CHLORINE_CHEMISTRY_NOTES - 15 Sep 2005
This release contains gas-phase chlorine chemistry in the CMAQ Chemical
Transport Model (CCTM). The purpose of these notes is to describe the
chlorine mechanism used in the CCTM.
A chlorine chemical mechanism has been added to the CCTM based on Tanaka
et al. (2003). The original chlorine mechanism proposed by Tanaka et al.
(2003) contains 13 reactions. However, two of those reactions involve 1,3
butadiene and its reaction product. Since the base CB-IV mechanism does
not contain 1,3 butadiene, these two reactions were eleminated and the
remaining 11 reactions were combined with the CB-IV mechanism and
incorporated into the CCTM. An EBI solver has also been developed for the
combined mechanism (chlorine + CB-IV mechanism). The current chlorine
chemistry can not be used in conjuction with the SAPRC-99 mechanism.
In-house tests were conducted using chlorine emissions for two cases
(Sarwar and Gipson, 2005) (1) In one case, the CCTM was run with molecular
chlorine emissions from the 1999 National Emissions Inventory of Hazardous
Air Pollutants (2) in the other case, the molecular chlorine was
supplemented with HOCl emissions estimated from swimming pools and cooling
towers. Initial test results indicate that when molecular chlorine
emissions were included in the model, the only impact occurred near the
Great Salt Lake. Ozone concentration at that location increased by a
maximum of 14 ppbv. When both molecular chlorine and hypochlorous acid
emissions were included in the model, the impacts were evident at several
areas, including the Great Salt Lake and the Houston area.
1) Build script for the CMAQ Model with chlorine chemistry:
Build script distributed with the standard CMAQ model can be used to
extract source codes for the chlorine chemistry and the relevant ebi
solver. However, the script needs the folowing changes in order to
extract the correct files:
Need to use "ebi_cb4cl" to extract ebi solver source code for the
chlorine chemistry:
set ModChem = ( module ebi_cb4cl $Revision; )
Need to use "cb4cl_ae3_aq" to extract source code for the combined
chemistry (CB-IV + Chlorine chemistry):
set Mechanism = cb4cl_ae3_aq
The source code can be complied using the modified build script.
2) Running the CMAQ Model with Chlorine Chemistry:
The run script distributed with the standard CMAQ model can be used to
run the CMAQ model with the chlorine chemistry. However, several
additional steps are necessary for running the CMAQ model with chlorine
chemistry:
The Meteorology Chemistry Interface Processor (MCIP, version 3.0) is
needed to generate deposition velocities for six additional species
used in the chlorine chemistry. Deposition velocities for these and
other species are stored in METCRO2D file generated by the MCIP.
Sparse Matrix Operator Kernel Emissions (SMOKE) System is needed to
generate model-ready chlorine emissions. These emissions need to be
added to the files containing emissions of other species used by the
CMAQ model.
Any IC and BC files for the standard CMAQ model can be used to run the
CMAQ model with chlorine chemistry. These IC and BC files currently do
not contain any values for the additional species in the chlorine
chemistry. Therefore, the minimum default value (10E-30 ppm) will be
used for these additional species in the CMAQ model with chlorine
chemistry.
References:
Sarwar, G., and G. Gipson. The effect of chlorine emissions on tropospheric
Ozone in the United States. A&WMA 98th Annual Conference, Minneapolis,
Minnesota, June 21-24, 2005. Session AB-3c, Development and
Application of Regional Transport One-Atmosphere Models in a
Regulatory Context. Air & Waste Management Association, Pittsburgh,
Paper # 596, 2005.
Tanaka, P. L., D.T. Allen, E.C. McDonald-Buller, S. Chang, Y. Kimura, C.B.
Mullins, G. Yarwood, and J.D. Neece, Development of a chlorine
mechanism for use in the carbon bond IV chemistry model, Journal of
Geophysical Research, 108(D4), 4145, doi:10.1029/2002JD002432, 2003.
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Topic: Chlorine Chemistry Notes (Read 1984 times)
