Unexplained systematic skill over the Swiss Plateau

Identify the cause of the systematic contribution to Varda-single’s positive two-metre-temperature skill over the Swiss Plateau.

Background

The spatial decomposition of mean-square-error skill shows that some regions of the Swiss Plateau have a substantial systematic contribution to Varda-single’s positive two-metre-temperature skill.

The authors offer a physical hypothesis for analogous behaviour in mountain valleys but explicitly state that they cannot explain the Swiss Plateau signal. The mechanism producing this regional skill therefore remains unresolved.

References

We do not have a clear explanation for the systematic contribution to positive skill in the Swiss Plateau.

— Varda-single-1.0: deterministic data-driven weather forecasting at 1 km resolution over Switzerland's complex topography  (2610.01835 - Pennino et al., 1 Oct 2026) in Section 5.2, Spatial distribution of forecast skill