5.2 Assessing Model Performance Results

Both graphical and statistical performance measures should be

used for the performance evaluation. However, although the

recommended statistical measures should be applied for all

meteorological episodes and monitoring networks, caution is

suggested for interpreting these measures in cases of sparse

monitoring network coverage. The Technical Committee should

consider the monitoring network design in interpreting statistical


In assessing model simulation results for the performance

evaluation, there is no rigid criterion for model acceptance or

rejection (i.e., no pass/fail test). Reference 17 states that,

based on past photochemical model evaluations, this type of

modeling "generally produces peak (unpaired) prediction accuracy,

overall bias, and gross error statistics in the approximate ranges

of ±15-20 percent, ±5-15 percent, and 30-35 percent, respectively."

In general, performance results that fall within these ranges would

be acceptable. However, caution is urged in using these ranges as

the sole basis for determining the acceptability of model performance.

These ranges were derived from past model performance

evaluations with varying densities of air quality and meteorological

monitoring networks and corresponding variations in the quality

and quantity of aerometric model input data. In some cases, they

reflect use of earlier versions of the UAM. Thus, these ranges

should be used in conjunction with the graphical procedures to

assess overall model performance.


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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