WRF-Chem Simulation of Air Quality in China: Sensitivity Analyses of PM Concentrations to Emissions, Atmospheric Transport, and Secondary Organic Aerosol Formation

Abstract:

We investigate air quality in China in April 2007, using the Weather Research and Forecasting model coupled with Chemistry version 3.5 (WRF-Chem) at a spatial resolution of 20km × 20km with 31 vertical levels. The model domain covers the entire East Asian region with 399 × 299 grid cells. The initial and lateral chemical boundary conditions are taken from a present-day simulation of the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) global chemistry-climate model AM3. The Regional Acid Deposition version 2 (RADM2) atmospheric chemical mechanism is used for gas-phase chemistry and the Model Aerosol Dynamics for Europe with the Secondary Organic Aerosol Model (MADE/SORGAM) and aqueous chemistry is used for aerosol chemistry. The emissions of gaseous pollutants (CO, NO_x, NH₃, VOCs, and SO₂) and particulate matter (BC, OC, PM_2.5, and PM₁₀) are taken from the Regional Emission Inventory in Asia (REAS) version 2. Dust and sea salt emissions are simulated online, where dust parameters are optimized using observed particular matter (PM₁₀) concentrations in 73 cities in China. We add gravitational settlement for dust and sea salt in vertical levels. The preliminary results show that the model predicts PM₁₀ reasonably well compared to the ground measurement data. The bias in modeled PM₁₀ concentrations in South and Northwest­­­­­­­ China is less than 10%. We will present results of sensitivity analyses that assess the impact of emissions, atmospheric transport, and secondary organic aerosol formation on PM concentrations.