Transcript Transpacific transport of anthropogenic aerosols and

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