Proposed Aerosol Treatment for CAM4

Steve Ghan, Richard Easter, Xiaohong Liu, Rahul ZaveriPacific Northwest National Laboratory

precursor emissions

coagulation

resuspension

new particle formation

subcloudscavenging

wateruptake

primary emissions

aqueouschemistry

drydeposition

activation

diffusion

condensationevaporation

oxidation

scavenging

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.

precursor emissions

coagulation

resuspension

new particle formation

subcloudscavenging

wateruptake

primary emissions

aqueouschemistry

drydeposition

activation

diffusion

condensationevaporation

oxidation

scavenging

Current Weaknesses in CAM

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

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.

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Primary CarbonnumberBChydrophobic OC

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Primary CarbonnumberBChydrophobic OC

coagulationcondensation

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Accumulationnumbersulfateammoniumnitratesecondary OChydrophobic OCBC

Primary CarbonnumberBChydrophobic OC

coagulationcondensation

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Accumulationnumbersulfateammoniumnitrate secondary OChydrophobic OCBC

Primary CarbonnumberBChydrophobic OC

Fine Soil Dustnumbersoil dustsulfatenitrate secondary OC

Fine Sea Saltnumbersea saltsulfatenitrate secondary OC

Coarse Soil Dustnumbersoil dustsulfatenitrate secondary OC

Coarse Sea Saltnumbersea saltsulfatenitrate secondary OC

coagulationcondensation

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Accumulationnumbersulfateammoniumnitrate secondary OChydrophobic OCBC

Primary CarbonnumberBChydrophobic OC

Fine Soil Dustnumbersoil dustsulfatenitrate secondary OC

Fine Sea Saltnumbersea saltsulfatenitrate secondary OC

Coarse Soil Dustnumbersoil dustsulfatenitrate secondary OC

Coarse Sea Saltnumbersea saltsulfatenitrate secondary OC

coagulationcondensation

All modes log-normal with prescribed width.

Total tracers: 25 (33)

Proposed Aerosol Treatment for CAM4Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri

Pacific Northwest National Laboratory

Aitkennumbersulfateammonium

Accumulationnumbersulfateammoniumnitrate secondary OChydrophobic OCBC

Primary CarbonnumberBChydrophobic OC

Fine Soil Dustnumbersoil dustsulfatenitrate secondary OC

Fine Sea Saltnumbersea saltsulfatenitrate secondary OC

Coarse Soil Dustnumbersoil dustsulfatenitrate secondary OC

Coarse Sea Saltnumbersea saltsulfatenitrate secondary OC

coagulationcondensation

All modes log-normal with prescribed width.

Total tracers: 25 (33)

Cloud-borne aerosol predicted but not advected.

Aerosol Processes

precursor emissions

coagulation

resuspension

new particle formation

subcloudscavenging

wateruptake

primary emissions

aqueouschemistry

drydeposition

activation

diffusion

condensationevaporation

oxidation

scavenging

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

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