Global distributions of overlapping gravity waves in HIRDLS data

Osprey, Scott; Gille, J. C.

doi:10.5194/acp-15-8459-2015

Cited by 20 publications

(35 citation statements)

References 48 publications

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“…When assuming that horizontal wave vectors of observed gravity waves are randomly distributed, the average horizontal wave number is underestimated by a factor of √ 2, giving a rough measure of how much shorter observed true horizontal wavelengths could be on average. Similar values for HIRDLS are found by Wright et al (2015).…”

Section: Sensitivity Functions Of Airs and Hirdlssupporting

confidence: 77%

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: Sensitivity Functions Of Airs and Hirdlssupporting

confidence: 77%

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

Meyer¹,

Ern²,

Hoffmann³

et al. 2018

Atmos. Meas. Tech.

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“…At both the highest and lowest altitudes, (i) temperature retrieval accuracy is significantly reduced, (ii) the vertical resolution of the retrieval is also reduced, and (iii) long vertical wavelengths unavoidably experience some edge-truncation due to the limited vertical height window in our analysis (e.g. Wright et al, 2015), with effect (iii) being particularly important. In particular, small regions of northeastwards flux are seen at high and low altitudes at (50 • S, 75 • W); these may be due to (i) limited data quality (ii) our assumption of upward ascent being invalid or (iii) they may genuinely be GWs propagating in a northeastward direction.…”

Section: Momentum Fluxesmentioning

confidence: 91%

“…able is restricted (e.g. Wright et al, 2015), and thus we see a "speckled" pattern of only two values over the great majority of the region, λ z ∼ 14 km and λ z ∼ 18 km. For an orographic GW under the hydrostatic relation (e.g.…”

Section: Wave Amplitudes and Wavelengthsmentioning

confidence: 99%

“…While this is necessary to implement the 3-D ST on our current hardware, we expect that future implementations will be able to use this discarded data to measure distinct overlapping wave signatures, as done in the 2-D case using HIRDLS data by Wright et al (2015). This example is chosen to allow direct comparison with GW measurements from combined AIRS brightness temperatures and MLS kinetic temperatures studied by Wright et al (2016a).…”

Section: Computational Limitationsmentioning

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.

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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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“…V007 of the HIRDLS data set provides vertical temperature profiles from the tropopause to ∼ 80 km in altitude as a function of pressure, allowing us to produce useful gravitywave analyses at these higher altitudes. Measurements have a precision ∼ 0.5 K throughout the stratosphere, decreasing smoothly to ∼ 1 K at the stratopause and 3K or more above this, depending on latitude and season (Khosravi et al, 2009;Gille et al, 2013;Wright et al, 2015). Vertical resolution is ∼ 1 km in the stratosphere, rising smoothly between ∼ 60 and ∼ 70 to ∼ 2 km.…”

Section: Hirdlsmentioning

confidence: 99%

Multi-instrument gravity-wave measurements over Tierra del Fuego and the Drake Passage – Part 1: Potential energies and vertical wavelengths from AIRS, COSMIC, HIRDLS, MLS-Aura, SAAMER, SABER and radiosondes

2016

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Abstract. Gravity waves in the terrestrial atmosphere are a vital geophysical process, acting to transport energy and momentum on a wide range of scales and to couple the various atmospheric layers. Despite the importance of these waves, the many studies to date have often exhibited very dissimilar results, and it remains unclear whether these differences are primarily instrumental or methodological. Here, we address this problem by comparing observations made by a diverse range of the most widely used gravity-wave-resolving instruments in a common geographic region around the southern Andes and Drake Passage, an area known to exhibit strong wave activity. Specifically, we use data from three limbsounding radiometers (Microwave Limb Sounder, MLSAura; HIgh Resolution Dynamics Limb Sounder, HIRDLS; Sounding of the Atmosphere using Broadband Emission Radiometry, SABER), the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) GPS-RO constellation, a ground-based meteor radar, the Advanced Infrared Sounder (AIRS) infrared nadir sounder and radiosondes to examine the gravity wave potential energy (GWPE) and vertical wavelengths (λ z ) of individual gravity-wave packets from the lower troposphere to the edge of the lower thermosphere ( ∼ 100 km). Our results show important similarities and differences. Limb sounder measurements show high intercorrelation, typically > 0.80 between any instrument pair. Meteor radar observations agree in form with the limb sounders, despite vast technical differences. AIRS and radiosonde observations tend to be uncorrelated or anticorrelated with the other data sets, suggesting very different behaviour of the wave field in the different spectral regimes accessed by each instrument. Evidence of wave dissipation is seen, and varies strongly with season. Observed GWPE for individual wave packets exhibits a log-normal distribution, with short-timescale intermittency dominating over a wellrepeated monthly-median seasonal cycle. GWPE and λ z exhibit strong correlations with the stratospheric winds, but not with local surface winds. Our results provide guidance for interpretation and intercomparison of such data sets in their full context.

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Global distributions of overlapping gravity waves in HIRDLS data

Cited by 20 publications

References 48 publications

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

Intercomparison of AIRS and HIRDLS stratospheric gravity wave observations

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

Multi-instrument gravity-wave measurements over Tierra del Fuego and the Drake Passage – Part 1: Potential energies and vertical wavelengths from AIRS, COSMIC, HIRDLS, MLS-Aura, SAAMER, SABER and radiosondes

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