Reference evapotranspiration (ET₀) in the hydrological cycle is one of the processes that is significantly affected by climate change. The Qinghai–Tibet Plateau (QTP) is universally recognized as a region that is sensitive to climate change. In this study, an area elevation curve is used to divide the study area into three elevation zones: low (below 2800 m), medium (2800–3800 m) and high (3800–5000 m). The cumulative anomaly curve, Mann–Kendall test, moving t-test and Yamamoto test results show that a descending mutation occurred in the 1980s, and an ascending mutation occurred in 2005. Moreover, a delay effect on the descending mutation in addition to an enhancement effect on the ascending mutation of the annual ET₀ were coincident with the increasing altitude below 5000 m. The annual ET₀ series for the QTP and different elevation zones showed an increasing trend from 1961 to 2017 and increased more significantly with the increase in elevation. Path analysis showed that the climate-driven patterns in different elevation zones are quite different. However, after the ascending mutations occurred in 2005, the maximum air temperature (Tmax) became the common dominant driving factor for the whole region and the three elevation zones.

中文翻译：

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青藏高原不同海拔参考蒸发量变化和气候驱动模式的差异（1961-2017）

水文循环中的参考蒸散量（ET ₀）是受气候变化影响较大的过程之一。青藏高原是公认的气候变化敏感地区。本研究采用面积高程曲线将研究区划分为三个高程带：低（2800米以下）、中（2800-3800米）和高（3800-5000米）。累积异常曲线、Mann-Kendall 检验、移动 t 检验和 Yamamoto 检验结果显示 1980 年代出现下降突变，2005 年出现上升突变。对年ET ₀上升突变的影响与 5000 m 以下的海拔升高相吻合。青藏高原及不同高程带的年ET ₀系列在1961—2017年间呈增加趋势，且随着海拔的升高增加更为显着。路径分析表明，不同海拔区域的气候驱动模式存在较大差异。但在2005年上升突变发生后，最高气温（Tmax）成为全区和三个高程带共同的主导驱动因素。