The question of the best OTAG measures of NA, might be viewed from 3 perspectives: regulatory, effects-relevant and analysis-oriented.
1. Regulatory perspective - What are the current and pending future metrics by which ozone NA is, or will soon be, defined? (possible answer: current NA is based on the highest 1-hour concentration in a day, with a "violation' recorded when 3 or mor days in any 3 year period have max 1-hour concentrations >or= 0.12 ppm (125 ppb). Metrics for pending future standards remain uncertain. However, it appears probable that a new 8-hour primary standard will be promulgated with a threshold in the range of 0.07 to 0.09 ppm, with an annual number of allowable exceedances ranging from 0 to 5. While the level and # of exceedances and treatment of missing data are unknown, the metric (maximum contiguous 8 hours in a calender day) seems to be relatively firm. Also, EPA staff has suggested possible secondary standard of SUM06 or SUM08 aggregated over the maximum 3 contiguous calender months. Also, there may be formal associated measures of severity (# and magnitude of exceedances) and/or alternive "attainment design values" associated with the regulatory metrics. (Would be best to get more specific definitions from the EPA folks (or others) who are closest to CASAC review process).
2. Effects perspective - While existing and pending future NAAQS are derived from, and intended to remediate adverse health and environmental effects, these NAAQS may not themselves be the best or only appropriate metrics to represent effects (W126, for example, or SUM06 aggregated over different hours of day, etc. I suspect various human health and crop or forest health researchers would have some useful opinions, and would be good to accomodate thier preferred metrics to support future effects research/ future revisions to standards, etc.
3. Data Analysis perspective - While it is logical and necessary to conduct data analyses with an eye on the formal metrics of non-attainment, it does not necessarily follow that these are the best or only useful forms of data sorting or aggregation to support informative data analyses. Data volume reduction is also an important goal of data screening or aggregation for analysis purposes. It is useful (for me) to contemplate screening and aggregation from the perspective of the time interval associated with the processed data. Raw ozone data typically has an hourly time step. Another useful way of organizing hourly data (doesn't reduce volume, but ...) might be with a daily time step with each hour-of-day expressed as a seperate variable. In this way, we might look quickly at a time series composed only of 3 PM (or 3 AM) observations. Other daily agg/sorts which may be useful (and reduce volume) would include: daily max, min, 8-hr max, 24 hr mean, 12-hr daytime mean, 12-hr nightime mean. Monthly: max hour, max 8 hr, max 24 hr, max 12 hr daytime mean, max 12 hr nighttime mean, monthly mean, monthly 12 hr daylight mean, monthly 12 hr nighttime mean, SUM06, SUM08, 12 hr daylight SUM06, 12 hr daylight SUM08, W126, etc. Seasonal and annual - many useful statistics are already available for quarterly and annual summaries via AIRS AMP230 files.
