A study of visibility in eighteen cities in the western and southwestern United States.

Abstract

A threshold visibility below which visibility is deemed 'poor' is determined for each station. The number of poor days divided by the total number of days with unlimited ceiling is calculated for each year. No general trends are apparent over the total period. Visibilities generally decreased, however, from 1958 to 1972 and generally increased from 1973 to 1978.-from Authors