EVALUATION AND CALIBRATION OF METHODS ESTIMATING SOLAR RADIATION AND ITS EFFECT ON REFERENCE CROP EVAPOTRANSPIRATION

A. Thanoon, Ahmed.

	EVALUATION AND CALIBRATION OF METHODS ESTIMATING SOLAR RADIATION AND ITS EFFECT ON REFERENCE CROP EVAPOTRANSPIRATION
AL-TAQANI
Article 1, Volume 26, Issue 5, 2013, Pages 0-0
Author
Ahmed. A. Thanoon
Abstract
radiation and their effect on reference crop evapotranspiration in Mosul area . The climatological data are presented for average 30 years 1971-2000 of Mosul station , which include monthly average maximum and minimum temperatures , mean relative humidity, wind speed , sunshine hours, and measured incoming solar radiation . These data are used to calculate monthly solar radiation by Angstrom and Hargreaves equations and reference evapotranspiration ETo by Penman-Monteith equation. The results of estimated monthly solar radiation are listed , plotted and compared with measured solar radiation . The coefficient of determination (R2) and the Root Mean Square Error (RMSE) are calculated . The values of R2 and RMSE are 0.998 and 3.6 MJ m-2 day-1 for Angstrom method and are 0.996 and 4.2 MJ m-2 day-1 for Hargreaves method . The results showed that the method of estimate of solar radiation by the Angstrom formula gave the highest R2 and smallest RMSE and , therefore it is the best way to calculate the solar radiation . But in case of absence measured solar radiation in calculation ETo led to overestimated by 9% for Angstrom and 11% for Hargreaves . The two linear regression equations are used to calibrate the coefficients of Angstrom and Hargreaves methods to Mosul area . The average ETo was 3.39 mm day-1 for measured solar radiation .

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