agreement. For modeling exercises over large domains and entire ozone seasons or years, it is

recommended that the operational evaluation be broken down into individual segments such as

geographic subregions and/or months/seasons to allow for a more comprehensive assessment of

the meteorological strengths and weaknesses. Other useful ways of examining model

performance include: aloft, surface, individual episodes (e.g., high ozone / PM2.5 days), diurnal

cycle, as a function of synoptic regimes, or combinations of the above. It is recommended that

the ambient data used in these statistical comparisons be quality checked by doing standard

range check and buddy analyses. To the extent that modelers can set aside a portion of the

ambient data strictly for evaluation purposes (i.e., data not used in the FDDA), that is also

encouraged. Figure 16.1 shows a sample operational evaluation summary. This graphic was

developed using the Atmospheric Model Evaluation Tool (AMET) (Gilliam, 2005), though other

evaluation tools are available.

It may be helpful when calculating domainwide and/or regional summary statistics to

compare the results against previously generated meteorological model performance

"benchmarks" (Emery et al., 2001). However, because of concerns about potentially misleading

comparisons of model performance findings across different analyses with differing model

configurations and FDDA strengths, EPA does not recommend using these benchmarks in a

"pass/fail" mode, but only as a means of assessing general confidence in the meteorological

model data. Statistical results that are outside the range of the compiled benchmarks may

indicate an issue that should be given further examination. Figure 16.2 shows a sample analysis

in this vein.



n801 - n802 - n803 - n804 - n805 - n806 - n807 - n808 - n809 - n810 - n811 - n812 - n813 - n814 - n815 - n816 - n817 - n818 - n819 - n820 - n821 - n822 - n823 - n824 - n825 - n826 - n827 - n828 - n829 - n830 - n831 - n832 - n833 - n834 - n835 - n836 - n837 - n838 - n839 - n840 - n841 - n842 - n843 - n844 - n845 - n846 - n847 - n848 - n849 - n850


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