AirWare User Manual
AERMOD: A Dispersion Model
This documentation is extracted from Perry et al. (1998).
for Industrial Source Applications
ISC2 accounts for elevated terrain by assuming that the
reflecting surface, which extends from the source to the receptor, is
located at the height of the receptor.
This assumption ignores the fact that under many atmospheric conditions a
plume is displaced vertically as it senses rising terrain.
As a result, ISC2 has been shown to significantly overestimate concentration
as terrain exceeds stack top. This result caused EPA to restrict the
application of ISC2 to terrain at or below stack top. For terrain above
stack top, EPA guidance allows for the use of either:
coupled with the application of the
"intermediate terrain policy
- a conservative screening model (eg., COMPLEX I or RTDM)