Dear Karl, Jonathan,
thank you, these are very relevant comments. I'm afraid I still can't find
Jonathan's comments from Tuesday --- the email doesn't appear with the other
mails of the thread in the list archives where I usually go to trace exchanges
back.
Jonathan makes a good point about the usage of "assuming": I introduced the
term into the thread, copying it from the existing help text for "soil_albedo",
and Alison referred to terms which use "assuming" in the standard name. As
Jonathan says, there is a very specific interpretation when "assuming" is used
in a standard name, so perhaps the soil_albedo help text should be modified to
avoid confusion. "soil_albedo" could, I think, be replaced by surface albedo
with area type bare_soil.
Responding to Karl's comments:
(1) I had missed the fact that the CMIP5 evaporation variable, evs, adopted the
broadest possible interpretation of the term. I agree that we should preserve
this interpretation and that the proposed new variable for evapotranspiration
is redundant. The fact that evs includes sublimation and transpiration is made
clear in the CMIP5 variable tables, but the standard name
water_evaporation_flux does not make any reference to the precise meaning of
evaporation. The AMS glossary says that "Evaporation is usually restricted in
use to the change of water from liquid to gas": this does not rule out the
possibility of using it in the broader sense, but it does suggest that there is
liable to be confusion if we use the word without further clarification. I
suggest introducing water_evapotranspiration_flux or
water_total_evaporation_flux and demoting water_evaporation_flux to an alias,
and also adding some explanatory text "Evapotranspiration/Total evaporation
refers to all water vapor fluxes
from the surface: liquid evaporation, sublimation and transpiration".
(2)
water_evaporation_flux_from_canopy_due_to_interception (kg m-2 s-1)
This may be obscure, and you are right to raise concerns about the precise
meaning of "canopy" as opposed to vegetation. There are a number of terms
related to water held on the "canopy". My understanding is that the terminology
comes from analysis of precipitation which lands on trees and is held away from
the surface. The models are beginning to differentiate between water which
falls directly on the surface and water held in the tree canopy.
We have an existing standard name canopy_height with the descriptive text:
'"Canopy" means the plant or vegetation canopy', and this name is used with a
CMIP6 variable for vegetation height and also for a specific variable for
vegetation height in natural grasslands (with the area type natural_grasses).
To my mind this usage (i.e. referring to the grass "canopy"), but it follows
the CMIP5 usage in variables such as prveg (Precipitation onto Canopy:
precipitation_flux_onto_canopy). It is also consistent with AMS, which
considers canopy to be "The vegetative covering over a surface", but also
references an alternative usage as the upper portion of the vegetation.
There are 11 CF standard names referring to the canopy, including
water_evaporation_flux_from_canopy. Following the discussion of
"water_evaporation_flux", the term "water_evaporation_flux_from_canopy" should
include transpiration as well as evaporation/sublimation from any water sitting
on the vegetation. The water sitting on the vegetation is referred to as
intercepted, and it is the evaporation/sublimation of this intercepted water
that is of interest here. LS3MIP will also be using the CMIP5 variable "ec"
which gives the transpiration flux. There is an existing term
canopy_water_amount to refer to this intercepted water, so perhaps it would be
better to say: water_evaporation_flux_from_canopy_water.
For the term canopy_water_amount, I think there is a real distinction between
canopy and vegetation: canopy is referring to the above ground portion of the
vegetation. The descriptive text could be clarified, but I think there is a
case for retaining the term.
(3) These are good points. I am also unfamiliar with the history of the term
temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_sea_water --- the
term we want here appears to be a close relative of that term, but I'm happy to
consider other formulation.
Because this is a heat flux across a surface I would prefer the form
"heat_flux_into_..." rather than "tendency_of_..._temperature_..._due_to_...",
because the boundary flux is not a term in a temperature tendency equation.
I have responded to comments from Alison on the best way to refer to the body
of snow and ice on land which is the recipient of the heat here -- my last
suggestion was "snow_and_ice_on_land", but that discussion is still open. Here,
we could use "heat_flux_into_snow_and_ice_on_land_due_to_rainfall".
(4) On reflection it may be clearer to say
surface_upward_latent_heat_flux_due_to_sublimation, where it is clear that
sublimation is a process and latent heat flux is a standard term.
regards,
Martin
________________________________
From: Karl Taylor <taylo...@llnl.gov>
Sent: 08 June 2018 17:24
To: Pamment, Alison (STFC,RAL,RALSP); Juckes, Martin (STFC,RAL,RALSP);
cf-metadata@cgd.ucar.edu
Subject: Re: [CF-metadata] Final 17 terms for CMIP6 LS3MIP.
Dear Alison, Martin, and Jonathan,
I just spent the last hour going over Alison's email and composed the following
comments before seeing Martin's response and not being aware of Jonathan's
comments on Tuesday. I think most of my comments are still relevant.
best regards,
Karl
Hi Alison and Martin,
After a quick look through these very thorough notes, I noticed:
1) "evaporation": In CMIP5 and in general up until now
a) "water_evaporation_flux" has included "transpiration" and
included water_sublimation_flux from all parts of the surface (soil and
vegetation).
b) "water_sublimation_flux" was restricted to water in solid
form on the surface (or surface vegetation) that passed into the gaseous phase
and entered the atmosphere.
c) we had no name for the "liquid-only" portion of
water_evaporation_flux
d) we had no name for the "transpiration-only" portion of
water_evaporation_flux.
I think we want to preserve these traditional definitions of
water_evaporation_flux and water_sublimation_flux when defining components of
them (e.g., portions originating from different parts of the surface and
vegetation, or restricted to certain surface water phases)
The main thing is that the water_evaporation_flux should be *all* the water
vapor leaving the surface (and surface vegetatioin) and entering the atmosphere
and water_sublimation_flux should be *all* the water vapor directly entering
the atmosphere from solid water on the surface.
If you want to introduce "evapotranspiration_flux", you would have to make
"water_evaporation_flux" an alias. It would be o.k. to define
"transpiration_flux" as a new name identifying the portion of
"water_evaporation" (i.e., "evapotranspiration") that is due to transpiration.
I think it would be a mistake to change the meaning of water_evaporation_flux
so that it excludes the portion due to transpiration. water_evaporation_flux
has been in use too long with the original meaning. "evapotranspiration" is
*not* a new concept in CF, it is a suggested new name for "evaporation". My
vote would be *not* to replace "evaporation" with "evapotranspiration"; the
atmosphere doesn't care that a portion of the evaporating water traveled
through the plant roots and exited through stomata in the leaves; it still ends
up in the atmosphere as vapor.
2) water_evaporation_flux_from_canopy_due_to_interception (kg m-2 s-1)
a) This seems quite obscure. "interception of what?" [snow
fall, yes?] Would water_evaporation_flux_from_canopy_snow work?
b) How else does snow accumulate on the canopy except by
falling as snow?
c) It appears that "evaporation" here must surely include
sublimation (as discussed in 1 above), which I think is good.
d) Is there a precise definition of canopy? How does it differ
from "vegetation"? A definition I found says "The canopy refers to the highest
layer of vegetation in a forest or woodland, made up of the crowns of its
tallest trees." I would be surprised if modelers are using the term in this
sense. If "canopy" is restricted to "trees" (or tallest trees), how are they
defined since some shrubs seem to have similar characteristics as trees. Why
would modelers want to isolate water evaporation from the canopy, rather than
considering water evaporation from all the vegetation? If "canopy" includes
all vegetation that "hides" the surface soil from above, wouldn't all plants do
that? If so, why not just say "vegetation" (meaning surface vegetation) and
avoid use of "canopy" in standard names.
e) In general the use of "canopy", I think, should be avoided
unless a precise definition can be provided and either models or measurements
actually keep track of what goes on there specifically. If "canopy" means
"surface vegetation", I think the term "vegetation" would be much less
misleading than the term "canopy".
3) I must have missed the discussion about this, but does
temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_sea_water
make sense? Our use of flux as a short-hand for "flux density" (as formally
used in physics) wouldn't seem to apply to "temperature", which is a property
of a material not something that can flow from one place to another. Does it
mean
"heat_flux_into_sea_water_due_to_rainfall_added_at_a_different_temperature"?
Or is it the "tendancy_of_sea_water_temperature_due_to_rainfall"? Or something
else?
4) I've never seen the term "sublimation heat flux" used, although I guess its
meaning is clear enough. Does anyone know of a different term meaning "heat
flux from the surface to the atmosphere due to sublimation of surface ice,
frost, and snow?
Thanks for all the great progress.
Best regards,
Karl
On 6/8/18 7:21 AM, Alison Pamment - UKRI STFC wrote:
Dear Martin,
Many thanks for making these proposals. I have comments and questions about
some of them. In particular, these proposals have made me think that we can
make better use of area types than we currently do for surface properties and
fluxes such as albedo (1.2), water evaporation (2.2) and snowpack heat flux
(3.1) - I think we should take a common approach to these.
I have accepted a few of the names and there are quite a number more that are
close to acceptance. As with the change_over_time names we need to be clear
which areas are included and excluded for all names and also which phases of
water are included. Please have a look at my comments and let me know what you
think.
Albedo [2]
We already have names such as "soil_albedo" (Soil albedo is the albedo of the
soil surface assuming no snow). Two new terms are requested, for canopy and snow
1.1 albc Canopy Albedo
canopy_albedo (1)
"Canopy" means the plant or vegetation canopy. Albedo is the ratio of outgoing
to incoming shortwave irradiance.
The name and units are fine. Does the canopy albedo assume no snow, or does it
include snow covered areas of the canopy?
This name is still under discussion. Please see also my related comments on 1.2.
1.2 albsn Snow and Ice Albedo [1]
Albedo of snow and ice covered surface.
snow_and_ice_albedo
Snow and ice albedo.
-- OR --
This could be handled with existing name surface_albedo and a new area type
"snow_or_ice". [Note that "landice" appears to exclude ice on lakes, which may
be a significant component of this albedo]
I'm beginning to think that we should have just one surface_albedo name which
would have several aliases (surface_albedo_assuming_deep_snow,
surface_albedo_assuming_no_snow, sea_ice_albedo) and add some more area types.
For your proposed quantity we'd need an area type of something like
land_snow_or_ice as you suggest; we could add deep_snow and no_snow, and
sea_ice already exists. This would be similar to the way in which we deprecated
several surface_temperature_where_X names and made them all aliases of
surface_temperature.
The surface_temperature definition says 'The surface called "surface" means the
lower boundary of the atmosphere. The surface temperature is the temperature at
the interface, not the bulk temperature of the medium above or below. Unless
indicated in the cell_methods attribute, a quantity is assumed to apply to the
whole area of each horizontal grid box. Previously, the qualifier where_type
was used to specify that the quantity applies only to the part of the grid box
of the named type. Names containing the where_type qualifier are deprecated and
newly created data should use the cell_methods attribute to indicate the
horizontal area to which the quantity applies.' If we take a similar approach
with the albedo names we should of course add the same recommendation to use
cell_methods to indicate the horizontal area. We would then be able to have the
albedo of any surface that is described in the area_type table without the need
to add further standard names. Do others think that would
be a useful step?
If we do go down the area_type route, I think we'd still need canopy_albedo as
a separate name because it's clearly not the same as the surface, but that name
could also optionally be combined with an area_type of no_snow if only the
albedo of snow free canopy where required.
Regardless of whether we decide to introduce a new standard name or a new area
type for the proposed quantity, we need a clear definition of which ice/snow
areas are included and excluded. I wonder if excluding lake_ice from our
definition of land_ice is a deliberate omission or an oversight? Can we check
this point with the ISMIP6 group? Even if lake_ice is not included in land_ice,
we do have an existing area_type lake_ice_or_sea_ice and we could introduce
lake_ice as a distinct area_type in its own right. I think we'd also need a
definition for land_snow, presumably something like ' "Land snow' means any
snow lying on the land surface, land ice or lake ice.'
If we use surface_albedo, then the area type for this quantity would need to be
land_ice_and_lake_ice_or_land_snow or land_ice_or_land_snow, depending on
whether lake_ice should be included in land_ice. If we introduce a new standard
name the information would have to go in there:
surface_albedo_assuming_land_ice_and_lake_ice_or_land_snow. Both approaches
lead to quite a long string for the surface type, but I think that's the only
way to be clear about the quantity that is being represented. We've used
similar long strings for C4MIP names such as
surface_upward_mass_flux_of_nitrous_oxide_expressed_as_nitrogen_out_of_vegetation_and_litter_and_soil.
This name is still under discussion.
2. Evaporation and transpiration fluxes [3] Variations on the theme of the
existing water_evaporation_flux term.
2.1 ec Interception evaporation [kg m-2 s-1]
water_evaporation_flux_from_canopy_due_to_intersection
"Canopy interception is the precipitation, including snow, that is intercepted
by the canopy of a tree and then evaporates from the leaves",
expanding on the existing name water_evaporation_flux_from_canopy
I assume there's a typo in the proposed name and it should say 'interception'.
Thank you for providing a definition for interception. Adding text from our
usual definitions I think we would end up with:
water_evaporation_flux_from_canopy_due_to_interception (kg m-2 s-1)
' "Water" means water in all phases. Evaporation is the conversion of liquid or
solid into vapor. (The conversion of solid alone into vapor is called
"sublimation".) In accordance with common usage in geophysical disciplines,
"flux" implies per unit area, called "flux density" in physics. The
specification of a physical process by the phrase "due_to_" process means that
the quantity named is a single term in a sum of terms which together compose
the general quantity named by omitting the phrase. "Canopy" means the plant or
vegetation canopy. "Canopy interception" is the precipitation, including snow,
that is intercepted by the canopy of a tree and then evaporates from the
leaves.'
Okay?
2.2 eow Open Water Evaporation [kg m-2 s-1]
A new term "water_evaporation_flux_from_open_water" would work here, but it
might make more sense to define an area type for open water
and use the existing standard name "water_evaporation_flux".
I agree that using the existing name water_evaporation_flux is a good choice,
although perhaps we should make that one into an alias of
water_evaporation_flux_from_surface which is a more accurate representation of
the quantity. We could certainly introduce a new area_type, but we'd need a
definition of 'open_water'. Does it mean 'ice_free_water'? We already have
ice_free_land and ice_free_sea. Does the open water in this case include the
sea or does it mean only land based water? Does it include rivers, lakes, etc.?
This name is still under discussion.
2.3 et Total Evapotranspiration [kg m-2 s-1]
"Evapotranspiration" is a new concept to the CF standard names, but appears to
be clearly defined.
evapotranspiration_flux (kg m-2 s-1)
"Evapotranspiration refers to the flux of water into the atmosphere from a
combination of transpiration by plants and evaporation from soil and
other land surfaces."
The name and units are fine. Thank you for providing a definition for
evapotranspiration. I think the full definition should read as follows:
' "Evapotranspiration" means the flux of water into the atmosphere from a
combination of transpiration by plants and evaporation from soil and other land
surfaces. Water means water in all phases. Evaporation is the conversion of
liquid or solid into vapor. (The conversion of solid alone into vapor is called
"sublimation"). Transpiration is the process by which water is carried from the
roots of plants and evaporates from the stomata. In accordance with common
usage in geophysical disciplines, "flux" implies per unit area, called "flux
density" in physics.'
Okay?
One question: does 'other land surfaces' specifically mean dry land, i.e. does
it exclude the open water of proposal 2.2?
This name is still under discussion.
3. Heat fluxes [2]
3.1 hfrs Heat transferred to snowpack by rainfall [W m-2]
A variation of
"temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_sea_water".
temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_snow_and_ice (W
m-2)
The name itself does follow existing patterns and the units are correct for a
heat flux. The existing
temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_sea_water name is
defined as follows:
'The quantity with standard name
temperature_flux_due_to_rainfall_expressed_as_heat_flux_into_sea_water is the
heat energy carried by rainfall entering the sea at the sea surface. It is
calculated relative to the heat that would be carried by rainfall entering the
sea at zero degrees Celsius. It is calculated as the product QrainCpTrain,
where Qrain is the mass flux of rainfall entering the sea (kg m-2 s-1), Cp is
the specific heat capacity of water and Train is the temperature in degrees
Celsius of the rain water entering the sea surface. In accordance with common
usage in geophysical disciplines, "flux" implies per unit area, called "flux
density" in physics. The specification of a physical process by the phrase
due_to_process means that the quantity named is a single term in a sum of terms
which together compose the general quantity named by omitting the phrase.'
Assuming that the proposed name would be defined similarly, it seems to me that
this is another case where we could use area types. The energy being carried by
the rainfall is essentially a surface flux - it depends on where the rain
originated and the properties of the air it has fallen through, rather than the
type of surface it is falling onto. I suggest we could make the existing name
into an alias of temperature_flux_due_to_rainfall_expressed_as_heat_flux. We
could then use this for both the original and proposed quantities if an
appropriate area type is supplied. We already have an area type of sea. Is the
proposed quantity like the albedo in proposal 1.2, i.e. does it mean
land_ice_and_lake_ice_or_land_snow?
This name is still under discussion.
3.2 hfsbl Energy of sublimation [W m-2]
Variation of: surface_upward_latent_heat_flux The definitions of latent heat
flux state that the latent heat flux includes sublimation heat flux, so it
makes sense to use the same pattern:
surface_upward_sublimation_heat_flux (W m-2)
The name and units are fine and the definition can be constructed from existing
text:
'The surface called "surface" means the lower boundary of the atmosphere.
"Upward" indicates a vector component which is positive when directed upward
(negative downward). Sublimation is the conversion of solid into vapor. In
accordance with common usage in geophysical disciplines, "flux" implies per
unit area, called "flux density" in physics.'
This name is accepted for publication in the standard name table and will be
added in the June update.
4. Nudging increments [2]
There are no terms referring to "nudging increments" in the CF convention, but
there are a number referring to "flux correction". The following help text is
proposed for nudging increments: "A nudging increment refers to an amount >
added to parts of the model system. nudging_increment_in_X refers to an
increment in quantity X over a time period which should be defined in the
bounds of the time coordinate." These should be encoded with cell_methods
"time: > sum" and a bounds variable to give the time over which nudging is
summed. The convention requires that, with this construction, the time periods
should be contiguous.
4.1 nudgincsm Nudging Increment of Water in Soil Moisture [kg m-2]
nudging_increment_in_mass_content_of_water_in_soil
Thank you for providing a definition for 'nudging increment'. I think this is
very much modelling jargon, although so is 'flux correction' I suppose. I can't
think of a better phrase, so don't have any real objection to including this
name as it is. The rest of the definition can be constructed from existing text:
'A "nudging increment" refers to an amount added to parts of a model system.
The phrase "nudging_increment_in_X" refers to an increment in quantity X over a
time period which should be defined in the bounds of the time coordinate.
"Content" indicates a quantity per unit area. "Water" means water in all
phases. The mass content of water in soil refers to the vertical integral from
the surface down to the bottom of the soil model. The "soil content" of a
quantity refers to the vertical integral from the surface down to the bottom of
the soil model. For the content between specified levels in the soil, standard
names including "content_of_soil_layer" are used.'
This name is accepted for publication in the standard name table and will be
added in the June update.
4.2 nudgincswe Nudging Increment of Water in Snow [kg m-2]
nudging_increment_in_surface_snow_and_ice_amount
The definition would be as follows:
'A "nudging increment" refers to an amount added to parts of a model system.
The phrase "nudging_increment_in_X" refers to an increment in quantity X over a
time period which should be defined in the bounds of the time coordinate. The
surface called "surface" means the lower boundary of the atmosphere. "Amount"
means mass per unit area.'
This seems okay, but I'm wondering if once again this quantity refers to
land_ice_and_lake_ice_or_land_snow as in proposals 1.2 and 3.1? If so, then we
should probably add something to the definition advising on the use of an area
type to describe exactly which areas are affected.
This name is still under discussion.
5. River in- and out-flow [2]
water_volume_transport_in_river_channel and
water_volume_transport_into_sea_water_from_rivers exist. The new variables
represent cell averages of river fluxes directed inwards and outwards
respectively.
5.1 rivi River Inflow Water flux from upstream [m3 s-1]
river_water_volume_transport_into_cell
'"Cell" refers to a model grid-cell. "River water" refers to the water (liquid
and solid) in the fluvial system (stream and floodplain).'
I think the suggested name and units look good. I suggest that we add some
advice about grid cell bounds to the definition (similar to ice mass and ice
area names).
' "Cell" refers to a model grid-cell. The extent of an individual grid cell is
defined by the horizontal coordinates and any associated coordinate bounds or
by a string valued auxiliary coordinate variable with a standard name of
"region". "Water" means water in all phases. "River" refers to water in the
fluvial system (stream and floodplain).'
Is it correct to say that this one includes "water in all phases", i.e. would
it include ice floating on a river? (This question also applies to proposal 1.3
change_over_time_in_river_water_amount in the thread "Standard names for
LS3MIP: 8 temporal changes + 1 feature depth".
This name is still under discussion.
5.2 rivo River Discharge [m3 s-1]
river_water_volume_transport_out_of_cell
As with proposal 5.1 the name and units look good and I suggest adding advice
about cell bounds to the definition:
' "Cell" refers to a model grid-cell. The extent of an individual grid cell is
defined by the horizontal coordinates and any associated coordinate bounds or
by a string valued auxiliary coordinate variable with a standard name of
"region". "Water" means water in all phases. "River" refers to water in the
fluvial system (stream and floodplain).'
Again, does this one include ice floating on a river?
This name is still under discussion.
6. Roots [1]
6.1 rzwc Root zone soil moisture [kg m-2]
This is a variation on mass_content_of_water_in_soil_layer, but with a layer
defined by the presence of roots rather than a coordinate range (cf.
"stratosphere" in atmosphere).
mass_content_of_water_in_root_zone
"The root zone refers to the soil which surrounds the roots of vegetation."
I think it would be helpful to include 'soil' in the name. We have an existing
name root_depth defined as 'Depth is the vertical distance below the surface.
The root depth is maximum depth of soil reached by plant roots, from which they
can extract moisture.' I suggest we call the proposed quantity
mass_content_of_water_in_soil_layer_defined_by_root_depth. This is a bit like
existing ocean_mixed_layer names, e.g.,
ocean_mixed_layer_thickness_defined_by_temperature. The ocean name definitions
refer to a coordinate variable whose value contains the temperature, etc., that
actually determine the layer thickness. We could do something similar here:
' "Content" indicates a quantity per unit area. The content of a soil layer is
the vertical integral of the specified quantity within the layer. The quantity
with standard name mass_content_of_water_in_soil_layer_defined_by_root_depth is
the vertical integral between the surface and the depth to which plant roots
penetrate. A coordinate variable or scalar coordinate variable with standard
name root_depth can be used to specify the extent of the layer. "Water" means
water in all phases.'
What do you think?
7. Water fluxes [5]
7.1 qgwr Groundwater recharge from soil layer [kg m-1 s-1]
There are no usage of "groundwater" in existing CF terms, the following has
been suggested in connection with the LS3MIP term dgw:
"Groundwater is the water present beneath Earth's surface in soil pore spaces
and in the fractures > of rock formations."
water_flux_from_soil_to_groundwater
I think there's a typo in the suggested units and it should say kg m-2 s-1. I
assume that this quantity must refer to the transfer of liquid water - frozen
soil moisture would have to melt before it could permeate to lower levels,
wouldn't it? Hence I think this name should be
liquid_water_mass_flux_from_soil_to_groundwater (kg m-2 s-1)
'In accordance with common usage in geophysical disciplines, "flux" implies per
unit area, called "flux density" in physics. Groundwater is subsurface water
below the depth of the water table, including soil moisture and underground
aquifers.'
I notice the wording of the suggested definition of groundwater differs from
the one we have discussed in other LS3MIP proposals, although I think the
meaning is the same. For consistency I have used the same wording as other
proposals for now. I am aware that there is still some work being done on
clarifying the definition of groundwater and we will need to wait for the
outcome of that before we can finalise this name.
This name is still under discussion.
7.2 sblnosn Sublimation of the snow free area [kg m-2 s-1]
This is a variation of the CMIP5 variable "sbl" which used the existing term
surface_snow_and_ice_sublimation_flux. Here, we just drop "and_ice" > to get a
term referring to the ice only.
surface_ice_sublimation_flux
Looking at existing names I see we also have surface_snow_sublimation_amount.
Rather than talking about sublimation amount in one name and sublimation flux
in others I think it would make sense to take a more uniform approach. I think
the primary purpose of the existing surface_snow_and_ice_sublimation_flux name
is to describe changes at the surface, rather than a water vapour flux into the
atmosphere. Hence I suggest introducing aliases:
surface_snow_sublimation_amount ->
tendency_of_surface_snow_amount_due_to_sublimation
surface_snow_and_ice_sublimation_flux ->
tendency_of_surface_snow_and_ice_amount_due_to_sublimation
and calling the proposed quantity:
tendency_of_ice_amount_due_to_sublimation.
None of these names specify that the snow and ice are located on land, so as
with the albedo and evaporation names we probably need to use them in
conjunction with an area type. Do you agree with this approach?
7.3 snmsl Water flowing out of snowpack [kg m-2 s-1]
This is a variation of snm [surface_snow_melt_flux], but considering only the
component of the flux into soil:
surface_snow_melt_flux_into_soil
For this name I suggest a different form:
liquid_water_mass_flux_into_soil_due_to_surface_snow_melt (kg m-2 s-1)
There are a number of reasons for suggesting this. The existing
surface_snow_melt_flux name isn't very clear in my opinion. It doesn't say
where the flux is going (or even that it is a mass flux, although that is
mentioned in the definition). It might even be better to change the existing
name to something like tendency_of_surface_snow_amount_due_to_melting. The
other reason I am suggesting a different form for the proposed quantity is
because of the use of the phrase 'surface_snow' in standard names to mean snow
lying on the surface. I think there's some potential for confusing surface_snow
with a surface_flux (i.e. flux in or out of the atmosphere) when that clearly
isn't intended. The definition would be as follows:
'In accordance with common usage in geophysical disciplines, "flux" implies per
unit area, called "flux density" in physics. The specification of a physical
process by the phrase "due_to_" process means that the quantity named is a
single term in a sum of terms which together compose the general quantity named
by omitting the phrase. The phrase "surface_snow" means snow lying on the
surface.'
Okay?
The sentence explaining that surface_snow means lying snow is new, but I think
we should add it to all existing surface snow names. Do others agree?
This name is still under discussion.
7.4 snwc Snow intercepted by the vegetation [kg m-2]
There is an existing term "canopy_water_amount", hence:
canopy_snow_amount
I think the name and units are fine. The definition would be:
' "Amount" means mass per unit area. "Canopy" means the plant or vegetation
canopy. The phrase "canopy_snow" means snow lying on the canopy.'
This one is a straight forward addition to the standard name table. It is
accepted for publication and will be added in the June update.
7.5 sw Surface Water Storage (excluding snow) [kg m-2]
The existing term surface_water_amount refers to ".. the amount on the ground,
excluding that on the plant or vegetation canopy", and "water" is assumed to
refer to all phases. There is a term "land_based_water_amount" under
discussion for PMIP which refers to "This quantity is often known as
Terrestrial Water Storage. It includes surface water (water in rivers,
wetlands, lakes, snow, vegetation and reservoirs) and subsurface water (soil
moisture, groundwater)".
Assuming that this term is intended to be a variation on the first,
surface_water_amount, and the amount includes only liquid phase water
(excluding snow and ice):
surface_liquid_water_amount
I note that the PMIP name you refer to is currently listed as
land_water_amount. Given that this variable is related and is clearly limited
to surface water on land (i.e. it excludes surface sea water) I suggest:
land_surface_liquid_water_amount (kg m-2)
'The surface called "surface" means the lower boundary of the atmosphere.
"Amount" means mass per unit area. The quantity with standard name
land_surface_liquid_water_amount includes water in rivers, wetlands, lakes,
snow, vegetation and reservoirs.'
I am aware that there is still some work being done on clarifying the
definition of land water and we will need to wait for the outcome of that
before we can finalise this name.
This name is still under discussion.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email:
alison.pamm...@stfc.ac.uk<mailto:alison.pamm...@stfc.ac.uk>
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
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