Estimating the average time for inter-continental transport of air pollutants

[1] We estimate the average time required for intercontinental transport of atmospheric tracers based on simulations with the global chemical tracer model MOZART-2 driven with NCEP meteorology. We represent the average transport time by a ratio of the concentration of two tracers with different lifetimes. We find that average transport times increase with tracer lifetimes. With tracers of 1and 2-week lifetimes the average transport time from East Asia (EA) to the surface of western North America (NA) in April is 2–3 weeks, approximately a half week longer than transport from NA to western Europe (EU) and from EU to EA. We develop an ‘equivalent circulation’ method to estimate a timescale which has little dependence on tracer lifetimes and obtain similar results to those obtained with short-lived tracers. Our findings show that average intercontinental transport times, even for tracers with short lifetimes, are on average 1–2 weeks longer than rapid transport observed in plumes. Citation: Liu, J., and D. L. Mauzerall (2005), Estimating the average time for intercontinental transport of air pollutants, Geophys. Res. Lett., 32, L11814, doi:10.1029/2005GL022619.