Using CMAQ-AIM to Evaluate the Gas-Particle Partitioning Treatment in CMAQ Chris Nolte Atmospheric Modeling Division National Exposure Research Laboratory October 19, 2004
Acknowledgements Prakash Bhave Robin Dennis K. Max Zhang Tony Wexler Lucille Bender Charles Chang
Outline Characteristics of the CMAQ and CMAQ-AIM aerosol modules Approach Results Conclusions & Future Work
Comparison between CMAQ and CMAQ-AIM FeatureCMAQCMAQ-AIM Size representation Modal (3 lognormal modes) Sectional (currently 9 sections) Mass transfer to fine PM Instantaneous equilibrium Dynamic Mass transfer to coarse PM NoneDynamic ThermodynamicsISORROPIAAIM
Comparison between CMAQ and CMAQ-AIM (continued) FeatureCMAQCMAQ-AIM Equilibrium StateMetastableStable Sea saltNoYes N 2 O 5 → HNO 3 heterogeneous conversion No CoagulationYesNo
Approach Model to model comparison Continental US domain, 32 km grid cell size, 24 vertical layers, SAPRC 99 chemical mechanism Summer (Jun 24 – Jul 31, 2001) and winter (Dec 24 – Jan 31, 2002) modeling periods
Results: O3 Average ozone concentrations are identical in the two models.
Results: O3 Average ozone concentrations are identical in the two models.
Excellent agreement in average SO 4 concentrations Results: SO4
Excellent agreement in average SO 4 concentrations Results: SO4
O 3 and SO 4 Difference Plots (CMAQ-AIM minus CMAQ)
Results: Total NO 3
TNO 3 Difference Plots (CMAQ-AIM minus CMAQ)
Results: Fine NO 3
Fine NO 3 Difference Plots (CMAQ-AIM minus CMAQ)
Results: HNO 3
HNO 3 Difference Plots (CMAQ-AIM minus CMAQ)
Results: NH 4
NH 4 Difference Plots (CMAQ-AIM minus CMAQ)
Conclusions Initial comparisons of CMAQ and CMAQ-AIM show good agreement. Differences in nitrate partitioning may be due to: (1) Equilibrium assumption vs. dynamic mass transfer (2) Different thermodynamics - activity coefficients (3) Coarse mode sink for NO 3 Future work will involve trying to evaluate these differences independently (1) Run CMAQ-AIM without sea-salt emissions (2) Run CMAQ-AIM with ISORROPIA The research presented here was performed under the Memorandum of Understanding between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Commerce’s National Oceanic and Atmospheric Administration (NOAA) and under agreement number DW Although it has been reviewed by EPA and NOAA and approved for publication, it does not necessarily reflect their policies or views.