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| Titel |
Spatial distribution of dust's optical properties over the Sahara and Asia inferred from Moderate Resolution Imaging Spectroradiometer |
| VerfasserIn |
M. Yoshida, J. M. Haywood, T. Yokohata, H. Murakami, T. Nakajimae |
| 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. 21 ; Nr. 13, no. 21 (2013-11-07), S.10827-10845 |
| Datensatznummer |
250085797
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| Publikation (Nr.) |
 copernicus.org/acp-13-10827-2013.pdf |
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| Zusammenfassung |
| There is great uncertainty regarding the role of mineral dust aerosols in
Earth's climate system. One reason for this uncertainty is that the
optical properties of mineral dust, such as its single scattering albedo
(the ratio of scattering to total extinction), are poorly constrained
because ground observations are limited to a few locations and satellite
standard products are not available due to the excessively bright surface of
the desert in the visible wavelength, which makes robust retrievals
difficult. Here, we develop a method to estimate the spatial distributions
of the aerosol single scattering albedo (ω0) and optical depth
(τa), with daily 1°×1° spatial resolution using data from
the Moderate Resolution Imaging Spectroradiometer (MODIS) as well as model
simulations of radiative transfer. This approach is based on the "critical
surface reflectance" method developed in the literature, which estimates
ω0 from the top of the atmospheric radiance. We estimate the
uncertainties in ω0 over the Sahara (Asia) to be approximately
0.020 and 0.010 (0.023 and 0.017) for bands 9 and 1, respectively, while the
uncertainty in τa is approximately 0.235 and 0.228 (0.464 and
0.370) for bands 9 and 1, respectively. The 5–95% range of the spatial
distribution of ω0 over the Sahara (Asia) is approximately
0.90–0.94 and 0.96–0.99 (0.87–0.94 and 0.89–0.97) for bands 9 and 1,
respectively, and that of τa over the Sahara (Asia) is
approximately 0.8–1.4 and 0.8–1.7 (0.7–2.0 and 0.7–1.9) for bands 9 and 1,
respectively. The results for the Sahara indicate a good correlation between
ω0 and the surface reflectance, and between ω0 and
τa. However, the relationships between ω0,
τa, and surface reflectance are less clear in Asia than in
the Sahara, and the ω0 values are smaller than those in the
Sahara. The regions with small ω0 values are consistent with the regions
where coal-burning smoke and carbonaceous aerosols
are reported to be transported in previous studies. Because the coal-burning
and carbonaceous aerosols are known to be more absorptive and have smaller
ω0 values than dust aerosols, our results indicate that the
dust aerosols in Asia are contaminated by these anthropogenic aerosols. The
spatial distribution of dust optical properties obtained in our work could
be useful in understanding the role of dust aerosols in Earth's climate
system, most likely through future collaboration with regional and global
modelling studies. |
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