I've asked for some feedback internally, based on the definitions at the web site and in the enclosed email. A few concerns were raised, but I'm not sure what the terms and definitions now proposed for CF are. Can someone provide the summary list, or should I try to summarize myself, or should I describe concerns with respect to the definitions referenced below?
By the way, "sea_water_temperature with a depth attribute" is fine; it is the other terms/definitions that may be a little confusing.
John
At 4:20 PM +0000 2/14/08, Craig Donlon wrote:
>Hi Olivier:
>Just to remind us all (we need to get this agreed if possible as the
>GHRSST-PP are working on a new set of documentation) and the large EU
>MyOcean project will be using CF as a the baseline for ocean products.
>
>My comments on your summary mail are in line below. also attached is
>the original proposal. Note that the operational GHRSST-PP community
>is moving some 25Gb SST data in netCDF _each day_ using GHRSST-PP
>definitions and that the World Meteorological Organisation has
>accepted the proposed terms already.
>
>I hope we can resolve these issues as quickly as possible now.
>
>Regards,
>Craig
>
>
>Summary of proposal so Far (from Oliveier Laurent mail)
>
>> *SSTint (GHRSST-PP): surface_temperature (CF)
>OK as we do not use this in operations but clarification on the
>interface may still be useful in a description.
>
>> *SSTskin (GHRSST-PP):
>> - sea_surface_temperature_in_skin_layer
>> - skin_sea_surface_temperature
>> - sea_skin_temperature?
>> - sea_water_temperature with a depth attribute ?
>We still propose skin_layer_sea_surface_temperature as in the
>GHRSST-PP proposal.
>
>> *SSTsubskin (GHRSST-PP):
>> - sea_surface_temperature_in_subskin_layer?
>> - subskin_sea_surface_temperature?
>> - sea_subskin_temperature?
>> - sea_water_temperature with a depth attribute ?
>> (same comments as for SSTskin)
>I accept subskin_sea_surface_temperature
>
>
>> *SSTdepth (GHRSST-PP): sea_water_temperature (CF)
>
>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. but The need for the depth information needs to be
>mandatory can this be done? without depth it is somewhat
>meaningless...
>
>>
>> *SSTfnd (GHRSST-PP):
>> - sea_surface_temperature_at_diurnal_thermocline_base
>This is not correct. 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
>So I would argue for foundation_sea_surface_temperature
>
>Original proposal==========================================
>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).
>
>
>
>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]
>
>
>
>
>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.
>
>
>--
>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
>
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--
----------
John Graybeal <mailto:graybeal at mbari.org> -- 831-775-1956
Monterey Bay Aquarium Research Institute
Marine Metadata Initiative: http://marinemetadata.org || Shore Side Data System: http://www.mbari.org/ssds
Received on Thu Feb 14 2008 - 11:22:45 GMT
