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### Additional Information

z Introduction to Visibility

z NPS WebCams

z IMPROVE Web Site

z IMPROVE Newsletters

z VIEWS Web Site

z Air Atlas

z ARIS

z Publications

z Studies 

## Visibility Monitoring

Overview

Our national parks and wilderness areas offer stunning m ountain vistas and scenery full of unique landscapes and geologic features. The enjoyment a nd appreciation of these are linked to one's ability to see clearly through the atmosphere. Unfortunately, air pollution affects our ab ility to see clearly. Small particles suspended in the atmosphere, mostly as a result of human -caused air pollution, often create haze -- a grey or white veil over the scene that scrubs it of its colors, forms, and textures an d the lessens the visitor's experience of seeing "forever".

The National Park Service and the U.S. Environmental Pr otection Agency (EPA) first began long-term visibility monitoring at selected national parks in 1979. In 1985, a national visibility monitori ng program was established One of the clearest days at Yosemite National Park, California photograph

One of the haziest days at Yosemite National Park, California photograph 

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...called Interagency Monitoring of Protected Visual Environments, or IMPROVE. IMPROVE is a cooperative effort led by a Steering Committee of representatives from the EPA, U.S. Forest Service, National Park Service, Fish and Wildlife Service, Bureau of Land Manage ment, National Oceanic and Atmospheric Administration, and several interstate air qual ity management organizations.

The goals of the IMPROVE program are to

z measure current visibility and aerosol conditions in mandatory Class I areas

z identify chemical species and emission source s responsible for existi ng human-caused visibility

impairment

z document long-term visibility trends

z and with the enactment of the regional haze regulations , to provide visibility monitoring representative of

all visibility-protected Class I areas.

More information about IM PROVE is available on the IMPROVE web site. The publications, Introduction to Visibility and Air Quality in the National Parks, 2nd edition , also provide good general di scussions of visibility and how it is affe cted by air pollution. Three types of visibility measuremen ts are undertaken in the IMPROVE ne twork: particle, scene, and optical. The mass and chemical composition of the suspended fine particulate matte r (PM-2.5) and the mass of coarse particulate matter (PM-10) is measured by the particle monitor. Every IMPROVE site has such a monitor. The appearance of a scene viewed through the atmosphere changes under different pa rticle concentrations and lighting conditions. The visual appearance of a scene is qualitatively documented with 35mm color slides, digital images, or video images. Optical monitoring measures the ability of the atmosphere to scatter and/or absorb light as it passes through it. Optical monitoring instruments us ed in IMPROVE include transmi ssometers and nephelometers.


### Locations

US Visibility Monitoring Site Map 

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### Procedures

The IMPROVE particle monitor consists of four inde pendent sampling modules. Three modules collect only fine particles (PM2.5), while the four th collects both fine and coarse pa rticles (PM10). The IMPROVE monitor measures mass, chemic al elements, sulfate, nitrate, organics, and elemental carbon. The samplers run for 24 hours every third day collecting the particulate matter on fi lters. These filters are retrieved once a week and sent to contracted laboratories for physical and chemic al analyses. Particle da ta are available on the IMPROVE and VIEWS (Visibility Information Exch ange Web System) web sites.

Scenic conditions are monitored by auto matic camera systems that include cameras that take still photographs three times a day, and web cameras that upload new photos to a web site every 15 minutes. Collections of color images taken at many national parks by th ese camera systems are available on the IMPROVE web site.

Optical measurements (pdf, 338KB) are also made at a handful of parks. These measurements include the attenuation of light over a given distance by transmissome ters and light scattering in a sampled volume of air by nephelometers. Visibility is monitored at 50 units of the Nationa l Park System. Transmissometers, nephelometers, and automatic camera systems are deployed at selected locations. Fo r a larger map with additional information, and a detailed table, please visit our Visibilit y Monitorin g Locations web pa g e.

Particle Sampler at Big Bend N ational Park, Texas photograph

35 mm camera located in Tonto National Monument photograph

Transmissometer at Grand Canyon National Park, Arizona photograph 

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### Data

* The VIEWS website is sponsored by the Regional Pla nning Organizations for the exchange of information relevant to regional haze, and as such, the website includes many differ ent databases on air quality, including IMPROVE data. The website al so utilizes many sophisticated data analysis tools.

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### Results

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### Contact

Skip to Content Skip to navigation DataType Details Access Data
Metadata what, where, and when monitors have operated in national parks Monitoring History Database

Particle elements, sulfate, nitrate, organic carbon, and soil concentrations and extinction estimates IMPROVE website
VIEWS website*
Real-time Scenic and Air Quality Conditions current on-line scenic views, ozone, PM2.5, and/or meteorological data Web Cameras

Scenic Conditions photographic archive IMPROVE website/photos Visibility total light extinction and extinction due to scattering IMPROVE Optical Data

2005-2007 Average Visual Range in Kilometers

Visibility data co llected at national parks and wilderness areas by the NPS and other IMPROVE program participants have helped define spatial and temporal variat ions in visibility throughout the United States. For a larger map a nd additional inform ation, please visit our Visibility Monitoring Results web page. US Average Visual Range Map 2005-2007

N PS Visibility Monitoring Program Manage r Bret Schichtel (970) 491-8581 

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