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Full-Text Articles in Physical Sciences and Mathematics

Numerical And Statistical Evidence For Long-Range Ducted Gravity Wave Propagation Over Halley, Antarctica, J. B. Snively, K. Nielsen, M. P. Hickey, C. J. Heale, M. J. Taylor, T. Moffat-Griffin Sep 2013

Numerical And Statistical Evidence For Long-Range Ducted Gravity Wave Propagation Over Halley, Antarctica, J. B. Snively, K. Nielsen, M. P. Hickey, C. J. Heale, M. J. Taylor, T. Moffat-Griffin

Publications

Abundant short-period, small-scale gravity waves have been identified in the mesosphere and lower thermosphere over Halley, Antarctica, via ground-based airglow image data. Although many are observed as freely propagating at the heights of the airglow layers, new results under modeled conditions reveal that a significant fraction of these waves may be subject to reflections at altitudes above and below.The waves may at times be trapped within broad thermal ducts, spanning from the tropopause or stratopause to the base of the thermosphere (~140 km), which may facilitate long-range propagation (~1000s of km) under favorable wind conditions.


Atmospheric Airglow Fluctuations Due To A Tsunami‐Driven Gravity Wave Disturbance, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid Jun 2010

Atmospheric Airglow Fluctuations Due To A Tsunami‐Driven Gravity Wave Disturbance, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid

Publications

A spectral full‐wave model is used to study the upward propagation of a gravity wave disturbance and its effect on atmospheric nightglow emissions. Gravity waves are generated by a surface displacement that mimics a tsunami having a maximum amplitude of 0.5 m, a characteristic horizontal wavelength of 400 km, and a horizontal phase speed of 200 m/s. The gravity wave disturbance can reach F region altitudes before significant viscous dissipation occurs. The response of the OH Meinel nightglow in the mesopause region (∼87 km altitude) produces relative brightness fluctuations, which are ∼1% of the mean for overhead ...


A Full-Wave Investigation Of The Use Of A ‘‘Cancellation Factor’’ In Gravity Wave–Oh Airglow Interaction Studies, Michael P. Hickey Ph.D., Yonghui Yu Jan 2005

A Full-Wave Investigation Of The Use Of A ‘‘Cancellation Factor’’ In Gravity Wave–Oh Airglow Interaction Studies, Michael P. Hickey Ph.D., Yonghui Yu

Publications

Atmospheric gravity waves (GWs) perturb minor species involved in the chemical reactions of airglow emissions in the upper mesosphere and lower thermosphere. In order to determine gravity wave fluxes and the forcing effects of gravity waves on the mean state (which are proportional to the square of the wave amplitude), it is essential that the amplitude of airglow brightness fluctuation be related to the amplitude of major gas density fluctuation in a deterministic way. This has been achieved through detailed modeling combining gravity wave dynamics described using a full-wave model with the chemistry relevant to the airglow emission of interest ...


A Simulation Study Of Space-Based Observations Of Gravity Waves In The Airglow Using Observed Aloha-93 Wave Parameters, Michael P. Hickey Ph.D., J. S. Brown Dec 2002

A Simulation Study Of Space-Based Observations Of Gravity Waves In The Airglow Using Observed Aloha-93 Wave Parameters, Michael P. Hickey Ph.D., J. S. Brown

Publications

We use gravity wave parameters derived from the ALOHA-93 campaign to model four gravity waves in airglow emissions as observed from the ground to numerically predict whether these waves could have been observed from space. In spite of encountering critical levels, some waves may still be observed in the airglow provided the critical level lies within the airglow emission region. One of the four waves experiences a critical level in the lower region of an airglow layer such that the disturbance to the volume emission rate would be effectively limited to a short distance along a satellite line of sight ...


An Observation Of A Fast External Atmospheric Acoustic-Gravity Wave, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., R. J. Rudy, A. Z. Liu Oct 2002

An Observation Of A Fast External Atmospheric Acoustic-Gravity Wave, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., R. J. Rudy, A. Z. Liu

Publications

In November 1999 a new near-IR airglow imaging system was deployed at the Starfire Optical Range outside of Albuquerque, New Mexico. This system allowed wide angle images of the airglow to be collected, with high signal to noise, every 3 seconds with a one second integration time. At approximately 1000 UT on November 17, 1999, a fast wavelike disturbance was seen propagating through the OH Meinel airglow layer. This wave had an observed period of ≈215 seconds, an observed phase velocity of ≈160 m/s and a horizontal wavelength of ≈35 km. This phase velocity is among the fastest yet ...


Reflection Of A Long-Period Gravity Wave Observed In The Nightglow Over Arecibo On May 8–9, 1989?, Michael P. Hickey Ph.D. Nov 2001

Reflection Of A Long-Period Gravity Wave Observed In The Nightglow Over Arecibo On May 8–9, 1989?, Michael P. Hickey Ph.D.

Publications

During the Arecibo Initiative for Dynamics of the Atmosphere (AIDA) campaign in 1989 a characteristic of gravity wave perturbations observed in mesopause region airglow emissions was that airglow brightness fluctuations and airglow-derived temperature fluctuations often occurred either in phase or in antiphase. This stimulated the development of a theory suggesting that such in-phase fluctuations were most probably the result of strong reflections occurring in the mesosphere and lower thermosphere region. Recent examination of a particular wave event and application of simple WKB-type theory has appeared to support this hypothesis. Here we use a full-wave model and a WKB-type model, each ...


Airglow Variations Associated With Nonideal Ducting Of Gravity Waves In The Lower Thermosphere Region, Michael P. Hickey Ph.D. Aug 2001

Airglow Variations Associated With Nonideal Ducting Of Gravity Waves In The Lower Thermosphere Region, Michael P. Hickey Ph.D.

Publications

A numerical full-wave model is used to study the response of the O2 atmospheric airglow to ducted gravity waves in the mesopause region. For an isothermal, quasi-adiabatic, and motionless background atmosphere the calculated phase differences between airglow brightness fluctuations and fluctuations of temperatures derived from the airglow, as given by Krassovsky's ratio, are in good agreement with the predictions of published theory. Significant departures from the predictions of the basic theory are obtained when we consider ducting in the presence of the eddy and molecular diffusion of heat and momentum in a nonisothermal background atmosphere. Wind shears also affect ...


Gravity Wave Propagation Directions Inferred From Satellite Observations Including Smearing Effects, Jason S. Brown, Michael P. Hickey Ph.D. Mar 2001

Gravity Wave Propagation Directions Inferred From Satellite Observations Including Smearing Effects, Jason S. Brown, Michael P. Hickey Ph.D.

Publications

We simulate space-based, sublimb viewing observations of airglow brightness fluctuations caused by atmospheric gravity wave interactions with the O2 atmospheric airglow, and we demonstrate that because of the geometry associated with such observations, the brightness fluctuations observed for the optically thick 0–0 band emission will always appear stronger for waves traveling toward the observer (the satellite). The effect should be most noticeable for waves having relatively small vertical wavelengths (∼10 km) and horizontal wavelengths of 50 km or greater. For waves of short (∼100 km) horizontal wavelength, the brightness fluctuation anisotropy with respect to viewing direction may also be ...


Secular Variations Of Oi 5577 Å Airglow In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid Feb 2001

Secular Variations Of Oi 5577 Å Airglow In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid

Publications

We employ a 2-dimensional, time-dependent, fully nonlinear model of minor species in the mesopause region and our Spectral Full-Wave Model to simulate the response of minor species and the OI 5577 Å airglow to a gravity wave packet in the mesopause region. Gravity waves affect the time-averaged distribution of minor species in the mesosphere and lower thermosphere (MLT) region through constituent fluxes induced by violation of the non-acceleration conditions due to wave transience and dissipation. In addition, wave perturbed chemistry can induce a flux of chemically active species. Simulations are performed with nominal values of eddy diffusion coefficients in the ...


Resolving Ambiguities In Gravity Wave Propagation Directions Inherent In Satellite Observations: A Simulation Study, Michael P. Hickey Ph.D., Jason S. Brown Sep 2000

Resolving Ambiguities In Gravity Wave Propagation Directions Inherent In Satellite Observations: A Simulation Study, Michael P. Hickey Ph.D., Jason S. Brown

Publications

We simulate space-based, sub-limb viewing observations of airglow brightness fluctuations caused by atmospheric gravity wave interactions with the O2 atmospheric airglow, and we demonstrate that, due to the geometry associated with such observations, the brightness fluctuations observed for the optically thick 0–0 band emission will always appear stronger for waves traveling towards the observer (satellite). The effect should be most noticeable for waves having relatively small vertical wavelengths (∼10 km) and horizontal wavelengths of 50 km or greater. For waves of short (∼100 km) horizontal wavelength, the brightness fluctuation anisotropy with respect to viewing direction may also be evident ...


A Note On Gravity Wave-Driven Volume Emission Rate Weighted Temperature Perturbations Inferred From O₂ Atmospheric And O I 5577 Airglow Observations, Michael P. Hickey Ph.D., Richard L. Walterscheid Mar 1999

A Note On Gravity Wave-Driven Volume Emission Rate Weighted Temperature Perturbations Inferred From O₂ Atmospheric And O I 5577 Airglow Observations, Michael P. Hickey Ph.D., Richard L. Walterscheid

Publications

A full-wave dynamical model and chemistry models that simulate ground-based observations of gravity wave-driven O₂ atmospheric and O I 5577 airglow fluctuations in the mesopause region are used to demonstrate that for many observable gravity waves modeling is required to infer temperature perturbation amplitudes from airglow observations. We demonstrate that the amplitude of the altitude-integrated volume emission rate weighted temperature perturbation differs by at least about 30% from the amplitude of the temperature perturbation of the major gas in the vicinity of the peak of the airglow volume emission rate for gravity waves with horizontal phase speeds less than about ...


Full-Wave Modeling Of Small-Scale Gravity Waves Using Airborne Lidar And Observations Of The Hawaiian Airglow (Aloha-93) O(¹S) Images And Coincident Na Wind/Temperature Lidar Measurements, Michael P. Hickey Ph.D., Michael J. Taylor, Chester S. Gardner, Christian R. Gibbons Mar 1998

Full-Wave Modeling Of Small-Scale Gravity Waves Using Airborne Lidar And Observations Of The Hawaiian Airglow (Aloha-93) O(¹S) Images And Coincident Na Wind/Temperature Lidar Measurements, Michael P. Hickey Ph.D., Michael J. Taylor, Chester S. Gardner, Christian R. Gibbons

Publications

Measurements were made of mesospheric gravity waves in the OI (5577 Å) nightglow observed from Maui, Hawaii, during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) campaign. Clear, monochromatic gravity waves were observed on several nights. By using a full-wave model that realistically includes the major physical processes in this region, we have simulated the propagation of four waves through the mesopause region and calculated the O(¹S) nightglow response to the waves. Mean winds derived from Na wind/temperature lidar observations were employed in the computations. Wave amplitudes were calculated based on the requirement that the observed ...


Wave-Modified Mean Exothermic Heating In The Mesopause Region, Michael P. Hickey Ph.D., R. L. Walterscheid Nov 1994

Wave-Modified Mean Exothermic Heating In The Mesopause Region, Michael P. Hickey Ph.D., R. L. Walterscheid

Publications

We employ a model of wave-driven OH nightglow fluctuations to calculate the effects of gravity waves on the chemical exothermic heating due to reactions involving odd hydrogen and odd oxygen species in the mesopause region. Using a model based on time means and deviations from those means, it is demonstrated that gravity waves contribute to the time-average exothermic heating. The effect can be significant because the fractional fluctuations in minor species density can be substantially greater than the fractional fluctuation of the major gas density. Our calculations reveal that the waves mitigate the exothermic heating, demonstrating their potential importance in ...


Comparison Of Theories For Gravity Wave Induced Fluctuations In Airglow Emissions, R. L. Walterscheid, G. Schubert, Michael P. Hickey Ph.D. Mar 1994

Comparison Of Theories For Gravity Wave Induced Fluctuations In Airglow Emissions, R. L. Walterscheid, G. Schubert, Michael P. Hickey Ph.D.

Publications

A comparison is undertaken of theories for the gravity wave induced fluctuations in the intensity of airglow emissions and the associated temperature of the source region. The comparison is made in terms of Krassovsky's ratio ηE for a vertically extended emission region (ηE is the ratio of the vertically integrated normalized intensity perturbation to the vertically integrated normalized intensity-weighted temperature perturbation). It is shown that the formulas for ηE in the works by Tarasick and Hines (1990) and Schubert et al. (1991) are in agreement for the case of an inviscid atmosphere. The calculation of ηE using the theory ...


Gravity Wave-Driven Fluctuations In The O2 Atmospheric (0-1) Nightglow From An Extended, Dissipative Emission Region, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid Aug 1993

Gravity Wave-Driven Fluctuations In The O2 Atmospheric (0-1) Nightglow From An Extended, Dissipative Emission Region, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid

Publications

The wave-driven fluctuations in the O2(0-1) atmospheric nightglow is modeled and the parameter (eta) is calculated using a model that accounts for either three-body recombination of atomic oxygen atoms alone to form the O2(b exp 1 Sigma(g)(+)) state directly, or by the further inclusion of the process that allows the formation of the O2(c exp 1 Sigma(u)(-)) intermediate state. The calculations are performed for a latitude of 18 deg N and for the months of March and June. The general results, which display how (eta) varies with wave period, horizontal wavelength, season, and chemical scheme ...


Seasonal And Latitudinal Variations Of Gravity Wave-Driven Fluctuations In Oh Nightglow, Michael P. Hickey Ph.D., R. L. Walterscheid, G. Schubert Oct 1992

Seasonal And Latitudinal Variations Of Gravity Wave-Driven Fluctuations In Oh Nightglow, Michael P. Hickey Ph.D., R. L. Walterscheid, G. Schubert

Publications

The seasonal and latitudinal variations of the gravity wave-driven fluctuations in the OH nightglow are investigated theoretically using a model that accounts for emission from an extended OH layer and includes the effects of eddy diffusivities in the gravity wave dynamics. The mean (unperturbed) state is obtained from a two-dimensional, nighttime model so that mean-state number densities, temperatures and eddy diffusivities are all self-consistent. Seasonal and latitudinal variations in the background OH nightglow emission and in the propagation and dissipation characteristics of the gravity waves influence how the OH nightglow modulations due to gravity waves depend on season and latitude ...


Gravity Wave-Driven Fluctuations In Oh Nightglow From An Extended, Dissipative Emission Region, G. Schubert, R. L. Walterscheid, Michael P. Hickey Ph.D. Aug 1991

Gravity Wave-Driven Fluctuations In Oh Nightglow From An Extended, Dissipative Emission Region, G. Schubert, R. L. Walterscheid, Michael P. Hickey Ph.D.

Publications

The theory of gravity wave-driven fluctuations in the OH nightglow from an extended source region is generalized to account for effects of eddy kinematic viscosity ν and eddy thermal diffusivity κ. In the nondiffusive case, the amplitudes and phases of vertically integrated normalized intensity 〈δI〉/〈Ī〉 and temperature 〈δTI〉/〈ĪI〉perturbations and vertically integrated Krassovsky's ratio 〈η〉 as functions of period are influenced by the upper limit of vertical integration of the extended source, especially at long periods when vertical wavelengths λᵥ are small. The effects, which include oscillations in 〈δT〉/〈Ī〉 , and 〈η〉, particularly at ...


Effects Of Eddy Viscosity And Thermal Conduction And Coriolis Force In The Dynamics Of Gravity Wave Driven Fluctuations In The Oh Nightglow, Michael P. Hickey Ph.D. May 1988

Effects Of Eddy Viscosity And Thermal Conduction And Coriolis Force In The Dynamics Of Gravity Wave Driven Fluctuations In The Oh Nightglow, Michael P. Hickey Ph.D.

Publications

Recently, Walterscheid et al. (1987) have described a dynamical-chemical model of wave-driven fluctuations in the OH nightglow which incorporated a five-reaction photochemical scheme and the dynamics of linearized acoustic-gravity waves in an isothermal, motionless atmosphere. The intensity oscillation (δI) about the time-averaged intensity (I0) and the temperature oscillation (δT) about the time-averaged temperature (T0) were related by means of the complex ratio η ≡ (δI/I0)/(δT/T0). One of the main conclusions of their work was that the inclusion of dynamical effects is absolutely essential for a valid assessment of η at ...


Wavelength Dependence Of Eddy Dissipation And Coriolis Force In The Dynamics Of Gravity Wave Driven Fluctuations In The Oh Nightglow, Michael P. Hickey Ph.D. May 1988

Wavelength Dependence Of Eddy Dissipation And Coriolis Force In The Dynamics Of Gravity Wave Driven Fluctuations In The Oh Nightglow, Michael P. Hickey Ph.D.

Publications

The theory of Walterscheid et al. (1987) to explain internal gravity wave induced oscillations in the emission intensity I and rotational temperature T of the OH nightglow was modified by Hickey (1988) to include the effects of eddy dissipation and Coriolis force. In the theory of Walterscheid et al. (1987) the ratio η = (δI/I0)/(δT/T0) (δ refers to a perturbation quantity, and a zero subscript refers to an average) was found to be independent of horizontal wavelength at long periods, while in the extended theory of Hickey (1988) some such dependence was inferred. In ...