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| Titel |
Spatial and temporal distribution of atmospheric aerosols in the lowermost troposphere over the Amazonian tropical rainforest |
| VerfasserIn |
R. Krejci, J. Ström, M. Reus, J. Williams, H. Fischer, M. O. Andreae, H.-C. Hansson |
| 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 ; 5, no. 6 ; Nr. 5, no. 6 (2005-06-17), S.1527-1543 |
| Datensatznummer |
250002903
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| Publikation (Nr.) |
 copernicus.org/acp-5-1527-2005.pdf |
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| Zusammenfassung |
| We present measurements of aerosol physico-chemical properties below 5 km
altitude over the tropical rain forest and the marine boundary layer (MBL)
obtained during the LBA-CLAIRE 1998 project. The MBL aerosol size
distribution some 50-100km of the coast of French Guyana and Suriname
showed a bi-modal shape typical of aged and cloud processed aerosol. The
average particle number density in the MBL was 383cm-3. The daytime
mixed layer height over the rain forest for undisturbed conditions was
estimated to be between 1200-1500m. During the morning hours the height
of the mixed layer increased by 144-180mh-1. The median daytime
aerosol number density in the mixed layer increased from 450cm-3 in
the morning to almost 800cm-3 in the late afternoon. The evolution of
the aerosol size distribution in the daytime mixed layer over the rain
forest showed two distinct patterns. Between dawn and midday, the Aitken
mode particle concentrations increased, whereas later during the day, a
sharp increase of the accumulation mode aerosol number densities was
observed, resulting in a doubling of the morning accumulation mode
concentrations from 150cm-3 to 300cm-3. Potential sources of the
Aitken mode particles are discussed here including the rapid growth of
ultrafine aerosol particles formed aloft and subsequently entrained into the
mixed layer, as well as the contribution of emissions from the tropical
vegetation to Aitken mode number densities. The observed increase of the
accumulation mode aerosol number densities is attributed to the combined
effect of: the direct emissions of primary biogenic particles from the rain
forest and aerosol in-cloud processing by shallow convective clouds. Based
on the similarities among the number densities, the size distributions and
the composition of the aerosol in the MBL and the nocturnal residual layer
we propose that the air originating in the MBL is transported above the
nocturnal mixed layer up to 300-400km inland over the rain forest by
night without significant processing. |
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