Optimization, applicability, and mechanisms of potential evapotranspiration models for meadow wetland ecosystems in semi-arid region

Arid and semi-arid regions cover more than 30% of the Earth’s land area, and play an increasingly important role in the global water cycle. Accurate estimation of potential evapotranspiration ( PET ) is crucial for understanding regional water cycle patterns, developing hydrological models, and assessing water resources. Based on long-term (2013–2022) in-situ meteorological and flux observations from the meadow wetland ecosystem of the Horqin Sandy Land in northern China, this study systematically refined various PET models and analyzed their applicability for meadow wetland ecosystems in semi-arid regions. The results indicated that PET ranged from 0.02 to 6.93 mm/d, averaging 3.25 mm/d during the growing season (2013–2022). Net radiation ( Rn ), air temperature ( Ta ), and vapor pressure deficit ( VPD ) were the dominant drivers of PET , with significant enhancements observed under Rn > 150 W/m 2 , Ta > 20 °C, and 1 < VPD < 2.3 kPa. The lag time of PET in response to Rn , Ta , and VPD was shorter in spring and autumn than in summer, averaging 0.5 h, − 2 h, and − 2.5 h, respectively. The model applicability ranked as: physically based models > radiation-based models > temperature-based models > aerodynamic-based models. Among the physical models, the Penman–Monteith model achieved the highest accuracy. This study can provide theoretical basis and technical support for ecological restoration, water resource management and water cycle simulation in arid and semi-arid regions.