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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 7
Atmos. Meas. Tech., 11, 4327-4344, 2018
https://doi.org/10.5194/amt-11-4327-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue: Sources, propagation, dissipation and impact of gravity waves...

Atmos. Meas. Tech., 11, 4327-4344, 2018
https://doi.org/10.5194/amt-11-4327-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Jul 2018

Research article | 23 Jul 2018

Limited angle tomography of mesoscale gravity waves by the infrared limb-sounder GLORIA

Isabell Krisch1, Jörn Ungermann1, Peter Preusse1, Erik Kretschmer2, and Martin Riese1 Isabell Krisch et al.
  • 1Forschungszentrum Jülich, Institute of Energy- and Climate Research, Stratosphere (IEK-7), Jülich, Germany
  • 2Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany

Abstract. Three-dimensional measurements of gravity waves are required in order to quantify their direction-resolved momentum fluxes and obtain a better understanding of their propagation characteristics. Such 3-D measurements of gravity waves in the lowermost stratosphere have been provided by the airborne Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) using full angle tomography. Closed flight patterns of sufficient size are needed to acquire the full set of angular measurements for full angle tomography. These take about 2h and are not feasible everywhere due to scientific reasons or air traffic control restrictions. Hence, this paper investigates the usability of limited angle tomography for gravity wave research based on synthetic observations. Limited angle tomography uses only a limited set of angles for tomographic reconstruction and can be applied to linear flight patterns. A synthetic end-to-end simulation has been performed to investigate the sensitivity of limited angle tomography to gravity waves with different wavelengths and orientations with respect to the flight path. For waves with wavefronts roughly perpendicular to the flight path, limited angle tomography and full angle tomography can derive wave parameters like wavelength, amplitude, and wave orientation with similar accuracy. For waves with a horizontal wavelength above 200km and vertical wavelength above 3km, the wavelengths can be retrieved with less than 10% error, the amplitude with less than 20% error, and the horizontal wave direction with an error below 10°. This is confirmed by a comparison of results obtained from full angle tomography and limited angle tomography for real measurements taken on 25 January 2016 over Iceland. The reproduction quality of gravity wave parameters with limited angle tomography, however, depends strongly on the orientation of the waves with respect to the flight path. Thus, full angle tomography might be preferable in cases in which the orientation of the wave cannot be predicted or waves with different orientations exist in the same volume and thus the flight path cannot be adjusted accordingly. Also, for low-amplitude waves and short-scale waves full angle tomography has advantages due to its slightly higher resolution and accuracy.

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Three-dimensional temperature measurements of the atmosphere are required to address current research questions concerning the propagation of gravity waves. Limited angle tomography (LAT) with measurements from an airborne infrared limb imager can provide such 3-D temperature measurements. Wave parameters derived from such LAT measurements achieve an accuracy similar to that derived from full angle tomography, if the orientation of the flight path is optimized with respect to the gravity wave.
Three-dimensional temperature measurements of the atmosphere are required to address current...
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