Gravity Wave Characteristics in the Southern Hemisphere Revealed by a High-Resolution Middle-Atmosphere General Circulation Model

Sato, K.; Tateno, Satoshi; Watanabe, Shingo; Kawatani, Yoshio

doi:10.1175/jas-d-11-0101.1

Cited by 207 publications

(333 citation statements)

References 55 publications

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“…Gravity wave activity over the Rocky Mountains is largely absent, which is due to relatively low stratospheric background winds over this mountain range (Hoffmann et al, 2013(Hoffmann et al, , 2014. In the Southern Hemisphere, we found increased gravity wave activity in a latitude band around 70-50 • S during the winter months, which is attributed mostly to jet and storm sources (Sato et al, 2012;Hendricks et al, 2014;Hindley et al, 2015). Orographic hot spots can be identified in the southern Andes, the Antarctic Peninsula, South Georgia, the Kerguelen Islands, and the Transantarctic Mountains.…”

Section: Temporal and Spatial Patterns Of Gravity Wave Activitymentioning

confidence: 61%

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

et al. 2017

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Abstract. Atmospheric gravity waves yield substantial small-scale temperature fluctuations that can trigger the formation of polar stratospheric clouds (PSCs). This paper introduces a new satellite record of gravity wave activity in the polar lower stratosphere to investigate this process. The record is comprised of observations of the Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite from January 2003 to December 2012. Gravity wave activity is measured in terms of detrended and noise-corrected 15 µm brightness temperature variances, which are calculated from AIRS channels that are the most sensitive to temperature fluctuations at about 17-32 km of altitude. The analysis of temporal patterns in the data set revealed a strong seasonal cycle in wave activity with wintertime maxima at mid-and high latitudes. The analysis of spatial patterns indicated that orography as well as jet and storm sources are the main causes of the observed waves. Wave activity is closely correlated with 30 hPa zonal winds, which is attributed to the AIRS observational filter. We used the new data set to evaluate explicitly resolved temperature fluctuations due to gravity waves in the European Centre for Medium-Range Weather Forecasts (ECMWF) operational analysis. It was found that the analysis reproduces orographic and non-orographic wave patterns in the right places, but that wave amplitudes are typically underestimated by a factor of 2-3. Furthermore, in a first survey of joint AIRS and Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) satellite observations, nearly 50 gravity-wave-induced PSC formation events were identified. The survey shows that the new AIRS data set can help to better identify such events and more generally highlights the importance of the process for polar ozone chemistry.

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Section: Temporal and Spatial Patterns Of Gravity Wave Activitymentioning

confidence: 61%

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

et al. 2017

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“…Using radiosonde measurements, Yoshiki and Sato (2000) and Sato and Yoshiki (2008) observed the downward propagating gravity waves around the stratospheric polar night jet that are generated from the upper-stratosphere jet by a spontaneous adjustment process. Recently, Sato et al (2012) proposed the partial reflection mechanism by a rapid change in the static stability for the downward propagating waves near the stratospheric polar jet simulated in a high-resolution general circulation model. It is noteworthy, however, that in the conventional sounding analysis, it is non-trivial to extract the background state from the observed profile (e.g., Zhang et al, 2004), especially the background state that changes rapidly with height.…”

Section: Discussionmentioning

confidence: 99%

Gravity wave reflection and its influence on the consistency of temperature- and wind-based momentum fluxes simulated above Typhoon Ewiniar

Kim

Chun

Preusse³

et al. 2012

Atmos. Chem. Phys.

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Abstract. For a case study of Typhoon Ewiniar performed with a mesoscale model, we compare stratospheric gravity wave (GW) momentum flux determined from temperature variances by applying GW polarization relations and by assuming upward propagating waves, with GW momentum flux calculated from model winds which is considered as a reference. The temperature-based momentum-flux profile exhibits positive biases relative to the reference, which fluctuate significantly with altitude. The vertically-averaged magnitude of the positive biases is about 14 % of the reference momentum flux. We found that this deviation from the reference stems from the interference between upward and downward propagating waves. The downward propagating GWs are due mainly to partial reflections of upward propagating waves at altitudes where the background wind and stability change with height. When the upward and downward propagating waves are decomposed and their momentum fluxes are calculated separately from temperature perturbations, the fraction of the momentum flux arising from the downward propagating waves is about 4.5-8.2 % of that from the upward propagating waves. The net momentum flux of upward and downward propagating GWs agrees well with the reference from the model wind perturbations. The implications of this study for the GW momentum-flux observations from satellites are discussed.

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“…Phys. their own horizontal group velocity is sometimes significant (e.g., Sato et al, 2009Sato et al, , 2012. BDC affects the global climate by modifying the tropopause structure, such as static stability and westerly jet latitudes (e.g., Kidston et al, 2015;Kohma and Sato, 2014;Li and Thompson, 2013).…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

The Climatology of Brewer-Dobson Circulation and the Contribution of Gravity Waves

Sato¹,

Hirano²

2018

Preprint

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Abstract. The climatology of residual mean circulation, which is a main component of Brewer-Dobson circulation, and the potential contribution of gravity waves (GWs) are examined for the annual mean state and for each season based on the transformed-Eulerian mean zonal momentum equation using modern four reanalysis data, which allows us to examine the whole stratosphere. First, the potential contribution of Rossby waves (RWs) to residual mean circulation is estimated from Eliassen-Palm flux divergence. The rest of residual-mean circulation, from which the potential RW contribution and zonal 10 mean zonal wind tendency are subtracted, is regarded as the potential GW contribution. These potential wave contributions are exact contributions for the annual mean state and give good approximates for solstitial seasons. The GWs contribute to drive not only the summer hemispheric part of the winter deep branch and low-latitude part of shallow branches, as indicated by previous studies, but also cause a higher-latitude extension of the deep circulation in all seasons except for summer. This GW contribution is essential to determine the location of the turn-around latitude. The autumn circulation is stronger and wider 15 than that of spring in the equinoctial seasons, regardless of almost symmetric RW and GW contributions around the equator. This asymmetry is attributable to the existence of the spring-to-autumn pole circulation corresponding to the angular momentum transport associated with seasonal variation due to the radiative process. The potential GW contribution is larger in September-to-November than in March-to-May in both hemispheres. The upward mass flux is maximized in the boreal winter in the lower stratosphere, while it exhibits semi-annual variation in the upper stratosphere. The GW contribution to the 20 annual mean upward mass flux is in a range of 10-30 %, depending on the reanalysis data. The boreal winter maximum in the lower stratosphere is attributable to stronger RW activity in both hemispheres than in the austral winter.

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Gravity Wave Characteristics in the Southern Hemisphere Revealed by a High-Resolution Middle-Atmosphere General Circulation Model

Cited by 207 publications

References 55 publications

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

A decadal satellite record of gravity wave activity in the lower stratosphere to study polar stratospheric cloud formation

Gravity wave reflection and its influence on the consistency of temperature- and wind-based momentum fluxes simulated above Typhoon Ewiniar

The Climatology of Brewer-Dobson Circulation and the Contribution of Gravity Waves

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