Material dispersion in a convective field

The dispersion mechanism of a plume in a convective field is considered here as being due to mixing between updraft and downdraft regions, and the dispersion pattern is examined from both elevated and ground sources. For elevated sources, the maximum concentration descends first to ground level at some distance downwind and then rises, depending on inversion depth, mean wind, and material release height. The updrafts have a higher velocity than the downdrafts, and consequently the downdrafts occupy a larger horizontal area. In some cases, the updrafts and downdrafts are comparable and materials are released alternatively in the downdraft and updraft, the concentration is split into two, one moving downward and the other upward. The high shear layer against the surface modifies the mixing processes at the base of the plumes and this causes the materials to disperse more both in the upwind and crosswind directions.