Ozone Measurements from a Network of Remote Sites

Abstract

The EPA, in cooperation with the U.S. Forest Service, has established a network of air monitoring stations designed to measure levels of ozone in remote areas within the contiguous 48 states. There are currently 8 sites, at various National Forests, which measure ozone, wind speed and direction, temperature, relative humidity, and solar radiation. This is a review of the network data collected during 1979, the year for which the most complete meteorological and ozone records were available. The mean ozone level for 1979 at these sites fell within the range of 0.025- 0.04 ppM. At most sites, there were several days in 1979 when hourly concentrations of ozone exceeded 0.08 ppM. The maximum 1 h ozone concentration observed was 0.125 ppM. The report provides analyses of the statistical distributions of the ozone data from these remote sites, their relationships with local meteorological data, and the possible impact of air parcel history upon ozone concentration. Examination of several individual days in 1979 with relatively high ozone levels using a back trajectory model showed that in almost all of these cases, the air had passed over large urban areas within the previous 3 days. The hypothesis is presented that high levels ofmore » ozone at remote sites may be due in part to the long range transport of ozone and/or its precursors. 1 figure, 4 tables.« less