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Quaas et al. 2004
Quaas, J., Boucher, O. and Bréon, F.-M. (2004). Aerosol indirect effects in POLDER satellite data and the Laboratoire de Météorologie Dynamique–Zoom (LMDZ) general circulation model. Journal of Geophysical Research 109: doi: 10.1029/2003JD004317. issn: 0148-0227.

The POLDER-1 instrument was able to measure aerosol and cloud properties for eight months in 1996--1997. We use these observational data for aerosol concentration (the aerosol index), cloud optical thickness, and cloud droplet effective radius to establish statistical relationships among these parameters in order to analyze the first and second aerosol indirect effects. We also evaluate the representation of these effects as parameterized in the Laboratoire de M¿t¿orologie Dynamique--Zoom (LMDZ) general circulation model. We find a decrease in cloud top droplet radius with increasing aerosol index in both the model and the observations. Our results are only slightly changed if the analysis is done at fixed cloud liquid water path (LWP) instead of considering all LWP conditions. We also find a positive correlation between aerosol index and cloud liquid water path, which is particularly pronounced over the Northern Hemisphere midlatitudes. This may be interpreted as observational evidence for the second aerosol indirect effect on a large scale. The model-simulated relationship agrees well with that derived from POLDER data. Model simulations show a rather small change in the two relationships if preindustrial rather than present-day aerosol distributions are used. However, when entirely switching off the second aerosol indirect effect in our model, we find a much steeper slope than we do when including it.

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Abstract

Keywords
Atmospheric Composition and Structure, Cloud physics and chemistry, Atmospheric Composition and Structure, Aerosols and particles (0345, 4801), Global Change, Atmosphere (0315, 0325), Global Change, Remote sensing, Hydrology, Anthropogenic effects, indirect effects, aerosol, clouds
Journal
Journal of Geophysical Research
http://www.agu.org/journals/jb/
Publisher
American Geophysical Union
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