UPPER BUFFALO WILDERNESS, ARKANSAS
		Photographic Archive 1988 - 1993

SPECTRUM FREQUENCY SUMMARIES

Visual range (km) and cumulative frequency summaries are provided for each archived spectrum series with associated IMPROVE aerosol data. Aerosol data correlations are not available for sites having no associated aerosol data prior to Fall 1999.

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Tabular summaries for each range of visibility grouping include:

• Spectrum sequence number
• The representative visibility condition for each archived image. Units presented include:
• deciview(dv)- the haziness index designed to be linear with respect to human perception of visibility. A 1-2 dv change in haziness corresponds to a small, visibly perceptible change in scene appearance. Higher deciview values indicate more extinction and a corresponding decrease in visual range, indicating an increase in haziness.
• extinction (b_ext) - the loss of light due to scattering and absorption as it passes through a medium. Presented in units of inverse megameters (Mm^-1), with 10 representing pristine conditions.
• visual range (VR) - the distance at which a large black object just disappears from view. Presented in kilometers, with 391 representing pristine (Rayleigh) conditions.
• The frequency of occurrence of the given image's visibility condition in relation to IMPROVE aerosol data collected at the site.

Word of Caution:

No direct correlation should be made between original visibility monitoring slides (or their measurements) and these provided reproduced images. Each replication and measured slide contrast is different from the original Kodachrome 35mm slide because of changes in film exposure, film type, digital scanning calibrations, and viewing equipment. Slides should be grouped into visibility categories such as excellent, good, medium, and poor. All associated photographs were selected as a set and must remain intact.

It should be noted that there is error, sometimes substantial error, in the process of estimating visual range from Kodachrome slides. True error in each slide measurement is dependent on the characteristics of the scene and target, weather conditions, sun angle, uniformity of the air quality in the sight path, film exposure, measurement error and other factors. The above visual range estimates and corresponding extinction and deciview measurements have been rounded for precision.