The Annual and Interannual Variation of Reference Crop Evapotranspiration of Panjin Area

The paper calculated reference crop evapotranspiration (ET0) and analyzed its annual and interannual characteristics of Panjin Area in details based on the FAO56Penman-Monteith formula, and the daily mean meteorological data of fifty years between 1957 and 2006. The results showed that the peak of annual ET0 mainly appeared between May and September, and the curve fluctuated severer and more unstable with the increase of ET0. The interannual variation of ET0 turned to be periodicity with 5 years and the value of it appeared to have a decline trend. The value of interannual ET0 in summer and winter was the largest and the smallest respectively and it in summer turned to be downward trend apparently while it in other seasons turned to be stable trend basically. It provides references for local agriculture development.