No. 51: May-Jun 1987
"One more mystery has been added to the seasonal loss of ozone in the stratosphere over Antarctica. It now appears that the 'hole' is an uneven one, with 2- to 3-kilometer-thick slices of ozone-poor air sandwiched within layers of only minimal depletion."
These new data came from McMurdo Sound, where a series of balloons carrying ozone sensors were released. Ozone depletion seems to be confined to the region 12-20 kilometers altitude and the top of the stratosphere. The overall depletion in this region was 35% at the time the balloons were lofted. However, some zones from 1 to 5 kilometers thick showed depletions as great as 90%. The reason for this stratificaiton is not yet known.
(Silberner, J.; "Layers of Complexity in Ozone Hole," Science News, 131:164, 1987.)