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| Titel |
Characterisation of dust aerosols in the infrared from IASI and comparison with PARASOL, MODIS, MISR, CALIOP, and AERONET observations |
| VerfasserIn |
S. Peyridieu, A. Chédin, V. Capelle, C. Tsamalis, C. Pierangelo, R. Armante, C. Crevoisier, L. Crépeau, M. Siméon, F. Ducos, N. A. Scott |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 12 ; Nr. 13, no. 12 (2013-06-25), S.6065-6082 |
| Datensatznummer |
250018720
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| Publikation (Nr.) |
 copernicus.org/acp-13-6065-2013.pdf |
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| Zusammenfassung |
| Infrared Atmospheric Sounder Interferometer (IASI) observations covering the
period from July 2007 to December 2011 are interpreted in terms of monthly
mean, 1°×1°, 10 μm dust Aerosol Optical Depth
(AOD), mean altitude and coarse mode effective radius. The geographical
study area includes the northern tropical Atlantic and the northwest
Arabian Sea, both characterised by strong, regular dust events. The method
developed relies on the construction of Look-Up-Tables computed for a large
selection of atmospheric situations and observing conditions. At a regional
scale, a good agreement is found between IASI-retrieved 10 μm AOD and
total visible optical depth at 550 nm from either the Moderate resolution
Imaging Spectroradiometer (MODIS/Aqua or Terra), or the Multi-angle Imaging
SpectroRadiometer (MISR), or the Polarization and Anisotropy of Reflectances
for Atmospheric Science coupled with Observations from a Lidar (PARASOL).
Taking into account the ratio existing between infrared and visible AODs,
the diversity between the different 550 nm AODs is similar to the difference
between these and the IASI AODs. The infrared AOD to visible AOD ratio,
partly reflecting the varying distribution of the dust layer between the
dust coarse mode particles seen by IASI, and the fine mode seen by the other
instruments, is found to vary with the region observed with values close to
already published values. Comparisons between the climatologies of the 10 μm
IASI AOD and of the PARASOL non-spherical coarse mode AOD at 865 nm, both
expected to be representative of the dust coarse mode, lead to
conclusions differing according to the region considered. These differences
are discussed in the light of the MODIS Angström exponent (865–550 nm).
At local scale, around six Aerosol Robotic Network (AERONET) sites, close or
far from the dust sources, a similar satisfactory agreement is found between
IASI and the visible AODs and the differences between these products are
shown and analysed. IASI-retrieved dust layer mean altitudes also compare
well with the Cloud-Aerosol Lidar with Orthogonal Polarization
(CALIOP/CALIPSO) aerosol mean layer altitude, both in terms of climatology
and of zonal evolution throughout the Atlantic. Comparisons between the
IASI-retrieved dust coarse mode effective radius and retrievals from AERONET
at the six sites brings into evidence an almost systematic bias of about
+0.35 μm (IASI-AERONET). Removing this bias leads to a satisfactory
agreement between the climatologies of these two products. Overall, these
results illustrate the dust westward transport characterised by a fast
decrease of the dust optical depth, a somewhat slower decrease of the
altitude, and an effective radius remaining almost constant during summer
throughout the northern tropical Atlantic. They also demonstrate the
capability of high resolution infrared sounders to contribute improving our
understanding of processes related to the aerosols (transport, sources,
cycles, effect of aerosols on the terrestrial radiation, etc.). |
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