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Articles 31 - 60 of 268
Full-Text Articles in Atmospheric Sciences
Extreme Horizontal Wind Perturbations In The Mesosphere And Lower Thermosphere Over South America Associated With The 2022 Hunga Eruption, Facundo L. Poblet, Jorge L. Chau, J. Federico Conte, Juha Vierinen, Jose Suclupe, Alan Liu, Rodolfo R. Rodriguez
Extreme Horizontal Wind Perturbations In The Mesosphere And Lower Thermosphere Over South America Associated With The 2022 Hunga Eruption, Facundo L. Poblet, Jorge L. Chau, J. Federico Conte, Juha Vierinen, Jose Suclupe, Alan Liu, Rodolfo R. Rodriguez
Publications
On 15 January 2022, the Hunga volcano produced a massive explosion that generated perturbations in the entire atmosphere. Nonetheless, signatures in the mesosphere and lower thermosphere (MLT) have been challenging to identify. We report MLT horizontal wind perturbations using three multistatic specular meteor radars on the west side of South America (spanning more than 3,000 km). The most notorious signal is an exceptional solitary wave with a large vertical wavelength observed around 18 UT at all three sites, with an amplitude of ∼50 m/s mainly in the westward direction. Using a customized analysis, the wave is characterized as traveling at …
Accelerating Atmospheric Gravity Wave Simulations Using Machine Learning: Kelvin-Helmholtz Instability And Mountain Wave Sources Driving Gravity Wave Breaking And Secondary Gravity Wave Generation, Wenjun Dong, David Fritts, Alan Z. Liu, Hanli Liu, Jonathan Snively
Accelerating Atmospheric Gravity Wave Simulations Using Machine Learning: Kelvin-Helmholtz Instability And Mountain Wave Sources Driving Gravity Wave Breaking And Secondary Gravity Wave Generation, Wenjun Dong, David Fritts, Alan Z. Liu, Hanli Liu, Jonathan Snively
Publications
Gravity waves (GWs) and their associated multi-scale dynamics are known to play fundamental roles in energy and momentum transport and deposition processes throughout the atmosphere. We describe an initial, two-dimensional (2-D), machine learning model – the Compressible Atmosphere Model Network (CAMNet) - intended as a first step toward a more general, three-dimensional, highly-efficient, model for applications to nonlinear GW dynamics description. CAMNet employs a physics-informed neural operator to dramatically accelerate GW and secondary GW (SGW) simulations applied to two GW sources to date. CAMNet is trained on high-resolution simulations by the state-of-the-art model Complex Geometry Compressible Atmosphere Model (CGCAM). Two …
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 …
Analysis Of Energy Transfer Among Background Flow, Gravity Waves And Turbulence In The Mesopause Region In The Process Of Gravity Wave Breaking From A High-Resolution Atmospheric Model, Fan Yang, Alan Z. Liu, Christopher J. Heale, Jonathan B. Snively, Wenjun Dong, Thomas Lund
Analysis Of Energy Transfer Among Background Flow, Gravity Waves And Turbulence In The Mesopause Region In The Process Of Gravity Wave Breaking From A High-Resolution Atmospheric Model, Fan Yang, Alan Z. Liu, Christopher J. Heale, Jonathan B. Snively, Wenjun Dong, Thomas Lund
Publications
We conducted an analysis of the process of GW breaking from an energy perspective using the output from a high-resolution compressible atmospheric model. The investigation focused on the energy conversion and transfer that occur during the GW breaking. The total change in kinetic energy and the amount of energy converted to internal energy and potential energy within a selected region were calculated. Prior to GW breaking, part of the potential energy is converted into kinetic energy, most of which is transported out of the chosen region. After the GW breaks and turbulence develops, part of the potential energy is converted …
Analysis Of Energy Transfer Among Background Flow, Gravity Waves And Turbulence In The Mesopause Region In The Process Of Gravity Wave Breaking From A High-Resolution Atmospheric Model, Alan Z. Liu, Fan Yang, Christopher James Heale, Jonathan Brian Snively, Wenjun Dong, Thomas Lund
Analysis Of Energy Transfer Among Background Flow, Gravity Waves And Turbulence In The Mesopause Region In The Process Of Gravity Wave Breaking From A High-Resolution Atmospheric Model, Alan Z. Liu, Fan Yang, Christopher James Heale, Jonathan Brian Snively, Wenjun Dong, Thomas Lund
Publications
We conducted an analysis of the process of GW breaking from an energy perspective using the output from a high-resolution compressible atmospheric model. The investigation focused on the energy conversion and transfer that occur during the GW breaking. The total change in kinetic energy and the amount of energy converted to internal energy and potential energy within a selected region were calculated.
Prior to GW breaking, part of the potential energy is converted into kinetic energy, most of which is transported out of the chosen region. After the GW breaks and turbulence develops, part of the potential energy is converted …
Gravity Wave Drag Parameterizations For Earth’S Atmosphere, Christopher J. Heale, Christopher G. Kruse, Jadwiga H. Richter, M. Joan Alexander, Julio T. Bacmeister, Junhong Wei
Gravity Wave Drag Parameterizations For Earth’S Atmosphere, Christopher J. Heale, Christopher G. Kruse, Jadwiga H. Richter, M. Joan Alexander, Julio T. Bacmeister, Junhong Wei
Publications
Atmospheric gravity waves (GWs), or buoyancy waves, transport momentum and energy through Earth’s atmosphere. GWs are important at nearly all levels of the atmosphere, though, the momentum they transport is particularly important in general circulation of the middle and upper atmosphere. Primary sources of atmospheric GWs are flow over mountains, moist convection, and imbalances in jet/frontal systems. Secondary GWs can also be generated as a result of dissipation of a primary GWs. Gravity waves typically have horizontal wavelengths of 10’s to 100’s of kilometers, though, they can have scales of 1’s to 1000’s of kilometers as well. Current effective resolutions …
On A Guiding Of Whistler-Mode Waves By Density Gradients, Anatoly V. Streltsov
On A Guiding Of Whistler-Mode Waves By Density Gradients, Anatoly V. Streltsov
Publications
Observations from satellites demonstrate that in the magnetosphere, VLF whistler-mode waves are frequently detected in the narrow transition regions, where the plasma density changes its magnitude over a short distance across the ambient magnetic field. These observations suggest that the small-scale, isolated density gradients can guide the VLF whistler-mode waves along the field. We investigate the guiding of the whistler-mode waves by the transverse density gradients with a size much less than the characteristic perpendicular size of the wave. We found analytical solutions describing these waves in the plasma with a sharp density discontinuity between two homogeneous regions, and confirm …
Wavenumbers 3 And 4 Quasi 2-Day Wave Activities Observed By Multiple Meteor Radars In The Two Hemispheres During Austral Summer, Hao Cheng, Kai Ming Huang, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Yun Gong
Wavenumbers 3 And 4 Quasi 2-Day Wave Activities Observed By Multiple Meteor Radars In The Two Hemispheres During Austral Summer, Hao Cheng, Kai Ming Huang, Alan Z. Liu, Shao Dong Zhang, Chun Ming Huang, Yun Gong
Publications
Combining observations from three meteor radars in the Northern Hemisphere (NH) and a meteor radar in the Southern Hemisphere (SH) and reanalysis data, we present successive wavenumbers 3 and 4 (W3 and W4) quasi 2 day wave activities in austral summer. In the mesosphere and lower thermosphere, the wave exhibits two burst activities. The W3 dominates the first burst, while the W4 is the predominate mode in the second burst. The mode transition arises in the late January and is completed around the end of January. The W3 and W4 have the nearly same dominate period of about 46 hr …
Coupling Evidence From Lower Atmosphere To Mesosphere And Ionosphere Through Quasi 27-Day Oscillation, Alan Z. Liu, Kaiming Huang, Hao Cheng, Shaodong Zhang, Chunming Huang, Yun Gong, Gang Chen
Coupling Evidence From Lower Atmosphere To Mesosphere And Ionosphere Through Quasi 27-Day Oscillation, Alan Z. Liu, Kaiming Huang, Hao Cheng, Shaodong Zhang, Chunming Huang, Yun Gong, Gang Chen
Publications
Using meteor radar, radiosonde and digisonde observations and MERRA-2 reanalysis data from 12 August to 31 October 2006, we report a dynamical coupling from the tropical lower atmosphere to the mesosphere and ionospheric F2 region through a quasi 27-day intraseasonal oscillation (ISO). It is interesting that the quasi 27-day ISO is active in the troposphere and stratopause and mesopause regions, exhibiting a three-layer structure. In the mesosphere and lower thermosphere (MLT), the amplitude in the zonal wind increases from about 4 ms at 90 km to 15 ms at 100 km, which is different from previous observations that ISOs generally …
The Dynamics Of Tsunamigenic Acoustic-Gravity Waves And Bathymetry Effect, Pavel Alexandrovich Inchin, Christopher James Heale, Jonathan Brian Snively, Matthew David Zettergren
The Dynamics Of Tsunamigenic Acoustic-Gravity Waves And Bathymetry Effect, Pavel Alexandrovich Inchin, Christopher James Heale, Jonathan Brian Snively, Matthew David Zettergren
Publications
The investigation of atmospheric tsunamigenic acoustic and gravity wave (TAGW) dynamics, from the ocean surface to the thermosphere, is performed through the numerical computations of the 3D compressible nonlinear Navier-Stokes equations. Tsunami propagation is first simulated using a nonlinear shallow water model, which incorporates instantaneous or temporal evolutions of initial tsunami distributions (ITD). Surface dynamics are then imposed as a boundary condition to excite TAGWs into the atmosphere from the ground level. We perform a case study of a large tsunami associated with the 2011 M9.1 Tohuku-Oki earthquake, and parametric studies with simplified and demonstrative bathymetry and ITD. Our results …
Climatology Of High-Frequency Gravity Waves Observed By An Airglow Imager At Andes Lidar Observatory, Alan Z. Liu, Bing Cao
Climatology Of High-Frequency Gravity Waves Observed By An Airglow Imager At Andes Lidar Observatory, Alan Z. Liu, Bing Cao
Publications
The long-term climatology of high-frequency quasi-monochromatic gravity waves is presented using multi-year airglow images observed at Andes Lidar Observatory (ALO, 30.3ºS, 70.7ºW) in northern Chile. A large number of high-frequency gravity waves were retrieved from OH airglow images. The distribution of primary wave parameters including horizontal wavelength, vertical wavelength, intrinsic wave speed, and intrinsic wave period are obtained and are in the ranges of 20–30 km, 15–25 km, 50–100 ms-1, and 5–10 min, respectively. The waves tend to propagate against the local background winds and show clear seasonal variations. In austral winter (Ma–Aug), the observed wave occurrence frequency is higher …
Meteor Radar Vertical Wind Observation Biases And Mathematical Debiasing Strategies Including The 3dvar+Div Algorithm, Alan Z. Liu, Zishun Qiao, Gunter Stober, Alexander Kozlovsky, Ales Kuchar, Christoph Jacobi, Chris Meek, Diego Janches, Guiping Liu, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Nicholas Mitchell
Meteor Radar Vertical Wind Observation Biases And Mathematical Debiasing Strategies Including The 3dvar+Div Algorithm, Alan Z. Liu, Zishun Qiao, Gunter Stober, Alexander Kozlovsky, Ales Kuchar, Christoph Jacobi, Chris Meek, Diego Janches, Guiping Liu, Masaki Tsutsumi, Njål Gulbrandsen, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Nicholas Mitchell
Publications
Meteor radars have become widely used instruments to study atmospheric dynamics, particularly in the 70 to 110 km altitude region. These systems have been proven to provide reliable and continuous measurements of horizontal winds in the mesosphere and lower thermosphere. Recently, there have been many attempts to utilize specular and/or transverse scatter meteor measurements to estimate vertical winds and vertical wind variability. In this study we investigate potential biases in vertical wind estimation that are intrinsic to the meteor radar observation geometry and scattering mechanism, and we introduce a mathematical debiasing process to mitigate them. This process makes use of …
Dynamics Of Atmospheric Gravity Wave Breaking In The Mesopause Region, Fan Yang
Dynamics Of Atmospheric Gravity Wave Breaking In The Mesopause Region, Fan Yang
Doctoral Dissertations and Master's Theses
GWs significantly impact the Mesosphere and Lower Thermosphere (MLT), and as a consequence of GW breaking, atmospheric turbulence plays an essential role in the mixing and transport of momentum, mass, and chemical materials in MLT. The main focus of this research for the fulfillment of the proposed Ph.D. dissertation is to improve the understanding of the dynamic process of wave breaking and their effects in the mesopause region above Andes Lidar Observatory (30.2◦ S, 70.7◦ W). A few scientific topics related to GW break- ing are addressed. What are the probabilities of the atmosphere becoming convectively or dynamically unstable in …
Kinetic Modeling Of Ionospheric Outflows Observed By The Visions-1 Sounding Rocket, Robert M. Albarran Ii
Kinetic Modeling Of Ionospheric Outflows Observed By The Visions-1 Sounding Rocket, Robert M. Albarran Ii
Doctoral Dissertations and Master's Theses
Plasma escape from the high-latitude ionosphere (ion outflow) serves as a significant source of heavy plasma to magnetospheric plasma sheet and ring current regions. Outflows alter mass density and reconnection rates, hence global responses of the magnetosphere. The VISIONS-1 (VISualizing Ion Outflow via Neutral atom imaging during a Substorm) sounding rocket was launched on Feb. 7, 2013 at 8:21 UTC from Poker Flat, Alaska, into an auroral substorm with the objective of identifying the drivers and dynamics of nightside ion outflow at altitudes where it is initiated, below 1000 km. Energetic ion data from the VISIONS-1 polar cap boundary crossing …
Ionospheric Feedback And Ulf Quarter-Waves, Anatoly Streltsov, Evgeny V. Mishin
Ionospheric Feedback And Ulf Quarter-Waves, Anatoly Streltsov, Evgeny V. Mishin
Publications
This paper presents results from the numerical investigation of nonlinear feedback interactions between ULF field-aligned currents (FACs) and the ionospheric plasma in the global magnetospheric resonator with a non-symmetrical distribution of the plasma density in the conjugate hemispheres. The density asymmetry is enhanced by the introduction of the ionospheric valley in the hemisphere where the plasma density is already lower. The main result from this study is that in the non-symmetrical resonator, the ionospheric feedback mechanism, driven by the electric field with the maximum amplitude of 50 mV/m, develops nonlinear, intense, small-scale upward currents with a characteristic quarter-wavelength structure along …
Stability Characteristics Of The Mesopause Region Above The Andes, Fan Yang, Alan Z. Liu
Stability Characteristics Of The Mesopause Region Above The Andes, Fan Yang, Alan Z. Liu
Publications
We report a detailed analysis of atmospheric stabilities in the mesopause region (85–100 km) based on over 2,000 hr of high-resolution temperature and horizontal wind measurements made with a Na lidar at the Andes Lidar Observatory, located in Cerro Pachón, Chile (30.25°S, 70.74°W). The square of Brunt–Väisälä frequency and the Richardson number are calculated, and occurrence probabilities of convective and dynamic instabilities are derived. An approach to assess the biases due to measurement uncertainties is used to obtain more accurate occurrence probabilities. The overall occurrence probabilities of convective and dynamic instabilities are 2.7% and 6.7%, respectively. High-, medium-, and low- …
Modeling Studies Of Gravity Wave Dynamics In Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, And Induced Flow Responses, Wenjun Dong, David C. Fritts, Michael P. Hickey, Alan Z. Liu, Thomas S. Lund, Shaodong Zhang, Yanying Yan, Fan Yang
Modeling Studies Of Gravity Wave Dynamics In Highly Structured Environments: Reflection, Trapping, Instability, Momentum Transport, Secondary Gravity Waves, And Induced Flow Responses, Wenjun Dong, David C. Fritts, Michael P. Hickey, Alan Z. Liu, Thomas S. Lund, Shaodong Zhang, Yanying Yan, Fan Yang
Publications
A compressible numerical model is applied for three-dimensional (3-D) gravity wave (GW) packets undergoing momentum deposition, self-acceleration (SA), breaking, and secondary GW (SGW) generation in the presence of highly-structured environments enabling thermal and/or Doppler ducts, such as a mesospheric inversion layer (MIL), tidal wind (TW), or combination of MIL and TW. Simulations reveal that ducts can strongly modulate GW dynamics. Responses modeled here include reflection, trapping, suppressed transmission, strong local instabilities, reduced SGW generations, higher altitude SGW responses, and induced large-scale flows. Instabilities that arise in ducts experience strong dissipation after they emerge, while trapped smaller-amplitude and smaller-scale GWs can …
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 …
Design And Development Of Distributed Lower Atmospheric Instrumentation Packages, Julio Guardado
Design And Development Of Distributed Lower Atmospheric Instrumentation Packages, Julio Guardado
Doctoral Dissertations and Master's Theses
The recent miniaturization of embedded electronics and widespread availability of low-cost sensors, microcontrollers and transceivers has enabled development of sensor suites that can be used for high temporal and spatial resolution measurements of atmospheric parameters such as temperature, pressure, humidity, particulate counts, wind velocity and much more. This thesis presents the development of both airborne and ground based distributed atmospheric instrumentation suites. First, we present a low-cost radiosonde platform capable of simultaneous multipoint launches or high cadence back-to-back continuous launches. This radiosonde platform can do wind measurements on an approximately 60 m scale up to a minimum of 25 km. …
Oxygen Ion Escape At Venus Associated With Three-Dimensional Kelvin-Helmholtz Instability, Tong Dang, Xuanye Ma, Jiuhou Le, Binzheng Zhang, Tielong Zhang, Zhonghua Yao, John Lyon, Sudong Xiao, Maodong Yan, Oliver Brambles, Kareem Sorathia
Oxygen Ion Escape At Venus Associated With Three-Dimensional Kelvin-Helmholtz Instability, Tong Dang, Xuanye Ma, Jiuhou Le, Binzheng Zhang, Tielong Zhang, Zhonghua Yao, John Lyon, Sudong Xiao, Maodong Yan, Oliver Brambles, Kareem Sorathia
Publications
How oxygens escape from Venus has long been a fundamental but controversial topic in the planetary research. Among various key mechanisms, the Kelvin-Helmholtz instability (KHI) has been suggested to play an important role in the oxygen ion escape from Venus. Limited by either scarce in-situ observations or simplified theoretical estimations, the mystery of oxygen ion escape process associated with KHI is still unsettled. Here we present the first three-dimensional configuration of KHI at Venus with a global multifluid magnetohydrodynamics model, showing a significantly fine structure and evolution of the KHI. KHI mainly occurred at the low latitude boundary layer if …
3d Numerical Simulation Of Secondary Wave Generation From Mountain Wave Breaking Over Europe, Christopher J. Heale, Katrina Bossert, Sharon L. Vadas
3d Numerical Simulation Of Secondary Wave Generation From Mountain Wave Breaking Over Europe, Christopher J. Heale, Katrina Bossert, Sharon L. Vadas
Publications
In this paper, we simulate an observed mountain wave event over central Europe and investigate the subsequent generation, propagation, phase speeds and spatial scales, and momentum deposition of secondary waves under three different tidal wind conditions. We find the mountain wave breaks just below the lowest critical level in the mesosphere. As the mountain wave breaks, it extends outwards along the phases and fluid associated with the breaking flows downstream of its original location by 500–1,000 km. The breaking generates a broad range of secondary waves with horizontal scales ranging from the mountain wave instability scales (20–300 km), to multiples …
Feedback Interactions Between The Ionosphere And Magnetosphere At Middle Latitude, Mergen Alimaganbetov, Anatoly Streltsov
Feedback Interactions Between The Ionosphere And Magnetosphere At Middle Latitude, Mergen Alimaganbetov, Anatoly Streltsov
Publications
Observations show that magnetic pulsations with frequencies around 1 mHz are frequently detected simultaneously at different latitudes on the ground, in the inner magnetosphere, and in the solar wind. The coupling between oscillations in the dynamic pressure or magnetic field carried by the solar wind and the ULF waves detected on the ground at high latitudes has been suggested in several studies. We present results from a numerical study of ultra-low-frequency waves detected by the ground magnetometers at middle latitudes during substorm. We investigate the hypothesis that these waves are generated by the ionospheric feedback instability driven by the large-scale …
Comparison Of Mlt Momentum Fluxes Over The Andes At Four Different Latitudinal Sectors Using Multistatic Radar Configurations, J. Federico Conte, Alan Liu, Zishun Qiao, Jorge L. Chau, David C. Fritts, José L. Hormaechea, Jacobo O. Salvador, Marco A. Milla
Comparison Of Mlt Momentum Fluxes Over The Andes At Four Different Latitudinal Sectors Using Multistatic Radar Configurations, J. Federico Conte, Alan Liu, Zishun Qiao, Jorge L. Chau, David C. Fritts, José L. Hormaechea, Jacobo O. Salvador, Marco A. Milla
Publications
The middle atmosphere over South America, particularly above the Andes mountain range, is known as one of the most dynamically active regions in the world. Previous studies have investigated wave dynamics at mesosphere and lower thermosphere (MLT) altitudes within this region, but only a handful of them have made use of continuous measurements provided by specular meteor radars (SMRs). Furthermore, it was only until recently that MLT horizontal wind gradients were estimated for the first time using Spread Spectrum Interferometric Multistatic meteor radar Observing Network (SIMONe) Argentina, a multistatic SMR network located in southern Patagonia. By observing larger amounts of …
Resonant Alfvén Waves In The Lower Auroral Ionosphere: Evidence For The Nonlinear Evolution Of The Ionospheric Feedback Instability, Hassanali Akbari, Anatoly Streltsov, Robert Pfaff, James Clemmons, Henry Freudenreich, Douglas Rowland
Resonant Alfvén Waves In The Lower Auroral Ionosphere: Evidence For The Nonlinear Evolution Of The Ionospheric Feedback Instability, Hassanali Akbari, Anatoly Streltsov, Robert Pfaff, James Clemmons, Henry Freudenreich, Douglas Rowland
Publications
During the “Auroral Jets” experiment from Poker Flat, Alaska on 2 March 2017, two NASA sounding rockets were simultaneously launched into the active auroral ionosphere. The rockets were equipped with instrumentation to measure DC and AC electric fields, magnetic fields, energetic electrons, plasma density, and neutral winds and achieved apogees of 190 and 330 km. A prominent feature of the electric and magnetic field observations is the presence of localized large-amplitude (±40 mV/m and ±100 nT) small-scale (λ⊥∼ 1 km) Alfvén wave structures at altitudes as low as 150 km in the vicinity of up- and down-ward current regions. We …
The Source Of Auroral Omegas, Heidi K. Nykyri, J.M. Weygand, Mostafa El-Alaoui
The Source Of Auroral Omegas, Heidi K. Nykyri, J.M. Weygand, Mostafa El-Alaoui
Publications
The auroral wave-like structures called “omega bands” appear within the post-midnight sector auroral oval with shapes resembling the Greek letter omega, and are typically associated with the recovery phase of substorms. Prior work and MHD simulations suggest both high speed earthward flows and postmidnight flow shears are possible omega band source mechanisms. However, what produces omega bands is not well understood. It is most likely that the paucity of concurrent magnetospheric data has limited our ability to understand fully the mechanism responsible for the generation of the omega bands. We have identified about 263 auroral omegas in seven different THEMIS …
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; …
Acoustic/Gravity Wave Phenomena In Wide-Field Imaging: From Data Analysis To A Modeling Framework For Observability In The Mlt Region And Beyond, Jaime Aguilar Guerrero
Acoustic/Gravity Wave Phenomena In Wide-Field Imaging: From Data Analysis To A Modeling Framework For Observability In The Mlt Region And Beyond, Jaime Aguilar Guerrero
Doctoral Dissertations and Master's Theses
Acoustic waves, gravity waves, and larger-scale tidal and planetary waves are significant drivers of the atmosphere’s dynamics and of the local and global circulation that have direct and indirect impacts on our weather and climate. Their measurements and characterization are fundamental challenges in Aeronomy that require a wide range of instrumentation with distinct operational principles. Most measurements share the common features of integrating optical emissions or effects on radio waves through deep layers of the atmosphere. The geometry of these integrations create line-of-sight effects that must be understood, described, and accounted for to properly present the measured data in traditional …
A Quasi-27-Day Oscillation Activity From The Troposphere To The Mesosphere And Lower Thermosphere At Low Latitudes, Hao Cheng, Alan Z. Liu, Kaiming Huang, Shaodong Zhang, Chunming Huang, Yun Gong
A Quasi-27-Day Oscillation Activity From The Troposphere To The Mesosphere And Lower Thermosphere At Low Latitudes, Hao Cheng, Alan Z. Liu, Kaiming Huang, Shaodong Zhang, Chunming Huang, Yun Gong
Publications
Using meteor radar, radiosonde observations and MERRA-2 reanalysis data from 12 August to 31 October 2006, we report a dynamical coupling from the tropical lower atmosphere to the mesosphere and lower thermosphere through a quasi-27-day intraseasonal oscillation (ISO). It is interesting that the quasi-27-day ISO is observed in the troposphere, stratopause and mesopause regions, exhibiting a three-layer structure. In the MLT, the amplitude in the zonal wind increases from about 4 ms−1 at 90 km to 15 ms−1 at 100 km, which is diferent from previous observations that ISOs occurs generally in winter with an amplitude peak at about 80–90 …
Atmospheric Tomography Using The Nordic Meteor Radar Cluster And Chilean Observation Network De Meteor Radars: Network Details And 3d-Var Retrieval, Gunter Stober, Alan Z. Liu, Zishun Qiao, Alexander Kozlovsky, Masaki Tsutsumi, Chris Hall, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Patrick J. Espy, Robert E. Hibbins, Nicholas Mitchell
Atmospheric Tomography Using The Nordic Meteor Radar Cluster And Chilean Observation Network De Meteor Radars: Network Details And 3d-Var Retrieval, Gunter Stober, Alan Z. Liu, Zishun Qiao, Alexander Kozlovsky, Masaki Tsutsumi, Chris Hall, Satonori Nozawa, Mark Lester, Evgenia Belova, Johan Kero, Patrick J. Espy, Robert E. Hibbins, Nicholas Mitchell
Publications
Ground-based remote sensing of atmospheric parameters is often limited to single station observations by vertical profiles at a certain geographic location. This is a limiting factor for investigating gravity wave dynamics as the spatial information is often missing, e.g., horizontal wavelength, propagation direction or intrinsic frequency. In this study, we present a new retrieval algorithm for multistatic meteor radar networks to obtain tomographic 3-D wind fields within a pre-defined domain area. The algorithm is part of the Agile Software for Gravity wAve Regional Dynamics (ASGARD) and called 3D-Var, and based on the optimal estimation technique and Bayesian statistics. The performance …
Observations And Validation Of Plasma Density, Temperature, And O+ Abundance From A Langmuir Probe Onboard The International Space Station, Shantanab Debchoudhury, Aroh Barjatya, Joseph I. Minow, Victoria N. Coffey, Michael O. Chandler
Observations And Validation Of Plasma Density, Temperature, And O+ Abundance From A Langmuir Probe Onboard The International Space Station, Shantanab Debchoudhury, Aroh Barjatya, Joseph I. Minow, Victoria N. Coffey, Michael O. Chandler
Publications
The Floating Potential Measurement Unit (FPMU) has been operational on board the International Space Station (ISS) since 2006. One of the instruments in the FPMU suite is a spherical wide-sweeping Langmuir probe, referred to as the WLP, which is sampled at a temporal cadence of 1 s giving in-situ measurements of the plasma density and electron temperature. In this study we present our refinements to the Langmuir probe analysis algorithm that address the uncertainties associated with photoelectron emission current from the metal probe. We also derive the fraction of O+ ions as a secondary data product, which shows decrease …