Role of gravity waves in the forcing of quasi two‐day waves in the mesosphere: An observational study

Ern, Manfred; Preusse, Peter; Kalisch, Silvio; Kaufmann, Martín; Riese, Martin

doi:10.1029/2012jd018208

Cited by 91 publications

(159 citation statements)

References 98 publications

(211 reference statements)

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“…Despite this systematic difference, the seasonal and latitudinal distributions of stratospheric gravity wave activity found in both data sets are rather similar. Overall, these variations are related to the well-known seasonal patterns of gravity wave activity with summertime maxima in the subtropics and wintertime max- ima at high latitudes (e.g., Ern et al, 2011Ern et al, , 2013Hoffmann et al, 2013Hoffmann et al, , 2014. Several sources of gravity waves can produce these maxima.…”

Section: Discussionmentioning

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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Section: Discussionmentioning

confidence: 99%

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

Meyer¹,

Ern²,

Hoffmann³

et al. 2018

Atmos. Meas. Tech.

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“…For this purpose, longitude-time spectra are estimated for a fixed set of altitudes and latitudes. This procedure is described in detail in Ern et al (2011), and it accounts also for fast traveling planetary waves, such as shortperiod Kelvin waves (e.g., Ern et al, 2008;Ern and Preusse, 2009; or quasi 2-day waves (e.g., Ern et al, 2013). Tides, however, are removed separately, as described in Ern et al (2013).…”

Section: Satellite Observations Of Gravity Wave Amplitudes Momentummentioning

confidence: 99%

“…This is particularly relevant for our study, because SABER does not continuously observe high northern latitudes. SABER temperature profiles have an altitude resolution of about 2 km, and every second pair of consecutive altitude profiles has an along track sampling of better than 300 km, allowing to derive gravity wave absolute momentum fluxes (e.g., Ern et al, 2011;Ern et al, 2013). In our study, we use SABER version v2.00 temperatures.…”

Section: The Saber Instrumentmentioning

confidence: 99%

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

Ern¹,

Trinh²,

Kaufmann³

et al. 2016

Atmos. Chem. Phys.

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Abstract. Sudden stratospheric warmings (SSWs) are circulation anomalies in the polar region during winter. They mostly occur in the Northern Hemisphere and affect also surface weather and climate. Both planetary waves and gravity waves contribute to the onset and evolution of SSWs. While the role of planetary waves for SSW evolution has been recognized, the effect of gravity waves is still not fully understood, and has not been comprehensively analyzed based on global observations. In particular, information on the gravity wave driving of the background winds during SSWs is still missing.

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“…In particular, Kelvin waves in the tropics, which can have very short periods of only a few days (e.g., Smith et al, 2002;Forbes et al, 2009;, are also removed. The strongest tidal modes are removed by subtracting quasi-stationary zonal wave numbers 0-4 separately for ascending and descending parts of the satellite orbits (see also Ern et al, 2013).…”

Section: Extraction Of Gravity Wavesmentioning

confidence: 99%

Driving of the SAO by gravity waves as observed from satellite

Ern¹,

Preusse²,

Riese³

2015

Ann. Geophys.

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Abstract. It is known that atmospheric dynamics in the tropical stratosphere have an influence on higher altitudes and latitudes as well as on surface weather and climate. In the tropics, the dynamics are governed by an interplay of the quasi-biennial oscillation (QBO) and semiannual oscillation (SAO) of the zonal wind. The QBO is dominant in the lower and middle stratosphere, and the SAO in the upper stratosphere/lower mesosphere. For both QBO and SAO the driving by atmospheric waves plays an important role. In particular, the role of gravity waves is still not well understood.In our study we use observations of the High Resolution Dynamics Limb Sounder (HIRDLS) satellite instrument to derive gravity wave momentum fluxes and gravity wave drag in order to investigate the interaction of gravity waves with the SAO. These observations are compared with the ERA-Interim reanalysis. Usually, QBO westward winds are much stronger than QBO eastward winds. Therefore, mainly gravity waves with westward-directed phase speeds are filtered out through critical-level filtering already below the stratopause region. Accordingly, HIRDLS observations show that gravity waves contribute to the SAO momentum budget mainly during eastward wind shear, and not much during westward wind shear. These findings confirm theoretical expectations and are qualitatively in good agreement with ERA-Interim and other modeling studies. In ERAInterim most of the westward SAO driving is due to planetary waves, likely of extratropical origin. Still, we find in both observations and ERA-Interim that sometimes westwardpropagating gravity waves may contribute to the westward driving of the SAO. Four characteristic cases of atmospheric background conditions are identified. The forcings of the SAO in these cases are discussed in detail, supported by gravity wave spectra observed by HIRDLS. In particular, we find that the gravity wave forcing of the SAO cannot be explained by critical-level filtering alone; gravity wave saturation without critical levels being reached is also important.

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Role of gravity waves in the forcing of quasi two‐day waves in the mesosphere: An observational study

Cited by 91 publications

References 98 publications

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

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

Driving of the SAO by gravity waves as observed from satellite

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