Hi, All,

MetO installed a Campbell Stokes sunshine recorder at the Copley Site on 1st July.
The electronic R&D recorder is set at its most sensitive and will not go any lower, as that was the best setting under weak sun. As it is on the 10 metre anemometer pole it records an extra hour of sun from 04Z-05Z which the Campbell Stokes, on a screen stand, does not capture. The rest of the day has no shade for either instrument.
To my surprise, as I thought the electronic would be more sensitive, during partly cloudy conditions, the C/S records more sun than the electronic, so much so that the C/S is currently running upwards of 10% higher for the month so far.

I am sure MetO Quality Control will put me right if I am reading the trace incorrectly when they look at the cards and visit the site. I have read the Observer's Handbook time and again and am sure I'm doing it right. It does seem very subjective, however!

Anyway, the half-way figures for Copley for July 2015, up to 09Z 16th:
Mean max 19.7C Mean min 10.0C Mean 14.9C(+0.2C)
Rain 54.3mm(76%)
Wind WSW 7.4KT(-0.2KT)
Sun(E) 94.3hr(59%)
Sun(C/S) 102.5hr

This morning's ob 09Z-09Z Max 18.4C min 5.5C grass -0.1C rain nil sun 15th 10.6hr(8.9hr electronic)

Ken
Copley
Teesdale
http://www.kencook.magix.net/

On Thursday, 16 July 2015 12:52:43 UTC+1, Ken Cook wrote:
Hi, All,

MetO installed a Campbell Stokes sunshine recorder at the Copley Site on 1st July.
The electronic R&D recorder is set at its most sensitive and will not go any lower, as that was the best setting under weak sun. As it is on the 10 metre anemometer pole it records an extra hour of sun from 04Z-05Z which the Campbell Stokes, on a screen stand, does not capture. The rest of the day has no shade for either instrument.
To my surprise, as I thought the electronic would be more sensitive, during partly cloudy conditions, the C/S records more sun than the electronic, so much so that the C/S is currently running upwards of 10% higher for the month so far.

I am sure MetO Quality Control will put me right if I am reading the trace incorrectly when they look at the cards and visit the site. I have read the Observer's Handbook time and again and am sure I'm doing it right. It does seem very subjective, however!

Anyway, the half-way figures for Copley for July 2015, up to 09Z 16th:
Mean max 19.7C Mean min 10.0C Mean 14.9C(+0.2C)
Rain 54.3mm(76%)
Wind WSW 7.4KT(-0.2KT)
Sun(E) 94.3hr(59%)
Sun(C/S) 102.5hr

This morning's ob 09Z-09Z Max 18.4C min 5.5C grass -0.1C rain nil sun 15th 10.6hr(8.9hr electronic)

Ken
Copley
Teesdale
http://www.kencook.magix.net/
----------------------------------------------------------------------------
Hi Ken,
The Campbell Stokes can give an overburn of the card in partly sunny conditions.
Something to do with reflection from the cloud as I understand.

It is a bit of a can of worms comparing it with the electronic recorder in my experience.
Campbell Stokes is only meant to record bright sunshine. There is a threshold set on the electronic recorder (200 W per sq m ?). I seem to remember there were particular discrepancies early and late in the day, which led to different sunshine totals.

Len
Wembury, SW Devon

--------------------------------------------------------------------------

"Ken Cook" wrote in message
...
Hi, All,

MetO installed a Campbell Stokes sunshine recorder at the Copley Site on 1st
July.
The electronic R&D recorder is set at its most sensitive and will not go any
lower, as that was the best setting under weak sun. As it is on the 10 metre
anemometer pole it records an extra hour of sun from 04Z-05Z which the
Campbell Stokes, on a screen stand, does not capture. The rest of the day
has no shade for either instrument.
To my surprise, as I thought the electronic would be more sensitive, during
partly cloudy conditions, the C/S records more sun than the electronic, so
much so that the C/S is currently running upwards of 10% higher for the
month so far.

I am sure MetO Quality Control will put me right if I am reading the trace
incorrectly when they look at the cards and visit the site. I have read the
Observer's Handbook time and again and am sure I'm doing it right. It does
seem very subjective, however!

Anyway, the half-way figures for Copley for July 2015, up to 09Z 16th:
Mean max 19.7C Mean min 10.0C Mean 14.9C(+0.2C)
Rain 54.3mm(76%)
Wind WSW 7.4KT(-0.2KT)
Sun(E) 94.3hr(59%)
Sun(C/S) 102.5hr

This morning's ob 09Z-09Z Max 18.4C min 5.5C grass -0.1C rain nil sun 15th
10.6hr(8.9hr electronic)

Ken
Copley
Teesdale
http://www.kencook.magix.net/

Hello Ken. I too use the R&D recorder, and find in summer months it can
record quite a bit less than both the CS recorders at Reading Uni and
Maidenhead, and Stephen Burt's KZ recorder. The June figures I have so far
are Wokingham 166 hrs, Maidenhead 224 hrs and Stratfield Mortimer 225 hrs.
There was some local correspondence about the large variation across the
area in May, and I copy below Stephen Burt's thoughts on the matter. I am
unable to adjust the threshold on my R&D any higher as if I do it causes
spurious sun in certain overcast conditions. I have a spare sensor that I
could install in the near future if my figures fall even more relative to
the others. I would expect the R&D to be the more accurate when compared to
the CS in conditions where there is intermittent sun, the effect larger in
summer than winter.

Dear Bernard -



Yes indeed, I still use my R&D (Instromet) sensor - in fact, I have two, one
at 11 m AGL is my original unit (installed 2001), one at 6 m adjacent to my
K&Z CSD3 unit is one of their new units with an infrared filter photodiode
unit, which was installed in November 2013.



The raw totals for all three for May we



Instromet 1 (at 11 m AGL) 173.28 h

Instromet 2 (at 6 m AGL) 168.36 h

K&Z CSD3 (at 6 m AGL) 180.03 h



My 'climatological' totals are the K&Z reading adjusted slightly for horizon
obstructions early and late using the higher Instromet unit, which is almost
unobstructed; this was 186.71 h in May. (The K&Z unit tends to read higher
than the Instromets in summer, although personally I think the Instromet
threshold is closer to 'sunshine' as estimated by 'hard shadows', but even
so all three normally agree within 10% over a month - within the WMO spec.)



I would urge caution in adjusting the threshold point on the Instromet,
simply because it will introduce inhomogeneity into your records. Your
sunshine values have always been quite similar to mine, and I wouldn't do
anything hasty because of one month's disparity. May's sunshine was very
broken: the average spell length* was just 0.12 hours, compared with 0.97
hours in April, and I'm sure that contributed to the relative over-reading
of the university's C/S unit. Roger and I are looking into the over-reading
of the university's K&Z unit - I suspect the threshold is slightly
mis-calibrated, but short of sending it back to K&Z there's no way to get it
checked. I don't think we have a 'spare' unit in a cupboard to swap it out
with while that's done, even if I could persuade our finance officer to
countenance the expense .



I'd keep your eye on it for a couple of months at least before making any
changes. I think the discrepancies across our region last month are partly
real, but mostly instrumental/exposure/calibration differences.



Best regards

Stephen





* Using the logger, I count every time the 'sunshine = yes' voltage
threshold on the K&Z is exceeded during the day, logging down to a
resolution of 1 min. Total sunshine duration / total spells = average length
of sunshine 'spells', an interesting and extremely variable statistic




--
Bernard Burton

Wokingham Berkshire.

Weather data and satellite images at:
http://www.woksat.info/wwp.html



---
This email has been checked for viruses by Avast antivirus software.
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Len Wood wrote:

There is a threshold set on the electronic recorder (200 W per sq m ?).


Really? The highest I recorded in the whole of December 2014 was 160w/sqm
and I'm pretty sure the sun came out at some point.

I asked in this newsgroup a few months ago if it was possible to
mathematically determine if the sun was 'out' using the w/sqm along with
time of day and time of year but I didn't get far.

It must be possible but you certainly can't have a single threshold like
200w/sqm.



--
Brian Wakem
Lower Bourne, Farnham, Surrey
http://www.brianwakem.co.uk/weather

"Brian Wakem" wrote in message ...

Really? The highest I recorded in the whole of December 2014 was 160w/sqm
and I'm pretty sure the sun came out at some point.

I asked in this newsgroup a few months ago if it was possible to
mathematically determine if the sun was 'out' using the w/sqm along with
time of day and time of year but I didn't get far.
=======================================

From memory, I think you'll find that the threshold is actually 120W/sqm
_direct_ irradiance. I'm guessing you were probably measuring with a sensor
that records _total_ (ie direct plus indirect) irradiance, which is
obviously something rather different.

There are well-established algorithms for testing for bright sunshine (ie if
the sun is 'out'), which also need lat/long and TZ as inputs of course if
you are using a total irradiance sensor. It can only be an approximate or
rough estimate because of the limitations of using total irradiance, but it
works tolerably well. It's not possible to summarise these methods in a
short post here, but if still interested you might want to Google a bit
harder. To implement the algorithms in a script or program does require some
understanding of the trig functions involved.

John Dann
www.weatherstations.co.uk

On Thursday, 16 July 2015 12:52:43 UTC+1, Ken Cook wrote:
Hi, All,

MetO installed a Campbell Stokes sunshine recorder at the Copley Site on 1st July.

Thanks for the replies. I'll get used to it no doubt. MetO seem very keen and will obviously take the C/S as the "official" figure.
They say I will lose about 10% of the possible, most of this loss during early mornings in the summer. I'll let you know whether quality control agrees with my figures!
Ken

On 16/07/2015 17:19, JohnD wrote:
"Brian Wakem" wrote in message ...

Really? The highest I recorded in the whole of December 2014 was 160w/sqm
and I'm pretty sure the sun came out at some point.

I asked in this newsgroup a few months ago if it was possible to
mathematically determine if the sun was 'out' using the w/sqm along with
time of day and time of year but I didn't get far.
=======================================

From memory, I think you'll find that the threshold is actually
120W/sqm _direct_ irradiance. I'm guessing you were probably measuring
with a sensor that records _total_ (ie direct plus indirect) irradiance,
which is obviously something rather different.

There are well-established algorithms for testing for bright sunshine
(ie if the sun is 'out'), which also need lat/long and TZ as inputs of
course if you are using a total irradiance sensor. It can only be an
approximate or rough estimate because of the limitations of using total
irradiance, but it works tolerably well. It's not possible to summarise
these methods in a short post here, but if still interested you might
want to Google a bit harder. To implement the algorithms in a script or
program does require some understanding of the trig functions involved.

John Dann
www.weatherstations.co.uk


Ha what you need is Gorzynski Normal Incidence meter. I used one of
these at Kew Observatory when I was there in the late 60s (it was still
there in the early 70s at least). It was a solarimter pointed at the sun
and had a circular disc (maybe more) with holes in. You pointed it at
the sun and that's all it measured. It was driven by clockwork (had to
wind it every day). When you did you had to unwind the signal cable. It
didn't move with the sun's height from day to day, so each day you had
to ensure that it was pointed straight at the sun. Interesting when the
sun came out after a few days of cloud.

But then KO had lots of strange meteorological instruments never seen
anywhere else.

I have a photo of one but I've not yet scanned it. Googling for it got
mentions but no pics.

"Ken Cook" wrote in message
...
On Thursday, 16 July 2015 12:52:43 UTC+1, Ken Cook wrote:
Hi, All,

MetO installed a Campbell Stokes sunshine recorder at the Copley Site on
1st July.

Thanks for the replies. I'll get used to it no doubt. MetO seem very keen
and will obviously take the C/S as the "official" figure.
They say I will lose about 10% of the possible, most of this loss during
early mornings in the summer. I'll let you know whether quality control
agrees with my figures!
Ken

Lighted cigarette ends can be useful if you are a health resort, did I say
that ....... :-O

Will
--
http://www.lyneside.demon.co.uk/Hayt...antage_Pro.htm
Will Hand (Haytor, Devon, 1017 feet asl)
---------------------------------------------

lol!
Anyway you southern boys watch out. Teesdale the sunny one :-)
Ken
Costa Copley