Dear Philip, John, and all, after discussing this issue also offline with a few peers, and including the comments of Philip and John, I think I can propose a solution:
The original problem: CF aerosol variable names so far use the terms "_due_to_ambient_aerosol" and "due_to_dry_aerosol". For variables with "_due_to_ambient_aerosol", a co-ordinate variable relative_humidity is required since most aerosol properties are strongly dependent on particle humidification, and not taking this effect into account would render any model-observation comparison meaningless. The observations of surface aerosol optical properties I'm concerned with are intended to be on the dry aerosol. In some locations however (e.g. in the tropics), sample drying can be incomplete at times, leaving the sample in a state between ambient and dry. In practice, these data would be used for comparisons in the same way as those with "_due_to_ambient_aerosol", where the humidity state needs to be taken into account, except that the humidity is neither ambient nor dry. The proposed solution: I propose to introduce "_due_to_dried_aerosol" as third term besides "_due_to_ambient_aerosol" and "due_to_dry_aerosol". The definitions using this term would say that a drying procedure has been applied to the sample, but that the dry aerosol state (RH < 40%) may or may not have been reached completely. I asked a few English native speakers, and most of them said this definition was what they thought when hearing the term, even without knowing the definition. Using "_due_to_dried_aerosol" would require a co-ordinate variable "relative_humidity". The term "_due_to_dried_aerosol" has the advantage of conveying how the measurement was obtained while being comparatively short. The term should also transport the information that Philip and John intended with their proposed solutions. Below, you find a complete updated list of the standard names I proposed, including definitions. Even though I'm happy about further comments on the proposal, I think we are close to a conclusion of this discussion, and I would like to thank all discussion participants for their contributions so far! Best regards, Markus --------------------------------------------------------------------------- Updated list of proposed standard names (2012-03-21) 1) volume_scattering_coefficient_in_air_due_to_dry_aerosol The volume scattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 2) volume_absorption_coefficient_in_air_due_to_dry_aerosol The volume absorption coefficient is the fractional change of radiative flux per unit path length due to absorption of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 3) volume_spherical_backscattering_coefficient_in_air_due_to_dry_aerosol The volume spherical backscattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam into the rearward hemisphere relative to the incident beam by a component in the reference volume. It is distinct from the backscattering coefficient which isn't integrated over the rearward hemisphere. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. A coordinate variable of radiation_wavelengt h or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 4) surface_volume_scattering_coefficient_at_stp_in_air_due_to_pm1_dry_aerosol The volume scattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm1" refers to the fraction of aerosol particles with an aero dynamic diameter of less than or equal to 1 micrometer, where the size cut is applied under ambient conditions before the aerosol is dried. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 5) surface_volume_scattering_coefficient_at_stp_in_air_due_to_pm10_dry_aerosol The volume scattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm10" refers to the fraction of aerosol particles with an aer odynamic diameter of less than or equal to 10 micrometers, where the size cut is applied under ambient conditions before the aerosol is dried. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 6) surface_volume_absorption_coefficient_at_stp_in_air_due_to_pm1_dry_aerosol The volume absorption coefficient is the fractional change of radiative flux per unit path length due to absorption of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm1" refers to the fraction of aerosol particles with an aerod ynamic diameter of less than or equal to 1 micrometers, where the size cut is applied under ambient conditions before the aerosol is dried. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 7) surface_volume_absorption_coefficient_at_stp_in_air_due_to_pm10_dry_aerosol The volume absorption coefficient is the fractional change of radiative flux per unit path length due to absorption of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm10" refers to the fraction of aerosol particles with an aero dynamic diameter of less than or equal to 10 micrometers, where the size cut is applied under ambient conditions before the aerosol is dried. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 8) surface_volume_spherical_backscattering_coefficient_at_stp_in_air_due_to_pm1_dry_aerosol The volume spherical backscattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam into the rearward hemisphere relative to the incident beam by a component in the reference volume. It is distinct from the backscattering coefficient which isn't integrated over the rearward hemisphere. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. "surface" means the lower boundary of the at mosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm1" refers to the fraction of aerosol particles with an aerodynamic diameter of less than or equal to 1 micrometers, where the size cut is applied under ambient conditions before the aerosol is dried. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 9) surface_volume_spherical_backscattering_coefficient_at_stp_in_air_due_to_pm10_dry_aerosol The volume spherical backscattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam into the rearward hemisphere relative to the incident beam by a component in the reference volume. It is distinct from the backscattering coefficient which isn't integrated over the rearward hemisphere. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). Aerosol takes up ambient water (a process known as hygroscopic growth) depending on the relative humidity and the composition of the aerosol. "Dry aerosol" means aerosol fully dehydrated from its ambient state, which in practice often means brought to a relative humidity less than 40%. 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. "surface" means the lower boundary of the at mosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm10" refers to the fraction of aerosol particles with an aerodynamic diameter of less than or equal to 10 micrometers, where the size cut is applied under ambient conditions before the aerosol is dried. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 10) volume_scattering_coefficient_in_air_due_to_dried_aerosol The volume scattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 11) volume_absorption_coefficient_in_air_due_to_dried_aerosol The volume absorption coefficient is the fractional change of radiative flux per unit path length due to absorption of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 12) volume_spherical_backscattering_coefficient_in_air_due_to_dried_aerosol The volume spherical backscattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam into the rearward hemisphere relative to the incident beam by a component in the reference volume. It is distinct from the backscattering coefficient which isn't integrated over the rearward hemisphere. "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 13) surface_volume_scattering_coefficient_at_stp_in_air_due_to_pm1_dried_aerosol The volume scattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm1" refers to the fraction of aerosol particles w ith an aerodynamic diameter of less than or equal to 1 micrometer, where the size cut is applied under ambient conditions before aerosol humidity, pressure, or temperature are possibly altered. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 14) surface_volume_scattering_coefficient_at_stp_in_air_due_to_pm10_dried_aerosol The volume scattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm10" refers to the fraction of aerosol particles with an aerodynamic diameter of less than or equal to 10 micrometers, where the size cut is applied under ambient conditions before aerosol humidity, pressure, or temperature are possibly altered. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 15) surface_volume_absorption_coefficient_at_stp_in_air_due_to_pm1_dried_aerosol The volume absorption coefficient is the fractional change of radiative flux per unit path length due to absorption of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm1" refers to the fraction of aerosol particles wi th an aerodynamic diameter of less than or equal to 1 micrometers, where the size cut is applied under ambient conditions before aerosol humidity, pressure, or temperature are possibly altered. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 16) surface_volume_absorption_coefficient_at_stp_in_air_due_to_pm10_dried_aerosol The volume absorption coefficient is the fractional change of radiative flux per unit path length due to absorption of an incident light beam by a component in the reference volume. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. "surface" means the lower boundary of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm10" refers to the fraction of aerosol particles w ith an aerodynamic diameter of less than or equal to 10 micrometers, where the size cut is applied under ambient conditions before aerosol humidity, pressure, or temperature are possibly altered. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 17) surface_volume_spherical_backscattering_coefficient_at_stp_in_air_due_to_pm1_dried_aerosol The volume spherical backscattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam into the rearward hemisphere relative to the incident beam by a component in the reference volume. It is distinct from the backscattering coefficient which isn't integrated over the rearward hemisphere. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. "surface" means the lower boundar y of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm1" refers to the fraction of aerosol particles with an aerodynamic diameter of less than or equal to 1 micrometers, where the size cut is applied under ambient conditions before aerosol humidity, pressure, or temperature are possibly altered. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. 18) surface_volume_spherical_backscattering_coefficient_at_stp_in_air_due_to_pm10_dried_aerosol The volume spherical backscattering coefficient is the fractional change of radiative flux per unit path length due to redirection of an incident light beam into the rearward hemisphere relative to the incident beam by a component in the reference volume. It is distinct from the backscattering coefficient which isn't integrated over the rearward hemisphere. "Aerosol" means the suspended liquid or solid particles in air (except cloud droplets). "Dried_aerosol" means that the aerosol sample has been dried from the ambient state, but that the dry state (RH < 40%) hasn't necessarily been reached. To specify the relative humidity at which the property applies, provide scalar coordinate variable with the standard name of "relative_humidity". 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. "surface" means the lower boundar y of the atmosphere. "at_stp" refers to a volume at standard conditions of temperature (273.15 K) and pressure (1013.25 hPa). "pm10" refers to the fraction of aerosol particles with an aerodynamic diameter of less than or equal to 10 micrometers, where the size cut is applied under ambient conditions before aerosol humidity, pressure, or temperature are possibly altered. A coordinate variable of radiation_wavelength or radiation_frequency needs to be specified to indicate that the property applies at specific wavelengths or frequencies. _______________________________________ Dr. Markus Fiebig Dept. Atmospheric and Climate Research (ATMOS) Norwegian Institute for Air Research (NILU) P.O. Box 100 N-2027 Kjeller Norway Tel.: +47 6389-8235 Fax : +47 6389-8050 e-mail: [email protected] skype: markus.fiebig _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
