First observational evidence of the modulation of gravity wave activity in the low latitude middle atmosphere by equatorial waves

2002 ◽  
Vol 29 (6) ◽  
pp. 1-1-1-4 ◽  
Author(s):  
K. Parameswaran ◽  
K. Rajeev ◽  
M. N. Sasi ◽  
Geetha Ramkumar ◽  
B. V. Krishna Murthy
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Activity ◽  
Observational Evidence ◽  
Equatorial Waves ◽  
Low Latitude

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 Turbulence characteristics in the tropical mesosphere as obtained by MST radar at Gadanki (13.5° N, 79.2° E)

2001 ◽  
Vol 19 (8) ◽  
pp. 1019-1025 ◽  
Author(s):  
M. N. Sasi ◽  
L. Vijayan
Keyword(s):  
Seasonal Variation ◽  
Gravity Wave ◽  
Middle Atmosphere ◽  
Indian Subcontinent ◽  
Southwest Monsoon ◽  
Wave Activity ◽  
Tropical Meteorology ◽  
Monsoon Period ◽  
Mst Radar ◽  
Summer Maximum

Abstract. Turbulent kinetic energy dissipation rates (ε) and eddy diffusion coefficients (Kz) in the tropical mesosphere over Gadanki (13.5° N, 79.2° E), estimated from Doppler widths of MST radar echoes (vertical beam), observed over a 3-year period, show a seasonal variation with a dominant summer maximum. The observed seasonal variation of ε and Kz in the mesosphere is only partially consistent with that of gravity wave activity inferred from mesospheric winds and temperatures measured by rockets for a period of 9 years at Trivandrum (8.5° N, 77° E) (which shows two equinox and one summer maxima) lying close to Gadanki. The summer maximum of mesospheric ε and Kz values appears to be related to the enhanced gravity wave activity over the low-latitude Indian subcontinent during the southwest monsoon period (June – September). Both ε and Kz in the mesosphere over Gadanki show an increase with an increase in height during all seasons. The absolute values of observed ε and Kz in the mesosphere (above ~80 km) does not show significant differences from those reported for high latitudes. Comparison of observed Kz values during the winter above Gadanki with those over Arecibo (18.5° N, 66° W) shows that they are not significantly different from each other above the ~80 km altitude.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; tropical meteorology; wave and tides)

scholarly journals Satellite observations of middle atmosphere gravity wave activity and dissipation during recent stratospheric warmings

2016 ◽  
Author(s):  
Manfred Ern ◽  
Quang Thai Trinh ◽  
Martin Kaufmann ◽  
Isabell Krisch ◽  
Peter Preusse ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Middle Atmosphere ◽  
Polar Vortex ◽  
Wave Activity ◽  
Planetary Waves ◽  
Absolute Gravity ◽  
Mountain Waves ◽  
Meridional Shape ◽  
Zonal Average

Abstract. Sudden stratospheric warmings (SSWs) are circulation anomalies in the polar region during winter. They mostly occur in the Northern Hemisphere and affect also surface weather and climate. Both planetary waves and gravity waves contribute to the onset and evolution of SSWs. While the role of planetary waves for SSW evolution has been recognized, the effect of gravity waves is still not fully understood, and has not been comprehensively analyzed based on global observations. In particular, information on the gravity wave driving of the background winds during SSWs is still missing. We investigate the boreal winters 2001/2002 until 2013/2014. Absolute gravity wave momentum fluxes and gravity wave dissipation (potential drag) are estimated from temperature observations of the satellite instruments HIRDLS and SABER. In agreement with previous work, we find that sometimes gravity wave activity is enhanced before the central date of major SSWs, particularly during vortex-split events. Often, SSWs are associated with polar-night jet oscillation (PJO) events. For these events, we find that gravity wave activity is strongly suppressed when winds reverse from eastward to westward (usually after the central date of a major SSW). In addition, gravity wave potential drag at the bottom of the newly forming eastward directed jet is remarkably weak, while considerable potential drag at the top of the jet likely contributes to the downward propagation of both the jet and the new elevated stratopause. During PJO events, we also find some indication for poleward propagation of gravity waves. Another striking finding is that obviously localized gravity wave sources, likely mountain waves and jet-generated gravity waves, play an important role during the evolution of SSWs and potentially contribute to the triggering of SSWs by preconditioning the shape of the polar vortex. The distribution of these hot spots is highly variable and strongly depends on the zonal and meridional shape of the background wind field, indicating that a pure zonal average view sometimes is a too strong simplification for the strongly perturbed conditions during the evolution of SSWs.

scholarly journals A climatology of medium-scale gravity wave activity in the midlatitude/low-latitude daytime upper thermosphere as observed by CHAMP

2014 ◽  
Vol 119 (3) ◽  
pp. 2187-2196 ◽  
Author(s):  
J. Park ◽  
H. Lühr ◽  
C. Lee ◽  
Y. H. Kim ◽  
G. Jee ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Wave Activity ◽  
Low Latitude ◽  
Medium Scale

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 Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

Atmosphere ◽  
2017 ◽  
Vol 8 (12) ◽  
pp. 27 ◽  
Author(s):  
Colin Triplett ◽  
Richard Collins ◽  
Kim Nielsen ◽  
V. Harvey ◽  
Kohei Mizutani
Keyword(s):  
Gravity Wave ◽  
Middle Atmosphere ◽  
Wave Activity ◽  
Flow Generation
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