Martin Rowley wrote:
"Keith (Southend)" wrote in message
news:ehfd11$dn1$1
Martin, I just bought a new Grass Minimum Thermometer from Fairmount
Weather Systems which is graduated in 0.5°c increments, however, you
can easily make a judgment of 0.1 - 0.2°c intervals. I was wondering
how your grass minimum was recorded as 9.3°c? Synops only report to
the nearest whole °c.

... SYNOP's only allow grass minima to be reported to nearest whole
degC, but that's simply a function of the code - saving some space: if
you remember, *all* temperatures in SYNOP's used to be reported to the
nearest whole degC (and before that, the nearest whole degF).

With a classic mercury-in-glass thermometer, it is perfectly possible to
read to the nearest degC: see the Observer's Handbook, page 111 (1969
ed.). If you haven't got access to that, let me know by email and I'll
send you a copy of the relevant page.

All the best,

Martin.



Thanks Martin,

I'm not this old, but I have a copy of the Observer's Handbook M.O.191
(1942) and page 25 states:
"(a) the range of ggraduation should be suitable,
(b) the scale of graduation should be sufficiently open to permit of
estimation to 0.1° F. without difficulty.
(c) the bulb should be of standard dimensions."

I'll e-mail you as I would be interested in whether the (1969) edition
has any changes :-)

Regards

--
Keith (Southend)
http://www.southendweather.net
e-mail: kreh at southendweather dot net