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Articles 1 - 30 of 39
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Maui Mesosphere And Lower Thermosphere (Maui Malt) Observations Of The Evolution Of Kelvin-Helmholtz Billows Formed Near 86 Km Altitude, J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. J. Rudy
Maui Mesosphere And Lower Thermosphere (Maui Malt) Observations Of The Evolution Of Kelvin-Helmholtz Billows Formed Near 86 Km Altitude, J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. J. Rudy
Alan Z Liu
Small-scale (less than 15 km horizontal wavelength) structures known as ripples have been seen in OH airglow images for nearly 30 years. The structures have been attributed to either convective or dynamical instabilities; the latter are mainly due to large wind shears, while the former are produced by superadiabatic temperature gradients. Dynamical instabilities produce Kelvin-Helmholtz (KH) billows, which have been known for many years. However, models and laboratory experiments suggest that these billows often spawn a secondary instability that is convective in nature. While laboratory investigations see evidence of such structures, the evolution of these instabilities in the atmosphere has …
Investigation Of A “Wall” Wave Event, Feng Li, Gary R. Swenson, Alan Z. Liu, Michael Taylor, Yucheng Zhao
Investigation Of A “Wall” Wave Event, Feng Li, Gary R. Swenson, Alan Z. Liu, Michael Taylor, Yucheng Zhao
Alan Z Liu
A bright airglow event was observed at Maui, Hawaii, on the night of 11–12 August 2004 with multiple instruments including a Na wind/temperature lidar, an airglow imager, and a mesospheric temperature mapper. The characteristics of this event were investigated with measurements from these instruments. Analysis showed that this event was caused by a large-amplitude, upward-propagating gravity wave with a period of about 4–5 hours and a vertical wavelength of about 20 km, i.e., a “wall” wave. This wall wave induced dramatic changes in temperature (60 K), airglow intensity (doubled in the OH and tripled in the O2 emissions), and Na …
Gravity Wave Characteristics In The Lower Atmosphere At South Pole, Matt Pfenniger, Alan Z. Liu, George C. Papen, Chester S. Gardner
Gravity Wave Characteristics In The Lower Atmosphere At South Pole, Matt Pfenniger, Alan Z. Liu, George C. Papen, Chester S. Gardner
Alan Z Liu
A 4-year (1993-1996) temperature and wind data set obtained from over 2000 high-resolution balloon soundings at South Pole is used to study gravity wave characteristics in the atmosphere and lower stratosphere. Extensive analyses of energy density, spectra, and static stability are performed to present a comprehensive view of the gravity waves are ubiquitous and often fairly strong at the South Pole, even though the generation mechanisms are not clear. Gravity wave characteristics are, in general, similar to those obtained at other high-latitude southern hemisphere stations. Potential energies vary between about 0.5 J/kg and 5 J/kg with season and altitude. Variations …
Comparison Of Na Lidar And Meteor Radar Wind Measurements At Starfire Optical Range, Nm, Usa, Alan Z. Liu, Wayne K. Hocking, Steven J. Franke, T. Thayaparan
Comparison Of Na Lidar And Meteor Radar Wind Measurements At Starfire Optical Range, Nm, Usa, Alan Z. Liu, Wayne K. Hocking, Steven J. Franke, T. Thayaparan
Alan Z Liu
Simultaneous wind measurements in the mesopause region at Starfire Optical Range near Albuquerque, NM with Na wind/temperature lidar and meteor radar have been performed and compared. 20 nights of hourly data recorded with these two instruments at two layers around 86 and 93 km altitude are compared for both zonal and meridional wind components. The mean values are found to have no statistically significant differences. The correlation coefficients vary between 0.63 and 0.70, indicating that the two sets of measurements are broadly consistent. When comparing the averaged variations over the night, the two measurements are highly correlated, with correlation coefficients …
A Modeling Study Of O2 And Oh Airglow Perturbations Induced By Atmospheric Gravity Waves, Alan Z. Liu, Gary R. Swenson
A Modeling Study Of O2 And Oh Airglow Perturbations Induced By Atmospheric Gravity Waves, Alan Z. Liu, Gary R. Swenson
Alan Z Liu
A one-dimensional model is used to investigate the relations between gravity waves and O2 and OH airglows perturbations. The amplitude and phase of the airglow perturbations induced by gravity waves (with period > 20 min) are calculated for different vertical wavelength (10–50 km) and damping rate. The model shows that for vertically propagating gravity waves, the amplitude of airglow perturbations observed from ground is larger for longer vertical wavelength, because of the smaller cancellation effect within each layer. The ratio of the amplitudes between O2 and OH is smaller for larger wave damping. For upward propagating (downward phase progression) waves, the …
Maintenance Of Circulation Anomalies During The 1988 Drought And 1993 Floods Over The United States, Alan Z. Liu, Mingfang Ting, Hailan Wang
Maintenance Of Circulation Anomalies During The 1988 Drought And 1993 Floods Over The United States, Alan Z. Liu, Mingfang Ting, Hailan Wang
Alan Z Liu
The large-scale circulation anomalies associated with the 1988 drought and the 1993 floods are investigated with the National Centers for Environmental Prediction Reanalysis data and a linear stationary wave model. The transient vorticity and thermal forcings are explicitly calculated and the diabatic heating is derived as a residual in the thermodynamic energy equation. Using the April–June (AMJ) data for 1988, and June–August (JJA) data for 1993, the linear stationary wave model is able to reproduce the main features of the geopotential height anomaly for the two seasons when all forcings are included. This provides a basis for further investigation of …
On The Variability Of Mesospheric Oh Emission Profiles, Romina Nikoukar, Gary R. Swenson, Alan Z. Liu, Farzad Kamalabadi
On The Variability Of Mesospheric Oh Emission Profiles, Romina Nikoukar, Gary R. Swenson, Alan Z. Liu, Farzad Kamalabadi
Alan Z Liu
Mesospheric OH radiance limb profiles measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft were inverted to yield altitude profiles of OH volume emission rates. The Abel inversion results of two months of data (from 1 June to 31 July 2004) were analyzed for the layer mean and standard deviation as a function of latitude and local time. Statistical analysis of SABER data shows that the global difference between the mean and standard deviation profiles for the OH(vu = 7, 8, 9; ∆v = 2) emission …
Observations Of Persistent Leonid Meteor Trails 3. The ‘‘Glowworm’’, Jack D. Drummond, Brent W. Grime, Chester S. Gardner, Alan Z. Liu, Xinzhao Chu, Michael C. Kelley, Craig Kruschwitz, Timothy J. Kane
Observations Of Persistent Leonid Meteor Trails 3. The ‘‘Glowworm’’, Jack D. Drummond, Brent W. Grime, Chester S. Gardner, Alan Z. Liu, Xinzhao Chu, Michael C. Kelley, Craig Kruschwitz, Timothy J. Kane
Alan Z Liu
A spectacular, well-observed Leonid meteor of visual magnitude -14.3 appeared on 17 November 1998 and left a lingering trail, dubbed the Glowworm, that was well studied. From a location on Kirtland Air Force Base, near Albuquerque, New Mexico, we obtained CCD images of the trail from 94 to 203 s after the meteor and recorded a video with an intensified camera for even longer. From information obtained with a sodium lidar half an hour after the meteor, we have determined that a gravity wave with a vertical wavelength of 2.4 km was responsible for the right-angled appearance of the trail. …
Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner
Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner
Alan Z Liu
Vertical heat flux profiles induced by dissipating gravity waves in the mesopause region (85–100 km altitude) are derived from Na lidar measurements of winds and temperatures at Maui (20.7ºN, 156.3ºW), Hawaii, and compared with earlier results from Starfire Optical Range (SOR, 35.0ºN, 106.5ºW), New Mexico. The heat flux profile at SOR has a single downward maximum of 2.25 ± 0.3 K m/s at 88 km, while the profile at Maui has two downward maxima of 1.25 ± 0.5 K m/s and 1.40 ± 0.5 K m/s at 87 and 95 km, respectively. The common maximum below 90 km can be …
Observations Of Persistent Leonid Meteor Trails. 1. Advection Of The "Diamond Ring", Jack D. Drummond, Brent W. Grime, Chester S. Gardner, Alan Z. Liu, Xinzhao Chu, Timothy J. Kane
Observations Of Persistent Leonid Meteor Trails. 1. Advection Of The "Diamond Ring", Jack D. Drummond, Brent W. Grime, Chester S. Gardner, Alan Z. Liu, Xinzhao Chu, Timothy J. Kane
Alan Z Liu
From a single image of a persistent trail left by a -1.5 magnitude Leonid meteor on November 17, 1998, the relative winds between 92.5 and 98 km altitude are derived, where the altitudes are determined by a sodium lidar. These are converted to true winds 82 sec after the appearance of the meteor by fixing the winds at 98 km to match the results of following the trail with the lidar for twelve minutes. The image and winds reveal a fine example of the effects of a gravity wave having a vertical wavelenth of 5.50 ± 0.02 km, a horizontal …
Meteor Trail Advection Observed During The 1998 Leonid Shower, Brent W. Grime, Timothy J. Kane, Alan Liu, George Papen, Chester S. Gardner, Michael C. Kelley, Craig Kruschwitz, Jack Drummond
Meteor Trail Advection Observed During The 1998 Leonid Shower, Brent W. Grime, Timothy J. Kane, Alan Liu, George Papen, Chester S. Gardner, Michael C. Kelley, Craig Kruschwitz, Jack Drummond
Alan Z Liu
Sodium resonance lidar observations of meteor trails are reported from the 1998 Leonid shower experimental at the Starfire Optical Range Kirtland Air Force Base, NM (35.0º N, 106.5º W ). The lidar was operating in a spatially scanning mode that allowed tracking for up to one half-hour. Three trails are presented here whose motion allowed inference of radial as well as vector wind components and apparent diffusivities. The winds are derived independently using the narrow linewidth sodium (Na) resonance Doppler lidar technique and are compared with the tracking results.
Measurements Of Atmospheric Stability In The Mesopause Region At Starfire Optical Range, Nm, Yucheng Zhao, Alan Z. Liu, Chester S. Gardner
Measurements Of Atmospheric Stability In The Mesopause Region At Starfire Optical Range, Nm, Yucheng Zhao, Alan Z. Liu, Chester S. Gardner
Alan Z Liu
The structure and seasonal variations of static (convective) and dynamic (shear) instabilities in the mesopause region (80–105 km) are examined using high-resolution wind and temperature data obtained with a Na lidar at the Starfire Optical Range, NM. The probabilities of static and dynamic instability are sensitive functions of N2/S2, where N is the buoyancy frequency and S is the total vertical shear in the horizontal winds. The mesopause region is most stable in summer when the mesopause is low, N is large and S is small. Monthly mean N2/S2 varies from a maximum value of about 1.06 in mid-summer to …
Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson
Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson
Alan Z Liu
Characteristics of convective and dynamical instabilities in the mesopause region (between 85 and 100 km) over Maui, Hawaii (20.7ºN, 156.3ºW) are investigated using 19 nights, ~133 hours of high-resolution wind and temperature data obtained by the University of Illinois Na wind/temperature lidar during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaigns. The mean probabilities of convective and dynamical instabilities are observed to be ~3 and 10%, respectively, but there is considerable night-to-night variation. At any given time the probability that an unstable condition is found at some altitudes in the 85–100 km range is 90%. The Maui MALT data …
Vertical Dynamical Transport Of Mesospheric Constituents By Dissipating Gravity Waves, Alan Z. Liu, Chester S. Gardner
Vertical Dynamical Transport Of Mesospheric Constituents By Dissipating Gravity Waves, Alan Z. Liu, Chester S. Gardner
Alan Z Liu
Over 400 h of Na wind/temperature lidar observations, obtained at the Star5re Optical Range, NM, are used to study the vertical dynamical transport of Na in the mesopause region between 85 and 100 km. Dynamical transport occurs when dissipating, non-breaking gravity waves impart a net vertical displacement in atmospheric constituents as they propagate through a region. We show that the vertical constituent flux can be related in a simple way to the vertical heat flux. Breaking gravity waves also contribute to eddy transport by generating turbulence. Because eddy transport is a mixing process, it only occurs in the presence of …
Observations Of Gravity Wave Breakdown Into Ripples Associated With Dynamical Instabilities, Feng Li, Alan Z. Liu, Gary R. Swenson, James H. Hecht, Walter A. Robinson
Observations Of Gravity Wave Breakdown Into Ripples Associated With Dynamical Instabilities, Feng Li, Alan Z. Liu, Gary R. Swenson, James H. Hecht, Walter A. Robinson
Alan Z Liu
The breakdown of a high-frequency quasi-monochromatic gravity wave into smallscale ripples in OH airglow was observed on the night of 28 October 2003 at Maui, Hawaii (20.7ºN, 156.3ºW). The ripples lasted ~20 min. The phase fronts of the ripples were parallel to the phase fronts of the breaking wave. The mechanism for the ripple generation is investigated using simultaneous wind and temperature measurements made by a sodium (Na) lidar. The observations suggest that the wave breaking and the subsequent appearance of ripples were related to dynamical (or Kelvin-Helmholtz) instabilities. The characteristics of the ripples, including the alignment of the phase …
Climatology Of Short-Period Gravity Waves Observed Over Northern Australia During The Darwin Area Wave Experiment (Dawex) And Their Dominant Source Regions, P. -D. Pautet, M. J. Taylor, Alan Z. Liu, Gary Swenson
Climatology Of Short-Period Gravity Waves Observed Over Northern Australia During The Darwin Area Wave Experiment (Dawex) And Their Dominant Source Regions, P. -D. Pautet, M. J. Taylor, Alan Z. Liu, Gary Swenson
Alan Z Liu
The Darwin Area Wave Experiment (DAWEX) was designed to investigate the generation and propagation of gravity waves from intense regions of localized convection that occur regularly over northern Australia (in the vicinity of Darwin) during the premonsoon period. This multinational program was conducted during the austral spring 2001 using a range of coordinated optical, radar, and in situ balloon measurements. As part of this program, all-sky image observations of short-period gravity wave events in the near infrared OH nightglow emission (altitude ~87 km) were made from two well-separated sites in northern Australia: Wyndham (15.5ºS, 128.1ºE) and Katherine (14.5ºS, 132.3ºE), over …
Measurements Of Mesospheric Sodium Abundance Above The Hawaiian Islands, Lewis C. Roberts, Jr., L. William Bradford, Christopher R. Neyman, Alan Z. Liu
Measurements Of Mesospheric Sodium Abundance Above The Hawaiian Islands, Lewis C. Roberts, Jr., L. William Bradford, Christopher R. Neyman, Alan Z. Liu
Alan Z Liu
Laser guide stars have increased the utility of adaptive optics systems by expanding the number of observable objects. The most common type of laser excites sodium in the mesosphere, and mesospheric sodium density is key to the performance of the laser. While a variety of observatories have conducted studies of the mesospheric sodium density, there are no published studies from Hawaii, which is home to some of the largest telescopes in the world. This paper presents mesospheric sodium densities measured by the University of Illinois lidar for 165 hr spanning 25 nights over 3 years. The mean sodium column density …
Characteristics Of Quasi-Monochromatic Gravity Waves Observed With Na Lidar In The Mesopause Region At Starfire Optical Range, Nm, Xiong Hu, Alan Z. Liu, Chester S. Gardner, Gary R. Swenson
Characteristics Of Quasi-Monochromatic Gravity Waves Observed With Na Lidar In The Mesopause Region At Starfire Optical Range, Nm, Xiong Hu, Alan Z. Liu, Chester S. Gardner, Gary R. Swenson
Alan Z Liu
The University of Illinois Na wind/temperature lidar data collected at the Starfire Optical Range, NM, between Jan. 1998 and May 2000 was used to extract the dominant monochromatic gravity waves. By using simultaneously measured horizontal wind and temperature profiles, the vertical wavelengths (λz), (TI), and propagation directions were determined using the hodograph method. A total of 700 monochromatic gravity waves were analyzed from ~300 h of observations. It was found that 84.4% of the waves were propagating upwards. The mean λz was 12.6 km and 9.9 km for upward and downward propagating waves, respectively, and showed a bimodal distribution with …
Observational Investigations Of Gravity Wave Momentum Flux With Spectroscopic Imaging, J. Tang, G. R. Swenson, Alan Z. Liu, F. Kamalabadi
Observational Investigations Of Gravity Wave Momentum Flux With Spectroscopic Imaging, J. Tang, G. R. Swenson, Alan Z. Liu, F. Kamalabadi
Alan Z Liu
We apply a newly developed gravity wave momentum flux estimation method to the mesospheric measurements obtained with colocated airglow imager and meteor radar at Maui, Hawaii (20.7ºN, 156.3ºW), during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaign. The method identifies individual quasi-monochromatic gravity waves with periods between 6 and ~40 min, estimates the intrinsic wave parameters, and calculates the momentum fluxes carried by vertically propagating waves. Data taken on 28 October 2003 are analyzed in detail to reveal the relationship between momentum flux and wave parameters. The January, April, July, and October 2003 data are divided into summer and …
Atmospheric Stability And Gravity Wave Dissipation In The Mesopause Region, Chester S. Gardner, Yucheng Zhao, Alan Z. Liu
Atmospheric Stability And Gravity Wave Dissipation In The Mesopause Region, Chester S. Gardner, Yucheng Zhao, Alan Z. Liu
Alan Z Liu
High-resolution temperature profile data collected at the Urbana Atmospheric Observatory (40ºN, 88ºW) and Starfire Optical Range, NM (35ºN, 106.5ºW) with a Na lidar are used to assess the stability of the mesopause region between 80 and 105 km. The mean diurnal and annual temperature profiles demonstrate that in the absence of gravity wave and tidal perturbations, the background atmosphere is statically stable throughout the day and year. Thin layers of instability can be generated only when the combined perturbations associated with tides and gravity waves induce large vertical shears in the horizontal wind and temperature profiles. There is a region …
High Frequency Atmospheric Gravity Wave Damping In The Mesosphere, G. R. Swenson, Alan Z. Liu, F. Li, J. Tang
High Frequency Atmospheric Gravity Wave Damping In The Mesosphere, G. R. Swenson, Alan Z. Liu, F. Li, J. Tang
Alan Z Liu
Correlative measurements of temperature and winds by Na lidar and brightness in OH and O2 Atmospheric band airglow have been made at Albuquerque, NM and Maui, HI for a study of high frequency (period less than 30 minutes) Atmospheric Gravity Waves. Wave studies from four nights have been made and the correlative information describes the intrinsic wave properties with altitude, their damping characteristics, and resulting accelerations to the large scale circulation in the 85-100 km altitude region. Generally, saturated to super-saturated conditions were observed below 95 km. Above this altitude, they were less saturated to freely propagating.
Seasonal Variations Of The Vertical Fluxes Of Heat And Horizontal Momentum In The Mesopause Region At Starfire Optical Range, New Mexico, Chester S. Gardner, Alan Z. Liu
Seasonal Variations Of The Vertical Fluxes Of Heat And Horizontal Momentum In The Mesopause Region At Starfire Optical Range, New Mexico, Chester S. Gardner, Alan Z. Liu
Alan Z Liu
Lidar observations of wind and temperature profiles between 85 and 100 km, conducted at the Starfire Optical Range (SOR), New Mexico, are used to characterize the seasonal variations of the vertical fluxes of heat and horizontal momentum and their relationships to gravity wave activity in this region. The wind and temperature variances exhibit strong 6-month oscillations with maxima during the summer and winter that are about 3 times larger than the spring and fall minima. The vertical heat flux also exhibits strong 6-month oscillations with maximum downward flux during winter and summer. The downward heat flux peaks near 88 km …
Airglow Emissions And Oxygen Mixing Ratios From The Photometer Experiment On The Turbulent Oxygen Mixing Experiment (Tomex), J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. G. Roble, M. F. Larsen, J. H. Clemmons
Airglow Emissions And Oxygen Mixing Ratios From The Photometer Experiment On The Turbulent Oxygen Mixing Experiment (Tomex), J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. G. Roble, M. F. Larsen, J. H. Clemmons
Alan Z Liu
The Turbulent Oxygen Mixing Experiment (TOMEX) combined Na lidar measurements from Starfire Optical Range in Albuquerque, New Mexico, with a launch of a payload from White Sands Missile Range (WSMR), located a little over 100 km from Starfire. The payload included a trmethyl aluminum release to measure winds and diffusion, a 5-channel ionization gauge to measure neutral densities, and a 3-channel photometer experiment to measure atomic oxygen related airglow. The payload was launched at 0957 UT on 26 October 2000 and successfully obtained data from all the experiments. The photometer experiment consisted of three liquid nitrogen cooled filter photometers which …
Tomex: Mesospheric And Lower Thermospheric Diffusivities And Instability Layers, R. L. Bishop, M. F. Larsen, J. H. Hecht, Alan Z. Liu, C. S. Gardner
Tomex: Mesospheric And Lower Thermospheric Diffusivities And Instability Layers, R. L. Bishop, M. F. Larsen, J. H. Hecht, Alan Z. Liu, C. S. Gardner
Alan Z Liu
The Turbulent Oxygen Mixing Experiment (TOMEX), which was carried out at White Sands Missile Range in New Mexico on 26 October 2000, included a rocketborne trimethyl aluminum (TMA) chemical tracer experiment. The subsequent TMA trails provided detailed information about the horizontal neutral wind, turbulence, and diffusivity properties of the atmosphere between approximately 85 and 140 km altitude. Measurements with the University of Illinois Na wind/temperature lidar located at the Starfire Optical Range, NM, provided a detailed time history of the stability properties between 85 and 105-km altitude, including high-resolution wind and temperature measurements prior to and during the chemical tracer …
Estimation Of Gravity Wave Momentum Flux With Spectroscopic Imaging, Jing Tang, Farzad Kamalabadi, Steven J. Franke, Alan Z. Liu, Gary R. Swenson
Estimation Of Gravity Wave Momentum Flux With Spectroscopic Imaging, Jing Tang, Farzad Kamalabadi, Steven J. Franke, Alan Z. Liu, Gary R. Swenson
Alan Z Liu
Atmospheric gravity waves play a significant role in the dynamics and thermal balance of the upper atmosphere. In this paper, we present a novel technique for automated and robust calculation of momentum flux of high-frequency quasi-monochromatic wave components from spectroscopic imaging and horizontal radar wind measurements. Our approach uses the two-dimensional (2-D) cross periodogram of two consecutive Doppler-shifted time-differenced (TD) images to identify wave components and estimate intrinsic wave parameters. Besides estimating the average perturbation of dominant waves in the whole field of view, this technique applies 2-D short-space Fourier transform to the TD images to identify localized wave events. …
Tomographic Imaging Of Airglow From Airborne Spectroscopic Measurements, D. Scott Anderson, Gary Swenson,, Farzad Kamalabadi, Alan Liu
Tomographic Imaging Of Airglow From Airborne Spectroscopic Measurements, D. Scott Anderson, Gary Swenson,, Farzad Kamalabadi, Alan Liu
Alan Z Liu
A description is given of the methodology based on a single, aircraft-mounted spectroscopic imager to tomographically reconstruct airglow perturbations induced by atmospheric gravity waves. In this configuration, the imager passes under the airglow structure to gather multiple-angle views of the wave structure in a relatively short amount of time. Under the assumption that the airglow structure does not change significantly during the acquisition interval, the data can be tomographically inverted to estimate the 2D (horizontal–vertical) airglow structure. We develop an inversion strategy for this image formation task and illustrate its applicability by inverting time-sequential imaging data taken from different vantage …
High Frequency Gravity Waves Observed In Oh Airglow At Starfire Optical Range, Nm: Seasonal Variations In Momentum Flux, Jing Tang, Alan Z. Liu, Gary R. Swenson
High Frequency Gravity Waves Observed In Oh Airglow At Starfire Optical Range, Nm: Seasonal Variations In Momentum Flux, Jing Tang, Alan Z. Liu, Gary R. Swenson
Alan Z Liu
Airglow imager and Na wind/temperature lidar measurements at Starfire Optical Range, New Mexico (35ºN, 107ºW) are used to estimate the seasonal variation of the vertical fluxes of horizontal momentum carried by high frequency Atmospheric Gravity Waves (AGWs). The cross-correlation coefficients between the vertical and horizontal wind perturbations were calculated from the OH airglow imager data collected during 32 nights in 1998, 1999 and 2000. The RMS wind velocities were deduced from the lidar measurements. The combined information was used to estimate the upper limit of the momentum flux. The meridional component of the vertical flux of horizontal momentum was observed …
O(1s), Oh, And O2(B) Airglow Layer Perturbations Due To Agws And Their Implied Effects On The Atmosphere, Fabio Vargas, Gary Swenson, Alan Liu, Delano Gobbi
O(1s), Oh, And O2(B) Airglow Layer Perturbations Due To Agws And Their Implied Effects On The Atmosphere, Fabio Vargas, Gary Swenson, Alan Liu, Delano Gobbi
Alan Z Liu
The O(1S) (green line) night airglow emission in response to atmospheric gravity wave (AGW) perturbations was simulated with a linear, one-dimensional model. The results were combined with previously modeled O2(b, 0–1) atmospheric band and OH Meinel band emission response (Liu and Swenson, 2003) to derive amplitude and phase relations among multiple airglow layers in response to gravity waves with various intrinsic parameters and damping rates (β). The simulations show that the vertical profile of the standard deviation of the perturbed green line volume emission rate (VER) has a centroid altitude that is 3 km …
Observations Of Overturning In The Upper Mesosphere And Lower Thermosphere, M. F. Larsen, Alan Z. Liu, C. S. Gardner, M. C. Kelley, S. Collins, J. Friedman, J. H. Hecht
Observations Of Overturning In The Upper Mesosphere And Lower Thermosphere, M. F. Larsen, Alan Z. Liu, C. S. Gardner, M. C. Kelley, S. Collins, J. Friedman, J. H. Hecht
Alan Z Liu
A number of observations of the sodium density primarily in the mesosphere and lower thermosphere (but also of the electron density structure) have shown what appears to be overturning or convective roll cells near the transition from the mesosphere to the lower thermosphere. The cells are found in the region between 95 and 105 km and occur near the boundary between the region of lower stability in the mesosphere and the region of higher stability in the lower thermosphere. The vertical scale for the rolls is ~5–6 km, and the timescale is ~1–3 hours. The rolls occur in a region …
Seasonal And Nocturnal Variations Of The Mesospheric Sodium Layer At Starfire Optical Range, New Mexico, Hu Xiong, Chester S. Gardner, Alan Z. Liu
Seasonal And Nocturnal Variations Of The Mesospheric Sodium Layer At Starfire Optical Range, New Mexico, Hu Xiong, Chester S. Gardner, Alan Z. Liu
Alan Z Liu
The seasonal variations of the mesospheric sodium layer structure over Starfire Optical Range (SOR: 35ºN, 106.5ºW), New Mexico are characterized using 46 night data of Na wind/temperature lidar observations collected from Jan. 1998 to May 2000. The column abundance has a mean value of 5.06 x 109 cm -2 and strong annual oscillations of with a maximum in November and a minimum in June and July. The annual mean rms width of the sodium layer is 4.30 km and the mean centroid height is 91.60 km. Semiannual oscillations are evident in seasonal variations of the rms width and the centroid …