GISS Aerosol Microphysics Susanne Bauer GISS Dorothy Koch

GISS Aerosol Microphysics: Susanne Bauer (GISS), Dorothy Koch (GISS) and Robert Mc. Graw (BNL) Motivation: The GISS climate model, only included a mass based aerosol scheme, allowing to calculate the mass of sulfate (Koch et al JGR 99), nitrate (Bauer et al ACP 06), black and organic carbon (Koch et al JGR 01) in one size class, sea salt (Koch et al JGR 06) and dust (Miller et al JGR 06) in a limited set of size classes. Aerosol mixing was only considered between dust, sulfate and nitrate (Bauer et al JGR 06) due to condensation processes. The new microphysical model (Bauer et al ACP 08) includes the processes of secondary particle formation (nucleation), coagulation and condensation, based on the Methods of Moments Scheme. Tracking mass, size and number concentrations and detailed information on the aerosol mixing state. Accumulation modes Mixed acc. modes Nucleation mode coagulation SU NH 4 NO 3 H 2 O nucleation Emission coagulation condensation coagulation SU condensation NO 3 NH 4 coagulation H 2 O condensation BC OC Emission Coars e mode DU SS Emission Species: Sulfate - SU Nitrate - NO 3 Ammonium - NH 4 Water - H 2 O Black carbon - BC Organic carbon- OC Dust - DU Sea Salt - SS DU SS SU Mixed coarse modes NO 3 H 2 O BC OC particle size Improvements for climate simulations: Direct Aerosol Forcing: Explicit treatment of aerosol size, chemical composition (mixing) and water content. Indirect Aerosol Forcing: Explicit calculation of aerosol particle activation, prognostic number concentrations. Interface for the double-moment bulk cloud microphysics scheme.

GISS Aerosol Microphysics: Susanne Bauer (GISS), Dorothy Koch (GISS) and Robert Mc. Graw (BNL) Example of detailed aerosol information as simulated by the GISS model: (Bauer et al, submitted to Atmos. Chem Phys. 2008: The Multiconfiguration Aerosol TRacker of m. IXing state MATRIX, an aerosol microphysical module for global atmospheric models, ) Station Hohenpeissenberg, Germany: Measurement of Number and Size Distribution (black solid line), GISS model number concentration (blue line), mixing mode and chemistry (colored symbols). Aitken mode particles: mix of sulfate and nitrates Accumulation mode particles: Dominant mixing states: OCC - pure organic carbon BOC - organic + black carbon mix BCS - organic, black carbon sulfate mix Information about mixing state Coarse mode: Dominant mixing state: Completely mixed MXX Chemical Species: Dust, sea-salt, and traces of nitrate and sulfate Information about chemical composition