Using the information from above,

(a) (Mean 8-hr daily max.)future = (87.2 + 82.4 + 77.5 + 81.1)/4 = 82.1 ppb

and

(b) (Mean 8-hr daily max.)baseline = (98.3 + 100.2 + 91.6 + 90.7)/4 = 95.2 ppb

(3) The relative response factor for site I is

(RRF)I = (mean 8-hr daily max.)future/(mean 8-hr daily max.)baseline

= 82.1/95.2 = 0.862

PM2.5 NAAQS

For PM2.5 applications, we recommend choosing predicted 24-hour average

concentrations from each modeled day (excluding “ramp-up” days) for consideration in the

modeled attainment test20. The 24-hour average values should be used, because they are the

basis for design value calculations.

The second decision that needs to be made is, “which of the 24-hour average values

predicted in cells near a monitor should we use to calculate the RRF?” For the annual PM2.,5

NAAQS, we recommend taking the spatially averaged value of the nearby predictions (mean

value of the grid cell array). Each component-specific relative response factor (RRF)j used in the

modeled attainment test is computed by taking the ratio of the mean of the spatially averaged

daily predictions in the future to the mean of the spatially averaged daily predictions with current

20This includes modeled days for which there is no corresponding monitored data.

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castellano: DISPER CUSTIC DESCAR RADIA italiano:

castellano: DIS CUS DES RAD english: DIS CUS DES RAD

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