Year: 2026 | Month: March | Volume 19 | Issue 1
Validation of New Version of Hargreaves–Samani Model for Calculating Solar Radiation from Temperature and Humidity Data
J. Ramachandran1 and R. Lalitha2
DOI:10.30954/0974-1712.01.2026.2
Abstract:
The performance of Valiantzas’ new version of Hargreaves–Samani model for calculating solar radiation from temperature and humidity data was validated in a semi-arid region of India. The validation was done by using the meteorological data (2005-14) obtained from a weather station at Agricultural Engineering College and Research Institute, Kumulur, Lalgudi Taluk of Tiruchirapalli district, located in Tamil Nadu, India. The indexes used for comparison are co-efficient of determination (R2), Standard Error Estimate (SEE) and long-term average ratio (rt). It was found that the mean solar radiation estimated from Valiantzas’ new version and Hargreaves–Samani model were higher compared to the measured solar radiation. The comparison showed a good performance (SEE = 4.412 MJ m-2 day-1 and R2 = 0.543) of the proposed new version of solar radiation equation. Hence, researchers can use this model on the basis of available data to getter better results for agricultural water management studies.
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Highlights
- Model Validation: The new version of the Hargreaves-Samani model using temperature and humidity data showed good performance in estimating solar radiation under semi-arid conditions in Tamil Nadu.
- Accurate ET Estimates: Substituting solar radiation values from Valiantzas’ model into FAO56-PM provided reliable reference evapotranspiration estimates with high correlation (R² ≈ 0.959).
- Practical Application: The model is especially useful in regions with limited or unreliable solar radiation data, supporting precision agriculture and water management studies.
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