Dear John and Roy, Thanks for your comments. Based on the explanations you have provided I suggest that the wording of the definition should be 'Turbidity is a dimensionless quantity which is expressed in NTU (Nephelometric Turbidity Units), which are normally given as 1e-3 or 0.001 i.e. parts per thousand. Turbidity expressed in NTU is the proportion of white light scattered back to a transceiver by the particulate load in a body of water, represented on an arbitrary scale referenced against measurements made in the laboratory on aqueous suspensions of formazine beads. Sea water turbidity may also be measured by the quantity with standard name secchi_depth_of_sea_water.'
I suggest also that we could improve the definition of the secchi_depth name to make it clearer that the quantity relates to turbidity and add a cross-reference to the new name: secchi_depth_of_sea_water - ' Depth is the vertical distance below the surface. A Secchi disk is a patterned disk that is used to measure water transparency, also called turbidity, in oceans and lakes. The disk is lowered into the water and the depth at which the pattern is no longer visible is the called the secchi depth. Sea water turbidity may also be measured by the quantity with standard name sea_water_turbidity.' Do you agree? Best wishes, Alison ------ Alison Pamment Tel: +44 1235 778065 NCAS/British Atmospheric Data Centre Email: [email protected] STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Oxford, Didcot, OX11 0QX, U.K. From: CF-metadata [mailto:[email protected]] On Behalf Of John Maurer Sent: 05 March 2013 00:23 To: [email protected] Subject: [CF-metadata] sea_water_turbidity Yes, I agree with Roy's assessment. Thank you. Cheers, John Date: Wed, 27 Feb 2013 21:19:01 +0000 From: "Lowry, Roy K." <[email protected]> To: "[email protected]" <[email protected]>, "[email protected]" <[email protected]> Subject: Re: [CF-metadata] sea_water_turbidity? Message-ID: <40829b0e077c1145a6de44d39b3830a922989bd...@nerckwmb1.ad.nerc.ac.uk> Content-Type: text/plain; charset="Windows-1252" Hello Alison, I had been hanging back waiting for John to respond to Jonathan's comment, because nephelometric turbidity is a phenomenon that I've seen described - but not necessarily defined - in a couple of different ways. However, whilst both turbidity and secchi disk depth (and attenuance to the matter) have values related to the SPM load in the water body, they differ markedly for a given SPM load and so I think a new standard name is justified. As a prompt, I'll give one of my understandings of turbidity in NTU, which is 'The proportion of white light scattered back to the transceiver by the particulate load in a body of water, represented on an arbitrary scale referenced against measurements made in the laboratory on aqueous suspensions of formazine beads.' Before going any further we need John to either confirm that this is what he means or come up with an alternative. Others might also have their own ideas.... Cheers, Roy. ______________________________ __________ From: CF-metadata [[email protected]] On Behalf Of [email protected] [[email protected]] Sent: 27 February 2013 14:04 To: [email protected] Subject: Re: [CF-metadata] sea_water_turbidity? Dear John, Thank you for your proposal. We currently have one existing standard name relating to turbidity of sea water, secchi_depth_of_sea_water, which has units of metres and is defined as ?Depth is the vertical distance below the surface. A Secchi disk is a patterned disk that is used to measure water transparency in oceans and lakes. The disk is lowered into the water and the depth at which the pattern is no longer visible is the called the secchi depth.? I agree with Jonathan that it would be helpful if you could provide a (fairly brief) definition for the new name or perhaps a suitable reference. Best wishes, Alison ------ Alison Pamment Tel: +44 1235 778065 NCAS/British Atmospheric Data Centre Email: [email protected]<mailto:[email protected]> STFC Rutherford Appleton Laboratory R25, 2.22 Harwell Oxford, Didcot, OX11 0QX, U.K. From: CF-metadata [mailto:[email protected]] On Behalf Of John Maurer Sent: 21 February 2013 00:52 To: [email protected] Subject: [CF-metadata] sea_water_turbidity? Dear CF-Metadata, I would propose the addition of "sea_water_turbidity" to the CF Standard Names. This has units of NTU (Nephelometric Turbidity Units), which would be represented in UDUNITS as "1e-3" (similar to how sea_water_salinity is in PSS (or PSU) and commonly represented as 1e-3). Thanks, John Maurer Data System Administrator Pacific Islands Ocean Observing System (PacIOOS) University of Hawaii at Manoa -- Scanned by iCritical. _______________________________________________ CF-metadata mailing list [email protected] http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
