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| Titel |
The invigoration of deep convective clouds over the Atlantic: aerosol effect, meteorology or retrieval artifact? |
| VerfasserIn |
I. Koren, G. Feingold, L. A. Remer |
| 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. 18 ; Nr. 10, no. 18 (2010-09-20), S.8855-8872 |
| Datensatznummer |
250008783
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| Publikation (Nr.) |
 copernicus.org/acp-10-8855-2010.pdf |
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| Zusammenfassung |
| Associations between cloud properties and aerosol loading are frequently
observed in products derived from satellite measurements. These observed
trends between clouds and aerosol optical depth suggest aerosol modification
of cloud dynamics, yet there are uncertainties involved in satellite
retrievals that have the potential to lead to incorrect conclusions. Two of
the most challenging problems are addressed here: the potential for
retrieved aerosol optical depth to be cloud-contaminated, and as a result,
artificially correlated with cloud parameters; and the potential for
correlations between aerosol and cloud parameters to be erroneously
considered to be causal. Here these issues are tackled directly by studying
the effects of the aerosol on convective clouds in the tropical Atlantic
Ocean using satellite remote sensing, a chemical transport model, and a
reanalysis of meteorological fields. Results show that there is a robust
positive correlation between cloud fraction or cloud top height and the
aerosol optical depth, regardless of whether a stringent filtering of
aerosol measurements in the vicinity of clouds is applied, or not. These
same positive correlations emerge when replacing the observed aerosol field
with that derived from a chemical transport model. Model-reanalysis data is
used to address the causality question by providing meteorological context
for the satellite observations. A correlation exercise between the full
suite of meteorological fields derived from model reanalysis and
satellite-derived cloud fields shows that observed cloud top height and
cloud fraction correlate best with model pressure updraft velocity and
relative humidity. Observed aerosol optical depth does correlate with
meteorological parameters but usually different parameters from those that
correlate with observed cloud fields. The result is a near-orthogonal
influence of aerosol and meteorological fields on cloud top height and cloud
fraction. The results strengthen the case that the aerosol does play a role
in invigorating convective clouds. |
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