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 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 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.

Coupling between Gravity Waves and Tropical Convection at Mesoscales

2011 ◽  
Vol 68 (11) ◽  
pp. 2582-2598 ◽  
Author(s):  
Todd P. Lane ◽  
Fuqing Zhang
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Model Simulation ◽  
Wave Mode ◽  
Life Cycles ◽  
Cloud System ◽  
Vertical Wavelength ◽  
Convective Systems ◽  
The Waves ◽  
Horizontal Wavelength

Abstract An idealized cloud-system-resolving model simulation is used to examine the coupling between a tropical cloud population and the mesoscale gravity waves that it generates. Spectral analyses of the cloud and gravity wave fields identify a clear signal of coupling between the clouds and a deep tropospheric gravity wave mode with a vertical wavelength that matches the depth of the convection, which is about two-thirds of the tropospheric depth. This vertical wavelength and the period of the waves, defined by a characteristic convective time scale, means that the horizontal wavelength is constrained through the dispersion relation. Indeed, the wave–convection coupling manifests at the appropriate wavelength, with the emergence of quasi-regular cloud-system spacing of order 100 km. It is shown that cloud systems at this spacing achieve a quasi-resonant state, at least for a few convective life cycles. Such regular spacing is a key component of cloud organization and is likely a contributor to the processes controlling the upscale growth of convective systems. Other gravity wave processes are also elucidated, including their apparent role in the maintenance of convective systems by providing a mechanism for renewed convective activity and system longevity.

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 Simulation of Inertia–Gravity Waves in a Poleward-Breaking Rossby Wave

2006 ◽  
Vol 63 (12) ◽  
pp. 3253-3276 ◽  
Author(s):  
Christoph Zülicke ◽  
Dieter Peters
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Mesoscale Model ◽  
Wave Packets ◽  
The Impact ◽  
Jet Streak ◽  
Horizontal Wavelength ◽  
Inertia Gravity Waves

Poleward-breaking Rossby waves often induce an upper-level jet streak over northern Europe. Dominant inertia–gravity wave packets are observed downstream of this jet. The physical processes of their generation and propagation, in such a configuration, are investigated with a mesoscale model. The study is focused on an observational campaign from 17 to 19 December 1999 over northern Germany. Different simulations with the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) have been performed. For a high-resolution process study, three domains were set up that encompass the evolution of Rossby waves and that of inertia–gravity waves. To minimize the impact of model damping, the horizontal and vertical resolution has been adjusted appropriately. With a novel statistical approach, the properties of inertia–gravity wave packets have been estimated. This method uses the horizontal divergence field and takes into account the spatial extension of a wave packet. It avoids the explicit treatment of the background field and works for arbitrary wavelength. Two classes of inertia–gravity waves were found: subsynoptic waves with a horizontal wavelength of about 500 km and mesoscale waves with a horizontal wavelength of about 200 km. The subsynoptic structures were also detected in radiosonde observations during this campaign. The similarity between simulated and observed wavelengths and amplitudes suggests that the simulations can be considered as near realistic. Spontaneous radiation from unbalanced flow is an important process of inertia–gravity wave generation. Synoptic-scale imbalances in the exit region of the upper-tropospheric jet streak were identified with the smoothed cross-stream Lagrangian Rossby number. In a number of simulations with different physics, it was found that the inertia–gravity wave activity was related to the tropospheric jet, orography, and moist convection. The upward propagation of inertia–gravity waves was favored during this event of a poleward-breaking Rossby wave. The presence of the polar vortex induced background winds exceeding the critical line. Consequently, the activity of inertia–gravity waves in the lower stratosphere increased by an order of magnitude during the case study. The successful simulation of the complex processes of generation and propagation showed the important role of poleward Rossby wave breaking for the appearance of inertia–gravity waves in the midlatitudes.

scholarly journals Gravity wave transmission diagram

2015 ◽  
Vol 33 (12) ◽  
pp. 1479-1484 ◽  
Author(s):  
Y. Tomikawa
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Phase Speed ◽  
Propagation Direction ◽  
Wave Transmission ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Wave Power ◽  
Power Spectral ◽  
Horizontal Wavelength

Abstract. A new method of obtaining power spectral distribution of gravity waves as a function of ground-based horizontal phase speed and propagation direction from airglow observations has recently been proposed. To explain gravity wave power spectrum anisotropy, a new gravity wave transmission diagram was developed in this study. Gravity wave transmissivity depends on the existence of critical and turning levels for waves that are determined by background horizontal wind distributions. Gravity wave transmission diagrams for different horizontal wavelengths in simple background horizontal winds with constant vertical shear indicate that the effects of the turning level reflection are significant and strongly dependent on the horizontal wavelength.

scholarly journals Seasonal Cycle of Gravity Wave Potential Energy Densities from Lidar and Satellite Observations at 54° and 69°N

2021 ◽  
Vol 78 (4) ◽  
pp. 1359-1386
Author(s):  
Irina Strelnikova ◽  
Marwa Almowafy ◽  
Gerd Baumgarten ◽  
Kathrin Baumgarten ◽  
Manfred Ern ◽  
...  
Keyword(s):  
Potential Energy ◽  
Gravity Wave ◽  
Seasonal Cycle ◽  
Middle Atmosphere ◽  
Reanalysis Data ◽  
Vertical Wavelength ◽  
Wave Potential ◽  
Broadband Emission ◽  
The Difference ◽  
Lidar Observations

AbstractWe present gravity wave climatologies based on 7 years (2012–18) of lidar and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperatures and reanalysis data at 54° and 69°N in the altitude range 30–70 km. We use 9452 (5044) h of lidar observations at Kühlungsborn [Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR)]. Filtering according to vertical wavelength (λz < 15 km) or period (τ < 8 h) is applied. Gravity wave potential energy densities (GWPED) per unit volume (EpV) and per unit mass (Epm) are derived. GWPED from reanalysis are smaller compared to lidar. The difference increases with altitude in winter and reaches almost two orders of magnitude around 70 km. A seasonal cycle of EpV with maximum values in winter is present at both stations in nearly all lidar and SABER measurements and in reanalysis data. For SABER and for lidar (with λ < 15 km) the winter/summer ratios are a factor of ~2–4, but are significantly smaller for lidar with τ < 8 h. The winter/summer ratios are nearly identical at both stations and are significantly larger for Epm compared to EpV. Lidar and SABER observations show that EpV is larger by a factor of ~2 at Kühlungsborn compared to ALOMAR, independent of season and altitude. Comparison with mean background winds shows that simple scenarios regarding GW filtering, etc., cannot explain the Kühlungsborn–ALOMAR differences. The value of EpV decreases with altitude in nearly all cases. Corresponding EpV-scale heights from lidar are generally larger in winter compared to summer. Above ~55 km, EpV in summer is almost constant with altitude at both stations. The winter–summer difference of EpV scale heights is much smaller or absent in SABER and in reanalysis data.

Gravity wave intermittency derived from HIRDLS and SABER satellite limb soundings

2020 ◽  
Author(s):  
Manfred Ern ◽  
Peter Preusse ◽  
Martin Riese
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Climate Models ◽  
Spatial Scales ◽  
Wave Activity ◽  
Background Flow ◽  
Wave Source ◽  
Gini Coefficients ◽  
Broadband Emission ◽  
Wave Distribution

&lt;p&gt;Sources of atmospheric gravity waves are mostly located in the troposphere and the lower stratosphere. Gravity waves propagate away from their sources, re-distribute energy and momentum in the atmosphere, and exert drag on the atmospheric background flow where they dissipate. Therefore they are important drivers of the atmospheric circulation. In climate models, their effect on the background circulation is usually parameterized because of their relatively short horizontal and vertical wavelengths that are of the order of 10-1000km and 1-100km, respectively. Gravity wave parametrizations are very simplified. For example, they often neglect the fact that gravity wave source processes and gravity wave propagation conditions can vary on short temporal and spatial scales. Therefore the global distribution of gravity wave activity is very intermittent, which has also important consequences where gravity waves dissipate and exert drag on the background flow, and which should be accounted for in parametrizations.&lt;br&gt;For guiding models, global observations of the gravity wave distribution and its intermittency are needed. We derive gravity wave potential energies and absolute momentum fluxes from observations of the High Resolution Dynamics Limb Sounder (HIRDLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instruments. As a measure of intermittency, we calculate global distributions of Gini coefficients. We find that our results are qualitatively in good agreement with previous findings from satellite, and similar in magnitude to intermittency obtained from previous superpressure balloon campaigns. In the stratosphere, strongest intermittency is found over orographic gravity wave sources, followed by gravity wave activity in the polar night jets. Intermittency in the tropical stratosphere is weakest. However, in the tropical upper mesosphere intermittency is increased, which is likely caused by the modulation of the gravity wave distribution by tides.&lt;/p&gt;

Removing spurious inertial instability signals from gravity wave temperature perturbations using spectral filtering methods

2020 ◽  
Author(s):  
Cornelia Strube ◽  
Manfred Ern ◽  
Peter Preusse ◽  
Martin Riese
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Wave Spectrum ◽  
Vertical Direction ◽  
Dynamic Processes ◽  
Small Scale ◽  
Vertical Wavelength ◽  
Background Removal ◽  
Zonal Wavenumber ◽  
Inertial Instability

&lt;p&gt;Gravity waves are important drivers of dynamic processes in the middle atmosphere, but not the only process that could lead to small-scale perturbations. To analyse atmospheric data for gravity wave signals, gravity wave perturbations have to be separated from atmospheric variability caused by other dynamic processes. Common methods to separate small-scale gravity wave signals from a large-scale background comprise filtering methods in either the horizontal or vertical wavelength domain. Recently, studies showed that vertical wavelengths filtering can mistake other wave-like perturbations, such as inertial instability effects, for gravity wave perturbations.&lt;/p&gt;&lt;p&gt;We use artificial inertial instability perturbations, global model data and satellite observations to assess different spectral background removal approaches on their ability to separate gravity waves and inertial instabilities. Therefore, we investigate a horizontal background removal, applying a zonal wavenumber filter with additional smoothing of the spectral components in meridional and vertical direction, a sophisticated filter based on 2D time-longitude spectral analysis (see Ern et al., 2011) and a vertical wavelength Butterworth filter.&lt;/p&gt;&lt;p&gt;We analyse the results for critical thresholds of the vertical wavelength and zonal wavenumber, respectively. Vertical filtering has to remove a part of the gravity wave spectrum in order to eliminate inertial instability remnants from the perturbations. Horizontal filtering, however, separates the data at scales far beyond the expected gravity wave spectrum for the case we investigated. Furthermore, we show that it is possible to effectively separate inertial instabilities perturbations from gravity waves perturbations for infrared limb-sounding satellite profiles using a cutoff zonal wavenumber of 6.&lt;/p&gt;

scholarly journals Global distributions of overlapping gravity waves in HIRDLS data

2015 ◽  
Vol 15 (14) ◽  
pp. 8459-8477 ◽  
Author(s):  
C. J. Wright ◽  
S. M. Osprey ◽  
J. C. Gille
Keyword(s):  
Gravity Wave ◽  
Gravity Waves ◽  
Spectral Characteristics ◽  
Small Scale ◽  
Spectral Form ◽  
Broadband Emission ◽  
Temporal And Spatial Variability ◽  
Abstract Data ◽  
Temporal And Spatial ◽  
Wave Phenomena

Abstract. Data from the High Resolution Dynamics Limb Sounder (HIRDLS) instrument on NASA's Aura satellite are used to investigate the relative numerical variability of observed gravity wave packets as a function of both horizontal and vertical wavenumber, with support from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on TIMED. We see that these distributions are dominated by large vertical and small horizontal wavenumbers, and have a similar spectral form at all heights and latitudes, albeit with important differences. By dividing our observed wavenumber distribution into particular subspecies of waves, we demonstrate that these distributions exhibit significant temporal and spatial variability, and that small-scale variability associated with particular geophysical phenomena such as the monsoon arises due to variations in specific parts of the observed spectrum. We further show that the well-known Andes/Antarctic Peninsula gravity wave hotspot during southern winter, home to some of the largest wave fluxes on the planet, is made up of relatively few waves, but with a significantly increased flux per wave due to their spectral characteristics. These results have implications for the modelling of gravity wave phenomena.

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