Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory

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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
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Goal Develop a complete and computationally
efficient representation of the aerosol for
exploring the competing and complementing
mechanisms by which natural and anthropogenic
aerosols influence clouds and the cycles of water
and energy.
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Current Weaknesses in CAM

• Aerosol species are externally mixed (individual
  particles are composed of only a single species).

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Current Weaknesses in CAM

• Aerosol species are externally mixed (individual
  particles are composed of only a single species).
• Their size distribution is prescribed (number is
  diagnosed from the predicted mass).
• Processes that should only affect mass also
  affect number.
• Processes that only affect number are neglected.

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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
coagulation condensation
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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
Accumulation number sulfate ammonium nitrate secon
dary OC hydrophobic OC BC
coagulation condensation
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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
Accumulation number sulfate ammonium nitrate
secondary OC hydrophobic OC BC
coagulation condensation
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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
Accumulation number sulfate ammonium nitrate
secondary OC hydrophobic OC BC
coagulation condensation
All modes log-normal with prescribed width. Total
tracers 25 (33)
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Proposed Aerosol Treatment for CAM4Steve Ghan,
Richard Easter, Xiaohong Liu, Rahul
ZaveriPacific Northwest National Laboratory
Accumulation number sulfate ammonium nitrate
secondary OC hydrophobic OC BC
coagulation condensation
All modes log-normal with prescribed width. Total
tracers 25 (33) Cloud-borne aerosol predicted
but not advected.
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Aerosol Processes
new particle formation
evaporation
aqueous chemistry
scavenging
diffusion
coagulation
activation
water uptake
resuspension
subcloud scavenging
oxidation
primary emissions
dry deposition
precursor emissions
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Process Treatment

• New particle formation binary homogeneous
• VOC oxidation and condensation separated
• Condensation mass transfer theory
• Coagulation Brownian within, between modes
• Renaming from Aitken to accumulation
• Scavenging activation of number and mass for
  each mode, number depletion by droplet
  collision/coalescence
• Water uptake Kohler theory for internal mixture,
  with hysteresis dependent on previous aerosol
  water
• Optical properties parameterization in terms of
  wet refractive index and wet surface mode radius

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Schedule

• March 2006 Select version of CAM to start with
• March 2007 Complete application and first
  simulation
• September 2007 Complete evaluation and
  refinement
• December 2007 Complete merge with developmental
  trunk