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| Titel |
The contribution of the strength and structure of extratropical cyclones to observed cloud–aerosol relationships |
| VerfasserIn |
B. S. Grandey, P. Stier, R. G. Grainger, T. M. Wagner |
| 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. 21 ; Nr. 13, no. 21 (2013-11-04), S.10689-10701 |
| Datensatznummer |
250085787
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| Publikation (Nr.) |
 copernicus.org/acp-13-10689-2013.pdf |
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| Zusammenfassung |
| Meteorological conditions may drive relationships between aerosol and
cloud-related properties. It is important to account for the meteorological
contribution to observed cloud–aerosol relationships in order to improve
understanding of aerosol–cloud–climate interactions. A new method of
investigating the contribution of meteorological covariation to observed
cloud–aerosol relationships is introduced. Other studies have investigated
the contribution of local meteorology to cloud–aerosol relationships. In
this paper, a complimentary large-scale view is presented. Extratropical
cyclones have been previously shown to affect satellite-retrieved aerosol
optical depth (τ), due to enhanced emission of sea salt and sea surface
brightness artefacts in regions of higher wind speed. Extratropical cyclones
have also been shown to affect cloud-related properties such as cloud
fraction (fc) and cloud top temperature (Ttop).
Therefore, it seems plausible to hypothesise that extratropical cyclones may
drive relationships between cloud-related properties and τ. In this
paper, this hypothesis is investigated for extratropical cyclones, henceforth
referred to as storms, over the Atlantic Ocean. MODerate resolution Imaging
Spectroradiometer (MODIS) retrieved τ, fc and Ttop
data are analysed using a storm-centric coordinate system centred on
extratropical cyclones which have been tracked using European Centre for
Medium Range Weather Forecasts (ECMWF) reanalysis 850 hPa relative vorticity
data. The tracked relative vorticity (ω) is used as a measure of storm
strength, while position in the storm-centric domain is used to account for
storm structure. Relationships between the cloud-related properties and
τ are measured by calculating regression slopes and correlations. The
fc–τ relationships are positive, while the
Ttop–τ relationships are negative. By shuffling the pairing
of the cloud and τ data at each location in the storm-centric domain and
within narrow ω bins, the contribution of storm strength and storm
structure to the observed relationships can be investigated. It is found that
storm strength and storm structure can explain only a small component of the
relationships observed in the MODIS data. The primary causes for observed
cloud–aerosol relationships are likely to be other factors such as retrieval
errors, local meteorology or aerosol–cloud interactions. |
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