Multi-decadal trends in global terrestrial evapotranspiration and its components

https://www.nature.com/articles/srep19124

Yongqiang Zhang, Jorge L. Peña-Arancibia, Tim R. McVicar, Francis H. S. Chiew, Jai Vaze, Changming Liu, Xingjie Lu, Hongxing Zheng, Yingping Wang, Yi Y. Liu, Diego G. Miralles & Ming Pan

doi:10.1038/srep19124

气候变化；水文学

Published:

11 January 2016

Evapotranspiration (ET) is the process by which liquid water becomes water vapor and energetically this accounts for much of incoming solar radiation. If this ET did not occur temperatures would be higher, so understanding ET trends is crucial to predict future temperatures. Recent studies have reported prolonged declines in ET in recent decades, although these declines may relate to climate variability. Here, we used a well-validated diagnostic model to estimate daily ET during 1981–2012, and its three components: transpiration from vegetation (Et), direct evaporation from the soil (Es) and vaporization of intercepted rainfall from vegetation (Ei). During this period, ET over land has increased significantly (p < 0.01), caused by increases in Et and Ei, which are partially counteracted by Es decreasing. These contrasting trends are primarily driven by increases in vegetation leaf area index, dominated by greening. The overall increase in Et over land is about twofold of the decrease in Es. These opposing trends are not simulated by most Coupled Model Intercomparison Project phase 5 (CMIP5) models, and highlight the importance of realistically representing vegetation changes in earth system models for predicting future changes in the energy and water cycle.

2016年1月，《科学报告》发表的一项研究Multi-decadal trends in global terrestrial evapotranspiration and its components展示了近几十年全球陆地蒸散量及其组成成分的变化趋势。过去的研究表明陆地蒸散量在近几十年间持续减少，然而，新的诊断模型对过去几十年地表蒸散量的推测得到了相反的结果。

蒸散量指的是地表液体水转变为水蒸气的量，同时也反映了地球受到的太阳辐射强度。如果没有蒸散过程，地球的温度将会升高，因此蒸散量对于预测地球温度的变化至关重要。

澳大利亚联邦科学与工业研究组织(CSIRO)的张永强及其同事建立的新诊断模型将陆地蒸散量分为了三个组分：植被蒸散量（Et），植被所拦截降水的蒸散量（Ei）以及土壤蒸散量（Es）。根据新诊断模型对1981-2012年间地球每日蒸散量的模拟，前两者增加的量超过了土壤蒸散所减少的量，使得地球的地表蒸散量总体显著增加。植被叶面积指数（LAI）的升高使得蒸散量的不同组分表现出了相反的变化趋势：Et的增加量大约是Es的减少量的两倍。然而，大部分的CMIP5模型却没有模拟出这样相反的变化趋势。这提醒我们在预测地球能量和水循环变化的过程中，应突出真实反映植被变化的重要性。（来源：科学网）