This reply addresses comments on our physically derived complementary relationship (CR) framework, which challenge both the framework’s practical performance and our physical interpretation of apparent potential evapotranspiration (PETa). We clarify that PETa represents an atmospheric aerodynamic upper limit instead of a surface energy-limited flux. Using the identical FLUXNET dataset of 124 sites to replicate the benchmark results reported in the comment, we quantify that errors in estimated evapotranspiration (ET) primarily originate from two sources: inaccurate parameterization of aerodynamic resistance (ra) and surface energy imbalance in eddy-covariance measurements. Both factors directly introduce uncertainties in computed PETa and propagate the errors in PETa into final ET estimates. Generalized calibration schemes for ra across diverse land cover types and further refinements to CR-based ET estimation frameworks are essential for mitigating ET estimation uncertainties in future CR applications.
- Open Access
- Communication
Reply to comment by Szilagyi and Crago on “Physical Interpretation of the Complementary Relationship for Evapotranspiration”
- Sha Zhou 1,2,*,
- Jinfeng Zhao 1,2,
- Bofu Yu 3
Author Information
Received: 20 Apr 2026 | Revised: 22 Jun 2026 | Accepted: 13 Jul 2026 | Published: 21 Aug 2026
Abstract
Keywords
evapotranspiration | complementary relationship | surface energy balance | aerodynamic resistance parameterization
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