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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)

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

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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)

Motivation: CCN and Indirect Effect

Diameter

Aer

osol

Num

ber

Dis

trib

utio

n• 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

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

Dp

Number Size Distribution

N2 N3 N4 N5N6

N7

N30N1

Mass Size Distribution

Dp…

SO42-

NaCl

M2M3

M4M5

M6 M7

M30

M1

0.01 0.1 1 10 0.01 0.1 1 10 (m) (m)

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 (H2SO4 and SOA condensation)• Cloud processing (in-cloud oxidation of SO2 to sulfate)• Nucleation: binary (Vehkamaki) and ternary (Napari); ion-induced

(MODGIL) easily implemented• Size-resolved deposition and primary emissions

cm-3

Sample model result

0

1000

2000

3000

4000

5000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

dN/d

logD

p (c

m-3)

0.01 0.1 1 10Diameter (m)

cm-3

dM/d

logD

p (

g m

-3)

0

50

100

150

200

250

300

1 3 5 7 9 11 13 15 17 19 21 23 25 27 290.01 0.1 1 10

Diameter (m)

0

50

100

150

200

250

300

1 12 23

Dust

OM2

OM1

Mixed EC

Pure EC

SeaSalt

SO4

Regional nucleation events: ACE-Asia

Ron Brown ship

Gosan site

Obs.BNUCTNUC

Ternary nucleation…• captures regional event• too frequent

Date

Date

1213

~400 km away

~600 km away

Gosan

Ron Brown

Co

nce

ntr

atio

n (

cm-3)

Co

nce

ntr

atio

n (

cm-3)

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 µm1 µm0.1 µm0.01 µm

5 bins 5 bins 2 bins

5 bins

10 bins 10 bins 10 bins

5 bins 5 binsTOMAS-15

TOMAS-12

Lumping size bins

Std. GEOS-CHEM

With TOMAS

Tracers 54 12 hours

Wall Clock 310 3 days

• Other size resolutions developed in GISS GCM:

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