Atmospheric Tracer Mass Conservation in OpenIFS: Single Precision Drift, Weather Divergence, and Stochastic Rounding
The first time you run OpenIFS in single precision, the global CO₂ mass budget will look like it has a severe leak. Here is what we found after tracking the diagnostics term-by-term, why >99.5% of the drift is chaotic weather, and how stochastic rounding fixed the real numerical error.