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Implementation of Sulfate and Sea-Salt
Aerosol Microphysics in GEOS-Chem
Win Trivitayanurak & Peter AdamsCarnegie Mellon University
3rd GEOS-Chem Users’ MeetingApril 11, 2007
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 2
Radiative Forcing EstimatesGlobal-average estimates for 2005, relative to 1750
Level of scientific understanding
+2.6 W/m2
-1.2 W/m2
IPCC (2007)
+1.6 W/m2
Must improve aerosol indirect effect estimate!
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 3
Improving Aerosol Microphysics
GISS GCM-II’• Produce its own
meteorology• Cannot predict at a
specific time
GEOSCHEM• Driven by assimilated
meteorology• Good for predicting at
specific times for comparison with observations
MicrophysicsMicrophysics
Climate change & Forcing estimate purpose
Aerosol model evaluation purpose
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 4
Size-resolved Microphysics
• TOMAS (TwO-Moment Aerosol Sectional microphysics algorithm)[Adams and Seinfeld, 2002]
– Moments = 1) aerosol number and 2) aerosol mass– 30 bins segregated by dry mass per particle– Size range is about 10 nm – 10 μm
N1 N2 N3
N4 N5N6 N7
N30SO4
2-
NaCl
…
Size Distribution
Dp
…SO42-
NaCl
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 5
TOMAS processes
–Coagulation–Condensation/ evaporation–Nucleation– In-cloud sulfur oxidation–Size-resolved dry deposition–Size-resolved wet deposition
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 6
TOMAS Status
• Species: Number, SO42-, Sea-salt
• Advection– Problem: TPCORE/ PPM parabolic
interpolation artificially grows/shrinks particles – Fixed (see me for detail)
• Convection– Negative entrainment at some time steps
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 7
TOMAS Status
• Emission– Sulfate: Same total, apply size distribution– Sea-salt: Clarke et al (2006) parameterization– Number: calculated from emitted mass and
assumed size distribution
• Nucleation : Binary nucleation (H2SO4-H2O)
• Aqueous oxidation of sulfate– Distribute over activated size range using
condensation/evaporation algorithm
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 8
TOMAS Status
• Wet deposition– In-cloud:
• Activated particles are removed same way as the original rainout (1st order loss).
• Interstitial particles are assumed inert.– Below-cloud: Apply size-resolved washout rate
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 9
TOMAS Status
• Dry deposition– Size-resolved scheme of Zhang et al (2001) as
in later versions of G-C
0.01 0.1 1 10
Dry particle diameter (m)
10
1
0.1
0.01
Deposition Velocity (cm s-1)
Original
New
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 10
Aerosol Prediction from TOMAS
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 11
Model ResultsTotal Number Concentration (cm-3)
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 12
Model Results
Total Number Concentration (cm-3)
CCN(0.2%) (cm-3)Notice the
scale!
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 13
Model Results
Total Number Concentration (cm-3) CCN(0.2%) (cm-3)
Latitude Latitude
Pre
ssur
e [m
bar]
Nucleation region
Heavy pollution region
Tropical convection CCN removed with rain
Emitted as well as grown into CCN sizes
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 14
Model Results
Number Size DistributiondN/dLogDp (cm-3)
Industrial region, China
Sea-salt emission-Significant mass (Larger particle)-Fewer numbers.
Nucleated particles
Grow by condensation as they descend
Cloud processingFrom cloud top down to surface Bimodal dist.
Sulfate primary emission
Remote marine, Southern Ocean
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 15
Model Results
Number Size DistributiondN/dLogDp (cm-3)
Remote marine, Southern Ocean
L19
L17
L10
L1
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 16
Upcoming Tasks & Challenges
• Introducing 30-bin OC, EC, and dust
• Running 2x2.5 memory need for (30*(n+2)) aerosol tracers, where n=number of mass species
• OR … Running nested grid over ACE-Asia domain?
• Comparing aerosol prediction with number size distribution measured from ACE-Asia
11/4/07
Implementation Aerosol Microphysics in GEOS-Chem Win T. 17
Question?
Check out my poster about …
• Comparison with Heintzenberg marine aerosol data
• Inter-model comparison :
G-C, GISS GCM-II’ and GLOMAP