TSS oscillations
Strong oscillations may occur in SNOWPACK simulations with MO-stability:
The problem likely arises when the surface temperature gets higher than the air temperature. This may happen due to shortwave absorption inside the snowpack. Then, unstable atmospheric conditions arise, and exchange coefficients alpha and beta for sensible and latent heat get extremely non-linear and sensitive to small perturbations of surface temperature. The implicit boundary conditions do not take this into account, so that may introduce large oscillations.
The oscillations may be reduced in amplitude by running SNOWPACK in small enough time steps (15 minutes is normally OK). As this is not practical for Alpine3D simulations, a quick-and-dirty solution is implemented in Meteo.cc to suppress unstable conditions in case the upper node is below 0 degC (commit 630).
Probably the only ""clean"" solution is to have the temperature equation solver run at smaller time steps in case of unstable atmospheric stability, re-iterating also over MicroMet to update the atmospheric stability. This involves some significant code changes.