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| Titel |
Indirect estimation of absorption properties for fine aerosol particles using AATSR observations: a case study of wildfires in Russia in 2010 |
| VerfasserIn |
E. Rodríguez, P. Kolmonen, T. H. Virtanen, L. Sogacheva, A.-M. Sundström, G. de Leeuw |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-03), S.3075-3085 |
| Datensatznummer |
250116516
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| Publikation (Nr.) |
 copernicus.org/amt-8-3075-2015.pdf |
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| Zusammenfassung |
| The Advanced Along-Track Scanning Radiometer (AATSR) on board the ENVISAT
satellite is used to study aerosol properties. The retrieval of aerosol
properties from satellite data is based on the optimized fit of simulated and
measured reflectances at the top of the atmosphere (TOA). The simulations are
made using a radiative transfer model with a variety of representative
aerosol properties. The retrieval process utilizes a combination of four
aerosol components, each of which is defined by their (lognormal) size
distribution and a complex refractive index: a weakly and a strongly
absorbing fine-mode component, coarse mode sea salt aerosol and coarse mode
desert dust aerosol). These components are externally mixed to provide the
aerosol model which in turn is used to calculate the aerosol optical depth
(AOD). In the AATSR aerosol retrieval algorithm, the mixing of these
components is decided by minimizing the error function given by the sum of
the differences between measured and calculated path radiances at 3–4
wavelengths, where the path radiances are varied by varying the aerosol
component mixing ratios. The continuous variation of the fine-mode components
allows for the continuous variation of the fine-mode aerosol absorption.
Assuming that the correct aerosol model (i.e. the correct mixing fractions
of the four components) is selected during the retrieval process, also other
aerosol properties could be computed such as the single scattering albedo
(SSA). Implications of this assumption regarding the ratio of the
weakly/strongly absorbing fine-mode fraction are investigated in this paper
by evaluating the validity of the SSA thus obtained. The SSA is indirectly
estimated for aerosol plumes with moderate-to-high AOD resulting from
wildfires in Russia in the summer of 2010. Together with the AOD, the SSA
provides the aerosol absorbing optical depth (AAOD). The results are compared
with AERONET data, i.e. AOD level 2.0 and SSA and AAOD inversion products.
The RMSE (root mean square error) is 0.03 for SSA and 0.02 for AAOD lower
than 0.05. The SSA is further evaluated by comparison with the SSA retrieved
from the Ozone Monitoring Instrument (OMI). The SSA retrieved from both
instruments show similar features, with generally lower AATSR-estimated SSA
values over areas affected by wildfires. |
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