Aircraft observations of the microphysical and optical properties of major aerosol species

We summarise the microphysical and optical parameters of some principal aerosol species obtained by instrumentation on the UK Met Office C-130 aircraft during international field campaigns since 1996. The aerosol species include Saharan dust, biomass burning aerosol, European continental pollution, eastern seaboard USA pollution, and clean maritime aerosol. The typical structure of the aerosol in the vertical from each airmass type is described. Microphysical parameters are described that comprise the mode radius and geometric standard deviation associated with 2-3 lognormal fits to the mean observed aerosol size distributions spanning the accumulation and coarse modes. Optical parameters comprising the aerosol single scattering albedo (which was both measured and derived from Mie theory), specific extinction coefficient, and asymmetry factor (which were derived from Mie theory) are also presented. Where available, evolution of the physical and optical properties of the aerosol has been highlighted. Comparisons with long-term ground-based AERONET aerosol retrievals show reasonable agreement. Our observations provide useful data for validating and improving global circulation models (GCMs) that use physically based aerosol representation and for validating satellite retrievals of the physical and optical properties of aerosols.