EAMxx: Add namelist vars for disabling P3 subgrid cldfrac

[whannah1]

These flags change the input P3 cloud fraction by setting them to 1 everywhere. Currently they default to False, but we will likely enable them as part of the effort to address the popcorn convection problem.

[BFB]

[github-actions]

PR Preview Action v1.4.8
🚀 Deployed preview to https://E3SM-Project.github.io/E3SM/pr-preview/pr-6849/
on branch gh-pages at 2024-12-19 18:09 UTC

[mahf708]

This is fine, but we want better docs. If you want to give extra flexibility to users, you can have these namelist params be reals (and you can ensure they are between 0 and 1). If you add the docs like I commented, they will appear readily here: https://docs.e3sm.org/E3SM/EAMxx/common/eamxx_params/. For example, see how the namelist parameter just above the added ones appear:

p3::do_ice_production:
description: Flag to turn on ice production processes (loss processes unaffected)
type: logical

Whereas your current ones look like:

p3::fix_cld_frac_r:
description: MISSING
type: MISSING

[mahf708]

@whannah1 just a minor request to update the docs. The "scientific worry" isn't important

[mahf708]

👍

[tcclevenger]

Since the params do not change throughout the run I would prefer not have 3 deep_copy() calls in run_impl() but instead to add bools struct variables to p3_preamble by passing params here

E3SM/components/eamxx/src/physics/p3/eamxx_p3_process_interface.cpp

Line 280 in e58531e

p3_preproc.set_variables(m_num_cols,nk_pack,pmid,pmid_dry,pseudo_density,pseudo_density_dry,

then inside the preamble we can set these views appropriately

E3SM/components/eamxx/src/physics/p3/eamxx_p3_process_interface.hpp

Line 108 in e58531e

cld_frac_l(icol,ipack) = ekat::max(cld_frac_t_pack,mincld);

cld_frac_l(icol,ipack) = set_cld_frac_l_to_one ? 1 : ekat::max(cld_frac_t_pack,mincld);

[whannah1]

The plot below shows the result of these flags for days 5-10 of an ensemble of 10-day DPxx runs of the GATE-IDEAL case.

Here's a simple legend:

black  - control
red    - set_cld_frac_l_to_one=true
green  - set_cld_frac_i_to_one=true
blue   - set_cld_frac_r_to_one=true
purple - all 3 flags set to true

The ice fraction flag has a non-zero, but inconsequential effect. The liquid fraction flag mainly affect the cloud number concentration. The rain fraction flag has the largest effect, and enabling all 3 flags looks most like the case with only the rain fraction flag.

A key thing to notice is the increase in rain amount at low levels when the rain fraction flag is enabled. This is critical to improving our representation of cold pools.

Taken together I don't see any good reason not to just enable all 3 flags by default - but this topic will be the subject of a future PR.

[mahf708]

Thanks @whannah1. I kept your impl the same but moved all options to a struct for runtime options we have.

@AaronDonahue @bartgol @tcclevenger, please take a look at your convenience. I do want to move all namelist parameters in p3 to the P3Runtime struct at some point. Still a few remaining ones I will address in a separate PR

Copilot wasn't able to review any files in this pull request.

Files not reviewed (4)

• components/eamxx/cime_config/namelist_defaults_scream.xml: Language not supported
• components/eamxx/src/physics/p3/eamxx_p3_process_interface.cpp: Language not supported
• components/eamxx/src/physics/p3/eamxx_p3_process_interface.hpp: Language not supported
• components/eamxx/src/physics/p3/p3_functions.hpp: Language not supported

[tcclevenger]

I'll integrate next week

[tcclevenger]

Merged to next