Hi Jonathan and Martin,
I agree, rainfall and snowfall are better because they are more
explicit. I guess precipitation by itself is already clear.
"onto" instead of "on" would also be less prone to misinterpretation as
would be using "surface_snow" in place of "snow".
As for the meaning, I interpreted it as you did in terms of the fraction
of falling mass deposited onto the snow-covered portion of the grid cell.
I think of snowfall "amount" and "rainfall" amount as answering the
question "how much snow (rain) did we get yesterday?". The answer is
usually expressed in terms of a depth measure (e.g., "cm"), not mass.
Interpreted in this way, it would be confusing to say
fraction_of_snowfall_amount_falling_onto_surface_snow
because it might suggest that this is the
"fraction_of_snowfall_depth_falling_onto_surface_snow, which isn't what we mean.
So, I would favor
fraction_of_precipitation/rainfall/snowfall_mass_falling_onto_surface_snow
best regards,
Karl
On 6/1/18 12:34 AM, Jonathan Gregory wrote:
Dear Martin and Karl
I'm not sure I have understood this. Writing out what Martin first said
at greater length, does it mean
mass of rainfall (in kg, meaning the area- and time-integral rainfall flux
in kg m-2 s-1) which falls onto the snow-covered portion of the gridbox in
a certain time-interval, divided by the mass of rainfall (in the same sense)
which falls onto the entire gridbox in the same time-interval?
and the same for "precipitation" and "snowfall" instead of "rainfall"?
If so, I have some suggestions regarding
fraction_of_precipitation_mass_falling_on_snow
fraction_of_rain_mass_falling_on_snow
fraction_of_snow_mass_falling_on_snow
First, I think we could use "rainfall_amount" and "snowfall_amount" as Martin
first said, because these are time-accumulations, aren't they? They are
actually the gridbox precipitation/rainfall/snowfall_amount multiplied by the
area fraction of the gridbox which is covered by snow. I think this would
be preferable because we currently don't have terms with "mass" for
precipitation. On the other hand, you could prefer "mass" if you write it as
I did above and regard it as a mass fraction. In that case I would advocate
"precipitation/rainfall/snowfall_mass" i.e. insert "fall". This
is because "snowmass" could be misunderstood to mean the mass of lying snow -
a sense in which the word is often used. Including "fall" would make these
mass terms look like the existing amount, content, flux and rate terms. However
I still prefer "amount".
Second, I think "onto", as Martin said, is better than "on". It makes it
clearer (again) that it's been added.
Third, instead of onto_snow I would say onto_surface_snow, because we have
consistently used the phrase surface_snow to mean snow lying on the ground,
to be absolutely clear we don't mean snowfall. Since we have to talk about
both snowfall and lying snow in one standard name here, clarity is useful
about which is which. If it means snow and ice, not just snow, then we can say
surface_snow_and_ice, which is a phrase already used.
Thus I end up with
fraction_of_precipitation/rainfall/snowfall_amount_falling_onto_surface_snow
and if that's still not quite transparent to parse, we could consider saying
which_falls instead of falling. Neither is yet used in standard names.
Best wishes
Jonathan
----- Forwarded message from Martin Juckes - UKRI STFC
<martin.juc...@stfc.ac.uk> -----
Date: Fri, 1 Jun 2018 06:42:45 +0000
From: Martin Juckes - UKRI STFC <martin.juc...@stfc.ac.uk>
To: Karl Taylor <taylo...@llnl.gov>, "cf-metadata@cgd.ucar.edu"
<cf-metadata@cgd.ucar.edu>
Subject: Re: [CF-metadata] Precipitation fractions for LS3MIP
Hi Karl,
Thanks, that looks better. I was trying to stick close to existing patterns,
but the outcome was a bit contrived and, I agree, not very satisfactory.
Sorry about the confusion, the two terms we need are:
fraction_of_rain_mass_falling_on_snow
fraction_of_snow_mass_falling_on_snow
However, I need to check with LS3MIP whether they intend "snowfall" to include snow and
ice, as for the CMIP5 variable "prsn",
regards,
Martin
________________________________
From: CF-metadata <cf-metadata-boun...@cgd.ucar.edu> on behalf of Karl Taylor
<taylo...@llnl.gov>
Sent: 31 May 2018 19:11
To: cf-metadata@cgd.ucar.edu
Subject: Re: [CF-metadata] Precipitation fractions for LS3MIP
Hi Martin,
For CMIP6, I think we define precipitation = rainfall + snowfall .
So do you want to collect "precipitation amount" or "rainfall amount"
(in addition to "snowfall amount")? You first mention "rainfall" below,
but later propose a name for "precipitation".
I also think it is a bit confusing that in this name "amount" refers to
the amount accumulated over some time-period (e.g., a day or a month),
rather than the total "content" that exists at a given point in time.
I might suggest as alternatives:
fraction_of_precipitation_mass_falling_on_snow
fraction_of_rain_mass_falling_on_snow
fraction_of_snow_mass_falling_on_snow
best regards,
Karl
On 5/31/18 9:56 AM, Martin Juckes - UKRI STFC wrote:
Hello All,
There are two LS3MIP variables for fractions of precipitation onto snow:
fraction of rainfall on snow and fraction of snowfall on snow. In both cases
the fraction is calculated as the mass of precipitation falling on snow divided
by the total mass of precipitation in the grid cell.
Since we are dealing with mass, the term should start from precipitation_amount
and snowfall_amount.
We have terms like lwe_thickness_of_precipitation_amount to describe properties
of the precipitation amount, and we have precipitation_flux_onto_canopy do
describe a flux onto a particular surface, so I propose:
fraction_of_precipitation_amount_onto_snow and
fraction_of_snowfall_amount_onto_snow, both with units '1',
regards,
Martin
_______________________________________________
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
_______________________________________________
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
_______________________________________________
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
----- End forwarded message -----
_______________________________________________
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
_______________________________________________
CF-metadata mailing list
CF-metadata@cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
