On 6 Apr, 06:26, "Col" wrote:
wrote in message

...

* * * *Unfortunately, Dave, the sun will raise the screen temperature
above the true air temperature whether there are gaps in it or not. *I
notice this when the sun goes behind a tree in next door's garden.
You could rotate the screen so that the door faces north. *Bit of a
palaver.

..................

So what is the 'true air temperature', how can it be measured?
I thought that an official screen had to be placed in open ground
in direct sunlight.
--
Col

Bolton, Lancashire
160m asl

Yes, I thought the same. The air in the shade of a tree tends to be
particularly cool, when compared to say, the air in the shade of a
building.

We tend to get 2 temperature maximums here in settled conditions, due
to the fact we often get 2 sea breezes in opposite directions on the
same day. The 'normal' onshore SE sea breeze sets in late morning. The
northwest facing 'north' coast takes longer to warm due to it's
aspect, the sea breeze here typically sets in early afternoon. It then
gradually becomes the dominant sea breeze. The convergence zone, near
the north coast at noon, moves slowly south, until it reaches Mount's
Bay around 16:00 (BST). The is movement commonly shown by a line of
cloud. It's this, often sudden, onset of the north coast breeze which
is repoonsible for many of the north coast summer thunderstorms.
www.turnstone-cottage.co.uk/SrMerrynStorm.PDF

As a result, in Penzance,we often get a max about 11;30-12:00, then a
dip, then a max around 15:30-16:00 in the quiet period before the NW
breeze sets in.

Graham
Penzance