I'm running relaxation experiments in 43r3 following the namelist changes outlined at How to use OpenIFS in nudged configuration, and I'm trying to work out what the relaxation coefficients and smoothing parameters mean physically. In the trial experiment I've run, I left everything as the default shown on the description page, but changed ALATRLX2=20 and NRLXLMAX=27 (i.e. upwards from lower stratosphere, poleward of 20N). This worked successfully, and did indeed seem rather "tight" with the coefficients at 0.5.
Ideally, I'd like to be able to explain the latitudinal and vertical dependence similar to Figs 1 & 2 in Jung et al 2010 MWR. The furthest I got to was finding relaxgp.F90 subroutine in /src/ifs/transform.
Any insight would be much appreciated. Thank you!