Transcript Transpacific transport of anthropogenic aerosols and

Organic Carbon Aerosol:
An Overview
(and Insight from Recent Field Campaigns)
Colette L. Heald
NOAA Climate and Global Change Postdoctoral Fellow
([email protected])
*New Affiliation as of Jan 2008*
Colorado State University
GEOS-Chem User’s Meeting
April 12, 2007
ORGANIC CARBON AEROSOL
SemiVolatiles
Nucleation or Condensation
Secondary
Organic
Aerosol
Primary
Organic
Aerosol
Oxidation
by OH, O3, NO3
Isoprene
Terpenes
Aromatics
Direct
Emission
Fossil Fuel
BIOGENIC SOURCES
Biomass
Burning
ANTHROPOGENIC SOURCES
GEOS-CHEM OC AEROSOL SIMULATION
Secondary Organic Aerosol
[Rokjin Park, Hong Liao, Daven Henze]
Terpenes: Chung and Seinfeld [2002]
Isoprene: Henze and Seinfeld [2006] (v7.04.05)
Aromatics: new smog chamber data (Henze)
Heterogeneous Chemistry: glyoxal (May Fu)
Primary Organic Aerosol
[Rokjin Park]
SOA treated as hydrophilic, semi-volatile gases are soluble
FF: Cooke / Bond
BF: Logan & Yevich
BB: Duncan
Empirical parameterization: 2-product
model fit to smog chamber studies
VOC + Oxidant  α1 P1 + α2 P2
Equilibrium Partitioning
Depends on T, [OC]
k1
k2
50% hydrophobic, 50% hydrophillic
GLOBAL OC BUDGET IN GEOS-CHEM
SOURCE
Fossil Fuel
Biofuel
TgC/yr
10.6
7.6
Biomass Burning
Terpene SOA
Isoprene SOA
Aromatic SOA
~25
9
5.5
~4
Glyoxal/methylglyoxal uptake May’s talk!
[Park et al., 2003; Henze and Seinfeld, 2006]
ORGANIC CARBON AEROSOL: AT THE SURFACE
2004 NARSTO Assessment
Organic carbon constitutes 10-70% of aerosol mass at surface.
ISSUE: Measurements do not differentiate POA and SOA
ACE-ASIA: FIRST OC AEROSOL MEASUREMENTS
IN THE FREE TROPOSPHERE
(ACE-Asia aircraft campaign conducted off of Japan during April/May 2001)
[Mader et al., 2002]
+
[Huebert et al., 2003]
Mean Observations
Mean Simulation
Observations
[Maria et al., 2003]
v7.01.02
(only terpene SOA)
Concentrations of OC in the FT were under-predicted by a factor of 10-100!
We conclude this is missing SOA
[Heald et al., 2005]
SEVERAL STUDIES SUGGESTING UNDERESTIMATE
OF SOA
[Volkamer et al., 2006]
Global underestimate in SOA?
WHAT CONTRIBUTES TO OC AEROSOL OVER
NORTH AMERICA?
Observed boreal fire
Influence down-wind
NOAA WP-3 Flight tracks
2004: worst fire season
on record in Alaska
BB filtered
using CH3CN
OC concentrations in the FT doubled as a result of Alaskan boreal fires.
DO WE UNDERSTAND OC AEROSOL OVER
NORTH AMERICA?
Sulfur Oxides (SOx)
Simulated source
attribution
Water soluble
OC Aerosol (WSOC)
Observed
Simulated
v7.02.04
(includes isoprene SOA)
OC aerosol concentrations 4x lower than observed off of Asia,
model within 25%
BUT we cannot simulate variability in observations (R=0.21)
 incomplete understanding of formation.
Note: biomass burning plumes were removed
[Heald et al., 2006]
WHAT DON’T WE UNDERSTAND ABOUT SOA FORMATION?
Cloud
Processing
CHEMISTRY
1. NOx, SO2/acidity
2. Multi-step oxidation
SVOC
SOA: ?? TgC/yr
FORMATION PATHWAYS
Nucleation or Condensation
Heterogeneous Reactions
PRECURSORS
Oxidation
by OH, O3, NO3
Isoprene
OC
Terpenes
FF: 45-80 TgC/yr
BB: 10-30 TgC/yr
Aromatics
Direct
Emission
Fossil Fuel
BIOGENIC SOURCES
Biomass
Burning
ANTHROPOGENIC SOURCES
MODELING OC AEROSOL: FUTURE?
Implementation of smog-chamber results
• Better constraints on role of NOx, seed particles,
T, RH, and radiative properties
In-cloud SOA formation
• CMAQ (A. Carlton)
New SOA Schemes?
• Example: Donahue volatility basis sets
Semi-volatile primary emissions?
• Robinson and Donahue suggest
primary aerosol emission is
misconception…
ACKNOWLEDGEMENTS
Daniel Jacob, Rokjin Park, Solène Turquety, Rynda Hudman
Lynn Russell
Rodney Weber,
Amy Sullivan
Rick Peltier
Barry Huebert
John Seinfeld,
Hong Liao
ITCT-2K4 Science Team
Hosts: Inez Fung &
Allen Goldstein