Zeitschriftenartikel zum Thema „Vertical velocities“
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Vélez-Belchí, Pedro, und Joaquín Tintoré. „Vertical velocities at an ocean front“. Scientia Marina 65, S1 (30.07.2001): 291–300. http://dx.doi.org/10.3989/scimar.2001.65s1291.
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Frajka-Williams, Eleanor, Charles C. Eriksen, Peter B. Rhines und Ramsey R. Harcourt. „Determining Vertical Water Velocities from Seaglider“. Journal of Atmospheric and Oceanic Technology 28, Nr. 12 (01.12.2011): 1641–56. http://dx.doi.org/10.1175/2011jtecho830.1.
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Abstract Vertical velocities in the world’s oceans are typically small, less than 1 cm s−1, posing a significant challenge for observational techniques. Seaglider, an autonomous profiling instrument, can be used to estimate vertical water velocity in the ocean. Using a Seaglider’s flight model and pressure observations, vertical water velocities are estimated along glider trajectories in the Labrador Sea before, during, and after deep convection. Results indicate that vertical velocities in the stratified ocean agree with the theoretical Wentzel–Kramers–Brillouin (WKB) scaling of w; and in the turbulent mixed layer, scale with buoyancy, and wind forcing. It is estimated that accuracy is to within 0.5 cm s−1. Because of uncertainties in the flight model, velocities are poor near the surface and deep apogees, and during extended roll maneuvers. Some of this may be improved by using a dynamic flight model permitting acceleration and by better constraining flight parameters through pilot choices during the mission.
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Merckelbach, Lucas, David Smeed und Gwyn Griffiths. „Vertical Water Velocities from Underwater Gliders“. Journal of Atmospheric and Oceanic Technology 27, Nr. 3 (01.03.2010): 547–63. http://dx.doi.org/10.1175/2009jtecho710.1.
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Abstract The underwater glider is set to become an important platform for oceanographers to gather data within oceans. Gliders are usually equipped with a conductivity–temperature–depth (CTD) sensor, but a wide range of other sensors have been fitted to gliders. In the present work, the authors aim at measuring the vertical water velocity. The vertical water velocity is obtained by subtracting the vertical glider velocity relative to the water from the vertical glider velocity relative to the water surface. The latter is obtained from the pressure sensor. For the former, a quasi-static model of planar glider flight is developed. The model requires three calibration parameters, the (parasite) drag coefficient, glider volume (at atmospheric pressure), and hull compressibility, which are found by minimizing a cost function based on the variance of the calculated vertical water velocity. Vertical water velocities have been calculated from data gathered in the northwestern Mediterranean during the Gulf of Lions experiment, winter 2008. Although no direct comparison could be made with water velocities from an independent measurement technique, the authors show that, for two different heat loss regimes (≈0 and ≈400 W m−2), the calculated vertical velocity scales are comparable with those expected for internal waves and active open ocean convection, respectively. High noise levels resulting from the pressure sensor require the water velocity time series to be low-pass filtered with a cutoff period of 80 s. The absolute accuracy of the vertical water velocity is estimated at ±4 mm s−1.
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Rao, P. V., P. Vinay Kumar, M. C. Ajay Kumar und G. Dutta. „Long-term mean vertical velocity measured by MST radar at Gadanki (13.5° N, 79.2° E)“. Annales Geophysicae 27, Nr. 2 (02.02.2009): 451–59. http://dx.doi.org/10.5194/angeo-27-451-2009.
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Abstract. MST radars are capable of measuring vertical motion along a vertically directed beam. We present 8 years (1995–2003) averaged profile of vertical velocity in the troposphere and the lower stratosphere over Gadanki (13.5° N, 79.2° E), a tropical station. A downward mid-tropospheric w is observed with a reversal of sign around 10 km and a further reversal can also be seen at ~17 km. A significant diurnal and semidiurnal variation in vertical wind is observed for all heights with subsidence during the evening hours. Seasonal variability of vertical wind is also found to be quite appreciable. Vertical velocities have been derived using symmetric pairs of off-vertical beams and a comparison has been made with direct vertical beam measurements. Vertical components estimated from E-W and N-S radial velocities do not match and are also found to have discrepancy with direct measurements. Plausible causes of the discrepancy have been investigated with the help of some case studies. Vertical shear in horizontal wind, gradients in horizontal velocities and echo power imbalance may be some of the factors responsible for the observed discrepancy.
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Donner, Leo J., Travis A. O'Brien, Daniel Rieger, Bernhard Vogel und William F. Cooke. „Are atmospheric updrafts a key to unlocking climate forcing and sensitivity?“ Atmospheric Chemistry and Physics 16, Nr. 20 (20.10.2016): 12983–92. http://dx.doi.org/10.5194/acp-16-12983-2016.
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Abstract. Both climate forcing and climate sensitivity persist as stubborn uncertainties limiting the extent to which climate models can provide actionable scientific scenarios for climate change. A key, explicit control on cloud–aerosol interactions, the largest uncertainty in climate forcing, is the vertical velocity of cloud-scale updrafts. Model-based studies of climate sensitivity indicate that convective entrainment, which is closely related to updraft speeds, is an important control on climate sensitivity. Updraft vertical velocities also drive many physical processes essential to numerical weather prediction.Vertical velocities and their role in atmospheric physical processes have been given very limited attention in models for climate and numerical weather prediction. The relevant physical scales range down to tens of meters and are thus frequently sub-grid and require parameterization. Many state-of-science convection parameterizations provide mass fluxes without specifying vertical velocities, and parameterizations that do provide vertical velocities have been subject to limited evaluation against what have until recently been scant observations. Atmospheric observations imply that the distribution of vertical velocities depends on the areas over which the vertical velocities are averaged. Distributions of vertical velocities in climate models may capture this behavior, but it has not been accounted for when parameterizing cloud and precipitation processes in current models.New observations of convective vertical velocities offer a potentially promising path toward developing process-level cloud models and parameterizations for climate and numerical weather prediction. Taking account of the scale dependence of resolved vertical velocities offers a path to matching cloud-scale physical processes and their driving dynamics more realistically, with a prospect of reduced uncertainty in both climate forcing and sensitivity.
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Gudadze, Nikoloz, Gunter Stober und Jorge L. Chau. „Can VHF radars at polar latitudes measure mean vertical winds in the presence of PMSE?“ Atmospheric Chemistry and Physics 19, Nr. 7 (05.04.2019): 4485–97. http://dx.doi.org/10.5194/acp-19-4485-2019.
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Abstract. Mean vertical velocity measurements obtained from radars at polar latitudes using polar mesosphere summer echoes (PMSEs) as an inert tracer have been considered to be non-representative of the mean vertical winds over the last couple of decades. We used PMSEs observed with the Middle Atmosphere Alomar Radar System (MAARSY) over Andøya, Norway (69.30∘ N, 16.04∘ E), during summers of 2016 and 2017 to derive mean vertical winds in the upper mesosphere. The 3-D vector wind components (zonal, meridional and vertical) are based on a Doppler beam swinging experiment using five beam directions (one vertical and four oblique). The 3-D wind components are computed using a recently developed wind retrieval technique. The method includes full non-linear error propagation, spatial and temporal regularisation, and beam pointing corrections and angular pointing uncertainties. Measurement uncertainties are used as weights to obtain seasonal weighted averages and characterise seasonal mean vertical velocities. Weighted average values of vertical velocities reveal a weak upward behaviour at altitudes ∼84–87 km after eliminating the influence of the speed of falling ice. At the same time, a sharp decrease (increase) in the mean vertical velocities at the lower (upper) edges of the summer mean altitude profile, which are attributed to the sampling issues of the PMSE due to disappearance of the target corresponding to the certain regions of motions and temperatures, prevails. Thus the mean vertical velocities can be biased downwards at the lower edge, and the mean vertical velocities can be biased upwards at the upper edge, while at the main central region the obtained mean vertical velocities are consistent with expected upward values of mean vertical winds after considering ice particle sedimentation.
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Yi, Zhang, und Oddbj�rn Engvold. „Vertical velocities and oscillations in quiescent filaments“. Solar Physics 134, Nr. 2 (August 1991): 275–86. http://dx.doi.org/10.1007/bf00152648.
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Sévellec, F., A. C. Naveira Garabato, J. A. Brearley und K. L. Sheen. „Vertical Flow in the Southern Ocean Estimated from Individual Moorings“. Journal of Physical Oceanography 45, Nr. 9 (September 2015): 2209–20. http://dx.doi.org/10.1175/jpo-d-14-0065.1.
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AbstractThis study demonstrates that oceanic vertical velocities can be estimated from individual mooring measurements, even for nonstationary flow. This result is obtained under three assumptions: (i) weak diffusion (Péclet number ≫ 1), (ii) weak friction (Reynolds number ≫ 1), and (iii) small inertial terms (Rossby number ≪ 1). The theoretical framework is applied to a set of four moorings located in the Southern Ocean. For this site, the diagnosed vertical velocities are highly variable in time, their standard deviation being one to two orders of magnitude greater than their mean. The time-averaged vertical velocities are demonstrated to be largely induced by geostrophic flow and can be estimated from the time-averaged density and horizontal velocities. This suggests that local time-mean vertical velocities are primarily forced by the time-mean ocean dynamics, rather than by, for example, transient eddies or internal waves. It is also shown that, in the context of these four moorings, the time-mean vertical flow is consistent with stratified Taylor column dynamics in the presence of a topographic obstacle.
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Hoppe, C. M., F. Ploeger, P. Konopka und R. Müller. „Kinematic and diabatic vertical velocity climatologies from a chemistry climate model“. Atmospheric Chemistry and Physics Discussions 15, Nr. 21 (02.11.2015): 29939–71. http://dx.doi.org/10.5194/acpd-15-29939-2015.
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Abstract. The representation of vertical velocity in chemistry climate models is a key element for the representation of the large scale Brewer–Dobson-Circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic vertical velocities in the ECHAM/Messy Atmospheric Chemistry (EMAC) model. The calculation of kinematic vertical velocity is based on the continuity equation, whereas diabatic vertical velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of vertical velocity from a 10 year simulation are provided for both, kinematic and diabatic vertical velocity representations. In general, both vertical velocity patterns show the main features of the stratospheric circulation, namely upwelling at low latitudes and downwelling at high latitudes. The main difference in the vertical velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic vertical velocity. Diabatic vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two vertical velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different vertical velocities. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic vertical velocities. Further, the age of air climatology from the transport scheme using diabatic vertical velocities shows younger mean age of air in the inner tropical upwelling branch and older mean age in the extratopical tropopause region.
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Hoppe, Charlotte Marinke, Felix Ploeger, Paul Konopka und Rolf Müller. „Kinematic and diabatic vertical velocity climatologies from a chemistry climate model“. Atmospheric Chemistry and Physics 16, Nr. 10 (23.05.2016): 6223–39. http://dx.doi.org/10.5194/acp-16-6223-2016.
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Abstract. The representation of vertical velocity in chemistry climate models is a key element for the representation of the large-scale Brewer–Dobson circulation in the stratosphere. Here, we diagnose and compare the kinematic and diabatic vertical velocities in the ECHAM/Modular Earth Submodel System (MESSy) Atmospheric Chemistry (EMAC) model. The calculation of kinematic vertical velocity is based on the continuity equation, whereas diabatic vertical velocity is computed using diabatic heating rates. Annual and monthly zonal mean climatologies of vertical velocity from a 10-year simulation are provided for both kinematic and diabatic vertical velocity representations. In general, both vertical velocity patterns show the main features of the stratospheric circulation, namely, upwelling at low latitudes and downwelling at high latitudes. The main difference in the vertical velocity pattern is a more uniform structure for diabatic and a noisier structure for kinematic vertical velocity. Diabatic vertical velocities show higher absolute values both in the upwelling branch in the inner tropics and in the downwelling regions in the polar vortices. Further, there is a latitudinal shift of the tropical upwelling branch in boreal summer between the two vertical velocity representations with the tropical upwelling region in the diabatic representation shifted southward compared to the kinematic case. Furthermore, we present mean age of air climatologies from two transport schemes in EMAC using these different vertical velocities and analyze the impact of residual circulation and mixing processes on the age of air. The age of air distributions show a hemispheric difference pattern in the stratosphere with younger air in the Southern Hemisphere and older air in the Northern Hemisphere using the transport scheme with diabatic vertical velocities. Further, the age of air climatology from the transport scheme using diabatic vertical velocities shows a younger mean age of air in the inner tropical upwelling branch and an older mean age in the extratropical tropopause region.
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Patara, L., N. Pinardi, C. Corselli, E. Malinverno, M. Tonani, R. Santoleri und S. Masina. „Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities“. Biogeosciences Discussions 5, Nr. 4 (12.08.2008): 3123–56. http://dx.doi.org/10.5194/bgd-5-3123-2008.
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Abstract. This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are higher than 200 m day−1. The current vertical velocity field is computed from a high resolution Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day−1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However, we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. By analyzing the delayed effects of ocean vertical velocities on deep particle fluxes we envisage a spectrum of particle sinking speeds ranging from about 100 m day−1 to more than 200 m day−1. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.
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Reeh, Niels, Johan Jacob Mohr, Søren Nørvang Madsen, Hans Oerter und Niels S. Gundestrup. „Three-dimensional surface velocities of Storstrømmen glacier, Greenland, derived from radar interferometry and ice-sounding radar measurements“. Journal of Glaciology 49, Nr. 165 (2003): 201–9. http://dx.doi.org/10.3189/172756503781830818.
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AbstractNon-steady-state vertical velocities of up to 5 m a−1 exceed the vertical surface-parallel flow (SPF) components over much of the ablation area of Storstrømmen, a large outlet glacier from the East Greenland ice sheet. Neglecting a contribution to the vertical velocity of this magnitude results in substantial errors (up to 20%) also on the south–north component of horizontal velocities derived by satellite synthetic aperture radar interferometry (InSAR) measurements. In many glacier environments, the steady-state vertical velocity component required to balance the annual ablation rate is 5–10 m a−1 or more. This indicates that the SPF assumption may be problematic also for glaciers in steady state. Here we derive the three-dimensional surface velocity distribution of Storstrømmen by using the principle of mass conservation (MC) to combine InSAR measurements from ascending and descending satellite tracks with airborne ice-sounding radar measurement of ice thickness. The results are compared to InSAR velocities previously derived by using the SPF assumption, and to velocities obtained by in situ global positioning system (GPS) measurements. The velocities derived by using the MC principle are in better agreement with the GPS velocities than the previously calculated velocities derived with the SPF assumption.
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Medvedev, Andrey V., Konstantin G. Ratovsky, Maxim V. Tolstikov, Roman V. Vasilyev und Maxim F. Artamonov. „Method for Determining Neutral Wind Velocity Vectors Using Measurements of Internal Gravity Wave Group and Phase Velocities“. Atmosphere 10, Nr. 9 (13.09.2019): 546. http://dx.doi.org/10.3390/atmos10090546.
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This study presents a new method for determining a neutral wind velocity vector. The basis of the method is measurement of the group velocities of internal gravity waves. Using the case of the Boussinesq dispersion relation, we demonstrated the ability to measure a neutral wind velocity vector using the group velocity and wave vector data. An algorithm for obtaining the group velocity vector from the wave vector spectrum is proposed. The new method was tested by comparing the obtained winter wind pattern with wind data from other sources. Testing the new method showed that it is in quantitative agreement with the Fabry–Pérot interferometer wind measurements for zonal and vertical wind velocities. The differences in meridional wind velocities are also discussed here. Of particular interest were the results related to the measurement of vertical wind velocities. We demonstrated that two independent methods gave the presence of vertical wind velocities with amplitude of ~20 m/s. Estimation of vertical wind contribution to plasma drift velocity indicated the importance of vertical wind measurements and the need to take them into account in physical and empirical models of the ionosphere and thermosphere.
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Dutta, Troyee Tanu, Masahide Otsubo, Reiko Kuwano und Takeshi Sato. „Development of vertical and horizontal disk transducers for wave velocity measurements in a large rectangular specimen“. E3S Web of Conferences 92 (2019): 02001. http://dx.doi.org/10.1051/e3sconf/20199202001.
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For the accurate design of structures subjected to both static and dynamic loadings, elastic wave velocity and small strain stiffness are essential parameters. Numerous techniques have been developed to estimate wave velocities of geomaterials. Bender elements which are widely adopted for wave velocity measurements are invasive in nature and are not suitable for coarse-grained materials. In the present study, new design configuration of disk transducer has been introduced to measure both vertical and horizontal wave velocities for coarse granular soils considering multidirectional oscillation of propagating waves. An innovative arrangement of both compression and shear type elements has been installed in a large-sized triaxial apparatus having rectangular specimens of size 236×236×500 mm to assess the wave velocities. The materials described are Toyoura sand (D50 = 0.24 mm) and Oiso gravel (D50 = 11.8 mm). This arrangement enables measurements of nine types of wave velocities, and thus the stiffness anisotropy to be quantified. For Oiso gravel, horizontal wave velocities are greater than vertical wave velocities for both shear and compression waves. For Toyoura sand, shear wave velocities are higher in horizontal direction of propagation, whereas similar compression wave velocities are observed from both horizontal and vertical directions.
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Rudenko, S., N. Schön, M. Uhlemann und G. Gendt. „Reprocessed height time series for GPS stations“. Solid Earth 4, Nr. 1 (24.01.2013): 23–41. http://dx.doi.org/10.5194/se-4-23-2013.
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Abstract. Precise weekly positions of 403 Global Positioning System (GPS) stations located worldwide are obtained by reprocessing GPS data of these stations for the time span from 4 January 1998 until 29 December 2007. The processing algorithms and models used as well as the solution and results obtained are presented. Vertical velocities of 266 GPS stations having a tracking history longer than 2.5 yr are computed; 107 of them are GPS stations located at tide gauges (TIGA observing stations). The vertical velocities calculated in this study are compared with the estimates from the co-located tide gauges and other GPS solutions. The formal errors of the estimated vertical velocities are 0.01–0.80 mm yr−1. The vertical velocities of our solution agree within 1 mm yr−1 with those of the recent solutions (ULR5 and ULR3) of the Université de La Rochelle for about 67–75 per cent of the common stations. Examples of typical behaviour of station height changes are given and interpreted. The derived height time series and vertical motions of continuous GPS at tide gauges stations can be used for correcting the vertical land motion in tide gauge records of sea level changes.
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Sankin, Vladimir Ilich, und Alla A. Lepneva. „Electron Saturated Vertical Velocities in Silicon Carbide Polytypes“. Materials Science Forum 338-342 (Mai 2000): 769–72. http://dx.doi.org/10.4028/www.scientific.net/msf.338-342.769.
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Bishop, R. L., G. D. Earle, S. A. Gonzalez, M. P. Sulzer und S. C. Collins. „Inferred vertical ion velocities associated with intermediate layers“. Journal of Atmospheric and Solar-Terrestrial Physics 64, Nr. 12-14 (August 2002): 1471–77. http://dx.doi.org/10.1016/s1364-6826(02)00111-6.
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Hughes, Steven A. „Estimating Wave‐Induced Bottom Velocities at Vertical Wall“. Journal of Waterway, Port, Coastal, and Ocean Engineering 118, Nr. 2 (März 1992): 175–92. http://dx.doi.org/10.1061/(asce)0733-950x(1992)118:2(175).
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Patara, L., N. Pinardi, C. Corselli, E. Malinverno, M. Tonani, R. Santoleri und S. Masina. „Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities“. Biogeosciences 6, Nr. 3 (06.03.2009): 333–48. http://dx.doi.org/10.5194/bg-6-333-2009.
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Abstract. This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are more than 200 m day−1. The current vertical velocity field is computed from a 1/16°×1/16° Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day−1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.
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Barceló-Llull, B., E. Mason und A. Pascual. „Impact of vertical and horizontal advection on nutrient distribution in the South East Pacific“. Ocean Science Discussions 12, Nr. 5 (29.09.2015): 2257–81. http://dx.doi.org/10.5194/osd-12-2257-2015.
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Abstract. An innovative approach is used to analyse the impact of vertical velocities associated with quasi-geostrophic (QG) dynamics on the distribution of a passive nutrient tracer (nitrate) in the South East Pacific. Twelve years of vertical and horizontal currents are derived from an observation-based estimate of the ocean state. Horizontal velocities are obtained through application of thermal wind balance to weekly temperature and salinity fields. Vertical velocities are estimated by integration of the QG Omega equation. Seasonal variability of the synthetic vertical velocity and kinetic energy associated with the horizontal currents are coincident, with peaks in austral summer (November–December) in accord with published observations. Two ensembles of Lagrangian particle tracking experiments that differ according to vertical forcing (w = wQG vs. w = 0) enable a quantitative analysis of the impact of the vertical velocity. From identical initial distributions of nitrate-tagged particles, the Lagrangian results show that the impact of vertical advection on nutrient distribution is 30 % of the contribution of horizontal advection. Despite being weaker by a factor of up to 10−4 than the horizontal currents, vertical velocity is demonstrated to make an important contribution to nutrient distributions in the region of study.
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Steinfeldt, R., J. Sültenfuß, M. Dengler, T. Fischer und M. Rhein. „Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium“. Biogeosciences 12, Nr. 24 (21.12.2015): 7519–33. http://dx.doi.org/10.5194/bg-12-7519-2015.
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Abstract. Upwelling is an important process, bringing gases and nutrients into the ocean mixed layer. The upwelling velocities, however, are too small to be measured directly. Here we use the surface disequilibrium of the 3He / 4He ratio measured in two coastal upwelling regions off Peru in the Pacific ocean and off Mauritania in the Atlantic ocean to calculate the regional distribution of vertical velocities. To also account for the fluxes by diapycnal mixing, microstructure-based observations of the vertical diffusivity have been performed on all four cruises analysed in this study. The upwelling velocities in the coastal regions vary between 1.1 ± 0.3 × 10−5 and 2.8 ± 1.5 × 10−5 m s−1 for all cruises. Vertical velocities are also inferred from the divergence of the wind-driven Ekman transport. In the coastal regimes, both methods agree within the error range. Further offshore, the helium-derived vertical velocity still reaches 1 × 10−5 m s−1, whereas the wind-driven upwelling from Ekman suction is smaller by up to 1 order of magnitude. One reason for this difference is ascribed to eddy-induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium-derived vertical velocities and the vertical diffusivities. The advective part of these fluxes makes up at about 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 ± 0.3 g C m2 d−1 off Peru and 1.6–2.1 ± 0.5 g C m2 d−1 off Mauritania.
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ADIWIBOWO, PRIYO HERU. „KARAKTERISITIK FLOW PATERN PADA ALIRAN DUA FASE GAS-CAIRAN MELEWATI PIPA VERTIKAL“. Jurnal Teknik Industri 11, Nr. 2 (09.02.2012): 117. http://dx.doi.org/10.22219/jtiumm.vol11.no2.117-122.
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Multi-phase flows are widely encountered in several engineering and industrial facilities, such as conventional steam power plants, evaporators and condensers, pressurized-water nuclear reactors, a wide variety of petroleum industries, chemicals and food processing industries. Surely, in the complex pipeline installation of these systems, vertical pipe will be commonly used for pipe connection. The purpose of this work is to investigate the flow pattern of gas-liquid two phase in the vertical pipe. Experiments will be performed in a 36 mm ID acrylic pipe vertical. Superifical liquid velocities and volumetric gas quality will be varied 0.3~1,1 m/s and 0.05~0.2 respectively. Digital camera will be used for flow pattern visualization in the vertical pipe. It was observed that effect of vertical pipe on flow pattern formed cluster bubbly flow for low volumetric gas quality with high superifical liquid velocities. For superifical liquid velocities with medium volumetric gas quality formed homogeneous bubbly flow and high volumetric gas quality is dense bubbly flow.
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Bailey, Nathan R., und Mark W. Scerbo. „The Horizontal-Vertical Velocity Illusion: Implications for the Design of Dynamic Displays“. Proceedings of the Human Factors and Ergonomics Society Annual Meeting 46, Nr. 17 (September 2002): 1556–59. http://dx.doi.org/10.1177/154193120204601706.
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It has long been known that physically equivalent vertical and horizontal stimuli are often perceived as different. The present study examines this phenomenon in the context of motion perception. Participants were asked to judge the speed of stimuli moving in vertical and horizontal directions using the method of constant stimuli. The findings are consistent with previous research in that vertically moving stimuli appear to move relatively faster than horizontal stimuli traveling at the same speed. Further, the axis of focus, i.e., horizontal or vertical, used as the standard for comparison of the two relative velocities, appears to mediate the perceived velocity of the vertically ascending and vertically descending stimuli. These findings may have important implications for the design and implementation of displays that use a combination of both horizontal and vertical indicators.
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Spada, E., T. Tucciarelli, M. Sinagra, V. Sammartano und G. Corato. „Computation of vertically averaged velocities in irregular sections of straight channels“. Hydrology and Earth System Sciences 19, Nr. 9 (14.09.2015): 3857–73. http://dx.doi.org/10.5194/hess-19-3857-2015.
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Abstract. Two new methods for vertically averaged velocity computation are presented, validated and compared with other available formulas. The first method derives from the well-known Huthoff algorithm, which is first shown to be dependent on the way the river cross section is discretized into several subsections. The second method assumes the vertically averaged longitudinal velocity to be a function only of the friction factor and of the so-called "local hydraulic radius", computed as the ratio between the integral of the elementary areas around a given vertical and the integral of the elementary solid boundaries around the same vertical. Both integrals are weighted with a linear shape function equal to zero at a distance from the integration variable which is proportional to the water depth according to an empirical coefficient β. Both formulas are validated against (1) laboratory experimental data, (2) discharge hydrographs measured in a real site, where the friction factor is estimated from an unsteady-state analysis of water levels recorded in two different river cross sections, and (3) the 3-D solution obtained using the commercial ANSYS CFX code, computing the steady-state uniform flow in a cross section of the Alzette River.
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Kumar, Vickal V., Christian Jakob, Alain Protat, Christopher R. Williams und Peter T. May. „Mass-Flux Characteristics of Tropical Cumulus Clouds from Wind Profiler Observations at Darwin, Australia“. Journal of the Atmospheric Sciences 72, Nr. 5 (01.05.2015): 1837–55. http://dx.doi.org/10.1175/jas-d-14-0259.1.
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Abstract Cumulus parameterizations in weather and climate models frequently apply mass-flux schemes in their description of tropical convection. Mass flux constitutes the product of the fractional area covered by convection in a model grid box and the vertical velocity in cumulus clouds. However, vertical velocities are difficult to observe on GCM scales, making the evaluation of mass-flux schemes difficult. Here, the authors combine high-temporal-resolution observations of in-cloud vertical velocities derived from a pair of wind profilers over two wet seasons at Darwin with physical properties of precipitating clouds [cloud-top heights (CTH), convective–stratiform classification] derived from the Darwin C-band polarimetric radar to provide estimates of cumulus mass flux and its constituents. The length of this dataset allows for investigations of the contributions from different cumulus cloud types—namely, congestus, deep, and overshooting convection—to the overall mass flux and of the influence of large-scale conditions on mass flux. The authors found that mass flux was dominated by updrafts and, in particular, the updraft area fraction, with updraft vertical velocity playing a secondary role. The updraft vertical velocities peaked above 10 km where both the updraft area fractions and air densities were small, resulting in a marginal effect on mass-flux values. Downdraft area fractions are much smaller and velocities are much weaker than those in updrafts. The area fraction responded strongly to changes in midlevel large-scale vertical motion and convective inhibition (CIN). In contrast, changes in the lower-tropospheric relative humidity and convective available potential energy (CAPE) strongly modulate in-cloud vertical velocities but have moderate impacts on area fractions. Although average mass flux is found to increase with increasing CTH, it is the environmental conditions that seem to dictate the magnitude of mass flux produced by convection through a combination of effects on area fraction and velocity.
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van der Veen, C. J., und I. M. Whillans. „Force Budget: Numerical Methods and Application to Two-Dimensional Flow Along the Byrd Station Strain Network, West Antarctica (Abstract)“. Annals of Glaciology 11 (1988): 210. http://dx.doi.org/10.3189/s0260305500006716.
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Using the partitioning of full stresses into resistive and lithostatic parts, force balance for plane flow is expressed in terms of strain-rates and a vertical coordinate scaled to the ice thickness. The balance equation and constitutive relation can then be used to calculate stresses through a vertical section of a glacier. Because the flow law is highly non-linear, these calculations are done numerically. Starting at the surface, the force-balance equation is solved by using measured surface velocities to calculate vertical shearing, and this yields velocities at a depth just below the surface. These velocities are used to compute vertical shearing at that depth, from which velocities at the next deeper layer follow. In this way, going progressively downward, velocities and stresses are calculated throughout a section of a glacier.The theory for calculating resistive stresses and velocities in a glacier is applied to the Byrd Station Strain Network. Large longitudinal variations in basal drag and in sliding velocity occur and this result is little affected by errors in the input data or by uncertainties in the constitutive relation for ice. The basal drag is usually equal to the driving stress to within 10–20%, and both vary by a factor of about 2 along the strain network. Sites of high drag and little sliding are not always correlated with basal highs, indicating that some process (for example, complex bed drainage) is controlling the friction at the bed of the West Antarctic ice sheet.
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van der Veen, C. J., und I. M. Whillans. „Force Budget: Numerical Methods and Application to Two-Dimensional Flow Along the Byrd Station Strain Network, West Antarctica (Abstract)“. Annals of Glaciology 11 (1988): 210. http://dx.doi.org/10.1017/s0260305500006716.
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Using the partitioning of full stresses into resistive and lithostatic parts, force balance for plane flow is expressed in terms of strain-rates and a vertical coordinate scaled to the ice thickness. The balance equation and constitutive relation can then be used to calculate stresses through a vertical section of a glacier. Because the flow law is highly non-linear, these calculations are done numerically. Starting at the surface, the force-balance equation is solved by using measured surface velocities to calculate vertical shearing, and this yields velocities at a depth just below the surface. These velocities are used to compute vertical shearing at that depth, from which velocities at the next deeper layer follow. In this way, going progressively downward, velocities and stresses are calculated throughout a section of a glacier. The theory for calculating resistive stresses and velocities in a glacier is applied to the Byrd Station Strain Network. Large longitudinal variations in basal drag and in sliding velocity occur and this result is little affected by errors in the input data or by uncertainties in the constitutive relation for ice. The basal drag is usually equal to the driving stress to within 10–20%, and both vary by a factor of about 2 along the strain network. Sites of high drag and little sliding are not always correlated with basal highs, indicating that some process (for example, complex bed drainage) is controlling the friction at the bed of the West Antarctic ice sheet.
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Lefeuvre, Frédéric, Roger Turpening, Carol Caravana, Andrea Born und Laurence Nicoletis. „Vertical open fractures and shear‐wave velocities derived from VSPs, full waveform acoustic logs, and televiewer data“. GEOPHYSICS 58, Nr. 6 (Juni 1993): 818–34. http://dx.doi.org/10.1190/1.1443467.
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Fracture or stress‐related shear‐wave birefringence (or azimuthal anisotropy) from vertical seismic profiles (VSPs) is commonly observed today, but no attempt is made to fit the observations with observed in‐situ fractures and velocities. With data from a hard rock (limestones, dolomites, and anhydrites) region of Michigan, fast and slow shear‐wave velocities have been derived from a nine‐component zero offset VSP and compared to shear‐wave velocities from two full waveform acoustic logs. To represent the shear‐wave birefringence that affects the shear wave’s vertical propagation, a propagator matrix technique is used allowing a local measurement independent of the overburden layers. The picked times obtained by using a correlation technique have been corrected in the birefringent regions before we compute the fast and slow velocities. Although there are some differences between the three velocity sets, there is a good fit between the velocities from the shear‐wave VSP and those from the two logs. We suspect the formations showing birefringence to be vertically fractured. To support this, we examine the behavior of the Stoneley wave on the full waveform acoustic logs in the formations. In addition, we analyze the borehole televiewer data from a nearby well. There is a good fit between the fractures seen from the VSP data and those seen from the borehole.
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Zheng, Bofu, Andrew J. Lucas, Robert Pinkel und Arnaud Le Boyer. „Fine-Scale Velocity Measurement on the Wirewalker Wave-Powered Profiler“. Journal of Atmospheric and Oceanic Technology 39, Nr. 2 (Februar 2022): 133–47. http://dx.doi.org/10.1175/jtech-d-21-0048.1.
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Abstract The Wirewalker (WW) ocean-wave-powered vertical profiling system allows the collection of high-resolution oceanographic data due to its rapid profiling, hydrodynamically quiet operation, and long endurance. We have assessed the potential for measuring fine-scale ocean velocities from the Wirewalker platform using commercially available acoustic velocimeters. Although the vertical profiling speed is relatively steady, platform motion affects the velocity measurements and requires correction. We present an algorithm to correct our velocity estimates using platform motion calculated from the inertial sensors—accelerometer, gyroscope, and magnetometer—on a Nortek Signature1000 acoustic Doppler current profiler (ADCP). This correction, carried out ping by ping, was effective in removing the vehicle motion from the measured velocities. The motion-corrected velocities contain contributions from surface wave orbital velocities, especially near the surface, and the background currents. To proceed, we use an averaging approach that leverages both the vertical platform profiling of the system and the ∼15–20 m vertical profiling range resolution of the down-looking ADCP to separate the surface wave orbital velocities and the background flow. The former can provide information on the wave conditions. From the latter, we are able to estimate fine-scale velocity and shear with spectral wavenumber rolloff at vertical scales around 3 m, a vertical resolution several times finer than that possible from modern shipboard or fixed ADCPs with similar profiling range, and similar to recent glider measurements. When combined with a continuous time series of buoy drift calculated from the onboard GPS, a highly resolved total velocity field is obtained, with a unique combination of space and time resolution.
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Barceló-Llull, Bàrbara, Evan Mason, Arthur Capet und Ananda Pascual. „Impact of vertical and horizontal advection on nutrient distribution in the southeast Pacific“. Ocean Science 12, Nr. 4 (25.08.2016): 1003–11. http://dx.doi.org/10.5194/os-12-1003-2016.
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Abstract. An innovative approach is used to analyze the impact of vertical velocities associated with quasi-geostrophic (QG) dynamics on the redistribution and uptake of nitrate in the southeast Pacific (SEP). A total of 12 years of vertical and horizontal currents are derived from an observation-based estimate of the ocean state. Horizontal velocities are obtained through the application of thermal wind balance to weekly temperature and salinity fields. Vertical velocities are estimated by integration of the QG omega equation. Seasonal variability of the synthetic vertical velocity and kinetic energy associated with the horizontal currents is coincident, with peaks in austral summer (November–December) in accord with published observations. The impact of vertical velocity on SEP nitrate uptake rates is assessed by using two Lagrangian particle tracking experiments that differ according to vertical forcing (ω = ωQG vs. ω = 0). From identical initial distributions of nitrate-tagged particles, the Lagrangian results show that vertical motions induce local increases in nitrate uptake reaching up to 30 %. Such increases occur in low uptake regions with high mesoscale activity. Despite being weaker than horizontal currents by a factor of up to 10−4, vertical velocity associated with mesoscale activity is demonstrated to make an important contribution to nitrate uptake, hence productivity, in low uptake regions.
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Lee, Changho, Q. Hung Truong und Jong-Sub Lee. „Cementation and bond degradation of rubber–sand mixtures“. Canadian Geotechnical Journal 47, Nr. 7 (Juli 2010): 763–74. http://dx.doi.org/10.1139/t09-139.
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Cementation influences the mechanical behavior of soils. The effects of cementation and bond degradation are investigated for lightly cemented rigid sand and soft rubber particle mixtures subjected to vertical loading under the K0 condition. Cemented and uncemented specimens were prepared with various sand volume fractions. The propagation velocity of small strain body waves was measured by piezo materials, incorporated within an oedometer. Cemented specimens exhibited a bilinear behavior in the semi-log plot (vertical strain versus log of vertical stress). Vertical strains of a cemented specimen normalized by an uncemented specimen show that the stress–strain behavior is controlled by several different mechanisms and forces: capillary force, cementation bonds, and interparticle contact stresses after bond degradation. The elastic wave velocities dramatically increase due to cementation hardening under fixed vertical stress, and are constant after curing even though vertical stress increases. Additional loading of the vertical effective stress decreases the elastic wave velocities due to bond degradation. The shear wave velocity presents three behavior regions as a function of the sand fraction for both uncemented and cemented specimens: rubber-like, sand-like, and transition behaviors. The vertical stress–strain response and the elastic wave velocities can serve as indicators of cementation and bond degradation.
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Collis, Scott, Alain Protat, Peter T. May und Christopher Williams. „Statistics of Storm Updraft Velocities from TWP-ICE Including Verification with Profiling Measurements“. Journal of Applied Meteorology and Climatology 52, Nr. 8 (August 2013): 1909–22. http://dx.doi.org/10.1175/jamc-d-12-0230.1.
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AbstractComparisons between direct measurements and modeled values of vertical air motions in precipitating systems are complicated by differences in temporal and spatial scales. On one hand, vertically profiling radars more directly measure the vertical air motion but do not adequately capture full storm dynamics. On the other hand, vertical air motions retrieved from two or more scanning Doppler radars capture the full storm dynamics but require model constraints that may not capture all updraft features because of inadequate sampling, resolution, numerical constraints, and the fact that the storm is evolving as it is scanned by the radars. To investigate the veracity of radar-based retrievals, which can be used to verify numerically modeled vertical air motions, this article presents several case studies from storm events around Darwin, Northern Territory, Australia, in which measurements from a dual-frequency radar profiler system and volumetric radar-based wind retrievals are compared. While a direct comparison was not possible because of instrumentation location, an indirect comparison shows promising results, with volume retrievals comparing well to those obtained from the profiling system. This prompted a statistical analysis of an extended period of an active monsoon period during the Tropical Warm Pool International Cloud Experiment (TWP-ICE). Results show less vigorous deep convective cores with maximum updraft velocities occurring at lower heights than some cloud-resolving modeling studies suggest.
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Bogusz, Janusz, Anna Klos und Krzysztof Pokonieczny. „Optimal Strategy of a GPS Position Time Series Analysis for Post-Glacial Rebound Investigation in Europe“. Remote Sensing 11, Nr. 10 (22.05.2019): 1209. http://dx.doi.org/10.3390/rs11101209.
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We describe a comprehensive analysis of the 469 European Global Positioning System (GPS) vertical position time series. The assumptions we present should be employed to perform the post-glacial rebound (PGR)-oriented comparison. We prove that the proper treatment of either deterministic or stochastic components of the time series is indispensable to obtain reliable vertical velocities along with their uncertainties. The statistical significance of the vertical velocities is examined; due to their small vertical rates, 172 velocities from central and western Europe are found to fall below their uncertainties and excluded from analyses. The GPS vertical velocities reach the maximum values for Scandinavia with the maximal uplift equal to 11.0 mm/yr. Moreover, a comparison between the GPS-derived rates and the present-day motion predicted by the newest Glacial Isostatic Adjustment (GIA) ICE-6G_C (VM5a) model is provided. We prove that these rates agree at a 0.5 mm/yr level on average; the Sweden area with the most significant uplift observed agrees within 0.2 mm/yr. The largest discrepancies between GIA-predicted uplift and the GPS vertical rates are found for Svalbard; the difference is equal to 6.7 mm/yr and arises mainly from the present-day ice melting. The GPS-derived vertical rates estimated for the southern coast of the Baltic Sea are systematically underestimated by the GIA prediction by up to 2 mm/yr. The northern British Isles vertical rates are overestimated by the GIA model by about 0.5 mm/yr. The area of the Netherlands and the coastal area of Belgium are both subsiding faster than it is predicted by the GIA model of around 1 mm/yr. The inland part of Belgium, Luxemburg and the western part of Germany show strong positive velocities when compared to the GIA model. Most of these stations uplift of more than 1 mm/yr. It may be caused by present-day elastic deformation due to terrestrial hydrology, especially for Rhein basin, or non-tidal atmospheric loading, for Belgium and Luxembourg.
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Michaelides, Silas, John Lane und Takis Kasparis. „Effect of Vertical Air Motion on Disdrometer Derived Z-R Coefficients“. Atmosphere 10, Nr. 2 (14.02.2019): 77. http://dx.doi.org/10.3390/atmos10020077.
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For synoptic-scale motions the vertical velocity component is typically of the order of a few centimeters per second. In general, the vertical velocity is not measured directly but must be inferred from other meteorological fields that are measured directly. In the present study, a Joss–Waldvogel disdrometer was used in order to establish the drop size distributions (DSD) at Athalassa, Cyprus. Data from a radiosonde station co-located with the disdrometer were also collected which were subsequently used to derive estimates of vertical velocities. Meteorological fields, including vertical velocities, were extracted from an atmospheric reanalysis, for an area centered over the disdrometer and radiosonde station instrumentation. The disdrometer data were used to determine the Z-R disdrometer derived coefficients, A and b, where Z = A Rb. To model the vertical air effect on the Z-R disdrometer derived coefficients an idealistic notion of flux conservation of the DSD is adopted. This adjusted DSD (FCM-DSD) is based on the exponential DSD and is modified by the relationship between drop terminal velocity (D) and vertical air speed w . The FCM-DSD has a similar appearance to the popular gamma DSD for w < 0. A clear segregation is seen in the A-w plane for both data and model. The data points are also clearly segregated in the b- w plane, but the model points are on opposite sides of the w = 0 line. It is also demonstrated that vertical velocities can be extracted from radiosonde data if initial balloon volume is accurately measured, along with an accurate measurement of the mass of the complete radiosonde-balloon system. To accomplish this, vertical velocities from radiosonde data were compared to reanalysis vertical velocity fields. The resulting values of initial balloon volume are found to be within the range of measured values.
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Zahmatkesh, Homayoon, und Abbas Abedeni. „Non-Parametric Wavelet Functional Analysis for Horizontal and Vertical displacements Derived from GPS Stations in Western Alaska during the Year 2012“. Earth Science Research 6, Nr. 2 (10.07.2017): 112. http://dx.doi.org/10.5539/esr.v6n2p112.
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In order to analyze the dynamic processes of the Earth interior and the effect of the propagation of the seismic waves to the surface, a comprehensive study of the Earth crust kinematics is necessary. Although the Global Positing System (GPS) is a powerful method to measure ground displacements and velocities both horizontally and vertically as well as to infer the tectonic stress regime generated by the subsurface processes (from local fault systems to huge tectonic plate movements and active volcanoes), the complexity of the deformation pattern generated during such movements is not always easy to be interpreted. Therefore, it is necessary to work on new methodologies and modifying the previous approaches in order to improve the current methods and better understand the crustal movements. In this paper, we focus on western Alaska area, where many complex faults and active volcanoes exist. In particular, we analyze the data acquired each 30 seconds by three GPS stations located in western Alaska (AC31, AB09 and AB11) from January 1, 2012 to December 31, 2012 in order to compute their displacements in horizontal and vertical components by vectorial summation of the average daily and annual velocities components. Furthermore, we design non-parametric DMeyer and Haar wavelets for horizontal and vertical velocities directions in order to identify significant and homogenous displacements during the year 2012. Finally, the non-parametric decomposition of total horizontal and vertical normalized velocities based on level 1 and level 2 coefficients have been applied to compute normal and cumulative probability histograms related to the accuracy and statistical evolution of each applied wavelet. The results present a very good agreement between the designed non-parametric wavelets and their decomposition functions for each of the three above mentioned GPS stations displacements and velocities during the year 2012.
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Koldunov, A. V., und T. V. Belonenko. „Hydrodynamic Modeling of Vertical Velocities in the Lofoten Vortex“. Izvestiya, Atmospheric and Oceanic Physics 56, Nr. 5 (September 2020): 502–11. http://dx.doi.org/10.1134/s0001433820040040.
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López-Corredoira, M., H. Abedi, F. Garzón und F. Figueras. „Vertical velocities from proper motions of red clump giants“. Astronomy & Astrophysics 572 (Dezember 2014): A101. http://dx.doi.org/10.1051/0004-6361/201424573.
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Osgood, Kenric E., John M. Bane und William K. Dewar. „Vertical velocities and dynamical balances in Gulf Stream meanders“. Journal of Geophysical Research 92, Nr. C12 (1987): 13029. http://dx.doi.org/10.1029/jc092ic12p13029.
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Martner, Brooks E. „Vertical Velocities in a Thunderstorm Gust Front and Outflow“. Journal of Applied Meteorology 36, Nr. 5 (Mai 1997): 615–22. http://dx.doi.org/10.1175/1520-0450(1997)036<0615:vviatg>2.0.co;2.
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MARKOVICH, K., V. YALTYKHOV, A. DEGTJAREV und M. MAKARAVA. „USE OF COMPLEX TECHNIQUE OF GEOLOGICAL INTERPRETATION OF GEOPHYSICAL FIELDS FOR PREDICTION OF POSSIBLE VALUES OF VELOCLES OF MODERN VERTICAL MOVEMENTS OF THE EARTH'S CRUST“. Herald of Polotsk State University. Series F. Civil engineering. Applied sciences 32, Nr. 14 (29.12.2022): 107–13. http://dx.doi.org/10.52928/2070-1683-2022-32-14-107-113.
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The article considers the possibility of predicting the velocities of modern vertical movements of the earth's crust using a complex method of geological interpretation of the geophysical fields of Arkhangelsk – Fedynsk – Fotiadi. The search for links between the velocities of modern vertical movements of the earth's crust with anomalous gravitational and magnetic fields, the topography of the day surface, and the thickness of the earth's crust for one geological structure of the territory of the Republic of Belarus in the form of the Orsha depression was performed. To search for links, the integral relation of Karataev – Vatlin – Zakharova was used. Based on the results of forecasting, a model map of the velocities of modern vertical movements of the Earth's crust was constructed. The map has sufficient accuracy and reliability for practical use.
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Azzopardi, B. J., und J. C. F. Teixeira. „Detailed Measurements of Vertical Annular Two-Phase Flow—Part I: Drop Velocities and Sizes“. Journal of Fluids Engineering 116, Nr. 4 (01.12.1994): 792–95. http://dx.doi.org/10.1115/1.2911851.
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Phase anemometry and laser diffraction techniques have been employed to measure drop sizes in annular two-phase flow. The former technique also provides drop velocities. When converted to the same basis, the drop size distributions from the two techniques are in agreement. Drop velocities were 20 percent below the corresponding local velocities for the gas. Standard deviations of the drop velocities were 10 to 65 percent higher than those for the gas.
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Kumar, Naresh, M. Mohapatra und B. P. Yadav. „Boundary Layer Impact on Mountain Waves across Western Ghats of India“. Mapana - Journal of Sciences 10, Nr. 1 (30.06.2011): 25–31. http://dx.doi.org/10.12723/mjs.18.3.
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A two- layer model has been developed assuming a steady, non- rotating and frictionless flow of vertically unbounded Boussinesq fluid across 2-D profile of Western Ghats of India. Further, it is assumed that lower layer is inviscid with neutral stability (N=0) and upper layer has constant static stability with respect to height, given by N= Constant (where N is Brunt- Väisälä frequency). The analytical expressions for vertical velocities and mountain drag have been derived across Western Ghats of India. It is found that vertical velocities are dependent on the characteristics like size and height of ridge as well as plateau region to the eastern side of the Western Ghats. However, the mountain drag is not dependent on the above characteristics of the plateau region to the east of Western Ghats confirming the earlier findings.
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Hawley, Robert L., Edwin D. Waddington, David L. Morse, Nelia W. Dunbar und Gregory A. Zielinski. „Dating firn cores by vertical strain measurements“. Journal of Glaciology 48, Nr. 162 (2002): 401–6. http://dx.doi.org/10.3189/172756502781831250.
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AbstractWe have developed a system for measuring a vertical strain-rate profile in the firn on polar ice sheets using a readily available video camera to detect metal bands inserted in an air-filled hole. We used this system in 1995 and 1996 at Taylor Dome, Antarctica. We use density measurements combined with our strain rates to infer vertical velocities. From our velocities we calculate a steady-state depth–age scale for the firn at Taylor Dome. The age of a visible ash layer from 79.1 m is 675 ± 25 years; this ash can be correlated with ash found at 97.2 m in a recent ice core at Siple Dome, West Antarctica.
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Dellwik, E., J. Mann, F. Bingöl und K. S. Larsen. „Mean vertical velocities and flow tilt angles at a fetch-limited forest site in the context of carbon dioxide vertical advection“. Biogeosciences Discussions 6, Nr. 4 (12.08.2009): 8167–213. http://dx.doi.org/10.5194/bgd-6-8167-2009.
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Abstract. An analysis of flow angles from a fetch-limited beech forest site with clearings is presented. Flow angles and vertical velocities from two types of sonic anemometers as well as a ground based remote sensing lidar were analysed. Instead of using rotations, where zero-flow angles were assumed for neutral flow, the data from the instruments were interpreted in relation to the terrain. Uncertainties regarding flow distortion and limited sampling time (statistical uncertainty) were evaluated and found to be significant. Especially for one of the sonic anemometers, relatively small changes in the flow distortion correction could change the sign of mean vertical velocities taken during stable atmospheric stratification relative to the neutral flow. Despite the uncertainties, it was possible to some extent to relate both positive and negative mean flow angles to features in the terrain. Conical and linear scans with a remote sensing lidar were evaluated for estimation of vertical velocities and flow angles. The results of the vertical conical scans were promising, and yielded negative flow angles for a sector where the forest is fetch-limited. However, more data and analysis is needed for a complete evaluation of the technique. The horizontal linear scans showed the variability of the mean wind speed field. A vertical velocity was calculated from different focusing distances, but this estimate yielded unrealistically high vertical velocities, due to neglect of the transversal wind component. The vertical advection term was calculated using the measured mean flow angles at the mast and profile measurements of carbon dioxide, but it is not recommended to use in relation with the flux measurement as the vertical velocity measured at the mast is most likely not representative for the whole forest.
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Steinfeldt, R., J. Sültenfuß, M. Dengler, T. Fischer und M. Rhein. „Coastal upwelling off Peru and Mauritania inferred from helium isotope disequilibrium“. Biogeosciences Discussions 12, Nr. 13 (14.07.2015): 11019–59. http://dx.doi.org/10.5194/bgd-12-11019-2015.
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Abstract. Oceanic upwelling velocities are too small to be measured directly. The surface disequilibrium of the 3He/4He ratio provides an indirect method to infer vertical velocities at the base of the mixed layer. Samples of helium isotopes were taken from two coastal upwelling regions, off Peru on cruise M91, and off Mauritania on 3 cruises. The helium-3 flux into the mixed layer also depends on the diapycnal mixing. Direct observations of the vertical diffusivity have been performed on all 4 cruises and are also used in this study. The resulting upwelling velocities in the coastal regions vary between 1.1 × 10−5 and 2.8 × 10−5 m s−1 for all cruises. Vertical velocities off the equator can also be inferred from the divergence of the wind driven Ekman transport. In the coastal regimes, the agreement between wind and helium derived upwelling is fairly good at least for the mean values. Further offshore, the helium derived upwelling still reaches 1 × 10−5 m s−1, whereas the wind driven upwelling from Ekman suction is smaller by at least one order of magnitude. One reason for this difference might be eddy induced upwelling. Both advective and diffusive nutrient fluxes into the mixed layer are calculated based on the helium derived vertical velocities and the measured vertical diffusivities. The advective part of these fluxes makes up at least 50 % of the total. The nutrient flux into the mixed layer in the coastal upwelling regimes is equivalent to a net community production (NCP) of 1.3 g C m2 d−1 off Peru and 1.6–1.9 g C m2 d−1 off Mauritania.
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Chen, Ke, Peter Gaube und Enric Pallàs-Sanz. „On the Vertical Velocity and Nutrient Delivery in Warm Core Rings“. Journal of Physical Oceanography 50, Nr. 6 (Juni 2020): 1557–82. http://dx.doi.org/10.1175/jpo-d-19-0239.1.
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AbstractWe examine various contributions to the vertical velocity field within large mesoscale eddies by analyzing multiple solutions to an idealized numerical model of a representative anticyclonic warm core Gulf Stream ring. Initial conditions are constructed to reproduce the observed density and nutrient profiles collected during the Warm Core Rings Program. The contributions to vertical fluxes diagnosed from the numerical simulations are compared against a divergence-based, semidiagnostic equation and a generalized omega equation to better understand the dynamics of the vertical velocity field. Frictional decay alone is found to be ineffective in raising isopycnals and transporting nutrients to the upper ocean. With representative wind forcing, the magnitude of vorticity gradient–induced Ekman pumping is not necessarily larger than the current-induced counterpart on a time scale relevant to ecosystem response. Under realistic forcing conditions, strain deformation can perturb the ring to be noncircular and induce vertical velocities much larger than the Ekman vertical velocities. Nutrient budget diagnosis, together with analysis of the relative magnitudes of the various types of vertical fluxes, allows us to describe the time-scale dependence of nutrient delivery. At time scales that are relevant to individual phytoplankton (from hours to days), the magnitudes of nutrient flux by Ekman velocities and deformation-induced velocities are comparable. Over the life span of a typical warm core ring, which can span multiple seasons, surface current–induced Ekman pumping is the most effective mechanism in upper-ocean nutrient enrichment because of its persistence in the center of anticyclones regardless of the direction of the wind forcing.
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King, Matt A., und Christopher S. Watson. „Geodetic vertical velocities affected by recent rapid changes in polar motion“. Geophysical Journal International 199, Nr. 2 (18.09.2014): 1161–65. http://dx.doi.org/10.1093/gji/ggu325.
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Abstract Secular motion of Earth's rotation pole results in large-scale secular deformation of Earth. Here, we investigate the magnitude of the deformation that has resulted from the rapid motion of the rotation pole to the east since ∼2005. We show that geodetic (GNSS, DORIS, VLBI and SLR) estimates of vertical velocity since ∼2005 have been biased by up to ±0.38 mm yr–1 relative to the longer-term deformation pattern. The largest signals occur within regions that include the U.S. Pacific Coast, Europe and South Pacific islands where geodetic measurements provide essential measurements of tide-gauge vertical movement and important constraints on models of glacial isostatic adjustment. Consequently, geodetic vertical velocities based on recent data should not be interpreted as being identical to centennial or longer term vertical land movement. Since 2010 the effect is further amplified by the overprediction of the IERS polar motion model relative to the ongoing secular change in pole position—during this time geodetic vertical velocities based on the IERS pole tide model are not just biased relative to the long-term rates but also from actual post-2010 Earth deformation. For geophysical or reference frame studies seeking geodetic vertical velocities that are representative of decadal timescales, where interannual variation is considered noise, the correction for this non-linear effect is straightforward, requiring an elastic computation using a reference rate of polar motion that is linear over the timescales of interest.
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Zhao, Chuan Zhen, Li Yuan Yu, Chun Xiao Tang, Ming Li und Jian Xin Zhang. „Optimized Simulation for GaN Growth in Vertical HVPE Reactor“. Advanced Materials Research 301-303 (Juli 2011): 116–20. http://dx.doi.org/10.4028/www.scientific.net/amr.301-303.116.
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The paper reports the setting up of a model of fluid dynamic for GaN HVPE system and the simulation. The deposition of GaN with the variation of the gas flow inlet velocities is investigated. The influence of diffusion coefficient on the deposition of GaN is also discussed. It is found that the influence of the gas flow inlet velocities on the deposition is large and the influence of diffusion coefficient on the deposition of GaN is small in vertical HVPE.
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Lott, Lori A., und Robert B. Post. „Up–down Asymmetry in Vertical Induced Motion“. Perception 22, Nr. 5 (Mai 1993): 527–35. http://dx.doi.org/10.1068/p220527.
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Induced motion (IM) is the illusory movement of an object in the direction opposite to the real motion of adjacent detail. One theory of IM suggests that it results, in part, from suppression of optokinetic nystagmus (OKN) by fixational (smooth-pursuit) effort. In several studies an asymmetry in human vertical OKN has been reported, with upward optokinetic stimulation eliciting higher OKN gain than downward motion. This provides a test of the nystagmus-suppression theory of IM. If suppression of OKN contributes significantly to IM, upward inducing stimuli should result in a greater magnitude of the illusion than should downward stimulus motion. Additionally, the asymmetry of vertical OKN should become more pronounced at higher stimulus velocities. Therefore, the asymmetry of vertical IM should be greater at higher inducing-stimulus velocities. Twelve subjects viewed a large, random-dot stimulus, which moved either upward or downward at a velocity of 10, 40, or 70 deg s−1. Subjects fixated a horizontally moving laser spot and adjusted a rod to match the apparent slope of the motion path of the spot. IM magnitude was derived from these measures. Mean IM velocity was significantly higher with upward than with downward stimulation, and the difference was maximal at velocities of 40 and 70 deg s−1. The results are discussed within the context of the nystagmus-suppression theory and other theories of IM.
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Calmer, Radiance, Gregory C. Roberts, Jana Preissler, Kevin J. Sanchez, Solène Derrien und Colin O'Dowd. „Vertical wind velocity measurements using a five-hole probe with remotely piloted aircraft to study aerosol–cloud interactions“. Atmospheric Measurement Techniques 11, Nr. 5 (03.05.2018): 2583–99. http://dx.doi.org/10.5194/amt-11-2583-2018.
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Abstract. The importance of vertical wind velocities (in particular positive vertical wind velocities or updrafts) in atmospheric science has motivated the need to deploy multi-hole probes developed for manned aircraft in small remotely piloted aircraft (RPA). In atmospheric research, lightweight RPAs (< 2.5 kg) are now able to accurately measure atmospheric wind vectors, even in a cloud, which provides essential observing tools for understanding aerosol–cloud interactions. The European project BACCHUS (impact of Biogenic versus Anthropogenic emissions on Clouds and Climate: towards a Holistic UnderStanding) focuses on these specific interactions. In particular, vertical wind velocity at cloud base is a key parameter for studying aerosol–cloud interactions. To measure the three components of wind, a RPA is equipped with a five-hole probe, pressure sensors, and an inertial navigation system (INS). The five-hole probe is calibrated on a multi-axis platform, and the probe–INS system is validated in a wind tunnel. Once mounted on a RPA, power spectral density (PSD) functions and turbulent kinetic energy (TKE) derived from the five-hole probe are compared with sonic anemometers on a meteorological mast. During a BACCHUS field campaign at Mace Head Atmospheric Research Station (Ireland), a fleet of RPAs was deployed to profile the atmosphere and complement ground-based and satellite observations of physical and chemical properties of aerosols, clouds, and meteorological state parameters. The five-hole probe was flown on straight-and-level legs to measure vertical wind velocities within clouds. The vertical velocity measurements from the RPA are validated with vertical velocities derived from a ground-based cloud radar by showing that both measurements yield model-simulated cloud droplet number concentrations within 10 %. The updraft velocity distributions illustrate distinct relationships between vertical cloud fields in different meteorological conditions.