Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory precursor emissions coagulation resuspension new particle formation subcloud scavenging water uptake primary emissions aqueous chemistry dry deposition activation diffusion condensation evaporation 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 subcloud scavenging water uptake primary emissions aqueous chemistry dry deposition activation diffusion condensation evaporation 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 CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium

Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium Primary Carbon number BC hydrophobic OC

Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium Primary Carbon number BC hydrophobic OC coagulation condensation

Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium Accumulation number sulfate ammonium nitrate secondary OC hydrophobic OC BC Primary Carbon number BC hydrophobic OC coagulation condensation

Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium Accumulation number sulfate ammonium nitrate secondary OC hydrophobic OC BC Primary Carbon number BC hydrophobic OC Fine Soil Dust number soil dust sulfate nitrate secondary OC Fine Sea Salt number sea salt sulfate nitrate secondary OC Coarse Soil Dust number soil dust sulfate nitrate secondary OC Coarse Sea Salt number sea salt sulfate nitrate secondary OC coagulation condensation

Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium Accumulation number sulfate ammonium nitrate secondary OC hydrophobic OC BC Primary Carbon number BC hydrophobic OC Fine Soil Dust number soil dust sulfate nitrate secondary OC Fine Sea Salt number sea salt sulfate nitrate secondary OC Coarse Soil Dust number soil dust sulfate nitrate secondary OC Coarse Sea Salt number sea salt sulfate nitrate secondary OC coagulation condensation All modes log-normal with prescribed width. Total tracers: 25 (33)

Proposed Aerosol Treatment for CAM4 Steve Ghan, Richard Easter, Xiaohong Liu, Rahul Zaveri Pacific Northwest National Laboratory Aitken number sulfate ammonium Accumulation number sulfate ammonium nitrate secondary OC hydrophobic OC BC Primary Carbon number BC hydrophobic OC Fine Soil Dust number soil dust sulfate nitrate secondary OC Fine Sea Salt number sea salt sulfate nitrate secondary OC Coarse Soil Dust number soil dust sulfate nitrate secondary OC Coarse Sea Salt number sea salt sulfate nitrate secondary OC coagulation condensation 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 subcloud scavenging water uptake primary emissions aqueous chemistry dry deposition activation diffusion condensation evaporation 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