[CF-metadata] Logarithmic scaling and CF-Convention

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 27 Sep 2010 08:33:28 +0100

Dear John and Steve

Any conversion to logarithmic units requires a reference value, because the
quantity computed is log(value/reference). The base of the logarithm (10 or e)
also has to be specified. If this conversion is used for packing, those two
numbers could be recorded as attributes and the transformation could be
reversed. If the conversion is done to produce a new geophysical quantity, the
reference level and logarithm base are part of the definition of the quantity
and could be recorded in the standard_name definition. For instance, "acoustic
intensity level" in decibels is the logarithm of the "acoustic intensity" in
W m-2, with a reference of 1e-12 W m-2 according to wikipedia.

Cheers

Jonathan
Received on Mon Sep 27 2010 - 01:33:28 BST