Quantifying the trans-Pacific transport of Asian pollution in the upper troposphere with Aura-MLS 2004-2006 observations

Tans-Pacific transport of Asian pollution has received considerable attention because of its global air quality and climate implications. It has been difficult to investigate long-range transport of pollution in the upper troposphere because of the lack of suitable observations. The launch of Aura-EOS, with its measurements of upper tropospheric carbon monoxide (CO) and ozone among other species, makes it possible for the first time to systematically examine long-range transport in the upper troposphere. In this study we present an analysis of the first two years (September 2004- September 2006) of Aura-MLS upper tropospheric observations of CO and ozone, in conjunction with a global 3-D chemical transport model (GEOS-CHEM), with a focus on (1) quantifying the temporal variability (i.e., frequency and strength) of trans-Pacific transport of Asian pollution in the upper troposphere, (2) delineating transport events in the upper troposphere from the ones in the middle and lower troposphere by combining and contrasting MLS and MOPITT observations of CO, and (3) examining the preferred meteorological conditions and associated processes including warm conveyor belt (WCB) that are responsible for these upper troposphere trans-Pacific transport of pollution.