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Showing papers by "Michael P. Hickey published in 2002"


Journal ArticleDOI
TL;DR: The nonisothermal Richardson number becomes negative as early as 0930 UT, indicating conditions conducive to the development of convective instability and turbulence as mentioned in this paper, and the possibility that turbulence could exist at times earlier than previously thought explains the large temperature increase observed before 1000 UT.
Abstract: [1] 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-Vaisala frequency, have been reexamined to include temperature gradients in the calculation of the Richardson number. In the previous analysis using the isothermal Brunt-Vaisala 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 Richardson number becomes negative as early as 0930 UT, indicating conditions conducive to the development of convective instability and turbulence. The possibility that turbulence could exist at times earlier than previously thought explains more satisfactorily the large temperature increase observed before 1000 UT.

21 citations


Journal ArticleDOI
TL;DR: In this paper, the Einaudi and Hines [1970] WKB approximation for the acoustic-gravity wave dispersion relation was used to calculate the wave's intrinsic properties.
Abstract: [1] 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 reported using an imager viewing the OH Meinel bands, while the wave period is among the shortest. Simultaneous Na lidar wind and temperature data from 80 to nearly 110 km altitude allow the intrinsic properties of the wave to be calculated. The Einaudi and Hines [1970] WKB approximation for the acoustic-gravity wave dispersion relation was used to calculate the wave's intrinsic properties. Using this approach indicates that the observed disturbance was an external acoustic wave in the 90 to 107 km altitude region and an external gravity wave at other altitudes between 80 and 90 km. Using model atmospheric data for altitudes below and above this altitude regime indicates that the wave is essentially external everywhere except perhaps in narrow regions around 80 and 105–110 km. This is confirmed using a more exact full-wave model analysis. The observations and model results suggest that this wave was not generated in the troposphere and propagated up to the mesosphere, but rather near 100 km altitude where it was possibly generated by a Leonids meteor.

14 citations


Journal ArticleDOI
TL;DR: In this article, the authors compare ground-based and space-based perspectives of wave perturbation of the O2 Atmospheric (0-1) mesospheric airglow using a theoretical model.

7 citations


Journal ArticleDOI
TL;DR: In this article, gravity wave parameters derived from the ALOHA-93 campaign were used 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.
Abstract: [1] 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. The effect of this is to mitigate the effects of destructive interference in the airglow making the wave more observable from space. For this particular wave the amplitude is derived by normalizing the model-derived airglow fluctuation amplitude to that observed from the ground during the ALOHA-93 campaign. The model then provides momentum and energy fluxes as a function of height as well as the flux divergences, from which the mean state forcing is evaluated. The results suggest that the observed wave could provide significant mean state forcing. Therefore, we conclude that some waves experiencing critical level interactions in the airglow regions are not only likely to be important to the momentum balance of the upper mesosphere/lower thermosphere region but also are more likely to be observed from space.

7 citations