A global view of stratospheric gravity wave hotspots located with Atmospheric Infrared Sounder observations

Abstract. Gravity waves are an important driver for the atmospheric circulation and have substantial impact on weather and climate. Satellite instruments offer excellent opportunities to study gravity waves on a global scale. This study focuses on observations from the Atmospheric Infrared Sounder (AIRS) onboard the National Aeronautics and Space Administration Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the European MetOp satellites. The main aim of this study is an intercomparison of stratospheric gravity wave observations of both instruments. In particular, we analyzed AIRS and IASI 4.3 μm brightness temperature measurements, which directly relate to stratospheric temperature. Three case studies showed that AIRS and IASI provide a clear and consistent picture of the temporal development of individual gravity wave events. Statistical comparisons based on a 5-year period of measurements (2008–2012) showed similar spatial and temporal patterns of gravity wave activity. However, the statistical comparisons also revealed systematic differences of variances between AIRS and IASI that we attribute to the different spatial measurement characteristics of both instruments. We also found differences between day- and nighttime data that are partly due to the local time variations of the gravity wave sources. While AIRS has been used successfully in many previous gravity wave studies, IASI data are applied here for the first time for that purpose. Our study shows that gravity wave observations from different hyperspectral infrared sounders such as AIRS and IASI can be directly related to each other, if instrument-specific characteristics such as different noise levels and spatial resolution and sampling are carefully considered. The ability to combine observations from different satellites provides an opportunity to create a long-term record, which is an exciting prospect for future climatological studies of stratospheric gravity wave activity.

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Gravity wave variances and propagation derived from AIRS radiances

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-1701-2012 ◽

2012 ◽

Vol 12 (4) ◽

pp. 1701-1720 ◽

Cited By ~ 55

Author(s):

J. Gong ◽

D. L. Wu ◽

S. D. Eckermann

Keyword(s):

Gravity Wave ◽

General Circulation ◽

Deep Convection ◽

General Circulation Models ◽

Satellite Orbits ◽

Atmospheric Infrared Sounder ◽

Quasi Biennial Oscillation ◽

Mountain Ranges ◽

The Tropics ◽

Cross Track

Abstract. As the first gravity wave (GW) climatology study using nadir-viewing infrared sounders, 50 Atmospheric Infrared Sounder (AIRS) radiance channels are selected to estimate GW variances at pressure levels between 2–100 hPa. The GW variance for each scan in the cross-track direction is derived from radiance perturbations in the scan, independently of adjacent scans along the orbit. Since the scanning swaths are perpendicular to the satellite orbits, which are inclined meridionally at most latitudes, the zonal component of GW propagation can be inferred by differencing the variances derived between the westmost and the eastmost viewing angles. Consistent with previous GW studies using various satellite instruments, monthly mean AIRS variance shows large enhancements over meridionally oriented mountain ranges as well as some islands at winter hemisphere high latitudes. Enhanced wave activities are also found above tropical deep convective regions. GWs prefer to propagate westward above mountain ranges, and eastward above deep convection. AIRS 90 field-of-views (FOVs), ranging from +48° to −48° off nadir, can detect large-amplitude GWs with a phase velocity propagating preferentially at steep angles (e.g., those from orographic and convective sources). The annual cycle dominates the GW variances and the preferred propagation directions for all latitudes. Indication of a weak two-year variation in the tropics is found, which is presumably related to the Quasi-biennial oscillation (QBO). AIRS geometry makes its out-tracks capable of detecting GWs with vertical wavelengths substantially shorter than the thickness of instrument weighting functions. The novel discovery of AIRS capability of observing shallow inertia GWs will expand the potential of satellite GW remote sensing and provide further constraints on the GW drag parameterization schemes in the general circulation models (GCMs).

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Intercomparison of stratospheric gravity wave observations with AIRS and IASI

Atmospheric Measurement Techniques Discussions ◽

10.5194/amtd-7-8415-2014 ◽

2014 ◽

Vol 7 (8) ◽

pp. 8415-8464 ◽

Cited By ~ 1

Author(s):

L. Hoffmann ◽

M. J. Alexander ◽

C. Clerbaux ◽

A. W. Grimsdell ◽

C. I. Meyer ◽

...

Keyword(s):

Gravity Wave ◽

Gravity Waves ◽

Global Scale ◽

Wave Activity ◽

Spatial And Temporal Patterns ◽

Atmospheric Infrared Sounder ◽

Substantial Impact ◽

Stratospheric Temperature ◽

Consistent Picture ◽

Time Variations

Abstract. Gravity waves are an important driver for the atmospheric circulation and have substantial impact on weather and climate. Satellite instruments offer excellent opportunities to study gravity waves on a global scale. This study focuses on observations from the Atmospheric Infrared Sounder (AIRS) onboard the National Aeronautics and Space Administration's Aqua satellite and the Infrared Atmospheric Sounding Interferometer (IASI) onboard the European MetOp satellites. The main aim of this study is an intercomparison of stratospheric gravity wave observations of both instruments. In particular, we analyzed AIRS and IASI 4.3 μm brightness temperature measurements, which directly relate to stratospheric temperature. Three case studies showed that AIRS and IASI provide a clear and consistent picture of the temporal development of individual gravity wave events. Statistical comparisons based on a five-year period of measurements (2008–2012) showed similar spatial and temporal patterns of gravity wave activity. However, the statistical comparisons also revealed systematic differences of variances between AIRS and IASI (about 45%) that we attribute to the different spatial measurement characteristics of both instruments. We also found differences between day- and nighttime data (about 30%) that are partly due to the local time variations of the gravity wave sources. While AIRS has been used successfully in many previous gravity wave studies, IASI data are applied here for the first time for that purpose. Our study shows that gravity wave observations from different hyperspectral infrared sounders such as AIRS and IASI can be directly related to each other, if instrument-specific characteristics such as different noise levels and spatial resolution and sampling are carefully considered. The ability to combine observations from different satellites provides an opportunity to create a long-term record, which is an exciting prospect for future climatological studies of stratospheric gravity wave activity.

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Retrieval of stratospheric temperatures from Atmospheric Infrared Sounder radiance measurements for gravity wave studies

Journal of Geophysical Research Atmospheres ◽

10.1029/2008jd011241 ◽

2009 ◽

Vol 114 (D7) ◽

Cited By ~ 83

Author(s):

L. Hoffmann ◽

M. J. Alexander

Keyword(s):

Gravity Wave ◽

Atmospheric Infrared Sounder

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Gravity wave variances and propagation derived from AIRS radiances

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-11691-2011 ◽

2011 ◽

Vol 11 (4) ◽

pp. 11691-11738 ◽

Cited By ~ 2

Author(s):

J. Gong ◽

D. L. Wu ◽

S. D. Eckermann

Keyword(s):

Gravity Wave ◽

General Circulation ◽

Deep Convection ◽

Low Frequency ◽

General Circulation Models ◽

Satellite Orbits ◽

Atmospheric Infrared Sounder ◽

Quasi Biennial Oscillation ◽

Mountain Ranges ◽

Cross Track

Abstract. As the first gravity wave (GW) climatology study using nadir-viewing infrared sounders, 50 Atmospheric Infrared Sounder (AIRS) radiance channels are selected to estimate GW variances at pressure levels between 2–100 hPa. The GW variance for each scan in the cross-track direction is derived from radiance perturbations in the scan, independently of adjacent scans along the orbit. Since the scanning swaths are perpendicular to the satellite orbits, which are inclined meridionally at most latitudes, the zonal component of GW propagation can be inferred by differencing the variances derived between the westmost and the eastmost viewing angles. Consistent with previous GW studies using various satellite instruments, monthly mean AIRS variance shows large enhancements over meridionally oriented mountain ranges as well as some islands at winter hemisphere high latitudes. Enhanced wave activities are also found above tropical deep convective regions. GWs prefer to propagate westward above mountain ranges, and eastward above deep convection. AIRS 90 field-of-views (FOVs), ranging from +48° to −48° off nadir, can detect large-amplitude GWs with a phase velocity propagating preferentially at steep angles (e.g., those from orographic and convective sources). The annual cycle dominates the GW variances and the preferred propagation directions for all latitudes. Quasi-biennial oscillation (QBO) signals are also found in the tropical lower stratosphere despite their small amplitudes. From 90 AIRS FOV radiance measurements, we are able to clearly identify measurement noises, high-frequency internal GWs, and low-frequency inertia GWs. Even though the vertical wavelengths of inertia GWs are shorter than the thickness of instrument weighting functions, simulations support the AIRS sensitivity to these waves. The novel discovery of AIRS capability of observing shallow inertia GWs will expand the potential of satellite GW remote sensing and provide further constraints on the GW drag parameterization schemes in the general circulation models (GCMs).

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