BBL sets wave-modulated bottom stress to zero when SEDIMENT is off

coupling (ocean-wave-atm)
1

Hello

I have implemented a CROCO-WW3 coupled simulation with BBL activated (as per the default coupling cpp keys). I noticed that the bottom stress seen by the model goes to zero in the shallow regions where one would instead expect the waves to increase the bottom stress.

On inspecting bbl.F, it appears that when waves are significant (Ub > Ubc) (bbl.F:345) the wave-modulated bottom stress taucw is only updated inside the #ifdef Z0_BL block (bbl.F:470). Since Z0_BL is defined only when SEDIMENT is defined, and I am running BBL without SEDIMENT, taucw is never updated and is left at its initial value of zero (bbl.F:177), which is what I see in my outputs.

Proposed fix: move bbl.F:471 (endif /* Z0_BL */) up to bbl.F:453, so that the bottom-stress is updated whether Z0_BL is defined or not.

Thanks for taking a look.

Cheers

Giles

2

Hi,

I can confirm that I get unreasonable velocities when running a simulation of a winter storm in the east Mediterranean with CROCO-WW3 coupling and BBL activated. The observed velocity was at most 85 cm/s whereas the model output for the same time and place was 2.0 m/s (after fixing CFL blowup).

When the suggested correction was applied, the modeled velocity at the same peak was 58cm/s, which is slightly better than the 53cm/s I get without the coupling.

Best regards,

Ron

3

Hi @rongoldman ,
Have you ever define ocean salinity (cpp – SALINITY).
then share your KE.
Thank you!
Best regards,