Dear Michael, All,
I have been promising for some time to review all the standard names proposed in relation to the GOES-R satellite programme. A total of 36 standard names and 6 area types were proposed and discussed in a large number of mailing list threads during 2013-14. The original proposals were made by a number of people, namely Randy Horne, Gary Meehan, Jonathan Wrotny and Ted Kennelly. Michael wrote to me recently to say that he is taking over from Randy in seeing all the GOES-R names through to publication.
I have now completed a review of all the proposals and my detailed comments on each one are given below. A summary of the current status of the standard name proposals can be viewed at
http://cfeditor.ceda.ac.uk/proposals/1?status=active&namefilter=&proposerfilter=&descfilter=&unitfilter=&yearfilter=&commentfilter=GOES-R&filter+and+display=Filter. A summary of the area type proposals can be viewed in point 16 of my comments below.
Of the 36 standard names proposed in relation to GOES-R, 3 are already in standard name table, 23 are now accepted for publication and 10 need further discussion (primarily to clarify the definitions). The 6 new area types are now accepted for publication in the area type table. The standard name and area type tables will both be updated one week from today, on 8 July 2015, when all accepted names will be added. Any names currently under discussion that can be agreed in the intervening period will also be added on 8 July. Names that require a longer period of discussion will be held over until the next standard name table update, planned for approximately 2 months time.
1. Thread: "Proposal for New Standard Names: "clear_area_fraction" and "probably_clear_area_fraction, probably_cloudy_area_fraction"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/057049.html)
Current status: Accepted.
clear_sky_area_fraction (canonical units: 1)
' "X_area_fraction" means the fraction of horizontal area occupied by X. "X_area" means the horizontal area occupied by X within the grid cell. The clear_sky area fraction is for the whole atmosphere column, as seen from the surface or the top of the atmosphere.'
This name was discussed and agreed in the mailing list thread.
2. Thread: "new standard names: day, night, and day/night terminator area_fractions".
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057093.html)
2a. Current status: Accepted.
area_fraction_of_day_defined_by_solar_zenith_angle (canonical units: 1)
' "X_area_fraction" means the fraction of horizontal area occupied by X. "X_area" means the horizontal area occupied by X within the grid cell. A coordinate variable of solar_zenith_angle indicating the day extent should be specified.'
This name was discussed and agreed in the mailing list thread.
2b. Current status: Accepted.
area_fraction_of_night_defined_by_solar_zenith_angle (canonical units: 1)
' "X_area_fraction" means the fraction of horizontal area occupied by X. "X_area" means the horizontal area occupied by X within the grid cell. A coordinate variable of solar_zenith_angle indicating the day extent should be specified.'
This name was discussed and agreed in the mailing list thread.
2c. Current status: Accepted.
area_fraction_of_twilight_defined_by_solar_zenith_angle (canonical units: 1)
' "X_area_fraction" means the fraction of horizontal area occupied by X. "X_area" means the horizontal area occupied by X within the grid cell. A coordinate variable of solar_zenith_angle indicating the day extent should be specified.'
This name was discussed and agreed in the mailing list thread.
3. Threads: "new standard name: geopotential_height_at_cloud_top" and "vertical datums and new standard name: geopotential_height_at_cloud_top"
(
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057239.html)
Current status: Accepted.
geopotential_height_at_cloud_top (canonical units: m)
'Cloud_top refers to the top of the highest cloud. Geopotential is the sum of the specific gravitational potential energy relative to the geoid and the specific centripetal potential energy. Geopotential height is the geopotential divided by the standard acceleration due to gravity. It is numerically similar to the altitude (or geometric height) and not to the quantity with standard name "height", which is relative to the surface.'
There was only a little discussion of this name on the mailing list, focusing on the vertical datum rather than the name itself. The proposal is consistent with the existing name geopotential_height_at_volcanic_ash_cloud_top and the units and definition are fine, so I am accepting this name for publication in the standard name table.
4. Thread: "new standard_name: sunglint_angle"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057160.html)
Current status: Accepted.
sunglint_angle (canonical units: rad)
'The sunglint angle is that between the direction of an incident beam of solar radiation and the outgoing beam after undergoing specular reflection at a sea surface.'
Only one comment was received on this name which led to the reference to sea surface being added to the definition. No objections were received. I have taken the liberty of making the language of the definition a little more formal but otherwise the proposal looks fine, so I am accepting this name for publication in the standard name table.
5. Thread: "new standard name proposal: brightness_temperature_at_cloud_top"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057397.html)
Current status: Accepted.
brightness_temperature_at_cloud_top (canonical units: K)
'cloud_top refers to the top of the highest cloud. The brightness_temperature of a body is the temperature of a black body which radiates the same power per unit solid angle per unit area. A coordinate variable of radiation_wavelength, sensor_band_central_radiation_wavelength, or radiation_frequency may be specified to indicate that the brightness temperature applies at specific wavelengths or frequencies.'
This proposal received no comments on the mailing list. The syntax matches that of existing names and the units and definition are fine. This name is accepted for publication in the standard name table.
6. A total of 11 names relating to tropical cyclones were proposed, under a number of different mailing list threads.
Several of the names refer to the Advanced Dvorak Technique which analyses and predicts the behaviour of tropical cyclones based on satellite imagery and idealised modelling. The method is well documented and it would be helpful to include a reference in the definition of all the 'dvorak' names. I have added a reference to the following paper that I found online: Olander and Velden, 20ll, Weather and Forecasting, doi:10.1175/WAF975.1. If there is a more suitable reference, please could you provide it?
6a. Thread: "Proposed Standard Name: dvorak_tropical_cyclone_current_intensity_number"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057271.html)
Current status: under discussion
dvorak_tropical_cyclone_current_intensity_number (canonical units: 1)
' "Dvorak current intensity number" means the ranking (1 to 8) of tropical cyclone strength derived using the Advanced Dvorak Technique based on satellite observations, which has been empirically related to maximum sustained 1-minute wind speed and mean sea level atmospheric pressure.'
No comments were received on this name following the original proposal. Having done some reading around the subject, it appears that the Current Intensity (CI) number relates cyclone intensity to maximum wind speed in particular, rather than mean sea level pressure (MSLP). The relationship between intensity and MSLP seems to be summarized in the Tropical (T) number which I think is the subject of proposal 6b. Please can you confirm whether this is correct? The definitions of 6a and 6b should make clear the difference between the two names and a reference to the Advanced Dvorak Technique should be added.
The name itself and the canonical units are fine.
6b. Thread: "Proposed Standard Name: dvorak_tropical_number"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057272.html)
Current status: under discussion
dvorak_tropical_number (canonical units: 1)
' "dvorak_tropical_number" means the tropical number derived using the Advanced Dvorak Technique based on satellite observations, which has been empirically related to maximum sustained 1-minute wind speed and mean sea level atmospheric pressure.'
No comments were received on this name following the original proposal. Please can you confirm whether my interpretation of 6a and 6b is correct (see 6a). I suggest that this name should be dvorak_tropical_cyclone_number for consistency of wording with 6a and to make clear that it relates to cyclones. The units are fine.
6c. Thread: "Proposed Standard Name: tropical_cyclone_eye_temperature"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057273.html)
Current status: Accepted.
tropical_cyclone_eye_brightness_temperature (canonical units: K)
' "tropical_cyclone_eye_brightness_temperature" means the warmest brightness temperature value in the eye region of a tropical cyclone (0 - 24 km from the storm center) derived using the Advanced Dvorak Technique, based on satellite observations. Reference: Olander and Velden, 20ll, Weather and Forecasting, doi:10.1175/WAF975.1.'
This name was discussed and agreed in the mailing list thread. I have added a reference to the Advanced Dvorak Technique to the definition.
6d. Thread: "Proposed Standard Name: tropical_cyclone_maximum_sustained_wind_speed"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057282.html)
Current status: Accepted.
tropical_cyclone_maximum_sustained_wind_speed (canonical units: m s-1)
' "tropical_cyclone_maximum_sustained_wind_speed" means the maximum sustained wind speed of a tropical cyclone, sustained over a period of one minute at the surface of the earth, derived using the Advanced Dvorak Technique based on satellite observations. Reference: Olander and Velden, 20ll, Weather and Forecasting, doi:10.1175/WAF975.1.'
This name received a comment from Jonathan Gregory asking about the period over which the wind is sustained and at what atmospheric level. I have incorporated the answer into the definition. I have also added a reference to the Advanced Dvorak Technique. Otherwise this name seems fine, so I am accepting it for publication in the standard name table.
6e. Thread: "new standard name: automated_tropical_cyclone_forecasting_system_storm_identifier"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057390.html)
Current status: Under discussion.
automated_tropical_cyclone_forecasting_system_storm_identifier (canonical units: 1)
' Definition:
Contains an 8 character string, BBCCYYYY which identifies a tropical cyclone. A string type variable should not normally have a "units" attribute.
BB is the ocean basin, specifically:
AL - North Atlantic basin; north of the Equator
SL - South Atlantic basin; south of the Equator
EP - North East Pacific basin; eastward of 140 degrees west longitude
CP - North Central Pacific basin; between the dateline and 140 degrees west longitude
WP -North West Pacific basin; westward of the dateline
IO - North Indian Ocean basin; north of the Equator between 40 and 100 degrees east longitude
SH - South Pacific Ocean basin and South Indian Ocean basin
CC is the cyclone number.
Numbers 01 through 49 are reserved for tropical and subtropical cyclones. A cyclone number is assigned to each tropical or subtropical cyclone in each basin as it develops. Numbers are assigned in chronological order. Numbers 50 through 79 are reserved for internal use by operational forecast centers. Numbers 80 through 89 are reserved for training, exercises and testing. Numbers 90 through 99 are reserved for tropical disturbances having the potential to become tropical or subtropical cyclones. The 90's are assigned sequentially and reused throughout the calendar year.
YYYY is the four-digit year
Calendar year for the northern hemisphere. For the southern hemisphere, the year begins July 1, with calendar year plus one.'
No comments were received on this name following the original proposal. We have existing standard names for string valued variables such as region, area_type, platform_name and sensor_band_identifier. The values of the first two are standardised while the second two are not. The proposed name would be another example of a standardised string valued variable and the possible values are described in the definition, so that is fine. A string type variable should not normally have a "units" attribute so the canonical units should be left blank. (I've added a sentence to the definition regarding units). As for the name itself, is there only one "automated tropical cyclone forecasting system" in existence? I.e. is the naming convention referred to in this name universally recognised or are there any "competitor" names that could be assigned to the same cyclone by a different forecasting system?
I will also send a separate email to the list on the subject of units for string valued variables, as there are a couple of issues with this in the standard name table.
6f. Thread: "Proposed Standard Name: radius_of_tropical_cyclone_eye"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057391.html)
Current status: Accepted.
radius_of_tropical_cyclone_eye (canonical units: m)
'The radius of a tropical cyclone eye defined to be the great circle distance measured from the cyclone center to the eye wall.'
No comments were received on this name following the original proposal. The name, definition and units all seem fine and the general syntax is consistent with other cyclone names in this set of proposals and existing names for "effective_radius_of_X". Therefore I am accepting this name for publication in the standard name table.
6g. Thread: "Proposed Standard Name: radius_of_tropical_cyclone_central_dense_overcast_region"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057399.html)
Current status: Accepted.
radius_of_tropical_cyclone_central_dense_overcast_region (canonical units: m)
'The average radius of a central region of clouds in tropical cyclones lacking well-defined eye features, which is computed by averaging the great circle distance in four cardinal directions. The radius in each direction is measured from the estimated storm center position to a warm point that exceeds a
threshold brightness temperature at top of atmosphere limit. The threshold applied should be recorded in a coordinate variable having the standard_name of toa_brightness_temperature. A coordinate variable of radiation_wavelength, sensor_band_central_radiation_wavelength, or radiation_frequency may be specified to indicate that the brightness temperature applies at specific wavelengths or frequencies.'
This name received a number of comments following the original proposal. It was discussed and agreed in the mailing list thread: it is now accepted for publication in the standard name table.
6h. Thread: "new standard name proposal: dvorak_tropical_cyclone_cloud_region_scene_type"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057409.html)
Current status: Accepted
scene_type_of_dvorak_tropical_cyclone_cloud_region (canonical units: 1)
'A variable with the standard name of scene_type_of_dvorak_tropical_cyclone_cloud_region contains integers which can be translated to strings using flag_values and flag_meanings attributes. It indicates the Advanced Dvorak Technique tropical cyclone cloud region scene type chosen from the following list: uniform_central_dense_overcast; embedded_center; irregular_central_dense_overcast; curved_band; shear. Alternatively, the data variable may contain strings chosen from the same standardised list to indicate the scene type. Reference: Olander and Velden, 20ll, Weather and Forecasting, doi:10.1175/WAF975.1.'
This name received some brief discussion on the mailing list and was agreed. I have added a reference to the Advanced Dvorak Technique to the definition and have rearranged the wording to be more consistent with that used for existing names referring to flag_values and flag_meanings. This name is accepted for publication in the standard name table.
6i. Thread: "standard_name proposal: dvorak_tropical_cyclone_eye_region_scene_type"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057423.html)
Current status: Accepted
scene_type_of_dvorak_tropical_cyclone_eye_region (canonical units: 1)
'A variable with the standard name of scene_type_of_dvorak_tropical_cyclone_eye_region contains integers which can be translated to strings using flag_values and flag_meanings attributes. It indicates the Advanced Dvorak Technique tropical cyclone eye region scene type chosen from the following list: clear_ragged_or_obscured_eye; pinhole_eye; large_eye; no_eye. Alternatively, the data variable may contain strings chosen from the same standardised list to indicate the scene type. Reference: Olander and Velden, 20ll, Weather and Forecasting, doi:10.1175/WAF975.1.'
This name received some brief discussion on the mailing list and was agreed. I have added a reference to the Advanced Dvorak Technique to the definition and have rearranged the wording to be more consistent with that used for existing names referring to flag_values and flag_meanings. This name is accepted for publication in the standard name table.
6j. Thread: "New Standard Name: distance_from_tropical_cyclone_center_to_leading_edge_of_displaced_convection"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057410.html)
Current status: Accepted.
distance_from_tropical_cyclone_center_to_leading_edge_of_displaced_convection (canonical units: m)
'The great circle distance measured from the tropical cyclone center to the leading edge of displaced convection, which is defined as the closest point that exceeds a threshold brightness temperature at top of atmosphere limit. The threshold applied should be recorded in a coordinate variable having the standard name of toa_brightness_temperature. A coordinate variable with standard name of radiation_wavelength, sensor_band_central_radiation_wavelength, or radiation_frequency may be specified to indicate that the brightness temperature applies at specific wavelengths or frequencies.'
No comments were received on this name but, for consistency, the definition was amended by the original proposer following discussion of radius_of_tropical_cyclone_central_dense_overcast_region. The name itself is consistent with other proposals and existing names and the units are fine. This name is accepted for publication in the standard name table.
6k. Thread: "Proposed New Standard Name: radius_of_tropical_cyclone_maximum_sustained_winds"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057416.html)
Current status: Accepted.
radius_of_tropical_cyclone_maximum_sustained_winds (canonical units: m)
'The great circle distance measured from the tropical cyclone center to the region of sustained 1-minute duration maximum wind speed, as defined by the standard name, tropical_cyclone_maximum_sustained_wind_speed.'
This name received some brief discussion on the mailing list and was agreed: it is now accepted for publication.
7. Thread: "Proposing Standard Names for Lightning Event, Group and Flash Radiant Energy"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057500.html)
Current status: Accepted.
lightning_radiant_energy (canonical units: J)
'The standard name "lightning radiant energy" means the energy emitted as electromagnetic radiation due to lightning. A coordinate variable of radiation_wavelength, radiation_frequency, or sensor_band_central_wavelength may be specified to indicate that the lightning_radiant_energy applies at specific wavelengths or frequencies. Bounds of the time and spatial coordinates may be specified to indicate the time interval and spatial extent over which the energy is emitted.'
The original proposal in this thread was for three separate names for lightning event, group and flash. During the discussion this was refined to a single name and the definition extended to explain the use of coordinate bounds. This name was agreed in the discussion and is now accepted for publication in the standard name table.
8. Thread: "new standard names: fire area, fire, temperature, fire radiative power"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056782.html)
The three original proposals in this mailing list thread were quickly agreed. Later, an amendment was discussed regarding specialising the names into different fire classifications of 'flaming', 'smouldering' and 'composite'. However, this more complex idea was not pursued, so here I am considering only the generic (agreed) names. If more specialised names are required now or in the future I suggest that they should be newly proposed to the list so that they can be discussed more fully.
N.B. I have added some cross-references to the definitions of the names. Also, the discussion made clear that these names refer to burning biomass so I have made sure that is mentioned in all three definitions.
8a. Current status: Accepted.
fire_area (canonical units: m2)
' "X_area" means the horizontal area occupied by X within the grid cell. "Fire area" means the area of detected biomass fire.'
8b. Current status: Accepted.
fire_temperature (canonical_units: K)
'The overall temperature of a fire area due to contributions from smoldering and flaming biomass. A data variable containing the area affected by fire should be given the standard name fire_area.'
8c. Current status: Accepted.
fire_radiative_power (canonical_units: W)
'The product of the irradiance (the power per unit area) of a biomass fire and the corresponding fire area. A data variable containing the area affected by fire should be given the standard name fire_area.'
9. Thread "new standard_name needed for cloud_phase (an enumeration type)"
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056424.html)
Current status: Under discussion.
cloud_phase_category (canonical units: 1)
'Cloud phase category is a string, taking one of the following standardised values: clear_sky, liquid_water, super_cooled_liquid_water, mixed_phase, ice, unknown. For a data variable it is encoded as an integer using flag_values and flag_meanings.'
This name received some brief discussion on the mailing list and was agreed at the time. However, I was looking through existing names whose definitions also refer to flag_values and flag_meanings because I wanted to check that the wording of the proposed definition is broadly consistent. In doing so I came across the name thermodynamic_phase_of_cloud_water_particles_at_cloud_top, introduced into the standard name table at Version 24 (June 2013), for use with Meteosat Second Generation (MSG) data. The existing name is defined as follows:
' "cloud_top" refers to the top of the highest cloud. "Water" means water in all phases. A variable with the standard name of thermodynamic_phase_of_cloud_water_particles_at_cloud_top contains integers which can be translated to strings using flag_values and flag_meanings attributes. Alternatively, the data variable may contain strings which indicate the thermodynamic phase. These strings are standardised. Values must be chosen from the following list: liquid; ice; mixed.'
Although the list of standardised values is not the same as proposed for GOES-R, I think the existing name is basically the same quantity as the one requested. My suggestion is that, instead of adding the new name, we expand the definition of the existing name to allow for all the strings needed for both MSG and GOES-R data, as follows:
' "cloud_top" refers to the top of the highest cloud. "Water" means water in all phases. A variable with the standard name of thermodynamic_phase_of_cloud_water_particles_at_cloud_top contains integers which can be translated to strings using flag_values and flag_meanings attributes. Alternatively, the data variable may contain strings which indicate the thermodynamic phase. These strings are standardised. Values must be chosen from the following list: liquid; ice; mixed; clear_sky; super_cooled_liquid_water; unknown.'
The standardised strings for liquid_water and mixed_phase would be slightly different from those agreed in the discussion of the current proposal, but if the names are to be combined I think we would need to stick with the earlier strings so as not to invalidate existing MSG data. Expanding the list of standardised strings would not affect existing data as I don't think there is any requirement to use all possible values of flag_values and flag_meanings within a particular data variable. One of the reasons for using standard names in CF is to avoid accidental duplication of quantities with the same meaning but different names, so I think that expanding the existing definition is the right way to go. Do you agree?
10. Thread "New reflectance standard names".
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http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056462.html)
The two names proposed in this thread received a number of comments on the mailing list, and led to a more general discussion of the definition of albedo. The last comment in the conversation was from Karl Taylor who suggested that the term 'albedo' may not be the best choice for quantities with a wavelength dependency and proposed that CF should reserve the use of that term for names applying to the full spectrum (
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056711.html). He further suggested that the two lambertian names should use the term 'hemispherical_reflectivity' instead of 'albedo'. There was no further discussion at the time, so this point does not appear to have been resolved.
The question of albedo definition is likely to surface again on the mailing list in the coming months in connection with climate model output for the CMIP6 project. At least one of the experiments in CMIP6 will require names for albedo/reflectance for a specific wavelength. If we can agree this issue now then it will enable me to give consistent advice to both GOES-R and CMIP data producers and perhaps avoid the need to create standard name aliases later on. In the reference that Karl provided,
http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Reflectivity.html, reflectivity is defined as 'the fraction of incident radiation reflected by a surface. In general it must be treated as a directional property that is a function of the reflected direction, the incident direction, and the incident wavelength. However it is also commonly averaged over the reflected hemisphere to give the hemispherical spectral reflectivity.'
We have existing standard names for surface_bidirectional_reflectance and toa_bidirectional_reflectance which depend on the angles of incidence and reflection. (According to Karl's refererence, reflectivity is a value that applies to thick reflecting objects whereas reflectance applies at a surface). I suggest we stick with what has already been done in standard names and therefore it would seem reasonable to introduce new names of toa_lambertian_equivalent_hemispherical_reflectance and toa_lambertian_equivalent_hemispherical_reflectance_multiplied_by_cosine_solar_zenith_angle. In the following I have given for comparison the original versions of the proposed names and definitions, and the suggested modifications. Would the modified versions be acceptable to you?
10a. Current status: Under discussion.
toa_lambertian_equivalent_albedo (canonical units: 1)
'Albedo is the ratio of the outgoing to the incoming power per unit area (irradiance). A coordinate variable of, respectively, radiation_wavelength or radiation_frequency can be used to specify the radiation wavelength or frequency. "toa" means top of atmosphere. "lambertian_equivalent" means the quantity is evaluated for a diffusely reflecting surface.'
OR
toa_lambertian_equivalent_hemispherical_reflectance (canonical units: 1)
'Reflectance is the ratio of the energy of the reflected to the incident radiation. Hemispherical reflectance means the quantity has been averaged over the reflected hemisphere. A coordinate variable of, respectively, radiation_wavelength or radiation_frequency can be used to specify the radiation wavelength or frequency. "toa" means top of atmosphere. "lambertian_equivalent" means the quantity is evaluated for a diffusely reflecting surface.'
10b. Current status: Under discussion.
toa_lambertian_equivalent_albedo_multiplied_by_cosine_solar_zenith_angle (canonical units: 1)
'Albedo is the ratio of the outgoing to the incoming power per unit area (irradiance). A coordinate variable of, respectively, radiation_wavelength or radiation_frequency can be used to specify the radiation wavelength or frequency. "toa" means top of atmosphere. "lambertian_equivalent" means the quantity is evaluated for a diffusely reflecting surface. "multiplied_by_cosine_solar_zenith_angle" means that the quantity has normalized to remove the angular dependence of the incoming shortwave irradiance.'
OR
toa_lambertian_equivalent_hemispherical_reflectance_multiplied_by_cosine_solar_zenith_angle (canonical units: 1)
'Reflectance is the ratio of the energy of the reflected to the incident radiation. Hemispherical reflectance means the quantity has been averaged over the reflected hemisphere. A coordinate variable of, respectively, radiation_wavelength or radiation_frequency can be used to specify the radiation wavelength or frequency. "toa" means top of atmosphere. "lambertian_equivalent" means the quantity is evaluated for a diffusely reflecting surface. "multiplied_by_cosine_solar_zenith_angle" means that the quantity has been normalized to remove the angular dependence of the incoming shortwave irradiance.'
11. Thread: "GOES-R generated binary mask products under proposal".
(
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056483.html)
11a. Additional threads: "standard name request for a satellite pixel-level cloud mask" (
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057257.html), "Status of cloud_binary_mask?" (
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2015/058108.html)
Current status: Accepted.
cloud_binary_mask (canonical units: 1)
' X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = cloud present, 0 = cloud absent (clear). If no threshold is supplied, the binary mask is 1 if there is any non-zero amount of cloud. if a threshold is supplied, it should be specified by associating a coordinate variable or scalar coordinate variable with the data variable and giving the coordinate variable a standard name of cloud_area_fraction. The values of the coordinate variable are the threshold values for the corresponding subarrays of the data variable.'
This name and definition were agreed in the original mailing list discussion. Subsequent requests for this quantity have also been made on the mailing list in the later threads. This name is accepted for publication in the standard name table.
11b. Current status: Under discussion.
smoke_binary_mask (canonical units: 1)
'X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = smoke present, 0 = smoke absent. If no threshold is supplied, the binary mask is 1 if there is any non-zero amount of smoke.'
We would require a definition for the term 'smoke' which is new to standard names. Clearly this is some sort of atmospheric aerosol but is it defined by, for example, size distribution, composition, proximity to fires, any other characteristics? For consistency with existing standard names (see also my comments in 11c and 11d) I suggest we modify the name itself to smoke_ambient_aerosol_particles_binary_mask. Do you agree?
The mailing list discussion on the binary mask names focused on including provision to specify a threshold for deciding whether cloud/smoke/dust/aerosol is present in a given scene. It was stated that, for GOES-R, the masks will be assigned a value of 1 if there is any presence of the phenomenon in question, detected by any one of a series of objective tests. However, it was agreed that in order to make the names more generally applicable we should include provision in the definitions for the use of a coordinate variable to specify a non-zero threshold, should it be needed. In the case of the cloud mask, the existing standard name cloud_area_fraction is suitable for such a coordinate variable. For smoke, dust and aerosol, the choice of coordinate variable is less obvious and we may even need to add new standard names to allow for this. Since GOES-R does not actually require a threshold, and currently we have no proposals for suitable coordinate variable names, I propose to add some text to the definitions
of the smoke/dust/aerosol masks suggested by
Jim Biard (
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056560.html): 'If a threshold is supplied, it may be specified by associating a coordinate variable or scalar coordinate variable with the data variable and giving the coordinate variable a standard name that specifies the quantity used for determining the threshold. The values of the coordinate variable are the threshold values for the corresponding subarrays of the data variable.' This neatly side steps the need to decide coordinate variable names now, but leaves the door open for them to be proposed in the future if another data provider does want to use these names with a non-zero threshold. Would you be happy with this approach?
11c. Current status: Under discussion.
dust_binary_mask (canonical units: 1)
'X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = dust present, 0 = dust absent. Note that if no threshold is supplied, the binary mask is 1 if there is any non-zero amount of dust.'
There are existing standard names for 'dust_dry_aerosol_particles' and 'dust_ambient_aerosol_particles'. For consistency, I would suggest modifying this name to dust_ambient_aerosol_particles_binary_mask (N.B. I am deliberately leaving 'particles' in the plural because that is what we already use. I am choosing 'ambient' rather than 'dry' because I assume that you are detecting all dust particles in the atmosphere, regardless of their state of hygroscopic growth). Is this OK? I note also that we do not appear to have any definition of 'dust' in the standard name table - it would be very useful if you could provide one.
Please see also my comments in 11b regarding provision in the definition for supplying a threshold.
11d. Current status: Under discussion.
aerosol_binary_mask (canonical units: 1)
'X_binary_mask has 1 where condition X is met, 0 elsewhere. 1 = aerosols present, 0 = aerosols absent. Note that if no threshold is supplied, the binary mask is 1 if there is any non-zero amount of aerosol.'
For consistency with existing names, I suggest that this name should be ambient_aerosol_particles_binary_mask (please see also my comments in 11b and 11c). Is this OK?
Charles Paxson, in the original mailing list thread, said that the GOES-R aerosol mask would be set to 1 if either smoke or dust were found to be present, so we should add that to the definition along with a cross-reference to the other mask names. Please see also my comments in 11b regarding provision in the definition for supplying a threshold.
12. Thread: "new standard name needed: toa_solar_irradiance_per_unit_wavelength"
(
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056448.html)
Current status: Under discussion.
toa_shortwave_irradiance_per_unit_wavelength (canonical units: W m-2 m-1)
' "toa" means top of atmosphere. "Shortwave" means shortwave radiation. Irradiance is the radiant power per unit area incident at a surface.'
This was discussed briefly on the mailing list and, at the time, did not excite any attention for the use of the word 'irradiance' rather than 'flux' unlike the recent discussions in the thread "New standard name requests for TSI and SSI" (
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2015/058115.html). However, in view of the more recent proposals I would like to check my understanding of this quantity.
We have just had a very detailed discussion of the following:
solar_irradiance_per_unit_wavelength (canonical units: W m-2 m-1)
' The quantity with standard name solar_irradiance_per_unit_wavelength, often called Solar Spectral Irradiance (SSI), is the radiation from the sun as a function of wavelength integrated over the entire solar disk. A coordinate variable for radiation wavelength should be given the standard name radiation_wavelength. The quantity applies outside the atmosphere, by default at a distance of one astronomical unit from the sun, but a coordinate or scalar coordinate variable of distance_from_sun can be used to specify a value other than the default. "Irradiance" means the power per unit area (called radiative flux in other standard names), the area being normal to the direction of flow of the radiant energy.'
This name has been agreed and accepted for publication in the standard name table.
On the face of it, the two names sound very similar. However, I suspect that the difference is regarding the "distance_from_sun". Am I correct in thinking that for the GOES-R name you are assuming a distance from the sun of whatever the earth-sun distance happens to be when the observation is made? (This is what I would infer from the use of "toa" in the name). Although the SSI name would allow you to specify a distance_from_sun that is not 1 AU, you would then need to supply a coordinate variable that presumably specified earth-sun distance. Would that be a problem for your data? If so, then we probably do need to introduce another name such as the toa one you are suggesting. I am keen to clarify this point as I have received an email from another CF user (offlist) asking whether it will always be necessary to specify a distance from the sun for the solar irradiance quantity - I have the impression that it could be an added complication for some users.
13. CF Trac Ticket #74 (Allow sharing of ancillary variables among multiple data variables)
(
http://cf-trac.llnl.gov/trac/ticket/74)
Two new standard names were proposed in this trac ticket discussion. The ticket has been agreed and will be implemented, I believe, in CF 1.7. Thus, these standard names can also be regarded as agreed.
Current status: Accepted.
status_flag (Canonical units: 1)
'A variable with the standard name of status_flag contains an indication of quality or other status of another data variable. The linkage between the data variable and the variable with the standard_name of status_flag is achieved using the ancillary_variables attribute.'
Current status: Accepted.
number_of_observations (Canonical units: 1)
'A variable with the standard name of number_of_observations contains the number of discrete observations or measurements from which the values of another data variable have been derived. The linkage between the data variable and the variable with a standard_name of number_of_observations is achieved using the ancillary_variables attribute.'
14. Thread: a question on standard_name "atmosphere_optical_thickness_due_to_cloud"
(
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2013/056423.html)
Current status: Accepted
A request was made to modify the definition for the existing name atmosphere_optical_thickness_due_to_cloud. I will add the sentence ' "Cloud" means the component of extinction owing to the presence of liquid or ice water particles' to the definition of this name, as requested by Randy.
15. Names already in the standard name table.
In a list of GOES-R names provided by Randy and Michael there was a reference to effective_radius_of_cloud_particle_at_cloud_top. This name was discussed on the list in 2013-14 and I recommended using the existing name effective_radius_of_cloud_condensed_water_particles_at_cloud_top. We briefly discussed amending the existing name but It was decided in the end that this wasn't necessary (
http://mailman.cgd.ucar.edu/pipermail/cf-metadata/2014/057118.html). I therefore continue to recommend use of the existing name in its present form.
Two further names that were proposed in relation to GOES-R, geopotential_height_at_volcanic_ash_cloud_top and atmosphere_mass_content_of_volcanic_ash, were added to the standard name table at Version 26.
16. Area types.
16a. Thread: "need additional area_types" and trac ticket 106.
Current status: Accepted.
The following five additions to the area type table were proposed to allow the calculation of statistics over portions of grid cells as described in the CF conventions section 7.3.3: fire; smoke; dust_aerosol; volcanic_ash_cloud; rain. These additions were all agreed during the discussion and they are now accepted for publication in the area type table.
16b. Thread: "new area type needed: snow_free_land"
Current status: Accepted.
The following addition to the standard name table was proposed and agreed: snow_free_land. This area type is now accepted for publication.
I hope these comments are useful and that we can soon agree those names that are still under discussion.
Best wishes,
Alison
------
Alison Pamment Tel: +44 1235 778065
Centre for Environmental Data Analysis Email: alison.pamment at stfc.ac.uk
STFC Rutherford Appleton Laboratory
R25, 2.22
Harwell Oxford, Didcot, OX11 0QX, U.K.
Received on Thu Jul 02 2015 - 08:09:31 BST
