[CF-metadata] CMIP5 cryosphere standard names

[Jonathan Gregory]

Dear Alison and Siobhan

Sorry for late comments on the cryosphere names.

I commented this week on "shear". I was wrong to suggest that sea ice shear
is like wind speed shear, because the latter is the vertical derivative of
a horizontal speed, whereas sea ice shear is (I think) a horizontal derivative
of a horizontal velocity or speed. I wonder what the quantity required is
symbolically? Is it du/dy or dv/dx? These, I think, are two distinct components
of a tensor, but I might be wrong.

> Perhaps the name should be
> tendency_of_fractional_growth_in_ice_volume_due_to_ridging or
> tendency_of_fractional_growth_in_ice_area_due_to_ridging.
> 
> I think we need to call the quantity a tendency because that is the term we normally use in standard names to mean the time rate of change.

I agree that it should be a tendency, and I suspect the quantity could be
called
  tendency_of_sea_ice_area_fraction_due_to_ridging
which is a contribution to (or perhaps identical with) the existing quantity
  tendency_of_sea_ice_area_fraction_due_to_dynamics

Best wishes

Jonathan