5.2 Protocol for Level II Long Range Transport Analysis

The IWAQM is recommending that the MESOPUFF-II model be

run for source-receptor distances of greater than 50 km, up to

several hundred km, when predicting the concentrations for

criteria pollutants. For impacts on AQRVs, the IWAQM is

recommending the use of MESOPUFF-II for all source-receptor

distances. It is also recommended that the analyst generally

follow the recommendations in A Modeling Protocol for Applying

MESOPUFF-II to Long Range Transport Problems (EPA, 1988); the

primary exceptions to that protocol are the distance at which

time dependent dispersion curves are used, the use of the

chemical transformation and deposition algorithms (both wet and

dry), and the use of five years of meteorological data. The

IWAQM recommendations for model options and input parameters

can be found in Appendix A.

The two areas where the previous protocol and the IWAQM

protocol diverge are in the specification of the distance where

time dependent dispersion curves are used to calculate puff

dispersion and the use of the chemical transformation and

deposition options. The previously suggested protocol for the

use of MESOPUFF-II (EPA, 1992) stated that the distance at

which the time dependent dispersion curves should be use was

beyond 100 km. It was indicated that the reason for this

choice was that the 100 km distance was used during the

performance evaluations (EPA, 1986), which identified MESOPUFFII

as one of the better performing models. The reference to

100 km appears to have been erroneous. A summary article,

describing the performance evaluations (Carhart et al., 1989)


The Turner curves were established from experiments

carried out over distances of 0-1 km from the source,

and yet some models use the curves out to 100 km. In

the MESOPUFF-II model, the transition from the Turner

to the Heffter formulation is made at 10 km from the



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