[MITgcm-support] Vertical heat balance in the ocean

[Shatwell, Peter A]

Wow, thank you so much for pointing me to this link, Yu Kun! And thanks also to Martin Losch for pointing me to swfrac.F in the source code.

I’ve now calculated the shortwave penetration offline, and the balance is looking a lot better! (figure attached) There’s still a small positive bump, but perhaps this will be closed by other terms as outlined in Yu Kun’s python notebook below.

All the best,

Peter

--
Peter Shatwell
PhD student at MPECDT
Space and Atmospheric Physics
Imperial College London
Huxley 714
On 25 Aug 2020, 18:13 +0100, Yu-Kun Qian <qianyk at mail3.sysu.edu.cn>, wrote:
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Hi Peter,

In case you use python, you may find this notebook useful
https://github.com/miniufo/notebooks/blob/master/Budget%20in%20MITgcm%20Part%20I.ipynb

This is a summary of my practice to close the heat budget, which is based on a previous notebook by Ryan Abernathy on Pangeo website.  Now the link seems broken.

The shortwave heating can be calculated offline if you have oceQsw output.  The code snippet __sw_fraction is a copy from the model source code, and calculates the short wave penetration fraction to a specific depth.  Hope this helps.

Sent from my iPad

在 2020年8月25日，21:48，Shatwell, Peter A <peter.shatwell12 at imperial.ac.uk> 写道：


Hello helpful MITgcm community,

I’m using the DDrake coupled configuration with a cube-sphere (C24) grid with 15 vertical levels (more details in Ferreira et al. 2010, https://doi.org/10.1175/2009JCLI3197.1), and I am trying to close the vertical heat balance in the model ocean.

I have computed vertical profiles of the advective vertical heat flux (diagnostic ADVr_TH) and the total diffusive vertical heat flux (diagnostics DFrE_TH and DFrI_TH). These advective and diffusive fluxes almost exactly balance throughout the water column (see attached figure), consistent with the traditional ‘upwelling-diffusion’ vertical balance of Munk ’66 and others (I’ve plotted it such that a positive flux is downwards i.e. a warming effect).

However, there is a strong departure from this balance in the top ~130 m of the ocean, indicating strong net upward cooling. Apparently penetrating shortwave radiation in the model could balance this cooling, but I am not sure how to properly confirm this. Are there existing model diagnostics to plot the shortwave penetration? Or could I estimate it from other outputs?

Or is there something else that could provide a warming effect near the ocean surface? Or should I expect this balance to even hold at all?

Thanks and all the best,

Peter

--
Peter Shatwell
PhD student at MPECDT
Space and Atmospheric Physics
Imperial College London
Huxley 714
<ctrl_climate_vertical_heat_balance.jpg>
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