Multiple Scenario Processor for
AERMOD/ISC
The Multiple Scenario Processor (MSP) for
AERMOD/ISC eliminates the need to perform multiple modeling iterations while
evaluating multiple emissions scenarios. The MSP provides the same accuracy
as a complete air quality dispersion modeling analysis without the
associated time requirements. BREEZE MSP utilizes the linear
relationship between emission rates and concentrations to predict, with a
single model execution, the concentrations at all receptors for multiple
modeling emissions scenarios. For example, for a simple scenario with 30
sources, a user can evaluate 30 emissions scenarios saving nine hours of
computation time when compared to multiple, single-run analyses. The more
complex the scenario or the greater the number of emissions scenarios, the
more time savings that can achieved with BREEZE MSP.
The BREEZE MSP stores emission rates for
up to 200 pollutants and applies them appropriately when calculating
receptor concentrations. The user has the option of making a model run of
all pollutants stored in the database, a subset of the pollutants, or a
single pollutant.
MSP Output Model
The structure of the AERMOD/ISC MSP output
text file is the same as for single scenario runs. In addition, the MSP
utility is capable of generating the following output files for each
emission scenario modeled:
POSTFILE –
contains concentration results for each source group and averaging period
combination specified by the user for each receptor modeled. They are often
used in post-processing programs and can be formatted as either binary or
ASCII text.
PLOTFILE –
contains the user specified High values for each source group and averaging
period combination for each receptor modeled. This file is often used to
generate contour or surface plots of the 1st through 6th highest
concentration results.
MAXFILE –
contains concentrations that occurred over a user-specified concentration at
each receptor modeled for a single threshold concentration. A planned
upgrade will allow the user to assign a threshold concentration for each
emission scenario modeled.
TOXFILE –
file for use with the EPA post-processing program, Toxic Modeling System
Short-Term (TOXST). The TOXST program estimates expected exceedances of
specified short-term health effects thresholds in the vicinity of continuous
and intermittent toxic releases. Although EPA’s current version of TOXST is
not compatible with ISCST3, Trinity offers a version that is compatible with
the latest version of ISCST3. This output file however, is not compatible
with the ISCMSP unless the model is run in single pollutant mode.
BREEZE MSP versions of AERMOD and ISCST3 also contain additional
post-processing files for use with BREEZE productivity tools, including:
RAWFILE –
a file used by the GIS mapping and contouring features in BREEZE.
This file contains concentrations for user specified High values for each
source group and averaging period combination for each receptor and
pollutant modeled. This information is used with BREEZE Graphics and
Surfer to generate base maps that display receptor concentrations with
respect to facility boundary, sources, and buildings.
PERCENT –
compressed versions of the standard AERMOD/ISC POSTFILEs. BREEZE ISC
and AERMOD MSP has an option to generate these files that are often up to
95% smaller than binary POSTFILEs containing the same information. The
BREEZE productivity tool, PERCENT uses this file to determine the
maximum percentile concentration of a pollutant for a particular averaging
period. The output from PERCENT can be used with BREEZE Graphics to
produce contour plots of percentile concentrations. Any tool that
post-processes POSTFILEs could be modified to use the multi-pollutant
compressed PERCENT files. |
MSP Software
