sometimes, profiles of both CL51 are almost identical, sometimes occur significant differences. Those differences are largest where aerosol layers are. But sometimes they also occur also in clean regions. See some examples of 13 June and 14 June.

Comment from Vaisala:
The main reason for this is the different firmware version of the two units involving also different overlap functions, see Special topics/Overlap. There is also a small difference in instrument sensitivity that could be adjusted. This adjustment has been proposed by Vaisala on 16.07.

Correlation plots: