Dear All,
Reporting the intake depth is one thing, but as we all know this isn't the depth of measurement. But the surface of the sea isn't always flat and ships tend to bounce around a bit, making measurment depth more of a range than a value! However, as Shawn says this is an area where it's maybe best not to go and we should use the inlet depth or vertical offset of the hull sensor relative to some datum (we usually take the central mark on the Plimsoll Line - ship loading is also a factor!!). However, I strongly endorse the approach of keeping the depth of measurement away from the Standard Name having learned from past experience with BODC parameter markup and as John and Shawn say depth and other issues should be handled by storing in a structured form as much relevant information as we can acquire.
The question we need to address is 'How many distinct phenomena do we want to describe through Standard Names?'. In CF, we have 'sea_water_temperature', 'sea_surface_temperature' and 'surface temperature'. The definition for 'sea_surface_temperature' is:
'Sea surface temperature is usually abbreviated as 'SST'. It is the temperature of sea water near the surface (including the part under sea-ice, if any), and not the skin temperature, whose standard name is surface_temperature. For the temperature of sea water at a particular depth or layer, a data variable of sea_water_temperature with a vertical coordinate axis should be used.'
Thus we have something that maps directly to GHRSST-PP SSTdepth (sea_surface_temperature) and SSTfnd (sea_water_temperature) and (maybe more controversially) SSTint (surface_temperature). To date, my understanding is that CF has not encountered storage of radiometer data or storage of model data with a vertical resolution on centimetric let alone micrometric scale. If we are to move into covering these areas, particularly radiometer data then I feel it is essential that we move into line with GHRSST-PP and add standard names 'sea_skin_temperature' and 'sea_subskin_temperature'.
Whether we use 'sea_water_temperature' or 'sea_surface_temperature' for TSG and in particular near-surface CTD data is a different issue that I don't want to open up here. BODC, Nan and I suspect many other observational oceanographers use 'sea_water_temperature'. The importnat thing is we realise this and make sure that our discovery/data handling agents take this into account.
When it comes to 'raw' TSG housing temperatures in CF my gut preference would be not to have a Standard Name, but as oceanographic CF implementations have made Standard Names mandatory we need to have something set up along the lines of what we did for Nan and oxygen. My suggestion would be:
'Temperature_of_sensor_for_conductivity_in_sea_water'
but maybe we should start this up as a separate thread?
Cheers, Roy.
>>> "Craig Donlon" <craig.donlon at gmail.com> 8/15/2007 7:12:07 pm >>>
Hi Derrick:
If you are intending to report data then the WMO Ship Observing Team
adopted the GHRSST-PP SST definitions. In tis case, your TSG data
would be reported as SST at depth using an attribute to specifiy the
depth of the TSG water intake. As a physical contact themometer
measurement, you are always going to be reporting SST depth and that
should be at the intake depth. The issue of warming within the ship
is a separate one form this debate and one that each installation
should try and minimise. Shawn Smith can assist you in thee issues.
If there is no depth reported with the SST the data are considerably
less useful especially for ocean modelling as the number of model
levels in the upper ocean is generally increasing as computing power
increases (and for air-sea interactionarehave his resolution in the
vertical)
Regards,
Craig
On 8/15/07, Derrick.Snowden at noaa.gov <Derrick.Snowden at noaa.gov> wrote:
> Dear all,
>
> I'm not in a position to weigh in on the debate or propose solutions but I do have a question as one project I work on seems related to this thread. This project is NOAA's Thermosalinograph program and in this program we aim to install TSGs on commercial vessels as well as provide the data management support for TSG data from the NOAA research fleet. My question is basically how TSG data figures in to this discussion and how we should refer to it in our exchange formats. (CF or COARDS compliant netcdf is likely to be adopted by the international committee concerned with exchange of TSG data)
>
> In principle temperature from a TSG shout every ship. It's possible that the fluid will flow through pipes in the engine room for a minuld probably be reported as SSTz but the z is debatable. For example, most ships have seawater intake pipes between 3-20m but the location of the TSG relative to the intake differs on almoste before reaching the sensor, during which time it is usually heating. To address this issue, we've begun installing remote temperature sensors designed to be nearer to the intake. This lessens but doesn't remove the problem of defining a depth for the SST measurement. Further, in cases where the remote sensor exists, we have two temperature measurements on each ship both of which must be kept in archives. The local temperature at the TSG is used for the determination of salinity from conductivity and the remote temperature seems more relevant to studying the physics of the ocean.
>
> I should mention that GOSUD, the Global Ocean Surface Underway Data committee is dealing with metadata issues, but GOSUD has not really made a determination about issues pertinent to CF, so far as I know. Does anyone care to comment on this? I'd love to hear any guidance you can give.
>
> Best
> Derrick
>
>
>
> ----- Original Message -----
> From: Karl Taylor <taylor13 at llnl.gov>
> Date: Wednesday, August 15, 2007 11:22 am
> Subject: Re: [CF-metadata] CF-1.0 registration of new names for SST
>
> > Dear all,
> >
> > It is my understanding that in coupled models of the atmosphere-
> > ocean
> > system the surface heat fluxes (at least sensible heat and upward
> > longwave radiation) require some estimate of "skin temperature"
> > because
> > the skin temperature is seen by the physics. It is true that this
> > is
> > not the same as the measured "sea surface temperature," which
> > Jonathan
> > notes is usually obtained by bucket or measurement of the near-
> > surface
> > water taken in by ships to cool their engines.
> >
> > For the CMIP3 database of model output used in preparation of the
> > IPCC
> > Fourth Assessment Report, we asked groups to report the "skin
> > temperature", and we labeled it with the standard name
> > "surface_temperature".
> >
> > We also requested "sea_surface_temperature", and I think (but am
> > not
> > positive) that we got different things from different groups. Some
> > sent
> > "skin temperature" (i.e., surface_temperature) in regions free of
> > sea
> > ice, and under sea ice, the temperature of the water in contact
> > with the
> > ice. Others probably simply sent the temperature of the upper-most
> > layer of their model. In either case this would differ from
> > "surface_temperature" at least in regions of sea ice.
> >
> > [By the way, I don't think the temperature seen by the heat flux
> > physics
> > over the ocean is invariably the mixed layer or first layer
> > temperature.
> > I know for a fact that for some land models and some sea-ice
> > models,
> > the surface temperature is not identical to the temperature of the
> > uppermost land or ice layer.]
> >
> > Best wishes,
> > Karl
> >
> >
> >
> >
> >
> >
> >
> > Heinke Hoeck wrote:
> > > Dear all,
> > >
> > > I have talked to the people who are working with ocean models and
> > > asked for a definition of SST from the modellers viewpoint.
> > > They think it doesn't exist. In the modeL world SST is the
> > temperature of
> > > the first layer or the 'mixed layer' if the mixed layer exists in
> > the model.
> > >
> > > So, the problem is, that we have the CF-Name sea_surface_temperature
> > > but not a definition. What does mean 'near' the surface ?
> > >
> > > I agree with Alison, that sea temperature depending on different
> > > physical processes should have there own standard names like
> > > sea_surface_temperature_in_subskin_layer
> > > sea_surface_temperature_in_skin_layer...
> > >
> > > or
> > >
> > > SSTsubskin
> > > SSTskin...
> > >
> > > --It will be very, very difficult to change many of the
> > > --names for GHRSST-PP now but of course, this can be done with
> > effort.>
> > >
> > > The 'CF Controlled Vocabulary' could be a solution of this problem.
> > > See Frank Toussaint's email with subject 'CF Controlled Vocabulary'.
> > >
> > > Best wishes
> > > Heinke
> > >
> > >
> > > Heinke H?ck
> > > Max-Planck-Institut fuer Meteorologie Tel +49 40 41173-465
> > > Abteilung Modelle und Daten Fax +49 40 41173-400
> > > Bundesstr. 53
> > > D-20146 Hamburg Germany
> > > Email: heinke.hoeck at zmaw.de
> > > http://www.mad.zmaw.de/
> > >
> > > Craig Donlon wrote:
> > >> Hi Alison:
> > >>
> > >> (Ken and JF, the thread can be picked up here:
> > >> http://mailman.cgd.ucar.edu/pipermail/cf-
> > metadata/2007/date.html#1609)>>
> > >> I missed your mail and the subsequent threads for some reason - the
> > >> most up to date entries I have are from the recent message sent
> > by Nan
> > >> (thanks Nan!). So I'll try and cover the details as best I can for
> > >> all concerned.
> > >>
> > >> All of the names that are being proposed have been the subject of
> > >> great debate within the GHRSST-PP community and are the result
> > of long
> > >> discussions at several international meetings. The names are
> > used for
> > >> every data set produced by GHRSST-PP every day 24/7 and as the
> > >> GHRSST-PP uses netCDF (and tries to be CF-1.0 Compliant) it was
> > >> appropriate to try and obtain ratification for the long and
> > standard>> names proposed. It will be very, very difficult to
> > change many of the
> > >> names for GHRSST-PP now but of course, this can be done with
> > effort.>>
> > >> For the benefit of everyone concerned, here are the full
> > definitions>> (reported in Donlon et al., J Climate 2002 and
> > updated and reported in
> > >> BAMS this August). The following is taken from
> > >> https://www.ghrsst-pp.org/SST-Definitions.html
> > >>
> > >>
> > >> SST is a difficult parameter to define exactly because the upper
> > ocean>> (~10 m) has a complex and variable vertical temperature
> > structure that
> > >> is related to ocean turbulence and the air-sea fluxes of heat,
> > >> moisture and momentum. A framework is required to understand the
> > >> information content and relationships between measurements of
> > SST made
> > >> by different satellite and in situ instruments, especially if these
> > >> are to be merged together. The definitions of SST developed by the
> > >> GHRSST-PP SST Science Team (agreed at the 2nd and 3rd GHRSST-PP
> > >> workshops) achieve the closest possible coincidence between what is
> > >> defined and what can be measured operationally, bearing in mind
> > >> current scientific knowledge and understanding of how the near
> > surface>> thermal structure of the ocean behaves in nature.
> > >>
> > >> The interface temperature (SSTint)
> > >> At the exact air-sea interface a hypothetical temperature called
> > the>> interface temperature (SSTint) is defined although this is of no
> > >> practical use because it cannot be measured using current
> > technology.>> (NOTE- this is probably not required but was included
> > for>> completeness)
> > >> [Proposed CF-names: SSTint, interface_SST,
> > interface_sea_surface_temperature]>>
> > >> The skin sea surface temperature (SSTskin)
> > >> The skin temperature (SSTskin) is defined as the temperature
> > measured>> by an infrared radiometer typically operating at
> > wavelengths 3.7-12 ?m
> > >> (chosen for consistency with the majority of infrared satellite
> > >> measurements) that represents the temperature within the conductive
> > >> diffusion-dominated sub-layer at a depth of ~10-20 ?m. SSTskin
> > >> measurements are subject to a large potential diurnal cycle
> > including>> cool skin layer effects (especially at night under
> > clear skies and low
> > >> wind speed conditions) and warm layer effects in the daytime.
> > (NOTE:>> Discussion on frequency is of secondary importance here -
> > the main
> > >> issue is that the SSTskin is that retrieved using an infrared
> > >> radiometer)
> > >> [Proposed CF-names: SSTskin, skin_layer_SST,
> > skin_layer_sea_surface_temperature]>>
> > >>
> > >> The sub-skin sea surface temperature (SSTsub-skin)
> > >> The subskin temperature (SSTsubskin) represents the temperature
> > at the
> > >> base of the conductive laminar sub-layer of the ocean surface. For
> > >> practical purposes, SSTsubskin can be well approximated to the
> > >> measurement of surface temperature by a microwave radiometer
> > operating>> in the 6-11 GHz frequency range, but the relationship
> > is neither
> > >> direct nor invariant to changing physical conditions or to the
> > >> specific geometry of the microwave measurements. (NOTE:
> > Discussion on
> > >> frequency is of secondary importance here - the main issue is
> > that the
> > >> SSTsub-skin is that retrieved using a microwave radiometer)
> > >> [Proposed CF-names: SSTsubskin, Sub-skin_SST, sub-
> > skin_sea_surface_temperature]>>
> > >>
> > >> The surface temperature at depth (SSTz or SSTdepth)
> > >> All measurements of water temperature beneath the SSTsubskin are
> > >> referred to as depth temperatures (SSTdepth) measured using a wide
> > >> variety of platforms and sensors such as drifting buoys, vertical
> > >> profiling floats, or deep thermistor chains at depths ranging from
> > >> 10-2 - 103m. These temperature observations are distinct from
> > those>> obtained using remote sensing techniques (SSTskin and
> > SSTsubskin) and
> > >> must be qualified by a measurement depth in meters (e.g., or SST(z)
> > >> e.g. SST5m).
> > >> (NOTE: I'm happy with Alison and Nan suggestions regarding the
> > use of
> > >> sea_water_temperature followed by a depth attribute. Without the
> > >> depth attribute the data are only of marginal use in data
> > assimilation>> systems and for blending. Many of the problems we
> > have in the
> > >> satellite SST community today stem from the fact that depth was not
> > >> included as an essential component of the measurement. Now that
> > some>> satellite radiometers are providing more accurate and
> > consistent>> measurements of SST than can be obtained in situ
> > (O'Carroll et al
> > >> JTECH, 2007) depth is essential!!) So to answer Alisons question
> > >>
> > >> "We already have the standard name sea_water_temperature which is
> > >> defined as follows: "For the temperature of sea water at a
> > particular>> depth or layer, a data variable of
> > sea_water_temperature with a
> > >> vertical coordinate axis should be used." Would this meet your
> > >> needs?" The answer is YES it does and we will work on this within
> > >> GHRSST-PP.
> > >>
> > >>
> > >> The foundation temperature (SSTfnd) (Please look at figure
> > provided at
> > >> https://www.ghrsst-pp.org/SST-Definitions.html to make sense of
> > this)>> The foundation SST, SSTfnd, is defined as the temperature
> > of the
> > >> water column free of diurnal temperature variability (daytime
> > warming>> or nocturnal cooling) and is considered equivalent to the
> > SSTsubskin>> in the absence of any diurnal signal. It is named to
> > indicate that it
> > >> is the foundation temperature from which the growth of the diurnal
> > >> thermocline develops each day (noting that on some occasions
> > with a
> > >> deep mixed layer there is no clear SSTfnd profile in the surface
> > >> layer). Only in situ contact thermometry is able to measure
> > SSTfnd and
> > >> analysis procedures must be used to estimate the SSTfnd from
> > >> radiometric satellite measurements of SSTskin and SSTsubskin.
> > SSTfnd>> provides a connection with the historical concept of a
> > "bulk" SST
> > >> considered representative of the oceanic mixed layer temperature
> > and>> represented by any SSTdepth measurement within the upper
> > ocean over a
> > >> depth range of 1-20+m. SSTfnd provides a more precise, well-
> > defined>> quantity than previous loosely defined "bulk" SST and
> > consequently, a
> > >> better representation of the mixed layer temperature. In general,
> > >> SSTfnd will be similar to a night time minimum or pre-dawn value at
> > >> depths of ~1-5 m, but some differences could exist. Note that
> > SSTfnd>> does not imply a constant depth mixed layer, but rather a
> > surface>> layer of variable depth depending on the balance between
> > >> stratification and turbulent energy and is expected to change
> > slowly>> over the course of a day.
> > >> [Proposed CF-names: SSTfnd, Foundation_Temperature,
> > >> foundation_sea_surface_temperature]
> > >>
> > >> (NOTE: The main purpose of SSTfnd is to remove from the
> > vocabulary of
> > >> scientists the totally confusing and lazy term bulk SST which is
> > >> meaningless in the context of modern measurements, for data
> > >> assimilation and simply perpetuates confusion and erroneous
> > >> assumptions (Bit harsh, I know, but essentially true!)). To answer
> > >> Alison's question:
> > >>
> > >> "Does this mean that the foundation temperature is
> > measured/modelled>> at the base of the thermocline so that the
> > values are intrinsically
> > >> free of diurnal variation [YES], or is the diurnal variation
> > >> statistically removed from the data [it could be - especially when
> > >> blending data for statistical analyses]?" The answer is yes in
> > both>> cases. I hope that a new 'surface' and associated name can be
> > >> introduced to represent this quantity which is the quantity that
> > most>> global SST analysis systems produce today. There is a nice
> > figure>> showing what SSTfnd is at
> > >> https://www.ghrsst-pp.org/SST-Definitions.html
> > >>
> > >>
> > >> I should note that I had a small WMO/IOC JCOMM task team set up as
> > >> part of the SOT to look at this a year or so ago which concluded at
> > >> this years SOT. The definitions presented above above were
> > adopted by
> > >> the WMO CBS. I Hope this makes things clearer and more straight
> > >> forward and I sense that the main concern is with the in situ folk
> > >> regarding the details and not the principles behind SSTz.
> > >>
> > >> Take care and with best regards
> > >>
> > >> Craig
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >>
> > >
> > > _______________________________________________
> > > CF-metadata mailing list
> > > CF-metadata at cgd.ucar.edu
> > > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> > >
> > _______________________________________________
> > CF-metadata mailing list
> > CF-metadata at cgd.ucar.edu
> > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
> >
>
> _______________________________________________
> CF-metadata mailing list
> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>
--
Dr Craig Donlon
Director of the International GODAE SST Pilot Project Office
Met Office Hadley Centre,
Fitzroy Road, Exeter, EX1 3PB United Kingdom
Tel: +44 (0)1392 886622 Mob:07920 235750
Fax:+44 (0)1392 885681
Skype ID:crazit
SkypeIn: +44 0141 416 0882
E-mail: craig.donlon at gmail.com
http://www.ghrsst-pp.org
_______________________________________________
CF-metadata mailing list
CF-metadata at cgd.ucar.edu
http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
--
This message (and any attachments) is for the recipient only. NERC
is subject to the Freedom of Information Act 2000 and the contents
of this email and any reply you make may be disclosed by NERC unless
it is exempt from release under the Act. Any material supplied to
NERC may be stored in an electronic records management system.
Received on Thu Aug 16 2007 - 02:25:12 BST
