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.

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I can't tell you how pleased I am to see people once again thinking
about the weather in an intersting way and coming up with some varied
and interesting ideas on UKSW. Having tried some similar things I
realise how difficult it is. I agree with Scott that there is more to a
severe winter than the superficial perceptions people have and also how
difficult it is to represent those perceptions mathematically.
Dave