On the Interpretation of Gravity Wave Measurements by Ground-Based Lidars

Dörnbrack, Andreas; Gisinger, Sonja; Kaifler, Bernd

doi:10.3390/atmos8030049

Cited by 25 publications

(34 citation statements)

References 47 publications

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“…We now check our assumption that upward (downward) phase progression corresponds to downward (upward) propagating secondary GWs. If an upward propagating GW is propagating against the background wind with U H <0 and | U H |> c I H (e.g., the GW propagates against the background wind but is swept downstream in the same direction as the wind), then its phase lines are upward (not downward) in time in a z − t plot (Dörnbrack et al, ; Fritts & Alexander, ). The opposite is true for a downward propagating GW.…”

Section: Secondary Gws Within Fishbone Structures In Mcmurdo Lidar Datamentioning

confidence: 99%

The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation

et al. 2018

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We examine the characteristics of secondary gravity waves (GWs) excited by a localized (in space) and intermittent (in time) body force in the atmosphere. This force is a horizontal acceleration of the background flow created when primary GWs dissipate and deposit their momentum on spatial and temporal scales of the wave packet. A broad spectrum of secondary GWs is excited with horizontal scales much larger than that of the primary GW. The polarization relations cause the temperature spectrum of the secondary GWs generally to peak at larger intrinsic periods τIr and horizontal wavelengths λH than the vertical velocity spectrum. We find that the one‐dimensional spectra (with regard to frequency or wave number) follow lognormal distributions. We show that secondary GWs can be identified by a horizontally displaced observer as “fishbone” or “>” structures in z − t plots whereby the positive and negative GW phase lines meet at the “knee,” zknee, which is the altitude of the force center. We present two wintertime cases of lidar temperature measurements at McMurdo, Antarctica (166.69°E, 77.84°S) whereby fishbone structures are seen with zknee=43 and 52 km. We determine the GW parameters and density‐weighted amplitudes for each. We show that these parameters are similar below and above zknee. We verify that the GWs with upward (downward) phase progression are downward (upward) propagating via use of model background winds. We conclude that these GWs are likely secondary GWs having ground‐based periods τr=6–10 hr and vertical wavelengths λz=6–14 km, and that they likely propagate primarily southward.

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Section: Secondary Gws Within Fishbone Structures In Mcmurdo Lidar Datamentioning

confidence: 99%

The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation

et al. 2018

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“…Not only do wind measurements provide additional information about atmospheric stability, together with temperature observations they also offer more sophisticated studies of gravity waves (e.g., Eckermann et al, 1995;Zink and Vincent, 2001;Placke et al, 2013;Bossert et al, 2014;Baumgarten et al, 2015) than studying gravity waves solely from temperature measurements (e.g., Chanin and Hauchecorne, 1981;Whiteway and Carswell, 1995;Alexander et al, 2011). In a recent study, Dörnbrack et al (2017) point out that information about background wind is essential to correctly interpret ground-based gravity wave observations, specifically regarding identified phase lines and the vertical propagation direction. However, simultaneous wind and temperature measurements covering a wider altitude range of the middle atmosphere are rare (e.g., Goldberg et al, Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Section: Introductionmentioning

confidence: 99%

Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

et al. 2017

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Abstract. We present an extensive data set of simultaneous temperature and wind measurements in the Arctic middle atmosphere. It consists of more than 300 h of Doppler Rayleigh lidar observations obtained during three January seasons (2012, 2014, and 2015) and covers the altitude range from 30 km up to about 85 km. The data set reveals large yearto-year variations in monthly mean temperatures and winds, which in 2012 are affected by a sudden stratospheric warming. The temporal evolution of winds and temperatures after that warming are studied over a period of 2 weeks, showing an elevated stratopause and the reformation of the polar vortex. The monthly mean temperatures and winds are compared to data extracted from the Integrated Forecast System of the European Centre for Medium-Range Weather Forecasts (ECMWF) and the Horizontal Wind Model (HWM07). Lidar and ECMWF data show good agreement of mean zonal and meridional winds below ≈ 55 km altitude, but we also find mean temperature, zonal wind, and meridional wind differences of up to 20 K, 20 m s −1 , and 5 m s −1 , respectively. Differences between lidar observations and HWM07 data are up to 30 m s −1 . From the fluctuations of temperatures and winds within single nights we extract the potential and kinetic gravity wave energy density (GWED) per unit mass. It shows that the kinetic GWED is typically 5 to 10 times larger than the potential GWED, the total GWED increases with altitude with a scale height of ≈ 16 km. Since temporal fluctuations of winds and temperatures are underestimated in ECMWF, the total GWED is underestimated as well by a factor of 3-10 above 50 km altitude. Similarly, we estimate the energy density per unit mass for largescale waves (LWED) from the fluctuations of nightly mean temperatures and winds. The total LWED is roughly constant with altitude. The ratio of kinetic to potential LWED varies with altitude over 2 orders of magnitude. LWEDs from ECMWF data show results similar to the lidar data. From the comparison of GWED and LWED, it follows that largescale waves carry about 2 to 5 times more energy than gravity waves.

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“…For upward-propagating waves, c z < 0, and for downward-propagating waves, c z > 0. According to Dörnbrack et al (2017) this condition holds for u 0 > −c I . Otherwise waves appear to be propagating upward in lidar data, while they are in reality propagating downward and vice versa.…”

Section: Vertical Wavelengthmentioning

confidence: 98%

“…Wavelet analysis is a well-established method in atmospheric science in general but also with respect to the study of atmospheric GWs. It is applied to in situ, remote-sensing and satellite observations, and reanalysis data, with the goal of characterizing GW parameters, deriving global maps, or studying generation processes in the troposphere or stratosphere and turbulence generation by breaking GWs (Stockwell et al, 1996;Alexander and Barnet, 2007;Zhang et al, 2001;Dörnbrack et al, 2018;Koch et al, 2005). The key advantage is the preserved temporal resolution, allowing for the detection of spatially and temporally localized wave packets.…”

Section: Introductionmentioning

confidence: 99%

Retrieval of intrinsic mesospheric gravity wave parameters using lidar and airglow temperature and meteor radar wind data

Reichert

Kaifler

et al. 2019

Atmos. Meas. Tech.

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Abstract. We analyse gravity waves in the upper-mesosphere, lower-thermosphere region from high-resolution temperature variations measured by the Rayleigh lidar and OH temperature mapper. From this combination of instruments, aided by meteor radar wind data, the full set of ground-relative and intrinsic gravity wave parameters are derived by means of the novel WAPITI (Wavelet Analysis and Phase line IdenTIfication) method. This WAPITI tool decomposes the gravity wave field into its spectral component while preserving the temporal resolution, allowing us to identify and study the evolution of gravity wave packets in the varying backgrounds. We describe WAPITI and demonstrate its capabilities for the large-amplitude gravity wave event on 16–17 December 2015 observed at Sodankylä, Finland, during the GW-LCYCLE-II (Gravity Wave Life Cycle Experiment) field campaign. We present horizontal and vertical wavelengths, phase velocities, propagation directions and intrinsic periods including uncertainties. The results are discussed for three main spectral regions, representing small-, medium- and large-period gravity waves. We observe a complex superposition of gravity waves at different scales, partly generated by gravity wave breaking, evolving in accordance with a vertically and presumably also horizontally sheared wind.

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On the Interpretation of Gravity Wave Measurements by Ground-Based Lidars

Cited by 25 publications

References 47 publications

The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation

The Excitation of Secondary Gravity Waves From Local Body Forces: Theory and Observation

Winds and temperatures of the Arctic middle atmosphere during January measured by Doppler lidar

Retrieval of intrinsic mesospheric gravity wave parameters using lidar and airglow temperature and meteor radar wind data

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