Question

how were the original measurements of increases in chlorine monoxide and the stratospheric ozone depletion over Antarctica obtained

Answer 1

Chlorine monoxide is a heavier gas compared to other gases. It is however mixed continuously and reaches stratosphere where it dissociates into chlorine and oxygen radicals. The chlorine radical then reacts with an ozone molecule to form oxygen and chlorine monoxide. Thus formed chlorine monoxide reacts with another ozone to form two oxygen molecule and an chlorine radical. Thus the process continues to be a chain reaction and one molecule of chlorine monoxide destroys several ozone molecules. Initial data was collected from satellite images and computer modeling experiments. The first confirmatory results were published on the antarctica depletion and ozone hole after several of these data were carefully analyzed by scientists. Over the years the hole has been found to be stable and not changing in size over the antarctic region.