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| Titel |
Aerosol decadal trends – Part 1: In-situ optical measurements at GAW and IMPROVE stations |
| VerfasserIn |
M. Collaud Coen, E. Andrews, A. Asmi, U. Baltensperger, N. Bukowiecki, D. Day, M. Fiebig, A. M. Fjǽraa, H. Flentje, A. Hyvärinen, A. Jefferson, S. G. Jennings, G. Kouvarakis, H. Lihavainen, C. Lund Myhre, W. C. Malm, N. Mihapopoulos, J. V. Molenar, C. O'Dowd, J. A. Ogren, B. A. Schichtel, P. Sheridan, A. Virkkula, E. Weingärtner, R. Weller, P. Laj |
| 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 ; 13, no. 2 ; Nr. 13, no. 2 (2013-01-22), S.869-894 |
| Datensatznummer |
250017606
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| Publikation (Nr.) |
 copernicus.org/acp-13-869-2013.pdf |
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| Zusammenfassung |
| Currently many ground-based atmospheric stations include in-situ measurements
of aerosol physical and optical properties, resulting in more than 20
long-term (> 10 yr) aerosol measurement sites in the Northern Hemisphere
and Antarctica. Most of these sites are located at remote locations and
monitor the aerosol particle number concentration, wavelength-dependent light
scattering, backscattering, and absorption coefficients. The existence of
these multi-year datasets enables the analysis of long-term trends of these
aerosol parameters, and of the derived light scattering Ångström
exponent and backscatter fraction. Since the aerosol variables are not
normally distributed, three different methods (the seasonal Mann-Kendall test
associated with the Sen's slope, the generalized least squares fit associated
with an autoregressive bootstrap algorithm for confidence intervals, and the
least-mean square fit applied to logarithms of the data) were applied to
detect the long-term trends and their magnitudes. To allow a comparison among
measurement sites, trends on the most recent 10 and 15 yr periods were
calculated. No significant trends were found for the three continental
European sites. Statistically significant trends were found for the two
European marine sites but the signs of the trends varied with aerosol
property and location. Statistically significant decreasing trends for both
scattering and absorption coefficients (mean slope of
−2.0% yr−1) were found for most North American stations,
although positive trends were found for a few desert and high-altitude sites.
The difference in the timing of emission reduction policy for the Europe and
US continents is a likely explanation for the decreasing trends in aerosol
optical parameters found for most American sites compared to the lack of
trends observed in Europe. No significant trends in scattering coefficient
were found for the Arctic or Antarctic stations, whereas the Arctic station
had a negative trend in absorption coefficient. The high altitude Pacific
island station of Mauna Loa presents positive trends for both scattering and
absorption coefficients. |
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