摘要:全球变暖加剧了气候系统能量和水分循环相互作用的变化，水分平衡变化导致极端旱涝事件频发。地表蒸散是能量水分循环的重要过程，是理解气候变化的关键环节。本文基于1982~2011年FLUXNET-MTE观测资料和ERA-Interim再分析资料，分析了全球干旱半干旱区蒸散的时空变化特征及典型区域的变幅、趋势和季节变化。结果表明：（1）干旱半干旱区多年平均蒸散量小于300 mm。冬季蒸散量最小，夏季最大且变率也最强。1990年代前后，干旱半干旱区蒸散发生了明显的年代际转变，暖季的年代际差异尤为明显。（2）近30年来，东半球干旱半干旱区蒸散量呈增加趋势，西半球呈减小趋势。典型区域来看，南非呈显著增加趋势[25.14 mm（10 a）-1]，美国西南部呈显著减小趋势[-19.86 mm（10 a）-1]；萨赫勒、中国北部和澳大利亚呈增加趋势，阿根廷及智利南部呈减小趋势。（3）蒸散变化与温度、降水的变化联系密切，三者具有相似的年循环变化，但三者间相关性在干旱半干旱区具有显著的差异性。
关键词:蒸散量/
FLUXNET-MTE观测资料/
ERA-Interim再分析资料/
区域对比
Abstract:Global warming has greatly intensified interactions between energy and water cycles in the climate system. Changes in the water balance increase the occurrence of regional floods and droughts. As a key component of energy-water interactions, surface evapotranspiration (ET) is important for understanding climate change. This paper focuses on the spatiotemporal variation of ET across global arid and semi-arid regions, especially its regional differences, using observations (FLUXNET-MTE) and reanalysis (ERA-Interim) dataset during 1982-2011. The results show that:(1) Mean annual ET is less than 300 mm across arid and semi-arid regions. Seasonally, minimum ET appears in winter, while maximum ET and the largest variability both appear in summer. A decadal negative-to-positive happened in the 1990s, which is particularly obvious in warm seasons. (2) At hemispheric scale, the ET variation shows a positive trend in the Eastern Hemisphere, whereas an opposite trend occurs in the western hemisphere in the last 30 years. Regarding those typical regions, ET in South Africa significantly increases by 25.14 mm (10 a)?1, while that in the Southwest U.S. significantly decreases by 19.86 mm (10 a)?1 (both at the confidence level of 99%). Moreover, ET slightly increases in Sahel, northern China and Australia, but slightly decreases in southern Argentina and Chile. (3) The ET variability is coupled with variations of temperature and precipitation with a similar annual cycle. However, the spatial patterns of correlation between ET and temperature/precipitation are heterogeneous across the arid and semi-arid regions.
Key words:Evapotranspiration/
FLUXNET-MTE observations/
ERA-Interim reanalysis/
Regional comparison
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