Ozone monitoring and environmental effects analysis

National Forests in North Carolina

SUMMARY: Natural resource managers need to use available ozone data to extrapolate the measured values in order to estimate the seasonal ozone exposure to National Forest lands. Where vegetation has the greatest risk from suffering from biomass (growth) reductions can be predicted using soil moisture data and the combination of two ozone exposure statistics known as the N100 and the W126. The N100 is the number of hours when the measured ozone concentration is greater than or equal to 0.100 parts per million (ppm). Experimental trials with a frequent number of peaks (hourly averages greater than or equal to 0.100 ppm) have been demonstrated to cause greater growth loss to vegetation than trials with no peaks in the exposure regime. The W126, the seasonal ozone exposure, was developed as a biologically meaningful way to summarize hourly average ozone data as it places a greater weight on the measured values as the concentrations increase. The use of both the N100 and W126 is consistent with the recommendations of the Federal Land Manager Air Quality Related Values Workgroup. The objective of this project is to obtain hourly ozone data to be summarized for two seasonal statistics, which will then be spatially extrapolated for the lower 48 United States.

EFETAC'S ROLE: EFETAC provided funding for this project.

STATUS: Completed

PROGRESS: The USDA Forest Service has acquired ozone data for two particular years of interest from all available monitoring sites (with an acceptable percent data capture) in the lower 48 United States. Three distinct types of spatial data have been produced including (1) a summary of the data at each of the ambient monitoring locations; (2) estimates of the W126 and N100, along with the uncertainties, using ordinary kriging; and (3) raster files of the W126, N100, and the 95 percent confidence interval for each of the preceding estimates. Data for 2000 and 2005 have been published and are available on the Air Resource Management webpage.


Air Resource Management Webpage

Bill Jackson, USDA Forest Service Air Resource Specialist, bjackson02@fs.fed.us or (828) 257-4815

Updated May 2010

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