If any of the statistical measures are worse than the above

ranges, or the graphical procedures are interpreted to yield

unacceptable performance, users should consider choosing an

alternative highly ranked meteorological episode for the

attainment demonstration. Performance evaluations should be

conducted on a prospective alternative episode to determine

whether it yields improved model performance.

Additional model performance measures are encouraged. These

should be described in the Modeling Protocol.



This chapter provides guidance on using modeling simulations

for attainment demonstrations. The primary reason for conducting

photochemical modeling is to demonstrate the effectiveness of

alternative control strategies in attaining the NAAQS for ozone

throughout the modeling domain. This demonstration consists of

four main parts: (1) developing attainment-year modeling emission

inventories, (2) developing alternative-control strategy emission

inventories, (3) performing model simulations for the attainment

year with and without alternative control strategies, and

(4) comparing attainment year and control strategy simulation

results with the ozone NAAQS. Attainment year and control strategy

simulations are conducted for each selected meteorological episode

(see Section 3.1).

6.1 Developing Attainment-Year Model Inputs

The attainment-year modeling inventory must be derived from

the 1990 SIP nonattainment base year inventory, adjusted for

episode-specific meteorology, and then projected to the attainment

year. Also, to the extent possible, initial- and boundarycondition

ozone and precursor concentrations must be projected to

the attainment year. The attainment year is determined by the

nonattainment area designation and the attainment dates specified

in the 1990 CAAA. Projections of emission inventories reflect the

net effect of mandated controls and growth projections for various

source categories. Guidance for projecting inventories is

available in Procedures for Preparing Emissions Projections.14 The

most direct method for projecting initial- and boundary-condition

precursor concentrations is by applying ROM simulation results for

which the UAM domain is nested within the ROM domain (see

Chapter 3). In the absence of available ROM data, the projection

of ozone precursor concentrations used for initial conditions

typically has been done by linear scaling based on emission changes



n1151 - n1152 - n1153 - n1154 - n1155 - n1156 - n1157 - n1158 - n1159 - n1160 - n1161 - n1162 - n1163 - n1164 - n1165 - n1166 - n1167 - n1168 - n1169 - n1170 - n1171 - n1172 - n1173 - n1174 - n1175 - n1176 - n1177 - n1178 - n1179 - n1180 - n1181 - n1182 - n1183 - n1184 - n1185 - n1186 - n1187 - n1188 - n1189 - n1190 - n1191 - n1192 - n1193 - n1194 - n1195 - n1196 - n1197 - n1198 - n1199 - n1200


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