拉萨参考作物蒸发蒸腾量的长期年际变化规律及小波分析

Long-term Annual Change Regulation and Wavelet Analysis of Reference Crop Evapotranspiration in Lhasa

根据拉萨气象站1955～2006年逐日气象资料计算出的参考作物蒸发蒸腾量（ET0）的逐年距平值时间序列资料作为分析基础数据，小波分析数据延拓采用对称延拓边界法。结果表明，拉萨年ET0均值年代际距平百分率1950、1970、1980年代为正，1960、1990、2000年代为负，其中最大值在1950年代、最小值在1960年代，说明它们属于异常年代；年ET0均值总体变化趋势呈现递减；在整个时间域内，拉萨年ET0均值变化的年际特征非常明显，主要以3～5年左右周期振动最强，而年代际周期变化非常微弱。

Based on daily weather data in Lhasa from 1955 to 2006, time-series data of annual value anomaly of reference crop evapotranspiration （ ETo ） were calculated as the basis of analysis data, and symmetric extension of the border method was used in data extension of wavelet analysis. The results showed that in Lhasa, the values of interdecadal anomaly percentage, of the annual average daily ETo in 1950s, 1970s and 1980s were positive; while in 1960s, 1990s and 2000s, the values were negative. The maximum value appeared in the 1950s and the mini- mum value appeared in the 1960s, which reflected that these two periods were abnormal; the overall trend of annual average daily ETo showed decreasing; throughout the time region, Lhasa, annual average daily ETo changed in the annual characteristics clearly, the strongest vibration mainly appeared in cycle of three to five years, but the decadal cycle is very. weak.