Abstract

Preliminary results are available from a study of the modeling of β_10.6, the aerosol backscattering coefficient at 10.6 μm, using published data on aerosol characteristics in the free troposphere and lower stratosphere. The main problem with such modeling is concerned with our knowledge of the characteristics of the larger aerosol particles (radii > 1 μm) whose presence, even in very small numbers, greatly changes the volume scattering cross-section. Factors which have been considered in this modeling, some of which are discussed quantitatively below, are the following:

1. Aerosol size distribution

2. Aerosol refractive index

3. Aerosol shape

4. Measurement uncertainties

5. Natural variations with time, height, location and meteorological conditions

Calculations have been made of β_10.6 using published data on the above factors and the modified AGAUSX scattering code developed by the U.S. Army Atmospheric Sciences Laboratory and the Department of Physics, New Mexico State University.