Future Ozone Extremes: Clues from a Data Analysis

To provide clues as to how ozone extremes behave under changes in emissions and climate we analyze the extreme behavior of ozone from the CASTNET ozone dataset over the last 20 years. We analyze the dependence of the shape and location of the ozone distribution on geographic location, emissions and temperature. Depending on these parameters the ozone distribution can be bounded and characterized by a maximum value or it can be unbounded and characterized by a return period. For example, the changes in emissions associated with the EPA SIP call shifts the location of the entire ozone distribution towards lower ozone values and in some locations changes the shape of the distribution from bounded to unbounded. The best methodology to assess ozone extremes is assessed with synthetic ozone distributions.