Assessment of Hargreaves-Samani Model and Valiantzas Model for Estimating Solar Radiation Using Temperature and Humidity Parameters Under Semi-Arid Conditions in India Ramachandran J1, Rajeswari M1, Sankar GR Maruthi2 1Department of Agricultural Engineering, Agricultural College and Research InstituteTamil Nadu Agricultural University, Madurai624104Tamil Nadu, India 2ICAR-Central Research Institute for Dryland Agriculture (CRIDA)Hyderabad500059Telangana, India Email for correspondence: eeesurya.tnau@gmail.com
Online Published on 12 September, 2022. Abstract A newly developed solar radiation model which is a function of temperature and humidity data was validated for Madurai district of Tamil Nadu. The model was developed by including the relative humidity in the temperature- based Hargreaves-Samani radiation model using daily data of 20 years (2000-2019) obtained from weather station located at Agricultural College and Research Institute, Madurai, Tamil Nadu. A comparison has been made between measured solar radiation and the solar radiation obtained from Hargreaves-Samani model (HS Rs [T]) and the newly proposed Valiantzas’ model (Val Rs [T & RH]). The reference evapotranspiration (ET0) was estimated by using FAO56 Penman-Monteith method (FAO56-PM) by substituting the measured solar radiation, HS Rs [T] and Val Rs [T & RH] and a comparison has also been made. The indices used for comparison were coefficient of determination (R2), standard error estimate (SEE) and long term average ratio (rt). Annual mean of HS R [T] was lesser and annual mean of Val Rs [T & RH] was higher compared to the measured solar radiation. When Val Rs [T & RH] was used in the FAO56-Penman-Monteith method, it indicated a good performance (SEE= 2.243 MJ/m2/day, rt= 1.067 and R2= 0.540) in the estimation of reference evapotranspiration. It is suggested that Val Rs [T & RH] model could be used to determine values of solar radiation when the measured data are unavailable in order to get efficient measurements of evapotranspiration for use in the agricultural water management and related studies. Top Keywords Evapotranspiration, FAO56 Penman-Monteith, Solar radiation, Temperature, Relative humidity, Hargreaves-Samani model, Valiantzas’ model. Top |