For more information see the PARS Instrument web page.
It has been observed at several sites, that the visibility drops out on the PARS2 even when there are clear conditions or when precipitation is not being reported. It turns out, that the instrument has a light path that can be blocked by fog which then affects the visibility.
The PARS is currently located at ENA, AMF1, and AMF2.
Document some known issues and past problems here.