Seasonal and regional evaluation of sixteen temperature-based solar radiation models for India using a Global Performance Indicator

Reliable estimation of surface solar radiation is crucial for climatological analyses and land–atmosphere applications; however, direct radiometric observations remain sparse across much of India. Under such data limitations, temperature-based empirical models continue to be widely used, although their seasonal robustness and spatial transferability across diverse climatic regimes remain insufficiently understood. This study assesses the accuracy of temperature-based models in predicting solar radiation required for agricultural planning across India. Daily data on maximum and minimum temperatures and sunshine duration from 14 agrometeorological stations, covering the period 2002–2023, were used to estimate reference solar radiation using the Angström–Prescott model and to validate 16 empirical temperature-input formulations without any local calibration. Model performance was assessed at daily scale using RMSE, MAE, MBE and R², which were synthesized into a Global Performance Indicator (GPI) to obtain season- and location-specific rankings. Results show a clear control of seasonality and geographical setting on model skill: in winter and post-monsoon, the Hargreaves–Samani model (M-1) generally provided the lowest errors across interior and semi-arid stations, whereas humidity-sensitive formulations such as M-5 and the Hassan-based model (M-13) performed better at coastal and high-humidity sites. During the monsoon, when persistent cloud cover weakens the link between diurnal temperature range and radiation, the Rao et al. model (M-2) consistently achieved the highest GPI values at most locations despite overall reduced R². Across all seasons, a small subset of models (notably M-1, M-2 and M-13) emerged as robust and transferable, offering practical, temperature-only options for operational agrometeorological advisories, evapotranspiration estimation and crop simulation in regions lacking direct solar radiation measurements.