[MITgcm-support] Bulk formula

[Richet, Oceane (O&A, Hobart)]

MITgcmers,

Previously I was running my regional simulations with a restoring temperature and salinity at the surface and at the lateral boundaries. I recently moved to a configuration where now I am using the bulk formula (BULK_FORCE package) at the surface for a more natural surface boundary condition without changing the forcing at the lateral boundaries. Both simulations are forced with a seasonal forcing.

In the case of the restoring forcing at the surface, I used the monthly SST and SSS from the COSIMA model http://cosima.org.au/ (same for the lateral boundaries). For the bulk formula, I use the JRA55 outputs which have been used to force the COSIMA model. Now, the forcing instead to be monthly inputs is 3-hourly inputs - the forcing at the lateral boundaries is still the same as previously but now it has been linearly interpolated in time 3-hourly.

What I observe between these 2 configurations after 12 years of running is that the SST is much colder and does not match the lateral boundary forcing (see figure SST12 - bulk formula). This behavior does not seem to be observe for the SSS (figure SSS_12 - bulk formula). So I am wondering if it is physical or if there is an issue with the bulk formula like for example a units problem as, for the bulk formula, my input file for the temperature is in Kevin and in Celsius for the lateral open boundaries. Also the wind stress is now calculated through the bulk formula from the U and V wind fields.

Has someone already observed this discontinuity between the surface and the lateral boundaries?

Cheers,

Océane Richet
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