Spatiotemporal variability of global river extent and the natural driving factors revealed by decades of Landsat observations, GRACE gravimetry observations, and land surface model simulations
Spatiotemporal variability of global river extent and the natural driving factors revealed by decades of Landsat observations, GRACE gravimetry observations, and land surface model simulations
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DOI：
10.1016/j.rse.2021.112725
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发表时间：
2021-10-11
影响因子：
13.5
通讯作者：
Hong, Yang
中科院分区：
文献类型：
--
作者：
Gao, Shang;Li, Zhi;Hong, Yang
河流是地球陆地水循环中最具活力的组成部分之一，并提供关键的生态系统服务。然而，河流表面范围的时空变异性在很大程度上仍然没有在全球范围内量化。卫星遥感为现场观测提供了一种有希望的替代办法，能够以精细的空间分辨率对全球河流进行更全面的调查和系统分析。该研究结合基于Landsat的全球地表水(GSW)和全球河流宽度(GRWL)数据库的使用，研究了全球河流表面范围的时空变异性及其自然驱动因素。除了检验不同气候带的长期平均河流面积外，我们还进行了统计分析，以将每月河流面积分数时间序列与从重力恢复和气候实验(GRACE)卫星观测和全球陆地数据同化系统(GLDAS)模式模拟获得的陆地水存储(TWS)分量相关联。结果表明，河流水量的时空变异性可以通过气候带的划分得到很好的解释。分析还表明，全球最大河流范围的52.7%被水覆盖的时间不到一半。在中低纬度地区，河流范围的变化与地下水储量高度相关，而在高纬度地区，积雪融化是河流动态的主导因素。通过检验分水河面积的极值，我们发现，分水河面积的突变与赤道、干旱和暖温带地区的降水异常有很好的联系。这项研究为结合光学遥感(Landsat)、重力观测(GRACE)和陆面模拟来研究河流的时空动态提供了一个创新的视角；它突出了低流量产生过程(融雪、入渗和补给-排放)在某些区域控制河流动态的重要作用，这是值得进一步研究的。
Rivers are among the most dynamic components in Earth's terrestrial water cycle and provide critical ecosystem services. Yet, the spatiotemporal variability of river surface extents remains largely unquantified at the global scale. Satellite remote sensing provides a promising alternative to in-situ observations, which can enable a more comprehensive survey and systematic analysis of global rivers at fine spatial resolutions. The study examines the spatiotemporal variability of river surface extent globally and its natural driving factors, by combining the use of Landsat-based Global Surface Water (GSW) and Global River Widths from Landsat (GRWL) databases. In addition to examining the long-term mean river surface extent in various climate zones, we perform statistical analyses to correlate monthly times series of fractional river extent with the terrestrial water storage (TWS) components obtained from the Gravity Recovery and Climate Experiment (GRACE) satellite observation and the Global Land Data Assimilation System (GLDAS) model simulations. Results show that the spatiotemporal variability of water presence in rivers can be explained well via differentiating climate zones. The analysis also shows that 52.7% of the global maximum river extent is covered by water less than half of time. Changes of fractional river extent are found to be highly correlated with groundwater storage in low- and mid-latitudes, whereas snow melting dominates the river dynamics in high latitudes. By examining the extremes of fractional river extent, we found that the abrupt changes of fractional river extent are well linked to precipitation anomalies in the equatorial, arid, and warm temperate areas. This study offers an innovative perspective to study spatiotemporal dynamics of rivers by combining optical remote sensing (Landsat), gravimetry observations (GRACE), and land surface simulations; and it highlights the significant role of low-flow-generating processes (snow melting, infiltration, and recharge-discharge) in controlling river dynamics in certain regions, which warrants future investigation.