Haze trends over the United States, 1980–1995

The patterns and trends of haze over the United States for the period of 1980–1995 are presented. Haze measurements are based on human visual range observations at 298 synoptic meteorological stations operated by the United States Weather Service. There was a significant ( 10%) decline in haziness over the 15-yr period. The reductions were evident throughout the eastern United States as well as over the hazy air basins of California. During the same period, in the eastern United States sulfur emissions also declined by about 10%. However, a causality for the reductions has not been established. This report is an update of an earlier survey of haze patterns and trends from 1950 to 1980.