Lidar Observations of Stratospheric Gravity Waves From 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 2. Potential Energy Densities, Lognormal Distributions, and Seasonal Variations.
16 Aug 2018-Journal of Geophysical Research (John Wiley & Sons, Ltd)-Vol. 123, Iss: 15, pp 7910-7934
TL;DR: It is found that large values of E¯pm during wintertime occur when McMurdo is well inside the polar vortex, and E¯PM variations in winter are mainly due to variations of gravity wave generation in the troposphere and stratosphere and Doppler shifting by the mean stratospheric winds.
Abstract: Five years of Fe Boltzmann lidar's Rayleigh temperature data from 2011 to 2015 at McMurdo are used to characterize gravity wave potential energy mass density (Epm), potential energy volume density (Epv), vertical wave number spectra, and static stability N2 in the stratosphere 30-50 km. Epm (Epv) profiles increase (decrease) with altitude, and the scale heights of Epv indicate stronger wave dissipation in winter than in summer. Altitude mean E¯pm and E¯pv obey lognormal distributions and possess narrowly clustered small values in summer but widely spread large values in winter. E¯pm and E¯pv vary significantly from observation to observation but exhibit repeated seasonal patterns with summer minima and winter maxima. The winter maxima in 2012 and 2015 are higher than in other years, indicating interannual variations. Altitude mean N2¯ varies by ~30-40% from the midwinter maxima to minima around October and exhibits a nearly bimodal distribution. Monthly mean vertical wave number power spectral density for vertical wavelengths of 5-20 km increases from summer to winter. Using Modern Era Retrospective Analysis for Research and Applications version 2 data, we find that large values of E¯pm during wintertime occur when McMurdo is well inside the polar vortex. Monthly mean E¯pm are anticorrelated with wind rotation angles but positively correlated with wind speeds at 3 and 30 km. Corresponding correlation coefficients are -0.62, +0.87, and +0.80, respectively. Results indicate that the summer-winter asymmetry of E¯pm is mainly caused by critical level filtering that dissipates most gravity waves in summer. E¯pm variations in winter are mainly due to variations of gravity wave generation in the troposphere and stratosphere and Doppler shifting by the mean stratospheric winds.
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Texas A&M University1, Ohio State University2, Norwegian Polar Institute3, British Antarctic Survey4, Commonwealth Scientific and Industrial Research Organisation5, Imperial College London6, University of Western Australia7, University of Colorado Boulder8, South Asian University9, Royal Holloway, University of London10, Victoria University of Wellington11, Instituto Antártico Chileno12, Desert Research Institute13, Scientific Committee on Antarctic Research14, University of California, Los Angeles15, Stanford University16, University of California, San Diego17, Australian National University18, Merrimack College19
TL;DR: The view from the south is, more than ever, dominated by ominous signs of change as mentioned in this paper, and a renewed commitment to gathering further knowledge will quicken the pace of understanding of Earth systems and beyond.
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TL;DR: The seasonal and height dependencies of the orographic primary and larger scale secondary gravity waves (GWs) have been studied using the temperature profiles measured by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) from 2002 to 2017.
Abstract: The seasonal and height dependencies of the orographic primary and larger‐scale secondary gravity waves (GWs) have been studied using the temperature profiles measured by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) from 2002 to 2017. At ~40°S and during Southern Hemisphere winter, there is a strong GW peak over the Andes mountains that extend to z ~ 55 km. Using wind and topographic data, we show that orographic GWs break above the peak height of the stratospheric jet. At z ~ 55–65 km, GW breaking and momentum deposition create body forces that generate larger‐scale secondary GWs; we show that these latter GWs form a wide peak above 65 km with a westward tilt. At middle latitudes during summer in the respective hemisphere, orographic GW breaking also generates larger‐scale secondary GWs that propagate to higher altitudes. Both orographic primary and larger‐scale secondary GWs are likely responsible for most of the non‐equatorial peaks of the persistent global distribution of GWs in SABER. Plain Language It is important to characterize orographic primary gravity waves (GWs) and the larger‐scale secondary GWs via both observations and numerical modeling because of their role in dynamics of the atmosphere. We present the global distributions of GWs and the associated larger‐scale secondary GWs in the middle atmosphere (z ~ 30–100 km) from temperature profiles measured by the SABER instrument over the past 16 years (2002–2017). We show that the peaks of the primary and the associated secondary GWs coincide with topographic peaks and that these associations depend on latitude and season. The polar stratospheric jet and the lower stratospheric wind reversal cause the orographic GWs break. The breaking GWs deposit their momentum and induce body forces that generate larger‐scale secondary GWs; these secondary GWs are responsible for the GWs peaks observed above the mountain wave breaking height.
28 citations
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...4512 thereby enabling them to have important influences on the upper atmosphere and ionosphere (Becker & Vadas, 2018; Bossert et al., 2017; Chu et al., 2018; de Wit et al., 2017; Fritts et al., 2016; Heale et al., 2017; Liu & Vadas, 2013; Vadas et al., 2014; Vadas & Becker, 2018; Vadas & Liu, 2009,…...
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TL;DR: The measured amplitudes and phase alignments agree well with operational analyses and short-term forecasts of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF), implying that these quasi-steady gravity waves resulted from the airflow across the Andes.
Abstract: Large-amplitude internal gravity waves were observed using Rayleigh lidar temperature soundings above Rio Grande, Argentina (
$$54^\circ \; \hbox {S}$$
,
$$68^\circ \; \hbox {W}$$
), in the period 16–23 June 2018. Temperature perturbations in the upper stratosphere amounted to 80 K peak-to-peak and potential energy densities exceeded 400 J/kg. The measured amplitudes and phase alignments agree well with operational analyses and short-term forecasts of the Integrated Forecasting System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF), implying that these quasi-steady gravity waves resulted from the airflow across the Andes. We estimate gravity wave momentum fluxes larger than 100 mPa applying independent methods to both lidar data and IFS model data. These mountain waves deposited momentum at the inner edge of the polar night jet and led to a long-lasting deceleration of the stratospheric flow. The accumulated mountain wave drag affected the stratospheric circulation several thousand kilometers downstream. In the 2018 austral winter, mountain wave events of this magnitude contributed more than 30% of the total potential energy density, signifying their importance by perturbing the stratospheric polar vortex.
27 citations
University of Bern1, Goddard Space Flight Center2, German Aerospace Center3, Embry-Riddle Aeronautical University, Daytona Beach4, Colorado Center for Astrodynamics Research5, British Antarctic Survey6, Fraunhofer Society7, Chungnam National University8, Australian Antarctic Division9, University of Bath10
TL;DR: In this article, the seasonal variability of the mean winds and diurnal and semidiurnal tidal amplitude and phases, as well as the Reynolds stress components during 2019, utilizing meteor radars at six Southern Hemisphere locations ranging from midlatitudes to polar latitudes.
Abstract: . In this study we explore the seasonal variability of the mean winds and diurnal and semidiurnal tidal amplitude and phases, as well as the Reynolds stress components during 2019, utilizing meteor radars at six Southern Hemisphere locations ranging from midlatitudes to polar latitudes. These include Tierra del Fuego, King Edward Point on South Georgia island, King Sejong Station, Rothera, Davis, and McMurdo stations. The year 2019 was exceptional in the Southern Hemisphere, due to the occurrence of a rare minor stratospheric warming in September. Our results show a substantial longitudinal and latitudinal seasonal variability of mean winds and tides, pointing towards a wobbling and asymmetric polar vortex. Furthermore, the derived momentum fluxes and wind variances, utilizing a recently developed algorithm, reveal a characteristic seasonal pattern at each location included in this study. The longitudinal and latitudinal variability of vertical flux of zonal and meridional momentum is discussed in the context of polar vortex asymmetry, spatial and temporal variability, and the longitude and latitude dependence of the vertical propagation conditions of gravity waves. The horizontal momentum fluxes exhibit a rather consistent seasonal structure between the stations, while the wind variances indicate a clear seasonal behavior and altitude dependence, showing the largest values at higher altitudes during the hemispheric winter and two variance minima during the equinoxes. Also the hemispheric summer mesopause and the zonal wind reversal can be identified in the wind variances.
21 citations
TL;DR: In this paper, an analysis of derived temperatures from the Atmospheric InfraRed Sounder (AIRS) provides insight into the sources of gravity wave activity over Europe, including a new observation of stratosphere polar night jet (PNJ) generated GWs.
Abstract: Observations during 12 January 2016 revealed a series of events of significant gravity wave (GW) activity over Europe. Analysis of derived temperatures from the Atmospheric InfraRed Sounder (AIRS) provides insight into the sources of these GWs, and include a new observation of stratosphere polar night jet (PNJ) generated GWs. Mountain waves were present during this time as well over the French Alps and the Carpathian Mountains and had maximum temperature perturbations, T′, as large as 27 K over the French Alps. Further investigation of the mountain waves that demonstrated their presence in the stratosphere was determined not only by stratospheric conditions but also by strong winds in the troposphere and at the surface. GWs generated in the stratosphere by the PNJ hadmaximum T′ of 7 K. These observations demonstrate multiple sources of GWs during a dynamically active period and implicate the role of the PNJ in both the vertical propagation of GWs generated in the troposphere and the generation of GWs from the PNJ itself.
19 citations
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...Other observations have demonstrated a positive correlation between GW activity and wind speed in the stratosphere (Chu et al., 2018; Llamedo et al., 2019)....
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References
More filters
Book•
01 Jan 1969
TL;DR: In this article, the authors propose a linearized theory of elasticity for tensors, which they call Linearized Theory of Elasticity (LTHE), which is based on tensors and elasticity.
Abstract: 1. Vectors and Tensors. 2. Strain and Deformation. 3. General Principles. 4. Constitutive Equations. 5. Fluid Mechanics. 6. Linearized Theory of Elasticity. Appendix I: Tensors. Appendix II: Orthogonal Curvilinear.
3,658 citations
"Lidar Observations of Stratospheric..." refers background in this paper
...The “Q diagnostic” measures the relative contribution of strain and rotation in the flow (Malvern, 1969); Q is negative in regions where rotation is dominant and positive where there is strong shear....
[...]
TL;DR: In this article, a review of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape are discussed.
Abstract: [1] Atmospheric gravity waves have been a subject of intense research activity in recent years because of their myriad effects and their major contributions to atmospheric circulation, structure, and variability. Apart from occasionally strong lower-atmospheric effects, the major wave influences occur in the middle atmosphere, between ∼ 10 and 110 km altitudes because of decreasing density and increasing wave amplitudes with altitude. Theoretical, numerical, and observational studies have advanced our understanding of gravity waves on many fronts since the review by Fritts [1984a]; the present review will focus on these more recent contributions. Progress includes a better appreciation of gravity wave sources and characteristics, the evolution of the gravity wave spectrum with altitude and with variations of wind and stability, the character and implications of observed climatologies, and the wave interaction and instability processes that constrain wave amplitudes and spectral shape. Recent studies have also expanded dramatically our understanding of gravity wave influences on the large-scale circulation and the thermal and constituent structures of the middle atmosphere. These advances have led to a number of parameterizations of gravity wave effects which are enabling ever more realistic descriptions of gravity wave forcing in large-scale models. There remain, nevertheless, a number of areas in which further progress is needed in refining our understanding of and our ability to describe and predict gravity wave influences in the middle atmosphere. Our view of these unknowns and needs is also offered.
2,206 citations
"Lidar Observations of Stratospheric..." refers background in this paper
...…are known to play essential roles in transporting energy and momentum from the lower to the middle and upper atmosphere and in driving the general circulation of the Earth’s atmosphere (e.g., Fritts & Alexander, 2003; Hines, 1960, 1974; Hitchman et al., 1989; Holton, 1982, 1983; Lindzen, 1981)....
[...]
TL;DR: In this article, the effects of mean winds and gravity waves on the mean momentum budget were investigated and it was shown that the existence of critical levels in the mesosphere significantly limits the ability of gravity waves to generate turbulence.
Abstract: It has been suggested (Lindzen, 1967, 1968a, b; Lindzen and Blake, 1971; Hodges, 1969) that turbulence in the upper mesosphere arises from the unstable breakdown of tides and gravity waves. Crudely speaking, it was expected that sufficient turbulence would be generated to prevent the growth of wave amplitude with height (roughly as (basic pressure)−1/2). This work has been extended to allow for the generation of turbulence by smaller amplitude waves, the effects of mean winds on the waves, and the effects of the waves on the mean momentum budget. The effects of mean winds, while of relatively small importance for tides, are crucial for internal gravity waves originating in the troposphere. Winds in the troposphere and stratosphere sharply limit the phase speeds of waves capable of reaching the upper mesosphere. In addition, the existence of critical levels in the mesosphere significantly limits the ability of gravity waves to generate turbulence, while the breakdown of gravity waves contributes to the development of critical levels. The results of the present study suggest that at middle latitudes in winter, eddy coefficients may peak at relatively low altitudes (50 km) and at higher altitudes in summer and during sudden warmings (70–80 km), and decrease with height rather sharply above these levels. Rocket observations are used to estimate momentum deposition by gravity waves. Accelerations of about 100 m/s/day are suggested. Such accelerations are entirely capable of producing the warm winter and cold summer mesopauses.
1,967 citations
"Lidar Observations of Stratospheric..." refers background in this paper
...These gravity waves are then filtered by the prevailing wind system in the stratosphere such that only gravity waves with significant eastward phase speeds are relevant in the summer mesosphere (see Becker, 2012; Hoffmann et al., 2010; Lindzen, 1981)....
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...…are known to play essential roles in transporting energy and momentum from the lower to the middle and upper atmosphere and in driving the general circulation of the Earth’s atmosphere (e.g., Fritts & Alexander, 2003; Hines, 1960, 1974; Hitchman et al., 1989; Holton, 1982, 1983; Lindzen, 1981)....
[...]
TL;DR: In this paper, the proper interpretation of irregular motions in the upper atmosphere has been investigated by a variety of techniques, but their proper interpretation has yet to be established. But their proper meaning has not yet been established.
Abstract: Irregularities and irregular motions in the upper atmosphere have been detected and studied by a variety of techniques during recent years, but their proper interpretation has yet to be established...
1,886 citations
"Lidar Observations of Stratospheric..." refers background in this paper
...…are known to play essential roles in transporting energy and momentum from the lower to the middle and upper atmosphere and in driving the general circulation of the Earth’s atmosphere (e.g., Fritts & Alexander, 2003; Hines, 1960, 1974; Hitchman et al., 1989; Holton, 1982, 1983; Lindzen, 1981)....
[...]
TL;DR: In this article, a slightly modified version of the parameterization suggested by Lindzen (1981) for the zonal drag and eddy diffusion effects generated by breaking internal gravity waves in the mesosphere is tested using a severely truncated midlatitude beta-plane channel model.
Abstract: A slight modification of the parameterization suggested by Lindzen (1981) for the zonal drag and eddy diffusion effects generated by breaking internal gravity waves in the mesosphere is tested using a severely truncated midlatitude beta-plane channel model. It is found that realistic mean zonal flow profiles with zonal wind reversals above the mesopause can be simulated for both winter and summer radiative heating conditions provided that a gravity-wave spectrum is assumed which includes both stationary waves and waves of relatively large phase speeds. These results contrast greatly with the unrealistic mean wind profiles produced when Rayleigh friction is used to parameterize the effects of small scale motions on the mean flow.
647 citations
"Lidar Observations of Stratospheric..." refers background in this paper
...…are known to play essential roles in transporting energy and momentum from the lower to the middle and upper atmosphere and in driving the general circulation of the Earth’s atmosphere (e.g., Fritts & Alexander, 2003; Hines, 1960, 1974; Hitchman et al., 1989; Holton, 1982, 1983; Lindzen, 1981)....
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