Good morning all
I've got some pesky model biases in both OpenIFS cy40 standalone (AMIP-type runs) and OpenIFS coupled to NEMO (piControl). Too much precipitation over the western tropical Pacific, warm SST bias over the Southern Ocean (in coupled runs) and weak atmosphere response to ENSO seem to be the biggest problems.
I'd like to experiment with some model tuning to see if I can reduce the problem.
I've found the NAMCUMF namelist, which sets some entrainment and autoconversion parameters, but doubling or halving these does not seem to have any effect at all. I end up with runs that are exactly identical to my control run.
All runs are without SPPT or SKEB.
My question is: How can I tweak the rain/snow autoconversion rates (is it different for shallow and deep convection?), entrainment for shallow and deep convection, and also the non-orographic drag?
It would be great to find some tunable cloud parameters equivalent to ECHAM6 (cf. Mauritsen et al., https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2012MS000154), i.e.
1) autoconversion for convective clouds, 2) lateral entrainment for shallow convection, 3) lateral entrainment for deep conversion, 4) cloud inhomogeneity, and 5) convective mass flux above level of non-buoyancy.
Any help is much appreciated!
Best regards
Joakim