Acid Deposition Atmospheric Processes in Eastern North America (1983) / Chapter Skim
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Appendix B: Transport and Dispersion Processes
Appendix B: Transport and Dispersion Processes
Pages 202-213
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From page 202... ...
. CLASSIFICATION OF TRANSPORT PHENOMENA Atmospheric motion and transport phenomena are extremely complex in both horizontal and vertical dimensions, with thermal layering, shear turbulence, convection, variation of boundary characteristics, and so on.
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From page 203... ...
Because most atmospheric pollutants are released in this layer, study of the PBL is vital to understanding local or mesocale transport as opposed to synoptic or global transport. LOCAL AND MESOSCALE SPORT Mesoscale transport is usually confined to the planetary boundary layer or the lowest 3 km.
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From page 204... ...
In general, mesoscale mean winds dominate plume transport, but, depending on the strength of local turbulent eddies, the plume may also be spread horizontally and vertically. Another factor affecting pollutant transport is wind shear.
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From page 206... ...
Important mesoscale factors such as release height and diurnal and seasonal variabilities must not be neglected in long-range transport modeling. SYNOPTIC- OR CONTItIENTAL-SCALE TRANSPORT Synoptic transport of pollutants, especially acids and acid precursors, has been one of the major thrusts in acid deposition research.
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From page 207... ...
The network of balloon soundings produces, unfortunately, sparser data coverage than the precipitation chemistry measurements over eastern North America. Considering the spacing of upper-air measurements, it is optimistic to expect the knowledge of the direction of the prevailing wind at an arbitrary location in space and time to be known to better than 5° about the "actual" adverting wind.
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From page 208... ...
Louis, Missoun, personal communication (1982~. daytime mixed layer when moving either from south to north or from west to east owing to lowered mixed depths along the trajectory.
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From page 209... ...
SU8C ~ . 2S FIGURE B.4 Contour plots of maximum afternoon mixing depths by season, indicating qualitative patterns only.
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From page 210... ...
has pointed out that the south central United States is particularly subject to stagnating anticyclones, leading to lower ventilation of local and adverted emissions. Another factor critical to long-range transport is precipitation, which removes pollutants in a sporadic way.
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From page 211... ...
Early estimates were made that North American contribution to sulfate in rain in Norway could be important. More recent studies in Bermuda indicate that trans-Atlantic transport of acid precursors is important to the acidity of precipitation on the island (Jickells et al.
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From page 212... ...
1972. Mixing heights, wind speeds, and potential for urban air pollution throughout the contiguous United States.
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From page 213... ...
Precipitation processes tend to be rather complicated, however, and currently a high level of uncertainty exists regarding their mathematical characterization. Dry deposition, on the other hand, tends to be extremely difficult to measure, and the corresponding data set is relatively meager.
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