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A Comparative Study of Correlation Functions for Estimation of Monthly Mean Daily Global Solar Radiation for Jaipur, Rajasthan (India)


  • Department of Physics, University of Rajasthan Jaipur-302 004, India
  • Department of Pure and Applied Physics, University of Kota, Kota-324 005, India


Six empirical correlations have been employed to predict monthly mean global solar radiation on a horizontal surface from relative duration of bright sunshine hours for Jaipur (26.92° N, 75.87° E). These correlations are Angstrom-Prescott linear correlation and modified functions such as quadratic, cubic, exponential, logarithmic and power function of relative duration of sunshine hours. Predicted values of monthly mean global solar radiation were compared with observed values using statistical parameters coefficient of determination R2, mean bias error MBE and root mean square error RMSE. The cubic correlation has been found to be the best while logarithmic correlation is proved worst for Jaipur. The proposed power correlation shows the values of statistical parameters close to cubic correlation and has a simpler form.


Global Solar Radiation, Sunshine Hours, Empirical Correlation, Statistical Parameters

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