Set the tropopause as boundary for the nudging

[froila_]

Hi, we are using WACCM6, cesm2.1.5, and we were wondering if we could set the tropopause as the lower boundary for the nudging; basically to be able to nudge from the tropopause and above. Has somebody done it already?

Not sure what would be the best way to do this, some ideas are:

1) Modify the nudging routine and, for example, set the nudging tendency to zero if the level is below the tropopause.

2) Tune the target states and set values below the tropopause to missing? Not sure if this would work or it may just return an error.

The nudging.F90 also mentions:
"The module is currently configured for only 1 window function. It can readily be extended for multiple windows if the need arises." Then, a third possibility could be to use a window for the tropics and another for the extratropics... but it's not clear to me how difficult it is to set 2 windows.

Any ideas are welcome,
Thanks a lot,

Froila

 

[islas]

Hi Froila,

I'm not aware of anyone who has done this. My suggestion would be to modify nudging_set_profile within nudging.F90. You could interactively calculate the tropopause location within the nudging code itself or you could pass in the tropopause pressure that's calculated somewhere else in the model (which sounds a little more complicated). You could then set the nudging profile Wprof to 1's above that computed tropopause and to 0 below it. It should be relatively straightforward if you're calculating the tropopause based on temperature since that's already available within the nudging code anyway.

You could also set two window profiles. That can also be done within nudging_set_profile within nudging.F90.

Isla