California Air Resources Board California Map
Statewide Ozone Summary Graphs  

Ozone data for California are summarized in the four graphs that follow.  The data for these graphs have been collected at numerous monitoring sites throughout the State over a number of years.  The Statewide Ozone Data Summary contains data in a tabular form.

The first graph is a plot of the Expected Peak Day Concentration (EPDC).   The EPDC is a statistic used as part of the process for designating areas of the State as attainment or nonattainment with respect to the State standard for ozone.  It represents the ozone concentration expected to occur once per year.  The EPDC is calculated using data over 3 successive years and is plotted on the graph by the last year of the three year period.

Statewide Maximum Ozone Concentrations (1980-1995)


The second graph is a plot of the maximum ozone concentrations measured in California over the last 16 years.

Statewide Maximum Ozone Concentrations (1980-1995)


The next graph is a plot of the number of days each year during which at least one monitoring site in California measured ozone concentrations above the corresponding standards.

Ozone Exceedances (1980-1995)

Three health based ozone air quality standards are presented on the graph above. The State 1-hour standard is a standard established for an outdoor ambient ozone concentration exceeding 0.09 parts per million (ppm).  If the level exceeds 0.09 ppm for a period of one hour during any given day, an exceedance occurs.  The 1-hour Federal ozone standard is triggered by an ozone concentration exceeding 0.12 ppm for a period of one hour during any given day.  The third standard is a recently proposed Federal ozone standard based on a concentration of 0.08 ppm averaged over an 8 hour period.


The fourth graph below is the average number of days per month when at least one monitoring site in California measured ozone concentrations above any one of the three ozone air quality standards shown.  Data for each month for the years 1993, 1994 and 1995 were averaged together.  The three ozone air quality standards described above are plotted for comparison.

Seasonal Ozone Variations (1993-1995)

 
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This page last revised on April 5, 1997
 
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