Gravity waves over Antarctica and the Southern Ocean: consistent momentum fluxes in mesoscale simulations and stratospheric balloon observations

Plougonven, Riwal; Hertzog, Albert; Guez, Lionel

doi:10.1002/qj.1965

Cited by 102 publications

(188 citation statements)

References 39 publications

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“…Our observations show clearly that directional MF in this region is primarily directed directly upwind and is greatest above mountainous regions, consistent with previous studies (Plougonven et al, 2013;Wright et al, 2016a;Ern et al, 2017). The spatial correspondence with topography at low altitudes is extremely close, particularly over the Antarctic Peninsula.…”

Section: Discussionsupporting

confidence: 92%

“…This variability is significant, with diurnal variations in MF of hundreds of percent not atypical (Hertzog et al, 2012;Plougonven et al, 2013;. This has major implications on the background atmosphere.…”

Section: Intermittencymentioning

confidence: 99%

“…Fritts et al, 2010Fritts et al, , 2012Wright et al, 2016b), in situ super-pressure balloons (e.g. Hertzog et al, 2008;Plougonven et al, 2013), and satellite limb (e.g. Eckermann and Preusse, 1999;Jiang, 2002;Alexander and Teitelbaum, 2011) and nadir sounders (e.g.…”

Section: Gravity Waves and The Drake Passage Regionmentioning

confidence: 99%

“…Previous studies (Plougonven et al, 2013; have proposed the use of Gini's coefficient of concentration G (Gini, 1912) as a metric for this intermittency. G provides a single-number estimate of the evenness of a distribution, with 0 representing a perfectly even distribution (i.e.…”

Section: Intermittencymentioning

confidence: 99%

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Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

Wright

Hindley

Hoffmann³

et al. 2017

Atmos. Chem. Phys.

112

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Abstract. Gravity waves (GWs) transport momentum and energy in the atmosphere, exerting a profound influence on the global circulation. Accurately measuring them is thus vital both for understanding the atmosphere and for developing the next generation of weather forecasting and climate prediction models. However, it has proven very difficult to measure the full set of GW parameters from satellite measurements, which are the only suitable observations with global coverage. This is particularly critical at latitudes close to 60 • S, where climate models significantly under-represent wave momentum fluxes. Here, we present a novel fully 3-D method for detecting and characterising GWs in the stratosphere. This method is based around a 3-D Stockwell transform, and can be applied retrospectively to existing observed data. This is the first scientific use of this spectral analysis technique. We apply our method to high-resolution 3-D atmospheric temperature data from AIRS/Aqua over the altitude range 20-60 km. Our method allows us to determine a wide range of parameters for each wave detected. These include amplitude, propagation direction, horizontal/vertical wavelength, height/direction-resolved momentum fluxes (MFs), and phase and group velocity vectors. The latter three have not previously been measured from an individual satellite instrument. We demonstrate this method over the region around the Southern Andes and Antarctic Peninsula, the largest known sources of GW MFs near the 60 • S belt. Our analyses reveal the presence of strongly intermittent highly directionally focused GWs with very high momentum fluxes (∼ 80-100 mPa or more at 30 km altitude). These waves are closely associated with the mountains rather than the open ocean of the Drake Passage. Measured fluxes are directed orthogonal to both mountain ranges, consistent with an orographic source mechanism, and are largest in winter. Further, our measurements of wave group velocity vectors show clear observational evidence that these waves are strongly focused into the polar night wind jet, and thus may contribute significantly to the "missing momentum" at these latitudes. These results demonstrate the capabilities of our new method, which provides a powerful tool for delivering the observations required for the next generation of weather and climate models.

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Section: Discussionsupporting

confidence: 92%

Section: Intermittencymentioning

confidence: 99%

Section: Gravity Waves and The Drake Passage Regionmentioning

confidence: 99%

Section: Intermittencymentioning

confidence: 99%

See 2 more Smart Citations

Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

Wright

Hindley

Hoffmann³

et al. 2017

Atmos. Chem. Phys.

112

View full text Add to dashboard Cite

show abstract

“…South Georgia and the Antarctic Peninsula, together with the southern tip of South America, lie in a well-known hotspot of stratospheric gravity wave activity during austral winter, which has been extensively studied both observationally (Eckermann and Preusse, 1999;Jiang et al, 2002;Alexander and Teitelbaum, 2007;Baumgaertner and McDonald, 2007;Hertzog et al, 2008;Alexander et al, 2009;Alexander and Teitelbaum, 2011;Alexander and Grimsdell, 2013;Hindley et al, 2015) and with numerical modelling techniques (Hertzog et al, 2008;Plougonven et al, 2010;Shutts and Vosper, 2011;Hertzog et al, 2012;Sato et al, 2012;Plougonven et al, 2013) in the last decade. These mountainous regions are subjected to a strong wintertime circumpolar flow in the troposphere and stratosphere and, as a result, are major orographic gravity wave sources (e.g.…”

Section: N P Hindley Et Al: a 2-d Stockwell Transform For Airs Gramentioning

confidence: 99%

A two-dimensional Stockwell transform for gravity wave analysis of AIRS measurements

et al. 2016

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Abstract. Gravity waves (GWs) play a crucial role in the dynamics of the earth's atmosphere. These waves couple lower, middle and upper atmospheric layers by transporting and depositing energy and momentum from their sources to great heights. The accurate parameterisation of GW momentum flux is of key importance to general circulation models but requires accurate measurement of GW properties, which has proved challenging. For more than a decade, the nadir-viewing Atmospheric Infrared Sounder (AIRS) aboard NASA's Aqua satellite has made global, two-dimensional (2-D) measurements of stratospheric radiances in which GWs can be detected. However, one problem with current one-dimensional methods for GW analysis of these data is that they can introduce significant unwanted biases. Here, we present a new analysis method that resolves this problem. Our method uses a 2-D Stockwell transform (2DST) to measure GW amplitudes, horizontal wavelengths and directions of propagation using both the along-track and cross-track dimensions simultaneously. We first test our new method and demonstrate that it can accurately measure GW properties in a specified wave field. We then show that by using a new elliptical spectral window in the 2DST, in place of the traditional Gaussian, we can dramatically improve the recovery of wave amplitude over the standard approach. We then use our improved method to measure GW properties and momentum fluxes in AIRS measurements over two regions known to be intense hotspots of GW activity: (i) the Drake Passage/Antarctic Peninsula and (ii) the isolated mountainous island of South Georgia. The significance of our new 2DST method is that it provides more accurate, unbiased and better localised measurements of key GW properties compared to most current methods. The added flexibility offered by the scaling parameter and our new spectral window presented here extend the usefulness of our 2DST method to other areas of geophysical data analysis and beyond.

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Internal gravity waves from atmospheric jets and fronts

2014

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For several decades, jets and fronts have been known from observations to be significant sources of internal gravity waves in the atmosphere. Motivations to investigate these waves have included their impact on tropospheric convection, their contribution to local mixing and turbulence in the upper troposphere, their vertical propagation into the middle atmosphere, and the forcing of its global circulation. While many different studies have consistently highlighted jet exit regions as a favored locus for intense gravity waves, the mechanisms responsible for their emission had long remained elusive: one reason is the complexity of the environment in which the waves appear; another reason is that the waves constitute small deviations from the balanced dynamics of the flow generating them; i.e., they arise beyond our fundamental understanding of jets and fronts based on approximations that filter out gravity waves. Over the past two decades, the pressing need for improving parameterizations of nonorographic gravity waves in climate models that include a stratosphere has stimulated renewed investigations. The purpose of this review is to present current knowledge and understanding on gravity waves near jets and fronts from observations, theory, and modeling, and to discuss challenges for progress in coming years.

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Gravity waves over Antarctica and the Southern Ocean: consistent momentum fluxes in mesoscale simulations and stratospheric balloon observations

Cited by 102 publications

References 39 publications

Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

Exploring gravity wave characteristics in 3-D using a novel S-transform technique: AIRS/Aqua measurements over the Southern Andes and Drake Passage

A two-dimensional Stockwell transform for gravity wave analysis of AIRS measurements

Internal gravity waves from atmospheric jets and fronts

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