عنوان مقاله [English]
نویسندگان [English]چکیده [English]
The estimated evapotranspiration of landscape with crop coefficient values should be set up relating with shadow, density modification and regulation of certain plant species which are estimated. Nowadays, according to three coefficients surplus are compared by evapotranspiration landscape plants, it is the problem to accurate calculation crop evapotranspiration of these parameters which are so high, and need high accuracy and will be demanded the using of proper methods. However one of the newest methods of estimating evapotranspiration is using large-scale satellite images which is in this research we would tried to use the satellite images by Sebal models and synoptic stations Mashhad in evapotranspiration rate of landscape (Mashhad Mellat Park). This parameter is with Kimberly Penman (1972), FAO Penman Mantis 56, radiation (FAO 24), Blani Criddle modified, Hargrive Samani, Prystly Taylor, Makking (1957), Turc, and the 24th FAO Penman 1948 Penman method compared with Sebal methods. The values of landscape coefficient obtained in this research have a close relationship with vegetation index and increased together the value of evapotranspiration calculated by Sebal method in warm months is more than calculated in other methods. This research is showed that by using coefficient obtained in Sebal model have showed the better results than Limp model. The Results show that differences between the values of reference evapotranspiration calculated by above methods with Lysimeter data of Ferdowsi University in May. Therefore the results given by the linear regression equation of Laysymetr were closed. Landscape coefficient obtained in this study, is closed relationship with vegetation index and increasing together. Sebal evapotranspiration values method is gram per month type and more than the values calculated by other relationships. This study showed that the using of this model coefficient obtained is better results in Sebal coefficient and better than limp model. These results show that Hargrive, Samani, Blani Criddle and Tork models are less accuracy and against them Prystly and Taylor, radiation and FAO 56 Penman Mantis and FAO are better than other methods and are close to Sebal model data. Therefore, to calculate the evapotranspiration Mashhad landscape or regions with similar climates could be used three methods to set Prystly Taylor, radiation and FAO 56, Penman Mantis models accompany with landscape coefficients which presented in this study.