Nicholas Randall wrote:

On Wednesday, 27 May 2020 10:38:20 UTC+1, Norman Lynagh wrote:
Graham Easterling wrote:


I agree with most of what you state about factors that affect UV
levels except humidity. I do not think it affects them.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

Equally, I am sure it does. If Norman reads this I know he'll
agree. In fact, anyone that spends a lot of time outdoors,
certainly on the coast of SW England where high humidity is
common, fully appreciates the fact.

How else do you explain the big drop in UV when a cold front goes
through? Certainly lower high level ozone sometimes being
associated with a warm sector ridge is partly the cause, but the
whole thing? If you don't except it's the humidity, despite the
evidence, you need to come up with an alternative explanation why
it's so high in air which has none of the clarity of that behind
the cold front.

Somewhere I'v got a list of times when the Camborne UV has hit 9,
never in clear, clean sunny mP conditions.

Graham
Penzance

I can't comment on actual UV measurements but, from personal
experience, for any given temperature I find that I burn more
readily in high humidity conditions than in dry conditions. In
coastal, fairly humid conditions, in this country with the temp in
the low 20s I burn much more than I do in 40° in very low humidity
in inland Australia. Indeed, I have to be very careful in this
country on summer days when there is a complete cover of low cloud
but nothing above it. On such days, if unprotected, I would burn
very badly.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr

Where in inland Australia are you referring to? The temperature is
not linked to UV levels. It is about how high the sun is in the sky
and the latitude. Lower latitudes will have higher UV levels than
higher latitudes.

Nicholas
Meir Heath, Stoke-On-Trent 250 metres above sea level.

Many places, including wide areas in the Northern Territory and North
Queensland. Also some places in nothern WA.

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.
https://peakdistrictweather.org
twitter: @TideswellWeathr