Chapter 16
Comparing the ISORROPIA
and EQSAM Aerosol Thermodynamic
Options in CAMx
Bonyoung Koo, Swen Metzger, Pradeepa Vennam, Chris Emery,
Gary Wilson and Greg Yarwood
Abstract The Comprehensive Air quality Model with extensions (CAMx) has
been employing ISORROPIA for inorganic aerosol thermodynamic calculations.
Recently, the Equilibrium Simplified Aerosol Model (EQSAM) was added to CAMx
as an alternative to ISORROPIA for computing concentrations of the inorganic ions:
sulfate, nitrate, ammonium, sodium and chloride. By design, EQSAM has more
streamlined algorithms than ISORROPIA, which may lead to different model concentrations and faster run times. We apply CAMx using both thermodynamic equilibrium modules for simulations of the continental US with 12 km grid resolution for
winter and summer months. Model predictions of inorganic ions by both algorithms
are compared and model performance is evaluated against ambient data collected
by speciated PM monitoring networks. The overall model run times are also compared. Our purpose is to introduce EQSAM as a newly available option in CAMx
and provide information relevant to choosing between the two available aerosol thermodynamics modules in CAMx taking into consideration the scheme’s performance
attributes as well as the requirements of each model application.
B. Koo · P. Vennam · C. Emery · G. Wilson · G. Yarwood (B)
Bay Area Air Quality Management District, 375 Beale Street, Suite 600, San Francisco, CA
94105, USA
e-mail: gyarwood@ramboll.com
B. Koo
e-mail: bkoo@ramboll.com
P. Vennam
e-mail: pvennam@ramboll.com
C. Emery
e-mail: cemery@ramboll.com
G. Wilson
e-mail: gwilson@ramboll.com
S. Metzger
ResearchConcepts io GmbH, Freiburg im Breisgau, Germany
e-mail: swen.metzger@eco-serve.de
© Springer Nature Switzerland AG 2020
C. Mensink et al. (eds.), Air Pollution Modeling and its Application XXVI,
Springer Proceedings in Complexity,
https://doi.org/10.1007/978-3-030-22055-6_16
93
Comparing the ISORROPIA
and EQSAM Aerosol Thermodynamic
Options in CAMx
Bonyoung Koo, Swen Metzger, Pradeepa Vennam, Chris Emery,
Gary Wilson and Greg Yarwood
Abstract The Comprehensive Air quality Model with extensions (CAMx) has
been employing ISORROPIA for inorganic aerosol thermodynamic calculations.
Recently, the Equilibrium Simplified Aerosol Model (EQSAM) was added to CAMx
as an alternative to ISORROPIA for computing concentrations of the inorganic ions:
sulfate, nitrate, ammonium, sodium and chloride. By design, EQSAM has more
streamlined algorithms than ISORROPIA, which may lead to different model concentrations and faster run times. We apply CAMx using both thermodynamic equilibrium modules for simulations of the continental US with 12 km grid resolution for
winter and summer months. Model predictions of inorganic ions by both algorithms
are compared and model performance is evaluated against ambient data collected
by speciated PM monitoring networks. The overall model run times are also compared. Our purpose is to introduce EQSAM as a newly available option in CAMx
and provide information relevant to choosing between the two available aerosol thermodynamics modules in CAMx taking into consideration the scheme’s performance
attributes as well as the requirements of each model application.
B. Koo · P. Vennam · C. Emery · G. Wilson · G. Yarwood (B)
Bay Area Air Quality Management District, 375 Beale Street, Suite 600, San Francisco, CA
94105, USA
e-mail: gyarwood@ramboll.com
B. Koo
e-mail: bkoo@ramboll.com
P. Vennam
e-mail: pvennam@ramboll.com
C. Emery
e-mail: cemery@ramboll.com
G. Wilson
e-mail: gwilson@ramboll.com
S. Metzger
ResearchConcepts io GmbH, Freiburg im Breisgau, Germany
e-mail: swen.metzger@eco-serve.de
© Springer Nature Switzerland AG 2020
C. Mensink et al. (eds.), Air Pollution Modeling and its Application XXVI,
Springer Proceedings in Complexity,
https://doi.org/10.1007/978-3-030-22055-6_16
93