Evidence of gravity wave breaking in lidar data from the mesopause region (original) (raw)
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Rayleigh-Lidar Observations of Mesospheric Gravity Wave Activity above Logan, Utah
A Rayleigh-scatter lidar operated from Utah State University (41.7°N, 111.8°W) for a period spanning 11 years ― 1993 through 2004. Of the 900 nights observed, data on 150 extended to 90 km or above. They were the ones used in these studies related to atmospheric gravity waves (AGWs) between 45 and 90 km. This is the first study of AGWs with an extensive data set that spans the whole mesosphere. Using the temperature and temperature gradient profiles, we produced a climatology of the Brunt-Väisälä (buoyancy) angular frequency squared, N2 (rad/s)2. The minimum and maximum values of N2 vary between 2.2×10-4 (rad/s)2 and 9.0×10-4 (rad/s)2. The corresponding buoyancy periods vary between 7.0 and 3.5 minutes. While for long averages the atmosphere above Logan, Utah, is convectively stable, all-night and hourly profiles showed periods of convective instability (i.e., negative N2). The N2 values were often significantly different from values derived from the NRL-MSISe00 model atmosphere bec...
Journal of Atmospheric and Solar-Terrestrial Physics, 2017
We present the first statistical study of gravity waves with periods of 0.3-2.5 h that are persistent and dominant in the vertical winds measured with the University of Colorado STAR Na Doppler lidar in Boulder, CO (40.1°N, 105.2°W). The probability density functions of the wave amplitudes in temperature and vertical wind, ratios of these two amplitudes, phase differences between them, and vertical wavelengths are derived directly from the observations. The intrinsic period and horizontal wavelength of each wave are inferred from its vertical wavelength, amplitude ratio, and a designated eddy viscosity by applying the gravity wave polarization and dispersion relations. The amplitude ratios are positively correlated with the ground-based periods with a coefficient of~0.76. The phase differences between the vertical winds and temperatures (φ φ − W T) follow a Gaussian distribution with 84.2 ± 26.7°, which has a much larger standard deviation than that predicted for non-dissipative waves (~3.3°). The deviations of the observed phase differences from their predicted values for non-dissipative waves may indicate wave dissipation. The shorter-vertical-wavelength waves tend to have larger phase difference deviations, implying that the dissipative effects are more significant for shorter waves. The majority of these waves have the vertical wavelengths ranging from 5 to 40 km with a mean and standard deviation of~18.6 and 7.2 km, respectively. For waves with similar periods, multiple peaks in the vertical wavelengths are identified frequently and the ones peaking in the vertical wind are statistically longer than those peaking in the temperature. The horizontal wavelengths range mostly from 50 to 500 km with a mean and median of~180 and 125 km, respectively. Therefore, these waves are mesoscale waves with high-to-medium frequencies. Since they have recently become resolvable in high-resolution general circulation models (GCMs), this statistical study provides an important and timely reference for them.
Geophysical Research Letters, 2007
On the night of December 3rd, 2004 (UT day 338), we observed a significant acceleration of horizontal wind near 100 km between 0900 and 0915 UT accompanied by a temperature cooling at the same altitude and warming below it. The Lomb spectrum analysis of the raw dataset revealed that a gravity wave with 1.5 hr period was significant between 0500 and 0900 UT, but blurred after 0900 UT, suggesting the transfer of wave energy and momentum from wave field to mean flow. Most likely, this observed phenomenon is due to the breaking of an upward propagating gravity wave with an apparent period of $1.5 hr. Using linear saturation theory and assuming a monochromatic wave packet, we estimated the characteristics of breaking gravity wave, eddy diffusion coefficient, and a simple relation between Prandtl number and turbulence localization measure when the wave is breaking, from the experimentally determined heating rate, horizontal wind acceleration, and background temperature and winds.
Journal of Atmospheric and Solar-Terrestrial Physics, 2008
Using the technique developed by Lidar studies of the nighttime sodium layer over Urbana, Illinois, 2. Gravity waves. Journal of Geophysical Research 92, 4673-4693] and a new method proposed by us, two groups of gravity wave parameters are extracted from 11 years sodium lidar measurements made at a southern low-latitude location. The wave occurrence frequencies, wave parameter distributions, and wave parameter relationships are given and compared with other lidar observations. The different lidar derived results can be attributed to different atmospheric parameters. The characteristics of these two groups of gravity waves are also compared, as well as that predicted by diffusive filtering theory, and we find the gravity wave relationships derived from our method are in better agreement with diffusive filtering theory predictions. r
EPJ Web of Conferences, 2016
We present the first coordinated study of a 1-h mesoscale gravity wave event detected simultaneously by a Na Doppler lidar at Boulder, CO (40.1°N, 105.2°W), and a Na Doppler lidar and an airglow temperature mapper (AMTM) at Logan, UT (41.7°N, 111.8°W) in the mesopause region on 27 Nov. 2013. The vertical and horizontal wavelengths are ~16.0±0.3 and 342.0±10.4 km, corresponding to vertical and horizontal phase speeds of ~4.4±0.1 and 95.0±3.0 m/s, respectively. The wave propagates from Logan to Boulder with an azimuth angle of ~138.1±1.7° clockwise from North. A uniqueness of this study is that the 1-h wave amplitudes on vertical winds have been quantified for the first time by the STAR Na lidar at Boulder. The GW polarization relation between vertical wind and temperature is evaluated. The intrinsic period of the wave is Doppler shifted to ~100 min by a background wind of 40 m/s, which is confirmed by USU lidar wind observations. This study illustrates a great potential of combining multiple instruments to fully characterize mesoscale gravity waves and inspect their intrinsic properties. 2. COORDINATED OBSERVATIONS This study was enabled by the simultaneous observations with two Na Doppler lidars of the Consortium of Resonance and Rayleigh Lidars (CRRL) at Boulder, CO [4], and at Logan, UT [5], combining with an Advanced Mesospheric Temperature Mapper (AMTM) [6] located at Bear Lake Observatory (41.9°N, 111.4°W) nearby Logan. The observations were made from ~1-13 UT in the night on 27 November 2013. Under the CRRL umbrella, the Consortium Technology Center (CTC), hosted by the University of Colorado Boulder, operates a STAR Na Doppler lidar from the Table Mountain Lidar Observatory north of Boulder while the Utah State University (USU) lidar group operates a Na Doppler lidar from the USU campus in Logan. Here "STAR" stands for Student Training and Atmospheric Research.
Gravity waves in the middle atmosphere observed by Rayleigh lidar: 1. Case studies
Journal of Geophysical Research, 1991
Density and temperature mesoscale fluctuations as observed in the stratosphere and mesosphere by means of two Rayleigh lidars with high resolution in time (15 min) and space (300 m), have been analyzed in some particular cases corresponding to different seasonal conditions. These case studies are characteristic of recurrently observed patterns and thus provide a description of the mesoscale fluctuation field in the middle atmosphere. The spatial, temporal, and spectral characteristics of the fluctuations are described and discussed in the framework of the gravity wave interpretation. Dominant wave modes with large period and large vertical wavelength (inertia-gravity waves) are frequently observed in the stratosphere and lower mesosphere. These lowfrequency modes are not generally observed above 50-to 55km altitude, suggesting a strong damping of such waves in the mesosphere. The vertical growth of potential energy density indicates that the wave motions are generally not conservative in the middle atmosphere. The gravity waves amplitude appears too small to produce convective instabilities in the stratosphere. On the contrary, the amplitude of the fluctuations is close to the convective saturation limit deduced from the linear theory for wavelengths up to 3-5 km in the lower mesosphere, and up to 6-8 km above 60 km altitude. Furthermore, convectively instable layers, which can persist for periods longer than 1 hour, have been frequently observed in the mesosphere.
Journal of Geophysical Research: Atmospheres, 2015
We present the first coordinated study using two lidars at two separate locations to characterize a 1 h mesoscale gravity wave event in the mesopause region. The simultaneous observations were made with the Student Training and Atmospheric Research (STAR) Na Doppler lidar at Boulder, CO, and the Utah State University Na Doppler lidar and temperature mapper at Logan, UT, on 27 November 2013. The high precision possessed by the STAR lidar enabled these waves to be detected in vertical wind. The mean wave amplitudes are~0.44 m/s in vertical wind and~1% in relative temperature at altitudes of 82-107 km. Those in the zonal and meridional winds are 6.1 and 5.2 m/s averaged from 84 to 99 km. The horizontal and vertical wavelengths inferred from the mapper and lidars are~219 ± 4 and 16.0 ± 0.3 km, respectively. The intrinsic period is~1.3 h for the airglow layer, Doppler shifted by a mean wind of~17 m/s. The wave packet propagates from Logan to Boulder with an azimuth angle of~135°clockwise from north and an elevation angle of~3°from the horizon. The observed phase difference between the two locations can be explained by the traveling time of the 1 h wave from Logan to Boulder, which is about~2.4 h. The wave polarization relations are examined through the simultaneous quantifications of the three wind components and temperature. This study has developed a systematic methodology for fully characterizing mesoscale gravity waves, inspecting their intrinsic properties and validating the derivation of horizontal wave structures by applying multiple instruments from coordinated stations.
Journal of Geophysical Research: Atmospheres, 2014
Mesospheric inversion layers (MIL) are well studied in the literature but their relationship to the dynamic feature associated with the breaking of atmospheric waves in the mesosphere/lower thermosphere (MLT) region are not well understood. Two strong MIL events (ΔT~30 K) were observed above 90 km during a 6 day full diurnal cycle Na lidar campaign conducted from 6 August to 13 August Logan, Utah (42°N, 112°W). Colocated Advanced Mesospheric Temperature Mapper observations provided key information on concurrent gravity wave (GW) events and their characteristics during the nighttime observations. The study found both MILs were well correlated with the development and presence of an unstable region~2 km above the MIL peak altitudes and a highly stable region below, implicating the strengthening of MIL is likely due to the increase of downward heat flux by the enhanced saturation of gravity wave, when it propagates through a highly stable layer. Each MIL event also exhibited distinct features: one showed a downward progression most likely due to tidal-GW interaction, while the peak height of the other event remained constant. During further investigation of atmospheric stability surrounding the MIL structure, lidar measurements indicate a sharp enhancement of the convective stability below the peak altitude of each MIL. We postulate that the sources of these stable layers were different; one was potentially triggered by concurrent large tidal wave activity and the other during the passage of a strong mesospheric bore. YUAN ET AL.