Time series of ClO over Kiruna lasting from 28 January to 2 February 1998. The lower ClO layer
at about 20 km and its diurnal variation indicating chlorine activation can clearly be seen. This
diurnal variation ist the result of the formation of the ClO dimer in the night. In the morning
after sunrise this ClO dimer is photolyzed and ClO is released again. There is a weaker diurnal
variation of the upper ClO layer at about 35 km due to the photolyses of chlorine nitrate which
is indicated in the graph.