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Full-Text Articles in Physical Sciences and Mathematics

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 ...


Further Investigations Of A Mesospheric Inversion Layer Observed In The Aloha-93 Campaign, Tai-Yin Huang, Michael P. Hickey Ph.D., Tai-Fu Tuan Oct 2002

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 ...


One-Gas Models With Height-Dependent Mean Molecular Weight: Effects On Gravity Wave Propagation, R. L. Walterscheid, Michael P. Hickey Ph.D. Dec 2001

One-Gas Models With Height-Dependent Mean Molecular Weight: Effects On Gravity Wave Propagation, R. L. Walterscheid, Michael P. Hickey Ph.D.

Publications

Many models of the thermosphere employ the one-gas approximation where the governing equations apply only to the total gas and the physical properties of the gas that depend on composition (mean molecular weight and specific heats) are height-dependent. It is further assumed that the physical properties of the gas are locally constant; thus motion-induced perturbations are nil. However, motion in a diffusively separated atmosphere perturbs local values of mean molecular weight and specific heats. These motion-induced changes are opposed by mutual diffusion of the constituent gases, which attempts to restore diffusive equilibrium. Assuming that composition is locally constant is equivalent ...


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 ...


Acoustic Wave Heating Of The Thermosphere, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid Oct 2001

Acoustic Wave Heating Of The Thermosphere, Michael P. Hickey Ph.D., G. Schubert, R. L. Walterscheid

Publications

A numerical model is used to study the dissipation in the thermosphere of upward propagating acoustic waves. Whereas dissipating gravity waves can cool the upper atmosphere through the effects of sensible heat flux divergence, it is found that acoustic waves mainly heat the thermosphere by viscous dissipation. Though the amplitudes of acoustic waves in the atmosphere are poorly constrained, the calculations suggest that dissipating acoustic waves can locally heat the thermosphere at rates of tens of kelvins per day and thereby contribute to the thermospheric energy balance. It is shown that viscous heating cannot be calculated from the divergence of ...


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 ...


Climatology And Modeling Of Quasi-Monochromatic Atmospheric Gravity Waves Observed Over Urbana Illinois, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., S. J. Franke Mar 2001

Climatology And Modeling Of Quasi-Monochromatic Atmospheric Gravity Waves Observed Over Urbana Illinois, J. H. Hecht, R. L. Walterscheid, Michael P. Hickey Ph.D., S. J. Franke

Publications

From analyzing nine months of airglow imaging observations of atmospheric gravity waves (AGWs) over Adelaide, Australia (35°S) [Walterscheid et al., 1999] have proposed that many of the quasi-monochromatic waves seen in the images were primarily thermally ducted. Here are presented 15 months of observations, from February 1996 to May 1997, for AGW frequency and propagation direction from a northern latitude site, Urbana Illinois (40°N). As Adelaide, Urbana is geographically distant from large orographic features. Similar to what was found in Adelaide, the AGWs seem to originate from a preferred location during the time period around summer solstice. In ...


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 ...


Secular Variations Of Atomic Oxygen In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid, Philip G. Richards Nov 2000

Secular Variations Of Atomic Oxygen In The Mesopause Region Induced By Transient Gravity Wave Packets, Michael P. Hickey Ph.D., R. L. Walterscheid, Philip G. Richards

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 atomic oxygen (O) to a gravity wave packet in the mesopause region. We demonstrate that gravity waves affect the time-averaged distribution of O in the mesosphere and lower thermosphere (MLT) region through the constituent fluxes the waves induce. Our conclusions are based on simulations of two wave packets that violate the non-acceleration conditions through transience and dissipation. The net cycle-averaged effect of the waves is to significantly increase (by as much as 50%) the O ...


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 ...


Numerical Simulations Of Gravity Waves Imaged Over Arecibo During The 10-Day January 1993 Campaign, Michael P. Hickey Ph.D., R. L. Walterscheid, Michael J. Taylor, William Ward, G. Schubert, Qihou Zhou, Francisco Garcia, Michael C. Kelly, G. G. Shepherd Jun 1997

Numerical Simulations Of Gravity Waves Imaged Over Arecibo During The 10-Day January 1993 Campaign, Michael P. Hickey Ph.D., R. L. Walterscheid, Michael J. Taylor, William Ward, G. Schubert, Qihou Zhou, Francisco Garcia, Michael C. Kelly, G. G. Shepherd

Publications

Recently, measurements were made of mesospheric gravity waves in the OI (5577 Å) nightglow observed from Arecibo, Puerto Rico, during January 1993 as part of a special 10-day 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 two waves through the mesopause region and calculated the O(¹S) nightglow response to the waves. Mean winds derived from both UARS wind imaging interferometer (WINDII) and Arecibo incoherent scatter radar observations were employed in the computations as were the ...


A Chemical-Dynamical Model Of Wave-Driven Sodium Fluctuations, Michael P. Hickey Ph.D., John M.C. Plane Oct 1995

A Chemical-Dynamical Model Of Wave-Driven Sodium Fluctuations, Michael P. Hickey Ph.D., John M.C. Plane

Publications

A comprehensive chemical-dynamical model is used to investigate the interaction of gravity waves with twenty minor species involved in the atomic sodium chemistry in the mesopause region. We find that chemistry becomes important on the underside of the sodium layer, primarily below 85 km altitude, where the relative importance of chemistry in wave-driven sodium fluctuations increases with increasing wave period and increasing horizontal wavelength. We also find that for altitudes below 80 km an adequate determination of the effects of chemistry in these fluctuations requires the inclusion of several reactions related to ozone chemistry. However, the atomic Na density is ...


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 ...


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 ...