1. Global Aerosol Microphysics With TOMAS Peter J. Adams Acknowledgments: Win Trivitayanurak GEOS-CHEM User’s Meeting April 7, 2009 Center for Atmospheric Particle Studies (CAPS)

2. Motivation: CCN and Indirect Effect Diameter Aerosol Number Distribution Indirect effect of aerosols on clouds depends on number concentration of cloud condensation nuclei (CCN) Activation = conversion of a CCN particle to a cloud droplet Kohler theory tells us that a CCN is a particle with enough solute to overcome surface tension CCN = number of particles larger than critical diameter = shaded area Critical diameter depends on: Aerosol composition (solubility) Cloud supersaturation →Need to predict size-resolved aerosol composition

3. TOMAS Algorithm TOMAS (TwO-Moment Aerosol Sectional microphysics algorithm) Microphysics: condensation, coagulation, nucleation Moments = 1) aerosol number and 2) aerosol mass 30 bins segregated by dry mass per particle Size range is about 10 nm – 10 μm DpDp Number Size Distribution N2 N3 N4 N5 N6 N7 N30 N1 … Mass Size Distribution DpDp … SO 4 2- NaCl … M2 M3 M4 M5 M6 M7 M30 M1 0.01 0.1 1 10 (  m)

4. GEOS-CHEM Implementation: Status TOMAS is fully implemented in GEOS-CHEM (v. 7-04-11) Size distribution 30 size sections; 10 nm to 10  m Species Sulfate Sea-salt (NaCl) Organic Carbon (OC): hydrophobic and hydrophillic Elemental Carbon (EC): externally mixed and internally mixed Mineral Dust Note this is 240 TOMAS-related tracers Processes Coagulation Condensational growth (H 2 SO 4 and SOA condensation) Cloud processing (in-cloud oxidation of SO 2 to sulfate) Nucleation: binary (Vehkamaki) and ternary (Napari); ion-induced (MODGIL) easily implemented Size-resolved deposition and primary emissions

5. cm -3 Sample model result dN/dlogDp (cm -3 ) 0.01 0.1 1 10 Diameter (  m) cm -3 dM/dlogDp (  g m -3 ) 0.01 0.1 1 10 Diameter (  m)

6. Regional nucleation events: ACE-Asia Ron Brown ship Gosan site Obs. BNUC TNUC Ternary nucleation… captures regional event too frequent Date 12 13 ~400 km away ~600 km away Gosan Ron Brown Concentration (cm -3 )

7. Timing and Other Options TOMAS is fast enough to run in a 3D model: One month simulation on Intel Xeon (2.66 GHz, 4 GB RAM) TOMAS-30 10 µ m1 µ m 0.1 µ m 0.01 µ m 5 bins 2 bins 5 bins 10 bins 5 bins TOMAS-15 TOMAS-12 Lumping size bins Std. GEOS- CHEM With TOMAS Tracers5412 hours Wall Clock3103 days Other size resolutions developed in GISS GCM:

8. Conclusions Fully functional TOMAS implemented in our version of GEOS-CHEM All major aerosol species Reasonable description of all microphysical processes 14 papers published or in development Ready to discuss implementation as an option in “standard” GEOS-CHEM TOMAS recommended for some problems Nucleation, number of ultrafine particles, CCN Inefficient for other problems where aerosol mass is sufficient Discussion items: Nucleation options SOA options Size bin options