Water Mass Leakage in Simpler Coupled Model

[jray]

Hi,

I'm currently setting up and running a Ridge model based on a simple coupled framework. The model is created following the instruction here: VisualCaseGen: Ridge World | Community Earth System Model. And the CESM version is cesm2_3_beta17_GUI.

I have diagnosed a water mass leakage issue in the coupled simulations. There is a negative drift in sea surface height over time. Additionally, the global integral of net freshwater flux into the ocean (wfo) is also negative. It indicates a loss of water mass from the ocean system.

How can I ensure freshwater conservation in this coupled configuration? Are there specific settings in CESM, MOM6, or ESMF that need to be modified to enforce conservation of freshwater fluxes?

I look forward to any suggestions or insights from the community.
Thanks

 

[jray]

I'm following up on my earlier post about the freshwater conservation issue in my Ridge configuration (CESM version cesm2_3_beta17_GUI).

After further investigation, I found that the land model (CLM) is producing runoff (QRUNOFF) as expected, but in the ocean model (MOM6), the received runoff (friver) is zero throughout the simulation. This indicates that the runoff is not being correctly passed from CLM to MOM6, which likely explains the negative sea surface height drift and net loss of freshwater (wfo < 0) in the ocean.

How can I properly set up the model so that runoff from land model is correctly passed to MOM6?

 

[Youwei]

Hi Ray,
As you mentioned above, the precipitation on the polar caps and ridge continent cannot flow back to ocean as runoff, leading to the water loss in the ocean, even though there is no sea ice formation in this Ridge world. Ideally, it should use an idealized runoff to resolve this issue. However, since the land area is relatively small in the Ridge world, we can adjust fresh water in MOM6 to keep fresh water conserved in the ocean by

ADJUST_NET_FRESH_WATER_TO_ZERO = True

 

[jray]

Thank you, Youwei.