ScholarWorks@성균관대학교

초록

Offline aridity and drought diagnostics typically project widespread terrestrial drying under climate change, whereas fully coupled Earth system models (ESMs) often simulate modest or regionally heterogeneous changes-and in some regions increasing-runoff. This long-standing divergence has been attributed largely to missing vegetation physiological effects and the neglect of sub-annual climate variability in offline diagnostic frameworks. Here, we show that a more fundamental issue is the violation of the diagnostic framework's structural requirement that potential evapotranspiration (PET) and precipitation (P) act as independent climatic constraints. Using Penman and Penman-Monteith formulations, each with and without thermodynamic deflation via the complementary evaporation principle (CEP), we demonstrate that land-atmosphere feedbacks embedded in conventional PET estimates induce strong negative P-PET correlations (-0.45 +/- 0.29; mean +/- standard deviation) across land surfaces, which collapse toward near zero (-0.02 +/- 0.42) after CEP deflation. Preserving PET-P independence substantially reduces inflation of the aridity index and brings offline diagnostic ET trends closer to ESM projections under a strong-emission scenario (from +0.61 to +0.39 mm yr-2; ESM mean: +0.28 mm yr-2). These results indicate that structural inconsistencies-rather than missing physiological processes alone-play a central role in the mismatch between offline diagnostics and ESM hydrology. Ensuring that PET is not inflated by land-atmosphere feedbacks is therefore essential for theoretically valid offline hydrologic assessments under a warming climate.

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