# Open boundary tracer: TEOS10 cons. temperature, abs. salinity and conversion function to prac. salinity

**URL:** <https://nemo-ocean.discourse.group/t/open-boundary-tracer-teos10-cons-temperature-abs-salinity-and-conversion-function-to-prac-salinity/80>\
**Category:** Regional\
**Tags:** P4Z, TRA\
**Created:** [13 June 2021 16:08 UTC](https://nemo-ocean.discourse.group/t/open-boundary-tracer-teos10-cons-temperature-abs-salinity-and-conversion-function-to-prac-salinity/80 "2021-06-13T16:08:01Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Bijoy](https://avatars.discourse-cdn.com/v4/letter/b/e5b9ba/32.png) [@Bijoy](https://nemo-ocean.discourse.group/u/Bijoy)\
**Post date:** [13 June 2021 16:08 UTC](https://nemo-ocean.discourse.group/t/open-boundary-tracer-teos10-cons-temperature-abs-salinity-and-conversion-function-to-prac-salinity/80/1 "2021-06-13T16:08:01Z")

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Hi all,  
I am using the TEOS-10 in a regional configuration of NEMO4.0.6. It is clear that the model should be initialised with the conservative temperature and absolute salinity. If we use TEOS-10, does the tracer fields provided at the open boundaries also need to be conservative temperature and absolute salinity? Is it correct to say that the conservative temperature and absolute salinity fields are available in the model output ?

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**Author:** ![jchanut](https://yyz2.discourse-cdn.com/free1/user_avatar/nemo-ocean.discourse.group/jchanut/32/9_2.png) [@jchanut](https://nemo-ocean.discourse.group/u/jchanut)\
**Post date:** [14 June 2021 06:52 UTC](https://nemo-ocean.discourse.group/t/open-boundary-tracer-teos10-cons-temperature-abs-salinity-and-conversion-function-to-prac-salinity/80/2 "2021-06-14T06:52:52Z")

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Using Teos-10, open boundary data must be consistent with the model field, e.g. these are supposed to be conservative temperature and absolute salinity. Outputs are the same also (so imagine you use data from a configuration using Teos-10 to force your regional model, no conversion would be required).

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<div class="post-metadata">

**Author:** ![Bijoy](https://avatars.discourse-cdn.com/v4/letter/b/e5b9ba/32.png) [@Bijoy](https://nemo-ocean.discourse.group/u/Bijoy)\
**Post date:** [24 June 2021 08:04 UTC](https://nemo-ocean.discourse.group/t/open-boundary-tracer-teos10-cons-temperature-abs-salinity-and-conversion-function-to-prac-salinity/80/3 "2021-06-24T08:04:13Z")

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Thanks,  
Looks a function `eos_pt_from_ct` is available in _eosbn2.F90_ for ct to pt conversion. Similarly, anyone has a function for the conversion of SA to the SP.

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<div class="post-metadata">

**Author:** ![jchanut](https://yyz2.discourse-cdn.com/free1/user_avatar/nemo-ocean.discourse.group/jchanut/32/9_2.png) [@jchanut](https://nemo-ocean.discourse.group/u/jchanut)\
**Post date:** [24 June 2021 14:29 UTC](https://nemo-ocean.discourse.group/t/open-boundary-tracer-teos10-cons-temperature-abs-salinity-and-conversion-function-to-prac-salinity/80/4 "2021-06-24T14:29:59Z")

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One could use this simple conversion found in _src/TOP/PISCES/P4Z/p4zche.F90_ (r4-0-HEAD):

```fortran
      ! Computation of chemical constants require practical salinity
      ! Thus, when TEOS80 is used, absolute salinity is converted to
      ! practical salinity
      ! -------------------------------------------------------------
      IF (neos == -1) THEN
      salinprac(:,:,:) = tsn(:,:,:,jp_sal) * 35.0 / 35.16504
      ELSE
      salinprac(:,:,:) = tsn(:,:,:,jp_sal)
      ENDIF

```