The BBC are reporting on the possibility of record UV levels today across IONA. I can never quite understand why the exact UV level isn’t used by the BBC Meteogroup in their TV forecasts, and why they have to be ‘simplified’ for the great British public to understand, perhaps it’s because we don’t see the high levels of UV levels people from sunnier climes do and can’t relate to the values.
As far as as the possibility of a record level in UV today goes, records of extreme UV levels maintained by the UKMO can only just be just over 25 years old because the exact definition for UV levels wasn’t ratified by the WMO till 1994.
Nick Miller explained in the 1 pm BBC news the reasons why UV radiation are at record levels today:-
- UV is at its highest around the time of the solstice.
- Scattering form the ozone in the upper atmosphere was not as high as usual.
- Less pollution due to the lock down.
It’s interesting that when I try this online UV calculator from NILU I can only seem to get a max of 5.7 for the UV ‘daily dose’ for our part of Scotland, ‘H’ must be as high as it goes up here. If you increase the elevation to the height of Ben Nevis you can get the daily dose up to 6.2.
I’ve tried most of the options but never managed to produce a nice graph like the one for New York.
Before I add the next graphic I will say for the record and before anyone drops me a line, I do realise that general hourly solar radiation as measured by an AWS and reported in SYNOP observations is not the same as a maximum or spot UV level reading. Anyway, here is a chart of hourly solar radiation at 13 UTC today. Why Nick Miller is talking about UV level records and not solar radiation levels is that there is a maximum value for solar radiation as the output from the sun fluctuates only minutely from year to year, whilst UV seems to be more open ended with UV levels of 10 or 11 common in the Tropics, and a disputed value of 43.3 reported from a Bolivian volcano.