Gap-Filling for Daily Evapotranspiration Observations with full-factorial method at Global Flux Sites

The comparative analysis of the filled ET data against three products—ERA5-Land, BESS, and GLEAM—reveals a high degree of consistency across 264 stations, with mean |MAE| and |RMSE| values of 0.32 mm/day and 0.92 mm/day, respectively. For 49 stations, the filled ET data aligns more closely with adjacent observed data or exhibits higher temporal coherence with observed ET data, net radiation, and LAI trends than the three ET products.

However, the reliability of the filled ET data at 26 stations requires further validation due to the scarcity of observed data or the influence of input data issues. Therefore, the filled ET data for a total of 313 sites demonstrates a high degree of reliability, with data records spanning from 1 to 27 years across these sites (2210 site-year). The underlying surface types at these sites are diverse, including forests (131 sites), grasslands (80 sites), farmlands (42 sites), shrublands (32 sites), wetlands (25 sites), and other surface cover types (3 sites).