Three Year Average of the 4th Highest Daily Maximum Ozone Concentrations (2018-2020) from CASTNET 2021-03-05T07:20:10.084-05:00 2021-03-05T07:20:17.283-05:00 Clean Air Status and Trends Network (CASTNET) measures hourly ozone concentrations at rural sites in the United States. This map shows the ambient concentrations from 2018-2020 shown as the 3-year average of the 4th highest daily maximum 8-hour average. Data meet the requirements in 40 CFR Parts 50, 53 &amp; 58. Map was created with site (point) concentrations and inverse distance weighting to create the spatial interpolation. <div>CASTNET is operated by the US EPA in partnership with the National Park Service and Bureau of Land Management Wyoming State Office in collaboration with many other federal, state, tribal and local partners. </div> Puchalski, M. (2021). Clean Air Status and Trends Network (CASTNET) Hourly Ozone Concentrations [Data set]. U.S. Environmental Protection Agency. https://doi.org/10.23719/1520792 CASTNETozoneambient monitoringdesign values 2018-2020 Clean Air Status and Trends Network (CASTNET) 4th highest daily maximum 3-year average (2018-2020) layer North American Profile of ISO19115 2003 2021-03-03 12544000 2021-03-05 07:32:01.02 TRUE 1.0 NAP editor:esri.dijit.metadata.editor 2021-03-05 1614946712652r5644166478889057 Melissa Puchalski US EPA puchalski.melissa@epa.gov https://www.epa.gov/castnet