Gravity wave amplitudes and momentum fluxes inferred from OH airglow intensities and meteor radar winds during SpreadFEx

Abstract. We show in this report the momentum flux content input in the mesosphere due to relatively fast and small scale gravity waves (GWs) observed through OH airglow images. The acquisition of OH NIR images was carried out in Brazil at Brasilia (14.8° S, 47.6° W) and Cariri (7.4° S, 36.5° W) from September 2005 to November 2005 during the SpreadFEx Campaign. Horizontal wind information from meteor radar was available in Cariri only. Our findings showed strong wave activity in both sites, mainly in Cariri. High wave directionality was also observed in both sites during SpreadFEx, which have been observed by other investigators using different analysis' techniques and different types of data during the campaign. We discuss also the possibility of plasma bubble seeding by gravity waves presenting spatial and temporal scales estimated with our novel analysis technique during the SpreadFEx campaign.

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Mesospheric gravity wave activity estimated via airglow imagery, multistatic meteor radar, and SABER data taken during the SIMONe–2018 campaign

10.5194/acp-2020-896 ◽

2020 ◽

Author(s):

Fabio Vargas ◽

Jorge L. Chau ◽

Harikrishnan Charuvil Asokan ◽

Michael Gerding

Keyword(s):

Gravity Waves ◽

Momentum Flux ◽

Large Scale ◽

Lower Thermosphere ◽

Small Scale ◽

Meteor Radar ◽

Mean Flow ◽

Horizontal Scale ◽

Momentum Fluxes ◽

Mesosphere And Lower Thermosphere

Abstract. We describe in this study the analysis of small and large horizontal scale gravity waves from datasets composed of images from multiple mesospheric nightglow emissions as well as multistatic specular meteor radar (MSMR) winds collected in early November 2018, during the SIMONe–2018 campaign. These ground-based measurements are supported by temperature and neutral density profiles from TIMED/SABER satellite in orbits near Kühlungsborn, northern Germany (54.1° N, 11.8° E). The scientific goals here include the characterization of gravity waves and their interaction with the mean flow in the mesosphere and lower thermosphere and their relationship to dynamical conditions in the lower and upper atmosphere. We obtain intrinsic parameters of small and large horizontal scale gravity waves and characterize their impact in the mesosphere region via momentum flux and flux divergence estimations. We have verified that a small percent of the detected wave events are responsible for most of the momentum flux measured during the campaign from oscillations seen in the airglow brightness and MSMR winds. From the analysis of small-scale gravity waves in airglow images, we have found wave momentum fluxes ranging from 0.38 to 24.74 m2/s2 (0.88 ± 0.73 m2/s2 on average), with a total of 586.96 m2/s2 (sum over all 362 detected waves). However, small horizontal scale waves with flux > 3 m2/s2 (11 % of the events) transport 50 % of the total measured flux. Likewise, wave events having flux > 10 m2/s2 (2 % of the events) transport 20 % of the total flux. The examination of two large-scale waves seen simultaneously in airglow keograms and MSMR winds revealed relative amplitudes > 35 %, which translates into momentum fluxes of 21.2–29.6 m/s. In terms of gravity wave–mean flow interactions, these high momentum flux waves could cause decelerations of 22–41 m/s/day (small-scale waves) and 38–43 m/s/day (large-scale waves) if breaking or dissipating within short distances in the mesosphere and lower thermosphere region. The dominant large-scale waves might be the result of secondary gravity excited from imbalanced flow in the stratosphere caused by primary wave breaking.

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Frequency spectra of horizontal winds in the mesosphere and lower thermosphere region from multistatic specular meteor radar observations during the SIMONe 2018 campaign

10.21203/rs.3.rs-697043/v1 ◽

2021 ◽

Author(s):

Harikrishnan Charuvil Asokan ◽

Jorge L Chau ◽

Raffaele Marino ◽

Juha Vierinen ◽

Fabio Vargas ◽

...

Keyword(s):

Gravity Waves ◽

Spread Spectrum ◽

Lower Thermosphere ◽

Geographic Area ◽

Horizontal Wind ◽

Small Scale ◽

Meteor Radar ◽

Frequency Spectra ◽

Mesosphere And Lower Thermosphere ◽

Field Correlation

Abstract In recent years, multistatic specular meteor radars (SMRs) have been introduced to study the Mesosphere and Lower Thermosphere (MLT) dynamics with increasing spatial and temporal resolution. In this paper, frequency spectra of MLT horizontal winds are explored through observations from a campaign using the SIMONe (Spread-spectrum Interferometric Multistatic meteor radar Observing Network) approach conducted in northern Germany in 2018 (hereafter SIMONe 2018). The seven-day SIMONe 2018 comprised of fourteen multistatic SMR links and allows to build a substantial database of specular meteor trail events, collecting more than one hundred thousand detections per day within a geographic area of $\sim $ 500 km $\times$ 500 km. We have implemented two methods to obtain the frequency spectra of the horizontal wind components: (1) Mean Wind Estimation (MWE) and (2) Wind field Correlation Function Inversion (WCFI), which utilizes the mean and the covariances of the line of sight velocities, respectively. Monte Carlo simulations of a gravity wave spectral model were implemented to validate and compare both methods. The simulation analyses suggest that the WCFI helps to capture the energy of smaller-scale wind fluctuations than those capture with MWE. Characterization of the spectral slope of the horizontal wind at different MLT altitudes has been conducted on the SIMONe 2018, and it provides evidence that gravity waves with periods smaller than seven hours and greater than two hours dominate with horizontal structures significantly larger than 500 km. These waves might be associated with secondary gravity waves during this observational campaign. In the future, these analyses can be extended to understand the significance of small-scale fluctuations in the MLT, which were not possible with conventional MWE methods.

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Small-scale gravity waves in ER-2 MMS/MTP wind and temperature measurements during CRYSTAL-FACE

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-5-11377-2005 ◽

2005 ◽

Vol 5 (6) ◽

pp. 11377-11412

Author(s):

L. Wang ◽

M. J. Alexander ◽

T. P. Bui ◽

M. J. Mahoney

Keyword(s):

Gravity Waves ◽

Temperature Measurements ◽

Small Scale ◽

Maximum Magnitude ◽

Horizontal Scale ◽

Crystal Face ◽

Cloud Models ◽

S Transform ◽

Momentum Fluxes ◽

The Cross

Abstract. ER-2 MMS and MTP wind and temperature measurements during the CRYSTAL-FACE campaign in July 2002 were analyzed to retrieve information on small scale gravity waves (GWs) at aircraft's flight level. For a given flight segment, the S-transform was used to search for and identify small horizontal scale GW events, and to estimate the apparent horizontal wavelengths of the events. The horizontal propagation directions of the events were determined using the Stokes parameters method combined with the cross S-transform analysis. The MTP temperature gradient method was used to determine the vertical wavelengths of the events. GW momentum fluxes were calculated from the cross S-transform. Other wave parameters such as intrinsic frequencies were calculated using the GW dispersion relation. More than 100 GW events were identified. They were generally short horizontal scale and high frequency waves with λz of ~5 km and λh generally shorter than 20 km. Their intrinsic propagation directions were predominantly toward the east, whereas their ground-based propagation directions were primarily toward the west. Among the events, ~20% of them had very short horizontal wavelength (<10 km), very high intrinsic frequency (ω/N≥0.8), and relatively small momentum fluxes, and thus they were likely trapped in the lower stratosphere. The averaged magnitude of vertical flux of horizontal momentum was ~0.026 kg m−1 s−2, and the maximum magnitude was ~0.13 kg m−1 s−2. Using the estimated GW parameters and the background winds and stabilities from the NCAR/NCEP reanalysis data, we were able to trace the sources of the events using a simple reverse ray-tracing. More than 70% of the events were traced back to convective sources in the troposphere, and the sources were generally located upstream to the events. Finally, a probability density function of GW cooling rates was obtained in this study, which may be used in cirrus cloud models.

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Consistency between Fourier transform and small-volume few-wave decomposition for spectral and spatial variability of gravity waves above a typhoon

Atmospheric Measurement Techniques ◽

10.5194/amt-5-1637-2012 ◽

2012 ◽

Vol 5 (7) ◽

pp. 1637-1651 ◽

Cited By ~ 23

Author(s):

C. I. Lehmann ◽

Y.-H. Kim ◽

P. Preusse ◽

H.-Y. Chun ◽

M. Ern ◽

...

Keyword(s):

Fourier Transform ◽

Momentum Flux ◽

Wide Spectrum ◽

Three Dimensional ◽

Phase Speed ◽

Analysis Technique ◽

Momentum Fluxes ◽

Different Types ◽

Wave Decomposition ◽

First Time

Abstract. Convective gravity wave (GW) sources are spatially localized and emit at the same time waves with a wide spectrum of phase speeds. Any wave analysis therefore compromises between spectral and spatial resolution. Future satellite borne limb imagers will for a first time provide real 3-D volumes of observations. These volumes will be however limited which will impose further constraints on the analysis technique. In this study a three dimensional few-wave approach fitting sinusoidal waves to limited 3-D volumes is introduced. The method is applied to simulated GWs above typhoon Ewiniar and GW momentum flux is estimated from temperature fluctuations. Phase speed spectra as well as average profiles of positive, negative and net momentum fluxes are compared to momentum flux estimated by Fourier transform as well as spatial averaging of wind fluctuations. The results agree within 10–20%. The few-wave method can also reveal the spatial orientation of the GWs with respect to the source. The relevance of the results for different types of measurements as well as its applicability to model data is discussed.

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Small-scale gravity waves in ER-2 MMS/MTP wind and temperature measurements during CRYSTAL-FACE

Atmospheric Chemistry and Physics ◽

10.5194/acp-6-1091-2006 ◽

2006 ◽

Vol 6 (4) ◽

pp. 1091-1104 ◽

Cited By ~ 18

Author(s):

L. Wang ◽

M. J. Alexander ◽

T. B. Bui ◽

M. J. Mahoney

Keyword(s):

Gravity Waves ◽

Temperature Measurements ◽

Small Scale ◽

Parameter Method ◽

Crystal Face ◽

Cloud Models ◽

S Transform ◽

Momentum Fluxes ◽

The Cross ◽

Horizontal Wavelength

Abstract. Lower stratospheric wind and temperature measurements made from NASA's high-altitude ER-2 research aircraft during the CRYSTAL-FACE campaign in July 2002 were analyzed to retrieve information on small scale gravity waves (GWs) at the aircraft's flight level (typically ~20 km altitude). For a given flight segment, the S-transform (a Gaussian wavelet transform) was used to search for and identify small horizontal scale GW events, and to estimate their apparent horizontal wavelengths. The horizontal propagation directions of the events were determined using the Stokes parameter method combined with the cross S-transform analysis. The vertical temperature gradient was used to determine the vertical wavelengths of the events. GW momentum fluxes were calculated from the cross S-transform. Other wave parameters such as intrinsic frequencies were calculated using the GW dispersion relation. More than 100GW events were identified. They were generally high frequency waves with vertical wavelength of ~5 km and horizontal wavelength generally shorter than 20 km. Their intrinsic propagation directions were predominantly toward the east, whereas their ground-based propagation directions were primarily toward the west. Among the events, ~20% of them had very short horizontal wavelength, very high intrinsic frequency, and relatively small momentum fluxes, and thus they were likely trapped in the lower stratosphere. Using the estimated GW parameters and the background winds and stabilities from the NCAR/NCEP reanalysis data, we were able to trace the sources of the events using a simple reverse ray-tracing. More than 70% of the events were traced back to convective sources in the troposphere, and the sources were generally located upstream of the locations of the events observed at the aircraft level. Finally, a probability density function of the reversible cooling rate due to GWs was obtained in this study, which may be useful for cirrus cloud models.

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Consistency between Fourier transform and small-volume few-wave decomposition for spectral and spatial variability of gravity waves above a typhoon

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-5-1763-2012 ◽

2012 ◽

Vol 5 (1) ◽

pp. 1763-1793

Author(s):

C. I. Lehmann ◽

Y.-H. Kim ◽

P. Preusse ◽

H.-Y. Chun ◽

M. Ern ◽

...

Keyword(s):

Fourier Transform ◽

Momentum Flux ◽

Wide Spectrum ◽

Three Dimensional ◽

Phase Speed ◽

Analysis Technique ◽

Momentum Fluxes ◽

Different Types ◽

Wave Decomposition ◽

First Time

Abstract. Convective gravity wave (GW) sources are spatially localized and emit at the same time waves with a wide spectrum of phase speeds. Any wave analysis therefore compromises between spectral and spatial resolution. Future satellite borne limb imagers will for a first time provide real 3d volumes of observations. These volumes will be however limited which will impose further constraints on the analysis technique. In this study a three dimensional few-wave appoach fitting sinusoidal waves to limited 3-D volumes is introduced. The method is applied to simulated GWs above typhoon Ewiniar and GW momentum flux is estimated from temperature fluctuations. Phase speed spectra as well as average profiles of positive, negative and net momentum fluxes are compared to momentum flux estimated by Fourier transform as well as spatial averaging of wind fluctuations. The results agree within 10–20%. The few-wave method can also reveal the spatial orientation of the GWs with respect to the source. The relevance of the results for different types of measurements as well as its applicability to model data is discussed.

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Revisiting the Quasi Biennial Oscillation as Seen in ERA5. Part II: Evaluation of Waves and Wave Forcing

Journal of the Atmospheric Sciences ◽

10.1175/jas-d-20-0249.1 ◽

2020 ◽

Author(s):

Hamid A. Pahlavan ◽

John M. Wallace ◽

Qiang Fu ◽

George N. Kiladis

Keyword(s):

Gravity Waves ◽

Rossby Waves ◽

Zonal Flow ◽

Small Scale ◽

Tropical Region ◽

Quasi Biennial Oscillation ◽

Wave Forcing ◽

Different Types ◽

Zonal Momentum ◽

Biennial Oscillation

AbstractThis paper describes stratospheric waves in ERA5 reanalysis and evaluates the contributions of different types of waves to the driving of the quasi-biennial oscillation (QBO). Because of its higher spatial resolution compared to its predecessors, ERA5 is capable of resolving a broader spectrum of waves. It is shown that the resolved waves contribute to both eastward and westward accelerations near the equator, mainly by the way of the vertical flux of zonal momentum. The eastward accelerations by the resolved waves are mainly due to Kelvin waves and small-scale gravity (SSG) waves with zonal wavelengths smaller than 2000 km, whereas the westward accelerations are forced mainly by SSG waves, with smaller contributions from inertio-gravity and mixed-Rossby-gravity waves. Extratropical Rossby waves disperse upward and equatorward into the tropical region and impart a westward acceleration to the zonal flow. They appear to be responsible for at least some of the irregularities in the QBO cycle.

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Diurnal Characteristics of Gravity Waves over the Tibetan Plateau in 2015 Summer Using 10-km Downscaled Simulations from WRF-EnKF Regional Reanalysis

Atmosphere ◽

10.3390/atmos11060631 ◽

2020 ◽

Vol 11 (6) ◽

pp. 631

Author(s):

Tingting Qian ◽

Fuqing Zhang ◽

Junhong Wei ◽

Jie He ◽

Yinghui Lu

Keyword(s):

Tibetan Plateau ◽

Gravity Waves ◽

Power Spectra ◽

Reanalysis Data ◽

Small Scale ◽

The Tibetan Plateau ◽

Wave Source ◽

Momentum Fluxes ◽

Regional Reanalysis ◽

Meso Scale

Diurnal variations of gravity waves over the Tibetan Plateau (TP) in summer 2015 were investigated based on high-resolution downscaled simulations from WRF-EnKF (Weather Research and Forecasting model and an ensemble Kalman filter) regional reanalysis data with particular emphasis on wave source, wave momentum fluxes and wave energies. Strong diurnal precipitations, which mainly happen along the south slope of the TP, tend to excite upward-propagating gravity waves. The spatial and temporal distributions of the momentum fluxes of small-scale (10–200 km) and meso-scale (200–500 km) gravity waves agree well with the diurnal precipitation distributions. The power spectra of momentum fluxes also show that the small- and meso-scale atmospheric processes become important during the period of the strongest rainfall. Eastward momentum fluxes and northward momentum fluxes are dominant. Wave energies are described in terms of kinetic energy (KE), potential energy (PE) and vertical fluctuation energy (VE). The diurnal variation and spatial distribution of VE in the lower stratosphere correspond to the diurnal rainfall in the troposphere.

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Modeling study of mesospheric planetary waves: genesis and characteristics

Annales Geophysicae ◽

10.5194/angeo-22-1885-2004 ◽

2004 ◽

Vol 22 (6) ◽

pp. 1885-1902 ◽

Cited By ~ 11

Author(s):

H. G. Mayr ◽

J. G. Mengel ◽

E. R. Talaat ◽

H. S. Porter ◽

K. L. Chan

Keyword(s):

Heat Source ◽

Gravity Waves ◽

Zonal Flow ◽

Planetary Waves ◽

Wave Number ◽

Horizontal Wind ◽

Small Scale ◽

Wind Fields ◽

Zonal Jets ◽

Nonmigrating Tides

Abstract. The Numerical Spectral Model (NSM) extends from the ground into the thermosphere and incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GWs). In the present version of the model we account for a tropospheric heat source in the zonal mean (m=0), which reproduces qualitatively the observed zonal jets near the tropopause and the accompanying reversal in the latitudinal temperature variations. In the study presented here, we discuss the planetary waves (PWs) that are solely generated internally, i.e. without the explicit excitation sources related to tropospheric convection or topography. Our analysis shows that PWs are not produced when the zonally averaged heat source into the atmosphere is artificially suppressed, and that the PWs are generally weaker when the tropospheric source is not applied. Instabilities associated with the zonal mean temperature, pressure and wind fields, which still need to be explored, are exciting PWs that have amplitudes in the mesosphere comparable to those observed. Three classes of PWs are generated in the NSM. (1) Rossby type PWs, which slowly propagate westward relative to the mean zonal flow, are carried by the winds so that they appear (from the ground) to propagate, respectively, eastward and westward in the winter and summer hemispheres below 80km. Depending on the zonal wave number and magnitudes of the zonal winds, and under the influence of the equatorial oscillations, these PWs typically have periods between 2 and 20 days. Their horizontal wind amplitudes can exceed 40 m/s in the lower mesosphere. (2) Rossby-gravity waves, which propagate westward at low latitudes and have periods around 2 days for zonal wave numbers m=2 to 4. (3) Eastward propagating equatorial Kelvin waves, which are generated in the upper mesosphere with periods between 1 and 3 days depending on m. A survey of the PWs reveals that the largest wind amplitudes tend to occur below 80km in the winter hemisphere; but above that altitude the amplitudes are larger in the summer hemisphere where the winds can approach 50m/s. This pattern in the seasonal variations also appears in the baroclinity of the zonal mean (m=0). The nonmigrating tides in the mesosphere are significantly larger for the model with the tropospheric heat source, in which PWs are apparently generated by the instabilities that arise around the tropopause.

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Mesospheric gravity wave activity estimated via airglow imagery, multistatic meteor radar, and SABER data taken during the SIMONe–2018 campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-21-13631-2021 ◽

2021 ◽

Vol 21 (17) ◽

pp. 13631-13654

Author(s):

Fabio Vargas ◽

Jorge L. Chau ◽

Harikrishnan Charuvil Asokan ◽

Michael Gerding

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Momentum Flux ◽

Large Scale ◽

Lower Thermosphere ◽

Small Scale ◽

Meteor Radar ◽

Mean Flow ◽

Flux Divergence ◽

Mesosphere And Lower Thermosphere

Abstract. We describe in this study the analysis of small and large horizontal-scale gravity waves from datasets composed of images from multiple mesospheric airglow emissions as well as multistatic specular meteor radar (MSMR) winds collected in early November 2018, during the SIMONe–2018 (Spread-spectrum Interferometric Multi-static meteor radar Observing Network) campaign. These ground-based measurements are supported by temperature and neutral density profiles from TIMED/SABER (Thermosphere, Ionosphere, Mesosphere Energetics and Dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry) satellite in orbits near Kühlungsborn, northern Germany (54.1∘ N, 11.8∘ E). The scientific goals here include the characterization of gravity waves and their interaction with the mean flow in the mesosphere and lower thermosphere and their relationship to dynamical conditions in the lower and upper atmosphere. We have obtained intrinsic parameters of small- and large-scale gravity waves and characterized their impact in the mesosphere via momentum flux (FM) and momentum flux divergence (FD) estimations. We have verified that a small percentage of the detected wave events is responsible for most of FM measured during the campaign from oscillations seen in the airglow brightness and MSMR winds taken over 45 h during four nights of clear-sky observations. From the analysis of small-scale gravity waves (λh < 725 km) seen in airglow images, we have found FM ranging from 0.04–24.74 m2 s−2 (1.62 ± 2.70 m2 s−2 on average). However, small-scale waves with FM > 3 m2 s−2 (11 % of the events) transport 50 % of the total measured FM. Likewise, wave events of FM > 10 m2 s−2 (2 % of the events) transport 20 % of the total. The examination of large-scale waves (λh > 725 km) seen simultaneously in airglow keograms and MSMR winds revealed amplitudes > 35 %, which translates into FM = 21.2–29.6 m2 s−2. In terms of gravity-wave–mean-flow interactions, these large FM waves could cause decelerations of FD = 22–41 m s−1 d−1 (small-scale waves) and FD = 38–43 m s−1 d−1 (large-scale waves) if breaking or dissipating within short distances in the mesosphere and lower thermosphere region.

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