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| Titel |
Characteristics and direct radiative effect of mid-latitude continental aerosols: the ARM case |
| VerfasserIn |
M. G. Iziomon, U. Lohmann |
| 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 ; 3, no. 6 ; Nr. 3, no. 6 (2003-11-03), S.1903-1917 |
| Datensatznummer |
250001331
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| Publikation (Nr.) |
 copernicus.org/acp-3-1903-2003.pdf |
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| Zusammenfassung |
| A multi-year field measurement analysis of the characteristics and direct radiative effect of
aerosols at the Southern Great Plains (SGP) central facility of the Atmospheric Radiation
Measurement (ARM) Program is presented. Inter-annual mean and standard deviation of
submicrometer scattering fraction (at 550 nm) and Ångström exponent å
(450 nm, 700 nm) at the mid-latitude continental site are indicative of the scattering dominance of fine mode
aerosol particles, being 0.84±0.03 and 2.25±0.09, respectively. We attribute the diurnal
variation of submicron aerosol concentration to coagulation, photochemistry and the evolution
of the boundary layer. Precipitation does not seem to play a role in the observed afternoon
maximum in aerosol concentration. Submicron aerosol mass at the site peaks in the summer
(12.1±6.7mg
m-3), with the summer value being twice that in the winter. Of the chemically
analyzed ionic components (which exclude carbonaceous aerosols), SO4=
and NH4+ constitute the dominant species at the SGP seasonally, contributing
23-30% and 9-12% of the submicron aerosol mass, respectively. Although a minor species, there is a notable rise in
NO3- mass fraction in winter. We contrast the optical properties of dust and smoke haze. The
single scattering albedo w0 shows the most remarkable distinction between the two aerosol
constituents. We also present aircraft measurements of vertical profiles of aerosol optical
properties at the site. Annually, the lowest 1.2 km contributes 70% to the column total light
scattering coefficient. Column-averaged and surface annual mean values of hemispheric
backscatter fraction (at 550 nm), w0
(at 550 nm) and å (450 nm, 700 nm) agree to within 5% in 2001. Aerosols produce a net cooling (most pronounced in the spring) at the ARM site |
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