There is a new paper that further improves our understanding the role of aerosols on clouds and precipitation. The paper is
S. Solomos, G. Kallos, J. Kushta, M. Astitha, C. Tremback, A. Nenes, and Z. Levin: 2011 – An integrated modeling study on the effects of mineral dust and sea salt particles on clouds and precipitation. Atmos. Chem. Phys., 11, 873–892, 2011.
The abstract reads [highlight added]
“This report addresses the effects of pollution on the development of precipitation in clean (“pristine”) and polluted (“hazy”) environments in the Eastern Mediterranean by using the Integrated Community Limited Area Modeling System (ICLAMS) (an extended version of the Regional Atmospheric Modeling System, RAMS). The use of this model allows one to investigate the interactions of the aerosols with cloud development. The simulations show that the onset of precipitation in hazy clouds is delayed compared to pristine conditions. Adding small concentrations of GCCN to polluted clouds promotes early-stage rain. The addition of GCCN to pristine clouds has no effect on precipitation amounts. Topography was found to be more important for the distribution of precipitation than aerosol properties. Increasing by 15% the concentration of hygroscopic dust particles for a case study over the Eastern Mediterranean resulted in more vigorous convection and more intense updrafts. The clouds that were formed extended about three kilometers higher, delaying the initiation of precipitation by one hour. Prognostic treatment of the aerosol concentrations in the explicit cloud droplet nucleation scheme of the model, improved the model performance for the twenty-four hour accumulated precipitation. The spatial distribution and the amounts of precipitation were found to vary greatly between the different aerosol scenarios. These results indicate the large uncertainty that remains and the need for more accurate description of aerosol feedbacks in atmospheric models and climate change predictions.”
The conclusion includes the text
“These results illustrate the highly non-linear response of precipitation to aerosol properties and indicate that a large portion of uncertainty remains unresolved. This study focuses mostly on investigating the mechanisms that are associated with the aerosol cloud interactions for a specific event. Therefore it is not possible to extract generic results. Nevertheless, this work represents one of the first limited area modelling studies for aerosol-cloud-radiation effects at the area of Eastern Mediterranean and could be used as a basis for future improvements and longer term studies. More intense combined modeling and observational surveys on the interactions between airborne particles and cloud processes at regional and local scale are necessary in order to improve our knowledge on the interactions between atmospheric chemistry and meteorology.”