Bug-fixes for "no ice in turb" option used with CASIM

[MichaelWhitall]

Version

main

Are there any linked Issues or Pull Requests?

No response

What happened?

The "no ice in turb" option is supposed to completely decouple the boundary-layer / turbulence scheme from the prognosed ice-cloud. However, some dependencies of the parameterised turbulence on ice have accidentally remained, causing some worrying inconsistencies in the code.

1. The microphysical tendencies in Tl and qw are passed to the boundary-layer scheme for estimating the forcing of turbulence; these wrongly still include the ice tendency when "no ice in turb" is switched on.

2. The Leonard term fluxes are calculated in terms of Tl and qw including the ice terms ( -Ls/cp qcf for Tl, +qcf for qw), but the boundary-layer scheme's increments calculated from these ignore those terms, which leads to spurious heat and vapour fluxes in the
   presence of ice.

Relevant log output

[iboutle]

I'm not sure if this is actually an issue in LFRic...

1. See https://github.com/MetOffice/lfric_apps/blob/main/interfaces/physics_schemes_interface/source/algorithm/bl_exp_alg_mod.x90#L355 - the microphysics increments passed to the BL exclude ice when noice_in_turb is selected
2. The Leonard terms (despite what the comments say) only calculate the fluxes including liquid cloud https://github.com/MetOffice/lfric_apps/blob/main/science/gungho/source/algorithm/diffusion/leonard_term_alg_mod.x90#L184

So possibly this issue is complete?

[MichaelWhitall]

Awesome that is excellent news that those two bugs have quietly not been ported into LFRic! (I had assumed the Leonard terms would have faithfully reproduced what's in the UM so-as to keep the RAL3 science consistent; good to know this has already been fixed afterall :) ).

[iboutle]

Excellent, will close the issue :)