Relationship of Light Scattering and. Absorption, to Visibility Reduction

FIGURE 9.21 Schematic diagram of an integrating nephelometer (from Charlson et at., 1967). 

The Koschmieder equation has been shown to approximate the change in contrast of an object with distance away from an observer (Middleton, 1952) note that it has a form similar to that of the Beer-Lambert law  

C() is the contrast relative to the horizon (or background) of an object seen at the observation point itself, that is, at a distance L 0, and C is the contrast at the distance L. The contrast is defined as the ratio of the brightness of the object (B0) to that of the horizon or background (/ ,) minus one  

For example, a black object at zero distance has a brightness of zero (e.g., it absorbs all the visible light) and hence has a C0 of 1.0. bcxl in Eq. (BB) is the total extinction as defined in Eq. (V). Observers typically can differentiate objects on the horizon if C C() 0.02-0.05. A contrast of 0.02, corresponds, using Eq. (BB), to a visual range VR of 

Visual ranges can vary from hundreds of kilometers in remote areas to only a few kilometers in heavily polluted urban areas. In the latter case, most of the loss in visibility is due to light scattering, with some 

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