This note in the French AIP explains the difference between Meteorological Optical Range (MOR) and Aeronautical Visibility (VA). They can differ by a factor of up to 2x, taking into account background luminescence.
It seems that RVR is normally reported using VA, so IFR pilots won’t be affected, but VFR reported visibility is likely to be improved (if I have understood it correctly).
Does this affect any other countries?
Could you elaborate a bit. It’s not clear to me what is “improved”, or what the change is exactly?
This was interesting, and a bit surprising. That would mean that by night, the difference between VIS and RVR will be much smaller than today, if any.
The comment in section 5 that the currently given VIS is a measure of the “atmospheric transparency” is exactly was I was taught in IFR ground school in the 80’s.
I read the note.
until now some (all?) aerodrome in France offering METARs would give visibility as MOR (excluding RVR of the subject)
Due to SERA it should now be given as VA, and therefore all non-equipped aerodrome should be retrofitted with the appropriate sensors to give visibility as VA (and not MOR anymore)
The note goes on explaining the difference and providing figures comparing VA/MOR in which you can see that VA can be up to 4x more favorable.
They give an example that a MOR visibility of 1000m would be measured at 2000m with VA
The “improvement” is that with this, VFR flight would be less likely limited by visibility factors (not that it is often the case in my experience…)
I wondered if this affected any other countries apart from France. I hadn’t seen this side-effect of SERA anywhere else. Do other places already use VA (or are they just ignoring the issue for now)?
PapaPapa, your analysis confirmed by understanding – so I think this should be especially helpful for night VFR
