A GRACE/‐FO‐Based Framework for Improved Reproduction of Water‐Balance‐Constrained Evapotranspiration Across Hydroclimatic Regimes

Abstract

Diagnosing monthly evapotranspiration (ET) under water‐balance constraints is essential for understanding land‐atmosphere interactions and managing water resources under changing climate conditions. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) and its successor GRACE Follow‐On (GRACE/‐FO) missions have provided precise observations of terrestrial water storage, enabling improved constraints on large‐scale water balance. Building on these advances, we develop a GRACE/‐FO‐constrained diagnostic to framework to reproduce monthly ET derived from water‐balance (ET _Budget ). The framework that applies the one‐parameter Budyko formulation during dry (water‐limited) months and the two‐parameter power‐law formulation during wet (energy‐limited) months, with the aridity index distinguishing between them. The framework is evaluated across 297 major river basins using ET _Budget as a reference and compared with conventional Budyko‐only approaches. Results show that, relative to the Budyko‐only approaches, the proposed framework substantially reduces deviations from ET _Budget , especially in 189 humid basins, while maintaining robust performance in 15 arid and 93 semi‐arid regions. The proposed framework yields mean annual ET and P‐ET of 612.5 and 191.4 mm yr ⁻¹ over major river basins, respectively, showing no significant long‐term trends but distinct spatial patterns and contrasting responses to the El Niño‐Southern Oscillation phases. These findings highlight the value of the proposed framework as a diagnostic tool for improving the representation of monthly water‐balance ET across diverse hydroclimatic conditions.