Aerosol Working Group

The 7th International GEOS-Chem User’s MeetingMay 4, 2015

Aerosol WG Co-ChairsColette Heald: heald@mit.edu

Jeff Pierce (outgoing): jeffrey.pierce@csu.eduPeter Adams (incoming): petera@andrew.cmu.edu

To join email list send email to: geos-chem-aerosols-join@seas.harvard.edu

Why Aerosols in GEOS-Chem?

Air Quality

Ecosystem Health

Climate

Local VisibilityLRT

Acid RainNutrients

Why in GEOS-Chem rather than stand-alone aerosol model?Benefits from coupled oxidant simulation, enables multi-pollutant approach.

Why Aerosols (if I really only care about gas-phase)?

Heterogeneous Chemistry

Effect on Photolysis Rates[Martin et al., 2003]

Original: [Martin et al., 2003]N2O5: [Evans and Jacob, 2005]HO2: [Thornton et al., 2008]

Gas-Particle PartitioningISORROPIA II: [Foutoukis and Nenes, 2007]Implementation in GC: [Pye et al., 2009]

The History of Aerosols in GEOS-Chem

Carbonaceous Aerosols and Sulfate-Nitrate Ammonium based on GOCART

[Park et al., 2003] [Park et al., 2004]

Sea Salt Dust (DEAD Scheme with SOA (biogenic GOCART source map) anthropogenic, semi-vol POA)

[Alexander et al, 2005; Jaeglé et al., 2011]

[Fairlie et al., 2007][Liao et al., 2007; Henze et al., 2008;Pye et al., 2010]

• mass based scheme, assumes fixed log-normal size distributions• full-chemistry with or without SOA (only without is benchmarked), also aerosol-only

Sectional Scheme Option: TOMASTwO-Moment Aerosol Sectional microphysics scheme

(maintained by Marguerite Marks, Jack Kodros, Jeff Pierce and Peter Adams)

• Explicit simulation of the aerosol size distribution.

Features • Aerosol number and mass simulated in 12, 15, 30 or 40 size sections

• Explicit aerosol number balance• 4x5, 2x2.5 and 0.5x0.666 nested grid• GEOS-Chem aerosol species incorporated into size sections• Sulfate, primary OC, SOA, EC, sea salt, dust

• In the Pipeline:• HEMCO compatability• tagging

Aerosol/climate effects and aerosol-size/heath effects

Sectional Scheme Option: APM(maintained by Gan Luo and Fangqun Yu, UAlbany)

Secondary particles (SP) : 40 bins

Sea salt particles: 20 bins

Dust: 15 bins

BC : 4 log-normal modes

.

Size-resolved microphysics with variable size resolution for particles of different types and sizes

Recent advances(1) Integrated aerosol optical depth (AOD) and surface

area based on APM aerosols with photo-chemistry and heterogeneous chemistry

(2) Integrated cloud optical depth (COD) based on APM aerosols and explicit cloud droplet activation scheme with photochemistry

(3) Added tracers and processes to predict global concentrations of amines

(4) Updated APM has been integrated into v9.2.0

(5) APM works with 0.25ox0.3125o nested domains

GC-APM AeroCom II participation1) Aerosol direct radiative forcing (Myhre et

al., 2013)2) Host model uncertainties in aerosol

radiative forcing estimates (Stier et al., 2013)

3) Aerosol microphysics (Mann et al., 2013)4) Aerosol organics (Tsigaridis et al., 2014)

Primary OC: 4 log-normal modes

Mixing states: Semi-externally mixed, with coating of primary particles by secondary species explicitly simulated

Research Topics Being Investigated in the WG• Aerosol chemistry (eg. sulfate formation, SOA, aqueous chem)• Black carbon and combustion aerosol• Regional AQ• Historical aerosol trends, future aerosol projections (AQ and climate)• Satellite-based PM2.5 estimation

• Inverse PM2.5

estimation • Long range transport and impacts• Precursor emission estimation, including for new satellite products (eg. NH3, SO2)• Estimating associated health impacts• Aerosol microphysics:

• New particle formation, optics, mixing state, direct effect, indirect effect, geoengineering

• Removal processes• Sea-salt impacts on tropospheric chemistry

Progress since IGC6

v9-02

● TOMAS parallelization and speed-up options (Pierce/Adams)● Heterogeneous chem updates... HO

2, N

2O

5) (Mao)

● NH3 emissions updates (Zhang/Lo)

● GFED3 emissions through 2011 (Kasibhatla)● SOA with semi-volatile POA (Pye)● Cloud-water pH for sulfate formation (Alexander)

Coming soon: v10-01

● Stratospheric aerosol chemistry through UCX (Barrett/Eastham)● Lots of emissions updates relevant to aerosols (HEMCO, GFED,4

EDGAR4.2, MIX, NEI2011, EMEP)

Important Capabilities in the Pipeline

• RRTMG online (Ridley/Heald, v10-01)• Simplified description of uptake of SO2, nitric acid and sulfuric acid on mineral

dust (Fairlie, v10-02)• Aerosol thermodynamics and microphysics from MOSAIC (Eastham, TBD)• Impaction scavenging for hydrophobic BC and homogeneous IN removal (Wang,

TBD)• Others?

Challenges Ahead, Topics for Discussion• Maintaining 3rd party code (TOMAS, APM, RRTMG, ISORROPIA, MOSAIC)• Full integration of gas and particle phase chemical mechanism• Modernizing aerosol optics• The future of SOA (multiple options?)• BC aging• Others??