区域蒸散发是一个地区气象和农业生产的重要水分指标。现采用彭曼公式计算潜在蒸散发，研究了北京市1960年—2011年潜在蒸散发及其影响因素的变化趋势，并对研究区潜在蒸散发时间序列变化进行了多尺度周期性分析。研究结果显示，潜在蒸散发线性变化趋势为每年增加0.54 mm，利用Mann-Kendall检验得到区域蒸散发增加趋势不明显，并且无突变点；气温升高，降水量下降导致蒸散发量增加，日照时数下降导致蒸散发量下降；总体上，气温和降水量对北京地区蒸散量影响更大。对北京地区蒸散发进行多尺度周期分析，发现该地区在14a、11-12a、5-6a上存在周期特征，各信号频率分布的时间域及其强度也存在着差异，而且近15年周期特点不同于历史上以往的时期。

Regional evapotranspiration is an important moisture indicator of regional weather and agricultural production. In this paper, the potential evapotranspiration (ET) in Beijing from 1960 to 2011 was calculated using the Penman-Monteith Method recommended by FAO, and the major impact factors of potential ET and their variation trends were investigated. Moreover, the multi-scale and periodic analysis of the time series variation of potential ET was conducted. The results showed that (1) the potential ET increased with a rate of 0.54 mm per year, while the increasing trend was not apparent without mutational point from the Mann-Kendall test; (2) the rising temperature and decreasing precipitation resulted in the increasing in potential ET , while the decreasing sunshine duration led to the reduction of potential ET; and (3) generally, variations of temperature and precipitation had larger effects on potential ET. The multi-scale and periodic analysis of potential ET indicated that the periodic characteristics appeared at the time scales of 14 years, 11 to 12 years, and 5 to 6 years. The time domains and strengths of signal frequency distribution varied, and the periodic characteristics of potential ET in recent 15 years were also different from those in the past.