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
woul
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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