بررسي روند تغييرات سري زماني تبخير- تعرق ماهيانه گياه مرجع با استفاده از روش پيشنهادي فائو پنمن- مانتيس

Time trend analysis monthly reference evapo-transpiration by using of recommendation FAo-Penman-Monteith method

One of the management optimal water consume in farm, is accurate estimation plant water demand and how lime trend reference evapo-transpiration study and research reference evapo transpiration for considering interest cultivation pattern and optimization by water resources is necessary in future. On basis of country expansion. varieVy time trend reference evapo transpiration and a few inquiries the subject, research the parameter time trend analysis is very necessary and it is the main purposes. After the collecting statistics and data 33 synoptic stations with record lengths 40 year to calculated reference evapo-traspiration to FAo-Penman-Monteith method, and time trend the parameter in monthly scale for every station in 2 record lengths time (40 years) and short time (20 years) to be calculate by slope line trend meaningful test and Spcarmans Rank correlation.In short, predicate that record lengths 40 years in average 38% of station have positive trend and 62% have been negative trend, and in record lengths 20 years, 62.5% have been positive trend and 37.5r^ have been negative trend, that with decrease record lengths deducted of levels negative trend and is increased to positive trend. Also, in record lengths 40 year, reference evapo transpiration in April was more than 60% stations have positive trend and in March, October. November months was more than 75% stations have negative trend but. in record lengths 20 years, in many of year, reference evapo-transpiration was more than 60c/i stations have increased trend