4.8.0 Grell-Freitas-Li scheme kills convection

M

meteoadriatic

Member
Hello,
The version 4.8.0 replaces pretty good scale-aware convection scheme, Grell-Freitas, that was battle-tested, extremely good behaved, with "improved" one, namely Grell_Freitas-Li, but this one shows pretty dramatic regression in quality.

I'm testing one challenging convective case using 3 km grid and just wondered if GFL will do better than GF. So I compiled 4.8.0 and used bit-identical namelist, with cu_physics = 3, which means that active cumulus scheme is now GFL instead of GF.

These are results, which speak for themselves:

1781214393678.png

All coastal convection that scale-aware GF correctly allowed to be explicitelly resolved by 3 km grid, is supressed and turned into drizzle in GFL.

I don't understand why this has been done (replacing good, operational scheme by many users, with new, untested one, instead of adding new option along existing one)?

Best wishes,
Ivan
 
Hi,

That should not result in what we see here. The fact that there is no coupling between convective clouds and radiation, means that radiation is not modified by the convective scheme, which makes small difference yes, but if anything, in oposite direction I think (more convective energy present). What I think the problem is, is that the new scheme is tuned for global simulations and coarse grids and it now behaves almost as classic, non-scale-aware schemes. Which I'm just fine with, but the main question here is - why the old GF is removed. It was perfect cu scheme.
 
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