COMPARISON OF TWO AEROSOL MODULES IN MODELS-3/CMAQ: SIMULATION OF PM2.5 FORMATION IN THE LOS ANGELES BASIN

摘要

We have incorporated a new aerosol module into the three-dimensional air quality model Models-3/CMAQ. This aerosol module uses ISORROPIA to simulate the thermodynamics of inorganic chemical species, a parameterization for secondary organic aerosol formation that is based on data from the Caltech smog chamber experiments and a sectional representation of the particle size distribution. The original aerosol module of Models-3 uses a modal representation of the size distribution and less detailed approaches for secondary aerosol formation. We applied Models-3/CMAQ to the 27-28 August 1987 episode of the Southern California Air Quality Study (SCAQS) in the Los Angeles (LA) basin, using (1) the original aerosol module and (2) the aerosol module mentioned above. Both modules reproduce well the evolution of the PM2.5 chemical composition as the air mass moves from the Pacific Ocean to the eastern part of the basin. Discrepancies between the two modules and between the simulations and observations are discussed.