Atmos. Chem. Phys. Discuss., 10, 3893-3936, 2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The invigoration of deep convective clouds over the Atlantic: aerosol effect, meteorology or retrieval artifact?
I. Koren1, G. Feingold2, and L. A. Remer3
1Department of Environmental Science and Energy Research, Weizmann Institute of Science, Rehovot 76100, Israel
2NOAA Earth System Research Laboratory, Boulder, CO, USA
3Laboratory for Atmospheres, NASA Goddard Space Flight Center, Greenbelt, MD, USA

Abstract. The effects of the aerosol on convective clouds in the tropical Atlantic Ocean are explored using satellite remote sensing, a chemical transport model, and a reanalysis of meteorological fields. Two of the most challenging problems are addressed: the potential for elements of the cloud field to be erroneously ascribed to aerosol optical depth; and the potential for correlations between aerosol and cloud parameters to be erroneously considered to be causal. 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. 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 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.

Citation: Koren, I., Feingold, G., and Remer, L. A.: The invigoration of deep convective clouds over the Atlantic: aerosol effect, meteorology or retrieval artifact?, Atmos. Chem. Phys. Discuss., 10, 3893-3936, doi:10.5194/acpd-10-3893-2010, 2010.
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