Evaluation of Different Radiation and Humidity Methods for Estimation of ETo and Analysis of Aridity Effects in Golestan Province

Document Type : Research Paper

Authors

1 ‍Ph .D. student in Irrigation Tarbiat Modarres University

2 scientific staff member, School of Agriculture, Ferdowsi University, Mashad

3 scientific staff member, School of Agriculture, Tarbiat Modarres University, respectively

Abstract

Reference evapotranspiration (ETo) is a term used for a grass/alfalfa medium under no-stress condition. ETo can be measured in lysimeters or estimated by the empirical equations. Due to lack of lysimetric data in Golestan province and taking FAO-Penman-Monteith (F-P-M) as a standard method, the radiation and humidity methods were compared with this standard method in synoptic stations of Golestan Province (Gorgan, Gonbad and Marave-Tappeh). In this evaluation, the data used were either raw data or corrected based on local and/or universal conditions. The results showed the accuracy order for these methods to follow the sequence Makkink, Turc, Jensen-Haise and radiation. The results also showed that Gorgan and Gonbad stations did not need any aridity correction, while the Maraveh-Tappeh had to be corrected. When estimated ETo values from radiation methods (e.g. J-H in Maraveh-Tappeh) were corrected by regression equation, the amounts obtained for these methods were applicable in Golestan. The humidity methods were not useful in Golestan, unless they were corrected by suitable regression equations in Gorgan and Gonbad stations.

Keywords

References

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Iranian Journal of Soil Research
Volume 19, Issue 2
November 2005
Pages 275-285

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