A multi-scale evaluation of 30 empirical models for reference evapotranspiration estimation in a data-scarce semi-arid region: A case study of Jhansi, India

Study region Semi-arid agro-climatic zone of central India. Study focus This study evaluated the performance of 30 empirical ET 0 models; ten each from the temperature-based, mass-transfer-based and radiation-based categories, against the FAO-PM standard using 21 years (2000–2020) of daily meteorological observations at Jhansi, India. The analysis is framed as a benchmarking of empirical models against FAO-PM. Model accuracy was quantified at daily, monthly, seasonal and annual scales using four statistical indices (NSE, RMSE, MBE and r), and an integrated model ranking was derived using the entropy-weighted TOPSIS multi-criteria decision-making framework. New hydrological insights for the region The 21-year FAO-PM record reveals a persistent annual atmospheric water deficit of ~731 mm (ET₀ = 1571 mm yr⁻¹ versus rainfall = 840 mm yr⁻¹). This deficit is highly asymmetric: the summer season alone (May–June) accounts for 440 mm of ET 0 against negligible rainfall, defining the period of maximum irrigation demand, while the monsoon surplus is offset within weeks by rapid soil moisture depletion. Pre-winter and winter seasons contribute a further 295 mm of ET 0 . The leading models are wind-driven mass-transfer models, showing that aerodynamic demand rather than solar radiation is the primary control on daily ET₀ variability in this climate. Category alone, however, poorly predicts performance across the models. The Penman model (TOPSIS rank 1, closeness = 0.953) and WMO model (rank 2), requiring only wind speed and vapour pressure inputs, are identified as most accurate FAO-PM substitutes at the daily and seasonal scale. The findings of the study are location-specific and need validation before applying to other locations in the semi-arid region.