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