Natural Resources, School of


Document Type


Date of this Version



Hydrol. Earth Syst. Sci., 25, 63–68, 2021


Author(s) 2021.


The paper by Han and Tian (2020) reviews the history of developments in the complementary relationship (CR) between actual and potential evaporation and introduces the generalized complementary principle (GCP) developed by the authors. This comment assesses whether the GCP: (1) can give reasonable results from a wide range of surfaces worldwide; (2) is supported by experimental data that verify the three stages of evaporation implicit in the GCP, particularly in the wet-surface limit; (3) has been proven to be correct by the authors in a previous paper; and (4) is supported by model studies showing that wet surfaces occur predominantly during periods of large-scale moisture convergence. The assessment finds that arguments in favor of the GCP deserve to be taken seriously but ultimately remain unconvincing.