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Generic Guidance and Optimum Model Settings for the CALPUFF ...

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Table A-4 Explanation <strong>and</strong> Recommendations <strong>for</strong> <strong>the</strong> List of Key <strong>CALPUFF</strong> <strong>Model</strong> Options/Continued<br />

Option Parameter Recommended<br />

value<br />

Explanation <strong>and</strong> Justification<br />

Dry deposition modeled MDRY 1 Dry deposition is often important long range transport. May be used in near-field in<br />

certain circumstances. Depends on <strong>the</strong> pollutant characteristics.<br />

Gravitational settling (plume tilt)<br />

Default is <strong>for</strong> plume tilt switch to be turned off. Usually unimportant <strong>for</strong> small<br />

MTILT<br />

0 (combustion size particles less than 10 um). May be needed <strong>for</strong> very large particles<br />

with substantial gravitational settling effects.<br />

Use of turbulence based dispersion coefficients is recommended <strong>for</strong> <strong>the</strong> same reasons<br />

ISCST PG-based dispersion has been replaced by turbulence-based AERMOD<br />

Dispersion coefficients<br />

MDISP<br />

2 dispersion in US plume regulatory modeling. The US EPA default is still to use PG<br />

dispersion in <strong>CALPUFF</strong>, but best science practice <strong>and</strong> model evaluation studies<br />

indicate MDISP=2 per<strong>for</strong>ms better.<br />

σv / σθ <strong>and</strong> σw measurements from<br />

PROFILE.DAT to compute σy <strong>and</strong><br />

σz<br />

Backup method used to compute<br />

dispersion when measured<br />

turbulence data are missing<br />

Method used <strong>for</strong> Lagrangian time<br />

scale <strong>for</strong> σy<br />

Method used to compute turbulence<br />

σv <strong>and</strong> σw profiles<br />

PG σy , σz adjusted <strong>for</strong> roughness<br />

Partial plume penetration into<br />

elevated inversions<br />

MTURBVW<br />

3<br />

MDISP=1, which is to compute dispersion coefficients from measured σv <strong>and</strong> σw is<br />

preferred when good quality, representative turbulence observations are available.<br />

Only used if MDISP = 1 or 5 which means that when measured sigmas are available.<br />

The default is to use observed measured σv / σθ <strong>and</strong> σw from <strong>the</strong> PROFILE.DAT file<br />

to compute σy <strong>and</strong> σz.<br />

MDISP2<br />

3 Used only if MDISP=1 or 5. Backup method is PG dispersion coefficients <strong>for</strong><br />

RURAL areas when turbulence data is missing.<br />

Default Lagrangian time scale (Draxler) is 617.284s. No need to modify. Only used<br />

MTAULY 0 when MDISP = 1,2<br />

Use st<strong>and</strong>ard <strong>CALPUFF</strong> subroutines. MCTURB=2 will use turbulence profiles based<br />

MCTURB 1 on AERMOD algorithms. <strong>Model</strong> evaluations have shown both options have similar<br />

per<strong>for</strong>mance.<br />

Not needed <strong>for</strong> <strong>CALPUFF</strong>. If trying to simulate an AUSPLUME run using single<br />

MROUGH 0 station PLMMET.DAT file <strong>the</strong>n user has choice to adjust <strong>for</strong> zo as is done in<br />

AUSPLUME.<br />

MPARTL 1 Recommend setting is to evaluate partial plume penetration into elevated inversions<br />

applied to point sources.<br />

62

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