Atmospheric aerosol is a suspension of liquid and solid particles, with radii varying from a few run to larger than 100μm, in air. The particles can be directly emitted into the atmosphere (e.g., sea spray aerosol, dust, biomass or fossil fuel burning aerosol, volcanic ash, primary organic aerosol) or produced from precursor gases (e.g., sulfates, nitrates, ammonium salts, secondary organic aerosol). The total aerosol mass is dominated by aerosols produced from the surface due to natural processes such as the action of the wind (sea spray aerosol, desert dust). However, anthropogenic emissions of both primary particles and precursor gases contribute significantly to the total aerosol load [Andreae and Rosenfeld, 2008].