# In situ density given by NEMO's equation of state

**URL:** <https://nemo-ocean.discourse.group/t/in-situ-density-given-by-nemos-equation-of-state/851>\
**Category:** v3.6\
**Created:** [21 February 2025 14:38 UTC](https://nemo-ocean.discourse.group/t/in-situ-density-given-by-nemos-equation-of-state/851 "2025-02-21T14:38:28Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Saran](https://avatars.discourse-cdn.com/v4/letter/s/7ea924/32.png) [@Saran](https://nemo-ocean.discourse.group/u/Saran)\
**Post date:** [21 February 2025 14:38 UTC](https://nemo-ocean.discourse.group/t/in-situ-density-given-by-nemos-equation-of-state/851/1 "2025-02-21T14:38:28Z")

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Hello,  
For Nemo V3.6, the documentation says that the EOS80 module gives in-situ density as the output by taking in Potential temperature and practical salinity as input. In-situ density should be used in the momentum equations.

However, this is given in the EOS module (eosbn2.f90):  
ln\_eos80 : polynomial EOS-80 equation of state is used for rho(t,s,z). rho is the insitu density.  
Check value: rho = 1028.35011066567 kg/m^3 for z=3000 dbar, pt=3 Celsius, sp=35.5 psu

The in-situ density is just 1028.35 at a depth of 3000meters (which is quite low).

Can anyone please explain why this is happening? Any answer would be much appreciated.