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| Titel |
Characterization of particle cloud droplet activity and composition in the free troposphere and the boundary layer during INTEX-B |
| VerfasserIn |
G. C. Roberts, D. A. Day, L. M. Russell, E. J. Dunlea, J. L. Jimenez, J. M. Tomlinson, D. R. Collins, Y. Shinozuka, A. D. Clarke |
| 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. 14 ; Nr. 10, no. 14 (2010-07-20), S.6627-6644 |
| Datensatznummer |
250008642
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| Publikation (Nr.) |
 copernicus.org/acp-10-6627-2010.pdf |
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| Zusammenfassung |
| Measurements of cloud condensation nuclei (CCN), aerosol size distributions,
and submicron aerosol composition were made as part of the Intercontinental
Chemical Transport Experiment Phase B (INTEX-B) campaign during spring 2006.
Measurements were conducted from an aircraft platform over the northeastern
Pacific and western North America with a focus on how the transport and
evolution of Asian pollution across the Pacific Ocean affected CCN
properties. A broad range of air masses were sampled and here we focus on
three distinct air mass types defined geographically: the Pacific free
troposphere (FT), the marine boundary layer (MBL), and the polluted
continental boundary layer in the California Central Valley (CCV). These
observations add to the few observations of CCN in the FT. CCN
concentrations showed a large range of concentrations between air masses,
however CCN activity was similar for the MBL and CCV (κ~0.2–0.25). FT
air masses showed evidence of long-range transport from Asia and CCN
activity was consistently higher than for the boundary layer air masses.
Bulk chemical measurements predicted CCN activity reasonably well for the
CCV and FT air masses. Decreasing trends in κ with organic mass fraction were
observed for the combination of the FT and CCV air masses and can be
explained by the measured soluble inorganic chemical components. Changes in
hygroscopicity associated with differences in the non-refractory organic
composition were too small to be distinguished from the simultaneous changes
in inorganic ion composition in the FT and MBL, although measurements for
the large organic fractions (0.6–0.8) found in the CCV showed values of the
organic fraction hygroscopicity consistent with other polluted regions
(κorg~0.1–0.2). A comparison of CCN-derived κ (for particles at the
critical diameter) to H-TDMA-derived κ (for particles at 100 nm diameter)
showed similar trends, however the CCN-derived κ values were significantly
higher. |
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