Aerosol size distribution and backscatter variability as a function of distance to Caribbean Trade Wind Cumulus Clouds

Shallow maritime cumuli continually modify aerosol size distributions in the trade wind regime, which leads to sampling problems due to this continual aerosol-cloud interaction. Because of the ubiquity of trade wind clouds across the world's tropical oceans, understanding the relationship between trade wind cumuli and aerosol spectra in the trade wind layer is required to evaluate the role of aerosols in Earth's radiation balance and climate. Studies in the past typically select either cloudy or cloud free areas to obtain aerosol size distributions. However, conclusions of past studies point to the fact that distance to cloud is an important parameter to consider when reporting aerosol size distributions. In this work, data collected from the National Center for Atmospheric Research Hercules C-130 during the Rain in Cumulus over the Ocean (RICO) field campaign, which took place during November 2004 - January 2005 in the trades over the western Atlantic, is used to study the variations of deliquesced and dry particle size distributions of sub-micron (dry radius, r = 0.05 - 1.0 &mum) and giant (1 < r ≤ 10 &mum) particles as function of distance to cloud and altitude above the ocean surface. Data collected from 14 research flights using aircraft mounted probes, PCASP/SPP-200 and FSSP/SPP-100, are used to obtain variations in particle spectra as a function of distance to cloud between 600m and 2000m above the ocean surface. Averaged particle size distributions as a function of distance to cloud edge and altitude above the ocean surface were then used to obtain backscatter information and compared to published results. Statistical summaries of the aerosol characteristics, including backscatter calculations, of the trade wind environment in the vicinity of clouds observed during RICO will be presented.