Skip using fluxes provided by land component for first time step

[uturuncoglu]

Due to the dependency between atmosphere and land components, the atmosphere model gets all zero from land component model in the initial coupling time step. This PR aims to fix this issue and skips data coming from land component (all zero) at first coupling time step and use the land fluxes calculated by noahmp land model found in ccpp/physics. After first coupling time step, the coupled configuration (cpld_control_p8_lnd) will continue to use fluxes coming from component model.

[uturuncoglu]

JFYI, The top level UFS WM PR is still in draft mode. I am still working on it.

[uturuncoglu]

@grantfirl JFYI, I might also need to introduce another input.nml option to make skipping first time step for land optional since it is related with the run sequence of the coupled application and we might not need for the data atmosphere coupled configurations.

[grantfirl]

@grantfirl JFYI, I might also need to introduce another input.nml option to make skipping first time step for land optional since it is related with the run sequence of the coupled application and we might not need for the data atmosphere coupled configurations.

@uturuncoglu Thanks. I see that the upstream PRs are in draft. We'll re-review if necessary. There are several PRs to be merged before this one, so it's unlikely this would bubble to the top in 2 weeks time anyway.

[uturuncoglu]

@grantfirl Thanks. That is totally fine. I am still working on it. Once it is ready I'll change UFS WM level PR from draft to ready to review.

[yangfanglin]

@uturuncoglu @barlage @HelinWei-NOAA I assume this is a temporary fix. Otherwise, updating land as a component model cannot happen.

[uturuncoglu]

@yangfanglin This is just for fully coupled S2S application and we could make it optional. The main issue is the run sequence. If you have a cold start and all components are running in the same time then you could not provide land fluxes in the first coupling time step. It is very similar to MOM6 case. It is also skipping first coupling time step as I know (except warm start maybe). If you want I could implement similar way in land and we could get rid of this part or we could discuss other possible options (let me know if you have something in your mind). In atm-land only case, I am having one time step delay between components and we have no this issue. BTW, we are trying to finalize the JTTI project soon. So, this will be a last PR from my end.

[barlage]

Just had a meeting with @uturuncoglu re: this. I think we need something similar to what is being done in sfc_ocean to calculate some initial consistent fluxes that aren't dependent on any specific land model. Then, this could also be used for other land components.

[uturuncoglu]

@yangfanglin @barlage Probably, I'll implement and test it in a couple of days.

[uturuncoglu]

@barlage I could not find anything related with 2 meter temperature and specific humidity. A this point, I am just setting like,

         t2mmp(i) = tskin(i)
         q2mp(i) = qsurf(i)

Do you think that this is good estimation for the initial coupling time step?

[barlage]

I think that's fine for the first time step.