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KATAGIRI, Junji, Takeshi OHKUMA, and Hisao MARUKAWA. "ANALYTICAL METHODS FOR COUPLED WIND RESPONCE OF ACROSS-WIND AND TORSION WITH MOTION-INDUCED WIND FORCES." Journal of Structural and Construction Engineering (Transactions of AIJ) 67, no. 555 (2002): 45–52. http://dx.doi.org/10.3130/aijs.67.45_4.
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Carlini, Maurizio, Tommaso Honorati, and Sonia Castellucci. "Photovoltaic Greenhouses: Comparison of Optical and Thermal Behaviour for Energy Savings." Mathematical Problems in Engineering 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/743764.
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The production of energy from renewable sources, the diversification of the productive activities, and the development of photovoltaic technology and integrated systems have led to the development of solar greenhouses. The interest of the developers and designers is now to seek new approaches to combine the electricity and food production optimally. The interaction of factors as outside local climate, exposure, slope, soil, altitude, wind conditions, structural materials, or cultivated plant species, influences greatly the energy balance. This paper illustrates the comparison of optical and thermal behavior of a solar greenhouse and a similar glass greenhouse, devoted to the production of soil-less tomatoes in three different Italian areas, with computational aspects and methods of the TRNSYS simulation. Values of climatic parameters are obtained as a responce for the feasibility of the cultivation under PV modules. The results show energy savings both for heating and cooling due to PV panels, adding a new reason for the realization of these systems.
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Dufour, C. O., J. Le Sommer, J. D. Zika, M. Gehlen, J. C. Orr, P. Mathiot, and B. Barnier. "Standing and Transient Eddies in the Response of the Southern Ocean Meridional Overturning to the Southern Annular Mode." Journal of Climate 25, no. 20 (May 11, 2012): 6958–74. http://dx.doi.org/10.1175/jcli-d-11-00309.1.
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Abstract To refine the understanding of how the Southern Ocean responds to recent intensification of the southern annular mode (SAM), a regional ocean model at two eddy-permitting resolutions was forced with two synthetic interannual forcings. The first forcing corresponds to homogeneously intensified winds, while the second concerns their poleward intensification, consistent with positive phases of the SAM. Resulting wind-driven responses differ greatly between the nearly insensitive Antarctic Circumpolar Current (ACC) and the more sensitive meridional overturning circulation (MOC). As expected, eddies mitigate the response of the ACC and MOC to poleward-intensified winds. However, transient eddies do not necessarily play an increasing role in meridional transport with increasing resolution. As winds and resolution increase, meridional transport from standing eddies becomes more efficient at balancing wind-enhanced overturning. These results question the current paradigms on the role of eddies and present new challenges for eddy flux parameterization. Results also indicate that spatial patterns of wind anomalies are at least as important as the overall change in intensity in influencing the Southern Ocean’s dynamic response to wind events. Poleward-intensified wind anomalies from the positive trend in the SAM are far more efficient in accelerating the ACC than homogeneous wind anomalies.
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Kapoor, Amber, Slimane Ouakka, Sanjay R. Arwade, Julie K. Lundquist, Matthew A. Lackner, Andrew T. Myers, Rochelle P. Worsnop, and George H. Bryan. "Hurricane eyewall winds and structural response of wind turbines." Wind Energy Science 5, no. 1 (January 14, 2020): 89–104. http://dx.doi.org/10.5194/wes-5-89-2020.
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Abstract. This paper describes the analysis of a wind turbine and support structure subject to simulated hurricane wind fields. The hurricane wind fields, which result from a large eddy simulation of a hurricane, exhibit features such as very high gust factors (>1.7), rapid direction changes (30∘ in 30 s), and substantial veer. Wind fields including these features have not previously been used in an analysis of a wind turbine, and their effect on structural loads may be an important driver of enhanced design considerations. With a focus on blade root loads and tower base loads, the simulations show that these features of hurricane wind fields can lead to loads that are substantially in excess of those that would be predicted if wind fields with equally high mean wind speeds but without the associated direction change and veer were used in the analysis. This result, if further verified for a range of hurricane and tropical storm simulations, should provide an impetus for revisiting design standards.
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Kilpatrick, Thomas, Niklas Schneider, and Bo Qiu. "Atmospheric Response to a Midlatitude SST Front: Alongfront Winds." Journal of the Atmospheric Sciences 73, no. 9 (August 10, 2016): 3489–509. http://dx.doi.org/10.1175/jas-d-15-0312.1.
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Abstract Satellite observations and modeling studies show that midlatitude SST fronts influence the marine atmospheric boundary layer (MABL) and atmospheric circulation. Here, the Weather Research and Forecasting (WRF) mesoscale model is used to explore the atmospheric response to a midlatitude SST front in an idealized, dry, two-dimensional configuration, with a background wind oriented in the alongfront direction. The SST front excites an alongfront wind anomaly in the free atmosphere, with peak intensity just above the MABL. This response is nearly quasigeostrophic, in contrast to the inertia–gravity wave response seen for cross-front background winds. The free-atmosphere response increases with the background wind , in contrast to previously proposed SST frontal MABL models. The MABL winds are nearly in Ekman balance. However, a cross-front wind develops in the MABL as a result of friction and rotation such that the MABL cross-front Rossby number ε ≈ 0.2. The MABL vorticity balance and scaling arguments indicate that advection plays an important role in the MABL dynamics. Surface wind convergence shows poor agreement with MABL depth-integrated convergence, indicating that the MABL mixed-layer assumption may not be appropriate for SST frontal zones with moderate to strong surface winds.
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Schneider, Niklas, and Bo Qiu. "The Atmospheric Response to Weak Sea Surface Temperature Fronts*." Journal of the Atmospheric Sciences 72, no. 9 (September 1, 2015): 3356–77. http://dx.doi.org/10.1175/jas-d-14-0212.1.
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Abstract The response of the atmospheric boundary layer to fronts of sea surface temperature (SST) is characterized by correlations between wind stress divergence and the downwind component of the SST gradient and between the wind stress curl and the crosswind component of the SST gradient. The associated regression (or coupling) coefficients for the wind stress divergence are consistently larger than those for the wind stress curl. To explore the underlying physics, the authors introduce a linearized model of the atmospheric boundary layer response to SST-induced modulations of boundary layer hydrostatic pressure and vertical mixing in the presence of advection by a background Ekman spiral. Model solutions are a strong function of the SST scale and background advection and recover observed characteristics. The coupling coefficients for wind stress divergence and curl are governed by distinct physics. Wind stress divergence results from either large-scale winds crossing the front or from a thermally direct, cross-frontal circulation. Wind stress curl, expected to be largest when winds are parallel to SST fronts, is reduced through geostrophic spindown and thereby yields weaker coupling coefficients.
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Marler, Thomas E. "Growth Responses to Wind Differ among Papaya Roots, Leaves, and Stems." HortScience 46, no. 8 (August 2011): 1105–9. http://dx.doi.org/10.21273/hortsci.46.8.1105.
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‘Sunrise’ and ‘Tainung 2’ papaya seedlings were subjected to 3 weeks of ambient winds in Guam during five experiments, and growth responses of roots, leaves, and stems were quantified to compare speed and extent of the plasticity among the organs. The cultivars responded similarly with 1 week eliciting stem growth responses and 2 weeks eliciting root responses. The timeframe of these studies was sufficient to enable adaptive responses in all three organs. Wind reduced stem and leaf expansion rate but not root extension rate, providing one example of how the form of response differed among the organs. A dose–effect was evident among the experiments with magnitude of response increasing with mean ambient wind speed. Asymmetric stem diameter and root tip density were examples of adaptive responses to directional wind load. These data on young papaya plants may be used to inform field experiments aiming to determine how chronic winds influence long-term growth and fitness.
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Toba, Yoshiaki, Kozo Okada, and Ian S. F. Jones. "The Response of Wind-Wave Spectra to Changing Winds. Part I: Increasing Winds." Journal of Physical Oceanography 18, no. 9 (September 1988): 1231–40. http://dx.doi.org/10.1175/1520-0485(1988)018<1231:trowws>2.0.co;2.
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Whitney, Michael M., and Daniel L. Codiga. "Response of a Large Stratified Estuary to Wind Events: Observations, Simulations, and Theory for Long Island Sound." Journal of Physical Oceanography 41, no. 7 (July 1, 2011): 1308–27. http://dx.doi.org/10.1175/2011jpo4552.1.
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Abstract The response to wind events in the Long Island Sound (LIS), a large macrotidal estuary influenced by rotation and stratification, is studied using long-term ferry-based current observations near the mouth, unstratified and stratified numerical simulations forced with along-estuary winds, and analytic solutions based on linear barotropic theory. The observed wind-event velocity anomalies for down-estuary winds have surface-intensified downwind flows flanking a deeper central upwind flow. Response to up-estuary wind events has a weaker magnitude and a broader and thicker downwind flow. The downwind and upwind flows are more laterally aligned than vertically layered, as determined by a newly defined dimensionless lateral alignment index. Simulation results and analytic solutions share the gross spatial patterns of the observed response, though statistical measures indicate weak agreement. Along-estuary variations in the simulation results and analytic solutions follow similar trends and are strongly influenced by variations of the bathymetric cross section. Wind-event anomalies in the section-averaged dynamics are dominated by the along-estuary pressure gradient opposing wind stress. In the stratified simulation, wind-driven density advection, isopycnal straining, and stirring modify stratification, eddy viscosities, and baroclinic pressure gradients. The wind-event response of the baroclinic pressure gradient is 15% of the barotropic gradient but is dynamically linked to response differences to up-estuary and down-estuary winds. The wind-event response asymmetries near the mouth are in qualitative agreement with observations and are opposite to asymmetries closer to the head.
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Parish, H. F., and L. R. Lyons. "Sensitivity studies of the E region neutral response to the postmidnight diffuse aurora." Annales Geophysicae 24, no. 6 (July 3, 2006): 1551–65. http://dx.doi.org/10.5194/angeo-24-1551-2006.
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Abstract. Measurements of the neutral thermosphere within the postmidnight substorm recovery phase diffuse aurora show very large horizontal winds, and strong vertical structure. Rocket, satellite, and ground based observations during the ARIA (Atmospheric Response in Aurora) campaigns, and earlier dawn side rocket observations, indicate neutral winds of up to 200 m/s, and a characteristic jet-like wind maximum around 110 to 120-km altitude, with strong shears above and below. The observed wind magnitudes are found to have a dependence on geomagnetic activity level, but recent modeling studies suggest that tides which propagate up from the troposphere and stratosphere may play an important role in generating the strong vertical variations in the neutral winds. The relative importance of auroral and tidal forcing in producing the measured wind structure is not known, however. Simulations have been performed using a three dimensional (3-D) high resolution limited area thermosphere model to understand the processes which generate the observed neutral structure within the postmidnight diffuse aurora. Parameters measured during the ARIA I observational campaign have been used to provide auroral forcing inputs for the model. Global background winds and tides have been provided by the CTIP (Coupled Thermosphere Ionosphere Plasmasphere) model. The sensitivity of the response of the neutral atmosphere to changes in different parameters has been examined. Variations in the amplitudes and phases of the propagating tides in the background winds are found to have significant effects on the neutral structure in the E region, and the wind structure below around 110km is found to be mainly produced by tidal forcing. Changes in the electric field and ion density affect the winds above around 120 km, and the importance of auroral forcing is found to depend on background winds. Variations in the orientation of the aurora relative to the background field, which may be caused by changes in the interplanetary magnetic field, are also found to modify the wind structure. When both auroral forcing and propagating tides are included, many of the basic characteristics of the wind structure are displayed, although the great strength of the wind shears is not well reproduced. The strength of the shears may be related to a currently unmodeled process, or to different types of waves.
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Haroonabadi, Hossein. "Unit Commitment in Power Market Considering Demand Response and Stochastic Wind Generation." International Journal of Engineering Research 3, no. 10 (October 1, 2014): 564–69. http://dx.doi.org/10.17950/ijer/v3s10/1003.
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Poulain, Pierre-Marie, Riccardo Gerin, Elena Mauri, and Romain Pennel. "Wind Effects on Drogued and Undrogued Drifters in the Eastern Mediterranean." Journal of Atmospheric and Oceanic Technology 26, no. 6 (June 1, 2009): 1144–56. http://dx.doi.org/10.1175/2008jtecho618.1.
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Abstract The wind effects on drogued and undrogued drifters are assessed using Coastal Ocean Dynamics Experiment (CODE) and Surface Velocity Program (SVP) drifter datasets and ECMWF wind products in the eastern Mediterranean. Complex and real linear regression models are used to estimate the relative slip of undrogued SVP drifters and to extract the wind-driven currents from the drifter velocities. The frequency response of the wind-driven currents is studied using cross-spectral analysis. By comparing the velocities of cotemporal and nearly collocated undrogued and drogued SVP drifters, it appears that undrogued SVP drifters have a general downwind slippage of about 1% of the wind speed. Time-lagged complex correlations and cross-spectral results show that the wind response is almost simultaneous. The velocities of SVP drifters drogued to 15 m are poorly correlated with the winds (R2 ≈ 3%): wind-driven currents have a magnitude of 0.7% of the wind speed and are 27°–42° to the right of the wind. For undrogued SVP drifters, the correlation with the winds increases to R2 ≈ 22% and the angle between winds and currents decreases to 17°–20°. The magnitude of the wind-driven currents is about 2% of the wind speed. For CODE designs, wind-driven currents are 1% of the wind speed at an angle of about 28° to the right of the wind (R2 ≈ 8%). Spectral and cospectral analyses reveal that the drifters sampled more anticyclonic than cyclonic motions. The inner coherence spectra show that wind and currents are more correlated at temporal scales spanning 3–10 days. They also confirm that the wind response is quasi-simultaneous and that currents are generally to the right of the wind.
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Cao, SS, ST Ke, WM Zhang, L. Zhao, YJ Ge, and XX Cheng. "Load–response correlation–based equivalent static wind loads for large cooling towers." Advances in Structural Engineering 22, no. 11 (April 22, 2019): 2464–75. http://dx.doi.org/10.1177/1369433219844336.
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The load–response correlation method has been recognized by the wind engineering community as a useful equivalent static wind load calculation method for structural design of quasi-static structures against strong winds. However, it has been found that the load–response correlation method is less effective to non-linear systems and in situations where load processes are non-Gaussian, such as large cooling towers subjected to strong winds. To validate the applicability of the load–response correlation method to large cooling towers, an aero-elastic model has been designed for a 215-m-high cooling tower in this article, which can simultaneously produce wind loads and wind-induced displacements of the structure according to wind tunnel model tests. Using data measured on the aero-elastic model, the exact results of correlation coefficients between wind loads and structural responses are obtained and validated by a non-linear finite element analysis. By comparing the correlation coefficients measured on the scaled model to the results based on the load–response correlation calculation, it is found that the correlations are much stronger for the load–response correlation calculation than those for the exact wind tunnel measurement. The explanation for this observation is that the non-linearity of the real structure and the non-Gaussian feature of the actual wind loads can weaken the correlations between the wind loads and the structural responses.
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Ruosteenoja, Kimmo, Timo Vihma, and Ari Venäläinen. "Projected Changes in European and North Atlantic Seasonal Wind Climate Derived from CMIP5 Simulations." Journal of Climate 32, no. 19 (August 30, 2019): 6467–90. http://dx.doi.org/10.1175/jcli-d-19-0023.1.
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Abstract Future changes in geostrophic winds over Europe and the North Atlantic region were studied utilizing output data from 21 CMIP5 global climate models (GCMs). Changes in temporal means, extremes, and the joint distribution of speed and direction were considered. In concordance with previous research, the time mean and extreme scalar wind speeds do not change pronouncedly in response to the projected climate change; some degree of weakening occurs in the majority of the domain. Nevertheless, substantial changes in high wind speeds are identified when studying the geostrophic winds from different directions separately. In particular, in northern Europe in autumn and in parts of northwestern Europe in winter, the frequency of strong westerly winds is projected to increase by up to 50%. Concurrently, easterly winds become less common. In addition, we evaluated the potential of the GCMs to simulate changes in the near-surface true wind speeds. In ocean areas, changes in the true and geostrophic winds are mainly consistent and the emerging differences can be explained (e.g., by the retreat of Arctic sea ice). Conversely, in several GCMs the continental wind speed response proved to be predominantly determined by fairly arbitrary changes in the surface properties rather than by changes in the atmospheric circulation. Accordingly, true wind projections derived directly from the model output should be treated with caution since they do not necessarily reflect the actual atmospheric response to global warming.
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Waugh, Darryn W., Andrew McC. Hogg, Paul Spence, Matthew H. England, and Thomas W. N. Haine. "Response of Southern Ocean Ventilation to Changes in Midlatitude Westerly Winds." Journal of Climate 32, no. 17 (July 26, 2019): 5345–61. http://dx.doi.org/10.1175/jcli-d-19-0039.1.
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ABSTRACT Changes in ventilation of the Southern Hemisphere oceans in response to changes in midlatitude westerly winds are examined by analyzing the ideal age tracer from global eddy-permitting ocean–ice model simulations in which there is an abrupt increase and/or a meridional shift in the winds. The age response in mode and intermediate waters is found to be close to linear; the response of a combined increase and shift of peak winds is similar to the sum of the individual responses to an increase and a shift. Further, a barotropic response, following Sverdrup balance, can explain much of the age response to the changes in wind stress. There are similar peak decreases (of around 50 years) in the ideal age for a 40% increase or 2.5° poleward shift in the wind stress. However, while the age decreases throughout the thermocline for an increase in the winds, for a poleward shift in the winds the age increases in the north part of the thermocline and there are decreases in age only south of 35°S. As a consequence, the change in the volume of young water differs, with a 15% increase in the volume of water with ages younger than 50 years for a 40% increase in the winds but essentially no change in this volume for a 2.5° shift. As ventilation plays a critical role in the uptake of carbon and heat, these results suggest that the storage of anthropogenic carbon and heat in mode and intermediate waters will likely increase with a strengthening of the winds, but will be much less sensitive to a meridional shift in the peak wind stress.
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Verdy, Ariane, Matthew R. Mazloff, Bruce D. Cornuelle, and Sung Yong Kim. "Wind-Driven Sea Level Variability on the California Coast: An Adjoint Sensitivity Analysis." Journal of Physical Oceanography 44, no. 1 (January 1, 2014): 297–318. http://dx.doi.org/10.1175/jpo-d-13-018.1.
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Abstract Effects of atmospheric forcing on coastal sea surface height near Port San Luis, central California, are investigated using a regional state estimate and its adjoint. The physical pathways for the propagation of nonlocal [O(100 km)] wind stress effects are identified through adjoint sensitivity analyses, with a cost function that is localized in space so that the adjoint shows details of the propagation of sensitivities. Transfer functions between wind stress and SSH response are calculated and compared to previous work. It is found that (i) the response to local alongshore wind stress dominates on short time scales of O(1 day); (ii) the effect of nonlocal winds dominates on longer time scales and is carried by coastally trapped waves, as well as inertia–gravity waves for offshore wind stress; and (iii) there are significant seasonal variations in the sensitivity of SSH to wind stress due to changes in stratification. In a more stratified ocean, the damping of sensitivities to local and offshore winds is reduced, allowing for a larger and longer-lasting SSH response to wind stress.
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Swart, N. C., J. C. Fyfe, O. A. Saenko, and M. Eby. "Wind driven changes in the ocean carbon sink." Biogeosciences Discussions 11, no. 6 (June 4, 2014): 8023–48. http://dx.doi.org/10.5194/bgd-11-8023-2014.
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Abstract. We estimate the historical ocean carbon sink over 1871 to 2010 using an ocean biogeochemical model driven with observed wind forcing. We focus on the influence of wind and mesoscale eddy changes on the net surface CO2 flux, which are most significant after 1950. The observed wind changes act to reduce the annual ocean carbon sink by 0.009 to 0.023 Pg yr−1 decade−1 over 1950 to 2010, and are consistent with previous studies covering only the latter part of the 20th century. The response of the ocean circulation and the carbon cycle to wind changes is sensitive to the parameterization of mesoscale eddies in our coarse resolution simulations. With a variable eddy transfer coefficient, eddy activity in the Southern Ocean increases in response to intensifying historical winds, partially compensating for direct wind-driven circulation changes. Thus with a variable eddy transfer coefficient the response to wind changes is about 2.5 times smaller than when using a constant coefficient. Finally, we show by comparing six reanalyses over 1980 to 2010 that estimated historical wind trends differ significantly. Through simulations forced with these reanalysis winds we show that the influence of historical wind changes on ocean carbon uptake is highly uncertain and depends on the choice of surface wind forcing product.
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Campbell-Clause, J. M. "Stomatal response of grapevines to wind." Australian Journal of Experimental Agriculture 38, no. 1 (1998): 77. http://dx.doi.org/10.1071/ea91220.
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Summary. A porometer study of 2 grapevine cultivars (Vitis vinifera cvv. Italia and Ribier) was conducted in the field to assess the effect of wind on stomatal resistance. The effect of differing light levels was also studied. Data of the grapevines stomatal resistance responses to wind and light were incorporated into the Penman–Monteith equation and an estimation of the effect of wind and light on evapotranspiration was made. Wind increased stomatal resistance for Ribier and Italia in an exponential manner. Both varieties showed a typical response to light with a flattening curve of decreasing stomatal resistance with increasing light. Stomatal resistance was similar at the upper range of light (>800 W/m2) for both Ribier and Italia. At lower light levels stomatal resistance of Ribier increased more than that of Italia. Stomatal resistance began to increase appreciably when the level of light fell below 400 W/m2 . Using the Penman–Monteith model, together with average weather data and including these responses to wind and light, daily evapotranspiration in January for Italia was calculated to be 4.03 mm/day (38.4% of class A pan evaporation) compared with 3.91 mm/day (37.2% of class A pan evaporation) for cv. Ribier. Wind speeds above 4 m/s reduced estimated evapotranspiration compared with less windy conditions (wind speed <4 m/s), more so at higher wind speeds. Reducing wind speed using a windbreak significantly increased water use and potential yield. Under Swan Valley conditions, a 3.6 m high, 40% permeable windbreak would be required every 60 m to reduce wind speed below 5.5 m/s for 93% of the time. Windbreak frequency can be determined for other areas with information on wind frequency and wind speed.
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Dorman, Clive E., and Darko Koračin. "Response of the Summer Marine Layer Flow to an Extreme California Coastal Bend." Monthly Weather Review 136, no. 8 (August 1, 2008): 2894–922. http://dx.doi.org/10.1175/2007mwr2336.1.
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Abstract A summer wind speed maximum extending more than 200 km occurs over water around Point Conception, California, the most extreme bend along the U.S. West Coast. The following several causes were investigated for this wind speed maximum: 1) synoptic conditions, 2) marine layer hydraulic flow effects, 3) diurnal variations, 4) mountain leeside downslope flow, 5) sea surface temperature structure, and 6) island influence. Synoptic conditions set the general wind speed around Point Conception, and these winds are classified as strong, moderate, or weak. The strong wind condition extends about Point Conception, reaching well offshore toward the southwest, and the highest speeds are within 20 km to the south. Moderate wind cases do not extend as far offshore, and they have a moderate maximum wind speed that occurs over a smaller area in the western mouth of the Santa Barbara Channel. The weak wind speed case consists of light and variable winds about Point Conception. Each category occurs about one-third of the time. Atmospheric marine layer hydraulic dynamics dominate the situation after the synoptic condition is set. This includes an expansion fan on the south side of the point and a compression bulge on the north side. The expansion fan significantly increases the wind speeds over a large area that extends to the southwest, south, and east of Point Conception, and the maximum wind speed is increased for the strong and moderate synoptic cases as well. The horizontal sea surface temperature pattern contributes to the sea surface wind maximum through the Froude number, which links the potential temperature difference between the sea surface temperature and the capping inversion temperature with marine layer acceleration in an expansion fan. A greater potential temperature difference across the top of the marine layer also causes more energy to be trapped in the marine layer, instead of escaping upward. The thermally driven flow resulting from differential heating over land in the greater Los Angeles, California, coastal and elevated area to the east is not directly related to the wind speed maximum, either in the Santa Barbara Channel or in the open ocean extending farther offshore. The effects of the thermally driven flow extend only to the east of the Santa Barbara Channel. The downslope flow on the south side of the Santa Ynez Mountains that is generated by winds crossing the Santa Ynez Mountain ridge contributes neither to the high-speed wind maximum in the Santa Barbara channel nor to that extending farther offshore. Fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) simulations do support a weak leeside flow in the upper portions of the Santa Ynez Mountains. The larger Channel Islands have a significant effect on the marine layer flow and the overwater wind structure. One major effect of the Santa Barbara Channel Islands is the extension of the zone of high-speed winds farther to the south than would otherwise be the case.
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Kim, Hong Yeon. "Reliability Analysis of Monopile for a Offshore Wind Turbine Using Response Surface Method." Journal of the Korean Society of Civil Engineers 33, no. 6 (2013): 2401. http://dx.doi.org/10.12652/ksce.2013.33.6.2401.
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Foussard, A., G. Lapeyre, and R. Plougonven. "Response of Surface Wind Divergence to Mesoscale SST Anomalies under Different Wind Conditions." Journal of the Atmospheric Sciences 76, no. 7 (June 26, 2019): 2065–82. http://dx.doi.org/10.1175/jas-d-18-0204.1.
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Abstract The response of the atmospheric boundary layer to mesoscale sea surface temperature (SST) is often characterized by a link between wind stress divergence and downwind SST gradients. In this study, an idealized simulation representative of a storm track above a prescribed stationary SST field is examined in order to determine in which background wind conditions that relationship occurs. The SST field is composed of a midlatitude large-scale frontal zone and mesoscale SST anomalies. It is shown that the divergence of the surface wind can correlate either with the Laplacian of the atmospheric boundary layer temperature or with the downwind SST gradient. The first case corresponds to background situations of weak winds or of unstable boundary layers, and the response is in agreement with an Ekman balance adjustment in the boundary layer. The second case corresponds to background situations of stable boundary layers, and the response is in agreement with downward mixing of momentum. Concerning the divergence of the wind stress, it generally resembles downwind SST gradients for stable and unstable boundary layers, in agreement with past studies. For weak winds, a correlation with the temperature Laplacian is, however, found to some extent. In conclusion, our study reveals the importance of the large-scale wind conditions in modulating the surface atmospheric response with different responses in the divergences of surface wind and wind stress.
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Butler, Bret, Steve Quarles, Christine Standohar-Alfano, Murray Morrison, Daniel Jimenez, Paul Sopko, Cyle Wold, et al. "Exploring fire response to high wind speeds: fire rate of spread, energy release and flame residence time from fires burned in pine needle beds under winds up to 27 ms−1." International Journal of Wildland Fire 29, no. 1 (2020): 81. http://dx.doi.org/10.1071/wf18216.
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The relationship between wildland fire spread rate and wind has been a topic of study for over a century, but few laboratory studies report measurements in controlled winds exceeding 5ms−1. In this study, measurements of fire rate of spread, flame residence time and energy release are reported for fires burning under controlled atmospheric conditions in shallow beds of pine needles subject to winds ranging from 0 to 27ms−1 (measured 5m above ground level). The data suggested that under constant flow conditions when winds are less than 10ms−1, fire rate of spread increases linearly at a rate of ~3% of the wind speed, which generally agrees with other laboratory-based models. When wind speed exceeds 10ms−1, the fire rate of spread response to wind remains linear but with a much stronger dependence, spreading at a rate of ~13% of the wind speed. Radiative and convective heating correlated directly to wind speed, with radiant heating increasing approximately three-fold as much as convective heating over the range of winds explored. The data suggested that residence time is inversely related to wind speed and appeared to approach a lower limit of ~20s as wind exceeded 15ms−1. Average flame residence time over the range of wind speeds was nominally 26s.
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Liu, Jing-Wu, Su-Ping Zhang, and Shang-Ping Xie. "Two Types of Surface Wind Response to the East China Sea Kuroshio Front*." Journal of Climate 26, no. 21 (October 16, 2013): 8616–27. http://dx.doi.org/10.1175/jcli-d-12-00092.1.
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Abstract Effects of the sea surface temperature (SST) front along the East China Sea Kuroshio on sea surface winds at different time scales are investigated. In winter and spring, the climatological vector wind is strongest on the SST front while the scalar wind speed reaches a maximum on the warm flank of the front and is collocated with the maximum difference between sea surface temperature and surface air temperature (SST − SAT). The distinction is due to the change in relative importance of two physical processes of SST–wind interaction at different time scales. The SST front–induced sea surface level pressure (SLP) adjustment (SF–SLP) contributes to a strong vector wind above the front on long time scales, consistent with the collocation of baroclinicity in the marine boundary layer and corroborated by the similarity between the thermal wind and observed wind shear between 1000 and 850 hPa. In contrast, the SST modulation of synoptic winds is more evident on the warm flank of the SST front. Large thermal instability of the near-surface layer strengthens temporal synoptic wind perturbations by intensifying vertical mixing, resulting in a scalar wind maximum. The vertical mixing and SF–SLP mechanisms are both at work but manifest more clearly at the synoptic time scale and in the long-term mean, respectively. The cross-frontal variations are 1.5 m s−1 in both the scalar and vector wind speeds, representing the vertical mixing and SF–SLP effects, respectively. The results illustrate the utility of high-frequency sampling by satellite scatterometers.
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Rafiq, Syeda, Charitha Pattiaratchi, and Ivica Janeković. "Dynamics of the Land–Sea Breeze System and the Surface Current Response in South-West Australia." Journal of Marine Science and Engineering 8, no. 11 (November 17, 2020): 931. http://dx.doi.org/10.3390/jmse8110931.
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The land–sea breeze (LSB) system, driven by the thermal contrast between the land and the adjacent ocean is a widely known atmospheric phenomenon, which occurs in coastal regions globally. South-west Australia experiences a persistent and one of the strongest LSB systems globally with maximum wind speeds associated with the LSB system often exceeding 15 ms−1. In this paper, using field measurements and numerical simulations, we examine: (1) the local winds associated with the land–sea breeze with an emphasis on the ocean; and, (2) the response of the surface currents to the diurnal wind forcing. The measurements indicated that the wind speeds decreased between midnight and 0400 and increased rapidly after 1100, reaching maxima >10 ms−1 around 1800) associated with the sea breeze and decreased to midnight. Wind directions were such that they were blowing from south-east (120°) in the morning and changed to almost southerly (~200°) in the afternoon. Decomposition of the wind record to the diurnal and synoptic components indicated that the diurnal component of winds (i.e., LSB) was oriented along the south-west to north-east axis. However, the stronger synoptic winds were from the south-east to south quadrant and in combination with the LSB, the winds consisted of a strong southerly component. We examined the evolution, horizontal extent, and propagation properties of sea breeze fronts for characteristic LSB cycles and the sea breeze cell propagating offshore and inland. The results indicated that the sea breeze cell was initiated in the morning in a small area, close to 33° S, 115.5° E, with a width of ~25 km and expanded onshore, offshore and alongshore. The sea breeze cell expanded faster (30 kmh−1) and farther (120 km) in the offshore direction than in the onshore direction (10 kmh−1 and 30–40 km). Winds during the LSB cycle followed a counterclockwise rotation that was also reflected in the surface currents. The winds and surface currents rotated anticlockwise with the surface currents responding almost instantaneously to changes in wind forcing but were modified by topography. The diurnal surface currents were enhanced due to the resonance between the LSB forcing and the inertial response.
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Yao, Zhuoer, Zi Kan, and Daochun Li. "Gust Response of Spanwise Morphing Wing by Simulation and Wind Tunnel Testing." Aerospace 10, no. 4 (March 24, 2023): 328. http://dx.doi.org/10.3390/aerospace10040328.
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The spanwise morphing wing can change its aerodynamic shape to suit its flight environment, thereby having the potential to improve the flight performance of the aircraft, especially in gusty conditions. To investigate the potential of morphing wings, the aerodynamic performance of a spanwise morphing wing with a flapping wingtip in a gust environment was analyzed in this paper. The aerodynamic characteristics of the morphing wing are hard to measure accurately, and thus a wind tunnel test was carried out to study the influences of morphing parameters, such as the morphing length, amplitude and frequency on the gust alleviation effect. The flow mechanism of the designed spanwise morphing wing was analyzed in detail by the instantaneous lift results of the wind tunnel test and the flow field results of the CFD method. The results have shown that with appropriate morphing parameters, the spanwise morphing wing designed in this paper can effectively achieve gust alleviation during flight. The conclusions obtained in this paper can be useful guidance for the design of morphing aircraft.
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McCracken, Gary F., Kamran Safi, Thomas H. Kunz, Dina K. N. Dechmann, Sharon M. Swartz, and Martin Wikelski. "Airplane tracking documents the fastest flight speeds recorded for bats." Royal Society Open Science 3, no. 11 (November 2016): 160398. http://dx.doi.org/10.1098/rsos.160398.
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The performance capabilities of flying animals reflect the interplay of biomechanical and physiological constraints and evolutionary innovation. Of the two extant groups of vertebrates that are capable of powered flight, birds are thought to fly more efficiently and faster than bats. However, fast-flying bat species that are adapted for flight in open airspace are similar in wing shape and appear to be similar in flight dynamics to fast-flying birds that exploit the same aerial niche. Here, we investigate flight behaviour in seven free-flying Brazilian free-tailed bats ( Tadarida brasiliensis ) and report that the maximum ground speeds achieved exceed speeds previously documented for any bat. Regional wind modelling indicates that bats adjusted flight speeds in response to winds by flying more slowly as wind support increased and flying faster when confronted with crosswinds, as demonstrated for insects, birds and other bats. Increased frequency of pauses in wing beats at faster speeds suggests that flap-gliding assists the bats' rapid flight. Our results suggest that flight performance in bats has been underappreciated and that functional differences in the flight abilities of birds and bats require re-evaluation.
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Sinha, Anirban, and Ryan P. Abernathey. "Time Scales of Southern Ocean Eddy Equilibration." Journal of Physical Oceanography 46, no. 9 (September 2016): 2785–805. http://dx.doi.org/10.1175/jpo-d-16-0041.1.
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AbstractStratification in the Southern Ocean is determined primarily by a competition between westerly wind-driven upwelling and baroclinic eddy transport. This study investigates the time scales of equilibration of the Southern Ocean in response to changing winds through an idealized channel model. An analytical framework describing the energetic pathways between wind input, available potential energy (APE), eddy kinetic energy (EKE), and dissipation provides a simple theory of the phase and amplitude response to oscillating wind stress. The transient ocean response to variable winds lies between the two limits of Ekman response (high frequency), characterized by the isopycnal slope responding directly to wind stress, and “eddy saturation” (low frequency), wherein a large fraction of the anomalous wind work goes into mesoscale eddies. The crossover time scale is the time scale of meridional eddy diffusive transport across the Antarctic Circumpolar Current (ACC) front. For wind variability with a period of 3 months (high-frequency forcing), the relative conversion of wind work to APE/EKE is 11, while for a period of 16 years (low-frequency forcing), the relative conversion to APE/EKE reduces to 3. The system’s frequency response is characterized by a complex transfer function. Both the phase and amplitude response of EKE and APE predicted by the linear analytic framework are verified using multiple ensemble experiments in an eddy-resolving (4-km horizontal resolution) isopycnal coordinate model. The results from the numerical experiments show agreement with the linear theory and can be used to explain certain features observed in previous modeling studies and observations.
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Perlin, Natalie, Simon P. de Szoeke, Dudley B. Chelton, Roger M. Samelson, Eric D. Skyllingstad, and Larry W. O’Neill. "Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature Perturbations." Monthly Weather Review 142, no. 11 (October 24, 2014): 4284–307. http://dx.doi.org/10.1175/mwr-d-13-00332.1.
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Abstract The wind speed response to mesoscale SST variability is investigated over the Agulhas Return Current region of the Southern Ocean using the Weather Research and Forecasting (WRF) Model and the U.S. Navy Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) atmospheric model. The SST-induced wind response is assessed from eight simulations with different subgrid-scale vertical mixing parameterizations, validated using Quick Scatterometer (QuikSCAT) winds and satellite-based sea surface temperature (SST) observations on 0.25° grids. The satellite data produce a coupling coefficient of sU = 0.42 m s−1 °C−1 for wind to mesoscale SST perturbations. The eight model configurations produce coupling coefficients varying from 0.31 to 0.56 m s−1 °C−1. Most closely matching QuikSCAT are a WRF simulation with the Grenier–Bretherton–McCaa (GBM) boundary layer mixing scheme (sU = 0.40 m s−1 °C−1), and a COAMPS simulation with a form of Mellor–Yamada parameterization (sU = 0.38 m s−1 °C−1). Model rankings based on coupling coefficients for wind stress, or for curl and divergence of vector winds and wind stress, are similar to that based on sU. In all simulations, the atmospheric potential temperature response to local SST variations decreases gradually with height throughout the boundary layer (0–1.5 km). In contrast, the wind speed response to local SST perturbations decreases rapidly with height to near zero at 150–300 m. The simulated wind speed coupling coefficient is found to correlate well with the height-averaged turbulent eddy viscosity coefficient. The details of the vertical structure of the eddy viscosity depend on both the absolute magnitude of local SST perturbations, and the orientation of the surface wind to the SST gradient.
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Downes, Stephanie M., Clothilde Langlais, Jordan P. Brook, and Paul Spence. "Regional Impacts of the Westerly Winds on Southern Ocean Mode and Intermediate Water Subduction." Journal of Physical Oceanography 47, no. 10 (October 2017): 2521–30. http://dx.doi.org/10.1175/jpo-d-17-0106.1.
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AbstractSubduction processes in the Southern Ocean transfer oxygen, heat, and anthropogenic carbon into the ocean interior. The future response of upper-ocean subduction, in the Subantarctic Mode Water (SAMW) and Antarctic Intermediate Water (AAIW) classes, is dependent on the evolution of the combined surface buoyancy forcing and overlying westerly wind stress. Here, the recently observed pattern of a poleward intensification of the westerly winds is divided into its shift and increase components. SAMW and AAIW formation occurs in regional “hot spots” in deep mixed layer zones, primarily in the southeast Indian and Pacific. It is found that the mixed layer depth responds differently to wind stress perturbations across these regional formation zones. An increase only in the westerly winds in the Indian sector steepens isopycnals and increases the local circulation, driving deeper mixed layers and increased subduction. Conversely, in the same region, a poleward shift and poleward intensification of the westerly winds reduces heat loss and increases freshwater input, thus decreasing the mixed layer depth and consequently the associated SAMW and AAIW subduction. In the Pacific sector, all wind stress perturbations lead to increases in heat loss and decreases in freshwater input, resulting in a net increase in SAMW and AAIW subduction. Overall, the poleward shift in the westerly wind stress dominates the SAMW subduction changes, rather than the increase in wind stress. The net decrease in SAMW subduction across all basins would likely decrease anthropogenic carbon sequestration; however, the net AAIW subduction changes across the Southern Ocean are overall minor.
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Chen, Gang, and Pablo Zurita-Gotor. "The Tropospheric Jet Response to Prescribed Zonal Forcing in an Idealized Atmospheric Model." Journal of the Atmospheric Sciences 65, no. 7 (July 1, 2008): 2254–71. http://dx.doi.org/10.1175/2007jas2589.1.
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Abstract This paper explores the tropospheric jet shift to a prescribed zonal torque in an idealized dry atmospheric model with high stratospheric resolution. The jet moves in opposite directions for torques on the jet’s equatorward and poleward flanks in the troposphere. This can be explained by considering how the critical latitudes for wave activity absorption change, where the eastward propagation speed of eddies equals the background zonal mean zonal wind. While the increased zonal winds in the subtropics allow the midlatitude eddies to propagate farther into the tropics and result in the equatorward shift in the critical latitudes, the increased winds in the midlatitudes accelerate the eastward eddy phase speeds and lead to the poleward shift in the critical latitudes. In contrast, the jet moves poleward when a westerly torque is placed in the extratropical stratosphere irrespective of the forcing latitude. The downward penetration of zonal winds to the troposphere displays a poleward slope for the subtropical torque, an equatorward slope for the high-latitude torque, and less tilting for the midlatitude torques. The stratospheric eddies play a key role in transferring zonal wind anomalies downward into the troposphere. It is argued that these stratospheric zonal wind anomalies can affect the tropospheric jet by altering the eastward propagation of tropospheric eddies. Additionally, the zonal wind response to a subtropical zonal torque in this idealized model is of value in understanding the tropospheric jet sensitivity to the orographic gravity wave drag parameterization in a realistic climate model.
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Zhu, Wen Qing, and Yang Yong Zhu. "The Vibration Response Analysis about High-Speed Train’s Braking Wing." Applied Mechanics and Materials 226-228 (November 2012): 102–5. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.102.
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With the rapid development of high-speed railway in China, the aerodynamic brake is very likely to be an important emergency braking mode of high-speed train in the future. This paper takes aerodynamic braking wing as the object, and uses the finite element software to divide the meshes, then analyses the model influenced by static stress. After simulating the vibratory frequency response of the model in the flow field, it finds that the largest deformation happens in the middle of the upper edge of the wind wing, when the wind speed gets to 500km/h and the load frequency to 4Hz. Some conclusions of this thesis can provide reference for researching the applying the aerodynamic brake in the high-speed trains and laying the foundation for solving the riding and braking safety problems.
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Carlsson, Martin. "Control Surface Response of a Blended Wing Body Aeroelastic Wind-Tunnel Model." Journal of Aircraft 42, no. 3 (May 2005): 738–42. http://dx.doi.org/10.2514/1.5440.
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Li, Bailiang, and Cheryl McKenna Neuman. "A wind tunnel study of aeolian sediment transport response to unsteady winds." Geomorphology 214 (June 2014): 261–69. http://dx.doi.org/10.1016/j.geomorph.2014.02.010.
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Moody, Matthew J., Jeremy A. Gibbs, Steven Krueger, Derek Mallia, Eric R. Pardyjak, Adam K. Kochanski, Brian N. Bailey, and Rob Stoll. "QES-Fire: a dynamically coupled fast-response wildfire model." International Journal of Wildland Fire 31, no. 3 (March 18, 2022): 306–25. http://dx.doi.org/10.1071/wf21057.
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A microscale wildfire model, QES-Fire, that dynamically couples the fire front to microscale winds was developed using a simplified physics rate of spread (ROS) model, a kinematic plume-rise model and a mass-consistent wind solver. The model is three-dimensional and couples fire heat fluxes to the wind field while being more computationally efficient than other coupled models. The plume-rise model calculates a potential velocity field scaled by the ROS model’s fire heat flux. Distinct plumes are merged using a multiscale plume-merging methodology that can efficiently represent complex fire fronts. The plume velocity is then superimposed on the ambient winds and the wind solver enforces conservation of mass on the combined field, which is then fed into the ROS model and iterated on until convergence. QES-Fire’s ability to represent plume rise is evaluated by comparing its results with those from an atmospheric large-eddy simulation (LES) model. Additionally, the model is compared with data from the FireFlux II field experiment. QES-Fire agrees well with both the LES and field experiment data, with domain-integrated buoyancy fluxes differing by less than 17% between LES and QES-Fire and less than a 10% difference in the ROS between QES-Fire and FireFlux II data.
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Solari, Giovanni. "Wind Response Spectrum." Journal of Engineering Mechanics 115, no. 9 (September 1989): 2057–73. http://dx.doi.org/10.1061/(asce)0733-9399(1989)115:9(2057).
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Fan, Weinan, Junxiang Liu, Wenxiong Mo, Le Luan, Yong Wang, and Zhong Xu. "Research on transient response of tower-line system under wind field based on finite element simulation." Journal of Physics: Conference Series 2360, no. 1 (November 1, 2022): 012043. http://dx.doi.org/10.1088/1742-6596/2360/1/012043.
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Most of the transmission poles and towers are built in the wild, and are often subjected to various loads such as wind, rain, ice and snow, especially the collapse of the tower caused by wind disasters. In order to study the response characteristics and disaster risk of towers under the wind field, this paper takes a 110kV transmission line as an example, and builds a “three towers and two lines” model based on ANSYS. Relevant specification parameters are calculated for the tower and conductor loads in this wind field, and the wind pressure time history is generated; based on the ANSYS transient analysis, the load wind pressure time history is used to analyze the dynamic response of the tower line, and the model is obtained in the static and dynamic wind field. Under the stress and displacement results, the response characteristics were analyzed. The research results can provide reference for tower design and line disaster prevention and mitigation.
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Joyce, Terrence M., Claude Frankignoul, Jiayan Yang, and Helen E. Phillips. "Ocean Response and Feedback to the SST Dipole in the Tropical Atlantic*." Journal of Physical Oceanography 34, no. 11 (November 1, 2004): 2525–40. http://dx.doi.org/10.1175/jpo2640.1.
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Abstract The equatorial SST dipole represents a mode of climate variability in the tropical Atlantic Ocean that is closely tied to cross-equatorial flow in the atmosphere, from the cold to the warm hemisphere. It has been suggested that this mode is sustained by a positive feedback of the tropical winds on the cross-equatorial SST gradient. The role, if any, of the tropical ocean is the focus of this investigation, which shows that at the latitudes of the SST signal (centered on 10°N/S) there is a weak positive feedback suggested in data from the last half century, that the cross-equatorial wind stress is closely coupled to this SST gradient on monthly time scales with no discernable lag, and that the period from January to June is the most active period for coupling. Northward (southward) anomalies of cross-equatorial wind stress are associated with a substantial negative (positive) wind stress curl. This wind system can thus drive a cross-equatorial Sverdrup transport in the ocean from the warm to the cold side of the equator (opposite the winds) with a temporal lag of only a few months. The oceanic observations of subsurface temperature and a numerical model hindcast also indicate a clear relationship between this mode of wind-driven variability and changes in the zonal transport of the North Equatorial Countercurrent. It is estimated that the time-dependent oceanic flow is capable of providing a significant contribution to the damping of the SST dipole but that external forcing is essential to sustaining the coupled variability.
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Hoffman, R. N., J. M. Henderson, S. M. Leidner, C. Grassotti, and T. Nehrkorn. "The Response of Damaging Winds of a Simulated Tropical Cyclone to Finite-Amplitude Perturbations of Different Variables." Journal of the Atmospheric Sciences 63, no. 7 (July 1, 2006): 1924–37. http://dx.doi.org/10.1175/jas3720.1.
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Abstract Four-dimensional variational data assimilation (4DVAR) is an established data assimilation method that finds the finite-amplitude perturbation that best fits observations consistent with a priori information and model dynamics. The response of a simulated tropical cyclone to specially designed finite perturbations of selected model variables was studied with a modified version of 4DVAR. The usual goal of minimizing data misfits was replaced with a goal of reducing damaging surface winds at the end of six hours of forecast time. For this purpose a property value cost function based on topography was defined. The case studied was a 20-km simulation of a hurricane approaching the Hawaiian Islands. Each prognostic variable in turn—temperature, winds, humidity, vertical velocity, and perturbation pressure—and all prognostic variables at once were used as the control vector for the optimization problem. Of all prognostic variables examined, temperature and the horizontal wind were the most effective at reducing damaging surface winds. The wind-only perturbation was very similar to the wind component of the perturbation calculated when all prognostic variables were used at once. Calculated perturbations had scales of 0.25°C or 1 m s−1, but changes at a few grid points near the center of the storm were an order of magnitude greater. Vertical velocity and humidity perturbations alone were ineffective at reducing damaging winds. The perturbation pressure experiment failed to converge but did substantially reduce the damaging winds.
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Marler, Thomas E., and Hiphil S. Clemente. "Papaya Seedling Growth Response to Wind and Water Deficit is Additive." HortScience 41, no. 1 (February 2006): 96–98. http://dx.doi.org/10.21273/hortsci.41.1.96.
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Trade winds occur throughout the year and drought occurs seasonally in many papaya (Carica papaya L.) production regions. We conducted four studies with `Known You 1' and `Sunrise' papaya seedlings to determine the combined influence of wind and water deficit on growth. We conducted three additional experiments to determine plant response to wind within a continuous dose range of 0 to 2.5 m·s–1. The main effects of wind and irrigation significantly reduced most response variables, such as dry weight components, leaf area, and height. However, the two factors acted independently of each other for every measure of plant growth. Thus, there was no departure from simple effects of an additive model for each main factor. The relationship between plant growth and wind between 0 and 2.5 m·s–1 could be described by a quadratic model. Results indicate that the influence of wind on plant growth cannot be studied without controlling or quantifying soil moisture among treatment groups. Practically, our results indicate that wind protection of young papaya plants may be warranted more so in the dry season than in the wet season or under sufficient irrigation practices.
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Amato, E. M., C. Polsinelli, E. Cestino, G. Frulla, N. Joseph, R. Carrese, and P. Marzocca. "HALE wing experiments and computational models to predict nonlinear flutter and dynamic response." Aeronautical Journal 123, no. 1264 (June 2019): 912–46. http://dx.doi.org/10.1017/aer.2019.38.
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AbstractExperimental and numerical investigations into the linear and nonlinear aeroelastic behaviour of very flexible High Altitude Long Endurance (HALE) wings are conducted to assess the effect of geometrical nonlinearities on wings displaying moderate-to-large displacement. The study shows that the dynamic behaviour of wings under large deflection, and specifically the edgewise and torsion natural frequencies and modal characteristics, are largely affected by the presence of geometrical nonlinearities. A modular wing structure has been manufactured by rapid prototyping and it has been tested to characterise its dynamic and aeroelastic behaviour. At first, several simple isotropic cantilever beams with selected crosssections are numerically investigated to extract their modal characteristics. Experiments are subsequently conducted to validate the geometrically nonlinear dynamics behaviour due to high tip displacement and to understand the influence of the beam cross-section geometry. The structural dynamics and aeroelastic analysis of a very flexible modular selected wing is then investigated. Clean-wing wind-tunnel tests are carried out to assess flutter and dynamic response. The wind-tunnel model display interesting aeroelastic features including the substantial influence of the wing large deformation on its natural frequencies and modal characteristics.
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Lemmin, U., and N. D'Adamo. "Summertime winds and direct cyclonic circulation: observations from Lake Geneva." Annales Geophysicae 14, no. 11 (November 30, 1996): 1207–20. http://dx.doi.org/10.1007/s00585-996-1207-z.
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Abstract. Records of wind, air temperature and air pressure from nine stations, situated along the shoreline of Lake Geneva, Switzerland, were analyzed for the summer period May to September. At all stations the consistent appearance of significant spectral peaks and changes in wind direction at the diurnal frequency indicates the importance of lake-land breezes. It is shown that the surrounding topography has a strong modifying effect (temporal and spatial) on the lake-land breeze. Superimposed on this cyclic wind pattern, short episodes of strong winds with long fetch over parts of Lake Geneva are regularly observed. Both of these winds exert a spatially variable wind stress over the lake surface on the same time scale. Typical examples of the expected lake's response are presented, among them the seasonally persistent gyre in the central part of the lake. Evidence is provided that this dominant circulation is part of a direct cyclonic circulation, generated by the curl of the diurnal wind field. It is concluded that the mean circulation is caused by these winds and affected by the topography of the surrounding land.
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Boos, William R., and Kerry A. Emanuel. "Wind–Evaporation Feedback and Abrupt Seasonal Transitions of Weak, Axisymmetric Hadley Circulations." Journal of the Atmospheric Sciences 65, no. 7 (July 1, 2008): 2194–214. http://dx.doi.org/10.1175/2007jas2608.1.
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Abstract For an imposed thermal forcing localized off the equator, it is known that conservation of absolute angular momentum in axisymmetric flow produces a nonlinear response once the forcing exceeds a critical amplitude. It is shown here that, for a moist atmosphere in convective quasi-equilibrium, the combination of wind-dependent ocean surface enthalpy fluxes and zonal momentum advection can provide a separate feedback that causes the meridional flow to evolve nonlinearly as a function of a sea surface temperature (SST) forcing, even if an angular momentum–conserving response is not achieved. This wind–evaporation feedback is examined in both an axisymmetric primitive equation model and a simple model that retains only a barotropic and single baroclinic mode. Only SST forcings that do not produce an angular momentum–conserving response are examined here. The wind–evaporation feedback is found to be inhibited in models with linear dynamics because the barotropic component of the Hadley circulation, which is coupled to the baroclinic circulation via surface drag, keeps surface winds small compared to upper-level winds. In models with nonlinear dynamics, the convergence of zonal momentum into the ascending branch of the cross-equatorial Hadley cell can create barotropic westerlies that constructively add to the baroclinic wind at the surface, thereby eliminating the inhibition of the wind–evaporation feedback. The possible relevance of these results to the onset of monsoons is discussed.
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Hlywiak, James, and David S. Nolan. "The Response of the Near-Surface Tropical Cyclone Wind Field to Inland Surface Roughness Length and Soil Moisture Content during and after Landfall." Journal of the Atmospheric Sciences 78, no. 3 (March 2021): 983–1000. http://dx.doi.org/10.1175/jas-d-20-0211.1.
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AbstractThe sensitivity of the inland wind decay to realistic inland surface roughness lengths and soil moisture contents is evaluated for strong, idealized tropical cyclones (TCs) of category 4 strength making landfall. Results show that the relative sensitivities to roughness and moisture differ throughout the decay process, and are dependent on the strength and size of the vortex. First, within 12 h of landfall, intense winds at the surface decay rapidly in reaction to the sudden change in surface roughness and decreasing enthalpy fluxes. Wind speeds above the boundary layer decay at a slower rate. Differences in soil moisture contents minimally affect intensity during the first 12 h, as the enhancement of latent heat fluxes from high moisture contents is countered by enhanced surface cooling. After TCs decay to tropical storm intensities, weakening slows and the sensitivity of the intensity decay to soil moisture increases. Increased latent heating becomes significant enough to combat surface temperature cooling, resulting in enhanced convection outside of the expanding radius of maximum winds. This supports a slower decay. Additionally, the decay of the radial wind profile by quadrant is highly asymmetric, as the rear and left-of-motion quadrants decay the fastest. Increasing surface roughness accelerates the decay of the strongest winds, while increasing soil moisture slows the decay of the larger TC wind field. Results have implications for inland forecasting of TC winds and understanding the potential for damage.
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Xu, Qin, Li Wei, Kang Nai, Shun Liu, Robert M. Rabin, and Qingyun Zhao. "A Radar Wind Analysis System for Nowcast Applications." Advances in Meteorology 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/264515.
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A radar wind analysis system (RWAS) has been developed for nowcast applications. By ingesting real-time wind observations from operational WSR-88D radars and surface mesonet, this system can produce and display real-time vector winds at each selected vertical level or on each conical surface of radar scans superimposed on radar reflectivity or radial-velocity images. An early version of the system has been evaluated and used to provide real-time winds to drive high-resolution emergency response dispersion models. This paper presents the detailed formulations of background error correlation functions used in each of the three steps of vector wind analysis performed in the RWAS and the method of solution used in each step of vector wind analysis. The performances of the RWAS are demonstrated by illustrative examples.
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Malki, Khalifa, Aziza Bounhir, Zouhair Benkhaldoun, Jonathan J. Makela, Nicole Vilmer, Daniel J. Fisher, Mohamed Kaab, et al. "Ionospheric and thermospheric response to the 27–28 February 2014 geomagnetic storm over north Africa." Annales Geophysicae 36, no. 4 (July 12, 2018): 987–98. http://dx.doi.org/10.5194/angeo-36-987-2018.
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Abstract. The present work explores the ionospheric and thermospheric responses to the 27–28 February 2014 geomagnetic storm. For the first time, a geomagnetic storm is explored in north Africa using interferometer, all-sky imager and GPS data. This storm was due to the arrival at the Earth of the shock of a coronal mass ejection (CME) associated with the solar flare event on 25 February 2014. A Fabry–Perot interferometer located at the Oukaïmeden Observatory (31.206° N, 7.866° W; 22.84° N magnetic) in Morocco provides measurements of the thermospheric neutral winds based on observations of the 630 nm red line emission. A wide-angle imaging system records images of the 630 nm emission. The effects of this geomagnetic storm on the thermosphere are evident from the clear departure of the neutral winds from their seasonal behavior. During the storm, the winds experience an intense and steep equatorward flow from 21:00 to 01:00 LT and a westward flow from 22:00 to 03:00 LT. The equatorial wind speed reaches a maximum of 120 m s−1 for the meridional component at 22:00 LT, after the zonal wind reverses to the westward direction. Shortly after 00:00 LT a maximum westward speed of 80 m s−1 was achieved for the zonal component of the wind. The features of the winds are typical of traveling atmospheric disturbance (TAD)-induced circulation; the first TAD coming from the Northern Hemisphere reaches the site at 21:00 LT and a second one coming from the Southern Hemisphere reaches the site at about 00:00 LT. We estimate the propagation speed of the northern TAD to be 550 m s−1. We compared the winds to the DWM07 (Disturbance Wind Model) prediction model and find that this model gives a good indication of the new circulation pattern caused by storm activity, but deviates largely inside the TADs. The effects on the ionosphere were also evident through the change observed in the background electrodynamics from the reversal in the drift direction in an observed equatorial plasma bubble (EPB). Total electron content (TEC) measurements of a GPS station installed in Morocco, at Rabat (33.998° N, 6.853° W), revealed a positive storm.
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Feng, Zhihui, Tao Li, Lei Zheng, and Jian Li. "Numerical Simulation of Wind-induced Swing Angle of 1000kV Transmission Line Suspension Insulator Strings Considering Dynamic Response." Journal of Physics: Conference Series 2237, no. 1 (March 1, 2022): 012001. http://dx.doi.org/10.1088/1742-6596/2237/1/012001.
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Abstract The wind-induced swing angle of insulator strings directly affects the electrical insulation performance and the construction cost of the UHV transmission project. However, due to not considering the fluctuating wind pressure, the calculation results of wind-induced swing tend to be conservative when adopting the recommended guidelines of standard especially in the face of severe weather. This paper simulates the transient wind field of strong winds based on time-space correlation characteristics and constructs the fluctuating wind load distribution model exerting on the UHV transmission line. Then a refined finite element model of the multi-span transmission line including the entire tensile section is established. And the swing angle of the insulator strings calculation formula is fitted based on the calculation results of the wind-induced swing response. The calculation result shows the swing angle decreases with the increase of ice thickness, and the magnified coefficient of the wind-induced swing angle at the target tower under the basic wind speed of 15m/s is 1.03.
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Dai, Yuting, and Chao Yang. "GPC-Based Gust Response Alleviation for Aircraft Model Adapting to Various Flow Velocities in the Wind Tunnel." Shock and Vibration 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/348971.
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A unified autoregressive (AR) model is identified, based on the wind tunnel test data of open-loop gust response for an aircraft model. The identified AR model can be adapted to various flow velocities in the wind tunnel test. Due to the lack of discrete gust input measurement, a second-order polynomial function is used to approximate the gust input amplitude by flow velocity. Afterwards, with the identified online aeroelastic model, the modified generalized predictive control (GPC) theory is applied to alleviate wing tip acceleration induced by sinusoidal gust. Finally, the alleviation effects of gust response at different flow velocities are estimated based on the comparison of simulated closed-loop acceleration with experimental open-loop one. The comparison indicates that, after gust response alleviation, the wing tip acceleration can be reduced up to 20% at the tested velocities ranging from 12 m/s to 24 m/s. Demonstratively, the unified control law can be adapted to varying wind tunnel velocities and gust frequencies. It does not need to be altered at different test conditions, which will save the idle time.
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Parkhomov, Vladimir, Viktor Eselevich, Maxim Eselevich, Aleksey Dmitriev, Alla Suvorova, and Tatyana Vedernikova. "CLASSIFICATION OF MAGNETOSPHERIC RESPONSES TO INTERACTION WITH DIAMAGNETIC STRUCTURES OF SLOW SOLAR WIND." Solar-Terrestrial Physics 6, no. 4 (December 22, 2020): 24–36. http://dx.doi.org/10.12737/stp-64202004.
Full textAbstract:
We propose a possible classification of the responses of the magnetosphere to the interaction with diamagnetic structures (DS), which form the basis of the slow solar wind. The main determinants of the classification are the value and orientation of the vertical component Bz of the interplanetary magnetic field (IMF) and the solar wind density N. We have identified three types of magnetospheric responses. Type 1 has two subtypes whose main difference is the presence or absence of auroras on the day side of the magnetosphere. Within an hour before DS arrival, Bz has a positive value (up to 12 nT) or fluctuates about 0 in the range from –1 to +1 nT. For both subtypes, the duration of substorm disturbances approximately coincides with the duration of DS, and their intensity does not exceed AE~500 nT. Type 2 is characterized by the fact that before the contact with DS positive IMF Bz (0–10 nT) is recorded for an hour, and at the interface of DS a rapid (≤2 min) change in the orientation of the IMF vertical component from north to south occurs. For type 3, Bz within an hour before the contact with DS is negative (from –10 to 0 nT).
We address the problem of DS energy transfer to the magnetosphere.
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Lundesgaard, Øyvind, Brian Powell, Mark Merrifield, Lisa Hahn-Woernle, and Peter Winsor. "Response of an Antarctic Peninsula Fjord to Summer Katabatic Wind Events." Journal of Physical Oceanography 49, no. 6 (June 2019): 1485–502. http://dx.doi.org/10.1175/jpo-d-18-0119.1.
Full textAbstract:
AbstractFjords along the western Antarctic Peninsula are episodically exposed to strong winds flowing down marine-terminating glaciers and out over the ocean. These wind events could potentially be an important mechanism for the ventilation of fjord waters. A strong wind event was observed in Andvord Bay in December 2015, and was associated with significant increases in upper-ocean salinity. We examine the dynamical impacts of such wind events during the ice-free summer season using a numerical model. Passive tracers are used to identify water mass pathways and quantify exchange with the outer ocean. Upwelling and outflow in the model fjord generate an average salinity increase of 0.3 in the upper ocean during the event, similar to observations from Andvord Bay. Down-fjord wind events are a highly efficient mechanism for flushing out the upper fjord waters, but have little net impact on deep waters in the inner fjord. As such, summer episodic wind events likely have a large effect on fjord phytoplankton dynamics and export of glacially modified upper waters, but are an unlikely mechanism for the replenishment of deep basin waters and oceanic heat transport toward inner-fjord glaciers.
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IZUMIYA, Takashi, Chiemi YUJIMA, and Kunihiko ISHIBASHI. "Experiments on Drag Coefficients and Response of Wind Waves to Periodically Fluctuating Winds." PROCEEDINGS OF COASTAL ENGINEERING, JSCE 54 (2007): 41–45. http://dx.doi.org/10.2208/proce1989.54.41.
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