Gavino wrote:

"Norman" wrote in message
...
John Hall wrote:
On second thoughts my suggestion would probably still over-emphasise
snowfall in relation to temperature, as the number of days of snow lying
can be anywhere between zero and 60-70, whereas the limits on winter
mean temperature are probably between about zero and 6-7. So the range
of values of the former is about ten times that of the latter. To
compensate for that, a possible index might be L - 10*T. So a very mild
and non-snowy winter would have a value of about -60 or -70, and a very
cold and snowy one like 1962-3 would have a value of +60 or +70. An
average winter would be about 10 - 10*4 = -30. If you'd rather the
average index was close to zero you could use 30 + L - 10*T.

Sorry John, I can't agree with that. Using the temperature expressed in deg
C in this way is akin to saying that a day with a max of 4 deg C is twice
as warm as a day with a max of 2 deg C which, I think you would agree, is
nonsense. Using deg K is the only valid method.

I don't agree, Norman.
I think John's method is perfectly valid, as the 'index' (like a temperature
scale) has an arbitrary zero point which can be chosen at will and only
differences in its value (not ratios) are meaningful. A max of 4C compared to
a max of 2C will just subtract '2 degrees worth' of severity from the index,
ie 20 points on his scale.

And this will work exactly the same whether you use deg K or deg C - it just
changes the zero point of the index.

Subtracting (some multiple of) the temperature is much better than dividing,
since it makes the index linear in both L and T.


You're right, Gavino. I obviously didn't read John's post correctly. I thought
he was still suggesting dividing by the temperature but he is not. I agree that
in John's proposed method it doesn't matter whether deg C or deg K are used -
apologies John :-)

--
Norman Lynagh
Tideswell, Derbyshire
303m a.s.l.