[CF-metadata] Hoedk/Stockhause standard names

From: Pamment, JA <J.A.Pamment>
Date: Tue, 10 Jul 2007 14:17:35 +0100

Dear Heinke,

Thank you for your responses.

> >> snow_evaporation_amount ->
> >> lwe_thickness_of_surface_snow_sublimation_amount open question
> (surface)
> >>
> >> >> > >
> >> >> > > snow_evaporation_amount
> >> >> > > metre
> >> >> > > ERA40
> >>
> >> Alisons question:
> >>
> >> I am not entirely clear as to whether this is evaporation of snow
> >> lying on the surface, or of falling snow. Please could you
clarify?
> >> In either case "amount" is used in standard names to mean "mass per
> >> unit area" which would not be appropriate for units of metres. I
> >> would suggest using "depth" rather than "amount". Also, if the
snow
> >> is being converted directly to water vapour we should call it
> >> sublimation rather than evaporation.
> >>
> >> Sorry, but I have not got an answer, but it is in work. I think it
is
> >> snow lying on the surface. But I would like to check it.
> >>
> >>
> > OK, thank you, I will wait for clarification.
> >
> >
> Here Manuel Fuentes (ECMWF) answers:
> > 2) In the ECMWF standard table 128 the variable "044 ES Snow
> > evaporation of water" is unclear - does it refer only to lying snow
or
> > to falling snow as well?
> >
>
> I have asked the experts, and this is their reply:
>
> It refers to snow on the ground. So it is a flux from the surface into
> into the atmosphere through the conversion of snow into water vapour.
>
Ok, thank you for checking. I take this to mean that we are talking
about
both the conversion of snow directly into water vapour (sublimation) and
the
melting of snow and subsequent evaporation of the melt water. We do
need to
be clear about which processes are included before the name can be
finally
agreed.

We already have the name
surface_snow_melt_and_sublimation_heat_flux
and one possibility would be to define a similar name for water vapour:
surface_evaporation_of_melted_snow_and_snow_sublimation_water_vapor_flux
(unit: kg m-2 s-1).
The emphasis here is clearly on the flux of water vapour into the
atmosphere, rather than on how the snow depth is changing due to the
evaporation.

However, I note that in your original proposal the unit given is metres:
> snow_evaporation_amount
> metre
> ERA40
so I still think that a "thickness" name would be a more appropriate
option.
Therefore, a second possibility is:
lwe_thickness_of_surface_snow_sublimation_and_melted_snow_evaporation_am
ount
(unit: m)
This means the vertical extent of a layer of liquid water having the
same mass per unit area as the layer of snow which has been lost due to
sublimation and melting + evaporation.

Yet a third possibility would be:
thickness_of_surface_snow_sublimation_and_melted_snow_evaporation_amount
(unit: m).
This means the thickness of the layer of snow lost due to sublimation
and
melting + evaporation and depends on the density of the snow.

The choice of whether to use "thickness" or "lwe_thickness" depends, I
think, on the precise way in which the variable is calculated in the
ECMWF model. We could, of course, define both names but you would still
need to decide which one to use for ERA40 data. I will check with
Manuel to see if we can get a more precise description of what is done
in ERA40.

> > You have given these names question marks on the right-hand side. I
> think in fact that we are already agreed that the names are fine and
the
> only outstanding question is the definition of "where_ice". I would
> interpret "where_ice" to mean anywhere where there is either land or
sea
> ice - do you agree with that?
> >
> >
> >
> ====================================================
> surface_net_downward_shortwave_flux_where_ice
> where_ice means sea ice or lake ice
> ===================================================
> But I think we should wait for the cell-method discussion about the
> where condition.
> What do you think ?
>
Yes, you are quite right - thank you for reminding me! The use of
"where"
was, in fact, one of the subjects presented by Jonathan at the GO-ESSP
meeting last month. I will check with Jonathan as to whether he is
intending to make a new proposal about how we should describe subgrid
variation following on from that meeting. Jonathan did post a proposal
on
the mailing list at the end of last year, but I don't think it received
any discussion at the time and I'm not sure if it needs to be revised
following the discussion at GO-ESSP.
 
I will be updating the standard name table in a few days and I propose
to
include those of your names that we have already agreed.

Best wishes,
Alison

------
Alison Pamment Tel: +44 1235 778065
NCAS/British Atmospheric Data Centre Fax: +44 1235 446314
Rutherford Appleton Laboratory Email: J.A.Pamment at rl.ac.uk
Chilton, Didcot, OX11 0QX, U.K.
Received on Tue Jul 10 2007 - 07:17:35 BST