The remaining mass and the nonsulfate hydrogen are believed to be qualita- tively related to the spatial distribution of organic aerosols. Do Cat . Livestock waste management operations are the dominant source. In the adjoining regions to the north and south, median standard visual range is also good, exceed- ing 100 km. Median visual range falls to less than 50 km along the northern Pacific coast, less than 30 km in the central valley of Califor- nia, and less than 15 km in the Los Angeles basin.
Visibility generally improves with altitude.
Ct ILL C' . In the East, airport data and NPS camera data reveal a strong summertime visibility minimum that is strongly linked to a summertime maximum in sulfate concentrations. Airport data from the late 1940s through the early 198Os show coher- ent visibility trends over large regions. In the Northeast, visibility has moderately improved during the winter and moderately decreased during the summer. Visibility in the Southeast has worsened moderately during the winter and substantially during the summer.