Linking Anthropogenic Aerosols, Urban Air Pollution and Tropospheric Chemistry to Climate actually,

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Linking Anthropogenic Aerosols, Urban Air
Pollution and Tropospheric Chemistry to Climate
(actually, to CAM/CCSM)
Current and Future Researches

• Chien Wang

Massachusetts Institute of Technology
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Impacts of Tropospheric Chemistry and Aerosols on
Climatic and Environmental Change
Why do we need an interactive model

• Radiative forcings of CH4 and tropospheric O3
• 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 H2O(g) on reaction
  rates
• Cloud and precipitation processing of gases and
  aerosols
• Clouds on aerosols effective climate impacts

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)
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Importance of Aerosols Chemical Compositions
BC Caused Changes in Convective Precipitation
Rate (Using the last 20-year means of two 60-year
runs coupled with SOM Wang, 2004)
(mm/yr/grid)
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Maximum Coverage of Cloud vs. Initial CCN
Concentration
Importance of Aerosols Number Concentration Resu
lts from Thirty 3-D cloud-resolving model runs
(Wang, 2004ab)
Total Precipitation vs. Initial CCN
Concentration
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Importance of Aerosols Size Distribution
Results of Size-Resolving Aerosol Model (Ekman
et al., 2004) Note Observed. max. value (gt7nm)
in anvil 2.5104 Modeled max. value (gt6nm) in
anvil 5.5 104
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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.
Computational Affordability
Accuracy in Representation
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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
(Wilson et al., 2001 Ekman et al., 2004)
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Scales of Key Chemical Species in Troposphere
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Inhomogeneous Distribution of Key Precursors (Do
we need to apply complicated chemistry
everywhere?)
(Courtesy of Andreas Richter)
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Nonlinearity in Fast Chemistry O3 Mole Fraction
(ppb) Derived Using CB4 Mechanism
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Coupling the Urban and Global Chemistry
Models An alternative solution (Mayer et al.,
2000)
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Modeled tropospheric mean properties of key
species from runs including and excluding the
Urban Meta Model
MIT IGSM 120-Year Runs
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The Interactive Aerosol-Chemistry-Climate Model A
collaborative effort of MIT and NCAR scientists
Note This is an alternative effort to other
colleagues similar works
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)
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Selected Issues of Interest for 3D Interactive
Modeling
Model Evaluation

• Ground AGAGE, NOAA CMDL, ARONET, etc.
• Satellite MODIS, POLDER, GOME, MOPITT, TES, etc.
  
• Others Field experiment data, NCAR aerosol
  climatology, etc.

• Aerosol-cloud interaction and hydrological cycle
• Urban O3 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