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Transpacific transport of anthropogenic aerosols:
Integrating ground and satellite observations with models
AAAR, Austin, TexasOctober 18, 2005
Colette Heald, Daniel Jacob, Rokjin Park, Becky Alexander, Duncan Fairlie, Allen Chu (GSFC), Robert Yantosca
ASIA
NORTHAMERICA
Clear Day
TRANSPACIFIC TRANSPORT OF ASIAN AEROSOLS
Most documented cases consist of transport of dust:
Despite their short lifetimes, aerosols can be transported across the Pacific and can affect North American air quality standards and visibility.
BUT Model simulations suggest that anthropogenic aerosols from Asia can ALSO be transported to the United States [Park et al., 2004]
April 16, 2001
Visibility reduction at Glen Canyon, Arizona due to transpacific transport of Asian dust
Asian contribution is comparable to
“natural” standardset by EPA Haze Rule (0.12 µgm-3)
CHALLENGE: OBSERVING AEROSOL COMPOSITION FROM SPACE TO QUANTITAVELY VALIDATE MODELS
Carbonaceousaerosols
Sulfate Dust
Sea SaltNitrate
SURFACE (variable reflectance properties)
What we wantto validate!
SATELLITE AOD
Assumptions:Optical PropertiesSize Distributions
Aerosol Distributionsetc.
A toughmeasurement
to make!
AEROSOL SPECIATED MASS CONCENTRATIONS
SIMULATED AOD
*DIFFERENT*Assumptions:
Optical PropertiesSize Distributions
etc.
What we are comparing!
Better basis for comparison: RADIANCE(Easan Drury, Harvard)
DIFFERENTIAL TRANSPORT OF AEROSOLS AND COOBSERVED FROM SPACE
March2001
Anthropogenic plume,similar for CO and aerosols (allowing for aerosol scavenging)
Biomass burning plume for CO – Not observed for aerosols
TRANSPACIFIC TRANSPORT (2001)
GEOS-CHEM underestimates MODIS observations by factor of ~2 in Spring
MODIS = MODerate resolution Imaging Spectroradiometer (launched EOS-Terra Dec 1999)GEOS-Chem = global CTM with coupled oxidant-aerosol simulation [Park et al., 2003; 2004]
peak Asian dust
ALSO
substantialanthropogenicaerosoltransport
MODIS AOD GEOS-Chem AOD Sulfate AOD Dust AOD
WHAT CAN AERONET OBSERVATIONS TELL US?
Is the model/MODIS bias primarily a model underestimate or a satelliteretrieval bias?
AERONET sites indicate a possible MODIS retrieval bias (not correlated with cloud cover).
MODISAERONETGEOS-CHEM
AN EXAMPLE OF TRANSPACIFIC TRANSPORT OF ASIAN AEROSOL POLLUTION AS SEEN BY MODIS
April 25, 2001
April 26, 2001
April 27, 2001
TRANSPACIFIC TRANSPORT EVENTS AT SURFACE SITES
Midway Island (central North Pacific)
4 transpacific events tracked at surface sites
IMPROVE Sites (NW United States)
IMPROVE obsGEOS-ChemGEOS-Chem (Asian)
IMPACT OF ASIAN SULFATE ON U.S. AIR QUALITY
Asian aerosols preferentially impact ground sites in the NW US.Observations at IMPROVE sites are elevated from mean when simulated Asian
influence is high
SimulatedAsian
NW US:0.18 μgm-3
Asianevents
NW US: 0.60 μgm-3
ObservedNW US:
0.72 μgm-3
ObservedduringAsianeventsNW US:
1.04 μgm-3
PROJECTED SOx EMISSIONS IN ASIA
Increasing SOx emissions from Asia will degrade North American air quality and present a further barrier to attainment of domestic air quality regulations
in the United States (eg. EPA Haze Rule)
courtesy: David Streets
One projection suggests that
emissions of SOx will more than
double in China between
1995-2020
[Streets & Waldhoff, 2000]
ORGANIC CARBON AEROSOL: IMPLICATIONS FOR TRANSPACIFIC TRANSPORT?
NORTHAMERICA
ASIA
High concentrations of OCaerosols measured in the FT
over Asia (not captured by models)[Heald et al., 2005]
ObservedSimulated
Asian air massesSulfate: 0.24 µgm-3
OC: 0.53 µgm-3
Twice as much OC aerosol as sulfate
observed at Crater Lake[Jaffe et al., 2005]
PACIFIC