Satellite observations of middle atmosphere gravity wave
absolute momentum flux and of its vertical
gradient during recent stratospheric warmings

Ern, Manfred; Trinh, Quang Thai; Kaufmann, Martín; Krisch, Isabell; Preusse, Peter; Ungermann, Jörn; Zhu, Yajun; Gille, J. C.; Mlynczak, Martin G.; Russell, James M.; Schwartz, M.; Riese, Martin

doi:10.5194/acp-16-9983-2016

Cited by 77 publications

(122 citation statements)

References 117 publications

(178 reference statements)

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“…The variation in gravity wave activity follows the variation in wind speed at 10 hPa. There is a general decrease in both gravity wave activity and wind speed over the seven-week period that has also been reported in satellite studies of stratospheric gravity wave activity during the 2009 SSW [37]. The decrease in gravity wave activity on 29 January followed by an increase on 3 February corresponds to a decrease in wind speed followed by an increase in wind speed.…”

Section: The 2009 Stratospheric Sudden Warmingsupporting

confidence: 74%

“…The modulation of gravity wave propagation by stratospheric winds and critical layer filtering has been documented since the 1990s [41]. Several studies in the Arctic have highlighted this modulation of gravity wave activity by the winds [18,37,42]. In this study, we have shown the systematic interannual modulation of the wintertime gravity wave activity associated with the occurrence of SSWs.…”

Section: Discussionsupporting

confidence: 56%

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Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

et al. 2017

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Abstract:The meteorological control of gravity wave activity through filtering by winds and generation by spontaneous adjustment of unbalanced flows is investigated. This investigation is based on a new analysis of Rayleigh LiDAR measurements of gravity wave activity in the upper stratosphere-lower mesosphere (USLM, 40-50 km) on 152 nights at Poker Flat Research Range (PFRR), Chatanika, Alaska (65 • N, 147 • W), over 13 years between 1998 and 2014. The LiDAR measurements resolve inertia-gravity waves with observed periods between 1 h and 4 h and vertical wavelengths between 2 km and 10 km. The meteorological conditions are defined by reanalysis data from the Modern-Era Retrospective Analysis for Research and Applications (MERRA). The gravity wave activity shows large night-to-night variability, but a clear annual cycle with a maximum in winter, and systematic interannual variability associated with stratospheric sudden warming events. The USLM gravity wave activity is correlated with the MERRA winds and is controlled by the winds in the lower stratosphere through filtering by critical layer filtering. The USLM gravity wave activity is also correlated with MERRA unbalanced flow as characterized by the residual of the nonlinear balance equation. This correlation with unbalanced flow only appears when the wind conditions are taken into account, indicating that wind filtering is the primary control of the gravity wave activity.

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Section: The 2009 Stratospheric Sudden Warmingsupporting

confidence: 74%

Section: Discussionsupporting

confidence: 56%

Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

et al. 2017

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“…Thus we can only examine the possible in situ generation of polar mesospheric SPW by longitudinally variable GW drag for the second half of the investigation time period. The GW drag is calculated via a multi-step procedure (Ern et al, 2011(Ern et al, , 2016.…”

Section: Instruments and Methodsmentioning

confidence: 99%

“…Therefore we investigate the longitudinal structure of absolute GW drag that is obtained from vertical gradients of absolute GW momentum fluxes which are derived from SABER temperature observations (see also Ern et al, 2011Ern et al, , 2016, and references therein). This parameter does not provide directional information unless atmospheric background conditions allow for assumptions to be made and it can be used as a proxy for "real" GW drag.…”

Section: Why Does the Spw 2 Dominate In Period Ii?mentioning

confidence: 99%

On the origin of the mesospheric quasi-stationary planetary waves in the unusual Arctic winter 2015/2016

Matthias

Ern²

2018

Atmos. Chem. Phys.

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Abstract. The midwinter 2015/2016 was characterized by an unusually strong polar night jet (PNJ) and extraordinarily large stationary planetary wave (SPW) amplitudes in the subtropical mesosphere. The aim of this study is, therefore, to find the origin of these mesospheric SPWs in the midwinter 2015/2016 study period. The study duration is split into two periods: the first period runs from late December 2015 until early January 2016 (Period I), and the second period from early January until mid-January 2016 (Period II). While the SPW 1 dominates in the subtropical mesosphere in Period I, it is the SPW 2 that dominates in Period II. There are three possibilities explaining how SPWs can occur in the mesosphere: (1) they propagate upward from the stratosphere, (2) they are generated in situ by longitudinally variable gravity wave (GW) drag, or (3) they are generated in situ by barotropic and/or baroclinic instabilities. Using global satellite observations from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) the origin of the mesospheric SPWs is investigated for both time periods. We find that due to the strong PNJ the SPWs were not able to propagate upward into the mesosphere northward of 50 • N but were deflected upward and equatorward into the subtropical mesosphere. We show that the SPWs observed in the subtropical mesosphere are the same SPWs as in the mid-latitudinal stratosphere. Simultaneously, we find evidence that the mesospheric SPWs in polar latitudes were generated in situ by longitudinally variable GW drag and that there is a mixture of in situ generation by longitudinally variable GW drag and by instabilities at mid-latitudes. Our results, based on observations, show that the abovementioned three mechanisms can act at the same time which confirms earlier model studies. Additionally, the possible contribution from, or impact of, unusually strong SPWs in the subtropical mesosphere to the disruption of the quasi-biennial oscillation (QBO) in the same winter is discussed.

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“…In the high-resolution retrieval of AIRS it could be seen, with a small delay, that the gravity wave activity is strengthening after the SSW when the zonal wind increases again. For an overview of gravity wave activity in the Northern Hemisphere polar region during recent winters see Ern et al (2016). Hoffmann et al (2016) discussed gravity wave activity located at Southern Hemisphere orographic hotspots and their correlation with background winds in more detail.…”

Section: Time Series Of Gravity Wave Variancesmentioning

confidence: 99%

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

Meyer¹,

Ern²,

Hoffmann³

et al. 2018

Atmos. Meas. Tech.

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Abstract. We investigate stratospheric gravity wave observations by the Atmospheric InfraRed Sounder (AIRS) aboard NASA's Aqua satellite and the High Resolution Dynamics Limb Sounder (HIRDLS) aboard NASA's Aura satellite. AIRS operational temperature retrievals are typically not used for studies of gravity waves, because their vertical and horizontal resolution is rather limited. This study uses data of a high-resolution retrieval which provides stratospheric temperature profiles for each individual satellite footprint. Therefore the horizontal sampling of the high-resolution retrieval is 9 times better than that of the operational retrieval. HIRDLS provides 2-D spectral information of observed gravity waves in terms of along-track and vertical wavelengths. AIRS as a nadir sounder is more sensitive to short-horizontal-wavelength gravity waves, and HIRDLS as a limb sounder is more sensitive to short-vertical-wavelength gravity waves. Therefore HIRDLS is ideally suited to complement AIRS observations. A calculated momentum flux factor indicates that the waves seen by AIRS contribute significantly to momentum flux, even if the AIRS temperature variance may be small compared to HIRDLS. The stratospheric wave structures observed by AIRS and HIRDLS often agree very well. Case studies of a mountain wave event and a non-orographic wave event demonstrate that the observed phase structures of AIRS and HIRDLS are also similar. AIRS has a coarser vertical resolution, which results in an attenuation of the amplitude and coarser vertical wavelengths than for HIRDLS. However, AIRS has a much higher horizontal resolution, and the propagation direction of the waves can be clearly identified in geographical maps. The horizontal orientation of the phase fronts can be deduced from AIRS 3-D temperature fields. This is a restricting factor for gravity wave analyses of limb measurements. Additionally, temperature variances with respect to stratospheric gravity wave activity are compared on a statistical basis. The complete HIRDLS measurement period from January 2005 to March 2008 is covered. The seasonal and latitudinal distributions of gravity wave activity as observed by AIRS and HIRDLS agree well. A strong annual cycle at mid-and high latitudes is found in time series of gravity wave variances at 42 km, which has its maxima during wintertime and its minima during summertime. The variability is largest during austral wintertime at 60 • S. Variations in the zonal winds at 2.5 hPa are associated with large variability in gravity wave variances. Altogether, gravity wave variances of AIRS and HIRDLS are complementary to each other. Large parts of the gravity wave spectrum are covered by joint observations. This opens up fascinating vistas for future gravity wave research.

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Satellite observations of middle atmosphere gravity wave absolute momentum flux and of its vertical gradient during recent stratospheric warmings

Cited by 77 publications

References 117 publications

Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

Role of Wind Filtering and Unbalanced Flow Generation in Middle Atmosphere Gravity Wave Activity at Chatanika Alaska

On the origin of the mesospheric quasi-stationary planetary waves in the unusual Arctic winter 2015/2016

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

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