| Popis: |
In this study, Fuxin city was taken as example to study Vacillations State features of reference crop evapotranspiration (ET0) in different time scale. Monthly ET0 was calculated based on four meteorological factors daily data of temperature (T), wind speed (WS), relative humidity (RH) and sunshine number (SN) during 1954 to 2006 in the two weather stations of Fuxin and Zhangwu located in Fuxin city using Penman-Monteith formula. EMD method was conducted to analyze Vacillations characteristics. Results showed that: Decreases in oscillation frequency and amplitude was observed, while cycle increased in turn after EMD decomposition of ET0 and four meteorological factors gradually. The rule of IMF changes transformed to liner from non-linear. Maximum contribution rates of T, WS, SN, RH, and ET0, were IMF1 (93.0%), IMF2 (35.0%), IMF2 (64.5%), IMF2 (40.0%) and IMF2 (84.3%). The main oscillation cycles were 1, 0.6, 0.8, 0.7, and 1 year, respectively. Study on ET0 oscillation mode based on EMD method, provided reference for ET0 and a new resolving tool for ET0 study. |
