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| Titel |
The magnitude and causes of uncertainty in global model simulations of cloud condensation nuclei |
| VerfasserIn |
L. A. Lee, K. J. Pringle, C. L. Reddington, G. W. Mann, P. Stier, D. V. Spracklen, J. R. Pierce, K. S. Carslaw |
| 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. 17 ; Nr. 13, no. 17 (2013-09-05), S.8879-8914 |
| Datensatznummer |
250085677
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| Publikation (Nr.) |
 copernicus.org/acp-13-8879-2013.pdf |
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| Zusammenfassung |
| Aerosol–cloud interaction effects are a major source of uncertainty in
climate models so it is important to quantify the sources of uncertainty and
thereby direct research efforts. However, the computational expense of global
aerosol models has prevented a full statistical analysis of their outputs.
Here we perform a variance-based analysis of a global 3-D aerosol
microphysics model to quantify the magnitude and leading causes of parametric
uncertainty in model-estimated present-day concentrations of cloud
condensation nuclei (CCN). Twenty-eight model parameters covering essentially
all important aerosol processes, emissions and representation of aerosol size
distributions were defined based on expert elicitation. An uncertainty
analysis was then performed based on a Monte Carlo-type sampling of an
emulator built for each model grid cell. The standard deviation around the
mean CCN varies globally between about ±30% over some marine regions to
±40–100% over most land areas and high latitudes, implying that aerosol
processes and emissions are likely to be a significant source of uncertainty
in model simulations of aerosol–cloud effects on climate. Among the most
important contributors to CCN uncertainty are the sizes of emitted primary
particles, including carbonaceous combustion particles from wildfires,
biomass burning and fossil fuel use, as well as sulfate particles formed on
sub-grid scales. Emissions of carbonaceous combustion particles affect CCN
uncertainty more than sulfur emissions. Aerosol emission-related parameters
dominate the uncertainty close to sources, while uncertainty in aerosol
microphysical processes becomes increasingly important in remote regions,
being dominated by deposition and aerosol sulfate formation during
cloud-processing. The results lead to several recommendations for research
that would result in improved modelling of cloud–active aerosol on a global
scale. |
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