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| Titel |
Assessment of aerosol-cloud interactions in the ECHAM6-HAM GCM and the
Aerosol{\_}cci/Cloud{\_}cci (A)ATSR dataset |
| VerfasserIn |
David Neubauer, Ulrike Lohmann, Matthew Christensen, Caroline Poulsen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125850
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| Publikation (Nr.) |
 EGU/EGU2016-5499.pdf |
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| Zusammenfassung |
| Aerosol-cloud interactions (ACI) are uncertain and the estimates of the ACI effective
radiative forcing magnitude show a large variability. Studies using present day variability in
satellite data to infer ACI, or that constrain model parameterizations to better agree with
satellite observations find a less negative ACI radiative forcing than purely model based
studies. Next to the problematic use of present day variability as a substitute for
anthropogenic change, the scale at which the analysis of the responses of cloud
properties to changes in aerosol is done could be a reason for the discrepancy in forcing
estimates if the analysis/observational scales differ substantially from the process scale.
The projects of the Climate Change Initiative (CCI) programme of ESA aim at
producing long time series of satellite data of essential climate variables and give
the opportunity to produce products for susceptibilities of aerosol properties from
Aerosol_cci and cloud properties from Cloud_cci from high resolution datasets.
Within the Aerosol_cci project these susceptibilities derived from high resolution
(A)ATSR datasets with a nearest neighbour approach are compared to susceptibilities
from the global aerosol climate model ECHAM6-HAM. Next to the new satellite
products a relatively fine analysis scale is used and the clouds are separated in different
environmental regimes to reduce smoothing or spurious effects by aggregation of
data.
Susceptibilities and forcing estimates differ between the (A)ATSR datasets
and ECHAM6-HAM with the model showing stronger susceptibilities and ACI
radiative forcing in agreement with previous estimates in the literature. There is a large
difference in susceptibilities between precipitating and non-precipitating clouds in the
satellite as well as the model data but there is no decrease in liquid water path with
increasing aerosol index as has been reported in the literature for A-train satellite
data. The liquid water path susceptibility of ECHAM6-HAM is smaller than in
previous model versions but still larger than susceptibilities derived from satellite data. |
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