Aerosol and Clouds
Effect of aerosol on trade cumulus cloud morphology
Article first published online: 13 JUN 2009
Copyright 2009 by the American Geophysical Union.
Journal of Geophysical Research: Atmospheres (1984–2012)
Volume 114, Issue D11, 16 June 2009
How to Cite
2009), Effect of aerosol on trade cumulus cloud morphology, J. Geophys. Res., 114, D11209, doi:10.1029/2009JD011750., , and (
- Issue published online: 13 JUN 2009
- Article first published online: 13 JUN 2009
- Manuscript Accepted: 13 APR 2009
- Manuscript Revised: 3 APR 2009
- Manuscript Received: 13 JAN 2009
- effect of aerosol;
- cumulus clouds
 Large-eddy simulations of trade wind cumulus clouds are conducted for clean and polluted aerosol conditions and at a number of different grid sizes to explore (1) the microphysical and morphological responses of fields of cumulus to aerosol perturbations and (2) the robustness of these responses to resolution. Cloud size distributions are shown to be well approximated by a negative power law function indicating that as resolution increases, more and more small clouds are resolved. Cloud fraction in the highest-resolution simulations is 30% higher than in the coarse-resolution simulations. Polluted cloud populations contain higher numbers of smaller clouds than clean cloud populations. Their frequency of convection is higher and lifetimes are shorter. The polluted clouds also tend to have higher cloud-averaged liquid water contents. It is hypothesized that these responses are a result of a chain reaction set off by stronger evaporation at cloud edges in the case of polluted clouds. In all cases, the smallest clouds either dominate or contribute significantly to cloud fraction and cloud reflectance, in accord with recent satellite studies. The response of cloud fraction and liquid water path to aerosol changes is shown to be strongly dependent on the definition of what constitutes a “cloud,” suggesting that caution be exercised before parameterizing these responses.