The transport of tropospheric ozone, ozone precursors, carbon monoxide, etc from Asia to North America is an active area of research (see J.L. Ambrose, et al., 2011) These types of events occur rather dramatically in the springtime, apparently due to meteorological conditions when westerly winds are strong, which carries polluted air across the Pacific. Stratospheric ozone events can be differentiated because they have low moisture and no associated increase in carbon monoxide.
What meteorological factors contribute to the increased transport of Asia-generated air pollution to North America? What occurs meteorologically in the springtime that leads to more westerly transport than any other season? The analyses I've seen say that transport can occur anywhere from 2.5 km to 8 km above sea level.
Are there factors that could cause temporal or spatial shifts in how these types of pollution transport events are recepted in North America?
Image from M. Lin et al., 2011 publication showing carbon monoxide crossing the Pacific Ocean caught by Aqua/AIRS, (1018 molecules / cm2)