"Keith (Southend)" wrote in message
...
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.

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 :-)

When I first started observing officially, in the early-1970s, I was
bemused by my co-observers' - mostly elderly gentlemen - habit
of reporting temperatures ending in .5 or .0 rather more frequently
(in one case, much more frequently) than ought to have been the case.
I was green enough and brash enough on one night duty to make
histograms of each observer's decimal-point count, thinking that
I'd identified a form of incompetence or laziness. Now that I need
reading-glasses myself for checking thermometers, especially by
torchlight at night, I finally understand why.

Philip