[CF-metadata] CF-metadata Digest - cell method change...

From: Jonathan Gregory <j.m.gregory>
Date: Thu, 12 Jul 2007 08:56:54 +0100

Dear Martin

I agree with Karl and Seth. The concepts of a change over 3 h, and a rate of
change averaged over 3 h, have the same practical purpose but they are not
identical in principle. The difference in principle is that the former is
extensive in time and the latter intensive. It's the same as the distinction
between a precipitation amount (kg m-2), which is extensive in time, and a
precipitation flux (kg m-2 s-1), which is intensive. In practice I think it
is much clearer to use rates rather than changes, because amounts are not
at all useful unless you know the length of time involved. However for
precipitation, at least, both rates and changes are in use, so we have to
have clear ways to describe and distinguish them.

Cheers

Jonathan
Received on Thu Jul 12 2007 - 01:56:54 BST