On 8/8/11 3:40 PM, Steve Hankin wrote:
> [My gosh, two responses arrived as I typed this. A hot topic, clearly.]
yup -- remember that last thread?
> Myself, I am in the school of
> thought that says a "month" is not a valid unit of time, since it does
> not represent a fixed amount of time (January and February months being
> unequal quantities).
me too.
> This school says you should encode your CF files
> using a meaningful unit such as "DAYS since ...".
however, I don't agree with this, either. data like a monthly average is
more categorical than on a continuum -- as you questions suggests, you
do not have values that are the value on May 15th, for example. If it is
a "moving average", then it _may_ be appropriate to call it the 15th of
the month, but in that case, the value really would be different on the
16th or 14th.
I don't know if there is a CF-approved way to do it, but I would define
your variable with a categorical axis:
* don't call it "time"
* don't use units of "a_unit since a date-time"
The problem with doing that, (months vs. days apart) is that software
tends to interpret that as a real time continuum, and that's not what
this is.
>> Also, should I do anything differently if my data are climatological
>> monthly averages (say, over 30 years of data)?
even more so -- a 30 year average for January does not have a date-time
associated with it at all -- it would be a mistake to make it look like
it does.
-Chris
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov
Received on Mon Aug 08 2011 - 17:04:58 BST
