Large‐Amplitude Mountain Waves in the Mesosphere Accompanying Weak Cross‐Mountain Flow During DEEPWAVE Research Flight RF22

Fritts, David C.; Williams, B. P.; Bossert, Katrina; Plane, J. M. C.; Taylor, Michael J.; Pautet, P. D.; Eckermann, Stephen D.; Kruse, Christopher G.; Smith, Ronald B.; Dörnbrack, Andreas; Rapp, Markus; Mixa, Tyler; Murphy, D. J.

doi:10.1029/2017jd028250

Cited by 35 publications

(47 citation statements)

References 103 publications

(212 reference statements)

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“…The FFT for each pass reveals spectral power centered around λ H ~ 220, 120, and 80 km, with the spectral power being most significant on the first and second passes. The λ H are consistent with observations at the flight level of the GV, and stratospheric lidar observations of MWs (Fritts et al, ), suggesting that these observed wavelengths are likely associated with MWs. As expected for MWs, all amplitudes for the λ H ~ 220, 120, and 80 km decay upon approach to the MW critical level near 90 km.…”

Section: Temperature and Mf Measurements And Validationsupporting

confidence: 88%

“…Assuming hydrostatic motions, the MF per unit mass for a given GW can be calculated as (Bossert et al, ; Ern et al, ; Fritts et al, ),

MF = < u_{H}^{'} w^{'} > = < \frac{1}{2} {(\frac{T^{'}}{\overset{T}{true}} \frac{g}{N})}^{2} ((), \frac{k_{H}}{m}) >

where u H ′ and w ′ are the horizontal and vertical wind perturbations of the GW, k H and m are the horizontal and vertical wavenumbers, and braces denote the mean over the observation segment. While k H can be obtained from the FFT and corresponding spectral temperature amplitude calculation, m must be calculated using the dispersion relation (Fritts & Alexander, ),

m^{2} = \frac{N^{2}}{{((), c - U_{H})}^{2}} - \frac{1}{4 H^{2}} - k_{H}^{2}

where c is the Earth‐relative phase speed assumed to be ~0 m/s for the observed presumed MWs and U H is the background wind in the direction of the MW horizontal wavenumber vector.…”

Section: Temperature and Mf Measurements And Validationmentioning

confidence: 99%

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Momentum Flux Spectra of a Mountain Wave Event Over New Zealand

et al. 2018

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During the Deep Propagating Gravity Wave Experiment (DEEPWAVE) 13 July 2014 research flight over the South Island of New Zealand, a multiscale spectrum of mountain waves (MWs) was observed. High‐resolution measurements of sodium densities were available from ~70 to 100 km for the duration of this flight. A comprehensive technique is presented for obtaining temperature perturbations, T′, from sodium mixing ratios over a range of altitudes, and these T′ were used to calculate the momentum flux (MF) spectra with respect to horizontal wavelengths, λH, for each flight segment. Spectral analysis revealed MWs with spectral power centered at λH of ~80, 120, and 220 km. The temperature amplitudes of these MWs varied between the four cross‐mountain flight legs occurring between 6:10UT and 9:10UT. The average spectral T′ amplitudes near 80 km in altitude ranged from 7–13 K for the 220 km λH MW and 4–8 K for the smaller λH MWs. These amplitudes decayed significantly up to 90 km, where a critical level for MWs was present. The average MF per unit mass near 80 km in altitude ranged from ~13 to 60 m2/s2 across the varying spectra over the duration of the research flight and decayed to ~0 by 88 km in altitude. These MFs are large compared to zonal means and highlight the importance of MWs in the momentum budget of the mesosphere and lower thermosphere at times when they reach these altitudes.

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Section: Temperature and Mf Measurements And Validationsupporting

confidence: 88%

“…Assuming hydrostatic motions, the MF per unit mass for a given GW can be calculated as (Bossert et al, ; Ern et al, ; Fritts et al, ),

MF = < u_{H}^{'} w^{'} > = < \frac{1}{2} {(\frac{T^{'}}{\overset{T}{true}} \frac{g}{N})}^{2} ((), \frac{k_{H}}{m}) >

m^{2} = \frac{N^{2}}{{((), c - U_{H})}^{2}} - \frac{1}{4 H^{2}} - k_{H}^{2}

where c is the Earth‐relative phase speed assumed to be ~0 m/s for the observed presumed MWs and U H is the background wind in the direction of the MW horizontal wavenumber vector.…”

Section: Temperature and Mf Measurements And Validationmentioning

confidence: 99%

Momentum Flux Spectra of a Mountain Wave Event Over New Zealand

et al. 2018

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“…PMC observations have the potential to contribute to such a climatology at a specific season and altitude, but airglow data will be needed to address their statistics at other seasons and lower latitudes. In contrast, satellite characterization of GW variances spans all latitudes and seasons and large altitude ranges but is largely insensitive to the smaller‐ λ h and larger‐ ω i GWs expected to contribute most to energy and momentum deposition at all altitudes (Fritts, Vosper, et al, ; Preusse et al, ).…”

Section: Discussionmentioning

confidence: 99%

PMC Turbo: Studying Gravity Wave and Instability Dynamics in the Summer Mesosphere Using Polar Mesospheric Cloud Imaging and Profiling From a Stratospheric Balloon

et al. 2019

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The Polar Mesospheric Cloud Turbulence (PMC Turbo) experiment was designed to observe and quantify the dynamics of small‐scale gravity waves (GWs) and instabilities leading to turbulence in the upper mesosphere during polar summer using instruments aboard a stratospheric balloon. The PMC Turbo scientific payload comprised seven high‐resolution cameras and a Rayleigh lidar. Overlapping wide and narrow camera field of views from the balloon altitude of ~38 km enabled resolution of features extending from ~20 m to ~100 km at the PMC layer altitude of ~82 km. The Rayleigh lidar provided profiles of temperature below the PMC altitudes and of the PMCs throughout the flight. PMCs were imaged during an ~5.9‐day flight from Esrange, Sweden, to Northern Canada in July 2018. These data reveal sensitivity of the PMCs and the dynamics driving their structure and variability to tropospheric weather and larger‐scale GWs and tides at the PMC altitudes. Initial results reveal strong modulation of PMC presence and brightness by larger‐scale waves, significant variability in the occurrence of GWs and instability dynamics on time scales of hours, and a diversity of small‐scale dynamics leading to instabilities and turbulence at smaller scales. At multiple times, the overall field of view was dominated by extensive and nearly continuous GWs and instabilities at horizontal scales from ~2 to 100 km, suggesting sustained turbulence generation and persistence. At other times, GWs were less pronounced and instabilities were localized and/or weaker, but not absent. An overview of the PMC Turbo experiment motivations, scientific goals, and initial results is presented here.

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“…The campaign revealed that mesospheric activity and wave breaking was present on days where surface wind forcing was small. If the surface wind forcing was too large, the mountain wave would break in the stratosphere, due to having a large amplitude, and would dissipate before reaching the mesosphere (Ehard et al, ; Fritts et al, ; Kaifler et al, ). Despite significant advancement, very little is still known about the spectra and importance of nonprimary waves in the upper atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Secondary Gravity Waves Generated by Breaking Mountain Waves Over Europe

et al. 2020

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A strong mountain wave, observed over Central Europe on 12 January 2016, is simulated in 2D under two fixed background wind conditions representing opposite tidal phases. The aim of the simulation is to investigate the breaking of the mountain wave and subsequent generation of nonprimary waves in the upper atmosphere. The model results show that the mountain wave first breaks as it approaches a mesospheric critical level creating turbulence on horizontal scales of 8–30 km. These turbulence scales couple directly to horizontal secondary waves scales, but those scales are prevented from reaching the thermosphere by the tidal winds, which act like a filter. Initial secondary waves that can reach the thermosphere range from 60 to 120 km in horizontal scale and are influenced by the scales of the horizontal and vertical forcing associated with wave breaking at mountain wave zonal phase width, and horizontal wavelength scales. Large‐scale nonprimary waves dominate over the whole duration of the simulation with horizontal scales of 107–300 km and periods of 11–22 minutes. The thermosphere winds heavily influence the time‐averaged spatial distribution of wave forcing in the thermosphere, which peaks at 150 km altitude and occurs both westward and eastward of the source in the 2 UT background simulation and primarily eastward of the source in the 7 UT background simulation. The forcing amplitude is ∼2 × that of the primary mountain wave breaking and dissipation. This suggests that nonprimary waves play a significant role in gravity waves dynamics and improved understanding of the thermospheric winds is crucial to understanding their forcing distribution.

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Large‐Amplitude Mountain Waves in the Mesosphere Accompanying Weak Cross‐Mountain Flow During DEEPWAVE Research Flight RF22

Cited by 35 publications

References 103 publications

Momentum Flux Spectra of a Mountain Wave Event Over New Zealand

Momentum Flux Spectra of a Mountain Wave Event Over New Zealand

PMC Turbo: Studying Gravity Wave and Instability Dynamics in the Summer Mesosphere Using Polar Mesospheric Cloud Imaging and Profiling From a Stratospheric Balloon

Secondary Gravity Waves Generated by Breaking Mountain Waves Over Europe

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