Bullet #4: Precursor emissions generally show marginal to poor agreement, especially for isoprene. In addition, comparison of model and observed CO (a tracer of automotive emissions) also shows poor agreement for the 1995 episode (8-10 rural and suburban sites).
Bullet #5: O3/NOx should be O3/NOy. Although this is encouraging behavior, it should be noted that agreement was much poorer for O3/NOx in urban and suburban locations (VOC limited?). These results neither add nor detract from use of the model to evaluate control strategies (there's no alternative); they do provide a context for interpretation of model results.
Bullet #2: AQA should examine the regional variability of this effect. It may be more evident in some urban areas (e.g., OTR) than others. It should be noted that the change in emissions involves both timing and amount, neither of which has been well quantified.
Bullet #3: Does this suggest that we should stay the course?
Bullet #4: Delete the word "greatest". We can say there is a likely downwind benefit, but we have no quantitative information to compare different control scenarios.
Bullet #5: Delete the word "greatest". This statement is intuitively obvious, but AQA hasn't done any work to examine the potential effectiveness of episodic controls on a regional scale. Model runs do suggest that emissions exert local effects, which would support the statement.
Bullet #2: It should be noted that different scales come from different analyses. The general picture seems to be that transport scale gets shorter as we progress to higher ozone concentrations. Average ozone exihibits coherence over large scales while exceedances are much more localized. Preliminary examination of model roll-out results suggests that scales of influence may differ dramatically from one non-attainment area to the next (Chicago vs OTR vs Atlanta). Although these runs have not been completely analyzed, the variablity in scales seems to be in conflict with transport scales developed by AQA. [It shold be noted that results of model roll-out runs were presented after this outline was posted to the AQA web site.]
Bullet #4: The significance of this observation is not clear. Nor is it that it is in any way related to sources of ozone precursors. Landscape effects and titration with NO can have a major influence on "minimum value" statistics. For example, the density of trees and the complexity of terrain differ between the Midwest and other regions. Surface ozone data collected in small clearings and low-lying areas may be substantially influenced by local deposition. This type of information should be factored into anaylyses of ozone patterns in the OTAG domain.
Bullet #8: This should be re-written. It appears to be contrasting the spatial coverage on non-attainment areas under 1-hour and 8-hour standards. As noted earlier, it is important to look at all data (rural and urban) when trying to evaluate the proposed 8-hour standard. Proximity of sites to cities and landscape features will influence the apparent pattern
of non-attainment under either standard.
Bullet #2: Spatial Coverage may be adequate for ozone, but only if and effort is made to integrate data from all available sources. Coverage is also variable from year to year, with better representation of rural areas in the more recent years.
Bullet #3: It is not clear what is meant. Information on non-episodes is not necessarily a strength. If it is assumed that regulators are going to base decisions on conditions that give rise to episodes, then information on non-episodes may be totally irrelevant.
Bullet #5: AQ analysis can provide "baseline characterization" of the ozone problem, but I'm not really sure we have. Most work has looked at climatological behavior, not necessarily the problematic behavior of ozone. SAI has produced a couple of reports for the Southeast Modeling Center on the representativeness of the OTAG ozone episodes. I suggest that the workgroup take a look at these reports and incorporate them, as appropriate, into the web site and report.
