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Air Quality-Climate Interactions. Aijun Xiu Carolina Environmental Program. The Interactions of Climate and Air Quality. Direct effect of aerosols on climate Aerosols enhance reflection of solar radiation by the earth-atmosphere system directly by scattering light in clear air (cooling)

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air quality climate interactions

Air Quality-Climate Interactions

Aijun Xiu

Carolina Environmental Program

the interactions of climate and air quality
The Interactions of Climate and Air Quality
  • Direct effect of aerosols on climate
    • Aerosols enhance reflection of solar radiation by the earth-atmosphere system directly by scattering light in clear air (cooling)
    • Black carbon aerosols also absorb radiation (heating)
  • Indirect effect of aerosols
    • Aerosols enhance the solar radiation reflection indirectly by increasing clouds droplets and lifetime (cooling)
  • The effects of aerosols on climate change are the biggest uncertainties in the estimation of anthropogenic climate forcing for current and future time
the integrated meteorology chemistry model
The integrated meteorology/chemistry model

Radiative Feedback of Aerosols


Advection, Chemical Transform

Turbulence and Diffusion, Dry

Deposition, Wet Deposition, Clouds;

Aqueous Chemistry



Met. Couple


Emissions Processing


radiation scheme
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
refractive index
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.
case study with the integrated model
Case Study with the integrated model
  • 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)

(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.

ncar s community climate system model ccsm
NCAR’s Community Climate System Model (CCSM)
  • A comprehensive modeling system with many ctitical components
    • Atmospheric general circulation model (CCM3)
    • Ocean model
    • Land surface biophysics model
    • Sea-ice model
applications of ccsm
Applications of CCSM
  • As climate inputs for PEcon model
  • As IC/BC for MM5 and the integrated model
    • We have developed a program ccm2pregrid so we can use the CCSM outputs to drive MM5 and the integrated model