Glossary
Hargreaves-Samani Method
A temperature-only method that estimates reference evapotranspiration from maximum and minimum air temperature plus extraterrestrial radiation (derived from latitude and date), without needing humidity or wind data.
Hargreaves-Samani is a useful fallback when only temperature data are available. It is less accurate than fuller methods such as Penman-Monteith, especially in humid or very windy conditions, but is valued for its minimal data requirements.