Ozone W126 Index
The impact of ozone exposure on trees, plants and ecosystems often is assessed using a seasonal index known as a "W126 index." A W126 index, named after portions of the equation used to calculate it, is a weighted index designed to reflect the cumulative exposures that can damage plants and trees during the consecutive three months in the growing season when daytime ozone concentrations are the highest and plant growth is most likely to be affected.
Here is a list of resources for calculating W126 index values.
- How the W126 index value is calculated (PDF, 67 KB)
- Excel file with Daily Index calculation programmed (XLS, 22 KB)
- Excel file with 3-year average W126 value calculation programmed (XLS, 747 KB)
Here are additional resources related to the 2014 ozone NAAQS proposal (79 FR 75234)
- Analysis relating the W126 metric and the annual 4th highest daily maximum 8-hour concentration metric (Nov 20, 2014 technical memorandum) (PDF, 1.2 MB)
- Table of values for the W126 and 4th high metrics for all U.S. ozone monitoring sites (data used in Nov 20, 2014 technical memorandum) (ZIP, 163 KB)