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| Titel |
Aerosol spectral absorption in the Mexico City area: results from airborne measurements during MILAGRO/INTEX B |
| VerfasserIn |
R. W. Bergstrom, K. S. Schmidt, O. Coddington, P. Pilewskie, H. Guan, J. M. Livingston, J. Redemann, P. B. Russell |
| 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 ; 10, no. 13 ; Nr. 10, no. 13 (2010-07-13), S.6333-6343 |
| Datensatznummer |
250008620
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| Publikation (Nr.) |
 copernicus.org/acp-10-6333-2010.pdf |
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| Zusammenfassung |
This paper presents estimates of the spectral solar absorption due to
atmospheric aerosols during the 2006 MILAGRO/INTEX-B (Megacity
Initiative-Local And Global Research Observations/Phase B of the
Intercontinental Chemical Transport Experiment) field campaign. The aerosol
absorption was derived from measurements of the spectral solar radiation and
the spectral aerosol optical depth made on the J31 aircraft flying over the
Gulf of Mexico and over Mexico City. We present the spectral single
scattering albedo (SSA) and aerosol absorption optical depth (AAOD) for two
flights over the Gulf of Mexico and three flights over Mexico City for
wavelengths from 350 to approximately 1650 nm. The spectral aerosol optical
properties of each case are different and illustrate the variability of the
aerosol optical properties in the Mexico City area.
The results can be described in terms of three different wavelength regions:
The 350–500 nm region where the aerosol absorption often falls off sharply
presumably due to organic carbonaceous particles and windblown dust; the
500–1000 nm region where the decrease with wavelength is slower presumably due
to black carbon; and the near infrared spectral region (1000 nm to 1650 nm)
where it is difficult to obtain reliable results since the aerosol
absorption is relatively small and the gas absorption dominates. However,
there is an indication of a small and somewhat wavelength independent
absorption in the region beyond 1000 nm.
For one of the flights over the Gulf of Mexico near the coastline it appears
that a cloud/fog formation and evaporation led to an increase of absorption
possibly due to a water shell remaining on the particles after the cloud/fog
had dissipated. For two of the Mexico City cases, the single scattering
albedo is roughly constant between 350–500 nm consistent with other Mexico
City results. In three of the cases a single absorption Angstrom exponent
(AAE) fits the aerosol absorption optical depth over the entire wavelength
range of 350 to 1650 nm relatively well (r2> 0.86). |
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