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Ozone & Meteorology Monitoring

Photo of a NPS air quality specialist at an air quality monitoring station at Great Smoky Mountains National Park, North Carolina and Tennessee.
Air quality monitoring station at Great Smoky Mountains National Park, North Carolina and Tennessee.

The NPS Air Resources Division operates a network of air quality monitoring stations that measures meteorological parameters and ozone. This is sometimes referred to as the Gaseous Pollutant Monitoring Program (GPMP). Many stations are jointly operated with the Environmental Protection Agency (EPA) through Clean Air Status and Trends Network (CASTNet).

The GPMP historically concentrated on determining the levels of two gaseous air pollutants, ozone and sulfur dioxide, which can be toxic to native plants. Other gaseous pollutants (e.g., other photochemical oxidants, nitrogen compounds, and toxic organic compounds) are also of interest to the NPS because they relate to physiological, morphological, or historical injury to park biological resources, or to global climate change.

  • Locations
  • Data Access
  • Results
  • Objectives & Procedures
  • Resources
  • Contacts

Ozone Monitoring Locations

Most NPS ozone monitoring locations are operated by the NPS in parks identified as mandatory Class I areas. Class 1 areas, defined by the Clean Air Act, are held to a higher air quality standard than other areas. Some ozone monitoring stations in the parks are operated by State agencies.

  • Monitoring History Database – Air quality parameters have been measured in parks since 1987. The database provides details on what has been measured at each location.
Map of NPS air qulaity monitoring locations
Map of NPS air quality monitoring locations. (Click map to enlarge)

Ozone Data

Data Type


Access Data

Metadata what, where, and when monitors have operated in national parks
NPS Gaseous Pollutant & Meteorology ozone and sulfur dioxide (for a limited number of parks) hourly concentrations; wind speed and direction, temperature, relative humidity, precipitation, solar radiation, and wetness at NPS sites
CASTNET data ozone hourly concentrations, meteorology, and filter-pack data at all CASTNet sites
Real-time Scenic and Air Quality Conditions current on-line scenic views, ozone, PM2.5, and/or meteorological data
Current Ozone & Weather Data current 1-hour average ozone concentration, wind speed and direction, temperature, relative humidity, solar radiation, and rainfall for NPS sites (available May–September only)
Health Advisories current health advisories (available May–September) and summaries of past advisory seasons.
Ozone Standard Exceedances park list of ozone standard exceedances by month and year (2000–present)
Current Map of Ozone Data map of current ozone data at NPS sites (available May–September only)
Criteria Pollutants & Meteorology ozone, sulfur dioxide, nitrogen dioxide, carbon monoxide, lead, PM10, PM2.5, and meteorology annual summaries

Ozone Results

NPS Ozone monitoring data summaries, analysis, and results are made available as reports, through Air Atlas, and other publications.

Ozone Trends

Visit the Air Quality Conditions & Trends by Park webpage to learn about ozone trends in parks.

Publications Using NPS Data

Monitoring Objectives & Procedures


  • Provide data to help scientists’ asses the risks that certain pollutants pose to natural resources in the parks.
  • Collect air quality data in parks that reveals how well parks are doing with respect to the national ambient air quality standards set by the EPA. These data are also useful for EPA’s New Source Review permitting program and Prevention of Significant Deterioration program which seek to ensure that new and modified industrial development do not significantly degrade air quality.
  • Identify air quality trends from measured data to aid in compliance predictions, policy objectives, and regional air quality assessments in areas that lack direct monitoring.
  • Assist modeling efforts, regional pollution and transportation studies, State Implementation Plan development (to address regional haze), and national air quality control strategies through special studies.
  • Provide timely NPS air quality information to the public and researchers.


The standard NPS monitoring station measures ozone using a UV-absorption analyzer, a transfer standard, a weather station including wind speed, wind direction, temperature at two heights, solar radiation, relative humidity, and a wetness sensor. Additionally a stacked filter-pack measures sulfate, sulfur dioxide, nitrate, ammonium, and nitric acid, and at some sites a sulfur dioxide. Park staff operate the stations and a contractor maintains and calibrates the network equipment. Data are transmitted nightly, validated, and archived. Hourly data files are transferred to the EPA Air Quality Systems database and are available on the web.

Additional Information

  • Monitoring network overview (pdf, 500 KB) document lists the NPS monitoring objectives, the basics of the monitoring strategy, and information about the operation of the network.
  • How the NPS ozone monitoring fits into US air quality monitoring is explained in a brochure (pdf, 3.5 MB).
  • Related NPS ozone monitoring includes special studies programs using passive samplers, portable O3 monitors, and enhanced multi-pollutant analyzers.
  • The US EPA has set an ozone national standard (NAAQS) of 70 ppb over an 8-hour period for human health and for natural resources. The standard is a calculated value over 3 years using the 4th highest annual ozone of the daily maximum 8-hour averages. See EPA for the full details.
  • AirNow – Map of Today’s Ozone. Daily contour plots of ozone concentrations are available from during the ozone season and include input from National Park Service monitoring stations. These maps are handy for understanding regional distributions and movements of ozone.


National Park Service, Air Resources Division staff – operations, contracts, analysis, and reporting,
Denver, CO

  • Barkley Sive, Monitoring Program Manager (303) 987-6947

Air Resource Specialists – field support and data center contractor, Fort Collins, CO

  • Mike Slate, Field Support Operations Manager (970) 484-7941
  • Jessica Ward, Project Manager, Information Management Center (970) 484-7941

Related Links

Last Updated: March 17, 2016