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Embry-Riddle Aeronautical University

Physical Sciences - Daytona Beach

2005

Articles 1 - 8 of 8

Full-Text Articles in Physical Sciences and Mathematics

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 Mar 2005

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 …

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Observational Investigations Of Gravity Wave Momentum Flux With Spectroscopic Imaging, J. Tang, G. R. Swenson, Alan Z. Liu, F. Kamalabadi Mar 2005

Observational Investigations Of Gravity Wave Momentum Flux With Spectroscopic Imaging, J. Tang, G. R. Swenson, Alan Z. Liu, F. Kamalabadi

Physical Sciences - Daytona Beach

We apply a newly developed gravity wave momentum flux estimation method to the mesospheric measurements obtained with colocated airglow imager and meteor radar at Maui, Hawaii (20.7ºN, 156.3ºW), during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaign. The method identifies individual quasi-monochromatic gravity waves with periods between 6 and ~40 min, estimates the intrinsic wave parameters, and calculates the momentum fluxes carried by vertically propagating waves. Data taken on 28 October 2003 are analyzed in detail to reveal the relationship between momentum flux and wave parameters. The January, April, July, and October 2003 data are divided into summer and …

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Climatology Of Short-Period Gravity Waves Observed Over Northern Australia During The Darwin Area Wave Experiment (Dawex) And Their Dominant Source Regions, P. -D. Pautet, M. J. Taylor, Alan Z. Liu, Gary Swenson Feb 2005

Climatology Of Short-Period Gravity Waves Observed Over Northern Australia During The Darwin Area Wave Experiment (Dawex) And Their Dominant Source Regions, P. -D. Pautet, M. J. Taylor, Alan Z. Liu, Gary Swenson

Physical Sciences - Daytona Beach

The Darwin Area Wave Experiment (DAWEX) was designed to investigate the generation and propagation of gravity waves from intense regions of localized convection that occur regularly over northern Australia (in the vicinity of Darwin) during the premonsoon period. This multinational program was conducted during the austral spring 2001 using a range of coordinated optical, radar, and in situ balloon measurements. As part of this program, all-sky image observations of short-period gravity wave events in the near infrared OH nightglow emission (altitude ~87 km) were made from two well-separated sites in northern Australia: Wyndham (15.5ºS, 128.1ºE) and Katherine (14.5ºS, 132.3ºE), over …

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Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson Feb 2005

Characteristics Of Instabilities In The Mesopause Region Over Maui, Hawaii, Feng Li, Alan Z. Liu, Gary R. Swenson

Physical Sciences - Daytona Beach

Characteristics of convective and dynamical instabilities in the mesopause region (between 85 and 100 km) over Maui, Hawaii (20.7ºN, 156.3ºW) are investigated using 19 nights, ~133 hours of high-resolution wind and temperature data obtained by the University of Illinois Na wind/temperature lidar during the Maui Mesosphere and Lower Thermosphere (Maui MALT) campaigns. The mean probabilities of convective and dynamical instabilities are observed to be ~3 and 10%, respectively, but there is considerable night-to-night variation. At any given time the probability that an unstable condition is found at some altitudes in the 85–100 km range is 90%. The Maui MALT data …

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Comparison Of Meteor Radar And Na Doppler Lidar Measurements Of Winds In The Mesopause Region Above Maui, Hawaii, S. J. Franke, X. Chu, A. Z. Liu, W. K. Hocking Jan 2005

Comparison Of Meteor Radar And Na Doppler Lidar Measurements Of Winds In The Mesopause Region Above Maui, Hawaii, S. J. Franke, X. Chu, A. Z. Liu, W. K. Hocking

Physical Sciences - Daytona Beach

The coincident measurements span 96 hours and altitudes between 80 and 100 km. Statistical comparisons are carried out on radar/lidar winds with 1 hour and 4 km time and height resolution, respectively. The RMS radar/lidar wind component differences observed in this study are in the range 12–17 m/s at altitudes below 96 km. This is smaller than the RMS differences observed in a previous Na lidar and meteor radar comparison. Lidar wind component variances exceed radar variances, and radar/lidar covariance, is nearly equal to the radar variance. Excess variance observed by the lidar is consistent with the fact that the …

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Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner Jan 2005

Vertical Heat And Constituent Transport In The Mesopause Region By Dissipating Gravity Waves At Maui, Hawaii (20.7ºn), And Starfire Optical Range, New Mexico (35ºn), Alan Z. Liu, Chester S. Gardner

Physical Sciences - Daytona Beach

Vertical heat flux profiles induced by dissipating gravity waves in the mesopause region (85–100 km altitude) are derived from Na lidar measurements of winds and temperatures at Maui (20.7ºN, 156.3ºW), Hawaii, and compared with earlier results from Starfire Optical Range (SOR, 35.0ºN, 106.5ºW), New Mexico. The heat flux profile at SOR has a single downward maximum of 2.25 ± 0.3 K m/s at 88 km, while the profile at Maui has two downward maxima of 1.25 ± 0.5 K m/s and 1.40 ± 0.5 K m/s at 87 and 95 km, respectively. The common maximum below 90 km can be …

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Maui Mesosphere And Lower Thermosphere (Maui Malt) Observations Of The Evolution Of Kelvin-Helmholtz Billows Formed Near 86 Km Altitude, J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. J. Rudy Jan 2005

Maui Mesosphere And Lower Thermosphere (Maui Malt) Observations Of The Evolution Of Kelvin-Helmholtz Billows Formed Near 86 Km Altitude, J. H. Hecht, Alan Z. Liu, R. L. Walterscheid, R. J. Rudy

Physical Sciences - Daytona Beach

Small-scale (less than 15 km horizontal wavelength) structures known as ripples have been seen in OH airglow images for nearly 30 years. The structures have been attributed to either convective or dynamical instabilities; the latter are mainly due to large wind shears, while the former are produced by superadiabatic temperature gradients. Dynamical instabilities produce Kelvin-Helmholtz (KH) billows, which have been known for many years. However, models and laboratory experiments suggest that these billows often spawn a secondary instability that is convective in nature. While laboratory investigations see evidence of such structures, the evolution of these instabilities in the atmosphere has …

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Estimation Of Gravity Wave Momentum Flux With Spectroscopic Imaging, Jing Tang, Farzad Kamalabadi, Steven J. Franke, Alan Z. Liu, Gary R. Swenson Jan 2005

Estimation Of Gravity Wave Momentum Flux With Spectroscopic Imaging, Jing Tang, Farzad Kamalabadi, Steven J. Franke, Alan Z. Liu, Gary R. Swenson

Physical Sciences - Daytona Beach

Atmospheric gravity waves play a significant role in the dynamics and thermal balance of the upper atmosphere. In this paper, we present a novel technique for automated and robust calculation of momentum flux of high-frequency quasi-monochromatic wave components from spectroscopic imaging and horizontal radar wind measurements. Our approach uses the two-dimensional (2-D) cross periodogram of two consecutive Doppler-shifted time-differenced (TD) images to identify wave components and estimate intrinsic wave parameters. Besides estimating the average perturbation of dominant waves in the whole field of view, this technique applies 2-D short-space Fourier transform to the TD images to identify localized wave events. …

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