[CF-metadata] Cell methods - depth mean

From: Jonathan Gregory <j.m.gregory>
Date: Mon, 3 Aug 2009 09:46:52 +0100

Dear Jenny

> In my data I have lat, long, time and the depth-mean east,north-velocities. I guess I need to attach the cell_methods attribute to the velocity variable. e.g. cell_methods="ocean_sigma_coordinate:mean"

Yes, that's right, except there should be a space after ":".

> Do I then create an ocean_sigma_coordinate variable (with correct dimensions and values) and attach a bounds attribute?
> e.g. ocean_sigma_coordinate : bounds = " sigma_coordinate_bnds"

Yes. But since this is a depth-mean, the coordinate variable will have size
one, not 32 or however many levels you have. This is not the usual vertical
coordinate. It's a "collapsed" vertical coordinate included specially in order
to indicate the limits of the vertical mean. As an alternative to a size-one
dimension and coordinate variable, CF allows a scalar coordinate variable
named by the coordinates attribute.

The value of the size-one or scalar coord variable is a bit arbitrary. It is
a representative sigma value. The important information is the bounds. They
should be the sigma values of the top and bottom of the vertical mean.

Cheers

Jonathan
Received on Mon Aug 03 2009 - 02:46:52 BST