Does Strong Tropospheric Forcing Cause Large‐Amplitude Mesospheric Gravity Waves? A DEEPWAVE Case Study

Bramberger, Martina; Dörnbrack, Andreas; Bossert, Katrina; Ehard, Benedikt; Fritts, David C.; Kaifler, Bernd; Mallaun, Christian; Orr, Andrew; Pautet, P. D.; Rapp, Markus; Taylor, Michael J.; Williams, B. P.; Witschas, Benjamin

doi:10.1002/2017jd027371

Cited by 41 publications

(64 citation statements)

References 60 publications

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“…The orientation can be explained by the difference in the GW sources. AMTM observations obtained during DEEPWAVE exhibited numerous N‐S aligned standing waves, which were identified as mountain waves (e.g., Bossert et al, ; Bramberger et al, ). Furthermore, this correlation between the sources and the GWs observed in the middle and upper atmosphere has been already noticed.…”

Section: Discussionmentioning

confidence: 99%

Regional Distribution of Mesospheric Small‐Scale Gravity Waves During DEEPWAVE

et al. 2019

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The Deep Propagating Gravity Wave Experiment project took place in June and July 2014 in New Zealand. Its overarching goal was to study gravity waves (GWs) as they propagate from the ground up to ~100 km, with a large number of ground‐based, airborne, and satellite instruments, combined with numerical forecast models. A suite of three mesospheric airglow imagers operated onboard the NSF Gulfstream V (GV) aircraft during 25 nighttime flights, recording the GW activity at OH altitude over a large region (>7,000,000 km2). Analysis of this data set reveals the distribution of the small‐scale GW mean power and direction of propagation. GW activity occurred everywhere and during every flight, even over open oceans with no neighboring tropospheric sources. Over the mountainous regions (New Zealand, Tasmania, isolated islands), mean power reached high values (more than 100 times larger than over the waters), but with a considerable variability. This variability existed from day to day over the same region, but even during the same flight, depending on forcing strength and on the middle atmosphere conditions. Results reveal a strong correlation between tropospheric sources, satellite stratospheric measurements, and mesosphere lower thermosphere airglow observations. The large‐amplitude GWs only account for a small amount of the total (~6%), even though they carry the most momentum and energy. The weaker wave activity measured over the oceans might originate from distance sources (polar vortex, weather fronts), implying that a ducted mechanism helped for their long range propagation.

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Section: Discussionmentioning

confidence: 99%

Regional Distribution of Mesospheric Small‐Scale Gravity Waves During DEEPWAVE

et al. 2019

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“…These initial observations, and advancing lidar and imaging capabilities, were among the many scientific opportunities and open questions that motivated DEEPWAVE (Fritts, Smith, et al, ). To date, multiple DEEPWAVE studies have addressed a diversity of MW dynamics extending to altitudes of ~90 km and of their effects extending to higher altitudes (e.g., Bossert et al, , ; Bramberger et al, ; Broutman et al, ; Eckermann et al, ; Fritts, Smith, et al, ; Kaifler et al, ; Pautet et al, ). Similar MW and more general GW studies are now being performed using ground‐based lidars, radars, and airglow imagers (e.g., Baumgarten et al, ; Hecht et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Orographic GWs, or mountain waves (MWs), arise wherever there is significant terrain, have spatial scales dictated by the terrain scales and cross‐mountain flows, and can have both upstream and downstream influences. The horizontal scales that readily achieve higher altitudes can be as small as ~10–20 km and as large as ~200 km or larger, but their dynamics and ability to propagate to higher altitudes depend strongly on the intervening wind and stability profiles and whether these dynamics are linear or nonlinear (e.g., Bramberger et al, ; Durran, ; Grubišić et al, ; Klemp & Lilly, ; Lilly & Kennedy, ; Lilly & Lester, ; Nastrom & Fritts, ; Shutts & Vosper, ; R. B. Smith et al, ; Vosper, ; Vosper et al, ). Where strong zonal winds extend into the stratosphere, orographic sources lead to the middle‐ to high‐latitude GW hot spots identified in high‐resolution satellite radiance data (e.g., Eckermann & Preusse, ; Hendricks et al, ; Jiang et al, ; Wu & Eckermann, ).…”

Section: Introductionmentioning

confidence: 99%

“…DEEPWAVE also employed the German DLR Falcon research aircraft and extensive ground‐based instrumentation on the NZ South Island (SI) and Tasmania (Fritts, Smith, et al, ). These data are enabling multiple studies of various GW dynamics from the surface to ~100 km (e.g., Bossert et al, , ; Bramberger et al, ; Eckermann et al, ; Heale et al, ; Kaifler et al, ; Kruse & Smith, ; Pautet et al, ; R. B. Smith et al, ).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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Mountain wave (MW) propagation and dynamics extending into the upper mesosphere accompanying weak forcing are examined using in situ and remote‐sensing measurements aboard the National Science Foundation/National Center for Atmospheric Research Gulfstream V (GV) research aircraft and the German Aerospace Center Falcon. The measurements were obtained during Falcon flights FF9 and FF10 and GV Research Flight RF22 of the Deep Propagating Gravity Wave Experiment (DEEPWAVE) performed over Mount Cook, New Zealand, on 12 and 13 July 2014. In situ measurements revealed both trapped lee waves having zonal wavelengths of λx ~ 12 km and less, and larger‐scale, vertically propagating MWs primarily at λx ~ 20–60 km and ~100–300 km extending from west to ~400 km east of Mount Cook. GV Rayleigh lidar measurements from 25‐ to 60‐km altitudes showed that the weak forcing and zonal winds that increased from ~12 m/s at 12 km to ~40 and 130 m/s at 30 and 55 km, respectively, enabled largely linear MW propagation and strong amplitude growth with altitude into the mesosphere. GV Na lidar and airglow imager measurements revealed an extensive MW response from ~70 to 87 km with large amplitudes and vertical displacements at λx ~ 40–300 km but with both decreasing with altitude approaching a critical level near 90 km. These MWs exhibited large‐scale MW breaking and among the largest sustained momentum fluxes observed in the mesosphere. UK Met Office Unified Model simulations of the RF22 MW event captured many aspects of the observed MW field and revealed that despite the dominant large‐scale MW responses in the stratosphere, the major momentum fluxes accompanied smaller‐scale waves.

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“…This layer was termed “valve layer” since it controlled the mountain wave momentum flux (WMF) through it. However, a more recent case study of DEEPWAVE by Bramberger et al () found that large‐amplitude gravity waves can also be generated by strong tropospheric forcing.…”

Section: Introductionmentioning

confidence: 99%

Directional Absorption of Parameterized Mountain Waves and Its Influence on the Wave Momentum Transport in the Northern Hemisphere

Tang²,

Wang³

et al. 2018

JGR Atmospheres

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The directional absorption of mountain waves in the Northern Hemisphere is assessed by examination of horizontal wind rotation using the 2.5° × 2.5° European Centre for Medium‐Range Weather Forecasts ERA‐Interim reanalysis between 2011 and 2016. In the deep layer of troposphere and stratosphere, the horizontal wind rotates by more than 120° all over the Northern Hemisphere primary mountainous areas, with the rotation mainly occurring in the troposphere (stratosphere) of lower (middle to high) latitudes. The rotation of tropospheric wind increases markedly in summer over the Tibetan Plateau and Iranian Plateau, due to the influence of Asian summer monsoonal circulation. The influence of directional absorption of mountain waves on the mountain wave momentum transport is also studied using a new parameterization scheme of orographic gravity wave drag (OGWD) which accounts for the effect of directional wind shear. Owing to the directional absorption, the wave momentum flux is attenuated by more than 50% in the troposphere of lower latitudes, producing considerable orographic gravity wave lift which is normal to the mean wind. Compared with the OGWD produced in traditional schemes assuming a unidirectional wind profile, the OGWD in the new scheme is suppressed in the lower stratosphere but enhanced in the upper stratosphere and lower mesosphere. This is because the directional absorption of mountain waves in the troposphere reduces the wave amplitude in the stratosphere. Consequently, mountain waves are prone to break at higher altitudes, which favors the production of stronger OGWD given the decrease of air density with height.

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Does Strong Tropospheric Forcing Cause Large‐Amplitude Mesospheric Gravity Waves? A DEEPWAVE Case Study

Cited by 41 publications

References 60 publications

Regional Distribution of Mesospheric Small‐Scale Gravity Waves During DEEPWAVE

Regional Distribution of Mesospheric Small‐Scale Gravity Waves During DEEPWAVE

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

Directional Absorption of Parameterized Mountain Waves and Its Influence on the Wave Momentum Transport in the Northern Hemisphere

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