ABSTRACT
The atmosphere affects optical extensive air shower observation primarily by attenuating and scattering the produced Cherenkov or fluorescence light. Attenuation is due to both purely absorptive processes and scattering processes which disperse light out of the direction of the line of sight. The troposphere is characterized by turbulent behavior which generates the well-known phenomenon of weather. It is also characterized by convective cooling processes, with the heat source being the surface of the Earth. The temperature of the troposphere drops with altitude above the Earth's surface due to the convective cooling, at a rate of -6.5 degrees per kilometer. Aerosol, or Mie, scattering is quite complex. It has a rapid dependence on scattering angle which varies with aerosol size, aerosol shape, and dielectric constant. The aerosol size distribution may change as a function of altitude, composition of pollutants, and weather conditions.
