Figure 2. Visibility monitoring sites for which long-term data exist.
Figure 3. Daily variation of Bext for Houston, TX and New Orleans, LA. Note the change in the visibility threshold over time.
Figure 4. Superposition of 25th, 50th, 75th, and 90th percentile Bext for Bismarck, ND. When all these values are the same, it is an indication that Bext is constant.
Figure 5. Trend of Bext percentiles for Sioux City, IA
Figure 6. Daily pattern of Bext for Raleigh/Durham, NC for 1961 and 1992. In a and b all data are shown regardless of the weather conditions. In c and d the days with fog and precipitation are eliminated.
Figure 7. Secular haze trends (1960-1992) for 6 eastern U.S. regions.
Figure 8. Seasonal haze pattern for Raleigh, NC, Greensboro, NC, and Charlotte, NC.
Figure 9. Seasonal haze pattern for Houston, TX, Port Arthur, TX, and Lake Charles, LA.
Figure 10. Seasonal haze pattern for Toledo, OH, Flint, MI, and Detroit, MI.
Figure 11. Seasonal haze pattern for Los Angeles, CA and Long Beach, CA.