[CF-metadata] CMIP6 Sea Ice MIP: General variables

From: Jonathan Gregory <j.m.gregory>
Date: Wed, 20 Jul 2016 14:48:39 +0100

Dear Dirk

Thanks for your proposals. Here are comments on some of them. The others are
new and fit existing patterns, I think.

> 1. proportion_of_model_time_steps_with_sea_ice_fraction_above_threshold

I suggest it would be better to make this less model-specific by calling it
  fraction_of_time_with_with_sea_ice_area_fraction_above_threshold
where I have inserted "area" as well for consistency with the existing name
sea_ice_area_fraction.

> 2. sea_ice_mass_content [kg m-2]
> describes the total mass of sea ice divided by grid-cell area.

This is the same as the existing sea_ice_amount (the area by which it is
divided is described by cell_methods, as in my other posting).

> 5. sea_ice_melt_pond_thickness [m]
> the volume of water in meltponds divided by meltpond covered area

OK, with a similar cell_methods issue: I think by default this would be
a local thickness, but it could be described as an area-mean.

> 6. thickness_of_sea_ice_melt_pond_refrozen_ice [m]
> the volume of refrozen ice in meltponds divided by meltpond covered area

Is this ice floating on top of the meltpond?

> 7. ridged_sea_ice_thickness [m]
> total volume of ridged sea ice divided by area of ridges

Instead of a new standard name, could this be described by sea_ice_thickness
and "where" in cell_methods if we define a new area_type of ridged_sea_ice?

> 11. surface_snow_sublimation_flux [kg m-2 s-1]
> the rate of change of snow mass through sublimation and evaporation
> divided by grid-cell area

Unless you specifically want to *exclude* ice, this could use the existing
surface_snow_and_ice_sublimation_flux.

> 13. tendency_of_surface_snow_amount_due_to_ice_conversion [kg m-2 s-1]
> the rate of change of snow mass due to transformation of snow to sea ice
> divided by grid-cell area

I feel that due_to_ice_conversion is not specific enough because it doesn't
give the sense of the change. To be clear, would it be correct to say
  due_to_conversion_of_snow_to_sea_ice
?

> 15. sea_ice_basal_downwelling_shortwave_flux_in_sea_water [W m-2]
> the downwelling shortwave flux underneath sea ice (always positive)

I think that
  downwelling_shortwave_flux_in_sea_water_at_sea_ice_base
would be more natural because it's not really a property of the sea-ice.
The sea-ice base is a level.

> 16. sea_ice_basal_net_downward_sensible_heat_flux [W m-2]
> the net sensible heat flux under sea ice from the ocean

This has an existing name upward_sea_ice_basal_heat_flux.

> 17. sea_ice_surface_net_downward_conductive_heat_flux [W m-2]
> the net heat conduction flux at the ice surface
> 18. sea_ice_basal_net_downward_conductive_heat_flux [W m-2]
> the net heat conduction flux at the ice base

We have an existing name of downward_heat_flux_in_sea_ice for the conductive
flux within the ice. To be specific about the level, we could prefix surface_
for 17 and suffix basal_ for 18.

> 19. salt_flux_into_sea_water_from_sea_ice [kg m-2 s-1]
> Total flux of salt from water into sea ice divided by grid-cell area;
> salt flux is upward (negative) during ice growth when salt is embedded
> into the ice and downward (positive) during melt when salt from sea ice
> is again released to the ocean

This is like the existing name
  virtual_salt_flux_into_sea_water_due_to_sea_ice_thermodynamics
isn't it, except not virtual.

> 20. water_flux_into_sea_water_from_sea_ice [kg m-2 s-1]
> Total flux of fresh water from water into sea ice divided by grid-cell
> area; This flux is negative during ice growth (liquid water mass
> decreases, hence upward flux of freshwater), positive during ice melt
> (liquid water mass increases, hence downward flux of freshwater)

I think this is the same as the existing
  water_flux_into_sea_water_due_to_sea_ice_thermodynamics

> 21. surface_drag_coefficient_for_momentum_in_sea_water [1]
> Oceanic drag coefficient that is used to calculate the oceanic momentum
> drag on sea ice

Should that be surface_ (which means the top of the atmosphere) or perhaps
sea_ice_basal_?

> 22. sea_ice_specific_x_force_due_to_sea_surface_tilt [N m-2]
> 23. sea_ice_specific_y_force_due_to_sea_surface_tilt [N m-2]
> 24. sea_ice_specific_x_force_due_to_coriolis_term [N m-2]
> 25. sea_ice_spcecific_y_force_due_to_coriolis_term [N m-2]
> 26. sea_ice_specific_x_force_due_to_internal_forces [N m-2]
> 27. sea_ice_specific_y_force_due_to_internal_forces [N m-2]

In other N m-2 = Pa names, we use "stress" rather than "specific force" but
I suppose this is different because they are not fluxes of momentum, but
divergences of momentum i.e. force per unit mass. Is "specific force" a
usual term for this? Could we say "coriolis_effect" rather than "term",
which sounds more algorithmic than geophysical?

> 28. sea_ice_mass_transport_across_line [kg s-1]
> "net (sum of transport in all directions) sea ice mass transport through
> given passages, positive into the Arctic Ocean

This exists under the name sea_ice_transport_across_line.

Best wishes

Jonathan
Received on Wed Jul 20 2016 - 07:48:39 BST