I thought I would pose this question here as there is a concentration of retired and (maybe?) current Met Office staff here with experience of observation networks.

In the current issue of Weather - in Weather Log - we find that 14 of the 21 UK sites listed give figures for days with snow lying and fog. Meanwhile, a further 4 just have a fog figure. 3 sites have no such data at all. My question is - does the existence of data imply that a station is staffed or part or maybe all of a day or is it simply a reflection of the appropriate sensor being installed? Are the observations comparable - for example, the snow depth sensor cannot find a representative patch of ground in the enclosure as the human can.

On a separate issue, no sunshine data is now available for Valley, Durham and Cambridge, each sites with long term records of sunshine on the old Campbell-Stokes instrument. (off hand I can't remember if it is Cambridge NIAB or the Botanic Gardens shown). It is even worse for the Europe list, including many capital cities which really must have sunshine data.

Many thanks, Julian
Molesey, Surrey.

On Monday, March 2, 2020 at 12:11:22 PM UTC, Julian Mayes wrote:
I thought I would pose this question here as there is a concentration of retired and (maybe?) current Met Office staff here with experience of observation networks.

In the current issue of Weather - in Weather Log - we find that 14 of the 21 UK sites listed give figures for days with snow lying and fog. Meanwhile, a further 4 just have a fog figure. 3 sites have no such data at all. My question is - does the existence of data imply that a station is staffed or part or maybe all of a day or is it simply a reflection of the appropriate sensor being installed? Are the observations comparable - for example, the snow depth sensor cannot find a representative patch of ground in the enclosure as the human can.

On a separate issue, no sunshine data is now available for Valley, Durham and Cambridge, each sites with long term records of sunshine on the old Campbell-Stokes instrument. (off hand I can't remember if it is Cambridge NIAB or the Botanic Gardens shown). It is even worse for the Europe list, including many capital cities which really must have sunshine data.

Many thanks, Julian
Molesey, Surrey.

I have never worked for the MetO, but my observation is that days of fog reported are highly misleading for a host of reasons

In the case of Camborne (manned) the issues are down to the 'fog in the vicinity' being reported as fog. (Camborne is close to an area prone to sea fog.) On one occasion Camborne recorded fog all day, when it was also the sunniest place in the UK (according to the MetO)

In reverse, Scilly (unmanned) can report sun all day when it's foggy. I did query that and got a reply that it was 'feature of the equipment used'. On a par when I queried different forecasts for St. Marys, Scilly heliport & airport, when they are the same place and got the reply the forecasts are different because 'they are based on different locations.'

The whole reporting of 'fog' seems a bit of a mess to me, as the recent fog at 09:00 thread shows. Not that the reporting of reduced visibility due to snow is a particular issue in Penzance!

Graham
Penzance

In the case of Camborne (manned) the issues are down to the 'fog in the vicinity' being reported as fog. (Camborne is close to an area prone to sea fog.) On one occasion Camborne recorded fog all day, when it was also the sunniest place in the UK (according to the MetO)


I had the same issue when I was holiday relief observer at Penmaen, Gower. I can remember an April day when most of the UK was cloudless and warm but it was a day of fog at 09h there - 500m from the Bristol Channel and the cliffs of Three Cliff Bay. A tiny area of advection fog was pouring up (if you see what I mean) the top of the cliffs and was visible for much of the morning. Not a bad place to have as a free holiday home though - for over 20 years, so I was happy to take whatever weather happened.

Julian

On 02/03/2020 12:11, Julian Mayes wrote:
I thought I would pose this question here as there is a concentration of retired and (maybe?) current Met Office staff here with experience of observation networks.

In the current issue of Weather - in Weather Log - we find that 14 of the 21 UK sites listed give figures for days with snow lying and fog. Meanwhile, a further 4 just have a fog figure. 3 sites have no such data at all. My question is - does the existence of data imply that a station is staffed or part or maybe all of a day or is it simply a reflection of the appropriate sensor being installed? Are the observations comparable - for example, the snow depth sensor cannot find a representative patch of ground in the enclosure as the human can.

On a separate issue, no sunshine data is now available for Valley, Durham and Cambridge, each sites with long term records of sunshine on the old Campbell-Stokes instrument. (off hand I can't remember if it is Cambridge NIAB or the Botanic Gardens shown). It is even worse for the Europe list, including many capital cities which really must have sunshine data.

Many thanks, Julian
Molesey, Surrey.

If you have access to the synops, these have codes which say weather
each station's observation was manned or automatic, whether there was
weather reported or not and info about precipitation.
AFAIK there are no synops now, it's all BUFR code. Ogimet (and others)
convert BUFR to SYNOP, but how accurate it is I don't know. It can get a
bit complicated if stations are only manned (personed?) for some of the
time - like Benson, my local Met station.
On the question of fog at coastal stations, I'm pretty sure that the
worst visibility is reported, but only inland. If fog is drifting onto
land just over the way, then the visibility can go up and down like a
yoyo. Perhaps that's what happened at Camborne - the fog was within
1000m but wasn't at the station - adjacent fog should have been reported.
The other issue, data at 0900, isn't that a throwback to when there were
no AWSs and many sites only reported climatologically. I suspect that
they are kept for consistency.
Are the climat reports online? I suspect that they have similar groups
to the SYNOPs. But trying to find decodes for these is a bit of a
nightmare. I have a decode for the SYNOP code, but it's quite old now.
And I left the Met Office eight years ago (this month), so I might be
completely out of date.
Where's Bruce when you need him!

Perhaps that's what happened at Camborne - the fog was within
1000m but wasn't at the station - adjacent fog should have been reported.

I think that's almost certainly the case. The Camborne site is around 2000m from an area of the north coast very prone to sea fog.

As for the 09:00 reporting time, whilst it many cases inland the fog has gone by then, on the coast it's often brought in by the sea breeze, so in summer the fog risk is higher later in the day.

There's an excellent photo of the onset of a north coast sea breeze causing a fog roller here, just passing Lands End. (Moving right to left) associated with the early afternoon onset of the north coast sea breeze. 5th Aug 2018

http://www.turnstone-cottage.co.uk/fog.html


Graham
Penzance

Graham Easterling wrote:

Perhaps that's what happened at Camborne - the fog was within
1000m but wasn't at the station - adjacent fog should have been
reported.

I think that's almost certainly the case. The Camborne site is around
2000m from an area of the north coast very prone to sea fog.

As for the 09:00 reporting time, whilst it many cases inland the fog
has gone by then, on the coast it's often brought in by the sea
breeze, so in summer the fog risk is higher later in the day.

There's an excellent photo of the onset of a north coast sea breeze
causing a fog roller here, just passing Lands End. (Moving right to
left) associated with the early afternoon onset of the north coast
sea breeze. 5th Aug 2018

http://www.turnstone-cottage.co.uk/fog.html


Graham
Penzance

At manned stations a human observer 'observes' the weather. At unmanned
stations the AWS 'measures' the weather. 'Observing' and 'measuring'
are not the same thing.

I recall, many moons ago at the start of my career, I was working at
the Met Office at Prestwick Airport. At that time we were the
collecting centre for all the Scottish SYNOPs and any queries regarding
them came through us. One day I got a call from some Herbert at
Bracknell querying a recent SYNOP from Lerwick. He said that you can't
have fog with a 25-knot wind. I duly called the observer at Lerwick and
passed on the query. His response was that 'if the guy at Bracknell
doesn't like my ob he can come and do the f***ing thing himself'. You
can't get that sort of response from an AWS :-)

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

One day I got a call from some Herbert at
Bracknell querying a recent SYNOP from Lerwick. He said that you can't
have fog with a 25-knot wind.
--
Norman Lynagh

He'd obviously never been near a west facing cliff top in a warm sector SW gale!

Graham
Penzance