1980—2020年中国九大流域蒸散发及其组分时空评估

蒸散发是地表陆气水分交换的纽带,准确量化蒸散发的时空演变格局对于水资源规划与管理至关重要。本文基于GLEAM模型的蒸散发及其组分数据集,借助7个通量观测站数据、120个流域的流域水量平衡及PML_V2蒸散发产品,在中国九大流域系统评估了GLEAM-ET产品,分析了植被恢复背景下,蒸散发（ET）及其组分（植被蒸腾Ec,截留蒸发Ei,土壤蒸发Es）在1980—2020年的时空演变格局。本文主要得到以下结论：① GLEAM-ET产品在中国九大流域具有较好的适用性,其性能与气候类型有关,干旱区效果优于湿润区。此外,GLEAM与PML_V2模型在九大流域相关性较好（R>0.7）,分布格局与变化趋势整体保持一致。② 全国尺度上,ET均值为416.88 mm,增长速率为1.21 mm/a。Ec与ET均呈自东南向西北递减的分布格局,而Es与其相反。Ec、ET在九大流域均呈显著增加趋势（p<0.001）。Ei、Es在季风区流域分别呈显著增加和显著减小趋势;在内陆区流域呈不显著减小（p>0.05）和显著增加趋势。③在植被恢复背景下,ET组分比例发生了变化。Ec占比变化存在南北差异,南方流域Ec占比均减小,北方流域均增加。Ei占比在各流域均增加,Es占比均减小。黄河流域ET组分对植被恢复的响应最为明显,Ec占比增加了5.21%,Es占比减小了5.56%。

Spatial-temporal Dynamics of Evapotranspiration and Its Components in Nine River Basins of China from 1980 to 2020 based on GlEAM-ET Products

Evapotranspiration (ET) is the link of water exchange between land surface and atmosphere, and has an important effect on the water cycle and energy cycle. In the context of climate change and increasing anthropogenic activities, significant changes in ET have been detected over past decades, which has profoundly impacted the global water cycle system and climate system. Thus, accurate estimation of spatiotemporal variability of ET and its components under a changing environment is essential for water resources planning and management. In this paper, we used the GLEAM-ET dataset to investigate the spatial-temporal dynamics of ET and its components in nine river basins of China. The applicability of the GLEAM model is verified at multiple scales in China based on ET observations at 7 flux sites, ET_water based on water balance principle in 120 basins and the PML_V2 evapotranspiration product. The spatial and temporal patterns of ET and its components (i.e., vegetation transpiration Ec, retained evapotranspiration Ei, and soil evapotranspiration Es) are comprehensively analyzed in the context of revegetation. The results show that: (1) The GLEAM-ET product has a good applicability in nine major river basins in China, and its performance is related to the climate zone. The applicability in arid areas is better than that in humid areas. In addition, the GLEAM and PML_V2 models have a good correlation in nine major watersheds (R>0.7), and their distribution pattern and change trend are consistent overall; (2) From 1980 to 2020, the average ET of China is 416.88 mm, and the growth rate is 1.21 mm/yr. Both Ec and ET show a decreasing pattern from southeast to northwest, while Es shows a reverse trend. The Ec and ET show a significant increasing trend in the 9 major watersheds (p<0.001). The Ei and Es show a significant increase and decrease in the monsoon watersheds, respectively, and an insignificant decrease (p>0.05) and a significant increase trend in inland watersheds, respectively; (3) The proportion of each ET component obviously changes under the background of vegetation restoration. The change of Ec proportion is different from north to south. The Ec proportion decreases in the southern basin and increases in the northern basin. The proportion of Ei and Es increases and decreases, respectively, over all basins. The ET components in the Yellow River Basin respond most obviously to vegetation restoration, with Ec increasing by 5.21% and Es decreasing by 5.56%. These findings will help to provide guidance for water resource management and planning the formulation of ecological restoration policies on the Loess Plateau.