近61年三峡库区潜在蒸发量时空演变规律及其驱动因素

Spatiotemporal Variability of Evapotranspiration in Recent 61 Years and Its Response to Climate Change in the Three Gorges Reservoir Area

三峡大坝蓄水影响了库区水循环过程,为探析库区潜在蒸发量的变化及其驱动因素,基于FAO56 Penman-Monteith(P-M)公式计算了1959~2019年三峡库区及周边25个气象站的潜在蒸发量。采用累积距平法诊断出1979~1980年三峡库区潜在蒸发量序列发生突变,采用Mann-Kendall法和简单滑动平均法检验了突变前(1959~1979年)、突变后(1980~2002年)及蓄水后(2003~2019年)三个时段的潜在蒸发量变化趋势,并计算了5个气象因子(日照时数、2 m处风速、实际水汽压、气温与太阳辐射)的敏感性系数。结果表明,近61年,潜在蒸发量整体呈下降趋势,线性趋势为-0.71 mm/a,库首处潜在蒸发量明显高于库中和库尾,尤其在秋、冬两季。三峡大坝蓄水后,潜在蒸发量增加趋势显著,库区25个站点的潜在蒸发量增加了41.8 mm,线性趋势为3.31 mm/a。经敏感性分析,太阳辐射和实际水汽压是两个较为敏感的气象因子,大坝蓄水后,风速和实际水汽压的变化是导致潜在蒸发量增加的主要驱动因素。

In order to analyze the variation of potential evaporation and its driving factors in the reservoir area, potential evaporation ET;of 25 meteorological stations in and around the Three Gorges reservoir area from 1959 to 2019 were calculated based on the FAO56 Penman-Monteith(P-M) Method. The sudden change of ET;sequence in the Three Gorges reservoir area during 1979-1980 was diagnosed by using cumulative distance method. The change trend of ET;in three periods before sudden change(1959-1979), after sudden change(1980-2002) and after impounding(2003-2019) was tested by Mann-Kendall method and simple sliding average method. Sensitivity coefficients of five meteorological factors(sunshine hours, wind speed at 2 meters, actual water vapor pressure, air temperature and solar radiation) were calculated. The results show that in recent 61 years, ET;has decreased with a linear trend of 0.71 mm/yr. The ET;at the first place is significantly higher than that at the middle and the end of the reservoir, especially in autumn and winter. After the Three Gorges Dam is impounded, the ET;increase trend is remarkable, the ET;of 25 stations in the reservoir area increases by 41.8 mm, and the linear trend is 3.31 mm/yr. Sensitivity analysis shows that the solar radiation and actual water vapor pressure are two sensitive meteorological factors. Changes of wind speed and actual water vapor pressure are the main driving factors for ET;increase after dam impounding.