Intercomparison of visibility measurement methods

A research program underway in the eastern U.S. is described, which intercompares standard visibility measurement techniques with visibility-related parameters determined by optical instruments. Utilizing a telephotometer, a camera, and integrating nephelometers (INs), the program also seeks to relate visibility to the chemical and physical properties of the atmospheric aerosol. Preliminary findings suggest that the telephotometer and camera will both approximate the visibility perception of the eye, but that the proper selection of targets and target distances is an important prerequisite. Furthermore, modification of the aerosol sample seems to be a major limitation of the IN in a humid environment.