High Time-Resolved Comparisons for In-Depth Probing of CMAQ Fine-Particle and Gas Predictions

In this paper, two major sources of bias in the Community Multi-scale Air Quality Model (CMAQ), one physical and one chemical process, are examined. The examination is conducted with hourly gas and particle data for the inorganic system of sulfate, total ammonia, also called NHX, (gaseous ammonia, NH3 plus aerosol ammonium, NH4) and total nitrate (gaseous nitric acid, HNO3 plus aerosol nitrate, NO3-) and with hourly gas and particle data for inert or conservative species. The physical source of bias stems from the meteorological inputs related to mixing, in particular the behavior of the simulated mixed layer in the evening. The chemical source of bias stems from the nighttime heterogeneous production of HNO3 from N2O5. The analyses are carried out for a summer and a winter period to examine the seasonal dependence of the biases.