Visibility Monitoring
Overview
Yosemite National Park, California
Our national parks and wilderness areas offer stunning mountain vistas and scenery full of unique landscapes and geologic features. The enjoyment and appreciation of these are linked to one's ability to see clearly through the atmosphere. Unfortunately, air pollution affects our ability 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 and the lessens the visitor's experience of seeing "forever".
Yosemite National Park, California
The National Park Service and the U.S. Environmental Protection Agency (EPA) first began long-term visibility monitoring at selected national parks in 1979. In 1985, a national visibility monitoring program was established 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 Management, National Oceanic and Atmospheric Administration, and several interstate air quality management organizations.
The goals of the IMPROVE program are to
- measure current visibility and aerosol conditions in mandatory Class I areas
- identify chemical species and emission sources responsible for existing human-caused visibility impairment
- document long-term visibility trends
- and with the enactment of the regional haze regulations, to provide visibility monitoring representative of all visibility-protected Class I areas.
Three types of visibility measurements are undertaken in the IMPROVE network: particle (or aerosol), scene, and optical. The mass and chemical composition of the suspended fine particulate matter (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 particle 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 or absorb light as it passes through it. Optical monitoring instruments used in IMPROVE include transmissometers and nephelometers.
Locations
Procedures
The IMPROVE particle monitor consists of four independent sampling modules. Three modules collect only fine particles (PM2.5), while the fourth collects both fine and coarse particles (PM10). The IMPROVE monitor measures mass, chemical elements, sulfate, nitrate, organics, and elemental carbon. The samplers run for 24 hours every third day collecting the particulate matter on filters. These filters are retrieved once a week and sent to contracted laboratories for physical and chemical analyses. Particle data are available on the IMPROVE and VIEWS web sites.
Scenic conditions are monitored by automatic camera systems that include cameras that take still photographs three times a day, and web cameras (pdf, 207KB) that upload new photos to a web site every 15 minutes. Collections of color images taken at many national parks by these camera systems are available on the IMPROVE and VIEWS web sites.
Optical measurements (pdf, 338KB) are also made at a handful of parks. These measurements include the attenuation of light over a given distance by transmissometers and light scattering in a sampled volume of air by nephelometers.
Data
| 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* |
| Stacked-bar Charts | alphabetical listing by Class I area of the contribution of sulfate, nitrate, organics, elemental carbon and soil to extinction on the 20% best and worst days from 2000-present | Best days A-L (1.2mb pdf) Best days M-Z (1.3mb pdf) Worst days A-L (1.2mb pdf) Worst days M-Z (1.3mb pdf) |
| 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 | John Molenar |
* The VIEWS website is sponsored by the Regional Planning Organizations for the exchange of information relevant to regional haze, and as such, the website includes many different databases on air quality, including IMPROVE data. The website also utilizes many sophisticated data analysis tools.
Results
Contacts
| NPS Visibility Monitoring Program Manager | Bret Schichtel | (970) 491-8581 |