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SUMMARYDispersion from a puff released in the atmospheric boundary layer in mid-latitudes is simulated with a Lagrangian global multiple-particle model using analysed three-dimensional wind fields. Quantitative measures of the spread are computed and used to assess the influence of the synoptic system into which the puff is released, and the ways in which turbulent diffusion can contribute to the total spread. The nature of the dispersion over ten days is examined to elucidate the controlling meteorology and kinematics during the various phases which could be identified. The results are compared with measurements made from constant-level balloons. A time index is proposed to characterize large-scale dispersion from a point source.

ß . , ß , ß ß , ß . A photochemical model consisting of 40 species and 107 reactions is integrated along 80 day air parcel trajectories calculated in the lower stratosphere for the springtime Antarctic. For the trajectory starting at 58øS, which may be regarded as outside the circumpolar vortex, only a small change in 0 3 occurs in the model. In contrast, for the air parcel starting in the vortex at 74øS, the 03 Concentration is reduced by 93% during the 80 days from the beginning of August to late October. The model results for several species are compared with measurements from the Airborne Antarctic Ozone Experiment and, in general, good agreement is obtained. In the model, the denitrification of the air parcels in polar stratospheric clouds increases the amount of chlorine present in active form. Heterogeneous reactions maintain high active chlorine which destroys 03 via the formation of the C10 dimer. Results of calculations with reduced concentrations of inorganic chlorine show ocnsiderably reduced 03 destruction rams and compare favorably with the behavior of total 03 Since the late 1970s. The remaining major uncertainties in the photochemical aspects of the Antarctic ozone hole are highlighted.

Dispersion from a puff released in the atmospheric boundary layer in mid‐latitudes is simulated with a Lagrangian global multiple‐particle model using analysed three‐dimensional wind fields. Quantitative measures of the spread are computed and used to assess the influence of the synoptic system into which the puff is released, and the ways in which turbulent diffusion can contribute to the total spread. the nature of the dispersion over ten days is examined to elucidate the controlling meteorology and kinematics during the various phases which could be identified. the results are compared with measurements made from constant‐level balloons. A time index is proposed to characterize large‐scale dispersion from a point source.