Balloon‐Borne Observations of Short Vertical Wavelength Gravity Waves and Interaction With QBO Winds

2020 ◽  
Vol 125 (15) ◽  
Author(s):  
Robert A. Vincent ◽  
M. Joan Alexander
Keyword(s):  
Gravity Waves ◽  
Vertical Wavelength

scholarly journals Gravity waves observed from the Equatorial Wave Studies (EWS) campaign during 1999 and 2000 and their role in the generation of stratospheric semiannual oscillations

2006 ◽  
Vol 24 (10) ◽  
pp. 2481-2491 ◽  
Author(s):  
V. Deepa ◽  
G. Ramkumar ◽  
B. V. Krishna Murthy
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Propagation Characteristics ◽  
Mean Flow ◽  
Vertical Wavelength ◽  
Flow Acceleration ◽  
Equatorial Wave ◽  
The Mean ◽  
Phase Propagation ◽  
Rayleigh Lidar

Abstract. The altitude profiles of temperature fluctuations in the stratosphere and mesosphere observed with the Rayleigh Lidar at Gadanki (13.5° N, 79.2° E) on 30 nights during January to March 1999 and 21 nights during February to April 2000 were analysed to bring out the temporal and vertical propagation characteristics of gravity wave perturbations. The gravity wave perturbations showed periodicities in the 0.5–3-h range and attained large amplitudes (4–5 K) in the mesosphere. The phase propagation characteristics of gravity waves with different periods showed upward wave propagation with a vertical wavelength of 5–7 km. The mean flow acceleration computed from the divergence of momentum flux of gravity waves is compared with that calculated from monthly values of zonal wind obtained from RH-200 rockets flights. Thus, the contribution of gravity waves towards the generation of Stratospheric Semi Annual Oscillation (SSAO) is estimated.

scholarly journals Observations of Near-Inertial Internal Gravity Waves Radiating from a Frontal Jet

2013 ◽  
Vol 43 (6) ◽  
pp. 1225-1239 ◽  
Author(s):  
Matthew H. Alford ◽  
Andrey Y. Shcherbina ◽  
Michael C. Gregg
Keyword(s):  
Gravity Waves ◽  
Three Dimensional ◽  
Internal Gravity Wave ◽  
Internal Gravity Waves ◽  
Shear Layers ◽  
Adjustment Process ◽  
Vertical Wavelength ◽  
The North ◽  
Inertial Wave ◽  
The North Pacific

Abstract Shipboard ADCP and towed CTD measurements are presented of a near-inertial internal gravity wave radiating away from a zonal jet associated with the Subtropical Front in the North Pacific. Three-dimensional spatial surveys indicate persistent alternating shear layers sloping downward and equatorward from the front. As a result, depth-integrated ageostrophic shear increases sharply equatorward of the front. The layers have a vertical wavelength of about 250 m and a slope consistent with a wave of frequency 1.01f. They extend at least 100 km south of the front. Time series confirm that the shear is associated with a downward-propagating near-inertial wave with frequency within 20% of f. A slab mixed layer model forced with shipboard and NCEP reanalysis winds suggests that wind forcing was too weak to generate the wave. Likewise, trapping of the near-inertial motions at the low-vorticity edge of the front can be ruled out because of the extension of the features well south of it. Instead, the authors suggest that the wave arises from an adjustment process of the frontal flow, which has a Rossby number about 0.2–0.3.

scholarly journals A comprehensive observational filter for satellite infrared limb sounding of gravity waves

2014 ◽  
Vol 7 (10) ◽  
pp. 10771-10827
Author(s):  
Q. T. Trinh ◽  
S. Kalisch ◽  
P. Preusse ◽  
H.-Y. Chun ◽  
S. D. Eckermann ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Tangent Point ◽  
Vertical Wavelength ◽  
Broadband Emission ◽  
Filter Process ◽  
High Level ◽  
Observation Geometry ◽  
Horizontal Wavelength ◽  
Wavelength Distribution

Abstract. This paper describes a comprehensive observational filter for satellite infrared limb sounding of gravity waves. The filter considers instrument visibility and observation geometry with a high level of accuracy. It contains four main processes: visibility filter, projection of the wavelength on the tangent-point track, aliasing effect, and calculation of the observed vertical wavelength. The observation geometries of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and HIRDLS (High Resolution Dynamics Limb Sounder) are mimicked. Gravity waves (GWs) simulated by coupling a convective GW source (CGWS) scheme and the gravity wave regional or global ray tracer (GROGRAT) are used as an example for applying the observational filter. Simulated spectra in terms of horizontal and vertical wave numbers (wavelengths) of gravity wave momentum flux (GWMF) are analyzed under the influence of the filter. We find that the most important processes, which have significant influence on the spectrum are: visibility filter (for both SABER and HIRDLS observation geometries), aliasing for SABER and projection on tangent-point track for HIRDLS. The vertical wavelength distribution is mainly affected by the retrieval as part of the "visibility filter" process. In addition, the short-horizontal-scale spectrum may be projected for some cases into a longer horizontal wavelength interval which originally was not populated. The filter largely reduces GWMF values of very short horizontal wavelength waves. The implications for interpreting observed data are discussed.

scholarly journals Simultaneous lidar observations of temperatures and waves in the polar middle atmosphere on both sides of the Scandinavian mountains: a case study on 19/20 January 2003

2004 ◽  
Vol 4 (1) ◽  
pp. 969-989 ◽  
Author(s):  
U. Blum ◽  
K. H. Fricke ◽  
G. Baumgarten ◽  
A. Schöch
Keyword(s):  
Gravity Waves ◽  
Middle Atmosphere ◽  
Temperature Structure ◽  
Vertical Wavelength ◽  
Mountain Ridge ◽  
Induced Gravity ◽  
Simultaneous Measurements ◽  
Wave Patterns ◽  
Atmospheric Gravity

Abstract. Atmospheric gravity waves have been the subject of intense research for several decades because of their extensive effects on the atmospheric circulation and the temperature structure. The U. Bonn lidar at the Esrange and the ALOMAR RMR lidar at the Andøya Rocket Range are located in northern Scandinavia 250 km apart on either side of the Scandinavian mountain ridge. During January and February 2003 both lidar systems conducted measurements and retrieved atmospheric temperatures. On 19/20 January 2003 simultaneous measurements for more than 7 h were possible. Although during most of the campaign time the atmosphere was not transparent for the propagation of orographically induced gravity waves, they could propagate and were observed at both lidar stations during these simultaneous measurements. The wave patterns at ALOMAR show a random distribution with time whereas at the Esrange a persistency in the wave patterns is observable. This persistency can also be found in the distribution of the most powerful vertical wavelengths. The mode values are both at about 5 km vertical wavelength, however the distributions are quite different, narrow at the Esrange containing values from λz=2–6 km and broad at ALOMAR, covering λz=1–12 km vertical wavelength. At both stations the waves deposit energy in the atmosphere with increasing altitude, which leads to a decrease of the observed gravity wave potential energy density with altitude. These measurements show unambigiously orographically induced gravity waves on both sides of the mountains as well as a clear difference of the characteristics of these waves, which might be caused by different excitation and propagation conditions on either side of the Scandinavian mountain ridge.

scholarly journals Derivation of gravity wave intrinsic parameters and vertical wavelength using a single scanning OH(3-1) airglow spectrometer

2018 ◽  
Vol 11 (5) ◽  
pp. 2937-2947 ◽  
Author(s):  
Sabine Wüst ◽  
Thomas Offenwanger ◽  
Carsten Schmidt ◽  
Michael Bittner ◽  
Christoph Jacobi ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Spatial Information ◽  
Rotational Transition ◽  
Horizontal Wind ◽  
Vertical Temperature ◽  
Vertical Wavelength ◽  
Broadband Emission ◽  
Wind Measurements ◽  
First Time

Abstract. For the first time, we present an approach to derive zonal, meridional, and vertical wavelengths as well as periods of gravity waves based on only one OH* spectrometer, addressing one vibrational-rotational transition. Knowledge of these parameters is a precondition for the calculation of further information, such as the wave group velocity vector. OH(3-1) spectrometer measurements allow the analysis of gravity wave ground-based periods but spatial information cannot necessarily be deduced. We use a scanning spectrometer and harmonic analysis to derive horizontal wavelengths at the mesopause altitude above Oberpfaffenhofen (48.09∘ N, 11.28∘ E), Germany for 22 nights in 2015. Based on the approximation of the dispersion relation for gravity waves of low and medium frequencies and additional horizontal wind information, we calculate vertical wavelengths. The mesopause wind measurements nearest to Oberpfaffenhofen are conducted at Collm (51.30∘ N, 13.02∘ E), Germany, ca. 380 km northeast of Oberpfaffenhofen, by a meteor radar. In order to compare our results, vertical temperature profiles of TIMED-SABER (thermosphere ionosphere mesosphere energetics dynamics, sounding of the atmosphere using broadband emission radiometry) overpasses are analysed with respect to the dominating vertical wavelength.

Effect of viscosity on gravity waves and the upper boundary condition

1967 ◽  
Vol 29 (2) ◽  
pp. 209-231 ◽  
Author(s):  
Michael Yanowitch
Keyword(s):  
Gravity Waves ◽  
Dimensionless Parameter ◽  
Radiation Condition ◽  
Viscosity Coefficient ◽  
Vertical Wavelength ◽  
Reflected Wave ◽  
Linearized Problem ◽  
Dimensional Gravity ◽  
Density Scale ◽  
Upper Boundary

The linearized problem of two-dimensional gravity waves in a viscous incompressible stratified fluid occupying the upper half-space z > 0 is investigated. It is assumed that the dynamic viscosity coefficient μ is constant and that the density distribution ρ(z) is exponential. This leads to a fourth-order differential equation in the z co-ordinate, the coefficients of which depend on ρ(z) and on a dimensionless parameter ε which is proportional to μ/σ, σ being the frequency of the oscillation. The problem is solved for small ε. It is found that there is a region in which the solutions behave like certain solutions of the inviscid problem (with ε = 0). However, when the solutions of the inviscid problem are wave-like in z, they do not satisfy the radiation condition. This is because the viscosity, in addition to damping the motion for large z, reflects waves. The appropriate solution of the inviscid problem consists, therefore, of an incident and a reflected wave. As μ → 0, the ratio of the amplitudes of the reflected and the incident wave approaches exp (− 2π2H/Λ), where Λ is the vertical wavelength, and H the density scale height. The solution, however, does not have a limit since the reflecting layer shifts, altering the phase of the reflected wave. The results of the analysis are supplemented by a number of numerically computed solutions, which are then used to discuss the validity of the linearization.

scholarly journals A comprehensive observational filter for satellite infrared limb sounding of gravity waves

2015 ◽  
Vol 8 (3) ◽  
pp. 1491-1517 ◽  
Author(s):  
Q. T. Trinh ◽  
S. Kalisch ◽  
P. Preusse ◽  
H.-Y. Chun ◽  
S. D. Eckermann ◽  
...  
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Tangent Point ◽  
Vertical Wavelength ◽  
Broadband Emission ◽  
Filter Process ◽  
High Level ◽  
Observation Geometry ◽  
Horizontal Wavelength ◽  
Wavelength Distribution

Abstract. This paper describes a comprehensive observational filter for satellite infrared limb sounding of gravity waves. The filter considers instrument visibility and observation geometry with a high level of accuracy. It contains four main processes: visibility filter, projection of the wavelength on the tangent-point track, aliasing effect, and calculation of the observed vertical wavelength. The observation geometries of the SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) and HIRDLS (High Resolution Dynamics Limb Sounder) are mimicked. Gravity waves (GWs) simulated by coupling a convective GW source (CGWS) scheme and the gravity wave regional or global ray tracer (GROGRAT) are used as an example for applying the observational filter. Simulated spectra in terms of horizontal and vertical wave numbers (wavelengths) of gravity wave momentum flux (GWMF) are analyzed under the influence of the filter. We find that the most important processes, which have significant influence on the spectrum are the visibility filter (for both SABER and HIRDLS observation geometries) and aliasing for SABER and projection on tangent-point track for HIRDLS. The vertical wavelength distribution is mainly affected by the retrieval as part of the "visibility filter" process. In addition, the short-horizontal-scale spectrum may be projected for some cases into a longer horizontal wavelength interval which originally was not populated. The filter largely reduces GWMF values of very short horizontal wavelength waves. The implications for interpreting observed data are discussed.

scholarly journals Characteristics of gravity waves generated in a convective and a non-convective environment revealed from hourly radiosonde observation under CPEA-II campaign

2011 ◽  
Vol 29 (12) ◽  
pp. 2259-2276 ◽  
Author(s):  
S. K. Dhaka ◽  
R. Bhatnagar ◽  
Y. Shibagaki ◽  
H. Hashiguchi ◽  
S. Fukao ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Zonal Wind ◽  
Wind Shear ◽  
Radiosonde Data ◽  
Strong Wind ◽  
Mean Flow ◽  
Vertical Wavelength ◽  
Short Period ◽  
Radiosonde Observation ◽  
Wind Shears

Abstract. Analyses of hourly radiosonde data of temperature, wind, and relative humidity during four days (two with convection and two with no convection) as a part of an intensive observation period in CPEA-2 campaign over Koto Tabang (100.32° E, 0.20° S), Indonesia, are presented. Characteristics of gravity waves in terms of dominant wave frequencies at different heights and their vertical wavelengths are shown in the lower stratosphere during a convective and non-convective period. Gravity waves with periods ~10 h and ~4–5 h were found dominant near tropopause (a region of high stability) on all days of observation. Vertical propagation of gravity waves were seen modified near heights of the three identified strong wind shears (at ~16, 20, and 25 km heights) due to wave-mean flow interaction. Between 17 and 21 km heights, meridional wind fluctuations dominated over zonal wind, whereas from 22 to 30 km heights, wave fluctuations with periods ~3–5 h and ~8–10 h in zonal wind and temperature were highly associated, suggesting zonal orientation of wave propagation. Gravity waves from tropopause region to 30 km heights were analyzed. In general, vertical wavelength of 2–5 km dominated in all the mean-removed (~ weekly mean) wind and temperature hourly profiles. Computed vertical wavelength spectra are similar, in most of the cases, to the source spectra (1–16 km height) except that of zonal wind spectra, which is broad during active convection. Interestingly, during and after convection, gravity waves with short vertical wavelength (~2 km) and short period (~2–3 h) emerged, which were confined in the close vicinity of tropopause, and were not identified on non-convective days, suggesting convection to be the source for them. Some wave features near strong wind shear (at 25 km height) were also observed with short vertical wavelengths in both convective and non-convective days, suggesting wind shear to be the sole cause of generation and seemingly not associated with deep convection below. A drop in the temperature up to ~4–5 K (after removal of diurnal component) was observed at ~16 km height near a strong wind shear (~45–55 m s−1 km−1) during active period of convection.

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