A Modeling Investigation of the Climate Effects of Air Pollutants

1. A Modeling Investigation of the Climate Effects of Air Pollutants Aijun Xiu1, Rohit Mathur2, Adel Hanna1, Uma Shankar1, Frank Binkowski1, Carlie Coats3 1. University of North Carolina at Chapel Hill 2. ASMD, ARL/NOAA, NERL/US EPA 3. Baron Advanced Meteorological Systems

2. Presentation Topics • Air quality modeling components • What is non-integrated meteorology/chemistry modeling? • The integrated meteorology/chemistry model • Optical properties of aerosols and radiative feedback • Case study simulation for July 1995 episode • Analysis (model vs. observations) and evaluation • Summary and on going research

3. Offline Air Quality Modeling CTM (MAQSIP, CMAQ) Advection, Chemical Transform Turbulence and Diffusion, Dry Deposition, Wet Deposition, Clouds; Aqueous Chemistry Meteorology MM5 Met. Couple MCPL, MCIP Emissions Processing SMOKE

4. Typical Air Quality Modeling Approach • Meteorological data are prepared offline and used as input to the chemistry transport model • Meteorological model outputs are processed to comply with the chemistry-transport format • Meteorological data output are less frequent than internal model time step • Temporal interpolation may lead to misleading results; may not capture the evolution of the PBL or may cause erroneous wind direction • Physical inconsistencies may occur (e.g., mass conservation if re-diagnosis of wind is required) • Radiative feedbacks of atmospheric constituents such as aerosols are not accounted for

5. Objectives • Develop and apply an air quality modeling system with integrated meteorology, emissions, and chemistry • Examine the feedback due to the direct effect of aerosols • Provide a platform for air pollution/climate feedback studies, e.g., examination of the indirect effects of aerosols

6. Integrated Meteorology-Chemistry Model Radiative Feedback of Aerosols CTM (MAQSIP) Advection, Chemical Transform Turbulence and Diffusion, Dry Deposition, Wet Deposition, Clouds; Aqueous Chemistry Meteorology MM5 Met. Couple MCPL Emissions Processing SMOKE

7. Multiscale Air Quality Simulation Platform (MAQSIP) • Modular/generalized coordinate • Prototype for Models3/CMAQ • Gas-phase and heterogeneous chemistry • Modified CBM-IV; modified QSSA, modal PM approach • Processes/modules • Advection Bott’s scheme • Turbulent mixing; K-theory • Clouds/aqueous chemistry; Kuo and Kain and Fritsch • Dry deposition • Wet deposition

8. Radiation Scheme • CCM2 radiation scheme in MM5 • Delta-Eddington approximation to calculate solar absorption with the solar spectrum divided into 18 discrete intervals • Absorption of O3, CO2, O2, and H2O • Scattering and absorption of cloud water droplet • Direct radiative forcing of aerosols is included using Mie approximation to calculate scattering and extinction efficiencies using aerosol effective radius and refractive index

9. Refractive Index • Refractive index is the particle optical property relative to the atmosphere and is used in the Mie scattering calculation to provide optical properties • A complex number, the real part represents the scattering and the imaginary part the absorbing properties • In the integrated model, the refractive index is calculated with the scattering and absorbing effects of a variety of aerosols (NH4, SO4, NO3, H2O, organic aerosol, elemental carbon, and dust). Sea salt will be included later.

10. Case Studies36 km simulation • Eastern US case study; 36 km horizontal grid resolution; 21 layers • July 2-15, 1995 period • SMOKE; anthropogenic and biogenic • MAQSIP is called every MM5 time step (100 Seconds) • Three days model spin-up

11. Air Quality Monitoring CASTNetIMPROVE

12. PM2.5

13. SO4

14. NH4

15. NO3

16. Aerosol Compositions

17. Aerosol optical depth comparisons

18. Analysis of the Radiative Feedback Short Wave Radiation Boundary Layer Average (No Feedback – Feedback) PM Fine Mass

19. Radiation Feedback Short Wave Radiation Boundary Layer Average (No Feedback – Feedback) PM particle size

20. Radiation Feedback Short Wave Radiation Boundary Layer Average (No Feedback – Feedback) Number Density

21. Reduction in Shortwave Radiation Concentration Size Number Density

22. Summary • Presented results from an episodic (10 days) integrated meteorology/chemistry regional scale model • Comparisons with observations suggest the ability of the model to capture spatial gradients in concentrations • The model simulations show the direct effect of aerosols causing reduction in surface short-wave energy which contributes to lower planetary boundary layer (PBL) heights • The aerosol size distribution parameters (number and mean diameter) seem to be as important as mass concentration in the direct radiative forcing

23. Ongoing/Future Work • Studying the effects of 1995 Canadian wildfires • Application to the Indian subcontinent (NSF) • Radiative effects of carbonaceous aerosol • Comparisons with INDOEX measurements • Study effects of aircraft emissions (NASA) • Comparisons with SONEX

24. R825388

25. Case Studies 108 km simulation • 1995 summer Canadian fire • Canada and US domain; 108 km horizontal resolution; 21 vertical layers • One month simulations (June 15 – July 15) • SMOKE for anthropogenic and biogenic emissions • MAQSIP is called every MM5 time step (300 Seconds) • Simulations with and without estimated wildfire emissions • Speciated wildfire emissions scaled to CO emission estimates from McKeen et al. (2002)

26. (a) CO (b) O3 (c) Carbonaceous particulate matter Simulated increases in surface level concentration (difference between simulations with and without fire emissions) resulting from the transport and chemical evolution of emissions from large Canadian forest fires at 1900 GMT on July 2, 1995.