layer of soil as spatial co-variables. Land cover was also taken into account, excluding areas that are not relevant to wind erosion (forests, water bodies, settlements, etc., to spatially assess the risk of wind erosion. According to the resulting map of wind erosion susceptibility, about 10 % of the total area of Hungary can be identified as susceptible to wind erosion. The map gives more detailed insight into the spatial distribution of wind-affected areas in Hungary compared to previous studies.

  4. WIND TURBINES FOR WIND POWER INSTALLATIONS

    Directory of Open Access Journals (Sweden)

    Barladean A.S.

    2008-04-01

    Full Text Available The problem of wind turbine choice for wind power stations is examined in this paper. It is shown by comparison of parameters and characteristics of wind turbines, that for existing modes and speeds of wind in territory of Republic of Moldova it is necessary to use multi-blade small speed rotation wind turbines of fan class.

  5. Integrated roof wind energy system

    Directory of Open Access Journals (Sweden)

    Moonen S.P.G.

    2012-10-01

    Full Text Available Wind is an attractive renewable source of energy. Recent innovations in research and design have reduced to a few alternatives with limited impact on residential construction. Cost effective solutions have been found at larger scale, but storage and delivery of energy to the actual location it is used, remain a critical issue. The Integrated Roof Wind Energy System is designed to overcome the current issues of urban and larger scale renewable energy system. The system is built up by an axial array of skewed shaped funnels that make use of the Venturi Effect to accelerate the wind flow. This inventive use of shape and geometry leads to a converging air capturing inlet to create high wind mass flow and velocity toward a vertical-axis wind turbine in the top of the roof for generation of a relatively high amount of energy. The methods used in this overview of studies include an array of tools from analytical modelling, PIV wind tunnel testing, and CFD simulation studies. The results define the main design parameters for an efficient system, and show the potential for the generation of high amounts of renewable energy with a novel and effective system suited for the built environment.

  6. Determination of wind erosion next to shelterbelts

    Directory of Open Access Journals (Sweden)

    Jana Dufková

    2007-01-01

    Full Text Available The influence of shelterbelts on the erodibility of soil by wind was studied at three chosen shelterbelts of Southern Moravia, Czech Republic – near the shelterbelts in the cadastral areas of Dolní Dunajovice, Micmanice and Suchá Loz. Ambulatory measurements of wind velocity as so as soil sampling for soil humidity analyses, non-erodible and clay particles analyses were done during the year of 2006. Subsequently, real erodibility of soil by wind was determined at these three areas. Results of the measurements and calculations verify positive effect of shelterbelts consisted in wind velocity decreasing (at about 78% in average, soil humidity increasing (at about 102% in average and soil resistance increasing (at about 70% in average at the leeward side of the shelterbelts.

  7. The sound of high winds. The effect of atmospheric stability on wind turbine sound and microphone noise

    International Nuclear Information System (INIS)

    Van den Berg, G.P.

    2006-01-01

    In this thesis issues are raised concerning wind turbine noise and its relationship to altitude dependent wind velocity. The following issues are investigated: what is the influence of atmospheric stability on the speed and sound power of a wind turbine?; what is the influence of atmospheric stability on the character of wind turbine sound?; how widespread is the impact of atmospheric stability on wind turbine performance: is it relevant for new wind turbine projects; how can noise prediction take this stability into account?; what can be done to deal with the resultant higher impact of wind turbine sound? Apart from these directly wind turbine related issues, a final aim was to address a measurement problem: how does wind on a microphone affect the measurement of the ambient sound level?

  8. Wind and IMP 8 Solar Wind, Magnetosheath and Shock Data

    Science.gov (United States)

    2004-01-01

    The purpose of this project was to provide the community access to magnetosheath data near Earth. We provided 27 years of IMP 8 magnetosheath proton velocities, densities, and temperatures with our best (usually 1-min.) time resolution. IMP 8 crosses the magnetosheath twice each 125 day orbit, and we provided magnetosheath data for the roughly 27 years of data for which magnetometer data are also available (which are needed to reliably pick boundaries). We provided this 27 years of IMP 8 magnetosheath data to the NSSDC; this data is now integrated with the IMP 8 solar wind data with flags indicating whether each data point is in the solar wind, magnetosheath, or at the boundary between the two regions. The plasma speed, density, and temperature are provided for each magnetosheath point. These data are also available on the MIT web site ftp://space .mit.edu/pub/plasma/imp/www/imp.html. We provide ASCII time-ordered rows of data giving the observation time, the spacecraft position in GSE, the velocity is GSE, the density and temperature for protons. We also have analyzed and archived on our web site the Wind magnetosheath plasma parameters. These consist of ascii files of the proton and alpha densities, speeds, and thermal speeds. These data are available at ftp://space.mit.edu/pub/plasma/wind/sheath These are the two products promised in the work statement and they have been completed in full.

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

    Science.gov (United States)

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

    2009-09-01

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

  10. Offshore winds using remote sensing techniques

    International Nuclear Information System (INIS)

    Pena, Alfredo; Hasager, Charlotte Bay; Gryning, Sven-Erik; Courtney, Michael; Antoniou, Ioannis; Mikkelsen, Torben; Soerensen, Paul

    2007-01-01

    Ground-based remote sensing instruments can observe winds at different levels in the atmosphere where the wind characteristics change with height: the range of heights where modern turbine rotors are operating. A six-month wind assessment campaign has been made with a LiDAR (Light Detection And Ranging) and a SoDAR (Sound Detection and Ranging) on the transformer/platform of the world's largest offshore wind farm located at the West coast of Denmark to evaluate their ability to observe offshore winds. The high homogeneity and low turbulence levels registered allow the comparison of LiDAR and SoDAR with measurements from cups on masts surrounding the wind farm showing good agreement for both the mean wind speed and the longitudinal component of turbulence. An extension of mean wind speed profiles from cup measurements on masts with LiDAR observations results in a good match for the free sectors at different wind speeds. The log-linear profile is fitted to the extended profiles (averaged over all stabilities and roughness lengths) and the deviations are small. Extended profiles of turbulence intensity are also shown for different wind speeds up to 161 m. Friction velocities and roughness lengths calculated from the fitted log-linear profile are compared with the Charnock model which seems to overestimate the sea roughness for the free sectors

  11. A commentary on the Atlantic meridional overturning circulation stability in climate models

    Science.gov (United States)

    Gent, Peter R.

    2018-02-01

    The stability of the Atlantic meridional overturning circulation (AMOC) in ocean models depends quite strongly on the model formulation, especially the vertical mixing, and whether it is coupled to an atmosphere model. A hysteresis loop in AMOC strength with respect to freshwater forcing has been found in several intermediate complexity climate models and in one fully coupled climate model that has very coarse resolution. Over 40% of modern climate models are in a bistable AMOC state according to the very frequently used simple stability criterion which is based solely on the sign of the AMOC freshwater transport across 33° S. In a recent freshwater hosing experiment in a climate model with an eddy-permitting ocean component, the change in the gyre freshwater transport across 33° S is larger than the AMOC freshwater transport change. This casts very strong doubt on the usefulness of this simple AMOC stability criterion. If a climate model uses large surface flux adjustments, then these adjustments can interfere with the atmosphere-ocean feedbacks, and strongly change the AMOC stability properties. AMOC can be shut off for many hundreds of years in modern fully coupled climate models if the hosing or carbon dioxide forcing is strong enough. However, in one climate model the AMOC recovers after between 1000 and 1400 years. Recent 1% increasing carbon dioxide runs and RCP8.5 future scenario runs have shown that the AMOC reduction is smaller using an eddy-resolving ocean component than in the comparable standard 1° ocean climate models.

  12. The role of Meridional Overturning Circulation (MOC) on Ancient Climates and Implications for Anthropogenic Climate Change

    Science.gov (United States)

    Cumming, M.

    2017-12-01

    Our increasingly robust history of ancient climates indicates that high latitude glaciation is the ultimate product of an episodic cooling trend that began about 100-million years ago rather than a result of a yet-to-be identified modal change. Antarctic geography (continent surrounded by ocean) allowed ice to develop prior to significant glaciation in the Northern Hemisphere (ocean surrounded by land), but global ice volume generally increased as Earth cooled. The question of what caused the Ice Ages should be reframed as to "What caused the Cenozoic Cooling?" Records tell us that changes in temperature and CO2 levels rise and fall together, however it is not clear when CO2 acts as a driver versus when it is primarily an indicator of temperature change. The episodic nature of the cooling trend suggests other more dynamic phenomena are involved. It is proposed that oceanic meridional overturning circulation (MOC) plays a significant role in regulating Earth's surface temperature. Robust MOC has a cooling effect which results from its sequestration of cold waters (together with their increased heat-absorbing potential) below the surface. Unable to better absorb equatorial insolation for great lengths of time, oceanic deep waters are not able to fully compensate for the heat lost by warm-water transport to Polar Regions. A lag-time between cooling and subsequent warming yields lower operating temperatures commensurate with the strength of global MOC. The long-term decline in global temperatures is largely explained by the tectonic reshaping of ocean basins and the connections between them such that MOC has generally, but not uniformly, increased. Geophysically Influenced MOC (GIMOC) has caused a significant proportion of the lowering of global temperatures in the Cenozoic Era. Short-term disruptions in MOC (and subsequent impacts on global temperatures) were likely involved in Late Pleistocene glacial termination events and may already be compounding present

  13. The Atlantic Meridional Overturning Circulation over time: a Nd isotope perspective

    Science.gov (United States)

    Goldstein, S. L.; Pena, L. D.; Yehudai, M.; Seguí, M. J.; Kim, J.; Knudson, K. P.; Basak, C.

    2017-12-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a major means for distributing heat between the tropics and the high latitudes, and thus its temporal variability has major impacts on ice age cycles. We present a summary of work in-progress to generate north-south profiles of the AMOC from the North Atlantic to the Southern Ocean, at various time slices over the past 2 Ma, based on Nd isotopes in Fe-Mn oxide encrusted foraminifera and fish debris. Our sites show a consistent north-south gradient in the North Atlantic source water (NSW) signal strength throughout, providing strong evidence that the data represent the fluctuations of the AMOC. The North Atlantic data show strong evidence that the eNd of the NSW end-member remained similar to today through this time interval (Kim et al. this meeting). We have identified 5 modes of the AMOC circulation. The most common ones are the (1) "interglacial norm" where the NSW signal remains strong into the South Atlantic similar to the present-day, and the (2) "glacial norm" where moderate southern source water (SSW) signals extend into the deep North Atlantic. Less common are the (3) "weak AMOC" mode, typical of Heinrich events, the Mid-Pleistocene Transition (MPT), and MIS 10,16, where even the deep North Atlantic shows a strong SSW signal, and its counterpart the (4) "ultra-strong AMOC", in MIS 9, 11, 19, 21 and 25, when the NSW signal is unusually strong south of the equator. Finally, during the (5) "pre-MPT" mode, in MIS 26 and 27, uniquely low Nd isotope ratios in the North Atlantic signals major input of Nd from the Canadian Shield directly preceding the MPT AMOC crisis (Pena and Goldstein, Science 2014), reflecting events there that likely triggered it. Overall we expect that the AMOC profiles will be useful as a means to directly relate climate to concurrent ocean circulation through time.

  14. Variations of the Atlantic meridional overturning circulation in control and transient simulations of the last millennium

    Directory of Open Access Journals (Sweden)

    D. Hofer

    2011-02-01

    Full Text Available The variability of the Atlantic meridional overturing circulation (AMOC strength is investigated in control experiments and in transient simulations of up to the last millennium using the low-resolution Community Climate System Model version 3. In the transient simulations the AMOC exhibits enhanced low-frequency variability that is mainly caused by infrequent transitions between two semi-stable circulation states which amount to a 10 percent change of the maximum overturning. One transition is also found in a control experiment, but the time-varying external forcing significantly increases the probability of the occurrence of such events though not having a direct, linear impact on the AMOC. The transition from a high to a low AMOC state starts with a reduction of the convection in the Labrador and Irminger Seas and goes along with a changed barotropic circulation of both gyres in the North Atlantic and a gradual strengthening of the convection in the Greenland-Iceland-Norwegian (GIN Seas. In contrast, the transition from a weak to a strong overturning is induced by decreased mixing in the GIN Seas. As a consequence of the transition, regional sea surface temperature (SST anomalies are found in the midlatitude North Atlantic and in the convection regions with an amplitude of up to 3 K. The atmospheric response to the SST forcing associated with the transition indicates a significant impact on the Scandinavian surface air temperature (SAT in the order of 1 K. Thus, the changes of the ocean circulation make a major contribution to the Scandinavian SAT variability in the last millennium.

  15. Estudios sobre la vegetación del estado de Paraná (Brasil meridional

    Directory of Open Access Journals (Sweden)

    de Bolòs, Oriol

    1991-12-01

    Full Text Available Contribution to knowledge about the vegetation of the state of Paraná in southern Brazil (Serra do Mar, Planaltos, Iguaçu Valley. Numerous plant associations are described and grouped together in the following classes: Pistio-Eichhornietea (communities of floating cormophytes Xyrido-Typhetea (helophytic herbaceous vegetation Polypodio-Tillandsietea (epiphytic and comophytic vegetation Ruderali-Manihotetea (ruderal and segetal vegetation Andropogono-Baccharidetea (savanoid vegetation Rhizophoretea (mangroves Lantano-Chusqueetea (woody marginal communities of the forest Cedrelo-Ocoteetea (rain and mesophilous forest. Special attention is paid to the study of the physiognomy, structure and dynamism of the vegetation and its biogeographical significance.

    Aportación al conocimiento de la vegetación del estado de Paraná en el Brasil meridional (Serra do Mar, Planaltos, valle del Iguaçu. Se describen numerosas asociaciones vegetales agrupadas en las clases siguientes: Pistio-Eichhornietea (comunidades de cormófitos flotantes. Xyrido-Typhetea (vegetación herbácea helofítica. Polypodio-Tillandsietea (vegetación epifítica y comofítica. Ruderali-Manihotetea (vegetación ruderal, viaria y arvense. Andropogono-Baccharidetea (vegetación sabanoide. Rhizophoretea (manglar. Lantano-Chusqueetea (manto marginal leñoso de la selva. Cedrelo-Ocoteetea (selva pluvial y mesófila. Se dedica atención especial al estudio de la fisionomía, estructura y dinamismo de la vegetación y a su significación biogeográfica.

  16. Effects of Solar Geoengineering on Meridional Energy Transport and the ITCZ

    Science.gov (United States)

    Russotto, R. D.; Ackerman, T. P.; Frierson, D. M.

    2016-12-01

    The polar amplification of warming and the ability of the intertropical convergence zone (ITCZ) to shift to the north or south are two very important problems in climate science. Examining these behaviors in global climate models (GCMs) running solar geoengineering experiments is helpful not only for predicting the effects of solar geoengineering, but also for understanding how these processes work under increased CO2. Both polar amplification and ITCZ shifts are closely related to the meridional transport of moist static energy (MSE) by the atmosphere. In this study we examine changes in MSE transport in 10 fully coupled GCMs in Experiment G1 of the Geoengineering Model Intercomparison Project, in which the solar constant is reduced to compensate for abruptly quadrupled CO2 concentrations. In this experiment, poleward MSE transport decreases relative to preindustrial conditions in all models, in contrast to the CMIP5 abrupt4xCO2 experiment, in which poleward MSE transport increases. The increase in poleward MSE transport under increased CO2 is due to latent heat transport, as specific humidity increases faster in the tropics than at the poles; this mechanism is not present under G1 conditions, so the reduction in dry static energy transport due to a weakened equator-to-pole temperature gradient leads to weaker energy transport overall. Changes in cross-equatorial MSE transport in G1, meanwhile, are anticorrelated with shifts in the ITCZ. The northward ITCZ shift in G1 is 0.14 degrees in the multi-model mean and ranges from -0.33 to 0.89 degrees between the models. We examine the specific forcing and feedback terms responsible for changes in MSE transport in G1 by running experiments with a moist energy balance model. This work will help identify the largest sources of uncertainty regarding ITCZ shifts under solar geoengineering, and will help improve our understanding of the reasons for the residual polar amplification that occurs in the G1 experiment.

  17. Surface ocean carbon dioxide during the Atlantic Meridional Transect (1995-2013); evidence of ocean acidification

    Science.gov (United States)

    Kitidis, Vassilis; Brown, Ian; Hardman-Mountford, Nicholas; Lefèvre, Nathalie

    2017-11-01

    Here we present more than 21,000 observations of carbon dioxide fugacity in air and seawater (fCO2) along the Atlantic Meridional Transect (AMT) programme for the period 1995-2013. Our dataset consists of 11 southbound and 2 northbound cruises in boreal autumn and spring respectively. Our paper is primarily focused on change in the surface-ocean carbonate system during southbound cruises. We used observed fCO2 and total alkalinity (TA), derived from salinity and temperature, to estimate dissolved inorganic carbon (DIC) and pH (total scale). Using this approach, estimated pH was consistent with spectrophotometric measurements carried out on 3 of our cruises. The AMT cruises transect a range of biogeographic provinces where surface Chlorophyll-α spans two orders of magnitude (mesotrophic high latitudes to oligotrophic subtropical gyres). We found that surface Chlorophyll-α was negatively correlated with fCO2, but that the deep chlorophyll maximum was not a controlling variable for fCO2. Our data show clear evidence of ocean acidification across 100° of latitude in the Atlantic Ocean. Over the period 1995-2013 we estimated annual rates of change in: (a) sea surface temperature of 0.01 ± 0.05 °C, (b) seawater fCO2 of 1.44 ± 0.84 μatm, (c) DIC of 0.87 ± 1.02 μmol per kg and (d) pH of -0.0013 ± 0.0009 units. Monte Carlo simulations propagating the respective analytical uncertainties showed that the latter were < 5% of the observed trends. Seawater fCO2 increased at the same rate as atmospheric CO2.

  18. MAPEAMENTO DE UNIDADES DE RELEVO NA MÉDIA SERRA DO ESPINHAÇO MERIDIONAL - MG

    Directory of Open Access Journals (Sweden)

    Éric Andrade Rezende

    2011-04-01

    Full Text Available O presente trabalho propõe um mapeamento de unidades de relevo para a porção sul do terço médio da Serra do Espinhaço Meridional. As unidades de relevo foram delimitadas a partir da análise integrada de cartas temáticas e imagens de satélite que permitiram observar variações na morfologia, na altimetria, na declividade, na litoestrutura e na organização da rede de drenagem. A etapa de cartografia digital, processada no software ArcGis 9.2, se baseou na utilização de produtos SRTM (Shuttle Radar Topography Mission. Os procedimentos metodológicos também incluíram trabalhos de campo e pesquisa bibliográfica. Foi empregada a taxonomia do mapeamento geomorfológico proposta pelo IBGE (2009, através da qual foram individualizadas quatorze Unidades Geomorfológicas. As unidades estão distribuídas entre cinco diferentes compartimentos do seguinte modo: dois planaltos, duas escarpas, seis depressões, três conjuntos de cristas e um conjunto de patamares. Foi possível observar que a disposição geral das unidades reflete o forte controle litoestrutural imposto ao relevo regional. Destaca-se a resistência diferenciada das diversas litologias frente aos processos denudacionais e a influência da neotectônica na geomorfogênese.

  19. Wind power

    International Nuclear Information System (INIS)

    2006-06-01

    This road-map proposes by the Group Total aims to inform the public on the wind power. It presents the principles, the technology takes off, its applications and technology focus, the global market trends and the outlooks and Total commitments in the domain. (A.L.B.)

  20. Wind energy

    International Nuclear Information System (INIS)

    Portilla S, L.A.

    1995-01-01

    The wind energy or eolic energy is a consequence of solar energy, the one which is absorbed by the atmosphere and is transformed into energy of movement of large bulks of air. In this process the atmosphere acts as the filter to the solar radiation and demotes the ultraviolet beams that result fatal to life in the Earth. The ionosphere is the most external cap and this is ionized by means of absorption process of ultraviolet radiation arising to the Sun. The atmosphere also acts as a trap to the infrared radiation, it that results from the continual process of energetic degradation. In this way, the interaction between Earth - Atmospheres, is behaved as a great greenhouse, maintaining the constant temperatures, including in the dark nights. Processes as the natural convection (that occur by the thermodynamic phenomenon), equatorial calmness, trade winds and against trade winds and global distribution of the air currents are described. The other hand, techniques as the transformation of the wind into energy and its parameters also are shown

  1. Wind Energy Japan

    Energy Technology Data Exchange (ETDEWEB)

    Komatsubara, Kazuyo [Embassy of the Kingdom of the Netherlands, Tokyo (Japan)

    2012-06-15

    An overview is given of wind energy in Japan: Background; Wind Energy in Japan; Japanese Wind Energy Industry; Government Supports; Useful Links; Major Japanese Companies; Profiles of Major Japanese Companies; Major Wind Energy Projects in Japan.

  2. High-resolution vertical velocities and their power spectrum observed with the MAARSY radar - Part 1: frequency spectrum

    Science.gov (United States)

    Li, Qiang; Rapp, Markus; Stober, Gunter; Latteck, Ralph

    2018-04-01

    The Middle Atmosphere Alomar Radar System (MAARSY) installed at the island of Andøya has been run for continuous probing of atmospheric winds in the upper troposphere and lower stratosphere (UTLS) region. In the current study, we present high-resolution wind measurements during the period between 2010 and 2013 with MAARSY. The spectral analysis applying the Lomb-Scargle periodogram method has been carried out to determine the frequency spectra of vertical wind velocity. From a total of 522 days of observations, the statistics of the spectral slope have been derived and show a dependence on the background wind conditions. It is a general feature that the observed spectra of vertical velocity during active periods (with wind velocity > 10 m s-1) are much steeper than during quiet periods (with wind velocity active periods, whereas a very asymmetric distribution with a maximum at around -1 is observed during quiet periods. The slope profiles along altitudes reveal a significant height dependence for both conditions, i.e., the spectra become shallower with increasing altitudes in the upper troposphere and maintain roughly a constant slope in the lower stratosphere. With both wind conditions considered together the general spectra are obtained and their slopes are compared with the background horizontal winds. The comparisons show that the observed spectra become steeper with increasing wind velocities under quiet conditions, approach a spectral slope of -5/3 at a wind velocity of 10 m s-1 and then roughly maintain this slope (-5/3) for even stronger winds. Our findings show an overall agreement with previous studies; furthermore, they provide a more complete climatology of frequency spectra of vertical wind velocities under different wind conditions.

  3. Wavelength Drift Corrector for Wind Lidar Receivers, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose a key innovation to improve wavelength-sensitive lidar measurements (such as wind velocity) using photon-counting receivers. A novel binning technique to...

  4. Lidar Wind Profiler for the NextGen Airportal Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of a standoff sensor that can measure 3D components of wind velocity in the vicinity of an airport has the potential to improve airport throughput,...

  5. Retrieval of sea surface velocities using sequential ocean colour monitor (OCM) data

    Digital Repository Service at National Institute of Oceanography (India)

    Prasad, J.S.; Rajawat, A.S.; Pradhan, Y.; Chauhan, O.S.; Nayak, S.R.

    patterns in successive images. The technique provides actual flow during a specified period by integrating both tidal and wind influences. The current velocities retrieved were compared with synchronous data collected along east coast during GSI cruise ST...

  6. On the dependence of sea surface roughness on wind waves

    DEFF Research Database (Denmark)

    Johnson, H.K.; Højstrup, J.; Vested, H.J.

    1998-01-01

    The influence of wind waves on the momentum transfer (wind stress) between the atmosphere and sea surface was studied using new measured data from the RASEX experiment and other datasets compiled by Donelan et al. Results of the data analysis indicate that errors in wind friction velocity u...... that calculations of the wind friction velocities using the wave-spectra-dependent expression of Hansen and Larsen agrees quite well with measured values during RASEX. It also gives a trend in Charnock parameter consistent with that found by combining the field data. Last, calculations using a constant Charnock...... parameter (0.018) also give very good results for the wind friction velocities at the RASEX site....

  7. Boundary layer heights derived from velocity spectra

    Energy Technology Data Exchange (ETDEWEB)

    Hoejstrup, J.; Barthelmie, R.J. [Risoe National Lab., Roskilde (Denmark); Kaellstrand, B. [Univ. of Uppsala, Uppsala (Sweden)

    1997-10-01

    It is a well-known fact that the height of the mixed layer determines the size of the largest and most energetic eddies that can be observed in the unstable boundary layer, and consequently a peak can be observed in the power spectra of the along-wind velocity component at scales comparable to the mixed layer depth. We will now show how the mixed layer depth can be derived from the u-specta and the results will be compared with direct measurements using pibal and tethersonde measurements. (au)

  8. Thermal Assessment of a Novel Combine Evaporative Cooling Wind Catcher

    Directory of Open Access Journals (Sweden)

    Azam Noroozi

    2018-02-01

    Full Text Available Wind catchers are one of the oldest cooling systems that are employed to provide sufficient natural ventilation in buildings. In this study, a laboratory scale wind catcher was equipped with a combined evaporative system. The designed assembly was comprised of a one-sided opening with an adjustable wetted pad unit and a wetted blades section. Theoretical analysis of the wind catcher was carried out and a set of experiments were organized to validate the results of the obtained models. The effect of wind speed, wind catcher height, and mode of the opening unit (open or closed was investigated on temperature drop and velocity of the moving air through the wind catcher as well as provided sensible cooling load. The results showed that under windy conditions, inside air velocity was slightly higher when the pad was open. Vice versa, when the wind speed was zero, the closed pad resulted in an enhancement in air velocity inside the wind catcher. At wind catcher heights of 2.5 and 3.5 m and wind speeds of lower than 3 m/s, cooling loads have been approximately doubled by applying the closed-pad mode.

  9. Velocity pump reaction turbine

    Science.gov (United States)

    House, P.A.

    An expanding hydraulic/two-phase velocity pump reaction turbine including a dual concentric rotor configuration with an inter-rotor annular flow channel in which the inner rotor is mechanically driven by the outer rotor. In another embodiment, the inner rotor is immobilized and provided with gas recovery ports on its outer surface by means of which gas in solution may be recovered. This velocity pump reaction turbine configuration is capable of potential energy conversion efficiencies of up to 70%, and is particularly suited for geothermal applications.

  10. The Prescribed Velocity Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...... description of this momentum flow. The Prescribed Velocity Method is a practical method for the description of an Air Terminal Device which will save grid points close to the opening and ensure the right level of the momentum flow....

  11. Characterising Turbulence Intensity for Fatigue Load Analysis of Wind Turbines

    DEFF Research Database (Denmark)

    Hansen, Kurt Schaldemose; Larsen, Gunner Chr.

    2005-01-01

    Turbulence in wind velocity presents a major factor for modern wind turbine design as cost reduction as are sort for the dynamic structures. Therefore this paper contains a parametrisation of the turbulence intensity at given sites, relevant for the calculation of fatigue loading of wind turbines....... The parameterisation is based on wind speed measurements extracted from the “Database on Wind Characteristics” (www.winddata.com). The parameterisation is based on the LogNormal distribution, which has proven to be suitable distribution to describe the turbulence intensity distribution....

  12. Simulations of large winds and wind shears induced by gravity wave breaking in the mesosphere and lower thermosphere (MLT region

    Directory of Open Access Journals (Sweden)

    X. Liu

    2014-05-01

    Full Text Available Using a fully nonlinear two-dimensional (2-D numerical model, we simulated gravity waves (GWs breaking and their contributions to the formation of large winds and wind shears in the mesosphere and lower thermosphere (MLT. An eddy diffusion coefficient is used in the 2-D numerical model to parameterize realistic turbulent mixing. Our study shows that the momentum deposited by breaking GWs accelerates the mean wind. The resultant large background wind increases the GW's apparent horizontal phase velocity and decreases the GW's intrinsic frequency and vertical wavelength. Both the accelerated mean wind and the decreased GW vertical wavelength contribute to the enhancement of wind shears. This, in turn, creates a background condition that favors the occurrence of GW instability, breaking, and momentum deposition, as well as mean wind acceleration, which further enhances the wind shears. We find that GWs with longer vertical wavelengths and faster horizontal phase velocity can induce larger winds, but they may not necessarily induce larger wind shears. In addition, the background temperature can affect the time and height of GW breaking, thus causing accelerated mean winds and wind shears.

  13. Hemispherically asymmetric trade wind changes as signatures of past ITCZ shifts

    Science.gov (United States)

    McGee, David; Moreno-Chamarro, Eduardo; Green, Brian; Marshall, John; Galbraith, Eric; Bradtmiller, Louisa

    2018-01-01

    The atmospheric Hadley cells, which meet at the Intertropical Convergence Zone (ITCZ), play critical roles in transporting heat, driving ocean circulation and supplying precipitation to the most heavily populated regions of the globe. Paleo-reconstructions can provide concrete evidence of how these major features of the atmospheric circulation can change in response to climate perturbations. While most such reconstructions have focused on ITCZ-related rainfall, here we show that trade wind proxies can document dynamical aspects of meridional ITCZ shifts. Theoretical expectations based on angular momentum constraints and results from freshwater hosing simulations with two different climate models predict that ITCZ shifts due to anomalous cooling of one hemisphere would be accompanied by a strengthening of the Hadley cell and trade winds in the colder hemisphere, with an opposite response in the warmer hemisphere. This expectation of hemispherically asymmetric trade wind changes is confirmed by proxy data of coastal upwelling and windblown dust from the Atlantic basin during Heinrich stadials, showing trade wind strengthening in the Northern Hemisphere and weakening in the Southern Hemisphere subtropics in concert with southward ITCZ shifts. Data from other basins show broadly similar patterns, though improved constraints on past trade wind changes are needed outside the Atlantic Basin. The asymmetric trade wind changes identified here suggest that ITCZ shifts are also marked by intensification of the ocean's wind-driven subtropical cells in the cooler hemisphere and a weakening in the warmer hemisphere, which induces cross-equatorial oceanic heat transport into the colder hemisphere. This response would be expected to prevent extreme meridional ITCZ shifts in response to asymmetric heating or cooling. Understanding trade wind changes and their coupling to cross-equatorial ocean cells is key to better constraining ITCZ shifts and ocean and atmosphere dynamical

  14. Wind Loads on Structures

    DEFF Research Database (Denmark)

    Dyrbye, Claes; Hansen, Svend Ole

    Wind loads have to be taken into account when designing civil engineering structures. The wind load on structures can be systematised by means of the wind load chain: wind climate (global), terrain (wind at low height), aerodynamic response (wind load to pressure), mechanical response (wind...... pressure to structural response) and design criteria. Starting with an introduction of the wind load chain, the book moves on to meteorological considerations, atmospheric boundary layer, static wind load, dynamic wind load and scaling laws used in wind-tunnel tests. The dynamic wind load covers vibrations...... induced by wind turbulence, vortex shedding, flutter and galloping. The book gives a comprehensive treatment of wind effects on structures and it will be useful for consulting engineers designing wind-sensitive structures. It will also be valuable for students of civil engineering as textbook...

  15. Modelling Wind Turbine Inflow: The Induction Zone

    DEFF Research Database (Denmark)

    Meyer Forsting, Alexander Raul

    to the rotor, but requires exact knowledge of the flow deceleration to estimate the available, undis- turbed kinetic energy. Thus this thesis explores, mostly numerically, any wind turbine or environmental dependencies of this deceleration. The computational fluid dynamics model (CFD) employed is validated......A wind turbine decelerates the wind in front of its rotor by extracting kinetic energy. The wind speed reduction is maximal at the rotor and negligible more than five rotor radii upfront. By measuring wind speed this far from the rotor, the turbine’s performance is determined without any rotor bias...... significant parameter. Exploiting this singu- lar dependency, a fast semi-empirical model is devised that accurately predicts the velocity deficit upstream of a single turbine. Near-rotor mea-surements in combination with this model are able to retrieve the kinetic energy available to the turbine in flat...

  16. Investigation on wind energy-compressed air power system.

    Science.gov (United States)

    Jia, Guang-Zheng; Wang, Xuan-Yin; Wu, Gen-Mao

    2004-03-01

    Wind energy is a pollution free and renewable resource widely distributed over China. Aimed at protecting the environment and enlarging application of wind energy, a new approach to application of wind energy by using compressed air power to some extent instead of electricity put forward. This includes: explaining the working principles and characteristics of the wind energy-compressed air power system; discussing the compatibility of wind energy and compressor capacity; presenting the theoretical model and computational simulation of the system. The obtained compressor capacity vs wind power relationship in certain wind velocity range can be helpful in the designing of the wind power-compressed air system. Results of investigations on the application of high-pressure compressed air for pressure reduction led to conclusion that pressure reduction with expander is better than the throttle regulator in energy saving.

  17. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  18. Doppler Lidar for Wind Measurements on Venus

    Science.gov (United States)

    Singh, Upendra N.; Emmitt, George D.; Yu, Jirong; Kavaya, Michael J.

    2010-01-01

    NASA Langley Research Center has a long history of developing 2-micron laser transmitter for wind sensing. With support from NASA Laser Risk Reduction Program (LRRP) and Instrument Incubator Program (IIP), NASA Langley Research Center has developed a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement. The transmitter portion of the transceiver employs the high-pulse-energy, Ho:Tm:LuLiF, partially conductively cooled laser technology developed at NASA Langley. The transceiver is capable of 250 mJ pulses at 10 Hz. It is very similar to the technology envisioned for coherent Doppler lidar wind measurements from Earth and Mars orbit. The transceiver is coupled to the large optics and data acquisition system in the NASA Langley VALIDAR mobile trailer. The large optics consists of a 15-cm off-axis beam expanding telescope, and a full-hemispheric scanner. Vertical and horizontal vector winds are measured, as well as relative backscatter. The data acquisition system employs frequency domain velocity estimation and pulse accumulation. It permits real-time display of the processed winds and archival of all data. This lidar system was recently deployed at Howard University facility in Beltsville, Mary-land, along with other wind lidar systems. Coherent Doppler wind lidar ground-based wind measurements and comparisons with other sensors will be presented. A simulation and data product for wind measurement at Venus will be presented.

  19. Chaotic variability of the meridional overturning circulation on subannual to interannual timescales

    Directory of Open Access Journals (Sweden)

    J. J.-M. Hirschi

    2013-09-01

    Full Text Available Observations and numerical simulations have shown that the meridional overturning circulation (MOC exhibits substantial variability on sub- to interannual timescales. This variability is not fully understood. In particular it is not known what fraction of the MOC variability is caused by processes such as mesoscale ocean eddies and waves which are ubiquitous in the ocean. Here we analyse twin experiments performed with a global ocean model at eddying (1/4° and non-eddying (1° resolutions. The twin experiments are forced with the same surface fluxes for the 1958 to 2001 period but start from different initial conditions. Our results show that on subannual to interannual timescales a large fraction of MOC variability directly reflects variability in the surface forcing. Nevertheless, in the eddy-permitting case there is an initial-condition-dependent MOC variability (hereinafter referred to as "chaotic" variability of several Sv (1Sv = 106 m3 s−1 in the Atlantic and the Indo-Pacific. In the Atlantic the chaotic MOC variability represents up to 30% of the total variability at the depths where the maximum MOC occurs. In comparison the chaotic MOC variability is only 5–10% in the non-eddying case. The surface forcing being almost identical in the twin experiments suggests that mesoscale ocean eddies are the most likely cause for the increased chaotic MOC variability in the eddying case. The exact formation time of eddies is determined by the initial conditions which are different in the two model passes, and as a consequence the mesoscale eddy field is decorrelated in the twin experiments. In regions where eddy activity is high in the eddy-permitting model, the correlation of sea surface height variability in the twin runs is close to zero. In the non-eddying case in contrast, we find high correlations (0.9 or higher over most regions. Looking at the sub- and interannual MOC components separately reveals that most of the chaotic MOC variability

  20. The importance of deep, basinwide measurements in optimized Atlantic Meridional Overturning Circulation observing arrays

    Science.gov (United States)

    McCarthy, G. D.; Menary, M. B.; Mecking, J. V.; Moat, B. I.; Johns, W. E.; Andrews, M. B.; Rayner, D.; Smeed, D. A.

    2017-03-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a key process in the global redistribution of heat. The AMOC is defined as the maximum of the overturning stream function, which typically occurs near 30°N in the North Atlantic. The RAPID mooring array has provided full-depth, basinwide, continuous estimates of this quantity since 2004. Motivated by both the need to deliver near real-time data and optimization of the array to reduce costs, we consider alternative configurations of the mooring array. Results suggest that the variability observed since 2004 could be reproduced by a single tall mooring on the western boundary and a mooring to 1500 m on the eastern boundary. We consider the potential future evolution of the AMOC in two generations of the Hadley Centre climate models and a suite of additional CMIP5 models. The modeling studies show that deep, basinwide measurements are essential to capture correctly the future decline of the AMOC. We conclude that, while a reduced array could be useful for estimates of the AMOC on subseasonal to decadal time scales as part of a near real-time data delivery system, extreme caution must be applied to avoid the potential misinterpretation or absence of a climate time scale AMOC decline that is a key motivation for the maintenance of these observations.Plain Language SummaryThe Atlantic Overturning Circulation is a system of ocean currents that carries heat northwards in the Atlantic. This heat is crucial to maintaining the mild climate of northwest Europe. The Overturning Circulation is predicted to slow in future in response to man-made climate change. The RAPID program is designed to measure the Overturning Circulation using a number of fixed point observations spanning the Atlantic between the Canary Islands and the Bahamas. We look at whether we could reduce the number of these fixed point observations to continue to get accurate estimates of the overturning strength but for less cost. We conclude that

  1. Meltwater routing and the Atlantic meridional overturning circulation: A Gulf of Mexico perspective

    Science.gov (United States)

    Flower, B. P.; Williams, C.; Randle, N.; Hastings, D. W.

    2008-12-01

    Routing of low-salinity meltwater from the Laurentide Ice Sheet (LIS) into the North Atlantic via eastern outlets (e.g., St. Lawrence and Hudson River systems) and northern outlets (e.g., Hudson Bay and Arctic Ocean) is thought to have reduced Atlantic meridional overturning circulation (AMOC) and thereby triggered rapid regional to global climate change during the last glacial cycle. In contrast, southward meltwater flow to the Gulf of Mexico is generally thought to allow enhanced AMOC and warmer climates in the North Atlantic region. Situated at the outlet of the Mississippi River system, Orca Basin is ideally located to record meltwater input from the LIS. Orca Basin core MD02-2550 collected by the R/V Marion Dufresne in 2002 on IMAGES cruise VIII allows sub-centennial-scale records of Mg/Ca sea-surface temperature (SST) and δ18Oseawater back to ca. 23.9 ka. Accumulation rates average about 40 cm/k.y. Our current data extend from ca. 16.5-7 ka, with age control provided by 40 AMS radiocarbon dates (nearly all in stratigraphic order; calibrated using Calib 5.0.2). We use paired Mg/Ca and oxygen isotope data on Globigerinoides ruber to isolate changes in the oxygen isotopic composition of seawater. Four major episodic δ18O decreases of more than 2 per mil indicate substantial LIS meltwater input. Intervals of major meltwater discharge to the Gulf of Mexico do not appear to match known pulses of global sea level increase. However, abrupt reductions in southward meltwater input to the Gulf of Mexico seem to correlate with abrupt coolings in the North Atlantic region (e.g., Younger Dryas, Intra-Allerod cold period, and Oldest Dryas). In particular, a 3.5 per mil δ18O increase centered at 10,970 radiocarbon years B.P. (the "cessation event") appears to coincide with the onset of the Younger Dryas in European lakes and with Δ14C evidence from Cariaco Basin for AMOC reduction. Furthermore, recent results with the NCAR Community Climate System model (CCSM3) indicate

  2. Turbulent Flow Inside and Above a Wind Farm: A Wind-Tunnel Study

    Directory of Open Access Journals (Sweden)

    Leonardo P. Chamorro

    2011-11-01

    Full Text Available Wind-tunnel experiments were carried out to better understand boundary layer effects on the flow pattern inside and above a model wind farm under thermally neutral conditions. Cross-wire anemometry was used to characterize the turbulent flow structure at different locations around a 10 by 3 array of model wind turbines aligned with the mean flow and arranged in two different layouts (inter-turbine separation of 5 and 7 rotor diameters in the direction of the mean flow by 4 rotor diameters in its span. Results suggest that the turbulent flow can be characterized in two broad regions. The first, located below the turbine top tip height, has a direct effect on the performance of the turbines. In that region, the turbulent flow statistics appear to reach equilibrium as close as the third to fourth row of wind turbines for both layouts. In the second region, located right above the first one, the flow adjusts slowly. There, two layers can be identified: an internal boundary layer where the flow is affected by both the incoming wind and the wind turbines, and an equilibrium layer, where the flow is fully adjusted to the wind farm. An adjusted logarithmic velocity distribution is observed in the equilibrium layer starting from the sixth row of wind turbines. The effective surface roughness length induced by the wind farm is found to be higher than that predicted by some existing models. Momentum recovery and turbulence intensity are shown to be affected by the wind farm layout. Power spectra show that the signature of the tip vortices, in both streamwise and vertical velocity components, is highly affected by both the relative location in the wind farm and the wind farm layout.

  3. Wind power variations under humid and arid meteorological conditions

    International Nuclear Information System (INIS)

    Şen, Zekâi

    2013-01-01

    Highlights: • It indicates the role of weather parameters’ roles in the wind energy calculation. • Meteorological variables are more significant in arid regions for wind power. • It provides opportunity to take into consideration air density variability. • Wind power is presented in terms of the wind speed, temperature and pressure. - Abstract: The classical wind power per rotor area per time is given as the half product of the air density by third power of the wind velocity. This approach adopts the standard air density as constant (1.23 g/cm 3 ), which ignores the density dependence on air temperature and pressure. Weather conditions are not taken into consideration except the variations in wind velocity. In general, increase in pressure and decrease in temperature cause increase in the wind power generation. The rate of increase in the pressure has less effect on the wind power as compared with the temperature rate. This paper provides the wind power formulation based on three meteorological variables as the wind velocity, air temperature and air pressure. Furthermore, from the meteorology point of view any change in the wind power is expressed as a function of partial changes in these meteorological variables. Additionally, weather conditions in humid and arid regions differ from each other, and it is interesting to see possible differences between the two regions. The application of the methodology is presented for two meteorology stations in Istanbul, Turkey, as representative of the humid regions and Al-Madinah Al-Monawwarah, Kingdom of Saudi Arabia, for arid region, both on daily record bases for 2010. It is found that consideration of air temperature and pressure in the average wind power calculation gives about 1.3% decrease in Istanbul, whereas it is about 13.7% in Al-Madinah Al-Monawwarah. Hence, consideration of meteorological variables in wind power calculations becomes more significant in arid regions

  4. Wind conditions for wind turbine design

    Energy Technology Data Exchange (ETDEWEB)

    Maribo Pedersen, B.

    1999-04-01

    Delegates from Europe and USA attended the meeting and discussed general aspects of wind conditions for wind turbine design. The subjects and the presented papers covered a very broad range of aspects of wind conditions and related influence on the wind turbine. (EHS)

  5. Chaos in the solar wind flow near Earth

    Indian Academy of Sciences (India)

    We have done a time series analysis of daily average data of solar wind velocity, density and temperature at 1 AU measured by ACE spacecraft for a period of nine years. We have used the raw data without filtering to give a faithful representation of the nonlinear behaviour of the solar wind flow which is a novel one.

  6. Chaos in the solar wind flow near Earth

    Indian Academy of Sciences (India)

    Abstract. We have done a time series analysis of daily average data of solar wind velocity, density and temperature at 1 AU measured by ACE spacecraft for a period of nine years. We have used the raw data without filtering to give a faithful representation of the nonlinear behaviour of the solar wind flow which is a novel one ...

  7. On the length-scale of the wind profile

    DEFF Research Database (Denmark)

    Pena Diaz, Alfredo; Gryning, Sven-Erik; Mann, Jakob

    2010-01-01

    We present the results of an analysis of simultaneous sonic anemometer observations of wind speed and velocity spectra over flat and homogeneous terrain from 10 up to 160 m height performed at the National Test Station for Wind Turbines at Høvsøre, Denmark. The mixing length, l, derived from the ...

  8. Diurnal, monthly and seasonal variation of mean winds in the MLT region observed over Kolhapur using MF radar

    Science.gov (United States)

    Sharma, A. K.; Gaikwad, H. P.; Ratnam, M. Venkat; Gurav, O. B.; Ramanjaneyulu, L.; Chavan, G. A.; Sathishkumar, S.

    2018-04-01

    Medium Frequency (MF) radar located at Kolhapur (16.8°N, 74.2°E) has been upgraded in August 2013. Since then continuous measurements of zonal and meridional winds are obtained covering larger altitudes from the Mesosphere and Lower Thermosphere (MLT) region. Diurnal, monthly and seasonal variation of these mean winds is presented in this study using four years (2013-2017) of observations. The percentage occurrence of radar echoes show maximum between 80 and 105 km. The mean meridional wind shows Annual Oscillation (AO) between 80 and 90 km altitudes with pole-ward motion during December solstice and equatorial motion during June solstice. Quasi-biennial oscillation (QBO) with weaker amplitudes are also observed between 90 and 104 km. Zonal winds show semi-annual oscillation (SAO) with westward winds during equinoxes and eastward winds during solstices between 80 and 90 km. AO with eastward winds during December solstice and westward wind in the June solstice is also observed in the mean zonal wind between 100 and 110 km. These results match well with that reported from other latitudes within Indian region between 80 and 90 km. However, above 90 km the results presented here provide true mean background winds for the first time over Indian low latitude region as the present station is away from equatorial electro-jet and are not contaminated by ionospheric processes. Further, the results presented earlier with an old version of this radar are found contaminated due to unknown reasons and are corrected in the present work. This upgraded MF radar together with other MLT radars in the Indian region forms unique network to investigate the vertical and lateral coupling.

  9. "What Controls the Structure and Stability of the Ocean Meridional Overturning Circulation: Implications for Abrupt Climate Change?"

    Energy Technology Data Exchange (ETDEWEB)

    Fedorov, Alexey [Yale University

    2013-11-23

    The central goal of this research project is to understand the properties of the ocean meridional overturning circulation (MOC) – a topic critical for understanding climate variability and stability on a variety of timescales (from decadal to centennial and longer). Specifically, we have explored various factors that control the MOC stability and decadal variability in the Atlantic and the ocean thermal structure in general, including the possibility abrupt climate change. We have also continued efforts on improving the performance of coupled ocean-atmosphere GCMs.

  10. De Indios “Bárbaros” a Vasallos en la Frontera Meridional Chilena Durante el Reformismo Borbónico.

    OpenAIRE

    Chauca García, Jorge

    2017-01-01

    Con la presente Tesis Doctoral abordamos críticamente la visión ilustrada del indígena de la frontera meridional chilena como marco geográfico y la centuria de la Ilustración como coordenada temporal, especialmente su segunda mitad. Un análisis de sus tres familias básicas que no contempla por razones cronológicas a los picunches o gentes del norte, pero sí a los mapuches –gente de la tierra–, huilliches –gente...

  11. Tuning facial-meridional isomerisation in monometallic nine-co-ordinate lanthanide complexes with unsymmetrical tridentate ligands.

    Science.gov (United States)

    Le Borgne, Thierry; Altmann, Peter; André, Nicolas; Bünzli, Jean-Claude G; Bernardinelli, Gérald; Morgantini, Pierre-Yves; Weber, Jacques; Piguet, Claude

    2004-03-07

    The unsymmetrical tridentate benzimidazole-pyridine-carboxamide units in ligands L1-L4 react with trivalent lanthanides, Ln(III), to give the nine-co-ordinate triple-helical complexes [Ln(Li)3]3+ (i = 1-4) existing as mixtures of C3-symmetrical facial and C1-symmetrical meridional isomers. Although the beta13 formation constants are 3-4 orders of magnitude smaller for these complexes than those found for the D3-symmetrical analogues [Ln(Li)3]3+ (i = 5-6) with symmetrical ligands, their formation at the millimolar scale is quantitative and the emission quantum yield of [Eu(L2)3]3+ is significantly larger. The fac-[Ln(Li)3]3+ mer-[Ln(Li)3]3+ (i = 1-4) isomerisation process in acetonitrile is slow enough for Ln = Lu(III) to be quantified by 1H NMR below room temperature. The separation of enthalpic and entropic contributions shows that the distribution of the facial and meridional isomers can be tuned by the judicious peripheral substitution of the ligands affecting the interstrand interactions. Molecular mechanics (MM) calculations suggest that one supplementary interstrand pi-stacking interaction stabilises the meridional isomers, while the facial isomers benefit from more favourable electrostatic contributions. As a result of the mixture of facial and meridional isomers in solution, we were unable to obtain single crystals of 1:3 complexes, but the X-ray crystal structures of their nine-co-ordinate precursors [Eu(L1)2(CF3SO3)2(H2O)](CF3SO3)(C3H5N)2(H2O) (6, C45H54EuF9N10O13S3, monoclinic, P2(1)/c, Z = 4) and [Eu(L4)2(CF3SO3)2(H2O)](CF3SO3)(C4H4O)(1.5) (7, C51H66EuF9N8O(15.5)S3, triclinic, P1, Z = 2) provide crucial structural information on the binding mode of the unsymmetrical tridentate ligands.

  12. Wave propagation and group velocity

    CERN Document Server

    Brillouin, Léon

    1960-01-01

    Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter

  13. Polar solar wind and interstellar wind properties from interplanetary Lyman-alpha radiation measurements

    Science.gov (United States)

    Witt, N.; Blum, P. W.; Ajello, J. M.

    1981-01-01

    The analysis of Mariner 10 observations of Lyman-alpha resonance radiation shows an increase of interplanetary neutral hydrogen densities above the solar poles. This increase is caused by a latitudinal variation of the solar wind velocity and/or flux. Using both the Mariner 10 results and other solar wind observations, the values of the solar wind flux and velocity with latitude are determined for several cases of interest. The latitudinal variation of interplanetary hydrogen gas, arising from the solar wind latitudinal variation, is shown to be most pronounced in the inner solar system. From this result it is shown that spacecraft Lyman-alpha observations are more sensitive to the latitudinal anisotropy for a spacecraft location in the inner solar system near the downwind axis.

  14. Wind shear proportional errors in the horizontal wind speed sensed by focused, range gated lidars

    DEFF Research Database (Denmark)

    Lindelöw, Per Jonas Petter; Courtney, Michael; Parmentier, R.

    2008-01-01

    altitude. The altitude errors of focused range gated lidars are likely to arise partly from an unaccounted shift of the weighting functions, describing the sample volume, due to the range dependent collection efficiency of the focused telescope. Possibilities of correcting the lidar measurements both...... an altitude dependent relation between the lidar error and the wind shear. A likely explanation for this relation is an error in the intended sensing altitude. At most this error is estimated to 9 in which induced errors in the horizontal wind velocity of up to 0.5 m/s as compared to a cup at the intended...... for wind velocity and wind shear dependent errors are discussed. The 2-parametric regression analysis described in this paper is proven to be a better approach when acceptance testing and calibrating lidars....

  15. Wind Technologies & Evolving Opportunities (Presentation)

    Energy Technology Data Exchange (ETDEWEB)

    Robichaud, R.

    2014-07-01

    This presentation covers opportunities for wind technology; wind energy market trends; an overview of the National Wind Technology Center near Boulder, Colorado; wind energy price and cost trends; wind turbine technology improvements; and wind resource characterization improvements.

  16. Gas transfer velocities in small forested ponds

    Science.gov (United States)

    Holgerson, Meredith A.; Farr, Emily R.; Raymond, Peter A.

    2017-05-01

    Inland waters actively exchange gases with the atmosphere, and the gas exchange rate informs system biogeochemistry, ecology, and global carbon budgets. Gas exchange in medium- to large-sized lakes is largely regulated by wind; yet less is known about processes regulating gas transfer in small ponds where wind speeds are low. In this study, we determined the gas transfer velocity, k600, in four small (water temperature; however, the explanatory power was weak (R2 water bodies, we compiled direct measurements of k600 from 67 ponds and lakes worldwide. Our k600 estimates were within the range of estimates for other small ponds, and variability in k600 increased with lake size. However, the majority of studies were conducted on medium-sized lakes (0.01 to 1 km2), leaving small ponds and large lakes understudied. Overall, this study adds four small ponds to the existing body of research on gas transfer velocities from inland waters and highlights uncertainty in k600, with implications for calculating metabolism and carbon emissions in inland waters.

  17. Transverse Spectral Velocity Estimation

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2014-01-01

    array probe is used along with two different estimators based on the correlation of the received signal. They can estimate the velocity spectrum as a function of time as for ordinary spectrograms, but they also work at a beam-to-flow angle of 90°. The approach is validated using simulations of pulsatile...... flow using the Womersly–Evans flow model. The relative bias of the mean estimated frequency is 13.6% and the mean relative standard deviation is 14.3% at 90°, where a traditional estimator yields zero velocity. Measurements have been conducted with an experimental scanner and a convex array transducer....... A pump generated artificial femoral and carotid artery flow in the phantom. The estimated spectra degrade when the angle is different from 90°, but are usable down to 60° to 70°. Below this angle the traditional spectrum is best and should be used. The conventional approach can automatically be corrected...

  18. Variable Winds in Early-B Hypergiants

    Science.gov (United States)

    Wolf, Bernhard; Rivinius, Thomas

    Early-B hypergiants belong to the most luminous stars in the Universe. They are characterized by high mass-loss rates (dot M≈ 10-5 M⊙yr-1) and low terminal wind velocities (v ∞≈400 km s-1) implying very dense winds. They represent a short-lived evolutionary phase and are of particular interest for evolutionary theories of massive stars with mass loss. Due to their high luminosity they play a key role in connection with the "wind momentum — luminosity relation". Among the main interesting characteristics of early-B hypergiants are the various kinds of photometric and spectroscopic variations. In several recent campaigns our group has performed extensive high dispersion spectroscopy of galactic early-B hypergiants with our fiber-fed echelle spectrograph Flash/Heros at the ESO-50 cm telescope. The main outcome was that their dense winds behave hydrodynamically differently to the less luminous supergiants of comparable spectral type. Outwardly accelerated propagating discrete absorption components of the P Cyg-type lines are the typical features rather than rotationally modulated line profile variations. These discrete absorptions could be traced in different spectral lines from photospheric velocities up to 75% of the terminal velocity. The stellar absorption lines show a pulsation-like radial velocity variability pattern lasting up to two weeks as the typical time scale. The radius variations connected with this pulsation-like motions are correlated with the emission height of the P Cyg-type profiles.

  19. Generation of the lower-thermospheric vertical wind estimated with the EISCAT KST radar at high latitudes during periods of moderate geomagnetic disturbance

    Directory of Open Access Journals (Sweden)

    S. Oyama

    2008-06-01

    Full Text Available Lower-thermospheric winds at high latitudes during moderately-disturbed geomagnetic conditions were studied using data obtained with the European Incoherent Scatter (EISCAT Kiruna-Sodankylä-Tromsø (KST ultrahigh frequency (UHF radar system on 9–10 September 2004. The antenna-beam configuration was newly designed to minimize the estimated measurement error of the vertical neutral-wind speed in the lower thermosphere. This method was also available to estimate the meridional and zonal components. The vertical neutral-wind speed at 109 km, 114 km, and 120 km heights showed large upward motions in excess of 30 m s−1 in association with an ionospheric heating event. Large downward speeds in excess of −30 m s−1 were also observed before and after the heating event. The meridional neutral-wind speed suddenly changed its direction from equatorward to poleward when the heating event began, and then returned equatorward coinciding with a decrease in the heating event. The magnetometer data from northern Scandinavia suggested that the center of the heated region was located about 80 km equatorward of Tromsø. The pressure gradient caused the lower-thermospheric wind to accelerate obliquely upward over Tromsø in the poleward direction. Acceleration of the neutral wind flowing on a vertically tilted isobar produced vertical wind speeds larger by more than two orders of magnitude than previously predicted, but still an order of magnitude smaller than observed speeds.

  20. Generation of the lower-thermospheric vertical wind estimated with the EISCAT KST radar at high latitudes during periods of moderate geomagnetic disturbance

    Directory of Open Access Journals (Sweden)

    S. Oyama

    2008-06-01

    Full Text Available Lower-thermospheric winds at high latitudes during moderately-disturbed geomagnetic conditions were studied using data obtained with the European Incoherent Scatter (EISCAT Kiruna-Sodankylä-Tromsø (KST ultrahigh frequency (UHF radar system on 9–10 September 2004. The antenna-beam configuration was newly designed to minimize the estimated measurement error of the vertical neutral-wind speed in the lower thermosphere. This method was also available to estimate the meridional and zonal components. The vertical neutral-wind speed at 109 km, 114 km, and 120 km heights showed large upward motions in excess of 30 m s−1 in association with an ionospheric heating event. Large downward speeds in excess of −30 m s−1 were also observed before and after the heating event. The meridional neutral-wind speed suddenly changed its direction from equatorward to poleward when the heating event began, and then returned equatorward coinciding with a decrease in the heating event. The magnetometer data from northern Scandinavia suggested that the center of the heated region was located about 80 km equatorward of Tromsø. The pressure gradient caused the lower-thermospheric wind to accelerate obliquely upward over Tromsø in the poleward direction. Acceleration of the neutral wind flowing on a vertically tilted isobar produced vertical wind speeds larger by more than two orders of magnitude than previously predicted, but still an order of magnitude smaller than observed speeds.

  1. Kahuku, Oahu wind summary. Period covered: August--November 1976

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, D.M.; Zalkan, R.L.; Walton, J.J.; Hill, K.L.

    1977-02-01

    Wind-energy measurements conducted by the Lawrence Livermore Laboratory on the island of Oahu, Hawaii, are discussed briefly. Measurement locations in northern Oahu are identified. The measurement site at Kahuku, Oahu, is described. Data obtained at the Kahuku location are summarized as daily and monthly mean velocities for August through November, 1976. Velocity duration curves for each month are also given.

  2. Friction velocity and aerodynamic roughness of conventional and undercutter tillage within the Columbia Plateau, USA

    Science.gov (United States)

    Friction velocity and aerodynamic roughness are characteristics of the soil-plant-atmosphere interface which affect wind erosion. Although exchange of momentum at the interface can be altered by land management practices, no attempts have been made to quantify the effect of tillage on friction veloc...

  3. Wind Power Meteorology

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Mortensen, Niels Gylling; Landberg, Lars

    Wind power meteorology has evolved as an applied science, firmly founded on boundary-layer meteorology, but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment, and short-term prediction of the wind...... resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed......: wind profiles and shear, turbulence and gust, and extreme winds. The data used in wind power meteorology stem mainly from three sources: onsite wind measurements, the synoptic networks, and the re-analysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed...

  4. LA PROYECCIÓN TALASOPOLÍTICA DE CHINA Y LAS DISPUTAS TERRITORIALES EN EL MAR MERIDIONAL

    Directory of Open Access Journals (Sweden)

    Lucas Pavez Rosales

    2017-04-01

    Full Text Available Este trabajo investigativo se funda en el objetivo de analizar la proyección talasopolítica de la República Popular China ( RPCh, en relación a las tensiones en el mar de la China meridional como yuxtaposición de intereses económicos y políticos entre los Estados involucrados. Siendo objetivos específicos: 1 dimensionar costos y factibilidad del creciente esfuerzo chino de configurarse como potencia marítima; 2 develar la unidad fragmentación de la postura de los miembros ASEAN frente a China, en la disputa; y 3 evidenciar la estrategia de EUA para hacer frente al cuestionamiento a su hegemonía en la región. A partir de esta base, el escrito busca dilucidar la forma en que el mar meridional se ha convertido en la nueva zona geopolítica caliente en el Sistema-mundo, y en la cual se puede producir una vorágine de conflictividad que desestabilice a la región.

  5. The Atlantic Meridional Transect: Spatially Extensive Calibration and Validation of Optical Properties and Remotely Sensed Measurements of Ocean Colour

    Science.gov (United States)

    Aiken, James; Hooker, Stanford

    1997-01-01

    Twice a year, the Royal Research Ship (RRS) James Clark Ross (JCR) steams a meridional transect of the atlantic Ocean between Grimsly (UK) and Stanley (Falkland Islands) with a port call in Montevideo (Uruguay), as part of the annual research activities of the British Antarctic Survey (BAS). In September, the JCR sails from the UK, and the following April it makes the return trip. The ship is operated by the BAS for the Natural Environment Research Council (NERC). The Atlantic Meridional Transect (AMT) Program exploits the passage of the JCR from approximately 50 deg. N to 50 deg. S with a primary objective to investigate physical and biological processes, as well as to measure the mesi-to-basin-scale bio-optical properties of the atlantic Ocean. The calibration and validation of remotely sensed observations of ocean colour is an inherent objective of these studies: first, by relating in situ measurements of water leaving radiance to satellite measurement, and second, by measuring the bio-optically active constituents of the water.

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

    Directory of Open Access Journals (Sweden)

    F. Tesema

    2017-03-01

    Full Text Available 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

  7. Study of wind forces on low-rise hip-roof building

    African Journals Online (AJOL)

    DR OKE

    Wind pressures on buildings and structures depend upon the velocity profile and turbulence ... the interaction between wind and structures numerically offering an alternative technique to practical applications. Earlier the ..... Areas of research are masonry structures, Computational Fluid Dynamics and Wind engineering.

  8. Prospecting for Wind

    Science.gov (United States)

    Swapp, Andy; Schreuders, Paul; Reeve, Edward

    2011-01-01

    Many people use wind to help meet their needs. Over the years, people have been able to harness or capture the wind in many different ways. More recently, people have seen the rebirth of electricity-generating wind turbines. Thus, the age-old argument about technology being either good or bad can also be applied to the wind. The wind can be a…

  9. Careers in Wind Energy

    Science.gov (United States)

    Liming, Drew; Hamilton, James

    2011-01-01

    As a common form of renewable energy, wind power is generating more than just electricity. It is increasingly generating jobs for workers in many different occupations. Many workers are employed on wind farms: areas where groups of wind turbines produce electricity from wind power. Wind farms are frequently located in the midwestern, western, and…

  10. Turbulent wind waves on a water current

    Directory of Open Access Journals (Sweden)

    M. V. Zavolgensky

    2008-05-01

    Full Text Available An analytical model of water waves generated by the wind over the water surface is presented. A simple modeling method of wind waves is described based on waves lengths diagram, azimuthal hodograph of waves velocities and others. Properties of the generated waves are described. The wave length and wave velocity are obtained as functions on azimuth of wave propagation and growth rate. Motionless waves dynamically trapped into the general picture of three dimensional waves are described. The gravitation force does not enter the three dimensional of turbulent wind waves. That is why these waves have turbulent and not gravitational nature. The Langmuir stripes are naturally modeled and existence of the rogue waves is theoretically proved.

  11. Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

    Science.gov (United States)

    Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

    2012-01-01

    We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

  12. Wind Tunnel Modeling Of Wind Flow Over Complex Terrain

    Science.gov (United States)

    Banks, D.; Cochran, B.

    2010-12-01

    , vortex shedding, and local turbulence intensity and wind shear values. To achieve accurate results, attention must of course be paid to issues such as ensuring Reynolds number independence, avoiding blockage issues, and properly matching the velocity power spectrum, but once this is done, the laws of fluid mechanics take care of the rest. There will not be an overproduction of turbulent kinetic energy at the top of escarpments, or unacceptable dissipation of inlet turbulence levels. Modern atmospheric boundary layer wind tunnels are also often used to provide validation data for evaluating the performance of CFD model in complex flow environments. Present day computers have further increased the quality and quantity of data that can be economically obtained in a timely manner, for example through wind speed measurement using a computer controlled 3-D measurement positioning system Given this accuracy and widespread acceptance, it is perhaps surprising that ours was the only wind tunnel model in the Bolund blind experiment, an indication of how seldom physical modelling is used when estimating terrain effect for wind farms. In demonstrating how the Bolund test was modeled, this presentation will provide background on wind tunnel testing, including the governing scaling parameters. And we’ll see how our results compared to the full scale tests.

  13. Wind power development field test project under Japan Sea Museum program. Detailed wind characteristics survey; Nihonkai Museum koso ni okeru furyoku kaihatsu field test jigyo (fukyo seisa) hokokusho

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1999-11-01

    A detailed wind characteristics survey was conducted at Kaio-machi, Niiminato-shi, Toyama Prefecture, on the assumption that a wind power generation system would be constructed. The survey was a 1-year project from October 1998 through September 1999, and wind characteristics such as the average wind speed, average wind direction, standard deviation of wind velocity, and the maximum instantaneous wind speed were observed. The observation point was fixed at 20m above ground, the minimum time unit for observation was 10 minutes, and the 10-minute average value was defined as the measured value. For the maximum instantaneous wind speed, the minimum time unit for observation was set to be 2 seconds. The yearly average wind speed was 3.7m/s and the maximum wind speed in the period was 26m/s. Winds came prevalently from SW (17.5%), and then from WSW (11.4%) and NNE (10.2%). The wind axis was in the NE-SW direction with a total wind direction occurrence rate of 62.0%. Turbulence intensity was 0.15 at wind speed 2.0m/s or more and 0.14 at wind speed 4.0m/s or more. Estimated wind turbine yearly operating factors of 32-79% were obtained using rated values of a 150kW, 300kW, and 750kW-class wind turbines. (NEDO)

  14. Measuring and modelling of the wind on the scale of tall wind turbines

    DEFF Research Database (Denmark)

    Floors, Rogier Ralph

    and the friction velocity had a bias, which were related to the change in surface roughness. A higher-order boundary-layer scheme represented the wind profile of the westerly flow over sea better, while a first-order scheme modelled the flow from the east with low-level jets better. The wind profile shape...... to baroclinity. The variation of the resistance law constants in neutral, baroclinic conditions was approximately the same as in experiments that where assumed to be barotropic; part of the variation was explained by baroclinity showing the importance of including this effect when studying boundary-layer winds....

  15. Investigation of wind behaviour around high-rise buildings

    Science.gov (United States)

    Mat Isa, Norasikin; Fitriah Nasir, Nurul; Sadikin, Azmahani; Ariff Hairul Bahara, Jamil

    2017-09-01

    A study on the investigation of wind behaviour around the high-rise buildings is done through an experiment using a wind tunnel and computational fluid dynamics. High-rise buildings refer to buildings or structures that have more than 12 floors. Wind is invisible to the naked eye; thus, it is hard to see and analyse its flow around and over buildings without the use of proper methods, such as the use of wind tunnel and computational fluid dynamics software.The study was conducted on buildings located in Presint 4, Putrajaya, Malaysia which is the Ministry of Rural and Regional Development, Ministry of Information Communications and Culture, Ministry of Urban Wellbeing, Housing and Local Government and the Ministry of Women, Family, and Community by making scaled models of the buildings. The parameters in which this study is conducted on are, four different wind velocities used based on the seasonal monsoons, and wind direction. ANSYS Fluent workbench software is used to compute the simulations in order to achieve the objectives of this study. The data from the computational fluid dynamics are validated with the experiment done through the wind tunnel. From the results obtained through the use of the computation fluid dynamics, this study can identify the characteristics of wind around buildings, including boundary layer of the buildings, separation flow, wake region and etc. Then analyses is conducted on the occurance resulting from the wind that passes the buildings based on the velocity difference between before and after the wind passes the buildings.

  16. Influence of wind loading

    OpenAIRE

    MAVLONOV RAVSHANBEK ABDUJABBOROVICH; VAKKASOV KHAYRULLO SAYFULLAHANOVICH

    2015-01-01

    Each wind load is determined by a probabilistic-statistical method based on the concept of “equivalent static wind load”, on the assumption that structural frames and components/cladding behave elastically in strong wind.

  17. Tower Winds - Cape Kennedy

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Digitized data taken from Wind Gust Charts. Record contains hourly wind directions and speed with a peak wind recorded at the end of each day. Sorted by: station,...

  18. Wind energy program overview

    International Nuclear Information System (INIS)

    1992-02-01

    This overview emphasizes the amount of electric power that could be provided by wind power rather than traditional fossil fuels. New wind power markets, advances in technology, technology transfer, and wind resources are some topics covered in this publication

  19. Non-radial solar wind flows and IMF B z during 1973-2003

    Science.gov (United States)

    Pereira, Felix B.; Girish, T. E.

    2009-03-01

    The characteristics of latitudinal angles of solar wind flow ( θv) observed near earth have been studied during the period 1973-2003. The average magnitude of θv shows distinct enhancements during the declining and maximum phases of the sunspot cycles. A close association of B z component of IMF in the GSE system and the orientation of meridional flows in the solar wind is found which depends on the IMF sector polarity. This effect has been studied in typical geomagnetic storm periods. The occurrence of non-radial flows is also found to exhibit heliolatitudinal dependence during the years 1975 and 1985 as a characteristic feature of non-radial solar wind expansion from polar coronal holes.

  20. Quasi-Biennial Oscillation signatures in the diurnal tidal winds over Cachoeira Paulista

    Science.gov (United States)

    Rodrigues de Araujo, Luciana; Jacobi, Christoph; Batista, Paulo; Lima, Lourivaldo

    2016-07-01

    The solar diurnal tidal plays an important role in the Mesosphere and Lower Thermosphere (MLT) region at low latitudes, in which its amplitude for horizontal winds maximizes around 20 degrees. The tides are excited in the lower atmosphere and stratosphere and can be affected by short and long-term local variations during their upward propagation. In this work, the meteor winds obtained over Cachoeira Paulista (22.7° S, 45.0° W), Brazil, have been used to investigate interannual variability in the amplitude of the diurnal tidal winds. The monthly diurnal tidal displays year to year variations. Amplitudes are strongest when the equatorial quasi-biennial oscillation (QBO) at the 30 mb level is eastward. This behavior can be observed in all seasons in the meridional component, whilst it is more clearly expressed during austral autumn in the zonal component, just when the diurnal tidal is strongest at this latitude.

  1. Influence on surfers wind conditions east of the new Hanstholm harbour/wind turbine project

    DEFF Research Database (Denmark)

    Larsen, Torben J.; Astrup, Poul

    on the lee side, which is an important area for wind and kite surfers. In this study, both changes in mean wind velocities as well as the turbulence level are investigated for the surf area between a location called ”Fish Factory” to the location called ”Hamburg”. The interesting wind speed interval is 8-16m/s...... mainly from west, measured in 10m height. Results are extracted in several downstream locations specified by Grontmij covering the area used for surfing. It is expected that surfing mainly occurs for wind speeds above 10m/s (10m height) and the important parameters both level of mean wind speeds as well...

  2. Modelling Wind for Wind Farm Layout Optimization Using Joint Distribution of Wind Speed and Wind Direction

    OpenAIRE

    Ju Feng; Wen Zhong Shen

    2015-01-01

    Reliable wind modelling is of crucial importance for wind farm development. The common practice of using sector-wise Weibull distributions has been found inappropriate for wind farm layout optimization. In this study, we propose a simple and easily implementable method to construct joint distributions of wind speed and wind direction, which is based on the parameters of sector-wise Weibull distributions and interpolations between direction sectors. It is applied to the wind measurement data a...

  3. Denmark Wind Energy Programme

    DEFF Research Database (Denmark)

    Shen, Wen Zhong

    2014-01-01

    In this paper, a summary of some ongoing wind energy projects in Denmark is given. The research topics comprise computational model development, wind turbine design, low noise airfoil and blade design, control device development, wake modelling, and wind farm layout optimization.......In this paper, a summary of some ongoing wind energy projects in Denmark is given. The research topics comprise computational model development, wind turbine design, low noise airfoil and blade design, control device development, wake modelling, and wind farm layout optimization....

  4. Superconducting Wind Turbine Generators

    OpenAIRE

    Yunying Pan; Danhzen Gu

    2016-01-01

    Wind energy is well known as a renewable energy because its clean and less polluted characteristic, which is the foundation of development modern wind electricity. To find more efficient wind turbine is the focus of scientists around the world. Compared from conventional wind turbines, superconducting wind turbine generators have advantages at zero resistance, smaller size and lighter weight. Superconducting wind turbine will inevitably become the main trends in this area. This paper intends ...

  5. Introduction to vector velocity imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov

    it virtually impossible to compensate for the factor and obtain correct velocity estimates for either CFM or spectral velocity estimation. This talk will describe methods for finding the correct velocity by estimating both the axial and lateral component of the velocity vector. The transverse oscillation...... method introduces an ultrasound field that oscillation not only along the ultrasound beam both also transverse to it to estimate both the lateral and axial velocity for the full velocity vector. The correct velocity magnitude can be found from this as well as the instantaneous angle. This can be obtained...... over the full region of interest and a real time image at a frame rate of 20 Hz can be displayed. Real time videos have been obtained from both our research systems and from commercial BK Medical scanners. The vector velocity images reveal the full complexity of the human blood flow. It is easy to see...

  6. Analysis of turbulent wake behind a wind turbine

    DEFF Research Database (Denmark)

    Kermani, Nasrin Arjomand; Andersen, Søren Juhl; Sørensen, Jens Nørkær

    2013-01-01

    The aim of this study is to improve the classical analytical model for estimation of the rate of wake expansion and the decay of wake velocity deficit in the far wake region behind a wind turbine. The relations for a fully turbulent axisymmetric far wake were derived by applying the mass and mome......The aim of this study is to improve the classical analytical model for estimation of the rate of wake expansion and the decay of wake velocity deficit in the far wake region behind a wind turbine. The relations for a fully turbulent axisymmetric far wake were derived by applying the mass...... ambient wind velocities (higher thrust coefficients), this trend may be improved due to the faster recovery of the wake and therefore closer values to the theoretical approach may be obtained. In addition, the assumption of self-similarity behavior of the mean velocity profile, when scaled with center...

  7. Wind turbines, is it just wind?

    International Nuclear Information System (INIS)

    Boiteux, M.

    2012-01-01

    The author first outlines that wind energy is not only random, but almost absent in extreme situations when it would be needed (for example and notably, very cold weather without wind). He suggests the association of a gas turbine to each wind turbine, so that the gas turbine will replace non operating wind turbines. He notices that wind turbines are not proximity energy as they were said to be, and that profitability in fact requires tens of grouped giant wind turbines. He also outlines the high cost of construction of grids for the connection of these wind turbines. Thus, he states that wind energy is far from being profitable in the present conditions of electricity tariffs in France

  8. Cluster Analysis of the Wind Events and Seasonal Wind Circulation Patterns in the Mexico City Region

    Directory of Open Access Journals (Sweden)

    Susana Carreón-Sierra

    2015-07-01

    Full Text Available The residents of Mexico City face serious problems of air pollution. Identifying the most representative scenarios for the transport and dispersion of air pollutants requires the knowledge of the main wind circulation patterns. In this paper, a simple method to recognize and characterize the wind circulation patterns in a given region is proposed and applied to the Mexico City winds (2001–2006. This method uses a lattice wind approach to model the local wind events at the meso-β scale, and hierarchical cluster analysis to recognize their agglomerations in their phase space. Data of the meteorological network of Mexico City was used as input for the lattice wind model. The Ward’s clustering algorithm with Euclidean distance was applied to organize the model wind events in seasonal clusters for each year of the period. Comparison of the hourly population trends of these clusters permitted the recognition and detailed description of seven circulation patterns. These patterns resemble the qualitative descriptions of the Mexico City wind circulation modes reported by other authors. Our method, however, permitted also their quantitative characterization in terms of the wind attributes of velocity, divergence and vorticity, and an estimation of their seasonal and annual occurrence probabilities, which never before were quantified.

  9. Numerical simulations of flow fields through conventionally controlled wind turbines and wind farms

    International Nuclear Information System (INIS)

    Yilmaz, Ali Emre; Meyers, Johan

    2014-01-01

    In the current study, an Actuator-Line Model (ALM) is implemented in our in-house pseudo-spectral LES solver SP-WIND, including a turbine controller. Below rated wind speed, turbines are controlled by a standard-torque-controller aiming at maximum power extraction from the wind. Above rated wind speed, the extracted power is limited by a blade pitch controller which is based on a proportional-integral type control algorithm. This model is used to perform a series of single turbine and wind farm simulations using the NREL 5MW turbine. First of all, we focus on below-rated wind speed, and investigate the effect of the farm layout on the controller calibration curves. These calibration curves are expressed in terms of nondimensional torque and rotational speed, using the mean turbine-disk velocity as reference. We show that this normalization leads to calibration curves that are independent of wind speed, but the calibration curves do depend on the farm layout, in particular for tightly spaced farms. Compared to turbines in a lone-standing set-up, turbines in a farm experience a different wind distribution over the rotor due to the farm boundary-layer interaction. We demonstrate this for fully developed wind-farm boundary layers with aligned turbine arrangements at different spacings (5D, 7D, 9D). Further we also compare calibration curves obtained from full farm simulations with calibration curves that can be obtained at a much lower cost using a minimal flow unit

  10. Field investigation of a wake structure downwind of a VANT (Vertical-Axis Wind Turbine) in a wind farm array

    Science.gov (United States)

    Liu, H. T.; Buck, J. W.; Germain, A. C.; Hinchee, M. E.; Solt, T. S.; Leroy, G. M.; Srnsky, R. A.

    1988-09-01

    The effects of upwind turbine wakes on the performance of a FloWind 17-m vertical-axis wind turbine (VAWT) were investigated through a series of field experiments conducted at the FloWind wind farm on Cameron Ridge, Tehachapi, California. From the field measurements, we derived the velocity and power/energy deficits under various turbine on/off configurations. Much information was provided to characterize the structure of VAWT wakes and to assess their effects on the performance of downwind turbines. A method to estimate the energy deficit was developed based on the measured power deficit and the wind speed distributions. This method may be adopted for other turbine types and sites. Recommendations are made for optimizing wind farm design and operations, as well as for wind energy management.

  11. Advanced structural wind engineering

    CERN Document Server

    Kareem, Ahsan

    2013-01-01

    This book serves as a textbook for advanced courses as it introduces state-of-the-art information and the latest research results on diverse problems in the structural wind engineering field. The topics include wind climates, design wind speed estimation, bluff body aerodynamics and applications, wind-induced building responses, wind, gust factor approach, wind loads on components and cladding, debris impacts, wind loading codes and standards, computational tools and computational fluid dynamics techniques, habitability to building vibrations, damping in buildings, and suppression of wind-induced vibrations. Graduate students and expert engineers will find the book especially interesting and relevant to their research and work.

  12. Wind for Schools (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Baring-Gould, I.

    2010-05-01

    As the United States dramatically expands wind energy deployment, the industry is challenged with developing a skilled workforce and addressing public resistance. Wind Powering America's Wind for Schools project addresses these issues by developing Wind Application Centers (WACs) at universities; WAC students assist in implementing school wind turbines and participate in wind courses, by installing small wind turbines at community "host" schools, by implementing teacher training with interactive curricula at each host school. This poster provides an overview of the first two years of the Wind for Schools project, primarily supporting activities in Colorado, Kansas, Nebraska, South Dakota, Montana, and Idaho.

  13. Simultaneous measurements of the thermospheric wind profile at three separate positions in the dusk auroral oval

    International Nuclear Information System (INIS)

    Mikkelsen, I.S.; Friis-Christensen, E.; Larsen, M.F.; Kelley, M.C.; Vickrey, J.; Meriwether, J.; Shih, P.

    1987-01-01

    On March 20, 1985, two rockets were launched from Soendre Stroemfjord, Greenland, into the dusk auroral oval. Three trimethyl aluminium trails were released to measure the neutral wind profiles between 95 and 190 km of altitude at two points separated by 190 km normal to the invariant latitude circles and at a third point separated from the first two by 300 km along the invariant latitude circles. Two barium/strontium clouds were released at 250 km of altitude, extending two of the neutral wind profiles to this altitude. In the E region the tip of the wind vector traced an ellipse as a function of increasing altitude with maximum wind speeds of 100-150 m/s in the southeastward and northwestward directions. The F region winds were southward with speeds of 100-200 m/s. The zonal wind component between 115 and 140 km of altitude had a horizontal gradient in the southeastward direction, whereas the meridional wind component at the same heights was constant over the spatial extent covered by the measurements. The authors interpret the observed E region wind field as being part of a gravity wave with a period of 3 hours as estimated from the ellipticity of the wind hodograms. The wind vectors rotated 540 degree clockwise with increasing height, indicating that the wave energy is propagating upward. The Fabry-Perot interferometer at Soendre Stroemfjord was first able to detect the F region winds 45 min after the releases and measured winds of 100-400 m/s mainly in the southeastward or antisunward direction. The geomagnetic conditions were quiet, with Kp not exceeding 2 for the 24 hours preceding the experiment. The incoherent scatter radar at Soendre Stroemfjord observed a contracted plasma convection pattern associated with positive B y and B z components of the interplanetary magnetic field

  14. The Portuguese man-of-war: Gone with the wind

    DEFF Research Database (Denmark)

    Ferrer, Luis; Pastor Rollan, Ane

    2017-01-01

    The Portuguese man-of-war (Physalia physalis) is a siphonophore that lives at the air–water interface of the sea. The wind is the main mechanism controlling its drift. In August 2010, a significant number of individuals of this species arrived at the Basque coast (southeastern Bay of Biscay......), causing a great socio-economic impact. Here we investigate the most likely region of origin and routes of these individuals using the Sediment, Oil spill and Fish Tracking model (SOFT). This model was run backwards in time using only the wind drag velocity (i.e., the wind velocity multiplied by a wind...... drag coefficient) to estimate the drift of these Portuguese man-of-war for one year and taking into account that the final destination was the Basque coast. The wind data were obtained with the Weather Research and Forecasting model (WRF). Six different simulations were carried out with SOFT using...

  15. Tidal wind oscillations in the tropical lower atmosphere as observed by Indian MST Radar

    Directory of Open Access Journals (Sweden)

    M. N. Sasi

    2001-08-01

    Full Text Available Diurnal tidal components in horizontal winds measured by MST radar in the troposphere and lower stratosphere over a tropical station Gadanki (13.5° N, 79.2° E are presented for the autumn equinox, winter, vernal equinox and summer seasons. For this purpose radar data obtained over many diurnal cycles from September 1995 to August 1996 are used. The results obtained show that although the seasonal variation of the diurnal tidal amplitudes in zonal and meridional winds is not strong, vertical phase propagation characteristics show significant seasonal variation. An attempt is made to simulate the diurnal tidal amplitudes and phases in the lower atmosphere over Gadanki using classical tidal theory by incorporating diurnal heat sources, namely, solar radiation absorption by water vapour, planetary boundary layer (PBL heat flux, latent heat release in deep convective clouds and short wave solar radiation absorption by clouds. A comparison of the simulated amplitudes and phases with the observed ones shows that agreement between the two is quite good for the equinox seasons, especially the vertical structure of the phases of the meridional wind components.Key words. Meteorology and atmospheric dynamics (tropical meteorology; waves and tides

  16. Tidal wind oscillations in the tropical lower atmosphere as observed by Indian MST Radar

    Directory of Open Access Journals (Sweden)

    M. N. Sasi

    Full Text Available Diurnal tidal components in horizontal winds measured by MST radar in the troposphere and lower stratosphere over a tropical station Gadanki (13.5° N, 79.2° E are presented for the autumn equinox, winter, vernal equinox and summer seasons. For this purpose radar data obtained over many diurnal cycles from September 1995 to August 1996 are used. The results obtained show that although the seasonal variation of the diurnal tidal amplitudes in zonal and meridional winds is not strong, vertical phase propagation characteristics show significant seasonal variation. An attempt is made to simulate the diurnal tidal amplitudes and phases in the lower atmosphere over Gadanki using classical tidal theory by incorporating diurnal heat sources, namely, solar radiation absorption by water vapour, planetary boundary layer (PBL heat flux, latent heat release in deep convective clouds and short wave solar radiation absorption by clouds. A comparison of the simulated amplitudes and phases with the observed ones shows that agreement between the two is quite good for the equinox seasons, especially the vertical structure of the phases of the meridional wind components.

    Key words. Meteorology and atmospheric dynamics (tropical meteorology; waves and tides

  17. Load attenuating passively adaptive wind turbine blade

    Science.gov (United States)

    Veers, Paul S.; Lobitz, Donald W.

    2003-01-07

    A method and apparatus for improving wind turbine performance by alleviating loads and controlling the rotor. The invention employs the use of a passively adaptive blade that senses the wind velocity or rotational speed, and accordingly modifies its aerodynamic configuration. The invention exploits the load mitigation prospects of a blade that twists toward feather as it bends. The invention includes passively adaptive wind turbine rotors or blades with currently preferred power control features. The apparatus is a composite fiber horizontal axis wind-turbine blade, in which a substantial majority of fibers in the blade skin are inclined at angles of between 15 and 30 degrees to the axis of the blade, to produces passive adaptive aeroelastic tailoring (bend-twist coupling) to alleviate loading without unduly jeopardizing performance.

  18. Forecasting winds over nuclear power plants statistics

    International Nuclear Information System (INIS)

    Marais, Ch.

    1997-01-01

    In the event of an accident at nuclear power plant, it is essential to forecast the wind velocity at the level where the efflux occurs (about 100 m). At present meteorologists refine the wind forecast from the coarse grid of numerical weather prediction (NWP) models. The purpose of this study is to improve the forecasts by developing a statistical adaptation method which corrects the NWP forecasts by using statistical comparisons between wind forecasts and observations. The Multiple Linear Regression method is used here to forecast the 100 m wind at 12 and 24 hours range for three Electricite de France (EDF) sites. It turns out that this approach gives better forecasts than the NWP model alone and is worthy of operational use. (author)

  19. Financial analysis of wind power projects

    International Nuclear Information System (INIS)

    Juanico, Luis E.; Bergallo, Juan E.

    1999-01-01

    In this work a financial assessment of the economic competitiveness of wind power projects in Argentina compared with other no CO 2 emission sources, such as nuclear, was developed. Argentina has a market driven electrical grid system, and no greenhouse gas emissions penalty taxes, together with a very low natural gas cost and a sustained nuclear development program. For the financial analysis an average wind velocity source of 8 m/s, on several wind farms (from 2 machines to 60) built with new technology wind generators (750 kilowatts power, 900 dollar/kilowatt cost) operating over 20 years, was considered. The leveled cost obtained is decreasing while the number of machines is increasing, from 0,130 dollar/kilowatt-hour to 0,090 dollar/kilowatts-hour. This poor performance can be partially explained considering the higher interest rates in the argentine financial market (15%) than the ones in developed countries

  20. Wake flow characteristics at high wind speed

    DEFF Research Database (Denmark)

    Aagaard Madsen, Helge; Larsen, Torben J.; Larsen, Gunner Chr.

    2016-01-01

    Wake flow characteristic at high wind speeds is the main subject of this paper. Although the wake losses decrease at high wind speeds it has been found in a recent study that for multiple wake inflow the increase in loading due to wake effects are substantial even at wind speeds well above rated...... power. In the present study we simulate the wake flow for a row of turbines with the wind aligned with the row using a simplified approach. The velocity deficit, being a function of the thrust coefficient, is simulated based on the BEM solution for wake expansion. An axis-symmetric boundary layer...... equation model (the same as implemented in the DWM model) is subsequently used to develop the deficit down to the next turbine, and then the approach is successively repeated. Simulation results for four different spacing’s in a row with eight turbines show that there are two major flow regimes...

  1. Examples of Vector Velocity Imaging

    DEFF Research Database (Denmark)

    Hansen, Peter M.; Pedersen, Mads M.; Hansen, Kristoffer L.

    2011-01-01

    To measure blood flow velocity in vessels with conventional ultrasound, the velocity is estimated along the direction of the emitted ultrasound wave. It is therefore impossible to obtain accurate information on blood flow velocity and direction, when the angle between blood flow and ultrasound wa...

  2. E region neutral winds in the postmidnight diffuse aurora during the atmospheric response in aurora 1 rocket campaign

    International Nuclear Information System (INIS)

    Brinkman, D.G.; Walterscheid, R.L.; Lyons, L.R.

    1995-01-01

    Measured E region neutral winds from the Atmospheric Response in Aurora (ARIA 1) rocket campaign are compared with winds predicted by a high-resolution nonhydrostatic dynamical thermosphere model. The ARIA 1 rockets were launched into the postmidnight diffuse aurora during the recovery phase of a substorm. Simulations have shown that electrodynamical coupling between the auroral ionosphere and the thermosphere was expected to be strong during active diffuse auroral conditions. This is the first time that simulations using the time history of detailed specifications of the magnitude and latitudinal variation of the auroral forcing based on measurements have been compared to simultaneous wind measurements. Model inputs included electron densities derived from ground-based airglow measurements, precipitating electron fluxes measured by the rocket, electron densities measured on the rocket, electric fields derived from magnetometer and satellite ion drift measurements, and large-scale background winds from a thermospheric general circulation model. Our model predicted a strong jet of eastward winds at E region heights. A comparison between model predicted and observed winds showed modest agreement. Above 135 km the model predicted zonal winds with the correct sense, the correct profile shape, and the correct altitude of the peak wind. However, it overpredicted the magnitude of the eastward winds by more than a factor or 2. For the meridional winds the model predicted the general sense of the winds but was unable to predict the structure or strength of the winds seen in the observations. Uncertainties in the magnitude and latitudinal structure of the electric field and in the magnitude of the background winds are the most likely sources of error contributing to the differences between model and observed winds. Between 110 and 135 km the agreement between the model and observations was poor because of a large unmodeled jetlike feature in the observed winds

  3. Wind loads on flat plate photovoltaic array fields

    Science.gov (United States)

    Miller, R. D.; Zimmerman, D. K.

    1981-01-01

    The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads. The arrays located at the outer boundary of an array field have a protective influence on the interior arrays of the field. A significant decrease of the array wind loads were recorded in the wind tunnel test on array panels located behind a fence and/or interior to the array field compared to the arrays on the boundary and unprotected from the wind. The magnitude of this decrease was the same whether caused by a fence or upwind arrays.

  4. Estimating wind frequency limits for natural ventilation at remote sites

    International Nuclear Information System (INIS)

    Su, B.; Aynsley, R.

    2006-01-01

    Detailed wind data are collected at a limited number of sites, usually at airports. When a building is sited remote from the nearest wind data collection site, estimating wind frequency is more complex. The techniques involved come from the discipline of wind engineering. Where there is a relatively flat terrain between the wind data-recording site and the building site, simple computations can be made to account for the wind velocities over intervening terrain roughness. Where significant topographic features such as hills or mountains are present between the wind data-recording site and the building site, then boundary layer wind tunnel studies will be necessary to determine the influence of such features on wind speed and direction. Rough estimates can be calculated using factors used in some wind loading codes. When buildings are to be designed to take advantage of the energy efficiency offered by natural ventilation, it is important to estimate the actual potential for such ventilation. The natural ventilation potential can be estimated in terms of the percentage of time when wind exceeds some minimum value. For buildings near airports this is a relatively simple procedure. Such estimates are important as they also indicate the likely percentage of time when fans or other energy consuming devices will be needed to maintain indoor thermal comfort. This paper identifies the wind engineering techniques that can be used for such estimates and gives examples of such calculations

  5. Effects of Southern Hemispheric Wind Changes on Global Oxygen and the Pacific Oxygen Minimum Zone

    Science.gov (United States)

    Getzlaff, J.; Dietze, H.; Oschlies, A.

    2016-02-01

    We use a coupled ocean biogeochemistry-circulation model to compare the impact of changes in southern hemispheric winds with that of warming induced buoyancy fluxes on dissolved oxygen. Changes in the southern hemispheric wind fields, which are in line with an observed shift of the southern annual mode, are a combination of a strengthening and poleward shift of the southern westerlies. We differentiate between effects caused by a strengthening of the westerlies and effects of a southward shift of the westerlies that is accompanied by a poleward expansion of the tropical trade winds. Our results confirm that the Southern Ocean plays an important role for the marine oxygen supply: a strengthening of the southern westerlies, that leads to an increase of the water formation rates of the oxygen rich deep and intermediate water masses, can counteract part of the warming-induced decline in marine oxygen levels. The wind driven intensification of the Southern Ocean meridional overturning circulation drives an increase of the global oxygen supply. Furthermore the results show that the shift of the boundary between westerlies and trades results in an increase of subantarctic mode water and an anti-correlated decrease of deep water formation and reduces the oceanic oxygen supply. In addition we find that the increased meridional extension of the southern trade winds, results in a strengthening and southward shift of the subtropical wind stress curl. This alters the subtropical gyre circulation (intensification and southward shift) and with it decreases the water mass transport into the oxygen minimum zone. In a business-as-usual CO2 emission scenario, the poleward shift of the trade-to-westerlies boundary is as important for the future evolution of the suboxic volume as direct warming-induced changes.

  6. [Influences of land using patterns on the anti-wind erosion of meadow grassland].

    Science.gov (United States)

    Zhou, Yao-Zhi; Wang-Xu; Yang, Gui-Xia; Xin, Xiao-Ping

    2008-05-01

    In order to analyse the effects of the human disturbances to the ability of anti-wind erosion of the Hulunbuir meadow grassland, the methods of vegetation investigation and the wind tunnel experiment were made to research the changes of vegetation and the abilities of anti-wind erosion of meadow grassland under different using patterns of meadow grassland. The results indicate that, under different grazing intensities of meadow grassland, the critical wind velocity of soil erosion (v) changes with the vegetation cover according to the relation of second power function. Along with the grazing intensities increasing and the vegetation cover reducing, the velocity of soil erosion rapidly increased on the condition of similar wind velocity which is speedier than the critical wind velocity of soil erosion. When the meadow grassland is mildly grazed which the vegetation cover maintains 63%, the velocity of soil erosion is small even there is gale that the wind velocity reach 25 m/s. When the vegetation cover of meadow grassland reduced to less than 35%, the velocity of soil erosion rapidly increased with the vegetation cover's reducing on the condition of the wind velocity is among 20-25 m/s. And owing to the no-tillage cropland of meadow grassland is completely far from the protection of the vegetation, the soil wind erosion quantity achieves 682.1 kg/hm2 in a minute when the wind velocity is 25 m/s, which approaches the average formation quantity of soil (1 000 kg/hm2) in a year.

  7. Northern Hemisphere stratospheric winds in higher midlatitudes: longitudinal distribution and long-term trends

    Czech Academy of Sciences Publication Activity Database

    Kozubek, Michal; Križan, Peter; Laštovička, Jan

    2015-01-01

    Roč. 15, Feb (2015), s. 2203-2213 ISSN 1680-7316 R&D Projects: GA ČR GAP209/10/1792; GA ČR GA15-03909S; GA MŠk LD12070 Institutional support: RVO:68378289 Keywords : stratospheric dynamics * meridional wind * long-term trend Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 5.114, year: 2015 http://www.atmos-chem-phys.net/15/2203/2015/acp-15-2203-2015.html

  8. Mean zonal and meridional accelerations and mean heating induced by solar tides for equinox and solstice conditions

    International Nuclear Information System (INIS)

    Groves, G.V.; Forbes, J.M.

    1985-01-01

    Evaluations are presented of the momentum and energy flux divergences of the diurnal and semidiurnal tidal fields calculated by Forbes from 0 to 400 km altitude. Results are presented in the form of meridional cross-sections from 0 to 78 0 N or S latitude with a 6 0 latitude interval. Comparisons are made with evaluations of the momentum flux divergences of the diurnal tide by Miyahara and good agreement is obtained in the lower thermosphere (below about 130 km) but a large disparity arises in the upper thermosphere. In the lower thermosphere momentum flux divergences of the semidiurnal tide are comparable with those of the diurnal tide and should be included in general circulation calculations of the 90-120 km region. (author)

  9. L'«Atles lingüístic del valencià meridional i alacantí» (ALVA

    Directory of Open Access Journals (Sweden)

    Josep Tormo Colomina

    2015-07-01

    Full Text Available This paper is the official presentation, since the project was first started in 1978, of the forthcoming «Atles Lingüístic del Valencià Meridional i Alacantí» (ALVA (Linguistic Atlas of Southern Valencian and Alacantí, which so far had not been explicitly publicized. This paper, divided in two sections, includes the background of the author, the birth of the Atlas, the original questionnaire and its evolution, the network of towns studied, the aims of the project, the research method, the present questionnaire, the findings beyond the questionnaire, the cartographic representation and a brief set of maps and comments showing the importance that microatles with a very specific questionnaire may have in reduced contexts in certain peripheral areas.

  10. Wind energy harvesting with a piezoelectric harvester

    International Nuclear Information System (INIS)

    Wu, Nan; Wang, Quan; Xie, Xiangdong

    2013-01-01

    An energy harvester comprising a cantilever attached to piezoelectric patches and a proof mass is developed for wind energy harvesting, from a cross wind-induced vibration of the cantilever, by the electromechanical coupling effect of piezoelectric materials. The vibration of the cantilever under the cross wind is induced by the air pressure owing to a vortex shedding phenomenon that occurs on the leeward side of the cantilever. To describe the energy harvesting process, a theoretical model considering the cross wind-induced vibration on the piezoelectric coupled cantilever energy harvester is developed, to calculate the charge and the voltage from the harvester. The influences of the length and location of the piezoelectric patches as well as the proof mass on the generated electric power are investigated. Results show that the total generated electric power can be as high as 2 W when the resonant frequency of the cantilever harvester is close to the vortex shedding frequency. Moreover, a value of total generated electric power up to 1.02 W can be practically realized for a cross wind with a variable wind velocity of 9–10 m s −1 by a harvester with a length of 1.2 m. This research facilitates an effective and compact wind energy harvesting device. (paper)

  11. Inter-comparison of stratospheric mean-meridional circulation and eddy mixing among six reanalysis data sets

    Directory of Open Access Journals (Sweden)

    K. Miyazaki

    2016-05-01

    Full Text Available The stratospheric mean-meridional circulation (MMC and eddy mixing are compared among six meteorological reanalysis data sets: NCEP-NCAR, NCEP-CFSR, ERA-40, ERA-Interim, JRA-25, and JRA-55 for the period 1979–2012. The reanalysis data sets produced using advanced systems (i.e., NCEP-CFSR, ERA-Interim, and JRA-55 generally reveal a weaker MMC in the Northern Hemisphere (NH compared with those produced using older systems (i.e., NCEP/NCAR, ERA-40, and JRA-25. The mean mixing strength differs largely among the data products. In the NH lower stratosphere, the contribution of planetary-scale mixing is larger in the new data sets than in the old data sets, whereas that of small-scale mixing is weaker in the new data sets. Conventional data assimilation techniques introduce analysis increments without maintaining physical balance, which may have caused an overly strong MMC and spurious small-scale eddies in the old data sets. At the NH mid-latitudes, only ERA-Interim reveals a weakening MMC trend in the deep branch of the Brewer–Dobson circulation (BDC. The relative importance of the eddy mixing compared with the mean-meridional transport in the subtropical lower stratosphere shows increasing trends in ERA-Interim and JRA-55; this together with the weakened MMC in the deep branch may imply an increasing age-of-air (AoA in the NH middle stratosphere in ERA-Interim. Overall, discrepancies between the different variables and trends therein as derived from the different reanalyses are still relatively large, suggesting that more investments in these products are needed in order to obtain a consolidated picture of observed changes in the BDC and the mechanisms that drive them.

  12. O HORST DA MANTIQUEIRA MERIDIONAL: PROPOSTA DE COMPARTIMENTAÇÃO MORFOESTRUTURAL PARA SUA PORÇÃO MINEIRA

    Directory of Open Access Journals (Sweden)

    Roberto Marques Neto

    2017-08-01

    Full Text Available A Mantiqueira Meridional perfaz o sistema orográfico contínuo mais elevado de todo o Brasil Oriental. Sua gênese está ligada à reativação tectônica que acometeu a Plataforma Brasileira entre o Cretáceo e o Paleógeno orquestrada pela separação da paleoplaca Afro-brasileira e processos geodinâmicos associados, com posteriores reativações vinculadas à dinâmica neotectônica intraplaca e outros efeitos diastróficos oriundos de tectônica ressurgente e ativa. Dessa forma, a compartimentação morfoestrutural da Serra da Mantiqueira integra uma série de feições passivas a um vasto rol de evidências de controle morfotectônico sobrepostos às estruturas preexistentes. O presente artigo consiste numa proposta de compartimentação morfoestrutural para a porção da Mantiqueira Meridional contida no estado de Minas Gerais, enfatizando o controle morfoestrutural, o papel dos níveis de base regionais, e as estruturas tectônicas ativas afetando os diferentes compartimentos discernidos. A análise integrada entre os litotipos, os lineamentos estruturais, a rede de drenagem e os padrões de formas de relevo discerniu os seguintes compartimentos morfoestruturais: Patamares de Cimeira da Mantiqueira (desmembrados em sete subcompartimentos, Patamares Escalonados da Mantiqueira (dois subcompartimentos, Cristas Quartzíticas Festonadas e Rebordos Erosivos Dissecados.

  13. Anywhere the Wind Blows does Really Matter

    Science.gov (United States)

    Montaldo, Nicola; Oren, Ram

    2014-05-01

    The variation of net ecosystem carbon exchange (NEE) has been explained at coarse scales with variation of forcing variables among climate regions and associated biomes, at the intermediate, mesoscale, with differences among dominating vegetation types and conditions, and at the misoscale with heterogeneity of the eddy covariance footprint properties. Wind is rarely considered in analysis of surface fluxes for its effects on periodic budgets of water and carbon. In many regions conditions change frequently between maritime and continental depending on wind velocity (VW) and direction. In these regions, water and carbon fluxes may respond to mesoscale weather patterns extending maritime influences far inland. Using eddy-covariance data from Sardinia, we show that daytime net carbon exchange (NEE) of a mixed pasture-woodland (grass-wild olive) ecosystem (Detto et al., 2006; Montaldo et al., 2008) increased with VW, especially during summer-dry conditions. As VW increased, the air, humidified over sea, remains relatively moist and cool to a greater distance inland, reaching only ~50 km during slow Saharan Sirocco wind but >160 km during mostly Mistral wind (4 m/s) from Continental Europe. A 30% lower vapor pressure deficit (D) associated with high VW (average 2 kPa at 4 m/s), allowed a 50% higher canopy stomatal conductance (gc) and, thus, photosynthesis. However, because gc and D have opposite effects on evapotranspiration (Ee), Ee was unaffected by VW. Thus, higher NEE during summertime Mistral reflects increased ecosystem water-use efficiency (We) and a departure from a costly carbon-water tradeoff. Yet many regions often experience high velocity winds, attention is typically focused on the capacity of strong winds to fan regional fires, threatening human habitation and natural habitats, and reducing Carbon storage (C), NEE and latent heat flux. However, depending on their origin, high velocity winds can bring continental air to the coast (e.g., Santa Ana winds

  14. Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

    Science.gov (United States)

    Hildebrand, Jens; Baumgarten, Gerd; Fiedler, Jens; Lübken, Franz-Josef

    2017-11-01

    We present an extensive data set of simultaneous temperature and wind measurements in the Arctic middle atmosphere. It consists of more than 300 h of Doppler Rayleigh lidar observations obtained during three January seasons (2012, 2014, and 2015) and covers the altitude range from 30 km up to about 85 km. The data set reveals large year-to-year variations in monthly mean temperatures and winds, which in 2012 are affected by a sudden stratospheric warming. The temporal evolution of winds and temperatures after that warming are studied over a period of 2 weeks, showing an elevated stratopause and the reformation of the polar vortex. The monthly mean temperatures and winds are compared to data extracted from the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Horizontal Wind Model (HWM07). Lidar and ECMWF data show good agreement of mean zonal and meridional winds below ≈ 55 km altitude, but we also find mean temperature, zonal wind, and meridional wind differences of up to 20 K, 20 m s-1, and 5 m s-1, respectively. Differences between lidar observations and HWM07 data are up to 30 m s-1. From the fluctuations of temperatures and winds within single nights we extract the potential and kinetic gravity wave energy density (GWED) per unit mass. It shows that the kinetic GWED is typically 5 to 10 times larger than the potential GWED, the total GWED increases with altitude with a scale height of ≈ 16 km. Since temporal fluctuations of winds and temperatures are underestimated in ECMWF, the total GWED is underestimated as well by a factor of 3-10 above 50 km altitude. Similarly, we estimate the energy density per unit mass for large-scale waves (LWED) from the fluctuations of nightly mean temperatures and winds. The total LWED is roughly constant with altitude. The ratio of kinetic to potential LWED varies with altitude over 2 orders of magnitude. LWEDs from ECMWF data show results similar to the lidar data. From the

  15. Ekman Upwelling, METOP ASCAT, 0.25 degrees, Global, Near Real Time

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA CoastWatch distributes near real time Ekman current (in zonal, meridional, and modulus sets) and Ekman upwelling data. This data begins with wind velocity...

  16. Solar wind stream interfaces

    International Nuclear Information System (INIS)

    Gosling, J.T.; Asbridge, J.R.; Bame, S.J.; Feldman, W.C.

    1978-01-01

    Measurements aboard Imp 6, 7, and 8 reveal that approximately one third of all high-speed solar wind streams observed at 1 AU contain a sharp boundary (of thickness less than approx.4 x 10 4 km) near their leading edge, called a stream interface, which separates plasma of distinctly different properties and origins. Identified as discontinuities across which the density drops abruptly, the proton temperature increases abruptly, and the speed rises, stream interfaces are remarkably similar in character from one stream to the next. A superposed epoch analysis of plasma data has been performed for 23 discontinuous stream interfaces observed during the interval March 1971 through August 1974. Among the results of this analysis are the following: (1) a stream interface separates what was originally thick (i.e., dense) slow gas from what was originally thin (i.e., rare) fast gas; (2) the interface is the site of a discontinuous shear in the solar wind flow in a frame of reference corotating with the sun; (3) stream interfaces occur at speeds less than 450 km s - 1 and close to or at the maximum of the pressure ridge at the leading edges of high-speed streams; (4) a discontinuous rise by approx.40% in electron temperature occurs at the interface; and (5) discontinuous changes (usually rises) in alpha particle abundance and flow speed relative to the protons occur at the interface. Stream interfaces do not generally recur on successive solar rotations, even though the streams in which they are embedded often do. At distances beyond several astronomical units, stream interfaces should be bounded by forward-reverse shock pairs; three of four reverse shocks observed at 1 AU during 1971--1974 were preceded within approx.1 day by stream interfaces. Our observations suggest that many streams close to the sun are bounded on all sides by large radial velocity shears separating rapidly expanding plasma from more slowly expanding plasma

  17. Doppler lidar investigation of wind turbine wake characteristics and atmospheric turbulence under different surface roughness.

    Science.gov (United States)

    Zhai, Xiaochun; Wu, Songhua; Liu, Bingyi

    2017-06-12

    Four field experiments based on Pulsed Coherent Doppler Lidar with different surface roughness have been carried out in 2013-2015 to study the turbulent wind field in the vicinity of operating wind turbine in the onshore and offshore wind parks. The turbulence characteristics in ambient atmosphere and wake area was analyzed using transverse structure function based on Plane Position Indicator scanning mode. An automatic wake processing procedure was developed to determine the wake velocity deficit by considering the effect of ambient velocity disturbance and wake meandering with the mean wind direction. It is found that the turbine wake obviously enhances the atmospheric turbulence mixing, and the difference in the correlation of turbulence parameters under different surface roughness is significant. The dependence of wake parameters including the wake velocity deficit and wake length on wind velocity and turbulence intensity are analyzed and compared with other studies, which validates the empirical model and simulation of a turbine wake for various atmosphere conditions.

  18. Fatigue damage from random vibration pulse process of tubular structural elements subject to wind

    DEFF Research Database (Denmark)

    Christensen, Claus F.; Ditlevsen, Ove Dalager

    1997-01-01

    In a wide range of the Reynolds number an elastically suspended circular cylinder surrounded by a homogeneous wind velocity field will generate vortex shedding of a frequency that by and large is proportional to the far field wind velocity. However, if the cylinder is free to vibrate, resonance...... of turbulence observed in the natural wind the undisturbed local wind velocity directly upstream to the cylinder varies as a sample from a random process. Thus the local wind velocity will cross in and out of the "iock in"-intervals in a random fashion causing pulse like bursts of strong vibrations. The paper...... describes a random pulse process model of this vibration behavior supported on the experimental work of the first author. Moreover, it is shown how the mean accumulated material fatigue damage per time unit according to the Palmgren-Miner rule can be evaluated by simulation....

  19. Potential threat of southern Moravia soils by wind erosion

    Directory of Open Access Journals (Sweden)

    Jana Dufková

    2004-01-01

    Full Text Available Wind erosion is caused by meteorological factors such as wind, precipitation and evaporation that influence the soil humidity. Erosive-climatological factor expresses wind and humidity conditions of particular landscape. This is an index of the influence of average soil surface humidity and average wind velocity on average soil erodibility by wind. On the basis of average wind velocity and Konček’s humidity index, the values of the erosive-climatological factor for three chosen areas of Czech republic (Telč-Kostelní Myslová, Znojmo-Kuchařovice and Brno-Tuřany, where the pro-cesses of wind erosion could exist, were evaluated. Thus, the change of the factor’s value during the period of 1961 – 2000 was studied. The linear trend for the region of Brno and Znojmo (dry areas shows increasing threat of soils by wind erosion, the contrary situation is at the humid area (Telč. The results prove the influence of soil humidity on the erosive-climatological factor and hereby the influence on wind erosion spreadout.

  20. Low-frequency variability of meridional transport in the divergence zone of the North Atlantic subtropical and subpolar gyres. The WOCE section A2; Niederfrequente Variabilitaet meridionaler Transporte in der Divergenzzone des nordatlantischen Subtropen- und Subpolarwirbels. Der WOCE-Schnitt A2

    Energy Technology Data Exchange (ETDEWEB)

    Lorbacher, K.

    2000-07-01

    The subinertial, climate relevant variability of the large-scale ocean circulation in the northern North Atlantic and its integral key parameters such as the advective transports of mass (volume), heat and freshwater are determined from observations alone using the hydrographic data from seven realisations of the so-called '48 N'-section between the English Channel and the Grand Banks of Newfoundland. The data consist of five available sets of the WOCE/A2-section during the Nineties for the years 1993, 1994, 1996, 1997, 1998 and of two previous transatlantic cruises in April of 1957 and 1982. The realisations of the WOCE/A2-section were carried out in the same season (May to July), except for the cruise in October 1994. The '48 N'-section follows the divergence zone of the mainly wind-driven subtropical gyre and the more complex, with respect to the forcing, subpolar gyre. In the central Westeuropean and Newfoundland Basins the section runs a few degrees south of the line of zero wind stress curl (curl{sub z}{tau}). In the West, the WOCE/A2-section turns northwest to cross the boundary current regime perpendicularly. Therefore, this quasi-zonal hydrographic section covers all large-scale circulation elements on the regional scale that contribute essentially to the ocean circulation on the global scale - the Meridional Overturning Circulation (MOC). The transport estimates are given as the sum of the three transport components of a quasi-steady, large-scale ocean circulation: The ageostrophic Ekman-, and the two geostrophic components, the depth-independent, barotropic or Sverdrup- and the baroclinic component. To maintain the mass balance over the plane of the section the compensation of each component is assumed. In the case of the baroclinic component the balance is achieved through a suitable choice for a surface of 'no-motion'. The absolute meridional velocity as a function of the zonal distance along the section and depth is

  1. A canopy-type similarity model for wind farm optimization

    Science.gov (United States)

    Markfort, Corey D.; Zhang, Wei; Porté-Agel, Fernando

    2013-04-01

    The atmospheric boundary layer (ABL) flow through and over wind farms has been found to be similar to canopy-type flows, with characteristic flow development and shear penetration length scales (Markfort et al., 2012). Wind farms capture momentum from the ABL both at the leading edge and from above. We examine this further with an analytical canopy-type model. Within the flow development region, momentum is advected into the wind farm and wake turbulence draws excess momentum in from between turbines. This spatial heterogeneity of momentum within the wind farm is characterized by large dispersive momentum fluxes. Once the flow within the farm is developed, the area-averaged velocity profile exhibits a characteristic inflection point near the top of the wind farm, similar to that of canopy-type flows. The inflected velocity profile is associated with the presence of a dominant characteristic turbulence scale, which may be responsible for a significant portion of the vertical momentum flux. Prediction of this scale is useful for determining the amount of available power for harvesting. The new model is tested with results from wind tunnel experiments, which were conducted to characterize the turbulent flow in and above model wind farms in aligned and staggered configurations. The model is useful for representing wind farms in regional scale models, for the optimization of wind farms considering wind turbine spacing and layout configuration, and for assessing the impacts of upwind wind farms on nearby wind resources. Markfort CD, W Zhang and F Porté-Agel. 2012. Turbulent flow and scalar transport through and over aligned and staggered wind farms. Journal of Turbulence. 13(1) N33: 1-36. doi:10.1080/14685248.2012.709635.

  2. Wind engineering in Africa

    NARCIS (Netherlands)

    Wisse, J.A.; Stigter, C.J.

    2007-01-01

    The International Association for Wind Engineering (IAWE) has very few contacts in Africa, the second-largest continent. This paper reviews important wind-related African issues. They all require data on wind climate, which are very sparse in Africa. Wind engineering in Africa can assist in

  3. Wind energy; Energie eolienne

    Energy Technology Data Exchange (ETDEWEB)

    Vachey, C.

    2000-05-01

    This public information paper presents the wind energy resource in the Languedoc Roussillon region, explains how a wind turbine works, the different types of utilization and the cost of the wind energy. The environmental impacts of the wind energy, on the noise and the landscape, are also discussed. (A.L.B.)

  4. The Response of Western Boundary Currents to Intensifying Global Winds

    Science.gov (United States)

    Beal, L. M.; Elipot, S.

    2016-02-01

    Western boundary currents, such as the Agulhas Current, are the most intense meridional flows in the ocean, carrying heat away from the tropics and towards the poles. There is evidence that these current systems are shifting and/or intensifying under anthropogenic climate change, potentially exacerbating warming and extreme weather events in the mid-latitudes. We use new ocean measurements to show that since the early 1990s the Agulhas Current has not strengthened, despite an increase in sea surface temperature indicative of intensification. Rather, the current has been widening, which we attribute to increased eddy activity. Recent analyses of the Kuroshio and East Australia Current hint at similar trends. These results suggest that increased energy input by the winds may be increasing the instability of boundary currents, rather than intensifying their mean flow, with potential impacts on ocean mixing, ventilation, and shelf interactions. Sustained measurements are needed to properly understand the role of these current systems in future climate change.

  5. Offshore Wind Farms

    DEFF Research Database (Denmark)

    Lundtang Petersen, Erik; Hasager, Charlotte Bay; Courtney, Michael

    2015-01-01

    The technology behind constructing wind farms offshore began to develop in 1991 when the Vindeby wind farm was installed off the Danish coast (11 Bonus 450 kW turbines). Resource assessment, grid connection, and wind farm operation are significant challenges for offshore wind power just...... concern are the problems associated with locating the turbines close together in a wind farm and the problems of placing several large wind farms in a confined area. The environmental impacts of offshore wind farms are also treated, but not the supply chain, that is, the harbors, the installation vessels...

  6. The influence of solar active region evolution on solar wind streams, coronal hole boundaries and geomagnetic storms

    International Nuclear Information System (INIS)

    Gold, R.E.; Dodson-Prince, H.W.; Hedeman, E.R.; Roelof, E.C.

    1982-01-01

    We have studied solar and interplanetary data by identification of the heliographic longitudes of the coronal source regions of high speed solar wind streams and by mapping the velocities measured near earth back to the sun using the approximation of constant radial velocity. Interplay of active regions and solar wind were studied

  7. Laser Doppler detection systems for gas velocity measurement.

    Science.gov (United States)

    Huffaker, R M

    1970-05-01

    The velocity of gas flow has been remotely measured using a technique which involves the coherent detection of scattered laser radiation from small particles suspended in the fluid utilizing the doppler effect. Suitable instrumentation for the study of wind tunnel type and atmospheric flows are described. Mainly for reasons of spatial resolution, a function of the laser wavelength, the wind tunnel system utilizes an argon laser operating at 0.5 micro. The relaxed spatial resolution requirement of atmospheric applications allows the use of a carbon dioxide laser, which has superior performance at a wavelength of 10.6 micro, a deduction made from signal-to-noise ratio considerations. Theoretical design considerations are given which consider Mie scattering predictions, two-phase flow effects, photomixing fundamentals, laser selection, spatial resolution, and spectral broadening effects. Preliminary experimental investigations using the instrumentation are detailed. The velocity profile of the flow field generated by a 1.27-cm diam subsonic jet was investigated, and the result compared favorably with a hot wire investigation conducted in the same jet. Measurements of wind velocity at a range of 50 m have also shown the considerable promise of the atmospheric system.

  8. Fluorescence-Doped Particles for Simultaneous Temperature and Velocity Imaging

    Science.gov (United States)

    Danehy, Paul M.; Tiemsin, Pacita I.; Wohl, Chrostopher J.; Verkamp, Max; Lowe, T.; Maisto, P.; Byun, G.; Simpson, R.

    2012-01-01

    Polystyrene latex microspheres (PSLs) have been used for particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) measurements for several decades. With advances in laser technologies, instrumentation, and data processing, the capability to collect more information about fluid flow beyond velocity is possible using new seed materials. To provide additional measurement capability, PSLs were synthesized with temperature-sensitive fluorescent dyes incorporated within the particle. These multifunctional PSLs would have the greatest impact if they could be used in large scale facilities with minimal modification to the facilities or the existing instrumentation. Consequently, several potential dyes were identified that were amenable to existing laser systems currently utilized in wind tunnels at NASA Langley Research Center as well as other wind and fluid (water) tunnels. PSLs incorporated with Rhodamine B, dichlorofluorescein (DCF, also known as fluorescein 548 or fluorescein 27) and other dyes were synthesized and characterized for morphology and spectral properties. The resulting particles were demonstrated to exhibit fluorescent emission, which would enable determination of both fluid velocity and temperature. They also would allow near-wall velocity measurements whereas laser scatter from surfaces currently prevents near-wall measurements using undoped seed materials. Preliminary results in a wind tunnel facility located at Virginia Polytechnic Institute and State University (Virginia Tech) have verified fluorescent signal detection and temperature sensitivity of fluorophore-doped PSLs.

  9. Wind power. [electricity generation

    Science.gov (United States)

    Savino, J. M.

    1975-01-01

    A historical background on windmill use, the nature of wind, wind conversion system technology and requirements, the economics of wind power and comparisons with alternative systems, data needs, technology development needs, and an implementation plan for wind energy are presented. Considerable progress took place during the 1950's. Most of the modern windmills feature a wind turbine electricity generator located directly at the top of their rotor towers.

  10. Acceleration and heating of the solar wind

    Science.gov (United States)

    Barnes, A.

    1978-01-01

    Some of the competing theories of solar wind acceleration and heating are reviewed, and the observations that are required to distinguish among them are discussed. In most cases what is required is measurement of plasma velocity and temperature and magnetic field, as near the sun as possible and certainly inside 20 solar radii; another critical aspect of this question is determining whether a turbulent envelope exists in this inner region, and if so, defining its properties. Plasma and magnetic observations from the proposed Solar Probe mission would thus yield a quantum jump in our understanding of the dynamics of the solar wind.

  11. Mid-latitude thermospheric wind changes during the St. Patrick's Day storm of 2015 observed by two Fabry-Perot interferometers in China

    Science.gov (United States)

    Huang, Cong; Xu, Ji-Yao; Zhang, Xiao-Xin; Liu, Dan-Dan; Yuan, Wei; Jiang, Guo-Ying

    2018-04-01

    In this work, we utilize thermospheric wind observations by the Fabry-Perot interferometers (FPI) from the Kelan (KL) station (38.7°N, 111.6°E, Magnetic Latitude: 28.9°N) and the Xinglong (XL) station (40.2°N, 117.4°E, Magnetic Latitude: 30.5°N) in central China during the St. Patrick's Day storm (from Mar. 17 to Mar. 19) of 2015 to analyze thermospheric wind disturbances and compare observations with the Horizontal Wind Model 2007 (HWM07). The results reveal that the wind measurements at KL show very similar trends to those at XL. Large enhancements are seen in both the westward and equatorward winds after the severe geomagnetic storm occurred. The westward wind speed increased to a peak value of 75 m/s and the equatorward wind enhanced to a peak value of over 100 m/s. There also exist obvious poleward disturbances in the meridional winds during Mar. 17 to Mar. 19. According to the comparison with HWM07, there exist evident wind speed and temporal differences between FPI-winds and the model outputs in this severe geomagnetic storm. The discrepancies between the observations and HWM07 imply that the empirical model should be used carefully in wind disturbance forecast during large geomagnetic storms and more investigations between measurements and numerical models are necessary in future studies.

  12. Numerical Investigation of Wind Conditions for Roof-Mounted Wind Turbines: Effects of Wind Direction and Horizontal Aspect Ratio of a High-Rise Cuboid Building

    Directory of Open Access Journals (Sweden)

    Takaaki Kono

    2016-11-01

    Full Text Available From the viewpoint of installing small wind turbines (SWTs on rooftops, this study investigated the effects of wind direction and horizontal aspect ratio (HAR = width/length of a high-rise cuboid building on wind conditions above the roof by conducting large eddy simulations (LESs. The LES results confirmed that as HAR decreases (i.e., as the building width decreases, the variation in wind velocity over the roof tends to decrease. This tendency is more prominent as the angle between the wind direction and the normal vector of the building’s leeward face with longer roof edge increases. Moreover, at windward corners of the roof, wind conditions are generally favorable at relatively low heights. In contrast, at the midpoint of the roof's windward edge, wind conditions are generally not favorable at relatively low heights. At leeward representative locations of the roof, the bottoms of the height range of favorable wind conditions are typically higher than those at the windward representative locations, but the favorable wind conditions are much better at the leeward representative locations. When there is no prevailing wind direction, the center of the roof is more favorable for installing SWTs than the corners or the edge midpoints of the roof.

  13. Satellite based wind resource assessment over the South China Sea

    DEFF Research Database (Denmark)

    Badger, Merete; Astrup, Poul; Hasager, Charlotte Bay

    2014-01-01

    years of WRF data – specifically the parameters heat flux, air temperature, and friction velocity – are used to calculate a long-term correction for atmospheric stability effects. The stability correction is applied to the satellite based wind resource maps together with a vertical wind profile...... from satellite synthetic aperture radar (SAR) data are particularly suitable for offshore wind energy applications because they offer a spatial resolution up to 500 m and include coastal seas. In this presentation, satellite wind maps are used in combination with mast observations and numerical...... modeling to develop procedures and best practices for satellite based wind resource assessment offshore. All existing satellite images from the Envisat Advanced SAR sensor by the European Space Agency (2002-12) have been collected over a domain in the South China Sea. Wind speed is first retrieved from...

  14. Gravity effects on wind-induced flutter of leaves

    Science.gov (United States)

    Clemmer, Nickalaus; Kopperstad, Karsten; Solano, Tomas; Shoele, Kourosh; Ordonez, Juan

    2017-11-01

    Wind-Induced flutter of leaves depends on both wind velocity and the gravity. To study the gravitational effects on the oscillatory behavior of leaves in the wind, a wind tunnel that can be tilted about the center of the test section is created. This unique rotation capability allows systematic investigation of gravitational effects on the fluttering response of leaves. The flow-induced vibration will be studied for three different leaves at several different tilting angles including the wind travels horizontally, vertically downward and vertically upward. In each situation, the long axis of a leaf is placed parallel to the wind direction and its response is studied at different flow speed. Oscillation of the leaf is recorded via high-speed camera at each of setup, and the effect of the gravity on stabilizing or destabilizing the fluttering response is investigated. Summer REU student at Florida State University.

  15. Wind-farm simulation over moderately complex terrain

    Science.gov (United States)

    Segalini, Antonio; Castellani, Francesco

    2017-05-01

    A comparison between three independent software to estimate the power production and the flow field in a wind farm is conducted, validating them against SCADA (Supervisory, Control And Data Acquisition) data. The three software were ORFEUS, WindSim and WAsP: ORFEUS and WAsP are linearised solvers, while WindSim is fully nonlinear. A wake model (namely a prescribed velocity deficit associated to the turbines) is used by WAsP, while ORFEUS and WindSim use the actuator-disc method to account for the turbines presence. The comparison indicates that ORFEUS and WAsP perform slightly better than WindSim in the assessment of the polar efficiency. The wakes simulated with ORFEUS appear more persistent than the ones of WindSim, which uses a two-equation closure model for the turbulence effects.

  16. Control rod velocity limiter

    International Nuclear Information System (INIS)

    Cearley, J.E.; Carruth, J.C.; Dixon, R.C.; Spencer, S.S.; Zuloaga, J.A. Jr.

    1986-01-01

    This patent describes a velocity control arrangement for a reciprocable, vertically oriented control rod for use in a nuclear reactor in a fluid medium, the control rod including a drive hub secured to and extending from one end therefrom. The control device comprises: a toroidally shaped control member spaced from and coaxially positioned around the hub and secured thereto by a plurality of spaced radial webs thereby providing an annular passage for fluid intermediate the hub and the toroidal member spaced therefrom in coaxial position. The side of the control member toward the control rod has a smooth generally conical surface. The side of the control member away from the control rod is formed with a concave surface constituting a single annular groove. The device also comprises inner and outer annular vanes radially spaced from one another and spaced from the side of the control member away from the control rod and positioned coaxially around and spaced from the hub and secured thereto by spaced radial webs thereby providing an annular passage for fluid intermediate the hub and the vanes. The vanes are angled toward the control member, the outer edge of the inner vane being closer to the control member and the inner edge of the outer vane being closer to the control member. When the control rod moves in the fluid in the direction toward the drive hub the vanes direct a flow of fluid turbulence which provides greater resistance to movement of the control rod in the direction toward the drive hub than in the other direction

  17. Wind effects on collectors. Final report, October 1, 1978--October 1, 1979

    Energy Technology Data Exchange (ETDEWEB)

    Hewitt, H.C. Jr.; Griggs, E.I.

    1979-11-01

    Consideration was given to modeling wind speed data and to a scheme for correlating data between two separate stations. A sensor system was developed to measure the effect of wind on collector performance. The specifications for the sensor are presented, and a discussion of the calibration of the sensor is given. Four experiments were performed to determine wind flow patterns around buildings. The velocity profile over an actual collector was also measured as a function of free stream velocity. A mathematical model for a solar collector and three experimental efforts to measure the effect of wind on collector performance are reported. (MHR)

  18. Climatic wind tunnel for wind engineering tasks

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil

    2015-01-01

    Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf

  19. Ion Velocity Measurements for the Ionospheric Connections Explorer

    Science.gov (United States)

    Heelis, R. A.; Stoneback, R. A.; Perdue, M. D.; Depew, M. D.; Morgan, W. A.; Mankey, M. W.; Lippincott, C. R.; Harmon, L. L.; Holt, B. J.

    2017-10-01

    The Ionospheric Connections Explorer (ICON) payload includes an Ion Velocity Meter (IVM) to provide measurements of the ion drift motions, density, temperature and major ion composition at the satellite altitude near 575 km. The primary measurement goal for the IVM is to provide the meridional ion drift perpendicular to the magnetic field with an accuracy of 7.5 m s-1 for all daytime conditions encountered by the spacecraft within 15° of the magnetic equator. The IVM will derive this parameter utilizing two sensors, a retarding potential analyzer (RPA) and an ion drift meter (IDM) that have a robust and successful flight heritage. The IVM described here incorporates improvements in the design and operation to produce the most sensitive device that has been fielded to date. It will specify the ion drift vector, from which the component perpendicular to the magnetic field will be derived. In addition it will specify the total ion density, the ion temperature and the fractional ion composition. These data will be used in conjunction with measurements from the other ICON instruments to uncover the important connections between the dynamics of the neutral atmosphere and the ionosphere through the generation of dynamo currents perpendicular to the magnetic field and collisional forces parallel to the magnetic field. Here the configuration and operation of the IVM instrument are described, as well as the procedures by which the ion drift velocity is determined. A description of the subsystem characteristics, which allow a determination of the expected uncertainties in the derived parameters, is also given.

  20. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    Mortensen, Niels Gylling; Said Said, Usama; Badger, Jake

    2006-01-01

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  1. Wind Atlas for Egypt

    DEFF Research Database (Denmark)

    The results of a comprehensive, 8-year wind resource assessment programme in Egypt are presented. The objective has been to provide reliable and accurate wind atlas data sets for evaluating the potential wind power output from large electricityproducing wind turbine installations. The regional wind...... climates of Egypt have been determined by two independent methods: a traditional wind atlas based on observations from more than 30 stations all over Egypt, and a numerical wind atlas based on long-term reanalysis data and a mesoscale model (KAMM). The mean absolute error comparing the two methods is about...... 10% for two large-scale KAMM domains covering all of Egypt, and typically about 5% for several smaller-scale regional domains. The numerical wind atlas covers all of Egypt, whereas the meteorological stations are concentrated in six regions. The Wind Atlas for Egypt represents a significant step...

  2. Mesospheric winds measurements using three meteor radars in Brazil

    Science.gov (United States)

    Batista, Paulo; Clemesha, Barclay; Fátima Andrioli, Vânia; Paulino, Ana Roberta; Buriti, Ricardo; Schuch, Nelson Jorge

    Three meteor radars of the SkiYmet type have been installed in Brazil covering low, tropical and sub-tropical latitudes. The first at Cachoeira Paulista(22.7 S, 45.0 W) started in march 1999, the second at Cariri(7.4 S, 36.5 W) in May, 2005, and the last one at Santa Maria( 29.7 S, 53.8 W) in December, 2005. Coincident periods of measurements permitted the determination of the Mean Winds, Planetary Waves, Tides and Gravity Wave Variances for these different latitudes and their comparison. Amplitude and phase structures are similar for Cachoeira Paulista and Santa Maria, but differ from the near-equatorial site Cariri. Also the Lunar Semidiurnal Tides have been studied at the three sites for the period January 2005 to December 2008. Amplitudes between 1 and 8 m/s were determined with the meridional winds being larger than the zonal in the three sites. Wind measurements have been used also as subsidiary data in the studies involving the sodium layer and the mesospheric airglow though lidar, photometers and imagers.

  3. Southern hemisphere low level wind circulation statisticsfrom the Seasat scatterometer

    Directory of Open Access Journals (Sweden)

    G. Levy

    1994-01-01

    Full Text Available Analyses of remotely sensed low-level wind vector data over the Southern Ocean are performed. Five-day averages and monthly means are created and the month-to-month variability during the winter (July-September of 1978 is investigated. The remotely sensed winds are compared to the Australian Bureau of Meteorology (ABM and the National Meteorological Center (NMC surface analyses. In southern latitudes the remotely sensed winds are stronger than what the weather services' analyses suggest, indicating underestimation by ABM and NMC in these regions. The evolution of the low-level jet and the major stormtracks during the season are studied and different flow regimes are identified. The large-scale variability of the meridional flow is studied with the aid of empirical orthogonal function (EOF analysis. The dominance of quasi-stationary wave numbers 3, 4, and 5 in the winter flow is evident in both the EOF analysis and the mean flow. The signature of an exceptionally strong blocking situation is evident in July and the special conditions leading to it are discussed. A very large intraseasonal variability with different flow regimes at different months is documented.

  4. Southern hemisphere low level wind circulation statisticsfrom the Seasat scatterometer

    Directory of Open Access Journals (Sweden)

    Gad Levy

    Full Text Available Analyses of remotely sensed low-level wind vector data over the Southern Ocean are performed. Five-day averages and monthly means are created and the month-to-month variability during the winter (July-September of 1978 is investigated. The remotely sensed winds are compared to the Australian Bureau of Meteorology (ABM and the National Meteorological Center (NMC surface analyses. In southern latitudes the remotely sensed winds are stronger than what the weather services' analyses suggest, indicating underestimation by ABM and NMC in these regions. The evolution of the low-level jet and the major stormtracks during the season are studied and different flow regimes are identified. The large-scale variability of the meridional flow is studied with the aid of empirical orthogonal function (EOF analysis. The dominance of quasi-stationary wave numbers 3, 4, and 5 in the winter flow is evident in both the EOF analysis and the mean flow. The signature of an exceptionally strong blocking situation is evident in July and the special conditions leading to it are discussed. A very large intraseasonal variability with different flow regimes at different months is documented.

  5. Extreme wind estimate for Hornsea wind farm

    DEFF Research Database (Denmark)

    Larsén, Xiaoli Guo

    The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two ap....... The greatest sector-wise extreme winds are from west to northwest. Different data, different periods and different methods have provided a range of values of the 50-year wind and accordingly the gust values, as summarized in Table 15.......The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...

  6. Effects of forward velocity on turbulent jet mixing noise

    Science.gov (United States)

    Plumblee, H. E., Jr. (Editor)

    1976-01-01

    Flight simulation experiments were conducted in an anechoic free jet facility over a broad range of model and free jet velocities. The resulting scaling laws were in close agreement with scaling laws derived from theoretical and semiempirical considerations. Additionally, measurements of the flow structure of jets were made in a wind tunnel by using a laser velocimeter. These tests were conducted to describe the effects of velocity ratio and jet exit Mach number on the development of a jet in a coflowing stream. These turbulence measurements and a simplified Lighthill radiation model were used in predicting the variation in radiated noise at 90 deg to the jet axis with velocity ratio. Finally, the influence of forward motion on flow-acoustic interactions was examined through a reinterpretation of the 'static' numerical solutions to the Lilley equation.

  7. Characteristics of Arctic winds at CANDAC-PEARL (80° N, 86° W and Svalbard (78° N, 16° E for 2006–2009: radar observations and comparisons with the model CMAM-DAS

    Directory of Open Access Journals (Sweden)

    A. H. Manson

    2011-10-01

    Full Text Available Operation of a Meteor Wind Radar (MWR at Eureka, Ellesmere Island (80° N, 86° W began in February 2006; this is the location of the Polar Environmental and Atmospheric Research Laboratory (PEARL, operated by the "Canadian Network for the Detection of Atmospheric Change" (CANDAC. The first 36 months of wind data (82–97 km are here combined with contemporaneous winds from the Meteor Wind Radar at Adventdalen, Svalbard (78° N, 16° E, to provide the first evidence for substantial interannual variability (IAV of longitudinally spaced observations of mean/background winds and waves at such High Arctic latitudes. The influences of "Sudden Stratospheric Warmings" (SSW are also apparent. Monthly meridional (north-south, NS 3-year means for each location/radar demonstrate that winds (82–97 km differ significantly between Canada and Norway, with winter-equinox values generally northward over Eureka and southward over Svalbard. Using January 2008 as case study, these oppositely directed meridional winds are related to mean positions of the Arctic mesospheric vortex. The vortex is from the Canadian Middle Atmosphere Model, with its Data Assimilation System (CMAM-DAS. The characteristics of "Sudden stratospheric Warmings" SSW in each of the three winters are noted, as well as their uniquely distinctive short-term mesospheric wind disturbances. Comparisons of the mean winds over 36 months at 78 and 80° N, with those within CMAM-DAS, are featured. E.g. for 2007, while both monthly mean EW and NS winds from CMAM/radar are quite similar over Eureka (82–88 km, the modeled autumn-winter NS winds over Svalbard (73–88 km differ significantly from observations. The latter are southward, and the modeled winds over Svalbard are predominately northward. The mean positions of the winter polar vortex are related to these differences.

  8. Research and analysis on response characteristics of bracket-line coupling system under wind load

    Science.gov (United States)

    Jiayu, Zhao; Qing, Sun

    2018-01-01

    In this paper, a three-dimensional finite element model of bracket-line coupling system is established based on ANSYS software. Using the wind velocity time series which is generated by MATLAB as a power input, by comparing and analyzing the influence of different wind speeds and different wind attack angles, it is found that when 0 degree wind acts on the structure, wires have a certain damping effect in the bracket-line coupling system and at the same wind speed, the 90 degree direction is the most unfavorable wind direction for the whole structure according to the three kinds of angle wind calculated at present. In the bracket-line coupling system, the bracket structure is more sensitive to the increase of wind speed while the conductors are more sensitive to the change of wind attack angle.

  9. Sodium Velocity Maps on Mercury

    Science.gov (United States)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  10. Offshore and onshore wind turbine wake meandering studied in an ABL wind tunnel

    DEFF Research Database (Denmark)

    Barlas, Emre; Buckingham, Sophia; Glabeke, Gertjan

    2015-01-01

    Scaled wind turbine models have been installed in the VKI L1-B atmospheric boundary layer wind tunnel at offshore and onshore conditions. Time-resolved measurements were carried out with three component hot wire anemometry and stereo-PIV in the middle vertical plane of the wake up to eleven turbine...... spectrum, present in the entire wake mainly for offshore inflow condition. It was found that the Strouhal number, based on the rotor diameter and the wind velocity at hub height, was in the order of 0.25. Below the meandering frequency, turbulence power spectrum decreased, whereas above it increased. Wake...... diameter downstream. The results show an earlier wake recovery for the onshore case. The effect of inflow conditions and the wind turbine’s working conditions on wake meandering was investigated. Wake meandering was detected by hot wire anemometry through a low frequency peak in the turbulent power...

  11. Wind tunnel study of helical and straight-bladed vertical-axis wind turbine wakes

    Science.gov (United States)

    Bagheri, Maryam; Araya, Daniel

    2017-11-01

    It is hypothesized that blade curvature can serve as a passive means to control fluid entrainment and wake recovery in vertical-axis wind turbine (VAWT) arrays. We test this experimentally in a wind tunnel using two different VAWT configurations, one with straight blades and another with helical blades, keeping all other experimental parameters fixed. A small-scale, commercially available VAWT (15W max power) is used as the baseline wind tunnel model in each case. The commercial VAWT blades are replaced with either straight or helical blades that are 3D-printed extrusions of the same airfoil cross-section. Results from smoke flow visualization, three-component wake velocity measurements, and turbine power data are presented. These results give insight into the potential use of VAWTs with curved blades in utility-scale wind farms.

  12. Wind Farm parametrization in the mesoscale model WRF

    DEFF Research Database (Denmark)

    Volker, Patrick; Badger, Jake; Hahmann, Andrea N.

    2012-01-01

    , but are parametrized as another sub-grid scale process. In order to appropriately capture the wind farm wake recovery and its direction, two properties are important, among others, the total energy extracted by the wind farm and its velocity deficit distribution. In the considered parametrization the individual...... the extracted force is proportional to the turbine area interfacing a grid cell. The sub-grid scale wake expansion is achieved by adding turbulence kinetic energy (proportional to the extracted power) to the flow. The validity of both wind farm parametrizations has been verified against observational data. We...... turbines produce a thrust dependent on the background velocity. For the sub-grid scale velocity deficit, the entrainment from the free atmospheric flow into the wake region, which is responsible for the expansion, is taken into account. Furthermore, since the model horizontal distance is several times...

  13. Offshore wind energy developments

    DEFF Research Database (Denmark)

    Stolpe, Mathias; Buhl, Thomas; Sumer, B. Mutlu

    2014-01-01

    This chapter will give a brief overview of a few of the activities within offshore wind energy research, specifically 1) Support structure optimization, 2) Blade coatings for wind turbines; 3) Scour protection of foundations, 4) Offshore HVDC and 5) Offshore wind services.......This chapter will give a brief overview of a few of the activities within offshore wind energy research, specifically 1) Support structure optimization, 2) Blade coatings for wind turbines; 3) Scour protection of foundations, 4) Offshore HVDC and 5) Offshore wind services....

  14. Wind energy information guide

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-04-01

    This book is divided into nine chapters. Chapters 1--8 provide background and annotated references on wind energy research, development, and commercialization. Chapter 9 lists additional sources of printed information and relevant organizations. Four indices provide alphabetical access to authors, organizations, computer models and design tools, and subjects. A list of abbreviations and acronyms is also included. Chapter topics include: introduction; economics of using wind energy; wind energy resources; wind turbine design, development, and testing; applications; environmental issues of wind power; institutional issues; and wind energy systems development.

  15. Wind Power Career Chat

    Energy Technology Data Exchange (ETDEWEB)

    2011-01-01

    This document will teach students about careers in the wind energy industry. Wind energy, both land-based and offshore, is expected to provide thousands of new jobs in the next several decades. Wind energy companies are growing rapidly to meet America's demand for clean, renewable, and domestic energy. These companies need skilled professionals. Wind power careers will require educated people from a variety of areas. Trained and qualified workers manufacture, construct, operate, and manage wind energy facilities. The nation will also need skilled researchers, scientists, and engineers to plan and develop the next generation of wind energy technologies.

  16. Arctic wind energy

    International Nuclear Information System (INIS)

    Peltola, E.; Holttinen, H.; Marjaniemi, M.; Tammelin, B.

    1998-01-01

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  17. Arctic wind energy

    Energy Technology Data Exchange (ETDEWEB)

    Peltola, E. [Kemijoki Oy (Finland); Holttinen, H.; Marjaniemi, M. [VTT Energy, Espoo (Finland); Tammelin, B. [Finnish Meteorological Institute, Helsinki (Finland)

    1998-12-31

    Arctic wind energy research was aimed at adapting existing wind technologies to suit the arctic climatic conditions in Lapland. Project research work included meteorological measurements, instrument development, development of a blade heating system for wind turbines, load measurements and modelling of ice induced loads on wind turbines, together with the development of operation and maintenance practices in arctic conditions. As a result the basis now exists for technically feasible and economically viable wind energy production in Lapland. New and marketable products, such as blade heating systems for wind turbines and meteorological sensors for arctic conditions, with substantial export potential, have also been developed. (orig.)

  18. Wind power today

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-04-01

    This publication highlights initiatives of the US DOE`s Wind Energy Program. 1997 yearly activities are also very briefly summarized. The first article describes a 6-megawatt wind power plant installed in Vermont. Another article summarizes technical advances in wind turbine technology, and describes next-generation utility and small wind turbines in the planning stages. A village power project in Alaska using three 50-kilowatt turbines is described. Very brief summaries of the Federal Wind Energy Program and the National Wind Technology Center are also included in the publication.

  19. The benefit of wind atlases in wind energy and their verification

    Science.gov (United States)

    Bethke, Julia; Kampmeyer, Jens; Mengelkamp, Heinz-Theo

    2014-05-01

    1 INTRODUCTION Wind atlases such as reanalysis data and downscaled data sets are widely used in the wind energy sector, e.g. for long-term correlation of short-term measurements or initial site search. Due to the financial impact of statements derived from wind atlases, their verification is of high importance. Here, different wind atlases are verified in-depth with numerous certified high-quality mast measurements covering a broad range of heights up to 200 m. In contrast to the commonly used weather stations, high masts allow for an evaluation of vertical profiles and atmospheric stability. The following questions will be addressed: What are wind atlases? How well are they performing? Which benefit do wind atlases have in wind energy? 2 APPROACH The performance of commonly used reanalysis data, e.g. MERRA, ERA-Interim, and two data sets downscaled from MERRA reanalysis data is investigated. The first downscaled data set is derived by the mesoscale model MM5 and has a spatial and temporal resolution of 20 km and 10 min, respectively. The second downscaled data set is derived by the WRF model and has a spatial and temporal resolution of 3 km and 10 min, respectively. Certified high-quality measurements of 45 met masts with 160 anemometers covering a range of complexity types, measurement heights between 30 m and 200 m and a time period of 2 years are compared to the wind atlases. Hourly values are analysed. 3 RESULTS The correlation with hourly measurements of wind speed is very good for all data sets. Correlation increases with decreasing terrain complexity. Wind directions are also met very well by all data sets. The frequency distributions of wind speed and therefore, the Weibull parameters are reproduced very well by the downscaled data sets for a broad range of velocities, however underestimating higher velocities. MERRA generally strongly overestimates wind speed. Diurnal and annual cycles as well as vertical profiles are reproduced more accurately by the

  20. Surface mapping, organic matter and water stocks in peatlands of the Serra do Espinhaço meridional - Brazil

    Directory of Open Access Journals (Sweden)

    Márcio Luiz da Silva

    2013-10-01

    Full Text Available Peatlands are soil environments that store carbon and large amounts of water, due to their composition (90 % water, low hydraulic conductivity and a sponge-like behavior. It is estimated that peat bogs cover approximately 4.2 % of the Earth's surface and stock 28.4 % of the soil carbon of the planet. Approximately 612 000 ha of peatlands have been mapped in Brazil, but the peat bogs in the Serra do Espinhaço Meridional (SdEM were not included. The objective of this study was to map the peat bogs of the northern part of the SdEM and estimate the organic matter pools and water volume they stock. The peat bogs were pre-identified and mapped by GIS and remote sensing techniques, using ArcGIS 9.3, ENVI 4.5 and GPS Track Maker Pro software and the maps validated in the field. Six peat bogs were mapped in detail (1:20,000 and 1:5,000 by transects spaced 100 m and each transect were determined every 20 m, the UTM (Universal Transverse Mercator coordinates, depth and samples collected for characterization and determination of organic matter, according to the Brazilian System of Soil Classification. In the northern part of SdEM, 14,287.55 ha of peatlands were mapped, distributed over 1,180,109 ha, representing 1.2 % of the total area. These peatlands have an average volume of 170,021,845.00 m³ and stock 6,120,167 t (428.36 t ha-1 of organic matter and 142,138,262 m³ (9,948 m³ ha-1 of water. In the peat bogs of the Serra do Espinhaço Meridional, advanced stages of decomposing (sapric organic matter predominate, followed by the intermediate stage (hemic. The vertical growth rate of the peatlands ranged between 0.04 and 0.43 mm year-1, while the carbon accumulation rate varied between 6.59 and 37.66 g m-2 year-1. The peat bogs of the SdEM contain the headwaters of important water bodies in the basins of the Jequitinhonha and San Francisco Rivers and store large amounts of organic carbon and water, which is the reason why the protection and preservation

  1. Influence of Velocity Curves Unevenness on the Centrifugal Pump Head

    Directory of Open Access Journals (Sweden)

    V. A. Cheryomushkin

    2017-01-01

    Full Text Available A formula of the theoretical head, which gives the value of the impeller in terms of its geometrical parameters, is used to calculate the pump head at the stage of theoretical design. One of the main assumptions in this case is a strip theory, which does not take into consideration the unevenness of curves of the meridional and circumferential velocity components at the impeller outlet of a centrifugal pump. The article studies this influence. Describes a mathematical model for theoretical and numerical calculations. Shows the figures of the flow part under study and of the computational grid. For complete formalization of the problem the meshing models and boundary conditions are shown. As the boundary conditions, full pump-inlet head into the flow part and velocity at the outlet were used. Then, there are the graphs to compare the results of theoretical and numerical calculation and the error is shown. For comparison, a value of the theoretical head was multiplied by the efficiency, which was defined by computer simulation. A designing process of the flow part was iterative, so the comparison was carried out for all iterations. It should be noted that correction for the finite number of blades is also assumption. To determine a degree of the errors impact because of this correction, an average value of the circumferential component of the fluid velocity at the impeller outlet was calculated by two above methods followed by their comparison. It was shown that this impact is negligible, i.e. correction provides a sufficiently accurate value. In conclusion, the paper explains the possible reasons for inaccuracies in theoretical determination of the head, as well as the option to eliminate this inaccuracy, thereby reducing the time required for defining the basic parameters of the flow part. To illustrate the nature of fluid flow, for the last iteration are given the fields of the pressure distribution and the velocity vector in the equatorial

  2. Sand Drift Potential by Wind in Shileh Plain of Sistan

    Directory of Open Access Journals (Sweden)

    S. Poormand

    2016-02-01

    Full Text Available Introduction: Wind erosion is one of the most important factors in desert environments. Prevailing winds can shift sand dunes and affect their accumulation and morphology. Also, wind regime determines the direction of sand dune mobility in different ways. Therefore, the wind regime, frequency, direction and velocity are supposed to be the most important factors to form the morphology of sand dunes. Wind energy and changes in different directions (wind regime have large impacts on the morphology, maintenance and transformation of wind features. Having a global knowledge of the magnitude of aeolian processes, we can assess the powerful impact of sand dune mobility on residential areas and infrastructures. The most important factors including the frequency, magnitude and directional mobility of aeolian processes have a very important effect on the entrainment and form of sand dunes. Materials and Methods: To understand and identify the wind erosion regions, wind regime is a useful way since there is a strong correlation between wind regimes and sand dune morphology and structure. Sand rose and wind rose are assumed to be easy, fast and most accurate methods for the identification of wind erosion. Wind regimes processes have been studied by many researchers who believed that investigating wind regimes and sand dune mobility gives a measure of drift potential. Drift potential is a measure of the sand-moving capability by wind; derived from reduction of surface-wind data through a weighting equation. To predict drift potential, wind velocity and direction data from meteorological synoptic stations were used. Regarding the estimation of sand transport rate by wind, many formulas exist such as Bagnold, Kawamura, and Lattau. Also, many software applications have been suggested. However, among these formulas, Fryberger’s is the best and has been widely used since 1979. Results and Discussion: The aim of this study was to analyze wind velocities and

  3. Relation of solar wind fluctuations to differential flow between protons and alphas

    Science.gov (United States)

    Neugebauer, M.

    1974-01-01

    An analysis is made of the difference between the alpha particle and proton flow velocities in the solar wind as observed by the OGO 5 satellite. The alpha and proton velocities from each of 962 spectral scans are compared with the variance of 32 solar wind flux measurements made during the scans. The average velocity difference is plotted for each of 10 logarithmic variance intervals and is seen to decrease and approach zero when the variance is high. It is shown that such an anticorrelation may be due to the fact the wave/particle interactions provide the drag force between two streams of different velocity in a collisionless plasma.

  4. Diffraction imaging and velocity analysis using oriented velocity continuation

    KAUST Repository

    Decker, Luke

    2014-08-05

    We perform seismic diffraction imaging and velocity analysis by separating diffractions from specular reflections and decomposing them into slope components. We image slope components using extrapolation in migration velocity in time-space-slope coordinates. The extrapolation is described by a convection-type partial differential equation and implemented efficiently in the Fourier domain. Synthetic and field data experiments show that the proposed algorithm is able to detect accurate time-migration velocities by automatically measuring the flatness of events in dip-angle gathers.

  5. On the early stages of wind wave under non-stationary wind conditions.

    Science.gov (United States)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2017-04-01

    Most efforts in the study of the generation and evolution of wind waves have been conducted under constant wind. The balance of the transfer of different properties has been studied mainly for situations where the wave has already reached the equilibrium with the constant wind conditions. The purpose of these experiments is to study the early stages of the generation of waves under non-stationary wind conditions and to determine a balance in the exchange at the air-water interface for non-equilibrium wind conditions. A total of 16 experiments with a characteristic acceleration and deceleration rate of wind speed were conducted in a large wind-wave facility of Institut Pythéas (Marseille-France). The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. The momentum fluxes were estimated from hot wire anemometry at station 7. Also, the free surface displacement was measured along the channel tank at 11 stations where resistance wires were installed, except at stations 1, 2, and 7 where capacitance wires were installed. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. During experiments the wind intensity was abruptly increased with a constant acceleration rate over time, reaching a constant maximum intensity of 13 m/s. This constant velocity remains some time until the intensity is again reduced suddenly. We observed that wind drag coefficient values are higher for the experiments that present the lower acceleration rate; some field data from previous studies is presented for reference (Large and Pond 1981; Ocampo-Torres et al. 2011; Smith 1980; Yelland and Taylor 1996). The empirical grow curves show that in the experiments with lower acceleration, the wave field is more developed, showing higher dimensional energy and lower dimensional peak frequency. In the evolution of the spectral wave energy, there is first high frequency energy saturation, followed by a downshift of

  6. Evolution of wind towards wind turbine

    NARCIS (Netherlands)

    Giyanani, A.H.; Bierbooms, W.A.A.M.; Van Bussel, G.J.W.

    2015-01-01

    Remote sensing of the atmospheric variables with the use of LiDAR is a relatively new technology field for wind resource assessment in wind energy. The validation of LiDAR measurements and comparisons is of high importance for further applications of the data.

  7. Analysis of ISEE-3/ICE solar wind data

    Science.gov (United States)

    Coplan, Michael A.

    1989-01-01

    Under the grant that ended November 11, 1988 work was accomplished in a number of areas, as follows: (1) Analysis of solar wind data; (2) Analysis of Giacobini/Zinner encounter data; (3) Investigation of solar wind and magnetospheric electron velocity distributions; and (4) Experimental investigation of the electronic structure of clusters. Reprints and preprints of publications resulting from this work are included in the appendices.

  8. Fiber Laser for Wind Speed Measurements

    DEFF Research Database (Denmark)

    Olesen, Anders Sig

    This PhD thesis evaluates the practical construction and use of a Frequency Stepped Pulse Train modulated coherent Doppler wind lidar (FSPT lidar) for wind speed measurement. The concept of Doppler lidar is introduced as a means to measure line of sight wind speed by the Doppler shift of reflected...... light from aerosols. Central concepts are introduced and developed, i.a. heterodyne detection, carrier-to-noise ratio, probe length, measuring distance, and velocity precision. On this basis the concepts of a FSPT lidar are introduced and its general setup explained. The Lightwave Synthesized Frequency...... Sweeper (LSFS) is introduced and analyzed as a light source for the FSPT lidar. The setup of the LSFS is discussed, and the necessary concepts for modeling and analyzing LSFS noise are developed. The model and measurements are then used to discuss the growth of optical noise in the LSFS and the impact...

  9. Scaling forecast models for wind turbulence and wind turbine power intermittency

    Science.gov (United States)

    Duran Medina, Olmo; Schmitt, Francois G.; Calif, Rudy

    2017-04-01

    The intermittency of the wind turbine power remains an important issue for the massive development of this renewable energy. The energy peaks injected in the electric grid produce difficulties in the energy distribution management. Hence, a correct forecast of the wind power in the short and middle term is needed due to the high unpredictability of the intermittency phenomenon. We consider a statistical approach through the analysis and characterization of stochastic fluctuations. The theoretical framework is the multifractal modelisation of wind velocity fluctuations. Here, we consider three wind turbine data where two possess a direct drive technology. Those turbines are producing energy in real exploitation conditions and allow to test our forecast models of power production at a different time horizons. Two forecast models were developed based on two physical principles observed in the wind and the power time series: the scaling properties on the one hand and the intermittency in the wind power increments on the other. The first tool is related to the intermittency through a multifractal lognormal fit of the power fluctuations. The second tool is based on an analogy of the power scaling properties with a fractional brownian motion. Indeed, an inner long-term memory is found in both time series. Both models show encouraging results since a correct tendency of the signal is respected over different time scales. Those tools are first steps to a search of efficient forecasting approaches for grid adaptation facing the wind energy fluctuations.

  10. Vertical evolution of wind meandering in a nocturnal boundary layer during low-wind speed conditions

    Science.gov (United States)

    Stefanello, Michel; Acevedo, Otávio; Mortarini, Luca; Cava, Daniela; Giostra, Umberto; Degrazia, Gervásio; Anfossi, Domenico

    2017-04-01

    In the nocturnal boundary layer episodes of horizontal wind meandering are frequent. These episodes are characterised by low-wind regimes (wind speed less than 1.5 m s-1) in which submeso motions drive the wind dynamics and turbulence is weak and often intermittent. The inception of the meandering phenomenon as well as the interaction between turbulence and the submeso oscillations are still poorly understood. In this work we study the vertical evolution of the wind meandering by analysingnight-time anemometric data. The observations were carried on at a coastal site in Espirito Santo state, south-eastern Brazil from august to November 2016. The turbulent data, divided in hourly series, were collected in a 140-m tower designed to provide micrometeorological observations with high vertical resolution and deep coverage of the lower portion of the atmospheric boundary layer. Particularly, turbulence observations of the wind components and temperature are carried at 11 vertical levels. The tower has been deployed next to a natural gas power plant, at 3 km from the ocean. The terrain is generally flat for an area of 30 km from the tower, where moderate hills exist. The meandering timescale at each level is evaluated through the Eulerian Autocorrelation Functions of the horizontal wind velocity components and temperature, while the interactions between the different scales of motions is studied using the multi-correlation analysis. Thus the vertical evolution of meandering and time scales structure can be studied.

  11. Feasibility study on the wind farm; Wind farm no kanosei chosa

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-03-01

    For assessment of the possibility of the wind farm (collective wind power facility) in Japan, site conditions, business plans and various issues in development were arranged using some projects in a planning stage. The case study of a system design was also conducted for a typical site. Four sites were selected based on geographical conditions, topographic features and weather conditions. Scales of every site are as large as 1000-3000kW and 400- 750kW in wind turbine capacity. Every developer expects a subsidy, and governmental economic support is indispensable for the wind farm. In the case of Hisai city, Mie prefecture with the most favorable wind condition in Japan, the annual mean wind velocity of the site is valued at nearly 8m/s, suggesting that it is promising for the wind farm. From the planned scale of 750kWtimes4, the annual generated power and availability factor are valued at 9,800,000kWh/y and 37%, respectively. From the construction cost of 1 billion yen including a subsidy of its half, the generation cost is valued at 14.5 yen/kWh in durability of 15 years, and 12.2 yen/kWh in 20 years, and the profitability is dependent on the purchase price of a power company. 27 figs., 36 tabs.

  12. Calculating wind profiles above a pine forest

    International Nuclear Information System (INIS)

    Murphy, C.E.; Dexter, A.H.

    1978-01-01

    A major part of the environmental transport work at the Savannah River Laboratory (SRL) involves the dispersion of airborne pollutants (aerosols and gases). A major part of the Savannah River Plant (SRP) site is covered with pine forests. Because forests are ''rough'' surfaces which increase turbulence and surface shear stress and, hence, alter the dispersion patterns, the nature of the wind profiles above the forests is being investigated. Two methods for determining the surface shear caused by the atmospheric wind field over a pine plantation were compared. Friction velocity [the square root of the ratio of shearing stress over the density of air; U/sub */ = (stress/density)1/2] calculated by eddy correlation was compared with friction velocity calculated from wind profiles. Data from the first five meters above the pine forest were compared. The data indicated that there was no significant difference in the mean friction velocity measured by each method. However, there were large differences in individual values calculated by the two methods for many of the measurement periods. An attempt was made to reconcile the differences in the measured values, but no satisfactory method was found

  13. Wind Tunnel Measurements at LM Wind Power

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    The optimization of airfoil profiles specifically designed for wind turbine application was initiated in the late 80’s [67, 68, 30, 15]. The first attempts to reduce airfoil noise for wind turbines made use of airfoil trailing edge serration. Themodification of airfoil shapes targeted at noise...... reduction is more recent. An important effort was produced in this direction within the SIROCCO project. This latter work involved measurements on full size wind turbines and showed that trailing edge serration may proved a viable solution for mitigating wind turbine noise though it has not been implemented...... on commercial wind turbine yet. It should be mentioned here that the attenuation of turbulent inflow noise using wavy leading edge has recently been investigated [55], but this technique has still to be further validated for practical applications. In this paper, it is proposed to optimize an airfoil which...

  14. Lattice Wind Description and Characterization of Mexico City Local Wind Events in the 2001–2006 Period

    Directory of Open Access Journals (Sweden)

    Alejandro Salcido

    2015-07-01

    Full Text Available Urban transformation and expansion in Mexico City continuously affect its urban morphology, and therefore the modes of wind circulation inside it and their occurrence probabilities. Knowledge on these topics is an important issue for urban planning and for other urban studies, such as air quality assessment. In this paper, using a lattice wind model at a meso-β scale, we develop a simple description and characterization of Mexico City local wind events that occurred during the period 2001–2006, including an estimation of the occurrence probabilities. This region was modeled as a 2D lattice domain of identical cells, and wind conditions in each cell were described by four wind attributes: the horizontal velocity components, divergence, and vorticity. Models of one and four cells were applied to wind data furnished by the meteorological network of the city. Results include the following: Early morning: low intensity winds (75% from N, NW, W and SW (75%, convergent (93%, with a slight predominance of cyclonic vorticity (54%. Morning and early afternoon: winds from N, NE and E (72% with speeds from 0.5 to 3.5 m/s, slight prevailing of convergent winds (51%, and slight predominance of cyclonic vorticity (57%. Late afternoon and night: winds blowing from N, NW, and S (63% with speeds from 1.5 to 3.5 m/s (66%, convergent (90%, and cyclonic (72%.

  15. Imaging doppler lidar for wind turbine wake profiling

    Science.gov (United States)

    Bossert, David J.

    2015-11-19

    An imaging Doppler lidar (IDL) enables the measurement of the velocity distribution of a large volume, in parallel, and at high spatial resolution in the wake of a wind turbine. Because the IDL is non-scanning, it can be orders of magnitude faster than conventional coherent lidar approaches. Scattering can be obtained from naturally occurring aerosol particles. Furthermore, the wind velocity can be measured directly from Doppler shifts of the laser light, so the measurement can be accomplished at large standoff and at wide fields-of-view.

  16. Fourier Simulation of a Non-Isotropic Wind Field Model

    DEFF Research Database (Denmark)

    Mann, J.; Krenk, S.

    -spectra. In this paper a method is described which builds on a recently developed model of a spectral tensor for atmospheric surface layer turbulence at high wind speeds. Although the tensor does not in principle contain more information than the cross-spectra, it leads to a more natural and direct representation...... the vertical velocity fluctuations give rise to loads. There may even be structures where combinations of velocity fluctuations in different direction are of importance. Most methods that have been developed to simulate the turbulent wind field are based on one-point (cross-)spectra and two-point cross...

  17. An evaluation of the WindEye wind lidar

    DEFF Research Database (Denmark)

    Dellwik, Ebba; Sjöholm, Mikael; Mann, Jakob

    Prevision of the wind field by remote sensing wind lidars has the potential to improve the performance of wind turbines. The functionality of a WindEye lidar developed by Windar Photonics A/S (Denmark) for the wind energy market was tested in a two months long field experiment. The WindEye sensor...... with a high accuracy during the whole campaign....

  18. Wind electric power generation

    International Nuclear Information System (INIS)

    Koch, M.K.; Wind, L.; Canter, B.; Moeller, T.

    2001-01-01

    The monthly statistics of wind electric power generation in Denmark are compiled from information given by the owners of the private wind turbines. For each wind turbine the name of the site and of the type of turbine is given, and the power generation data are given for the month in question together with the total production in 1999 and 2000. Also the data of operation start are given. On the map of Denmark the sites of the wind turbines are marked. (CLS)

  19. The Irish Wind Atlas

    Energy Technology Data Exchange (ETDEWEB)

    Watson, R. [Univ. College Dublin, Dept. of Electronic and Electrical Engineering, Dublin (Ireland); Landberg, L. [Risoe National Lab., Meteorology and Wind Energy Dept., Roskilde (Denmark)

    1999-03-01

    The development work on the Irish Wind Atlas is nearing completion. The Irish Wind Atlas is an updated improved version of the Irish section of the European Wind Atlas. A map of the irish wind resource based on a WA{sup s}P analysis of the measured data and station description of 27 measuring stations is presented. The results of previously presented WA{sup s}P/KAMM runs show good agreement with these results. (au)

  20. Turbulence and wind turbines

    DEFF Research Database (Denmark)

    Brand, Arno J.; Peinke, Joachim; Mann, Jakob

    2011-01-01

    The nature of turbulent flow towards, near and behind a wind turbine, the effect of turbulence on the electricity production and the mechanical loading of individual and clustered wind turbines, and some future issues are discussed.......The nature of turbulent flow towards, near and behind a wind turbine, the effect of turbulence on the electricity production and the mechanical loading of individual and clustered wind turbines, and some future issues are discussed....