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| Titel |
Aerosol light-scattering enhancement due to water uptake during the TCAP campaign |
| VerfasserIn |
G. Titos, A. Jefferson, P. J. Sheridan, E. Andrews, H. Lyamani, L. Alados-Arboledas, J. A. Ogren |
| 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 ; 14, no. 13 ; Nr. 14, no. 13 (2014-07-10), S.7031-7043 |
| Datensatznummer |
250118878
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| Publikation (Nr.) |
 copernicus.org/acp-14-7031-2014.pdf |
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| Zusammenfassung |
| Aerosol optical properties were measured by the DOE/ARM (US Department of
Energy Atmospheric Radiation Measurements) Program Mobile Facility during
the Two-Column Aerosol Project (TCAP) campaign deployed at Cape Cod,
Massachusetts, for a 1-year period (from summer 2012 to summer 2013).
Measured optical properties included aerosol light-absorption coefficient
(σap) at low relative humidity (RH) and aerosol
light-scattering coefficient (σsp) at low and at RH values
varying from 30 to 85%, approximately. Calculated variables included the
single scattering albedo (SSA), the scattering Ångström exponent
(SAE) and the scattering enhancement factor (f(RH)). Over the period of
measurement, f(RH = 80%) had a mean value of 1.9 ± 0.3 and
1.8 ± 0.4 in the PM10 and PM1 fractions, respectively.
Higher f(RH = 80%) values were observed for wind directions from
0 to 180° (marine sector) together with high SSA and low SAE
values. The wind sector from 225 to 315° was identified as
an anthropogenically influenced sector, and it was characterized by smaller,
darker and less hygroscopic aerosols. For the marine sector, f(RH = 80%)
was 2.2 compared with a value of 1.8 obtained for the
anthropogenically influenced sector. The air-mass backward trajectory
analysis agreed well with the wind sector analysis. It shows low cluster to
cluster variability except for air masses coming from the Atlantic Ocean
that showed higher hygroscopicity. Knowledge of the effect of RH on aerosol
optical properties is of great importance for climate forcing calculations
and for comparison of in situ measurements with satellite and remote sensing
retrievals. In this sense, predictive capability of f(RH) for use in climate
models would be enhanced if other aerosol parameters could be used as
proxies to estimate hygroscopic growth. Toward this goal, we propose an
exponential equation that successfully estimates aerosol hygroscopicity as a
function of SSA at Cape Cod. Further work is needed to determine if the
equation obtained is valid in other environments. |
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