Dear Alison,
Thank you for reviewing all these. The "_clear_sky_and_no_aerosol" names look
good.
6. & 7.
For the albedo terms: You are right about "spectral": this was included because
the CMIP6 variables which need this standard name are requested in spectral frequency
bands, but the term requested is an albedo, not an albedo per unit wave-number.
I believe that "spherical" and "hemispherical" have distinct meanings when applied to radiation terms. From ISO 9288-1996 ["Thermal
insulation — Heat transfer by radiation .."]: "hemispherical" is used for quantities which "are related to all directions along which a
surface element can emit or receive radiation", which I think applies here. Spherical irradiance refers to the total irradiance incident on a point from
all angles. Hence, I think we should stay with hemispherical reflectance. On the other hand, "surface hemispherical reflectance" and "surface
albedo" appear to mean the same thing, and we already have "surface_albedo", so it may be better to use that phrase here. I had not looked into
this enough before, so thank you for querying the original suggestion.
The surface_albedo term makes no reference to the wavelength at which it should
be calculated, but I believe that it is generally considered to be a quantity
associated with shortwave radiation. Hence, I suggest we can drop this
qualifier -- but only if everyone agrees that surface_albedo should, at least
by default, apply to solar radiation.
Finally, "downwelling" is redundant here, since it is implicit in the
definition of surface albedo. After these simplifying assumptions, we could use:
direct_surface_albedo
and
diffuse_surface_albedo.
8:
Yes, this the associated CMIP6 variable is the total incoming shortwave flux in
bands, so a new name is not needed.
9 & 10
volume_extinction_coefficient_in_air_due_to_ambient_aerosol_particles and
single_scattering_albedo_in_air_due_to_ambient_aerosol_particles: I agree.
11
aerasym:
volume_spectral_asymmetry_factor_in_air_due_to_ambient_aerosol_particles
"asymmetry factor" and "backscatter fraction" appear to be two well defined
terms. I'll check with Robert Pincus to see which one he wants.
Looking at this again, I'm concerned that the use of "due_to_" is not entirely correct here: both "asymmetry factor"
and "backscatter fraction" are properties of the particles ... I don't think it is part of an additive collection of terms which
the use of "due_to" appears to imply. Hence, accepting your comments about "volume" and "spectral", I suggest:
asymmetry_factor_of_ambient_aerosol_particles or
backscatter_fraction_of_ambient_aerosol_particles
regards,
Martin
________________________________
Alison Pamment - UKRI STFCalison.pamment at stfc.ac.uk
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Dear All,
Standard names were proposed some time ago for CMIP6 RFMIP and some of the
names received a small amount of discussion back in 2016. However, none of the
names were published at that time. Three names were proposed for GeoMIP as long
ago as 2015, but strangely, although I have a copy of the GeoMIP email (which
was addressed to the mailing list) it seems never to have actually appeared on
the list. The RFMIP and GeoMIP quantities are similar, so I will address both
in this message. I would particularly like some advice on RFMIP proposals 6 -
11.
GeoMIP
1. stratosphere_optical_thickness_due_to_ambient_aerosol_particles (1)
The same quantity was recently proposed for PMIP and added in Version 53 of the
standard name table, so this one is done.
2. toa_outgoing_shortwave_flux_assuming_clear_sky_and_no_aerosol (Wm-2)
This is the same as RFMIP proposal 1 (see below), so I will deal with this one
as part of the RFMIP request.
3. toa_outgoing_shortwave_flux_assuming_no_aerosol (W m-2)
This proposal is straight forward. We have one existing assuming_no_aerosol
name,
volume_attenuated_backwards_scattering_function_in_air_assuming_no_aerosol_or_cloud.
The definition can be constructed from existing text:
'The abbreviation "toa" means top of atmosphere. The term "shortwave" means shortwave radiation. The TOA outgoing shortwave flux is the
reflected and scattered solar radiative flux i.e. the "upwelling" TOA shortwave flux, sometimes called the "outgoing shortwave radiation"
or "OSR". In accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in
physics. A phrase "assuming_condition" indicates that the named quantity is the value which would obtain if all aspects of the system were unaltered
except for the assumption of the circumstances specified by the condition.'
This name is accepted for publication in the standard name table and has been
included in this week's update.
RFMIP
1. toa_outgoing_shortwave_flux_assuming_clean_clear_sky (W m-2)
Jonathan commented (in 2016) that it would be preferable to say 'no_aerosol'
rather than 'clean'
(http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2016/059135.html). I have
seen some offlist emails that indicate 'no_aerosol' is now being used in
preference to 'clean' in the CMIP6 long names. Also, this is consistent with
the one existing no_aerosol name and the GeoMIP proposals.
This one should therefore be as follows:
toa_outgoing_shortwave_flux_assuming_clear_sky_and_no_aerosol (W m-2)
'The abbreviation "toa" means top of atmosphere. The term "shortwave" means shortwave radiation. The TOA outgoing shortwave flux is the reflected and
scattered solar radiative flux i.e. the "upwelling" TOA shortwave flux, sometimes called the "outgoing shortwave radiation" or "OSR". In
accordance with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. A phrase
"assuming_condition" indicates that the named quantity is the value which would obtain if all aspects of the system were unaltered except for the assumption of
the circumstances specified by the condition. "Clear sky" means in the absence of clouds.'
This name, units and definition are consistent with existing names so it is
accepted and has been added in this week's standard name table update.
This proposal has been around for a long time and there is a possibility that
some data have been written with the original version of the name. For this
reason I have added toa_outgoing_shortwave_flux_assuming_clean_clear_sky to the
standard name table and then immediately turned it into an alias of
toa_outgoing_shortwave_flux_assuming_clear_sky_and_no_aerosol. This has been
achieved by updating the standard name table twice - both versions will be
published this week. (The double update is necessary to keep in sync with the
standard name publication process on the NERC Vocabulary Server). We don't
usually publish two versions of a name almost simultaneously, but there is a
precedent for treating long standing proposals in this way - for example it was
done for some standard names arising from trac ticket 37 which took a couple of
years to agree. This arrangement affects 5 names for RFMIP.
2. surface_downwelling_shortwave_flux_in_air_assuming_clean_clear_sky (W m-2)
As for proposal 1, we should replace 'clean' with 'no_aerosol':
surface_downwelling_shortwave_flux_in_air_assuming_clear_sky_and_no_aerosol (W
m-2)
'The surface called "surface" means the lower boundary of the atmosphere. Downwelling radiation is radiation from above. It does not mean "net downward". The
term "shortwave" means shortwave radiation. Surface downwelling shortwave is the sum of direct and diffuse solar radiation incident on the surface, and is sometimes
called "global radiation". When thought of as being incident on a surface, a radiative flux is sometimes called "irradiance". In addition, it is identical with
the quantity measured by a cosine-collector light-meter and sometimes called "vector irradiance". In accordance with common usage in geophysical disciplines,
"flux" implies per unit area, called "flux density" in physics. A phrase "assuming_condition" indicates that the named quantity is the value which
would obtain if all aspects of the system were unaltered except for the assumption of the circumstances specified by the condition. "Clear sky" means in the absence of
clouds.'
This name, units and definition are consistent with existing names so it is
accepted and will be added in this week's standard name table update. As for
proposal 1, I have published the original version of the name and immediately
turned it into an alias of the final version.
3. surface_upwelling_shortwave_flux_in_air_assuming_clean_clear_sky (W m-2)
As for proposal 1, we should replace 'clean' with 'no_aerosol':
surface_upwelling_shortwave_flux_in_air_assuming_clear_sky_and_no_aerosol (W
m-2)
'The surface called "surface" means the lower boundary of the atmosphere. Upwelling radiation is radiation from below. It does not mean "net upward".
The term "shortwave" means shortwave radiation. When thought of as being incident on a surface, a radiative flux is sometimes called "irradiance". In
addition, it is identical with the quantity measured by a cosine-collector light-meter and sometimes called "vector irradiance". In accordance with common
usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics. A phrase "assuming_condition" indicates
that the named quantity is the value which would obtain if all aspects of the system were unaltered except for the assumption of the circumstances specified by the
condition. "Clear sky" means in the absence of clouds.'
This name, units and definition are consistent with existing names so it is
accepted and will be added in this week's standard name table update. As for
proposal 1, I have published the original version of the name and immediately
turned it into an alias of the final version.
4. upwelling_shortwave_flux_in_air_assuming_clean_clear_sky (W m-2)
As for proposal 1, we should replace 'clean' with 'no_aerosol':
upwelling_shortwave_flux_in_air_assuming_clear_sky_and_no_aerosol (W m-2)
'Upwelling radiation is radiation from below. It does not mean "net upward". The term "shortwave" means shortwave radiation. When thought
of as being incident on a surface, a radiative flux is sometimes called "irradiance". In addition, it is identical with the quantity measured by a
cosine-collector light-meter and sometimes called "vector irradiance". In accordance with common usage in geophysical disciplines, "flux"
implies per unit area, called "flux density" in physics. A phrase "assuming_condition" indicates that the named quantity is the value which
would obtain if all aspects of the system were unaltered except for the assumption of the circumstances specified by the condition. "Clear sky" means
in the absence of clouds.'
This name, units and definition are consistent with existing names so it is
accepted and will be added in this week's standard name table update. As for
proposal 1, I have published the original version of the name and immediately
turned it into an alias of the final version.
5. downwelling_shortwave_flux_in_air_assuming_clean_clear_sky (W m-2)
As for proposal 1, we should replace 'clean' with 'no_aerosol':
downwelling_shortwave_flux_in_air_assuming_clear_sky_and_no_aerosol (W m-2)
'Downwelling radiation is radiation from above. It does not mean "net downward". The term "shortwave" means shortwave radiation. When
thought of as being incident on a surface, a radiative flux is sometimes called "irradiance". In addition, it is identical with the quantity measured
by a cosine-collector light-meter and sometimes called "vector irradiance". In accordance with common usage in geophysical disciplines,
"flux" implies per unit area, called "flux density" in physics. A phrase "assuming_condition" indicates that the named quantity
is the value which would obtain if all aspects of the system were unaltered except for the assumption of the circumstances specified by the condition.
"Clear sky" means in the absence of clouds.'
This name, units and definition are consistent with existing names so it is
accepted and will be added in this week's standard name table update. As for
proposal 1, I have published the original version of the name and immediately
turned it into an alias of the final version.
Now I am coming to some even older proposals for RFMIP, dating from 2015. They
received only one comment at the time and I think the names, units and
definitions need some work. For two of the quantities I think we can probably
use existing names. I hope Martin, Daniel and Robert will be able to advise on
these proposals.
6. CMIP6 short name albdiff.
surface_spectral_hemispherical_reflectance_of_diffuse_shortwave_radiation (1)
I think we probably shouldn't say 'spectral' in the name. We used to have
standard names that included 'spectral' but then we agreed to change them all
to say 'per_unit_wavelength' or 'per_unit_wavenumber'. Per_unit_wavelength
introduces a unit of m-1 and per_unit_wavenumber introduces a unit of (m-1)-1;
I suspect neither is appropriate in this case. We can still add a sentence in
the definition that would say something like 'The reflectance is assumed to be
an integral over all wavelengths, unless a coordinate of radiation_wavelength
or radiation_frequency is included to specify either the wavelength or
frequency' to allow the quantity to be specified at different wavelengths or
frequencies. We do this for quite a number of existing names.
We have an existing name downwelling_spherical_irradiance_in_sea_water defined as 'Downwelling radiation is radiation
from above. It does not mean "net downward". Spherical irradiance is the radiation incident on unit area of a
hemispherical (or "2-pi") collector. It is sometimes called "scalar irradiance". The direction
(up/downwelling) is specified. Radiation incident on a 4-pi collector has standard names of "omnidirectional
spherical irradiance".' This makes me think that we should refer to the proposed name as a 'spherical' rather than
'hemishpherical' reflectance - presumably it is the reflectance that would apply to any shortwave radiation arriving at
the surface from any upward direction. Apart from the omnidirectional names, all the existing 'spherical' names include
some sense of direction (upwelling or downwelling). Since the current proposal is for shortwave radiation incident at
the surface, I suggest we need to say 'downwelling'.
We do have existing names for diffuse radiation, e.g.
surface_diffuse_downwelling_shortwave_flux_in_air. We can just say 'shortwave'
instead of 'shortwave radiation' because that would be explained in the
definition.
Putting all this together, I think we would arrive at the following name, units
and definition:
surface_diffuse_downwelling_shortwave_spherical_reflectance (1)
'The surface called "surface" means the lower boundary of the atmosphere. "Diffuse" radiation is radiation
that has been scattered by particles in the atmosphere such as cloud droplets and aerosols. Downwelling radiation is radiation
from above. It does not mean "net downward". The term "shortwave" means shortwave radiation. Spherical
reflectance is the reflectance of radiation incident on unit area of a hemispherical (or "2-pi") collector. Reflectance
is the ratio of the energy of the reflected to the incident radiation. A coordinate variable of radiation_wavelength or
radiation_frequency can be used to specify the wavelength or frequency, respectively, of the radiation.'
What do others think?
7. CMIP6 short name albdir.
surface_spectral_hemispherical_reflectance_of_direct_shortwave_radiation (1)
We have one existing name for direct radiation,
direct_downwelling_shortwave_flux_in_air.
Following similar arguments to proposal 6, I suggest this one should be:
surface_direct_downwelling_shortwave_spherical_reflectance (1)
'The surface called "surface" means the lower boundary of the atmosphere. "Direct" (also known as "beam") radiation is
radiation that has followed a direct path from the sun and is alternatively known as "direct insolation". Downwelling radiation is
radiation from above. It does not mean "net downward". The term "shortwave" means shortwave radiation. Spherical reflectance is
the reflectance of radiation incident on unit area of a hemispherical (or "2-pi") collector. Reflectance is the ratio of the energy of the
reflected to the incident radiation. A coordinate variable of radiation_wavelength or radiation_frequency can be used to specify the wavelength or
frequency, respectively, of the radiation.'
Do others agree?
8. CMIP6 short name sol.
toa_incoming_shortwave_flux_per_unit_wavelength (W m-2)
If this is intended to be a truly spectrally resolved quantity, then the name
is correct, but as I mentioned for proposal 6 the units should be W m-2 m-1. We
do have an existing name toa_incoming_shortwave_flux which is integrated across
all shortwave frequencies.
If we leave the name as it is, then we would have:
toa_incoming_shortwave_flux_per_unit_wavelength (W m-2 m-1)
'The abbreviation "toa" means top of atmosphere. The term "shortwave" means shortwave radiation. The TOA
incoming shortwave flux is the radiative flux from the sun i.e. the "downwelling" TOA shortwave flux. In accordance
with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.
A coordinate variable for radiation wavelength should be given the standard name radiation_wavelength.'
If these units are not acceptable we could use the existing name
toa_incoming_shortwave_flux (W m-2)
'The abbreviation "toa" means top of atmosphere. The term "shortwave" means shortwave radiation. The TOA
incoming shortwave flux is the radiative flux from the sun i.e. the "downwelling" TOA shortwave flux. In accordance
with common usage in geophysical disciplines, "flux" implies per unit area, called "flux density" in physics.'
The definition is the same except for the sentence about the coordinate
variable. We could add a slightly softer version of that sentence, similar to
the reflectance names, 'A coordinate variable of radiation_wavelength or
radiation_frequency can be used to specify the wavelength or frequency,
respectively, of the radiation.' This would allow wavelength to be used as a
dimension, but wouldn't alter the units.
What do others think?
9. CMIP6 short name aerext.
volume_spectral_extinction_coefficient_in_air_due_to_ambient_aerosol_particles
(1)
As with the reflectance proposals, we shouldn't say 'spectral' in the name and
if we say 'per_unit_wavelength' it would alter the units. In fact, for this
quantity I think we have an existing name that would do the job:
volume_extinction_coefficient_in_air_due_to_ambient_aerosol_particles (1)
'The volume extinction coefficient is the fractional change of radiative flux per unit path length. Extinction is the sum of absorption and
scattering, sometimes called "attenuation". "Extinction" is the term most commonly used at optical wavelengths whereas
"attenuation" is more often used at radio and radar wavelengths. "Aerosol" means the system of suspended liquid or solid
particles in air (except cloud droplets) and their carrier gas, the air itself. "Ambient_aerosol" means that the aerosol is measured or
modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient aerosol
particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth depends on the
relative humidity and the composition of the particles. 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.'
Again, we could add an advisory sentence to the definition to say that a
coordinate variable of radiation_wavelength can be specified. What do others
think?
10. CMIP6 short name aerssa.
volume_spectral_single_scattering_albedo_in_air_due_to_ambient_aerosol_particles
(1)
This one is similar to proposal 9. Again we shouldn't say 'spectral' and there
is the question of units. I think this is another one for which we have an
existing name:
single_scattering_albedo_in_air_due_to_ambient_aerosol_particles (1)
'"Single scattering albedo" is the fraction of radiation in an incident light beam scattered by the particles of an aerosol reference
volume for a given wavelength. It is the ratio of the scattering and the extinction coefficients of the aerosol particles in the reference volume. A
coordinate variable with a standard name of radiation_wavelength or radiation_frequency should be included to specify either the wavelength or
frequency. "Aerosol" means the system of suspended liquid or solid particles in air (except cloud droplets) and their carrier gas, the air
itself. "Ambient_aerosol" means that the aerosol is measured or modelled at the ambient state of pressure, temperature and relative
humidity that exists in its immediate environment. "Ambient aerosol particles" are aerosol particles that have taken up ambient water
through hygroscopic growth. The extent of hygroscopic growth depends on the relative humidity and the composition of the particles. To specify the
relative humidity and temperature at which the quantity described by the standard name applies, provide scalar coordinate variables with standard
names of "relative_humidity" and "air_temperature". 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.'
As with proposal 9, we could add an advisory sentence to the definition to say
that a coordinate variable of radiation_wavelength can be specified. What do
others think?
11. CMIP6 short name aerasym.
volume_spectral_asymmetry_factor_in_air_due_to_ambient_aerosol_particles (1)
I am not really familiar with this quantity, but I note Markus Fiebig's comment
(http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2015/058422.html) when the
names were originally proposed to the mailing list:
For the aerosol asymmetry factor / parameter, I'm familiar with the definition
as the cosine weighted angular integral of the aerosol scattering
phase function. For the property you describe, I know the term "backscatter
fraction", i.e. the ratio of the integral over the scattering phase
function in the backward hemisphere (backscatter coefficient) over the aerosol
scattering coefficient.
It sounds like this one is a new quantity to standard names. Again, I don't
think the name itself should say 'spectral'. Rather than 'factor' I would
suggest the term 'coefficient' which is already used in existing names. Also, I
don't know whether we really need 'volume' in this case - I think this refers
to extinction along the path of the radiation and volume coefficients have
units of m-1. Does the asymmetry factor refer to a single scattering event or
to multiple events along a path? I suggest the name would be:
[volume_]asymmetry_coefficient_of_radiative_flux_in_air_due_to_ambient_aerosol_particles
(1)
and the definition would be something like:
'The asymmetry coefficient is the ratio of forward to backward scattered radiative flux. The asymmetry coefficient is assumed to be an
integral over all wavelengths, unless a coordinate of radiation_wavelength is included to specify the wavelength. 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. "Aerosol" means the system of suspended liquid or solid particles in
air (except cloud droplets) and their carrier gas, the air itself. "Ambient_aerosol" means that the aerosol is measured or
modelled at the ambient state of pressure, temperature and relative humidity that exists in its immediate environment. "Ambient
aerosol particles" are aerosol particles that have taken up ambient water through hygroscopic growth. The extent of hygroscopic growth
depends on the relative humidity and the composition of the particles. To specify the relative humidity and temperature at which the
quantity described by the standard name applies, provide scalar coordinate variables with standard names of "relative_humidity"
and "air_temperature".'
What do others think?
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
NCAS/Centre for Environmental Data Archival Email: alison.pamment at
stfc.ac.uk<http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata>
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
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