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Historical Data Base of Hourly O3 Concentrations for Crestline, California -- 1963 - 2000

A historical database of hourly O3 concentrations for Crestline, California in 1963-2000 has been developed based on all relevant oxidant/ozone monitoring data taken since 1963. All data were obtained from the California Air Resources Board and the U.S. Department of Agriculture Forest Service and have been standardized to be comparable to the current UV photometry calibration basis. A rigorous statistical analysis was performed to integrate these data with differing accuracies, reliabilities and representativeness of the study site into a temporally consistent research-quality data set for Crestline, California. Records of O3 monitoring on a long-term consistent basis provide much needed information to better understand the chronic effects of pollutants on sensitive species. The database provides valuable information on the changing ambient air quality conditions in the San Bernardino Mountains of Southern California due initially to increases in population and vehicle usage and subsequently due to decreases in O3 precursors from the implementation of more effective emission control strategies beginning in the late 1970s.

Crestline (latitude 34:14:29N, longitude 117:16:32W) is situated at an elevation of 1384 m near the top of a south-facing ridge on the Northern Plateau in the San Bernardino Mountains, downwind from major urban areas in the South Coast Air Basin. Crestline was selected as the study site because (1) the highest O3 exposures occur in this area; (2) this is a long-term site for which historical forest survey data on foliar injury on P. ponderosa are available; (3) this site is at high-elevation and represents the southern limit of the western variety of P. ponderosa; (4) loss in growth increment was highest in previous TREGRO model simulation and (5) existing data for photochemical oxidants are available at or in close proximity to the study site since monitoring began in 1963.

The following files are available for downloading and the detailed statistical analysis used to compile the existing oxidant/ozone monitoring data are described in the article.

crestline.xls [Excel 2000 spreadsheet containing hourly O3 concentrations for Crestline in 1963-2000]

crestline.wpd [Wordperfect document - Lee et al. (2003, accepted for publication in Atmospheric Environment)]

To obtain further information, contact E. Henry Lee (Lee.EHenry@epa.gov).

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