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PROTOCOL FOR DETERMINING THE BEST PERFORMING AIR QUALITY MODEL

PROTOCOL FOR DETERMINING THE BEST PERFORMING AIR QUALITY MODEL. 8 TH MODELING CONFERENCE SEPTEMBER 22, 23 2005. MODEL PROTOCOL. THESE SLIDES ARE BASED ON AN EPA DOCUMENT – EPA-454/R-92-025 – ENTITLED: “PROTOCOL FOR DETERMINING THE BEST PERFORMING MODEL” DECEMBER 1992

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PROTOCOL FOR DETERMINING THE BEST PERFORMING AIR QUALITY MODEL

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  1. PROTOCOL FOR DETERMINING THE BEST PERFORMING AIR QUALITY MODEL 8TH MODELING CONFERENCE SEPTEMBER 22, 23 2005

  2. MODEL PROTOCOL • THESE SLIDES ARE BASED ON AN EPA DOCUMENT – EPA-454/R-92-025 – ENTITLED: “PROTOCOL FOR DETERMINING THE BEST PERFORMING MODEL” DECEMBER 1992 • REFERENCED IN APPENDIX W

  3. MODEL PROTOCOL • SCREENING TEST IS AVAILABLE • BASED ON FRACTIONAL BIAS (FB) • FB = 2 [PR - OB] / [OB + PR] • BASED ON THE HIGHEST 25 VALUES • IF ABSOLUTE FB EXCEEDS 0.67 (FACTOR OF 2), THE MODEL MAY BE EXCLUDED OB = OBSERVED DATA: PR = PREDICTED DATA

  4. MODEL PROTOCOL • THE MORE ADVANCED STATISTICAL TEST HAS 2 COMPONENTS • A REGULATORY COMPONENT • A SCIENTIFIC COMPONENT

  5. MODEL PROTOCOL • THE REGULATORY COMPONENT • THE PRECISE TIME, LOCATION AND METEOROLOGICAL CONDITIONS ARE NOT OF CONCERN • THE MAGNITUDE OF THE HIGHEST CONCENTRATIONS IS OF PRIMARY CONCERN

  6. MODEL PROTOCOL • THE REGULATORY COMPONENT • USES A TEST STATISTIC – THE ROBUST HIGHEST CONCENTRATION (RHC) - A SMOOTHED ESTIMATE OF THE HIGHEST CONCENTRATIONS • BASED ON A TAIL EXPONENTIAL FIT TO THE UPPER END OF THE DISTRIBUTION • GENERALLY BASED ON THE HIGHEST 25 CONCENTRATIONS • CONDUCTED FOR REGULATORY AVERAGING TIME (E.G. 3- AND 24-HOUR) • USES A PERFORMANCE MEASURE - THE FRACTIONAL BIAS OF THE RHCs

  7. MODEL PROTOCOL • THE SCIENTIFIC COMPONENT • THE LOCATION AND METEOROLOGICAL CONDITIONS ARE OF CONCERN • THE MAGNITUDE OF THE HIGHEST CONCENTRATIONS UNDER EACH CONDITION IS OF CONCERN

  8. MODEL PROTOCOL • THE SCIENTIFIC COMPONENT • USES A TEST STATISTIC – THE ROBUST HIGHEST CONCENTRATION (RHC) - A SMOOTHED ESTIMATE OF THE HIGHEST CONCENTRATIONS • BASED ON A TAIL EXPONENTIAL FIT TO THE UPPER END OF THE DISTRIBUTION • GENERALLY BASED ON THE HIGHEST 25 CONCENTRATIONS • USES A PERFORMANCE - THE FRACTIONAL BIAS OF THE RHCs • CONDUCTED FOR 1 HOUR CONCENTRATIONS • CONDUCTED FOR 2 WIND SPEED GROUPS AND 3 STABILTIY CATEGORIES

  9. MODEL PROTOCOL • COMBINE THE SCIENTIFIC AND REGULATORY COMPONENTS INTO ONE METRIC

  10. MODEL PROTOCOL • USES A COMPOSITE PERFORMANCE METRIC (CPM) CPM = 1/3 [AVERAGE AFBI,J ]+ 2/3 [AFB3 + AFB24 ] / 2 • AFBI,J = absolute fractional bias for met category i at station j • AFB3 = absolute fractional bias for 3 hour averages • AFB24 = absolute fractional bias for 24 hour averages

  11. MODEL PROTOCOL • MODEL TO MODEL COMPARISON USES THE MODEL COMPARISON MEASURE (MCM) MCMA,B = CPMA - CPMB CPMA IS A COMPOSITE PERFORMANCE MEASURE FOR MODEL A CPMB IS A COMPOSITE PERFORMANCE MEASURE FOR MODEL A

  12. MODEL PROTOCOL • THE YARDSTICK • THE RATIO OF THE 1) COMPOSITE DIFFERENCE TO THE 2) STANDARD ERROR • BLOCKED BOOTSTRAP METHOD IS USED TO GENERATE THE ESTIMATE OF THE STANDARD ERROR • RATIOS > 1.7 INDICATE A SIGNIFICANT DIFFERENCE IN THE 2 MODELS AT ABOUT 90% CONFIDENCE LEVEL

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