Meteor radar observations of vertically propagating low-frequency inertia-gravity waves near the southern polar mesopause region

2017 ◽  
Vol 122 (4) ◽  
pp. 4777-4800 ◽  
Author(s):  
I.-S. Song ◽  
C. Lee ◽  
J.-H. Kim ◽  
G. Jee ◽  
Y.-H. Kim ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Low Frequency ◽  
Meteor Radar ◽  
Mesopause Region ◽  
Radar Observations ◽  
Vertically Propagating ◽  
Inertia Gravity Waves

scholarly journals Meteor radar observations of mesopause region long-period temperature oscillations

2016 ◽  
Vol 14 ◽  
pp. 169-174
Author(s):  
Ch. Jacobi ◽  
N. Samtleben ◽  
G. Stober
Keyword(s):  
Time Scales ◽  
Lower Thermosphere ◽  
Planetary Waves ◽  
Meteor Radar ◽  
Mesopause Region ◽  
Radar Observations ◽  
Long Period ◽  
Temperature Oscillations ◽  
Wind Measurements

Abstract. Meteor radar observations of mesosphere/lower thermosphere (MLT) daily temperatures have been performed at Collm, Germany since August 2004. The data have been analyzed with respect to long-period oscillations at time scales of 2–30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The oscillations may be considered as the signature of planetary waves. The results are compared with analyses from radar wind measurements. Moreover, the temperature oscillations show considerable year-to-year variability. In particular, amplitudes of the quasi 5-day oscillation have increased during the last decade, and the quasi 10-day oscillations are larger if the equatorial stratospheric winds are eastward.

scholarly journals Meteor radar measurements of mean winds and tides over Collm (51.3° N, 13° E) and comparison with LF drift measurements 2005–2007

2011 ◽  
Vol 9 ◽  
pp. 335-341 ◽  
Author(s):  
C. Jacobi
Keyword(s):  
Diffusion Coefficients ◽  
Lower Thermosphere ◽  
Low Frequency ◽  
Meteor Radar ◽  
Mesopause Region ◽  
Wind Measurements ◽  
Radar Measurements ◽  
Long Term Trend ◽  
Temporal Overlap

Abstract. An all-sky VHF meteor radar (MR) has been continuously operated at Collm (51.3° N, 13° E) since summer 2004. The radar measures meteor parameters, diffusion coefficients, and horizontal winds in the mesopause region. There exists a temporal overlap of the MR wind measurements with co-located low-frequency (LF) ionospheric drift measurements until 2007. Comparison of MR and LF semidiurnal tidal phases allows to empirically determine the virtual height overestimation of LF reflection heights due to the group retardation of LF waves. LF reference heights have to be reduced by up to 20 km to match real heights. Correction of LF heights for group retardation allows to determine the wind underestimation by the LF method compared with meteor radar measurements and opens the possibility to continue long-term trend analysis using mesosphere/lower thermosphere winds.

On the effects of frontogenetic strain on symmetric instability and inertia–gravity waves

2012 ◽  
Vol 711 ◽  
pp. 620-640 ◽  
Author(s):  
Leif N. Thomas
Keyword(s):  
Gravity Waves ◽  
Richardson Number ◽  
Low Frequency ◽  
Deformation Field ◽  
Vertical Shear ◽  
Geostrophic Flow ◽  
Ageostrophic Circulation ◽  
The Waves ◽  
Symmetric Instability ◽  
Inertia Gravity Waves

AbstractThe dynamics of symmetric instability and two-dimensional inertia–gravity waves in a baroclinic geostrophic flow undergoing frontogenesis is analysed. A frontogenetic strain associated with a balanced deformation field drives an ageostrophic circulation and temporal variations in the basic state that significantly affect the properties of perturbations to the background flow. For stable stratification, perturbations to the basic state result in symmetric instability or inertia–gravity waves, depending on the sign of the Ertel potential vorticity and the magnitude of the Richardson number of the geostrophic flow. The kinetic energy (KE) of both types of motion is suppressed by frontogenetic strain due to the vertical shear in the ageostrophic circulation. This is because the perturbation streamlines tilt with the ageostrophic shear causing the disturbances to lose KE via shear production. The effect can completely dampen symmetric instability for sufficiently strong strain even though the source of KE for the instability (the vertical shear in the geostrophic flow) increases with time. Inertia–gravity waves in a baroclinic flow undergoing frontogenesis simultaneously lose KE and extract KE from the deformation field as they decay. This is because the horizontal velocity of the waves becomes rectilinear, resulting in a Reynolds stress that draws energy from the balanced flow. The process is most effective for waves of low frequency and for a geostrophic flow with low Richardson number. However, even in a background flow that is initially strongly stratified, frontogenesis leads to an exponentially fast reduction in the Richardson number, facilitating a rapid energy extraction by the waves. The KE transferred from the deformation field is ultimately lost to the unbalanced ageostrophic circulation through shear production, hence the inertia–gravity waves play a catalytic role in loss of balance. Given the large amount of KE in low-frequency inertia–gravity waves and the ubiquitous combination of strain and baroclinic geostrophic currents in the ocean, it is estimated that this mechanism could play a significant role in the removal of KE from both the internal wave and mesoscale eddy fields.

scholarly journals New method of estimating temperatures near the mesopause region using meteor radar observations

2016 ◽  
Vol 43 (20) ◽  
pp. 10,580-10,585 ◽  
Author(s):  
Changsup Lee ◽  
Jeong-Han Kim ◽  
Geonhwa Jee ◽  
Wonseok Lee ◽  
In-Sun Song ◽  
...  
Keyword(s):  
New Method ◽  
Meteor Radar ◽  
Mesopause Region ◽  
Radar Observations
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