JPG File 3.72M

Figure 6.6
Visibility measurements show that the entire eastern third of the United States is under the influence of a widespread aerosol on April 26, 1990. Visibility is usually dominated by scattering of light and is estimated from visual range at numerous airports, shown here as daytime averages. Larger circles represent lower visibility (visibility is represented by the extinction coefficient, σ, which is proportional to the inverse visual range, in units of km-1). (from the National Climatic Data Center, 1998b.)