1. Linking Anthropogenic Aerosols, Urban Air Pollution and Tropospheric Chemistry to Climate ( actually, to CAM/CCSM ) Chien Wang Massachusetts Institute of Technology Current and Future Researches

2. Impacts of Tropospheric Chemistry and Aerosols on Climatic and Environmental Change Radiative forcings of CH 4 and tropospheric O 3 Radiative forcing and influence on hydrological cycle of aerosols Air pollution, acid deposition, and pollutant cleaning Impacts of Climatic Change on Tropospheric Chemistry and Aerosols Temperature, UV fluxes, and H 2 O(g) on reaction rates Cloud and precipitation processing of gases and aerosols Clouds on aerosols’ effective climate impacts Why do we need an interactive model Basic requirement for the interactive model A good balance of the process complexity (including needed important processes and parameters) and model performance (accomplishing runs of 50-100 years with a practical turnaround time)

3. Importance of Aerosols’ Chemical Compositions: JJA DJF -10001000 0 -500500 (mm/yr/grid) BC Caused Changes in Convective Precipitation Rate (Using the last 20-year means of two 60-year runs coupled with SOM; Wang, 2004)

4. Maximum Coverage of Cloud vs. Initial CCN Concentration Total Precipitation vs. Initial CCN Concentration Importance of Aerosols’ Number Concentration: Results from Thirty 3-D cloud-resolving model runs (Wang, 2004a&b)

5. Importance of Aerosols’ Size Distribution: Results of Size-Resolving Aerosol Model (Ekman et al., 2004) Note: Observed. max. value (>7nm) in anvil: 2.5·10 4 Modeled max. value (>6nm) in anvil: 5.5 ·10 4 Altitude (km) 20 10 0 50 250 Horizontal distance (km) 177.5316.2562.51000.0 Aitken mode (6nm<d<30nm) Concentration (100 cm -3 ) 100.0 0.11.010.0100.01000.0 Acc. mode aerosol (d>30nm) 20 10 0 Altitude (km) 50 250 Horizontal distance (km) Concentration (cm -3 )

6. Current Aerosol Dynamic Models 1. Continuous size distribution models: Solving the aerosol general dynamic equation in continuous form. 2. Sectional models: 10+ size sections, fixed or moving; mass only or mass and number; inherent internal mixture structure. 3. Moment models: Using prognostic moments to close the size distribution with or without a prescribed function; chemistry-based multiple mode structure; single-moment = mass only external mixture model. Accuracy in Representation Computational Affordability Current selection

7. (Wilson et al., 2001; Ekman et al., 2004) SO 4 (g) SO 4 nuc SO 4 ait SO 4 acc BC/OC/SO 4 mixed BC pure nucleation condensation emissions dry deposition coagulation nucleation and impact scavenging ‘growth’ The size- and chemical-resolving aerosol modal model Work in progress: ternary nucleation Additions: pure OC mode; nitrate to mixed mode Prescribed: climatological dust and sea salt

8. Sub-grid processes in most current global models Scales of Key Chemical Species in Troposphere 10 2 reactions and  40 prognostic species are normally used to describe the NOx-HOx-VOC-O 3 system Local processes Sec.-Min. VOCs NOx Aerosol Trop O 3 HOx CO < 10 0 10 1 10 2 10 3 10 4 ~10 6 CH 4 10 Yrs Week Day Hour Month Tropospheric Lifetime Corresponding Spatial Scale (km)

9. (Courtesy of Andreas Richter) Inhomogeneous Distribution of Key Precursors: (Do we need to apply complicated chemistry everywhere?)

10. Nonlinearity in Fast Chemistry: O 3 Mole Fraction (ppb) Derived Using CB4 Mechanism

11. Coupling the Urban and Global Chemistry Models: An alternative solution (Mayer et al., 2000) Emission Preprocessor Urban Air Pollution Model Grid Model: Background Chemistry Parameterized Urban Model: Fast Urban Chemistry Rural Emissions Urban Emissions Grid Concentrations of Chemical Species Total Emissions Grid-model Predictions Urban-model Predictions Daily Predictions of the ModelsPreprocessors

12. Modeled tropospheric mean properties of key species from runs including and excluding the Urban Meta Model MIT IGSM 120-Year Runs

13. The Interactive Aerosol-Chemistry-Climate Model A collaborative effort of MIT and NCAR scientists References: Wang (2004); Wang et al. (1998); Mayer et al. (2000) ; Kiehl et al. (1998); Barth et al. (2000); Rasch et al. (2000); and Kiehl et al. (2000) AGCM: NCAR CAM + CLM Atmospheric circulation and state Clouds and precipitation Radiation Atmospheric Chemistry and Aerosol Model: 25 Chemical species 5 or 6 Aerosol modes Advection, convection, and mixing Gaseous and aqueous reactions Wet and dry deposition Urban Air Pollution Model Concentrations of Chemicals & Aerosols Winds, T, H 2 O, Precipitation & Radiative Fluxes OGCM or SST Data A-O Exchanges MIT EPPA Emissions Note: This is an alternative effort to other colleagues’ similar works

14. Selected Issues of Interest for 3D Interactive Modeling Aerosol-cloud interaction and hydrological cycle Urban O 3 production and export on tropospheric chemistry Estimate of future environmental evolution with climate change Acknowledgements NSF, NASA, Ford-MIT Alliance, US EPA, and MIT Joint Program on the Science and Policy of Global Change Model Evaluation Ground: AGAGE, NOAA CMDL, ARONET, etc. Satellite: MODIS, POLDER, GOME, MOPITT, TES, etc. Others: Field experiment data, NCAR aerosol climatology, etc.