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Stephen D. Eckermann - One of the best experts on this subject based on the ideXlab platform.
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atmospheric conditions during the deep propagating Gravity Wave experiment deepWave
Monthly Weather Review, 2017Co-Authors: Sonja Gisinger, Stephen D. Eckermann, Lars Hoffmann, Christopher G Kruse, James D Doyle, Andreas Dornbrack, Vivien Matthias, Benedikt Ehard, Bernd Kaifler, Markus RappAbstract:AbstractThis paper describes the results of a comprehensive analysis of the atmospheric conditions during the Deep Propagating Gravity Wave Experiment (DEEPWave) campaign in austral winter 2014. Different datasets and diagnostics are combined to characterize the background atmosphere from the troposphere to the upper mesosphere. How weather regimes and the atmospheric state compare to climatological conditions is reported upon and how they relate to the airborne and ground-based Gravity Wave observations is also explored. Key results of this study are the dominance of tropospheric blocking situations and low-level southwesterly flows over New Zealand during June–August 2014. A varying tropopause inversion layer was found to be connected to varying vertical energy fluxes and is, therefore, an important feature with respect to Wave reflection. The subtropical jet was frequently diverted south from its climatological position at 30°S and was most often involved in strong forcing events of mountain Waves at t...
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dynamics of orographic Gravity Waves observed in the mesosphere over the auckland islands during the deep propagating Gravity Wave experiment deepWave
Journal of the Atmospheric Sciences, 2016Co-Authors: Stephen D. Eckermann, David C. Fritts, James D Doyle, Michael J Taylor, Katrina Bossert, Bifford P Williams, Pierredominique Pautet, Dave Broutman, Ronald B SmithAbstract:AbstractOn 14 July 2014 during the Deep Propagating Gravity Wave Experiment (DEEPWave), aircraft remote sensing instruments detected large-amplitude Gravity Wave oscillations within mesospheric airglow and sodium layers at altitudes z ~ 78–83 km downstream of the Auckland Islands, located ~1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier Gravity Wave model are used to investigate the dynamics of this event. At 0700 UTC when the first observations were made, surface flow across the islands’ terrain generated linear three-dimensional Wave fields that propagated rapidly to z ~ 78 km, where intense breaking occurred in a narrow layer beneath a zero-wind region at z ~ 83 km. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these Wave fields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis...
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the deep propagating Gravity Wave experiment deepWave an airborne and ground based exploration of Gravity Wave propagation and effects from their sources throughout the lower and middle atmosphere
Bulletin of the American Meteorological Society, 2016Co-Authors: David C. Fritts, Stephen D. Eckermann, Ronald B Smith, James D Doyle, Michael J Taylor, Andreas Dornbrack, Markus Rapp, Bifford P Williams, Dominique P Pautet, Katrina BossertAbstract:AbstractThe Deep Propagating Gravity Wave Experiment (DEEPWave) was designed to quantify Gravity Wave (GW) dynamics and effects from orographic and other sources to regions of dissipation at high altitudes. The core DEEPWave field phase took place from May through July 2014 using a comprehensive suite of airborne and ground-based instruments providing measurements from Earth’s surface to ∼100 km. Austral winter was chosen to observe deep GW propagation to high altitudes. DEEPWave was based on South Island, New Zealand, to provide access to the New Zealand and Tasmanian “hotspots” of GW activity and additional GW sources over the Southern Ocean and Tasman Sea. To observe GWs up to ∼100 km, DEEPWave utilized three new instruments built specifically for the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV): a Rayleigh lidar, a sodium resonance lidar, and an advanced mesosphere temperature mapper. These measurements were supplemented by in situ probes, dropson...
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scale dependent infrared radiative damping rates on mars and their role in the deposition of Gravity Wave momentum flux
Icarus, 2011Co-Authors: Stephen D. Eckermann, Xun ZhuAbstract:Abstract Using a Curtis-matrix model of 15 μm CO 2 radiative cooling rates for the martian atmosphere, we have computed vertical scale-dependent IR radiative damping rates from 0 to 200 km altitude over a broad band of vertical Wavenumbers ∣ m ∣ = 2 π (1–500 km) −1 for representative meteorological conditions at 40°N and average levels of solar activity and dust loading. In the middle atmosphere, infrared (IR) radiative damping rates increase with decreasing vertical scale and peak in excess of 30 days −1 at ∼50–80 km altitude, before gradually transitioning to scale-independent rates above ∼100 km due to breakdown of local thermodynamic equilibrium. We incorporate these computed IR radiative damping rates into a linear anelastic Gravity-Wave model to assess the impact of IR radiative damping, relative to Wave breaking and molecular viscosity, in the dissipation of Gravity-Wave momentum flux. The model results indicate that IR radiative damping is the dominant process in dissipating Gravity-Wave momentum fluxes at ∼0–50 km altitude, and is the dominant process at all altitudes for Gravity Waves with vertical Wavelengths ≲10–15 km. Wave breaking becomes dominant at higher altitudes only for “fast” Waves of short horizontal and long vertical Wavelengths. Molecular viscosity plays a negligible role in overall momentum flux deposition. Our results provide compelling evidence that IR radiative damping is a major, and often dominant physical process controlling the dissipation of Gravity-Wave momentum fluxes on Mars, and therefore should be incorporated into future parameterizations of Gravity-Wave drag within Mars GCMs. Lookup tables for doing so, based on the current computations, are provided.
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recent developments in Gravity Wave effects in climate models and the global distribution of Gravity Wave momentum flux from observations and models
Quarterly Journal of the Royal Meteorological Society, 2010Co-Authors: Michael A Alexander, Peter Preusse, Stephen D. Eckermann, Marvin A Geller, Albert Hertzog, Kaoru Sato, C Mclandress, Saroja Polavarapu, Fabrizio Sassi, Yoshio KawataniAbstract:Recent observational and theoretical studies of the global properties of small-scale atmospheric Gravity Waves have highlighted the global effects of these Waves on the circulation from the surface to the middle atmosphere. The effects of Gravity Waves on the large-scale circulation have long been treated via parametrizations in both climate and weather-forecasting applications. In these parametrizations, key parameters describe the global distributions of Gravity-Wave momentum flux, Wavelengths and frequencies. Until recently, global observations could not define the required parameters because the Waves are small in scale and intermittent in occurrence. Recent satellite and other global datasets with improved resolution, along with innovative analysis methods, are now providing constraints for the parametrizations that can improve the treatment of these Waves in climate-prediction models. Research using very-high-resolution global models has also recently demonstrated the capability to resolve Gravity Waves and their circulation effects, and when tested against observations these models show some very realistic properties. Here we review recent studies on Gravity-Wave effects in stratosphere-resolving climate models, recent observations and analysis methods that reveal global patterns in Gravity-Wave momentum fluxes and results of very-high-resolution model studies, and we outline some future research requirements to improve the treatment of these Waves in climate simulations. Copyright © 2010 Royal Meteorological Society and Crown in the right of Canada
Peter Preusse - One of the best experts on this subject based on the ideXlab platform.
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The Quest for the Gravity Wave Source
2020Co-Authors: Markus Geldenhuys, Peter Preusse, Isabell Krisch, Joern Ungermann, I. Polichtchouk, Lukas Krasouskas, Felix Friedl-vallon, Martin RieseAbstract:<p>Apart from orography, no specific sources of parametrized Gravity Waves are considered in most global circulation models. This is an inadequate generalization in the long run. In 2002, Charron and Manzini stated that no global Gravity Wave source climatology exist, and in the meantime, little has been done to address this observationally. A single observational case over Greenland is used to illustrate how difficult it is to disentangle the source of a Gravity Wave. The observation was made during the POLar STRAtosphere in a Changing Climate (POLSTRACC) campaign on 10 March 2016. The campaign was based in Kiruna, Sweden and investigated polar air during the polar vortex breakdown in spring. The Gravity Wave was observed between 10 and 15 km, with a horizontal Wavelength of around 300 km and a vertical Wavelength of around 2 km. Several plausible source mechanisms were present at the time of observation, a breaking Rossby Wave, jet exit region, cold front, strong wind shear, and topography. POLSTRACC observations, ECMWF high resolution analysis and ERA 5 reanalysis were used to find the Gravity Wave source. Observations were obtained by the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) instrument based on the High Altitude Long Range (HALO) German research aircraft. GLORIA is an infrared spectrometer that measures many trace gasses in the mid-infrared frequencies. Radiance is changed by inverse-modelling to temperatures. The temperature structure of the Gravity Wave was tomographically reconstructed. The 3D observations correlate well with the model data. ERA 5 data and the Gravity-Wave Regional Or Global Ray Tracer (GROGRAT) was used to determine the exact location of where the Gravity Wave was emitted. Evidence exists that the Gravity Wave could have been released by the geostrophic imbalance in the jet. In contrast, dedicated ECMWF model runs suggest that the origin of the Gravity Wave is in fact orography. However, the Scorer parameter suggests no Gravity Wave can propagate from the surface upwards. Two ECMWF model runs were used to prove this, one normal operational model run, and the second, with a &#8216;flat&#8217; orography. This work indicates that care needs to be exercised to diagnose the source of Gravity Waves, especially without a full informational analysis. Our study illustrates that a better parametrization scheme of Gravity Wave sources should be included in models for a more realistic representation.</p>
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gracile a comprehensive climatology of atmospheric Gravity Wave parameters based on satellite limb soundings
Earth System Science Data, 2018Co-Authors: Manfred Ern, Peter Preusse, Quang Thai Trinh, John C Gille, Martin G Mlynczak, James M Russell, Martin RieseAbstract:Abstract. Gravity Waves are one of the main drivers of atmospheric dynamics. The spatial resolution of most global atmospheric models, however, is too coarse to properly resolve the small scales of Gravity Waves, which range from tens to a few thousand kilometers horizontally, and from below 1 km to tens of kilometers vertically. Gravity Wave source processes involve even smaller scales. Therefore, general circulation models (GCMs) and chemistry climate models (CCMs) usually parametrize the effect of Gravity Waves on the global circulation. These parametrizations are very simplified. For this reason, comparisons with global observations of Gravity Waves are needed for an improvement of parametrizations and an alleviation of model biases. We present a Gravity Wave climatology based on atmospheric infrared limb emissions observed by satellite (GRACILE). GRACILE is a global data set of Gravity Wave distributions observed in the stratosphere and the mesosphere by the infrared limb sounding satellite instruments High Resolution Dynamics Limb Sounder (HIRDLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER). Typical distributions (zonal averages and global maps) of Gravity Wave vertical Wavelengths and along-track horizontal Wavenumbers are provided, as well as Gravity Wave temperature variances, potential energies and absolute momentum fluxes. This global data set captures the typical seasonal variations of these parameters, as well as their spatial variations. The GRACILE data set is suitable for scientific studies, and it can serve for comparison with other instruments (ground-based, airborne, or other satellite instruments) and for comparison with Gravity Wave distributions, both resolved and parametrized, in GCMs and CCMs. The GRACILE data set is available as supplementary data at https://doi.org/10.1594/PANGAEA.879658 .
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A Comparison between Gravity Wave Momentum Fluxes in Observations and Climate Models
Journal of Climate, 2013Co-Authors: Marvin A Geller, Peter Preusse, M. Joan Alexander, Peter T. Love, Julio Bacmeister, Manfred Ern, Albert Hertzog, Elisa Manzini, Kaoru Sato, Adam A. ScaifeAbstract:For the first time, a formal comparison is made between Gravity Wave momentum fluxes in models and those derived from observations. Although Gravity Waves occur over a wide range of spatial and temporal scales, the focus of this paper is on scales that are being parameterized in present climate models, sub-1000-km scales. Only observational methods that permit derivation of Gravity Wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high-vertical-resolution radiosonde data. The models discussed include two high-resolution models in which Gravity Waves are explicitly modeled, Kanto and the Community Atmosphere Model, version 5 (CAM5), and three climate models containing Gravity Wave parameterizations, MAECHAM5, Hadley Centre Global Environmental Model 3 (HadGEM3), and the Goddard Institute for Space Studies (GISS) model. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of Wavelengths, although other factors may contribute. When one accounts for this more rapid fall off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the nonorographic Gravity Wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between Gravity Wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of Gravity Wave sources in climate models.
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recent developments in Gravity Wave effects in climate models and the global distribution of Gravity Wave momentum flux from observations and models
Quarterly Journal of the Royal Meteorological Society, 2010Co-Authors: Michael A Alexander, Peter Preusse, Stephen D. Eckermann, Marvin A Geller, Albert Hertzog, Kaoru Sato, C Mclandress, Saroja Polavarapu, Fabrizio Sassi, Yoshio KawataniAbstract:Recent observational and theoretical studies of the global properties of small-scale atmospheric Gravity Waves have highlighted the global effects of these Waves on the circulation from the surface to the middle atmosphere. The effects of Gravity Waves on the large-scale circulation have long been treated via parametrizations in both climate and weather-forecasting applications. In these parametrizations, key parameters describe the global distributions of Gravity-Wave momentum flux, Wavelengths and frequencies. Until recently, global observations could not define the required parameters because the Waves are small in scale and intermittent in occurrence. Recent satellite and other global datasets with improved resolution, along with innovative analysis methods, are now providing constraints for the parametrizations that can improve the treatment of these Waves in climate-prediction models. Research using very-high-resolution global models has also recently demonstrated the capability to resolve Gravity Waves and their circulation effects, and when tested against observations these models show some very realistic properties. Here we review recent studies on Gravity-Wave effects in stratosphere-resolving climate models, recent observations and analysis methods that reveal global patterns in Gravity-Wave momentum fluxes and results of very-high-resolution model studies, and we outline some future research requirements to improve the treatment of these Waves in climate simulations. Copyright © 2010 Royal Meteorological Society and Crown in the right of Canada
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global ray tracing simulations of the saber Gravity Wave climatology
Journal of Geophysical Research, 2009Co-Authors: Peter Preusse, Stephen D. Eckermann, Martin Riese, Manfred Ern, James M Russell, J Oberheide, Richard H Picard, R G Roble, Martin G MlynczakAbstract:[1] Since February 2002, the SABER (sounding of the atmosphere using broadband emission radiometry) satellite instrument has measured temperatures throughout the entire middle atmosphere. Employing the same techniques as previously used for CRISTA (cryogenic infrared spectrometers and telescopes for the atmosphere), we deduce from SABER V1.06 data 5 years of Gravity Wave (GW) temperature variances from altitudes of 20 to 100 km. A typical annual cycle is presented by calculating averages for the individual calendar months. Findings are consistent with previous results from various satellite missions. Based on zonal mean, SABER data for July and zonal mean GW momentum flux from CRISTA, a homogeneous and isotropic launch distribution for the GROGRAT (Gravity Wave regional or global ray tracer) is tuned. The launch distribution contains different phase speed mesoscale Waves, some of very high-phase speed and extremely low amplitudes, as well as Waves with horizontal Wavelengths of several thousand kilometers. Global maps for different seasons and altitudes, as well as time series of zonal mean GW squared amplitudes based on this launch distribution, match the observations well. Based on this realistic observation-tuned model run, we calculate quantities that cannot be measured directly and are speculated to be major sources of uncertainty in current GW parameterization schemes. Two examples presented in this paper are the average cross-latitude propagation of GWs and the relative acceleration contributions provided by saturation and dissipation, on the one hand, and the horizontal refraction of GWs by horizontal gradients of the mean flow, on the other hand.
Marvin A Geller - One of the best experts on this subject based on the ideXlab platform.
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A Comparison between Gravity Wave Momentum Fluxes in Observations and Climate Models
Journal of Climate, 2013Co-Authors: Marvin A Geller, Peter Preusse, M. Joan Alexander, Peter T. Love, Julio Bacmeister, Manfred Ern, Albert Hertzog, Elisa Manzini, Kaoru Sato, Adam A. ScaifeAbstract:For the first time, a formal comparison is made between Gravity Wave momentum fluxes in models and those derived from observations. Although Gravity Waves occur over a wide range of spatial and temporal scales, the focus of this paper is on scales that are being parameterized in present climate models, sub-1000-km scales. Only observational methods that permit derivation of Gravity Wave momentum fluxes over large geographical areas are discussed, and these are from satellite temperature measurements, constant-density long-duration balloons, and high-vertical-resolution radiosonde data. The models discussed include two high-resolution models in which Gravity Waves are explicitly modeled, Kanto and the Community Atmosphere Model, version 5 (CAM5), and three climate models containing Gravity Wave parameterizations, MAECHAM5, Hadley Centre Global Environmental Model 3 (HadGEM3), and the Goddard Institute for Space Studies (GISS) model. Measurements generally show similar flux magnitudes as in models, except that the fluxes derived from satellite measurements fall off more rapidly with height. This is likely due to limitations on the observable range of Wavelengths, although other factors may contribute. When one accounts for this more rapid fall off, the geographical distribution of the fluxes from observations and models compare reasonably well, except for certain features that depend on the specification of the nonorographic Gravity Wave source functions in the climate models. For instance, both the observed fluxes and those in the high-resolution models are very small at summer high latitudes, but this is not the case for some of the climate models. This comparison between Gravity Wave fluxes from climate models, high-resolution models, and fluxes derived from observations indicates that such efforts offer a promising path toward improving specifications of Gravity Wave sources in climate models.
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New Gravity Wave Treatments for GISS Climate Models
Journal of Climate, 2011Co-Authors: Marvin A Geller, Tiehan Zhou, Reto Ruedy, Igor Aleinov, Larissa Nazarenko, N. Tausnev, Shan Sun, Maxwell Kelley, Y. ChengAbstract:Previous versions of GISS climate models have either used formulations of Rayleigh drag to represent unresolved Gravity Wave interactions with the model-resolved flow or have included a rather complicated treatment of unresolved Gravity Waves that, while being climate interactive, involved the specification of a relatively large number of parameters that were not well constrained by observations and also was computationally very expensive. Here, the authors introduce a relatively simple and computationally efficient specification of unresolved orographic and nonorographic Gravity Waves and their interaction with the resolved flow. Comparisons of the GISS model winds and temperatures with no Gravity Wave parameterization; with only orographic Gravity Wave parameterization; and with both orographic and nonorographic Gravity Wave parameterizations are shown to illustrate how the zonal mean winds and temperatures converge toward observations. The authors also show that the specifications of orographic and nonorographic Gravity Waves must be different in the Northern and Southern Hemispheres. Then results are presented where the nonorographic Gravity Wave sources are specified to represent sources from convection in the intertropical convergencezoneandspontaneousemissionfromjetimbalances.Finally,astrategytoincludetheseeffectsin a climate-dependent manner is suggested.
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recent developments in Gravity Wave effects in climate models and the global distribution of Gravity Wave momentum flux from observations and models
Quarterly Journal of the Royal Meteorological Society, 2010Co-Authors: Michael A Alexander, Peter Preusse, Stephen D. Eckermann, Marvin A Geller, Albert Hertzog, Kaoru Sato, C Mclandress, Saroja Polavarapu, Fabrizio Sassi, Yoshio KawataniAbstract:Recent observational and theoretical studies of the global properties of small-scale atmospheric Gravity Waves have highlighted the global effects of these Waves on the circulation from the surface to the middle atmosphere. The effects of Gravity Waves on the large-scale circulation have long been treated via parametrizations in both climate and weather-forecasting applications. In these parametrizations, key parameters describe the global distributions of Gravity-Wave momentum flux, Wavelengths and frequencies. Until recently, global observations could not define the required parameters because the Waves are small in scale and intermittent in occurrence. Recent satellite and other global datasets with improved resolution, along with innovative analysis methods, are now providing constraints for the parametrizations that can improve the treatment of these Waves in climate-prediction models. Research using very-high-resolution global models has also recently demonstrated the capability to resolve Gravity Waves and their circulation effects, and when tested against observations these models show some very realistic properties. Here we review recent studies on Gravity-Wave effects in stratosphere-resolving climate models, recent observations and analysis methods that reveal global patterns in Gravity-Wave momentum fluxes and results of very-high-resolution model studies, and we outline some future research requirements to improve the treatment of these Waves in climate simulations. Copyright © 2010 Royal Meteorological Society and Crown in the right of Canada
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Gravity Wave kinetic potential and vertical fluctuation energies as indicators of different frequency Gravity Waves
Journal of Geophysical Research, 2010Co-Authors: Marvin A Geller, Jie GongAbstract:[1] An advantage of examining atmospheric Gravity Waves using high vertical-resolution radiosonde data over other measurement techniques is that horizontal wind, temperature, and vertical ascent rate can be measured directly. This allows the kinetic, potential, and vertical velocity fluctuation energies to be derived independently. Each of these Gravity Wave energies is shown to have sensitivity to different Gravity Wave frequencies. Observed correlations among these energies are consistent with this, and simulations of these correlations are shown to constrain Gravity Wave frequency spectra. The climatology of these energies shows quite different variations with month of the year and with latitude such that the vertical fluctuation energy seems to be a better indicator of convectively forced higher-frequency Gravity Waves.
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Gravity Wave kinetic potential and vertical fluctuation energies as indicators of different frequency Gravity Waves
Journal of Geophysical Research, 2010Co-Authors: Marvin A Geller, Jie GongAbstract:[1] An advantage of examining atmospheric Gravity Waves using high vertical-resolution radiosonde data over other measurement techniques is that horizontal wind, temperature, and vertical ascent rate can be measured directly. This allows the kinetic, potential, and vertical velocity fluctuation energies to be derived independently. Each of these Gravity Wave energies is shown to have sensitivity to different Gravity Wave frequencies. Observed correlations among these energies are consistent with this, and simulations of these correlations are shown to constrain Gravity Wave frequency spectra. The climatology of these energies shows quite different variations with month of the year and with latitude such that the vertical fluctuation energy seems to be a better indicator of convectively forced higher-frequency Gravity Waves.
David C. Fritts - One of the best experts on this subject based on the ideXlab platform.
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secondary Gravity Wave generation over new zealand during the deepWave campaign
Journal of Geophysical Research, 2017Co-Authors: Katrina Bossert, David C. Fritts, Christopher G Kruse, C J Heale, J B Snively, Bifford P Williams, Pierredominique Pautet, Michael J TaylorAbstract:Multiple events during the Deep Propagating Gravity Wave Experiment measurement program revealed mountain Wave (MW) breaking at multiple altitudes over the Southern Island of New Zealand. These events were measured during several research flights from the National Science Foundation/National Center for Atmospheric Research Gulfstream V aircraft, utilizing a Rayleigh lidar, an Na lidar, and an Advanced Mesospheric Temperature Mapper simultaneously. A flight on 29 June 2014 observed MWs with horizontal Wavelengths of ~80–120 km breaking in the stratosphere from ~10 to 50 km altitude. A flight on 13 July 2014 observed a horizontal Wavelength of ~200–240 km MW extending from 20 to 90 km in altitude before breaking. Data from these flights show evidence for secondary Gravity Wave (SGW) generation near the breaking regions. The horizontal Wavelengths of these SGWs are smaller than those of the breaking MWs, indicating a nonlinear generation mechanism. These observations reveal some of the complexities associated with MW breaking and the implications this can have on momentum fluxes accompanying SGWs over MW breaking regions.
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dynamics of orographic Gravity Waves observed in the mesosphere over the auckland islands during the deep propagating Gravity Wave experiment deepWave
Journal of the Atmospheric Sciences, 2016Co-Authors: Stephen D. Eckermann, David C. Fritts, James D Doyle, Michael J Taylor, Katrina Bossert, Bifford P Williams, Pierredominique Pautet, Dave Broutman, Ronald B SmithAbstract:AbstractOn 14 July 2014 during the Deep Propagating Gravity Wave Experiment (DEEPWave), aircraft remote sensing instruments detected large-amplitude Gravity Wave oscillations within mesospheric airglow and sodium layers at altitudes z ~ 78–83 km downstream of the Auckland Islands, located ~1000 km south of Christchurch, New Zealand. A high-altitude reanalysis and a three-dimensional Fourier Gravity Wave model are used to investigate the dynamics of this event. At 0700 UTC when the first observations were made, surface flow across the islands’ terrain generated linear three-dimensional Wave fields that propagated rapidly to z ~ 78 km, where intense breaking occurred in a narrow layer beneath a zero-wind region at z ~ 83 km. In the following hours, the altitude of weak winds descended under the influence of a large-amplitude migrating semidiurnal tide, leading to intense breaking of these Wave fields in subsequent observations starting at 1000 UTC. The linear Fourier model constrained by upstream reanalysis...
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stratospheric Gravity Wave fluxes and scales during deepWave
Journal of the Atmospheric Sciences, 2016Co-Authors: Ronald B Smith, David C. Fritts, Alison D Nugent, Christopher G Kruse, James D Doyle, Steven D Eckermann, Michael J Taylor, Andreas Dornbrack, Michael Uddstrom, William A CooperAbstract:AbstractDuring the Deep Propagating Gravity Wave Experiment (DEEPWave) project in June and July 2014, the Gulfstream V research aircraft flew 97 legs over the Southern Alps of New Zealand and 150 legs over the Tasman Sea and Southern Ocean, mostly in the low stratosphere at 12.1-km altitude. Improved instrument calibration, redundant sensors, longer flight legs, energy flux estimation, and scale analysis revealed several new Gravity Wave properties. Over the sea, flight-level Wave fluxes mostly fell below the detection threshold. Over terrain, disturbances had characteristic mountain Wave attributes of positive vertical energy flux (EFz), negative zonal momentum flux, and upwind horizontal energy flux. In some cases, the fluxes changed rapidly within an 8-h flight, even though environmental conditions were nearly unchanged. The largest observed zonal momentum and vertical energy fluxes were MFx = −550 mPa and EFz = 22 W m−2, respectively.A wide variety of disturbance scales were found at flight level over...
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the deep propagating Gravity Wave experiment deepWave an airborne and ground based exploration of Gravity Wave propagation and effects from their sources throughout the lower and middle atmosphere
Bulletin of the American Meteorological Society, 2016Co-Authors: David C. Fritts, Stephen D. Eckermann, Ronald B Smith, James D Doyle, Michael J Taylor, Andreas Dornbrack, Markus Rapp, Bifford P Williams, Dominique P Pautet, Katrina BossertAbstract:AbstractThe Deep Propagating Gravity Wave Experiment (DEEPWave) was designed to quantify Gravity Wave (GW) dynamics and effects from orographic and other sources to regions of dissipation at high altitudes. The core DEEPWave field phase took place from May through July 2014 using a comprehensive suite of airborne and ground-based instruments providing measurements from Earth’s surface to ∼100 km. Austral winter was chosen to observe deep GW propagation to high altitudes. DEEPWave was based on South Island, New Zealand, to provide access to the New Zealand and Tasmanian “hotspots” of GW activity and additional GW sources over the Southern Ocean and Tasman Sea. To observe GWs up to ∼100 km, DEEPWave utilized three new instruments built specifically for the National Science Foundation (NSF)/National Center for Atmospheric Research (NCAR) Gulfstream V (GV): a Rayleigh lidar, a sodium resonance lidar, and an advanced mesosphere temperature mapper. These measurements were supplemented by in situ probes, dropson...
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Gravity Wave penetration into the thermosphere sensitivity to solar cycle variations and mean winds
Annales Geophysicae, 2008Co-Authors: David C. Fritts, Sharon L VadasAbstract:We previously considered various aspects of grav- ity Wave penetration and effects at mesospheric and ther- mospheric altitudes, including propagation, viscous effects on Wave structure, characteristics, and damping, local body forcing, responses to solar cycle temperature variations, and filtering by mean winds. Several of these efforts focused on Gravity Waves arising from deep convection or in situ body forcing accompanying Wave dissipation. Here we generalize these results to a broad range of Gravity Wave phase speeds, spatial scales, and intrinsic frequencies in order to address all of the major Gravity Wave sources in the lower atmosphere potentially impacting the thermosphere. We show how pen- etration altitudes depend on Gravity Wave phase speed, hor- izontal and vertical Wavelengths, and observed frequencies for a range of thermospheric temperatures spanning realistic solar conditions and winds spanning reasonable mean and tidal amplitudes. Our results emphasize that independent of Gravity Wave source, thermospheric temperature, and fil- tering conditions, those Gravity Waves that penetrate to the highest altitudes have increasing vertical Wavelengths and decreasing intrinsic frequencies with increasing altitude. The spatial scales at the highest altitudes at which Gravity Wave perturbations are observed are inevitably horizontal Wave- lengths of 150 to 1000 km and vertical Wavelengths of 150 to 500 km or more, with the larger horizontal scales only becoming important for the stronger Doppler-shifting conditions. Observed and intrinsic periods are typically 10 to 60 min and 10 to 30 min, respectively, with the intrinsic periods shorter at the highest altitudes because of preferen- tial penetration of GWs that are up-shifted in frequency by thermospheric winds.
Manuel Pulido - One of the best experts on this subject based on the ideXlab platform.
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The Role of Gravity Wave Drag Optimization in the Splitting of the Antarctic Vortex in the 2002 Sudden Stratospheric Warming
Geophysical Research Letters, 2018Co-Authors: Guillermo Scheffler, Manuel Pulido, Claudio José Francisco RodasAbstract:The impact of Gravity Wave drag on the Antarctic sudden stratospheric warming (SSW) in 2002 is examined through a mechanistic middle atmosphere model combined with a variational data assimilation system. Significant differences in the SSW representation are found between a model integration that uses reference Gravity Wave parameters and one that uses parameters estimated using data assimilation. Upon identical Wave forcings at 100 hPa, the vortex breakdown may arise as either a vortex splitting event or a displacement vortex event depending on Gravity Wave parameters. A local enhancement of Rossby Waves is found in the integration with estimated parameters, leading to a split SSW. The changes in the vortex breakdown are associated with changes in the vortex geometry caused entirely by modifying the Gravity Wave parameters. Gravity Wave drag proved to play an instrumental role in preconditioning the stratosphere near a resonant excitation point that triggers the split SSW.
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On the Doppler effect in a transient Gravity-Wave spectrum
Quarterly Journal of the Royal Meteorological Society, 2005Co-Authors: Manuel PulidoAbstract:The power-spectrum evolution of a transient Gravity-Wave disturbance propagating conservatively upwards in a shear flow is examined. It is proven that the Wave action for a disturbance suffering Doppler shifting is invariant in the Wave-number space. On the other hand, vertical Wave-momentum flux, even when it is invariant for Waves of fixed frequency, is not invariant in the Wave-number space for a transient disturbance. The principle is used to derive a transformation law between a source spectrum and the resultant Doppler-shifted spectrum. The Doppler-shifted spectrum has a −3 power law in the spectral tail, the asymptotic behaviour of the tail is shown to be independent of the Gravity-Wave source. The result is obtained in two ways: from the Gravity-Wave energy equation and also by Fourier transforming the solution to the Gravity-Wave equations. The derived spectral transformation law should be a key point in spectral Gravity-Wave parametrizations. Copyright © 2005 Royal Meteorological Society
