Hello Roy, maybe .. but I was talking about the current definition of the CF standard name "solar_irradiance", which, currently, has nothing to do with the vertical,
regards, Martin ________________________________ From: Lowry, Roy K. [r...@bodc.ac.uk] Sent: 26 January 2018 20:35 To: Juckes, Martin (STFC,RAL,RALSP); cf-metadata@cgd.ucar.edu Subject: Re: Definiton of solar_irradiance Hello Martin, Isn't that was what cosine collectors on radiometers are for? I thought they resolved the vertical component of the radiation within the hemisphere sampled. Cheers, Roy. Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquir...@bodc.ac.uk. Please also use this e-mail if your requirement is urgent. ________________________________ From: martin.juc...@stfc.ac.uk <martin.juc...@stfc.ac.uk> Sent: 26 January 2018 19:15 To: Lowry, Roy K.; cf-metadata@cgd.ucar.edu Subject: RE: Definiton of solar_irradiance Hello Roy, but the flow of radiant energy isn't necessarily perpendicular to the surface of the Earth. At the top of the atmosphere the flow of energy will generally be along a ray from the Sun. If you want it to be the irradiance on a horizontal surface you really need to take out the bit about being perpendicular to the flow of energy. You can't make the name work for horizontal surfaces without contradicting the assertion in the current definition that it applies to TSI, regards, Martin ________________________________ From: Lowry, Roy K. [r...@bodc.ac.uk] Sent: 26 January 2018 17:46 To: Juckes, Martin (STFC,RAL,RALSP); cf-metadata@cgd.ucar.edu Subject: Re: Definiton of solar_irradiance Hello again, What we map to the 'solar_irradiance' Standard name are parameters such as 'Downwelling vector irradiance as energy of electromagnetic radiation (solar wavelengths) in the atmosphere by pyranometer'. So in the use case I was thinking of it's both a horizontal surface and a surface perpendicular to the direction of flow of the radiant energy i.e. we have made an assumption the the direction of flow of the radiant energy is perpendicular to the Earth's surface. Consequently, I would amend the definition as below rather than redefining from scratch with the risk you pointed out of changing the semantics of existing data sets. "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. The area is a horizontal surface for radiant energy flowing perpendicular to the Earth's surface. Cheers, Roy. Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquir...@bodc.ac.uk. Please also use this e-mail if your requirement is urgent. ________________________________ From: martin.juc...@stfc.ac.uk <martin.juc...@stfc.ac.uk> Sent: 26 January 2018 16:52 To: Lowry, Roy K.; cf-metadata@cgd.ucar.edu Subject: RE: Definiton of solar_irradiance Dear Roy, If we were starting from scratch I would recommend the following: Solar irradiance is the power per unit area of the solar radiation received from above at horizontal surface. It is distinct from the Direct Normal Irradiance (which refers to radiation received by a surface perpendicular to rays travelling from the sun) and the Total Solar Irradiance (which is the mean value of Direct Normal Irradiance at a standard distance from the sun). I am, however, concerned that people may have already, on the basis of the current definition, used the term for Total Solar Irradiance. regards, Martin ________________________________________ From: Lowry, Roy K. [r...@bodc.ac.uk] Sent: 26 January 2018 16:03 To: Juckes, Martin (STFC,RAL,RALSP); cf-metadata@cgd.ucar.edu Subject: Re: Definiton of solar_irradiance Dear Martin, I agree that the current definition reflects more an astrophysics textbook rather than common usage of the Standard Name and so I would support tweaking the wording as you suggest. Care to come up with the replacement wording to be used? Cheers, Roy. Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquir...@bodc.ac.uk. Please also use this e-mail if your requirement is urgent. ________________________________ From: martin.juc...@stfc.ac.uk <martin.juc...@stfc.ac.uk> Sent: 26 January 2018 15:57 To: Lowry, Roy K.; cf-metadata@cgd.ucar.edu Subject: RE: Definiton of solar_irradiance Hello Roy, I suspected that there might be such a usage ... but don't you agree that the current CF definition, which I've quoted below, is inconsistent with this? But it could be adapted with a small change of wording, regards, Martin ________________________________ From: Lowry, Roy K. [r...@bodc.ac.uk] Sent: 26 January 2018 15:51 To: Juckes, Martin (STFC,RAL,RALSP); cf-metadata@cgd.ucar.edu Subject: Re: Definiton of solar_irradiance Hello Martin, >From an oceanographic perspective I had always thought of solar (and other >waveband) irradiance as the energy incident on the sea surface, which is a >horizontal surface. So, I would like to think of solar_irradiance as being >horizontal_solar_irradiance and if any new Standard Name is required to cover >the current Vaisala instrumentation use case then that should be >normal_standard_irradiance. Cheers, Roy. Please note that I partially retired on 01/11/2015. I am now only working 7.5 hours a week and can only guarantee e-mail response on Wednesdays, my day in the office. All vocabulary queries should be sent to enquir...@bodc.ac.uk. Please also use this e-mail if your requirement is urgent. ________________________________ From: CF-metadata <cf-metadata-boun...@cgd.ucar.edu> on behalf of martin.juc...@stfc.ac.uk <martin.juc...@stfc.ac.uk> Sent: 26 January 2018 13:37 To: cf-metadata@cgd.ucar.edu Subject: [CF-metadata] Definiton of solar_irradiance Hello, the cf standard name has a definition: The quantity with standard name solar_irradiance, often called Total Solar Irradiance (TSI), is the radiation from the sun integrated over the whole electromagnetic spectrum and over the entire solar disk. 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. My question is about the last phrase, which I have highlighted. The flow of radiant energy from the sun at the top of the atmosphere is directed away from the sun .. so this definition would imply that the irradiance is defined relative to a fixed plane in the solar coordinate system. This is OK for solar physicists, but atmospheric scientists are sometime interested in irradiance relative to a horizontal surface. Vaisalla distinguish between the two by defining "horizontal solar irradiance" to be the irradiance on a horizontal surface and "normal solar irradiance" to be irradiance on a surface perpendicular to a line to the sun (<UrlBlockedError.aspx>http://www.3tier.com/en/support/solar-online-tools/what-solar-values-are-shown-map/ ). Should "solar_irradiance" apply to both usages, or do we need a new standard name, e.g. "horizonatl_solar_irradiance"? regards, Martin _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata CF-metadata Info Page - mailman.cgd.ucar.edu Mailing Lists<http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata> mailman.cgd.ucar.edu This is an unmoderated list for discussions about interpretation, clarification, and proposals for extensions or change to the CF conventions. 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