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| Titel |
Evaluation of simulated aerosol properties with the aerosol-climate model ECHAM5-HAM using observations from the IMPACT field campaign |
| VerfasserIn |
G.-J. Roelofs, H. Brink, A. Kiendler-Scharr, G. Leeuw, A. Mensah, A. Minikin, R. Otjes |
| 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. 16 ; Nr. 10, no. 16 (2010-08-19), S.7709-7722 |
| Datensatznummer |
250008715
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| Publikation (Nr.) |
 copernicus.org/acp-10-7709-2010.pdf |
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| Zusammenfassung |
| In May 2008, the measurement campaign IMPACT for observation of atmospheric
aerosol and cloud properties was conducted in Cabauw, The Netherlands. With
a nudged version of the coupled aerosol-climate model ECHAM5-HAM we simulate
the size distribution and chemical composition of the aerosol and the
associated aerosol optical thickness (AOT) for the campaign period. Synoptic
scale meteorology is represented realistically through nudging of the
vorticity, the divergence, the temperature and the surface pressure.
Simulated concentrations of aerosol sulfate and organics at the surface are
generally within a factor of two from observed values. The monthly averaged
AOT from the model is 0.33, about 20% larger than observed. For selected
periods of the month with relatively dry and moist conditions discrepancies
are approximately −30% and +15%, respectively. Discrepancies during
the dry period are partly caused by inaccurate representation of boundary
layer (BL) dynamics by the model affecting the simulated AOT. The model
simulates too strong exchange between the BL and the free troposphere,
resulting in weaker concentration gradients at the BL top than observed for
aerosol and humidity, while upward mixing from the surface layers into the
BL appears to be underestimated. The results indicate that beside aerosol
sulfate and organics also aerosol ammonium and nitrate significantly
contribute to aerosol water uptake. The simulated day-to-day variability of
AOT follows synoptic scale advection of humidity rather than particle
concentration. Even for relatively dry conditions AOT appears to be strongly
influenced by the diurnal cycle of RH in the lower boundary layer, further
enhanced by uptake and release of nitric acid and ammonia by aerosol water. |
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