What Is the Source of the Stratospheric Gravity Wave Belt in Austral Winter?

Hendricks, Eric A.; Doyle, James D.; Eckermann, Stephen D.; Jiang, Qingfang; Reinecke, P. Alexander

doi:10.1175/jas-d-13-0332.1

Cited by 73 publications

(133 citation statements)

References 34 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: 71%

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: 71%

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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“…Other studies suggest that much of the enhancement is primarily the result of non-orographic wave sources in and around the Southern Ocean (e.g. Hendricks et al, 2014;Preusse et al, 2014). Furthermore, the distribution of increased E p in Fig.…”

Section: Geographic Distribution Of E P In the Southernmentioning

confidence: 73%

“…Despite more than a decade of close observation (e.g. Wu and Waters, 1996;Wu and Jiang, 2002;Ern et al, 2004;Hei et al, 2008; M. J. ; S. P. Yan et al, 2010;Gong et al, 2012;Hendricks et al, 2014;Preusse et al, 2014), its origins are still not incontestably understood.…”

Section: Introductionmentioning

confidence: 99%

“…It has been suggested that gravity waves in this region may have a number of orographic and non-orographic sources, such as the leeward propagation of mountain waves from the southern tip of South America and/or the northern tip of the Antarctic Peninsula (Preusse et al, 2002;Sato et al, 2009Sato et al, , 2012, baroclinic instabilities from tropospheric storm systems (Hendricks et al, 2014;Preusse et al, 2014) or spontaneous adjustment arising independently from, or as a result of, either or both of these primary processes. It is likely that the gravity waves observed in this region are a result of some or all of these processes overlapping in spatial and temporal regions.…”

Section: Introductionmentioning

confidence: 99%

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The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO

et al. 2015

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Abstract. Nearly all general circulation models significantly fail to reproduce the observed behaviour of the southern wintertime polar vortex. It has been suggested that these biases result from an underestimation of gravity wave drag on the atmosphere at latitudes near 60 • S, especially around the "hot spot" of intense gravity wave fluxes above the mountainous Southern Andes and Antarctic peninsula. Here, we use Global Positioning System radio occultation (GPS-RO) data from the COSMIC satellite constellation to determine the properties of gravity waves in the hot spot and beyond. We show considerable southward propagation to latitudes near 60 • S of waves apparently generated over the southern Andes. We propose that this propagation may account for much of the wave drag missing from the models. Furthermore, there is a long leeward region of increased gravity wave energy that sweeps eastwards from the mountains over the Southern Ocean. Despite its striking nature, the source of this region has historically proved difficult to determine. Our observations suggest that this region includes both waves generated locally and orographic waves advected downwind from the hot spot. We describe and use a new wavelet-based analysis technique for the quantitative identification of individual waves from COSMIC temperature profiles. This analysis reveals different geographical regimes of wave amplitude and short-timescale variability in the wave field over the Southern Ocean. Finally, we use the increased numbers of closely spaced pairs of profiles from the deployment phase of the COSMIC constellation in 2006 to make estimates of gravity wave horizontal wavelengths. We show that, given sufficient observations, GPS-RO can produce physically reasonable estimates of stratospheric gravity wave momentum flux in the hot spot that are consistent with measurements made by other techniques. We discuss our results in the context of previous satellite and modelling studies and explain how they advance our understanding of the nature and origins of waves in the southern stratosphere.

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“…1 shows a broad zonal band of stratospheric gravity wave activity around 50-70 • S. A pronounced maximum of gravity wave activity within this latitude band is found leeward of the Andes and the Antarctic Peninsula, extending as far as 150 • E. The origin of this broad maximum is not entirely clear as the region of enhanced activity extends well beyond the reach of the direct effect of orography. It may be caused by propagating mountain waves (Preusse et al, 2002;Sato et al, 2012;Hindley et al, 2015), but also by nonorographic sources in winter storm tracks such as spontaneous adjustment, frontogenesis, and convection (Hendricks et al, 2014;Hindley et al, 2015;Alexander et al, 2016). (Dee et al, 2011) at the AIRS observational level (3 hPa, about 40 km) and at low level (750 hPa, about 2 km).…”

Section: Hotspotmentioning

confidence: 99%

Stratospheric gravity waves at Southern Hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations

2016

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Abstract. Stratospheric gravity waves from small-scale orographic sources are currently not well-represented in general circulation models. This may be a reason why many simulations have difficulty reproducing the dynamical behavior of the Southern Hemisphere polar vortex in a realistic manner. Here we discuss a 12-year record (2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014) of stratospheric gravity wave activity at Southern Hemisphere orographic hotspots as observed by the Atmospheric InfraRed Sounder (AIRS) aboard the National Aeronautics and Space Administration's (NASA) Aqua satellite. We introduce a simple and effective approach, referred to as the "two-box method", to detect gravity wave activity from infrared nadir sounder measurements and to discriminate between gravity waves from orographic and other sources. From austral midfall to mid-spring (April-October) the contributions of orographic sources to the observed gravity wave occurrence frequencies were found to be largest for the Andes (90 %), followed by the Antarctic Peninsula (76 %), Kerguelen Islands (73 %), Tasmania (70 %), New Zealand (67 %), Heard Island (60 %), and other hotspots (24-54 %). Mountain wave activity was found to be closely correlated with peak terrain altitudes, and with zonal winds in the lower troposphere and mid-stratosphere. We propose a simple model to predict the occurrence of mountain wave events in the AIRS observations using zonal wind thresholds at 3 and 750 hPa. The model has significant predictive skill for hotspots where gravity wave activity is primarily due to orographic sources. It typically reproduces seasonal variations of the mountain wave occurrence frequencies at the Antarctic Peninsula and Kerguelen Islands from near zero to over 60 % with mean absolute errors of 4-5 percentage points. The prediction model can be used to disentangle upper level wind effects on observed occurrence frequencies from low-level source and other influences. The data and methods presented here can help to identify interesting case studies in the vast amount of AIRS data, which could then be further explored to study the specific characteristics of stratospheric gravity waves from orographic sources and to support model validation.

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What Is the Source of the Stratospheric Gravity Wave Belt in Austral Winter?

Cited by 73 publications

References 34 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

The southern stratospheric gravity wave hot spot: individual waves and their momentum fluxes measured by COSMIC GPS-RO

Stratospheric gravity waves at Southern Hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations

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