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RESIDENCE TIME OF ATMOSPHERIC POLLUTANTS AND LONG-RANGE TRANSPORT
Citation:
Henmi, T., E. Reiter, AND R. Edson. RESIDENCE TIME OF ATMOSPHERIC POLLUTANTS AND LONG-RANGE TRANSPORT. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/4-78/003.
Description:
The Lagrangian trajectory model which is suitable for the study of long-range transport of pollutants, is developed. The computer program is capable of calculating trajectories over the region of the U.S. using routine sounding data. The output consists of tables of locations of trajectory end points at each time-step, dispersion widths along a trajectory, and the plotting of trajectories. The regional residence times, T, of SO2 in the mixing layer are calculated for the region of the United States east of 105 degrees W longitude, based on climatological data of the mixing layer depth and hourly precipitation data. The results are shown as isopleths of T over the studied area for the cold season (November to April) and for the warm season (May to October). Taking detailed microphysical processes into consideration, the scavenging due to cumulus cloud precipitation is studied. The results can be summarized as follows: The scavenging coefficient of aerosols by cloudwater droplets is one order of magnitude larger in the continental cloud than in the maritime cloud. On the other hand, the scavenging coefficient of aerosols by rainwater droplets is slightly larger in maritime clouds than in continental clouds. As a whole, aerosols are more efficiently scavenged in the continental cloud than in the maritime cloud.