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| Titel |
Aerosol's optical and physical characteristics and direct radiative forcing during a shamal dust storm, a case study |
| VerfasserIn |
T. M. Saeed, H. Al-Dashti, C. Spyrou |
| 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 ; 14, no. 7 ; Nr. 14, no. 7 (2014-04-14), S.3751-3769 |
| Datensatznummer |
250118585
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| Publikation (Nr.) |
 copernicus.org/acp-14-3751-2014.pdf |
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| Zusammenfassung |
| Dust aerosols are analyzed for their optical and physical properties during
an episode of a dust storm that blew over Kuwait on 26 March 2003 when the military Operation Iraqi
Freedom was in full swing. The intensity of the dust
storm was such that it left a thick suspension of dust throughout the
following day, 27 March. The synoptic sequence leading to the dust storm and
the associated wind fields are discussed. Ground-based measurements of
aerosol optical thickness reached 3.617 and 4.17 on 26 and 27 March respectively
while the Ångstrom coefficient, α870/440, dropped to −0.0234
and −0.0318. Particulate matter concentration of 10 μm diameter or
less, PM10, peaked at 4800 μg m−3 during dust storm hours of 26
March. Moderate Resolution Imaging Spectroradiometer (MODIS) retrieved
aerosol optical depth (AOD) by Deep Blue algorithm and Total Ozone Mapping
Spectrometer (TOMS) aerosol index (AI) exhibited high values.
Latitude–longitude maps of AOD and AI were used to deduce source regions of
dust transport over Kuwait. The vertical profile of the dust layer was
simulated using the SKIRON atmospheric model. Instantaneous net direct radiative
forcing is calculated at top of atmosphere (TOA) and surface level. The
thick dust layer of 26 March resulted in cooling the TOA by −60 Wm−2
and surface level by −175 Wm−2 for a surface albedo of 0.35. Slightly
higher values were obtained for 27 March due to the increase in aerosol
optical thickness. Radiative heating/cooling rates in the shortwave and
longwave bands were also examined. Shortwave heating rate reached a maximum
value of 2 K day−1 between 3 and 5 km, dropped to
1.5 K day−1 at 6 km and diminished at 8 km. Longwave
radiation initially heated the lower atmosphere by a maximum value of
0.2 K day−1 at surface level, declined sharply at
increasing altitude and diminished at 4 km. Above 4 km longwave radiation
started to cool the atmosphere slightly reaching a maximum rate of
−0.1 K day−1 at 6 km. |
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