In this section, we identify several means of analysis for addressing the issues identified

in section 1.2. States should perform the set of analyses that is most appropriate based on

available data bases for the area under review.

(1) What do air quality trends (normalized for meteorological differences) at midcourse

review suggest about the likelihood of meeting the NAAQS on time?

(2) What does aerometric analysis of the role of transport vs. local emissions suggest

about the likelihood of meeting the NAAQS?

(3) Are aerometric data observed at mid-course review time consistent with modeled

projections used earlier to conclude that the most recent SIP revision is sufficient to

meet the NAAQS on time?

2.1 Use Air Quality Trends To Assess Whether A SIP Is On Track Toward Attainment

These analyses require decisions to be made about four factors to make well informed

judgments about whether timely attainment is likely: (1) choosing one or more trend

parameters, (2) adjusting (i.e., normalizing) observed ozone trends in the selected trend

4

parameters for meteorological differences, (3) deciding whether ozone trends are likely to be

most responsive to changes in VOC or NOx emissions or changes in both, and (4) selecting

the area for which trends in emissions will be estimated.

Choosing trend parameters. There are several things to consider when choosing trend

parameters in a mid-course review. Closeness of the parameter to the definition (i.e., form) of

the NAAQS, susceptibility to extreme or unusual meteorological conditions, stability of the

parameter, dependence on the number of sites with measured values. Table 2.1 presents

some potential trend parameters along with comments about the suitability of each. Table 2.1

is not comprehensive. Other trend parameters may be used, so long as a rationale for doing

so is presented. Since trend parameters could behave differently from one another, it is

advisable to select several parameters to get a better overall sense of how air quality is

changing.

 

 

n1201 - n1202 - n1203 - n1204 - n1205 - n1206 - n1207 - n1208 - n1209 - n1210 - n1211 - n1212 - n1213 - n1214 - n1215 - n1216 - n1217 - n1218 - n1219 - n1220 - n1221 - n1222 - n1223 - n1224 - n1225 - n1226 - n1227 - n1228 - n1229 - n1230 - n1231 - n1232 - n1233 - n1234 - n1235 - n1236 - n1237 - n1238 - n1239 - n1240 - n1241 - n1242 - n1243 - n1244 - n1245 - n1246 - n12247 - n1248 - n1249 - n1250

 

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