[ecco-support] [EXTERNAL] the potential density

[Ivana Cerovecki]

Thank you very much Ian,
Ivana


On Thu, Mar 11, 2021 at 11:01 AM Fenty, Ian G (US 329C) <
ian.fenty at jpl.nasa.gov> wrote:

> Hi Ivana,
>
> >> I want to calculate the potential density relative to the surface using
> ECCO output (THETA and SALT  fields....) and "density.m" function from
> gcmfaces, where "p" is the depth of tracer points, do I specify pref=0, and
> the potential density is given by rhop, as:  [rhop,rhpis,rhor] =
> density(t(:),s(:),p(:),pref(:));
>
> That's what I would do.  You do have some choices about what to use for
> pressure.  You could directly convert model z depth to pressure in decibars
> or you could use the latitude-dependent pressure (e.g., the matlab seawater
> package 'sw_pres' from
> https://urldefense.com/v3/__http://globec.whoi.edu/globec-dir/CTDSoftware/SeaWater/__;!!Mih3wA!TM8nqsHsQgnfBzc5NYAL0p0QD2Gb0fHO7dBKqHXt1gf4lZAIhVnANq9fFXxvGZ-KXw$
> ).
>
> In case you are not aware, there is a Matlab representation of the JMD95
> eos here:
>
> https://urldefense.com/v3/__https://github.com/MITgcm/MITgcm/blob/master/utils/matlab/densjmd95.m__;!!Mih3wA!TM8nqsHsQgnfBzc5NYAL0p0QD2Gb0fHO7dBKqHXt1gf4lZAIhVnANq9fFXz13p2vfw$
>
>
> >> If following Iudicone et al. (2008), I want to estimate the equation of
> evolution of the locally referenced potential density defined at a
> reference pressure chosen as the local pressure pr, I get that by
> multiplying the temperature tendency equation by alpha, salt tendency
> equation by beta, and combine them. In doing so, is this a correct way to
> obtain alpha?
> >> alpha=sw_alpha(s(:),t(:),p(:),'ptmp'),
> >>where again s is obtained from the SALT fields, t from THETA and p is
> the depth of the tracer points.
>
> Yes, that is what I would do.  Again, you could choose a different eos to
> calculate alpha. The eos used in the seawater package 'sw_alpha' routine
> seems to be same JMD:
> https://urldefense.com/v3/__https://www.mathworks.com/matlabcentral/mlc-downloads/downloads/submissions/47595/versions/12/previews/mixing_library/private1/seawater/sw_aonb.m/index.html?access_key=__;!!Mih3wA!TM8nqsHsQgnfBzc5NYAL0p0QD2Gb0fHO7dBKqHXt1gf4lZAIhVnANq9fFXzecweOEA$
>
> -Ian
>
>
>
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