RT - Journal Article T1 - Estimation of Reference Evapotranspiration with Incomplete Data (A Case Study: North Khorasan Province) JF - JSTNAR YR - 2013 JO - JSTNAR VO - 17 IS - 65 UR - http://jstnar.iut.ac.ir/article-1-1730-en.html SP - 211 EP - 221 K1 - Arid and Semi-Arid Climate K1 - FAO-Penman-Monteith K1 - Hargreaves-Samani K1 - Regression. AB - Quantitative evaluation of evapotranspiration on a regional scale is necessary for water resources management, crop production and environmental assessments in irrigated lands. In this study, in order to estimate ETo and because of few synoptic stations and also little recorded meteorological data in North Khorasan Province, Iran, with arid and semi-arid climate, 7 stations from neighboring provinces were used. Reference evapotranspiration was calculated using 6 different methods which required a small amount of input data, including Class A pan, Hargreaves-Samani, Priestly-Tailor, Turc, Makkink and the method proposed by Allen et al (1998) to estimate ETo with missing climate data. Besides, the standard FAO-Penman-Monteith was used (because there was no Lysimetric data in the region) to evaluate the applied formulas. Since there was no agreement over the appropriate method to calculate ETo in the selected stations, by using significance test of regression lines, a linear regression equation was computed for each month, in order to convert the best calculating method to FAO-Penman-Monteith formula. Evaluations of these equations showed their acceptable accuracy, in comparison with the previous researches, specifically for cold months (MAE values ranged from 0.3 to 1.4 mm/day). LA eng UL http://jstnar.iut.ac.ir/article-1-1730-en.html M3 ER -