This study presents ISORROPIA II, a thermo-dynamic equilibrium model for the K + –Ca 2+ –Mg 2+ –NH + 4 – Na + –SO 2− 4 –NO − 3 –Cl − –H 2 O aerosol system. A comprehen-sive evaluation of its performance is conducted against water uptake measurements for laboratory aerosol and predictions of the SCAPE2 thermodynamic module over a wide range of atmospherically relevant conditions. The two models agree well, to within 13% for aerosol water content and total PM mass, 16% for aerosol nitrate and 6% for aerosol chloride and ammonium. Largest discrepancies were found under condi-tions of low RH, primarily from differences in the treatment of water uptake and solid state composition. In terms of com-putational speed, ISORROPIA II was more than an order of magnitude faster than SCAPE2, with robust and rapid con-vergence under all conditions. The addition of crustal species does not slow down the thermodynamic calculations (com-pared to the older ISORROPIA code) because of optimiza-tions in the activity coefficient calculation algorithm. Based on its computational rigor and performance, ISORROPIA II appears to be a highly attractive alternative for use in large scale air quality and atmospheric transport models.
CITATION STYLE
Fountoukis, C., & Nenes, A. (2007). ISORROPIA II: a computationally efficient thermodynamic equilibrium model for K+–Ca2+–Mg2+–NH4+–Na+–SO42−–NO3−–Cl−–H2O aerosols. Atmospheric Chemistry and Physics Discussions, 7(1), 1893–1939. Retrieved from http://www.atmos-chem-phys.net/7/4639/2007/
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