scholarly journals Intra-annual variations of spectrally resolved gravity wave activity in the UMLT region

2020 ◽  
Author(s):  
René Sedlak ◽  
Alexandra Zuhr ◽  
Carsten Schmidt ◽  
Sabine Wüst ◽  
Michael Bittner ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Annual Cycle ◽  
Large Scale ◽  
Wave Spectrum ◽  
Wave Activity ◽  
Environmental Research ◽  
Research Station ◽  
Period Range ◽  
Annual Variations ◽  
Spectrally Resolved

Abstract. The period range between 6 min and 480 min is known to represent the major part of the gravity wave spectrum driving mesospheric dynamics. We present a method using wavelet analysis to calculate gravity wave activity with a high period-resolution and apply it to temperature data acquired with the OH* airglow spectrometers GRIPS (GRound-based Infrared P-branch Spectrometer) within the framework of the NDMC (Network for the Detection of Mesospheric Change; https://ndmc.dlr.de). We analyse data measured at the NDMC sites Abastumani in Georgia (ABA, 41.75° N, 42.82° E), ALOMAR in Norway (ALR, 69.28° N, 16.01° E), Neumayer III in the Antarctic (NEU, 70.67° S, 8.27° W), Observatoire de Haute-Provence in France (OHP, 43.93° N, 5.71° E), Oberpfaffenhofen in Germany (OPN, 48.09° N, 11.28° E), Sonnblick in Austria (SBO, 47.05° N, 12.95° E), Tel Aviv in Israel (TAV, 32.11° N, 34.80° E), and the Environmental Research Station Schneefernerhaus on top of Mt. Zugspitze, Germany (UFS, 47.42° N, 10.98° E). All eight instruments are identical in construction and deliver consistent and comparable data sets. For periods shorter than 60 min, gravity wave activity is found to be relatively low and hardly shows any seasonal variability on the time scale of months. We find a semi-annual cycle with maxima during winter and summer for gravity waves with periods longer than 60 min, which gradually develops into an annual cycle with a winter maximum for longer periods. The transition from a semi-annual pattern to a primarily annual pattern occurs around a gravity wave period of 200 min. Although there are indications of enhanced gravity wave sources above mountainous terrain, the overall pattern of gravity wave activity does not differ significantly for the abovementioned observation sites. Thus, large-scale mechanisms such as stratospheric wind filtering seem to dominate the temporal course of mesospheric gravity wave activity.

scholarly journals Intra-annual variations of spectrally resolved gravity wave activity in the upper mesosphere/lower thermosphere (UMLT) region

2020 ◽  
Vol 13 (9) ◽  
pp. 5117-5128
Author(s):  
René Sedlak ◽  
Alexandra Zuhr ◽  
Carsten Schmidt ◽  
Sabine Wüst ◽  
Michael Bittner ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Annual Cycle ◽  
Large Scale ◽  
Middle Atmosphere ◽  
Wave Spectrum ◽  
Lower Thermosphere ◽  
Wave Activity ◽  
Environmental Research ◽  
Research Station ◽  
Period Range

Abstract. The period range between 6 and 480 min is known to represent the major part of the gravity wave spectrum driving mesospheric dynamics. We present a method using wavelet analysis to calculate gravity wave activity with a high period resolution and apply it to temperature data acquired with the OH* airglow spectrometers called GRIPS (GRound-based Infrared P-branch Spectrometer) within the framework of the NDMC (Network for the Detection of Mesospheric Change; https://ndmc.dlr.de, last access: 22 September 2020). We analyse data measured at the NDMC sites Abastumani in Georgia (ABA; 41.75∘ N, 42.82∘ E), ALOMAR (Arctic Lidar Observatory for Middle Atmosphere Research) in Norway (ALR; 69.28∘ N, 16.01∘ E), Neumayer Station III in the Antarctic (NEU; 70.67∘ S, 8.27∘ W), Observatoire de Haute-Provence in France (OHP; 43.93∘ N, 5.71∘ E), Oberpfaffenhofen in Germany (OPN; 48.09∘ N, 11.28∘ E), Sonnblick in Austria (SBO; 47.05∘ N, 12.95∘ E), Tel Aviv in Israel (TAV; 32.11∘ N, 34.80∘ E), and the Environmental Research Station Schneefernerhaus on top of Zugspitze mountain in Germany (UFS; 47.42∘ N, 10.98∘ E). All eight instruments are identical in construction and deliver consistent and comparable data sets. For periods shorter than 60 min, gravity wave activity is found to be relatively low and hardly shows any seasonal variability on the timescale of months. We find a semi-annual cycle with maxima during winter and summer for gravity waves with periods longer than 60 min, which gradually develops into an annual cycle with a winter maximum for longer periods. The transition from a semi-annual pattern to a primarily annual pattern starts around a gravity wave period of 200 min. Although there are indications of enhanced gravity wave sources above mountainous terrain, the overall pattern of gravity wave activity does not differ significantly for the abovementioned observation sites. Thus, large-scale mechanisms such as stratospheric wind filtering seem to dominate the evolution of mesospheric gravity wave activity.

scholarly journals Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

2018 ◽  
Vol 11 (1) ◽  
pp. 215-232 ◽  
Author(s):  
Catrin I. Meyer ◽  
Manfred Ern ◽  
Lars Hoffmann ◽  
Quang Thai Trinh ◽  
M. Joan Alexander
Keyword(s):  
High Resolution ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Wave Spectrum ◽  
Horizontal Resolution ◽  
Wave Activity ◽  
Large Variability ◽  
Wave Event ◽  
The Waves

Abstract. We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a statistical basis. The complete HIRDLS measurement period from January 2005 to March 2008 is covered. The seasonal and latitudinal distributions of gravity wave activity as observed by AIRS and HIRDLS agree well. A strong annual cycle at mid- and high latitudes is found in time series of gravity wave variances at 42 km, which has its maxima during wintertime and its minima during summertime. The variability is largest during austral wintertime at 60∘ S. Variations in the zonal winds at 2.5 hPa are associated with large variability in gravity wave variances. Altogether, gravity wave variances of AIRS and HIRDLS are complementary to each other. Large parts of the gravity wave spectrum are covered by joint observations. This opens up fascinating vistas for future gravity wave research.

scholarly journals Influence of the spatial distribution of gravity wave activity on the middle atmospheric circulation and transport

2016 ◽  
Author(s):  
Petr Šácha ◽  
Friederike Lilienthal ◽  
Christoph Jacobi ◽  
Petr Pišoft
Keyword(s):  
Spatial Distribution ◽  
Gravity Wave ◽  
Atmospheric Circulation ◽  
Large Scale ◽  
Mechanistic Model ◽  
Polar Vortex ◽  
Wave Activity ◽  
Residual Circulation ◽  
Density Profiles ◽  
Longitudinal Variability

Abstract. Analyzing GPS radio occultation density profiles, we have recently pointed out a localized area of enhanced gravity wave (GW) activity and breaking in the lower stratosphere of the Eastern Asia/North-western Pacific (EA/NP) region. With a mechanistic model for the middle and upper atmosphere (MUAM), experiments are performed to study a possible effect of such a localized IGW breaking region on the large-scale circulation and transport and also more generally, possible influence of spatial distribution of gravity wave activity on the middle atmospheric circulation and transport. The results indicate an important role of the spatial distribution of GW activity for the polar vortex stability, formation of planetary waves (PW) and for the strength and structure of the zonal mean residual circulation. Also, a possible effect of a zonally asymmetric GW breaking in the longitudinal variability of Brewer–Dobson circulation is analyzed. Finally, consequences of our results for a variety of research topics (Sudden Stratospheric Warmings, atmospheric blocking, teleconnections and a compensation mechanism between resolved and unresolved drag) are discussed.

scholarly journals The MaCWAVE program to study gravity wave influences on the polar mesosphere

2006 ◽  
Vol 24 (4) ◽  
pp. 1159-1173 ◽  
Author(s):  
R. A. Goldberg ◽  
D. C. Fritts ◽  
F. J. Schmidlin ◽  
B. P. Williams ◽  
C. L. Croskey ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Large Scale ◽  
Planetary Wave ◽  
Middle Atmosphere ◽  
Lower Thermosphere ◽  
Wave Structure ◽  
Wave Activity ◽  
Small Scale ◽  
Mountain Waves ◽  
The Mean

Abstract. MaCWAVE (Mountain and Convective Waves Ascending VErtically) was a highly coordinated rocket, ground-based, and satellite program designed to address gravity wave forcing of the mesosphere and lower thermosphere (MLT). The MaCWAVE program was conducted at the Norwegian Andøya Rocket Range (ARR, 69.3° N) in July 2002, and continued at the Swedish Rocket Range (Esrange, 67.9° N) during January 2003. Correlative instrumentation included the ALOMAR MF and MST radars and RMR and Na lidars, Esrange MST and meteor radars and RMR lidar, radiosondes, and TIMED (Thermosphere Ionosphere Mesosphere Energetics and Dynamics) satellite measurements of thermal structures. The data have been used to define both the mean fields and the wave field structures and turbulence generation leading to forcing of the large-scale flow. In summer, launch sequences coupled with ground-based measurements at ARR addressed the forcing of the summer mesopause environment by anticipated convective and shear generated gravity waves. These motions were measured with two 12-h rocket sequences, each involving one Terrier-Orion payload accompanied by a mix of MET rockets, all at ARR in Norway. The MET rockets were used to define the temperature and wind structure of the stratosphere and mesosphere. The Terrier-Orions were designed to measure small-scale plasma fluctuations and turbulence that might be induced by wave breaking in the mesosphere. For the summer series, three European MIDAS (Middle Atmosphere Dynamics and Structure) rockets were also launched from ARR in coordination with the MaCWAVE payloads. These were designed to measure plasma and neutral turbulence within the MLT. The summer program exhibited a number of indications of significant departures of the mean wind and temperature structures from ``normal" polar summer conditions, including an unusually warm mesopause and a slowing of the formation of polar mesospheric summer echoes (PMSE) and noctilucent clouds (NLC). This was suggested to be due to enhanced planetary wave activity in the Southern Hemisphere and a surprising degree of inter-hemispheric coupling. The winter program was designed to study the upward propagation and penetration of mountain waves from northern Scandinavia into the MLT at a site favored for such penetration. As the major response was expected to be downstream (east) of Norway, these motions were measured with similar rocket sequences to those used in the summer campaign, but this time at Esrange. However, a major polar stratospheric warming just prior to the rocket launch window induced small or reversed stratospheric zonal winds, which prevented mountain wave penetration into the mesosphere. Instead, mountain waves encountered critical levels at lower altitudes and the observed wave structure in the mesosphere originated from other sources. For example, a large-amplitude semidiurnal tide was observed in the mesosphere on 28 and 29 January, and appears to have contributed to significant instability and small-scale structures at higher altitudes. The resulting energy deposition was found to be competitive with summertime values. Hence, our MaCWAVE measurements as a whole are the first to characterize influences in the MLT region of planetary wave activity and related stratospheric warmings during both winter and summer.

scholarly journals Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

2017 ◽  
Author(s):  
Catrin I. Meyer ◽  
Manfred Ern ◽  
Lars Hoffmann ◽  
Quang Thai Trinh ◽  
M. Joan Alexander
Keyword(s):  
High Resolution ◽  
Gravity Wave ◽  
Gravity Waves ◽  
Momentum Flux ◽  
Wave Spectrum ◽  
Horizontal Resolution ◽  
Wave Activity ◽  
Large Variability ◽  
Wave Event ◽  
The Waves

Abstract. We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is nine times better than that of the operational retrieval. HIRDLS provides 2D spectral formation of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short horizontal wavelength gravity waves and HIRDLS as a limb sounder is more sensitive to short vertical wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS agree often very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are conform. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths compared to HIRDLS. However, AIRS has a much higher horizontal resolution and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a statistical basis. The complete HIRDLS measurement period from January 2005 to March 2008 is covered. The seasonal and latitudinal distributions of gravity wave activity as observed by AIRS and HIRDLS fit well. A strong annual cycle at mid and high latitudes is found in time series of gravity wave variances at 42 km, which has during wintertime its maxima and during summertime its minima. During austral wintertime at 60° S the variability is largest. Variations in the zonal winds at 2.5 hPa are associated with large variability in gravity wave variances. Altogether, gravity wave variances of AIRS and HIRDLS are conform and complementary to each other. Thereby large parts of the gravity wave spectrum are covered by joint observations. This opens up fascinating vistas for future gravity wave research.

scholarly journals Influence of the spatial distribution of gravity wave activity on the middle atmospheric dynamics

2016 ◽  
Vol 16 (24) ◽  
pp. 15755-15775 ◽  
Author(s):  
Petr Šácha ◽  
Friederike Lilienthal ◽  
Christoph Jacobi ◽  
Petr Pišoft
Keyword(s):  
Spatial Distribution ◽  
Gravity Wave ◽  
Large Scale ◽  
Mechanistic Model ◽  
Polar Vortex ◽  
Wave Activity ◽  
Northwestern Pacific ◽  
Residual Circulation ◽  
Teleconnection Patterns ◽  
Longitudinal Variability

Abstract. Analysing GPS radio occultation density profiles, we have recently pointed out a localised area of enhanced gravity wave (GW) activity and breaking in the lower stratosphere of the east Asian–northwestern Pacific (EA/NP) region. With a mechanistic model of the middle and upper atmosphere, experiments are performed to study the possible effect of such a localised GW breaking region on large-scale circulation and transport and, more generally, a possible influence of the spatial distribution of gravity wave activity on middle atmospheric dynamics.The results indicate the important role of the spatial distribution of GW activity for polar vortex stability, formation of planetary waves and for the strength and structure of zonal-mean residual circulation. Furthermore, a possible effect of a zonally asymmetric GW breaking in the longitudinal variability of the Brewer–Dobson circulation is analysed. Finally, consequences of our results for a variety of research topics (e.g. sudden stratospheric warming, atmospheric blocking, teleconnection patterns and a compensation mechanism between resolved and unresolved drag) are discussed.

Nonlinear energy transfer in a narrow gravity-wave spectrum

1979 ◽  
Vol 368 (1733) ◽  
pp. 239-265 ◽  
Keyword(s):  
Energy Transfer ◽  
Gravity Wave ◽  
Large Scale ◽  
Wind Wave ◽  
Wave Spectrum ◽  
Spectral Width ◽  
First Order ◽  
Nonlinear Energy Transfer ◽  
First Order Theory ◽  
Nonlinear Energy

A method is developed for efficient calculation of the rate of energy transfer due to nonlinear resonant interaction in a narrow gravity wave spectrum according to Hasselmann’s theory. The coupling coefficient is perturbed to the first order (in spectral width), and it is shown that for Gaussian spectra the sixfold integral is reduced to a single integration. Comparisons with the limiting case of Longuet-Higgins and Fox show that the effects of the spectral width of a typical narrow wind wave spectrum on the nonlinear energy transfer are very important and cannot be neglected. It is also shown that when these effects are included, the present first order theory is in excellent agreement with large scale numerical computations of Jonswap (Joint North Sea Wave Project) on the forward face of the spectrum. Furthermore, preliminary comparisons with the growth rate of wind-wave spectra measured in Lake Ontario tend to substantiate the Jonswap conclusion that ‘Most of the wave growth on the forward face of the spectrum can be attributed to the nonlinear transfer to longer waves.´

scholarly journals Influence of the cloud-level neutral layer on the vertical propagation of topographically generated gravity waves on Venus

2019 ◽  
Vol 71 (1) ◽  
Author(s):  
Takeru Yamada ◽  
Takeshi Imamura ◽  
Tetsuya Fukuhara ◽  
Makoto Taguchi
Keyword(s):  
Layer Thickness ◽  
Gravity Wave ◽  
Local Time ◽  
Gravity Waves ◽  
Analytical Approach ◽  
Wave Activity ◽  
Neutral Layer ◽  
Low Latitudes ◽  
Vertical Propagation ◽  
The Waves

AbstractThe reason for stationary gravity waves at Venus’ cloud top to appear mostly at low latitudes in the afternoon is not understood. Since a neutral layer exists in the lower part of the cloud layer, the waves should be affected by the neutral layer before reaching the cloud top. To what extent gravity waves can propagate vertically through the neutral layer has been unclear. To examine the possibility that the variation of the neutral layer thickness is responsible for the dependence of the gravity wave activity on the latitude and the local time, we investigated the sensitivity of the vertical propagation of gravity waves on the neutral layer thickness using a numerical model. The results showed that stationary gravity waves with zonal wavelengths longer than 1000 km can propagate to the cloud-top level without notable attenuation in the neutral layer with realistic thicknesses of 5–15 km. This suggests that the observed latitudinal and local time variation of the gravity wave activity should be attributed to processes below the cloud. An analytical approach also showed that gravity waves with horizontal wavelengths shorter than tens of kilometers would be strongly attenuated in the neutral layer; such waves should originate in the altitude region above the neutral layer.

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