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| Titel |
JURASSIC Retrieval Processing |
| VerfasserIn |
J. Blank, J. Ungermann, T. Guggenmoser, M. Kaufmann, M. Riese |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250070693
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| Zusammenfassung |
| The Gimballed Limb Observer for Radiance Imaging in the Atmosphere (GLORIA) is an
aircraft based infrared limb-sounder. This presentation will give an overview of the retrieval
techniques used for the analysis of data produced by the GLORIA instrument. For data
processing, the JUelich RApid Spectral SImulation Code 2 (JURASSIC2) was
developed. It consists of a set of programs to retrieve atmospheric profiles from GLORIA
measurements.
The GLORIA Michelson interferometer can run with a wide range of parameters. In
the dynamics mode, spectra are generate with a medium spectral and a very high
temporal and spatial resolution. Each sample can contain thousands of spectral lines for
each contributing trace gas. In the JURASSIC retrieval code this is handled by
using a radiative transport model based on the Emissivity Growth Approximation.
Deciding which samples should be included in the retrieval is a non-trivial task and
requires specific domain knowledge. To ease this problem we developed an automatic
selection program by analysing the Shannon information content. By taking into
account data for all relevant trace gases and instrument effects, optimal integrated
spectral windows are computed. This includes considerations for cross-influence of
trace gases, which has non-obvious consequence for the contribution of spectral
samples. We developed methods to assess the influence of spectral windows on the
retrieval. While we can not exhaustively search the whole range of possible spectral
sample combinations, it is possible to optimize information content using a genetic
algorithm.
The GLORIA instrument is mounted with a viewing direction perpendicular to the flight
direction. A gimbal frame makes it possible to move the instrument 45° to both direction. By
flying on a circular path, it is possible to generate images of an area of interest from a
wide range of angles. These can be analyzed in a 3D-tomographic fashion, which
yields superior spatial resolution along line of site. Usually limb instruments have a
resolution of several hundred kilometers. In studies we have shown to get a resolution
of 35km in all horizontal directions. Even when only linear flight patterns can be
realized, resolutions of -70km can be obtained. This technique can be used to
observe features of the Upper Troposphere Lower Stratosphere (UTLS), where
important mixing processes take place. Especially tropopause folds are difficult to
image, as their main features need to be along line of flight when using common 1D
approach. |
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