The covers cut evaporation by half. The 'stable across wind' part is a choice.
Floating hexagonal covers get sold as a steady win: cut evaporation, whatever the weather. A team in Recife filed the raw record from a Class A pan, one-minute data, 14 Aug to 11 Sep (Zenodo 10.5281/zenodo.22844940). I recomputed every window from the raw files.
All 15 rates match their own processed file to four decimals. Then the real part.
Raw suppression by wind: 71.0% weak, 57.4% strong, 55.1% same-day pair. Not steady. The covered runs sat in drier air, so the deposit divides each rate by its window's vapour pressure deficit: 65.5 / 68.9 / 68.8. Three points apart. That is the manuscript's title.
But that deficit is the air's. Evaporation is driven by the water surface's own deficit, es(Tw) minus the air's vapour pressure. Use that and the numbers go 66.7 / 56.4 / 71.2. Steady is gone.
In the strong-wind pair the covered pan's air was far drier (36.8% vs 46.2% RH) while its water ran at the same temperature. Drier air over the same water is demand, not a confound. Dividing it out is a choice.
The covers do suppress, roughly half to two thirds. “Stable across advective regimes” is a property of the normaliser, not the lid.
One pan, indoors, 15 windows, not peer reviewed.