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In 1995, the IMPROVE (Interagency Monitoring of Protected Visual Environment) Steering Committee formed a consensus, that five 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 slides is selected from the period of record and archived on CD-ROM. This series of slides 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.


          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 slides that show scenic views of the vista and observations of meteorological interest during the period of record.


          Historical slide selections requested by the IMPROVE Committee and/or other air quality managers that depict visibility conditions for the project-specific reports or public presentations.


To access site-specific images; select the gallery archive type from the menu at the left.






The total number of slides selected for each historical archive depends on the vista, the variability in visual air quality, the period of record, and completeness of the slide database. Final sets can vary from 50 to 150 slides. Final images are selected and assigned to gallery archive types (accessed at the left) as follows:


          Spectrum Series slides consist of selected clear sky days that represent a range of visibility conditions from good to bad for selected monitoring time periods. Slides with fog and other weather-related occurrences or evident layered hazes are not included. Impaired visibility is most often apparent by the loss of color, texture or contrast of scenic features. Each series contains slides showing a uniform haze, which degrades visibility evenly across the scene.


Using slide densitometry measurements, known target distances, and estimated inherent contrast measurements; the visual range (km) is estimated for each slide of the series. All values are rounded for precision. Associated extinction (Mm-1) and haziness (dv) values are calculated. Representative cumulative frequency summaries for each image are provided for sites that also have IMPROVE aerosol-monitoring instrumentation.


All spectrum series slides were selected as a set and should remain intact.


          Episode series slides are chosen to represent regional or layered haze conditions that continue for a period of time greater than an isolated event (2 or more days). These can often be attributed to wildfires, long-term periods of air stagnation, plumes, or winter inversions in the region.


          Layered Haze slides depict ground-based or elevated layered haze, or some combination thereof described as multiple haze layers. Layered hazes occur when pollutants are released into a stable atmosphere with little or no vertical mixing. The pollutants form a layer of haze that continues to develop as long as the air mass above remains stagnant. Layers can form near the ground and are known as ground-based layered hazes. Layers that are not in contact with the ground are described as elevated layered hazes. Layered hazes are usually associated with emissions that are local in nature as opposed to pollutants that are transported over hundreds of kilometers.


          Scenic slides represent special scenic qualities such as interesting cloud formations, pristine conditions, snow-covered scenes or meteorological observations.


          Historical Selections include any slide data that has been used to depict visibility conditions in project-specific reports or public presentations. Base slides used for the modeling application WinHaze Visual Air Quality Modeler, and the header image used for HTML-formatted Web pages of this historical archive are also included in historical selections.


Historical slide archives for each site are reproduced digitally to Kodak Photo Cd (PCD) format and transferred to a Kodak Gold CD. 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 IMPROVE Program under contract to the National Park Service (NPS) Air Resources Division.




Prepared by Air Resource Specialists, Inc.

Under NPS Contract CX-1270-96-006



For additional information contact:
Air Resource Specialists, Inc.
1901 Sharp Point Drive
Suite E
Fort Collins, CO 80525
Ph: 970.484.7941
Fx: 970.484.3423