A BBC forecaster kept saying yesterday that the sun index is higher than you
would normally expect at this time of year. What exactly did he mean?
Presumably not that the output from the sun is higher than normal!

If he was referring to the atmospheric conditions, what should be expected
at this time of year?

Phileas

Yes I noticed this on the 1357 forecast on BBC New 24. I would have thought
the factor was directly related to the sun's elevation. Is there something
special about the clarity of the air? I suspect it's just a bit of rather
careless, off the cuff, wording.
Cheers
John
--
York,
North Yorkshire.
(Norman Virus Protected)

"Phileas" wrote in message
...
A BBC forecaster kept saying yesterday that the sun index is higher than
you
would normally expect at this time of year. What exactly did he mean?
Presumably not that the output from the sun is higher than normal!

If he was referring to the atmospheric conditions, what should be expected
at this time of year?

Phileas

On Sun, 16 May 2004 12:52:57 GMT, Phileas wrote in


A BBC forecaster kept saying yesterday that the sun index is higher than you
would normally expect at this time of year. What exactly did he mean?
Presumably not that the output from the sun is higher than normal!

If he was referring to the atmospheric conditions, what should be expected
at this time of year?

I saw that forecast as well. Mention was made that UV radiation would be
as high as in mid June and similar to southern areas of France at present.
I can only guess this is down to depleted ozone levels above us now. This
site seems to suggest that may be a factor, as it shows the UV indices off
SW England and Ireland to be very similar to places such as N Turkey and N
Italy.

http://www.dmi.dk/dmi/index/verden/u.../uv_europa.htm

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 16/05/2004 15:27:43 UTC

My interpretation was simply that it is mid May now and that the sun is
almost as high as mid July. People realise that the sun can be warm in mid
July but they may think that the sun is not as powerful in May especially as
it has been quite unsettled and cool in many places this month up to the
other day. So with people flocking out into the sun this Weekend probably
exposing themselves to its rigours for the first time this year it was just
a warning that the sun is as powerful as mid July.
Incidentally for those who followed my posts earlier in the year about a
candidate for the 'coldest place in Europe' south west of Vienna it has been
snowing there for much of today and there still is quite a depth of snow
covering the ground at a modest height of 1600 metres.

Ian Currie-Coulsdon
www.Frostedearth.com




"John Whitby" wrote in message
news:64Lpc.43$OS1.30@newsfe1-win...
Yes I noticed this on the 1357 forecast on BBC New 24. I would have
thought
the factor was directly related to the sun's elevation. Is there
something
special about the clarity of the air? I suspect it's just a bit of rather
careless, off the cuff, wording.
Cheers
John
--
York,
North Yorkshire.
(Norman Virus Protected)

"Phileas" wrote in message
...
A BBC forecaster kept saying yesterday that the sun index is higher than
you
would normally expect at this time of year. What exactly did he mean?
Presumably not that the output from the sun is higher than normal!

If he was referring to the atmospheric conditions, what should be
expected
at this time of year?

Phileas

"Mike Tullett" wrote in message
...
On Sun, 16 May 2004 12:52:57 GMT, Phileas wrote in


A BBC forecaster kept saying yesterday that the sun index is higher than
you
would normally expect at this time of year. What exactly did he mean?
Presumably not that the output from the sun is higher than normal!

If he was referring to the atmospheric conditions, what should be expected
at this time of year?

I saw that forecast as well. Mention was made that UV radiation would be
as high as in mid June and similar to southern areas of France at present.
I can only guess this is down to depleted ozone levels above us now. This
site seems to suggest that may be a factor, as it shows the UV indices off
SW England and Ireland to be very similar to places such as N Turkey and N
Italy.

http://www.dmi.dk/dmi/index/verden/u.../uv_europa.htm

There is an ozone map of Europe here;
ftp://jwocky.gsfc.nasa.gov/pub/eptom...L_LATEST_N.GIF

Cheers, Alastair.

On Sun, 16 May 2004 18:46:26 +0100, Alastair McDonald wrote in


I saw that forecast as well. Mention was made that UV radiation would be
as high as in mid June and similar to southern areas of France at present.
I can only guess this is down to depleted ozone levels above us now. This
site seems to suggest that may be a factor, as it shows the UV indices off
SW England and Ireland to be very similar to places such as N Turkey and N
Italy.

http://www.dmi.dk/dmi/index/verden/u.../uv_europa.htm

There is an ozone map of Europe here;
ftp://jwocky.gsfc.nasa.gov/pub/eptom...L_LATEST_N.GIF

Thanks Alastair. The pattern there fits in with the greater amounts of UV
in western Europe compared with the south east and east. Trouble is, I am
clueless about the O3 values. That map shows a range from about 325 DU
over the nearby Atlantic to about 425 DU in E and SE Europe.

--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 16/05/2004 18:39:29 UTC

On Sun, 16 May 2004 17:05:33 +0100, Ian Currie wrote in

"John Whitby" wrote in message
news:64Lpc.43$OS1.30@newsfe1-win...
Yes I noticed this on the 1357 forecast on BBC New 24. I would have thought
the factor was directly related to the sun's elevation. Is there something
special about the clarity of the air? I suspect it's just a bit of rather
careless, off the cuff, wording.

My interpretation was simply that it is mid May now and that the sun is
almost as high as mid July. People realise that the sun can be warm in mid
July but they may think that the sun is not as powerful in May especially as
it has been quite unsettled and cool in many places this month up to the
other day. So with people flocking out into the sun this Weekend probably
exposing themselves to its rigours for the first time this year it was just
a warning that the sun is as powerful as mid July.

My impression, from the words used, was it was unusual for mid May. The UV
index forecast for today was 7 in parts of the south. How accurate the
following is I don't know, but it was taken from:

http://www.weatheronline.co.uk/ukweather.htm

quote
The strength of the sun's ultraviolet (UV) radiation is expressed as a
Solar UV Index or Sun Index.The UV Index does not exceed 8 in the UK (8 is
rare; 7 may occur on exceptional days, mostly in the two weeks around the
summer solstice). Indices of 9 and 10 are common in the Mediterranean area.
The Sun Index forecast refers to the daily maximum.
endquote

I hope no-one used this page in N.I. today, as its forecast for here was
only a 1 :-)

http://www.met-office.gov.uk/weather/uv/uv_uk.html


--
Mike 55.13°N 6.69°W Coleraine posted to uk.sci.weather 16/05/2004 18:48:37 UTC

"Mike Tullett" wrote in message
...
On Sun, 16 May 2004 18:46:26 +0100, Alastair McDonald wrote in


I saw that forecast as well. Mention was made that UV radiation would be
as high as in mid June and similar to southern areas of France at
present.
I can only guess this is down to depleted ozone levels above us now.
This
site seems to suggest that may be a factor, as it shows the UV indices
off
SW England and Ireland to be very similar to places such as N Turkey and
N
Italy.

http://www.dmi.dk/dmi/index/verden/u.../uv_europa.htm

There is an ozone map of Europe here;
ftp://jwocky.gsfc.nasa.gov/pub/eptom...L_LATEST_N.GIF

Thanks Alastair. The pattern there fits in with the greater amounts of UV
in western Europe compared with the south east and east. Trouble is, I am
clueless about the O3 values.

Yes so am I. That's why I did not comment :-( I think in Antarctica the
normal value is 450 DU but I have a feeling it get less at the Equator.

I wonder if the air rising from the troposphere into the stratosphere
in the inter tropical convergence zone is ozone free, then as that
air travels polewards it gains ozone until it sinks out of the
stratosphere in the polar vortex.

That map shows a range from about 325 DU
over the nearby Atlantic to about 425 DU in E and SE Europe.

That would imply a 25% reduction over the UK at present.

Here is the site I was looking for;
http://freespace.virgin.net/mike.trigger/ozone.htm

See this link to confirm that an ozone hole has moved over the UK!
http://freespace.virgin.net/mike.trigger/ozloop.htm

Cheers, Alastair.

Thanks Alastair. The pattern there fits in with the greater amounts of UV
in western Europe compared with the south east and east. Trouble is, I am
clueless about the O3 values.

Yes so am I. That's why I did not comment :-( I think in Antarctica the
normal value is 450 DU but I have a feeling it get less at the Equator.


I study these maps fairly regularly and I'd say the average for this
latitude is about 330 DU. Antarctica averages about the same, except during
the Ozone Hole season (Sept-Dec) when it can drop as low as 110 DU and is
rarely over about 150 DU. The ozone over Europe looks pretty normal to me,
maybe just faintly lower than average over the UK, but definitely above average
well to the east.
Of course it's not only ozone that absorbs UV - just ordinary air
does it quite well, given enough of it. You simply can't get noticeably
sunburnt, except at high altitudes, with a solar elevation less than 20°,
roughly.

Tudor Hughes, Warlingham, Surrey.

I wonder if the air rising from the troposphere into the stratosphere
in the inter tropical convergence zone is ozone free, then as that
air travels polewards it gains ozone until it sinks out of the
stratosphere in the polar vortex
Erm,not quite.See eg-
http://www.atm.damtp.cam.ac.uk/people/mem/


--
regards,
david
(add 17 to waghorne to reply)