Table 1.

PET input variables as estimated from ERA5 variables.

Input variable	FAO56 definition	Estimation
Rn	Net radiation at the crop surface [MJ m-2 day-1]	Derived from ERA5 surface net solar/thermal radiation
G	Soil heat flux density [MJ m-2 day-1]	Following Eq 42 in ref. 36 Gday ≈ zero
T	Mean daily air temperature at 2 m height [°C]	ERA5 2 m temperature
u2	Wind speed at 2 m height [m s-1]	Derived from ERA5 10 m u and v components and downscaled using Eq 47 in ref. 36
es	Saturation vapor pressure [kPa]	Estimated from ERA5 2 m temperature using Eq. 11 in ref. 36
ea	Actual vapor pressure [kPa]	Estimated from ERA5 2 m dewpoint temperature using Eq 14 in ref. 36
γ	Psychrometric constant [kPa °C-1]	Estimated using Eqs. 7 and 8 from ref. 36 using ERA5 geopotential to derive elevation above sea level
Δ	Slope vapor pressure curve [kPa °C-1]	Estimated from ERA5 2 m temperature using Eq 13 from ref. 36