US Forest Service Historical Overview

forest scene

In 1995, the IMPROVE (Interagency Monitoring of Protected Visual Environments) Steering Committee, including the US Forest Service, formed a consensus that five (5) years of scene monitoring yields sufficient examples of most visual air quality conditions. To secure a representative set of observed air quality conditions for each scene monitoring site, a series of images is selected from the period of record and archived on CD-ROM. This series of images makes up the historical photographic archive and consists of:

A spectrum series of regional haze visibility conditions observed at the site for each monitored time of day.
A selection of the cleanest clear sky images representing seasonal pristine conditions for each monitoring season.
Selected visibility and meteorological episodes or events observed during the period of record (including wildfire, winter inversions, and/or regional haze impacts).
Selected layered haze events observed during the period of record.
Specific images that show scenic views of the vista and observations of meteorological interest during the period of record.
Historical image selections requested by the US Forest Service and/or other air quality managers that depict visibility conditions for project-specific reports or public presentations.

The total number of images selected for each historical archive depends on the vista, the variability in visual air quality, the period of record and completeness of the image database. Final sets can vary from 50 to 150 images. Master historical photographic archives produced for each site contain 4 JPEG resolutions of each selected image (Image Gallery); graphic images of the monitoring location and site vistas (Site Specifications), as well as associated cumulative frequency summaries, tables and/or data listings (Spectrum Frequencies).


Air Resource Specialists, Inc. created this historical photographic archive for the Forest Service Air Monitoring Program. The US Forest Service is the copyright owner of all provided images. Any commercial use or duplication of this material without prior approval or licensing is forbidden. Use of the provided images should reference the Forest Service Air Monitoring Program.