Modeling atmospheric aerosol backscatter at CO2 laser wavelengths. 1: Aerosol properties, modeling techniques, and associated problems.

This paper presents the results of investigations into the problems associated with modeling the atmospheric aerosol backscattering function βCO2 at CO2 laser wavelengths in the lowest 20 km of the atmosphere. It contains a summary of the relevant aerosol characteristics and their variability together with a discussion of the measurement techniques and the errors involved. The different methods of calculating βCO2 both from measured aerosol characteristics and from optical measurements made at other wavelengths are discussed in detail, and limits are placed on the accuracy of these methods. The most significant factor in determining βCO2 has been found to be the aerosol size distribution and concentration, which should be known accurately for particle radii up to at least 1 μm for stratospheric particles and 5 μm for tropospheric particles.