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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Gravity Waves Emitted From Kelvin-Helmholtz Instabilities, Alan Z. Liu, Wenjun Dong, David C. Fritts, Thomas S. Lunda, Han-Li Liu
Gravity Waves Emitted From Kelvin-Helmholtz Instabilities, Alan Z. Liu, Wenjun Dong, David C. Fritts, Thomas S. Lunda, Han-Li Liu
Publications
Fritts, Wang, Lund, and Thorpe (2022, https://doi.org/10.1017/jfm.2021.1085) and Fritts, Wang, Thorpe, and Lund (2022, https://doi.org/10.1017/jfm.2021.1086) described a 3-dimensional direct numerical simulation of interacting Kelvin-Helmholtz instability (KHI) billows and resulting tube and knot (T&K) dynamics that arise at a stratified shear layer defined by an idealized, large-amplitude inertia-gravity wave. Using similar initial conditions, we performed a high-resolution compressible simulation to explore the emission of GWs by these dynamics. The simulation confirms that such shear can induce strong KHI with large horizontal scales and billow depths that readily emit GWs having high frequencies, small horizontal wavelengths, and large vertical group velocities. The …
Mesosphere And Lower Thermosphere Changes Associated With The 2 July 2019 Total Eclipse In South America Over The Andes Lidar Observatory, Cerro Pachon, Chile, A. Liu, F. Vargas, G. Swenson, C. Segura, P. Vega, J. Fuentes, D. Pautet, M. Taylor, Y. Zhao, Y. Morton, H. Bourne
Mesosphere And Lower Thermosphere Changes Associated With The 2 July 2019 Total Eclipse In South America Over The Andes Lidar Observatory, Cerro Pachon, Chile, A. Liu, F. Vargas, G. Swenson, C. Segura, P. Vega, J. Fuentes, D. Pautet, M. Taylor, Y. Zhao, Y. Morton, H. Bourne
Publications
This article presents the results of a week of observations around the 2 July 2019, total Chilean eclipse. The eclipse occurred between 19:22 and 21:46 UTC, with complete sun disc obscuration at 20:38–20:40 UTC (16:38–16:40 LT) over the Andes Lidar Observatory (ALO) at (30.3°S, 70.7°W). Observations were carried out using ALO instrumentation with the goal to observe possible eclipse-induced effects on the mesosphere and lower thermosphere region (MLT; 75–105 km altitude). To complement our data set, we have also utilized TIMED/SABER temperatures and ionosonde electron density measurements taken at the University of La Serena's Juan Soldado Observatory. Observed events include …
Statistical Spectral Characteristics Of Three-Dimensional Winds In The Mesopause Region Revealed By The Andes Lidar, Qian Li, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Kai Ming Huang, Yun Gong, Quan Gan, Yan Ying Yan, Hang Liu
Statistical Spectral Characteristics Of Three-Dimensional Winds In The Mesopause Region Revealed By The Andes Lidar, Qian Li, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Kai Ming Huang, Yun Gong, Quan Gan, Yan Ying Yan, Hang Liu
Publications
By analyzing data recorded at the Andes Lidar Observatory in Cerro Pachon, Chile (30.3°S, 70.7°W) from May 2014 to July 2019, we investigated the fundamental features of three-dimensional wind and temperature spectra. The vertical wavenumber spectral amplitudes of horizontal winds show obvious seasonal variations that are closely related to the seasonal variations in the source and background winds. The wavenumber spectral slopes of the horizontal winds are systematically less negative than −3, with mean values of −1.96 and −2.18 for zonal and meridional winds, respectively. The zonal and meridional wind frequency spectra have mean slopes of −1.37 and −1.56, respectively; …
Evidence For Horizontal Blocking And Reflection Of A Small-Scale Gravity Wave In The Mesosphere, N. R. Criddle, C. Heale, J. Snively, P. -D. Pautet, T. Yuan, Y. Zhao, M. J. Taylor
Evidence For Horizontal Blocking And Reflection Of A Small-Scale Gravity Wave In The Mesosphere, N. R. Criddle, C. Heale, J. Snively, P. -D. Pautet, T. Yuan, Y. Zhao, M. J. Taylor
Publications
The variations of the horizontal phase velocity of an internal gravity wave, generated by wave “blocking” or “reflection” due to an inhomogeneous wind field, have been predicted theoretically and numerically investigated but had yet to be captured experimentally. In this paper, through a collaborative observation campaign using a sodium (Na) Temperature/Wind lidar and a collocated Advanced Mesospheric Temperature Mapper (AMTM) at Utah State University (USU), we report the first potential evidence of such a unique gravity wave process. The study shows that a small-scale wave, captured by the AMTM, with initial observed horizontal phase velocity of 37 ± 5 m/s …
Gravity-Wave-Induced Variations In Exothermic Heating In The Low-Latitude, Equinox Mesophere And Lower Thermosphere Region, Michael P. Hickey Ph.D., Tai-Yin Huang
Gravity-Wave-Induced Variations In Exothermic Heating In The Low-Latitude, Equinox Mesophere And Lower Thermosphere Region, Michael P. Hickey Ph.D., Tai-Yin Huang
Publications
We investigate gravity-wave-induced variations in exothermic heating in the OH nightglow region at a latitude of 18° in the Northern and Southern Hemispheres during March. An OH nightglow chemistry model with gravity wavefields from a spectral full-wave model is used for the investigation. Our simulation results show that the wave packet induces a large secular increase in the number densities of the minor species involved in the OH chemistry, a 50% increase in O3, 42% in O, and 29% in OH (v= 8), and the ultimate driver for these increases is the wave-driven downward transport of O. We find that …
Gravity Wave Heating And Cooling Of The Thermosphere: Sensible Heat Flux And Viscous Flux Of Kinetic Energy, Michael P. Hickey Ph.D., R. L. Walterscheid, G. Schubert
Gravity Wave Heating And Cooling Of The Thermosphere: Sensible Heat Flux And Viscous Flux Of Kinetic Energy, Michael P. Hickey Ph.D., R. L. Walterscheid, G. Schubert
Publications
Total wave heating is the sum of the convergence of the sensible heat flux and the divergence of the viscous flux of wave kinetic energy. Numerical simulations, using a full-wave model of the viscous damping of atmospheric gravity waves propagating in a nonisothermal atmosphere, are carried out to explore the relative contributions of these sources of wave heating as a function of wave properties and altitude. It is shown that the sensible heat flux always dominates in the lower thermosphere, giving a lower region of heating and an upper stronger region of cooling. The heating due to the divergence of …
The 2009 Samoa And 2010 Chile Tsunamis As Observed In The Ionosphere Using Gps Total Electron Content, David A. Galvan, Attila Komjathy, Michael P. Hickey Ph.D., Anthony J. Mannucci
The 2009 Samoa And 2010 Chile Tsunamis As Observed In The Ionosphere Using Gps Total Electron Content, David A. Galvan, Attila Komjathy, Michael P. Hickey Ph.D., Anthony J. Mannucci
Publications
Ground‐based Global Positioning System (GPS) measurements of ionospheric total electron content (TEC) show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events: the Samoa earthquake of 29 September 2009 and the Chile earthquake of 27 February 2010. Both earthquakes produced ocean tsunamis that were destructive to coastal communities near the epicenters, and both were observed in tidal gauge and buoy measurements throughout the Pacific Ocean. We observe fluctuations in TEC correlated in time, space, and wave properties with these tsunamis using the Jet Propulsion Laboratory’s Global Ionospheric Mapping software. These TEC measurements were …
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
Physical Sciences - Daytona Beach
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 …
Unstable Layers In The Mesopause Region Observed With Na Lidar During The Turbulent Oxygen Mixing Experiment (Tomex) Campaign, Alan Z. Liu, Raymond G. Roble, James H. Hecht, Miguel F. Larsen, Chester S. Gardner
Unstable Layers In The Mesopause Region Observed With Na Lidar During The Turbulent Oxygen Mixing Experiment (Tomex) Campaign, Alan Z. Liu, Raymond G. Roble, James H. Hecht, Miguel F. Larsen, Chester S. Gardner
Physical Sciences - Daytona Beach
The Na wind/temperature lidar located at Starfire Optical Range near Albuquerque, New Mexico, provided real time measurements of wind, temperature, and Na density in the mesopause region during the TOMEX rocket campaign in October 2000. The state of the atmosphere in which the rocket was launched into was examined using the lidar measurements. Both convectively and dynamically unstable layers were observed at various times and altitudes during the night. The low convective stability region below 90 km was found to be associated with the diurnal tide. The unstable layers are the combined results of wave and tidal perturbations. Comparison with …
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
Physical Sciences - Daytona Beach
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 …
Further Investigations Of A Mesospheric Inversion Layer Observed In The Aloha-93 Campaign, Tai-Yin Huang, Michael P. Hickey Ph.D., Tai-Fu Tuan
Further Investigations Of A Mesospheric Inversion Layer Observed In The Aloha-93 Campaign, Tai-Yin Huang, Michael P. Hickey Ph.D., Tai-Fu Tuan
Publications
Temperature and wind data obtained from a Na wind/temperature lidar operated by the University of Illinois group during the Airborne Lidar and Observations of the Hawaiian Airglow (ALOHA-93) Campaign, previously analyzed by Huang et al. [1998] using an isothermal Brunt-Va¨isa¨la¨ frequency, have been reexamined to include temperature gradients in the calculation of the Richardson number. In the previous analysis using the isothermal Brunt-Va¨isa¨la¨ frequency the existence of convective instability could not be assessed. New analysis shows that the nonisothermal Richardson number preserves some features found previously, with some striking differences noticable at times between 0900 and 1030 UT. The nonisothermal …
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
Physical Sciences - Daytona Beach
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 …