Dear Martin, Karl and Steve, Thank you for the proposing these two names and the comments received so far.
fraction_of_rainfall_mass_falling_onto_surface_snow (1) 'The phrase "surface_snow" means snow lying on the surface.' fraction_of_solid_precipitation_mass_falling_onto_surface_snow (1) 'The phrase "surface_snow" means snow lying on the surface. Solid precipitation refers to the precipitation of water in the solid phase. Water in the atmosphere exists in one of three phases: solid, liquid or vapor. The solid phase can exist as snow, hail, graupel, cloud ice, or as a component of aerosol.' The names and units look fine. Are these variables calculated over quite large areas? If so, would it be appropriate to add the following sentence to their definitions: 'The horizontal domain over which the quantity is calculated is described by the associated coordinate variables and coordinate bounds or by a coordinate variable or scalar coordinate variable with the standard name of "region" supplied according to section 6.1.1 of the CF conventions'? This is what we do with names like land_ice_mass where the quantity might represent the mass of a whole ice sheet, rather than something calculated in a small lat-long grid box. Best wishes, Alison ------ Alison Pamment Tel: +44 1235 778065 NCAS/Centre for Environmental Data Archival Email: [email protected] STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Oxford, Didcot, OX11 0QX, U.K. From: CF-metadata <[email protected]> On Behalf Of Karl Taylor Sent: 05 June 2018 17:03 To: Steven Emmerson <[email protected]>; Juckes, Martin (STFC,RAL,RALSP) <[email protected]> Cc: [email protected] Subject: Re: [CF-metadata] Precipitation fractions for LS3MIP Hi all, I think in common usage "mass fraction" is the ratio of the mass of a particular species to the total mass of all species combined (e.g., the mass fraction of oxygen molecules in air). For the variable considered here, the fraction refers to the ratio of the mass of as particular "species" (e.g., rain) that falls on a particular surface (e.g., surface snow). This is enough different from the standard usage that I think it would be wise to avoid "mass fraction" in the standard name; thus, the suggestion: fraction_of_rainfall_mass_falling_onto_surface_snow Using "mass_fraction" here might lead some to wrongly jump to an interpretation that this had something to do with the fraction of precipitation that was falling as rain. best regards, Karl On 6/5/18 7:55 AM, Steven Emmerson wrote: Greetings, On Tue, Jun 5, 2018 at 3:31 AM, Martin Juckes - UKRI STFC <mailto:[email protected]> wrote: We don't want the mass per unit area on snow divided by the mass per unit area on the whole grid cell, but rather, as Jonathan has spelled out, the mass on snow divided by the mass on the whole grid cell. Hence, I support Karl's suggestion of using "mass" in the name, rather than "amount". I believe that's called a "mass fraction". See Table 12 of <https://www.nist.gov/pml/nist-guide-si-chapter-8-comments-some-quantities-and-their-units>. Regards, Steve Emmerson _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
