"Wijke" wrote in message
...

"Martin Rowley" schreef in bericht
...

... can't read the Dutch I'm afraid, at least to pick out the answer
to
my question: is this sunshine record with respect to the *same*
recording instrument?


That's a rightly marginal note, Martin. The KNMI (Dutch Met-Office)
used the
Campbell-Stokes untill 1992; from that year on the institute works
with the
pyranometer. And still has the Campbell-Stokes for backing-up and
comparing
the data.
I have tried to find something about the formula which is used to
calculate
sun-hours out of radiation; the estimation-errors etc. Unfortunately,
despite the perfect information of the KNMI-site, I haven't found an
answer
yet. But will keep on searching ;-).


.... many thanks for that: would be interesting to find out how they
relate the CS to modern records - I know the Met Office are (have)
undertaken the same comparison. Using the standard WMO definition for
'bright sunshine' ( direct irradiance 120 W/m^2), it's study suggests
an rough 10% *reduction* (for the units used by the UKMO) wrt
Cambell-Stokes. I think most would agree that the C-S always did tend
(either through it's design or through difficulty of estimating
intermittent sunshine), to *over-estimate* sunshine amounts. This would
make the De Bilt record set this year even more remarkable, and in any
case, it confirms what we over this side of the North Sea have been
experiencing - a remarkable year for sunshine.

If you can get hold of it, it would be interesting to see what the C-S
figures are for this year, against the pyranometer, and also which
marque of the latter is being used.

Martin.

Martin.