[CF-metadata] hydrosphere

[Jonathan Gregory]

Dear Philip

> FWIW, I think of 'hydrosphere' as including ground water, clouds, and ice.

Ah.

> Is that what is intended here?

No, it is not mean to include groundwater or clouds. Ice is included if it is
frozen river, lake or sea water. 

> Would 'water_bodies' work for ocean+sea+lakes+rivers ?

That's unfortunately not a phrase which would be obviously meaningful in
water_bodies_density, I think.

I fear this is a hopeless quest, which is why I suggested defining "sea" to
include lake and river in the context of CF standard names.

Best wishes

Jonathan