TwoMoment Aerosol Microphysics TOMAS Development GEOSCHEM Users Meeting

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

Source: IPCC Third Assessment Report

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

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

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

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

Tw. O-Moment Aerosol Sectional (TOMAS) Model M 1 M 2. . . § Two moments of the size distribution (mass and number) N 1 N 2. . . are tracked for each size bin. § The average size of particles in a given section is not constant with time mo 2 mo … Mass § Two-moment method conserves both mass and number precisely § Prevents numerical diffusion present in singlemoment methods § Excellent size resolution: 30 sections from. 01 mm to 10 mm

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

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

Impact of Carbonaceous Aerosol on CCN (0. 2%) SO 4 / Sea-salt / EC / OC simulation: 330 cm-3 Goal: Understand sensitivities of CCN to • EC/OC mixing state • OC solubility / activation behavior • size distribution of primary emissions SO 4 / Sea-salt simulation: 180 cm-3 20 100 500 2000