Long-range Transport of Asian Pollution to North America: Transport, chemistry and variability

Qing Liang and Lyatt Jaeglé

University of Washington, Seattle

Meteorological Indices for Asian Outflow and Transpacific Transport on Daily to Interannual Timescales

Model: GEOS-CHEM Tagged CO simulation10 year simulation (1992-2002), 2˚x2.5˚

Use seasonal climatological biomass burning and same OH field for each year.

MethodCorrelate tagged Asian CO tracer with Sea Level Pressure (SLP) to form simple transport indices

Liang et al. [2005], submitted to J. Geophys. Res.

Daily variability in Asian Outflow

Asian Outflow Index: SLP anomalies over NE China

Cyclones over NE China favors exportAsian CO

R (Asian CO, SLP)

R = 0.38-0.47

SLP anti-correlated with export

1993

Daily variability in transpacific transportTranspacific Transport index: SLP anomalies in E. Pacific

Strong Pacific High favors transpacific transport

Asian CO

R (Asian CO, SLP)

R = 0.27-0.53

SLP correlated with transport

1993

Interannual variability of Transpacific Transport

R = 0.65 Enhanced Transpacific Transport

Monthly Asian CO in the western North America is correlated with the meridional SLP gradient

Index: Weighted SLP anomalies over the N. Pacific

Winter & Spring

What drives the interannual variability of transpacific transport?

LRT3 strongly projects on Pacific and North American (PNA) indexR(LRT3, PNA)=0.69 for 1948-2004

Enhanced Transpacific Transport

Summertime influence of Asian pollution in the middle and upper troposphere during INTEX-A

INTEX-A: 18 flights, Jun. 29 – Aug. 14, 2004 Goals and Methods

What was the extent of Asian influence over the U.S. during INTEX-A?

Use GEOS-CHEM to identify Asian plumes in observations, characterize their composition, and elucidate their chemical evolution and transport mechanisms

Asian plumes sampled during INTEX-A (Modeled Asian CO > 25-30 ppbv)6 Asian plumes

Asian CO

GEOS-CHEMModel

Observ.

Chemical Composition of Asian Plumes

Observed Δ Model Δ

CO, ppbv +19 +6

O3, ppbv +23 +13

HNO3, pptv -8 +20

PAN, pptv +97 +4

Acetylene, pptv +47

Enhancement in Asian Plumes vs. Background

Modeled Asian CO [ppbv]

Asian Plume

DIAL+ In Situ O3 Observations [ppbv]

1 2 3

July 1, 2004 – Asian Plume

12

3

Future work

Chemical properties and evolution of the Asian plumes

Origin of discrepancy between model and observations (transport, STE, chemistry?)

Impact on Ozone in UT over US

Was transpacific transport during INTEX-A unusual?