Hi Jonathan, thanks for your input!
I put my replies to your comments inline below: -----Original Message----- From: CF-metadata [mailto:[email protected]] On Behalf Of Jonathan Gregory Sent: Sonntag, 13. Oktober 2013 10:46 To: [email protected] Subject: [CF-metadata] standard names for surface aerosol optical properties 1) "surface_particle_number_concentration_at_stp_in_aerosol (and other similar names). Could this be said more clearly as surface_number_concentration_of_aerosol_in_air_at_stp? That would be consistent with existing names e.g. number_concentration_of_coarse_mode_ambient_aerosol_in_air" The standard names I proposed use the term "aerosol" according to its proper textbook definition, i.e. meaning the system of particles and carrier gas. Your wording implies that "aerosol" consists of particles only, which is a common, but colloquial jargon use of the term. I respect the use of "aerosol" in standard names so far, so I worded the proposed names to be backward compatible. 2) You draw attention to the inclusion of "surface" in the above, but I'm not clear why it's there. Is the measurement actually exactly at the ground? If not, surface should be omitted, and the height indicated by a numerical coordinate, or some other phrase e.g. in_atmosphere_boundary_layer (that one already appears in the stdname table). The term "surface" is used according to the description given in the "Guidelines for Construction of CF Standard Names" at http://cf-pcmdi.llnl.gov/documents/cf-standard-names/guidelines It is a qualifier of type surface that has the value "surface". This qualifier may be stated at the begin of the standard name, or added with the "_at" proposition ("_at_surface"). The standard names I'm proposing are intended to be used for data measured at GAW ground stations, where the sample inlet is typically located 4-5 meters above ground. For most (model) users except boundary layer and microscale models, i.e. climate models, CTMs, etc., this is pretty much the same as "surface", i.e. interface between atmosphere and ground. You just don't get much closer to "surface" than this. I included this qualifier also because these names are to be used independently of a file, i.e. in data portals intended for data discovery linking to the primary data archives. For this use case, it's highly valuable that the standard name states clearly what's in the file without in fact opening it. I would see 2 options for modifying the standard names to accommodate your concerns: 1) State the "surface" qualifier not at the begin of the standard name, but use the "_at" version. 2) Include in the definition the requirement that the sampling height needs to be included as numerical coordinate. 3) Clouds do not usually occur at the surface, so "surface" is surprising for CCN. Not really. The number of cloud condensation nuclei active at a given water vapour supersaturation is independent of the actual existence of a cloud. The instrument measuring this property exposes the aerosol particles to a generated, defined supersaturation, i.e. generates its own "cloud" inside the instrument. 4) electrical_mobility_particle_diameter. I think the "electrical" here refers to the means of measurement. Usually the CF standard name describes the geophysical quantity itself. Would it be OK to say aerosol_particle_diameter? The electrical mobility particle diameter is one of many aerosol particle diameters, as opposed to for example the aerodynamic particle diameter (how a particle follows a streamline) or the optical particle diameter (how the particle scatters light). By only saying "aerosol particle diameter", the property is somewhat ill-defined since most aerosol particles aren't spherical. The proposed name avoids this ambiguity. 5) sizing_relative_humidity. Could "sizing" be omitted? The definition of your standard names can specify what the role of the RH is. This standard name would be used together with reporting particle size resolved CCN concentrations, i.e. CCN concentrations as function of both, supersaturation and dry particle size. In this context, we need to distinguish between the RH for which the CCN concentration is measured (a few 10ths above 100%), and the RH at which the particle size is selected (usually below or just above 40%). I couldn't find any other way of distinguishing this easily except defining a separate standard name. Best regards, Markus _______________________________________ Dr. Markus Fiebig Senior Scientist 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 P Please consider the environment before printing this email and attachments _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
