The Aerosol Models in MODTRAN: Incorporating Selected Measurements from Northern Australia

The aerosol models in MODTRAN are discussed. The focus in this report is on the boundary layer aerosol. The second part of the report outlines the major results of aircraft measurements of atmospheric aerosol obtained around Jabiru, N.T., in June and September 2003. These measurements are used to obtain theoretical multimode size distribution functions. The chemistry composition measurements are used with selected results from the literature to derive spectral refractive indices for the biomass burning smoke aerosol. These results are then used in Mie scattering calculations of the aerosol extinction and scattering coefficients. The attenuation coefficients are then incorporated into MODTRAN and compared with the default aerosol models. Finally the Jabiru aerosol is used in calculations of atmospheric transmission over a series of paths: horizontal, vertical and slant paths. The major result is that the aerosol concentration is quite low giving rise to large visibilities and hence the effect of the atmospheric aerosol on the transmission of radiation over visible and thermal wavebands is small for paths less than around 30 km.