Maximum Upward Velocity Research Articles

Association of lightning occurrence with precipitation cloud column structure at a fixed position

In this study, a C-band frequency-modulated continuous-wave (C-FMCW) radar, with its feature of vertical detection, was combined with lightning discharge recordings within a 3 km range to investigate the dependence of lightning occurrence on the structure of precipitation cloud columns (PCCs) from the perspective of a fixed position. The results show that, relative to PCCs without lightning, PCCs with lightning exhibit greater maximum reflectivity, maximum upward radial velocity, maximum velocity spectrum width, cloud top height, and vertically integrated liquid in terms of their average values, and wider-range distributions of these parameters. Using the Light Gradient Boosting Machine algorithm, a lightning diagnosis program that integrates multiple C-FMCW radar parameters was developed. Its hit rate of lightning occurrence is 93.5% and it has a threat score of 0.421. The maximum velocity spectrum width above the melting layer was found to be the most effective in distinguishing PCCs with or without lightning. It was suggested that the hydrometeor properties at a specific location, specifically the size diversity and content of ice-phase particles, should be the key elements determining the occurrence of lightning in PCCs.

Mixed‐Phase Clouds and Precipitation in Southern Ocean Cyclones and Cloud Systems Observed Poleward of 64°S by Ship‐Based Cloud Radar and Lidar

AbstractMixed‐phase clouds (MPCs), composed of both liquid and ice, are prevalent in Southern Ocean cyclones. A characterization of these clouds on fine vertical scales is required in order to understand the microphysical processes within these clouds, and for model and satellite evaluations over this region. We investigated three examples of cloud systems collected by ship‐mounted remote‐sensing instruments adjacent to East Antarctica at latitudes between 64°S and 69°S. These cases allow us to examine the properties of midlevel MPCs, with cloud tops between 2 and 6 km. Midlevel MPCs contain multiple layers of supercooled liquid water (SLW) embedded within ice during the passage of cyclones. SLW layers are capped by strong temperature inversions and are observed at temperatures as low as −31°C. Convective generating cells (GCs) are present inside supercooled liquid‐topped midlevel MPCs. The horizontal extent, vertical extent, and maximum upward Doppler velocity of these GCs were 0.6–3.6 km, 0.7–1.0 km, and 0.5–1.0 m s−1, respectively, and are consistent with observations from previous lower‐latitude studies. Ice precipitation is nearly ubiquitous, except in the thinnest clouds at the trailing end of the observed systems. Seeding of lower SLW layers from above leads to periods with either larger ice particles or greater ice precipitation rates. Periods of supercooled drizzle lasting up to 2 h were observed toward the end of two of the three cyclone systems. This supercooled drizzle turns into predominantly ice precipitation as the result of seeding by ice clouds located above the precipitating SLW layer.

Spectral Study of the Active Region with the Ellerman Bomb and Hα Surges. Chromosphere. Ellerman Bomb

The results from the analysis of spectral observations in the Hα line of the active region (AR) NOAA 11024, in which the Ellerman bomb (EB) and various chromospheric surges developed, are presented. Spectral data with high spatial and temporal resolution were obtained using the THEMIS French–Italian solar telescope (Tenerife, Spain) on July 4, 2009. The observation time was 20 min. On the day of the observations, the AR was at the stage of a sharp increase in activity. The Hα line profiles obtained for different periods of the Ellerman bomb development were very diverse, mainly consisted of several components, and were asymmetrical with excess emission in the short-wavelength wing. The maximum increase in the intensity of the emission component, compared with the profile for the AR segment without active formations, in the short-wavelength wing by 73% and in the long-wavelength wing by 35% occurred at a distance of ±0.16 nm from the core of the Hα line. The temporal variations of intensity in the wings of the Hα line indicate that there was a gradual energy release for the first 8 min of the Ellerman bomb development and then there was a pulse energy release for 6 min. The EB brightness increase period consisted of five peaks with an interval of approximately 1 min. The obtained temporal changes in the line-of-sight velocity (Vlos) of the chromospheric matter over the EB development region at the level of the Hα line core formation indicate that the velocity distribution in this region was mainly due to the development of chromospheric surges. In the segment without active formations, values of Vlos experienced small fluctuations within ±2 km/s. Two periods of increase in Vlos are distinguished. They consisted of several individual peaks: in the first half of the observations, the chromospheric matter mainly moved upward, while it mainly moved downward in the second half of the observations. Above the EB development region, different kinds of Hα-surges were observed. The maximum upward velocity in the return surges reached –12 to –16 km/s and the chromospheric matter descended along the same trajectories of magnetic loops with two times higher velocity, up to 22–30 km/s. In the loop surge, the maximum upward velocity on one side of the loop was –7 km/s and the downward velocity on the other side reached 18 km/s. One of the surges showed signs of plasma vortex motions, as evidenced by the inclined dark streaks in the spectra. Features of intensity variation in the wings of the Hα line and in the line-of-sight velocity of the chromospheric matter indicate that the Ellerman bomb and the accompanying Hα-surges, which appeared and developed in the AR under study, resulted from the magnetic reconnection caused by the emergence of the new serpentine magnetic flux and its interaction with the pre-existing magnetic field or between the magnetic loops of the flux itself.

Experimental Observations on Impact Velocity and Entrapped Air for Standing Wave Impacts on Vertical Hydraulic Structures with Overhangs

This study focusses on increasing the understanding on vertical hydraulic structures with relatively short overhangs subjected to standing wave impacts. To this end, the impact velocity and the entrapped air are studied in detail, given their influence on the impulsive loading characteristics and consequently on the structural dynamic response. This study is based on regular wave laboratory experimental data obtained for relatively short overhangs with respect to the wave length and with respect to the overhang height. The laboratory tests illustrate the complex wave hydrodynamics before the wave impacts, influenced by the incident wave conditions and structural characteristics. Regarding the impact velocity, the experimental measurements with a wall wave gauge in the tests without overhangs show that the maximum upward velocities deviate from linear wave theory between +5.5% and +13.0%, while the zero-crossing upward velocities deviate from linear wave theory between +1.9% and +7.0%. The zero-crossing upward velocities estimated from third order wave theory deviate from the linear wave theory between +1.8% and +4.7%. In the tests with overhangs, the maximum upward velocity below the overhang estimated by camera recording measurements deviates from linear wave theory between −11.8% and +13.4%. It was also found that when considering the experimental impact velocity from camera recordings in the tests with overhangs, the mean effective bounce-back factor β deviates relatively little from when linear wave theory is used (≈1%), while the uncertainty described by the standard deviation increases significantly (≈35%). Regarding the entrapped air, it is shown that the interaction between incident wave parameters and structural configurations leads to a large variation in the entrapped air area, up to a factor of 5.7 for shorter overhangs and a factor of 9.5 for longer overhangs. This variability in entrapped air characteristics leads to significant effects on the loading on the structure, as observed by the variability on pressure measurements. The experimental results showed increasing impact durations and increasing effective bounce-back factor β in the tests with increasing entrapped air dimensions. This study highlights the importance of the details of the impact velocity and entrapped air for load estimations during the design of vertical hydraulic structures exposed to standing wave impacts. This is particularly important for thin structures such as steel gates which are susceptible to a dynamic behaviour under such impulsive loads.

Estimating the Maximum Vertical Velocity at the Leading Edge of a Density Current

AbstractThe maximum upward vertical velocity at the leading edge of a density current is commonly <10 m s−1. Studies of the vertical velocity, however, are relatively few, in part owing to the dearth of high-spatiotemporal-resolution observations. During the Plains Elevated Convection At Night (PECAN) field project, a mobile Doppler lidar measured a maximum vertical velocity of 13 m s−1 at the leading edge of a density current created by a mesoscale convective system during the night of 15 July 2015. Two other vertically pointing instruments recorded 8 m s−1 vertical velocities at the leading edge of the density current on the same night. This study describes the structure of the density current and attempts to estimate the maximum vertical velocity at their leading edges using the following properties: the density current depth, the slope of its head, and its perturbation potential temperature. The method is then be applied to estimate the maximum vertical velocity at the leading edge of density currents using idealized numerical simulations conducted in neutral and stable atmospheres with resting base states and in neutral and stable atmospheres with vertical wind shear. After testing this method on idealized simulations, this method is then used to estimate the vertical velocity at the leading edge of density currents documented in several previous studies. It was found that the maximum vertical velocity can be estimated to within 10%–15% of the observed or simulated maximum vertical velocity and indirectly accounts for parameters including environmental wind shear and static stability.

Particle fountains in a confined environment

We present new experiments and theoretical models of the motion of relatively dense particles carried upwards by a liquid jet into a laterally confined space filled with the same liquid. The incoming jet is negatively buoyant and rises to a finite height, at which the dense mixture of liquid and particles, diluted by the entrainment of ambient liquid, falls back to the floor. The mixture further dilutes during the collapse and then spreads out across the floor and supplies an up-flow outside the fountain equal to the source volume flux plus the total entrained volume flux. The fate of the particles depends on the particle fall speed, $u_{fall}$ , compared to (i) the characteristic fountain velocity in the fountain core, $u_{F}$ , (ii) the maximum upward velocity in the ambient fluid outside the fountain, $u_{u}(0)$ , which occurs at the base of the fountain, and (iii) the upward velocity in the ambient fluid above the top of the fountain associated with the original volume flux in the liquid jet, $u_{BG}$ . From this comparison we identify four regimes. (I) If $u_{fall}>u_{F}$ , then the particles separate from the fountain and settle on the floor. (II) If $u_{F}>u_{fall}>u_{u}(0)$ , the particles are carried to the top of the fountain but then settle as the collapsing flow around the fountain spreads out across the floor; we do not observe particle suspension in the background flow. (III) For $u_{u}(0)>u_{fall}>u_{BG}$ we observe a particle-laden layer outside the fountain which extends from the floor of the tank to a point below the top of the fountain. The density of this lower particle-laden layer equals the density of the collapsing fountain fluid as it passes downwards through this interface. The collapsing fluid then spreads out horizontally through the depth of this particle-laden layer, instead of continuing downwards around the rising fountain. In the lower layer, the negatively buoyant source fluid in fact rises as a negatively buoyant jet, but this transitions into a fountain above the upper interface of the particle-laden layer. The presence of the particles in the lower layer reduces the density difference between fountain and environment, leading to an increase in the fountain height. (IV) If $u_{fall}<u_{BG}$ then an ascending front of particles rises above the fountain and eventually fills the entire tank up to the level where fluid is removed from the tank. We compare the results of a series of new laboratory experiments with simple theoretical investigations for each case, and discuss the relevance of our results.

Diagnosis of 3D Vertical Circulation in the Upwelling and Frontal Zones East of Hainan Island, China

AbstractUsing the generalized omega equation and cruise observations in July 2012, this study analyzes the 3D vertical circulation in the upwelling region and frontal zone east of Hainan Island, China. The results show that there is a strong frontal zone in subsurface layer along the 100-m isobath, which is characterized by density gradient of O(10−4) kg m−4 and vertical eddy diffusivity of O(10−5–10−4) m2 s−1. The kinematic deformation term SDEF, ageostrophic advection term SADV, and vertical mixing forcing term SMIX are calculated from the observations. Their distribution patterns are featured by banded structure, that is, alternating positive–negative alongshore bands distributed in the cross-shelf direction. Correspondingly, alternating upwelling and downwelling bands appear from the coast to the deep waters. The maximum downward velocity reaches −5 × 10−5 m s−1 within the frontal zone, accompanied by the maximum upward velocity of 7 × 10−5 m s−1 on two sides. The dynamic diagnosis indicates that SADV contributes most to the coastal upwelling, while term SDEF, which is dominated by the ageostrophic component SDEFa, plays a dominant role in the frontal zone. The vertical mixing forcing term SMIX, which includes the momentum and buoyancy flux terms SMOM and SBUO, is comparable to SDEF and SADV in the upper ocean, but negligible below the thermocline. The effect of the vertical mixing on the vertical velocity is mainly concentrated at depths with relatively large eddy diffusivity and eddy diffusivity gradient in the frontal zone.

First detection of the supersonic upward plasma flow structures in the early morning sector

AbstractWe present the first observations of the supersonic updrafting plasma drifts in the predawn sector. Two DMSP satellites quasi‐simultaneously detected two fast‐speed events: one of ~385 km spatial extension and with the maximum upward velocity of 1683 m/s appeared at ~3 LT, and the other of ~1500 km large with maximum speed of 1770 m/s occurred at ~5 LT. Both supersonic structures were observed above the eastern Pacific region, separated by ~35° of longitude in space and by 45 min in time. The events occurred at the recovery phase of the geomagnetic storm of 19 February 2014, during rapid oscillations of the interplanetary magnetic field Bz and the interplanetary electric field Ey components, which increased the eastward electric field in the equatorial nighttime ionosphere and triggered the generation of plasma irregularities. The storm time penetration electric fields seem to be the principal driver of the observed supersonic events.

Slippery Thermals and the Cumulus Entrainment Paradox*

Abstract In numerical simulations of growing congestus clouds, the maximum upward velocities w typically occur in compact toroidal vortices or thermals. These maxima were tracked, and the momentum budget was analyzed within spherical regions centered on them with objectively determined radii approximately enclosing the vortex ring or pair. Such regions are proposed as an advantageous prototype for rising air parcels due to their prolonged identity as evident in laboratory flows. Buoyancy and other forces are generally less than 0.02 m s−2 (0.7 K). In particular, resolved mixing between thermals and their environment fails to produce the drag normally anticipated, often producing even a slight upward force, indicating that parcel models should allow for significantly different dilution rates for momentum than for material properties. A conceptual model is proposed to explain this as a result of the thermals' internal circulation and detrainment characteristics. The implications of momentum dilution for cumulus development are explored using a simple model of a heterogeneous entraining parcel. Without friction, parcels reach the upper troposphere even at a high entrainment rate [~(2 km)−1] if the environment is sufficiently humid, whereas with standard momentum dilution, a much lower entrainment rate is required. Peak condensed water amounts and sensitivities of cloud amount and height to ambient humidity are significantly more realistic in the high-entrainment case. This suggests that revised treatments of friction and momentum could help address the “entrainment paradox” whereby entrainment rates implied by detailed cloud studies are higher than those typically preferred for parcel-based calculations.

CHROMOSPHERIC EVAPORATION IN SOLAR FLARE LOOP STRANDS OBSERVED WITH THE EXTREME-ULTRAVIOLET IMAGING SPECTROMETER ON BOARDHINODE

The entire profile of the Fe XXIII line at 263.8 ?, formed at temperature 14 MK, was blueshifted by an upward velocity ?122 ? 33?km?s?1 when it was first detected by the Extreme-ultraviolet Imaging Spectrometer operating in rapid cadence (11.18?s) stare mode during a C1 solar flare. The entire profile became even more blueshifted over the next two exposures, when the upward velocity reached its maximum of ?208 ? 14?km?s?1 before decreasing to zero over the next 12 exposures. After that, a weak, secondary blueshifted component appeared for five exposures, reached a maximum upward velocity of ?206 ? 33?km?s?1, and disappeared after the maximum line intensity (stationary plus blueshifted) was achieved. Velocities were measured relative to the intense stationary profile observed near the flare's peak and early during its decline. The initial episode during which the entire profile was blueshifted lasted about 156?s, while the following episode during which a secondary blueshifted component was detected lasted about 56?s. The first episode likely corresponds to chromospheric evaporation in a single loop strand, while the second corresponds to evaporation in an additional strand, as described in multi-strand flare loop models proposed by Hori et al. and Warren & Doschek. Line emission from progressively cooler ions (Fe XVII, XVI, and XIV) brightened at successively later times, consistent with cooling of flare-heated plasma.

Vertical velocities and biological consequences at a front detected at the balearic sea

An intense oceanic front was detected at the west of Mallorca Island (Balearic sub-basin of the North Western Mediterranean Sea) during an oceanographic survey in December 2009. This contribution analyses the hydrography and geostrophic motions observed at the front, together with the ageostrophic motion derived from the omega equation. The front separated resident Atlantic water (to the north) from more recent Atlantic water (to the south). Maximum upward vertical velocities of 6m/day were found at the northern side of the front, related with relative maxima of dissolved oxygen and fluorescence. The vertical velocities in this study are mainly due to relative vorticity advection. AVISO altimetry data is used to discuss the advection of the front over a nearby mooring equipped with temperature and salinity sensors at 300m below the sea surface. The biological implications of the front are discussed by means of acoustic backscatter data. There is an observed increase in mesopelagic fish biomass at the frontal area. Our hypothesis states that the vertical velocities associated to the front would lead to the observed increase in mesopelagic biomass near the front, which is in agreement with previous studies in other frontal systems.

Dynamics of posterior tongue during pronunciation and voluntary tongue lift movement in young adults

The lifting-up movement of the posterior part of the tongue to touch the palate, which is a requirement for performing physiological functions such as deglutition and speech, is an important phenomenon that is difficult to objectively evaluate. The purpose of this study was to develop a new modality to evaluate the tongue-lifting function, especially in the posterior part of the tongue, and to elucidate the dynamic properties of the tongue in normal subjects. Twenty-three healthy volunteers (9 men and 14 women; mean age, 27·6years) participated in this study. A new device was developed that could evaluate the up-down movement of the posterior part of the tongue in a non-invasive manner. The experimental tasks were as follows: (i) /a/ pronunciation for 1s followed by /ka/ pronunciation (a-ka task), (ii) /a/ pronunciation for 1s followed by /ga/ pronunciation (a-ga task) and (iii) /a/ pronunciation for 1s followed by a voluntary push-up movement of the posterior part of the tongue (a-lift task). Maximum upward velocity in the a-ga task was larger than that in the a-ka task (P<0·05). The a-lift task showed the highest tongue lift range among the three tasks, and the a-ga task showed a higher range than that of the a-ka task (P<0·05). This study revealed that precise quantification of the motility of the posterior part of the tongue, which would be useful in rehabilitation of articulation and/or swallowing, could be achieved using this new device in a non-invasive manner.

A toy model that predicts the qualitative role of bar bend in a push jerk

In this work, we describe a simple coarse-grained model of a barbell that can be used to determine the qualitative role of bar bend during a jerk. In simulations of this model, we observed a narrow time window during which the lifter can leverage the elasticity of the bar in order to lift the weight to a maximal height. This time window shifted to later times as the weight was increased. In addition, we found that the optimal time to initiate the drive was strongly correlated with the time at which the bar had reached a maximum upward velocity after recoiling. By isolating the effect of the bar, we obtained a generalized strategy for lifting heavy weight in the jerk.

漂流ブイの上下揺れに及ぼす粘性流体力の影響

In recent years, a system to measure sea conditions in real time for carrying in a buoy is developed. In this system, wave conditions, those are wave height, period and direction, are obtained from calculating the buoy's motion equation with its accurate response operator functions using measured buoy's motion. Therefore, it is necessary to take the functions in design stage, in order to design for an optimum form of buoy for installed sea area. First, the accuracy of an existing motion calculation program based on potential theory is checked. It is found that the calculation overestimates the harmonic heaving amplitude for some buoy.Then, in order to understand the reasons, the characteristics of the hydrodynamic forces acting on buoy are investigated with a forced heaving motion test. From the flow observation around a buoy using visualization technique, large vortexes shedding under the body in the moment when buoy has maximum upward velocity are observed, and it is confirmed that viscous drag acts on buoy. Using a vertical cylinder model, the viscous drag coefficient acting on aft-body in the moment when the model has maximum upward velocity is measured by the forced heaving motion test for several KC numbers and 2D CFD calculation based on CIP method is also carried out, and the characteristics of the viscous drag are investigated and an empirical estimation formula is presented. Finally, a motion calculation including the viscous drag is carried out and the results are compared with measured results. It is confirmed that the calculated results are improved and shows good agreement with measured results.

Target Detection in SAR Images Based on a Level Set Approach

This paper introduces a new framework for point target detection in synthetic aperture radar (SAR) images. We focus on the task of locating reflective small regions using a level-set-based algorithm. Unlike most of the approaches in image segmentation, we address an algorithm that incorporates speckle statistics instead of empirical parameters and also discards speckle filtering. The curve evolves according to speckle statistics, initially propagating with a maximum upward velocity in homogeneous areas. Our approach is validated by a series of tests on synthetic and real SAR images and compared with three other segmentation algorithms, demonstrating that it configures a novel and efficient method for target-detection purpose.

Dynamics of Vertical Displacement in Porous Media Associated With CO2 Sequestration

Summary The problem of CO2 sequestration in geologic formations is analyzed from a fundamental perspective. In order to clearly understand the first order behavior of the system, the mechanisms of trapping, dissolution and chemical reactions are not accounted for. The analysis is concerned with the post-injection period when the CO2 plume rises due to buoyancy. Characteristics of the plume for a 1D problem show that a pair of shocks moving in opposite directions is produced at the top end. The downward moving shock interacts with the bottom end of the plume resulting in a decrease in the maximum value of the CO2 saturation. High accuracy numerical simulations are employed to understand the 2D mechanisms of plume evolution in terms of the viscosity ratio and the capillary number. 2D results show that the plume rises to significantly lower depth, in shorter times, as compared to the 1D problem. This behavior is governed by the 2D velocity field around the plume that additionally leads to spanwise wave interactions and results in a faster decrease of the maximum CO2 saturation. The initial dimensions of the plume have a strong influence on the time scales of the wave interactions. The maximum upward velocity that is generated due to buoyancy is closely related to the maximum saturation and decays rapidly to very small values with a decrease in saturation. In the case where the viscosity of CO2 is a tenth of the viscosity of the surrounding fluid, the plume rises up about 500 m in 700 yrs. Our results provide an upper bound on the maximum rise distance and the sequestration time for the problem involving trapping and dissolution. Comparison with experimental results show that the buoyancy velocity obtained from our results is of the same order as observed in the experiments.

Entrainment and bending in a major hydrothermal plume, Main Endeavour Field, Juan de Fuca Ridge

[1] We measure expansion rate and bending in a 23-hour time series of acoustic images of the lower 25 m section of a buoyant hydrothermal plume rising from Grotto vent in the Main Endeavour Field, Juan de Fuca Ridge. We then calculate entrainment coefficient, the constant of proportionality relating mean inflow velocity at the plume edge to maximum mean upward velocity within the plume. The plume section alternately bends southwest at relatively high inclinations (37°) and northeast at lower inclinations at irregular intervals twice during this time period, apparently driven by current reversals in the mixed semi-diurnal tidal cycle. The measured expansion rates (0.11–0.25 m/m) and calculated entrainment coefficients (0.07–0.18) are directly proportional to the degree of bending (R2 = 0.75). The loss of buoyancy flux related to enhanced mixing in a stratified environment during bending may contribute to reduction of potential rise height consistent with predicted (∼400 m) and measured (300–350 m) plume tops.

Modulations in the polar mesosphere summer echoes and associated atmospheric gravity waves

Mesospheric observations were made by the EISCAT VHF radar. On one occasion a relatively weak Polar Mesosphere Summer Echo (PMSE) was observed with its intensity varying with a period of about 27 minutes. Immediately below the PMSE layer an atmospheric gravity wave was observed, also with a period of about 27 minutes. The maximum intensity of the PMSE corresponded to the maximum upward velocity associated with the wave. Particle precipitation, adiabatic cooling due to the upward velocity and wave steepening and breaking at the mesopause may all play a role in causing PMSEs.

Daytime lidar measurements of tidal winds in the mesospheric sodium layer at Urbana, Illinois

The first daytime lidar observations of the mesospheric Na layer at Urbana, Illinois (40°N, 88°W), were made in January and March 1986. The data show strong 12‐hour oscillations of the Na density and layer centroid height which appear to be caused by the semidiurnal tide. The peak‐to‐peak variations in column abundance and centroid height were of the order of 100% and 3 km, respectively. The vertical wind velocities were inferred from the temporal variations of the density gradients on the layer topside. The inferred wind amplitudes and vertical wavelengths for the semidiurnal tide were ∼30 cm s−1 and ∼50 km, respectively. The maximum upward vertical velocity occurs at about 1100 LST and 2300 LST.

Tidal oscillations in the atmospheric sodium layer

The vertical distribution of atmospheric sodium has been measured at São José dos Campos (23°S, 46°W) over a total of about 20 complete diurnal cycles between April and August 1981. Average time variations of the sodium density show strong oscillations with 12‐ and 24‐hour periods. Both the diurnal and semidiurnal components of the oscillation display large amplitudes and a 180° phase inversion near the layer peak. These features are interpreted in terms of the propagation of tides in the layer, taking into account the interaction between the tide and the minor constituent layer. It is shown that the vertical wind is the most important factor that determines the amplitude of the oscillation in sodium density at a fixed height, thus making it possible to estimate the phase and amplitude of the wind oscillations over a limited height range. Diurnal and semidiurnal vertical wind amplitudes of 2–6 cm s−1 and 5–20 cm s−1, respectively, have been inferred. The 12‐hour component shows vertical phase propagation with a wavelength of ∼50 km, in agreement with recent theories. The 24‐hour component, however, shows characteristics of an evanescent mode instead of the expected S1.1 mode. Maximum upward vertical velocity occurs at about 2100 LT at all heights for the diurnal component and at 0600 and 1800 LT at 85 km for the semidiurnal component. These results appear to be the first reported measurements of tidally induced vertical displacements in the mesopause region.