1. Two-Moment Aerosol Microphysics (TOMAS) Development GEOS-CHEM User’s Meeting 4-6 April 2005 Funding: NSF / NASA Peter Adams Kaiping Chen Jeffrey Pierce Win Trivitayanurak

2. Source: IPCC Third Assessment Report

3. Cloud Condensation Nuclei (CCN) Diameter Number  “Activation” = formation of cloud droplet  involves a competition between solute and surface tension effects Depends on  ambient supersaturation  aerosol composition  aerosol mixing state  number concentration above “critical diameter”

4. Model Development Strategy MODULE DEVELOPMENT GISS GCM II-prime Sulfate: Adams and Seinfeld, 2002 Sea-salt: Jeff Pierce, nearly submitted EC/OC: Kaiping Chen, nearly submitted Dust: Kaiping Chen, developed, in evaluation

5. Model Development Strategy MODULE DEVELOPMENT GISS GCM II-prime Sulfate: Adams and Seinfeld, 2002 Sea-salt: Jeff Pierce, nearly submitted EC/OC: Kaiping Chen, nearly submitted Dust: Kaiping Chen, developed, in evaluation MODULE EVALUATION GEOS-CHEM Sulfate: Win Trivitayanurak, in progress Other species: future

6. Model Development Strategy MODULE DEVELOPMENT GISS GCM II-prime Sulfate: Adams and Seinfeld, 2002 Sea-salt: Jeff Pierce, nearly submitted EC/OC: Kaiping Chen, nearly submitted Dust: Kaiping Chen, developed, in evaluation MODULE EVALUATION GEOS-CHEM Sulfate: Win Trivitayanurak, in progress Other species: future GEOS-CHEM standard code

7.  Two moments of the size distribution (mass and number) are tracked for each size bin.  The average size of particles in a given section is not constant with time  Two-moment method conserves both mass and number precisely  Prevents numerical diffusion present in single- moment methods  Excellent size resolution: 30 sections from.01  m to 10  m TwO-Moment Aerosol Sectional (TOMAS) Model m o 2m o … Mass M1N1M1N1 M2N2M2N2...

8. Aerosol Microphysics Coagulation: General Dynamic Equation Condensation:  ~30,000 grid cells  >= 1 year  Adaptive time steps

9. Impact of Ultrafine Sea- Salt Emissions (% Increase) Clarke parameterization Monahan parameterization Goals: Evaluate emissions parameterizations Evaluate impact of ultrafine sea-salt

10. Impact of Carbonaceous Aerosol on CCN (0.2%) SO 4 / Sea-salt / EC / OC simulation: 330 cm -3 SO 4 / Sea-salt simulation: 180 cm -3 100500200020 Goal: Understand sensitivities of CCN to EC/OC mixing state OC solubility / activation behavior size distribution of primary emissions