Near-daily monitoring of surface temperature and channel width of the six largest Arctic rivers from space using GCOM-C/SGLI
Near-daily monitoring of surface temperature and channel width of the six largest Arctic rivers from space using GCOM-C/SGLI
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DOI：
10.1016/j.rse.2021.112538
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发表时间：
2021-09
影响因子：
13.5
通讯作者：
M. Hori
中科院分区：
文献类型：
--
作者：
M. Hori
北极河流水温和流量的时空变化是需要观测的重要变量，不仅可以用于估算大陆融雪、降雨和永久冻土融化的径流贡献，还可以评估其对北极海冰和海洋生态系统的影响。然而，自20世纪以来，由于维护现场监测站的预算缩减，地下水监测站的数量以及温度和流量的现场测量频率一直在减少。在这项研究中，我们探索了使用名为 SGLI 的日本星载光学传感器从太空对河流表面温度 (RST) 和河道宽度 (RCW) 进行近日常监测的可能性，该传感器可以在全球范围内以 250 米的相同空间分辨率观测从近紫外到热红外区域的光谱带的辐射率。使用 SGLI TIR 波段测量的河流表面亮温 (RSBT) 作为未经大气校正的 RST。 RCW 是使用可见光到短波红外波段的 SGLI 反射率沿河道识别的水像素的宽度。对2018年和2019年获取的两年SGLI数据的分析结果表明，应用时空插值后，可以从每天的SGLI观测中成功反演RSBT和RCW。使用插值法评估的原位水温检索的 RSBT 精度约为 2.57 K（无插值法但观测频率较低的情况下为 1.84 K）。检索到的 RCW 与原位河流水流量密切相关，表明不仅可以评估雪融水的变化，还可以评估流域内降水的变化。因此，SGLI数据不仅可以用来重建河水温度，还可以重建大陆河道沿线的河水流量，以评估流入北冰洋的热通量。
Spatio-temporal changes in water temperature and discharge of the Arctic rivers are important variables to be observed not only for estimating runoff contributions from snow melt, rainfall, and thawing of permafrost over the continents but also for assessing their impacts on the Arctic sea-ice and marine ecosystem. Nevertheless, the number of ground water gauging stations and the frequency of in-situ measurements for temperature and discharge has been decreasing since the 20 Century due to the shrinkage of budgets for maintaining the in-situ stations. In this study, we explored the possibility to perform near-daily monitoring of river surface temperature (RST) and river channel width (RCW) from space using a Japanese satellite-borne optical sensor named SGLI which can observe radiances at the spectral bands from near-ultraviolet to thermal infrared regions at the same spatial resolution of 250-m on a global scale. River surface brightness temperature (RSBT) measured with SGLI TIR band was used as RST without atmospheric correction. RCW was derived as the widths of water pixels identified along river channels using SGLI reflectances at visible to shortwave infrared bands. Analysis results of two-year SGLI data acquired in 2018 and 2019 show that RSBT and RCW can be retrieved successfully from the SGLI observations on a daily basis after applying a spatio-temporal interpolation. The accuracies of the retrieved RSBT evaluated with in-situ water temperatures are about 2.57 K with the interpolation (and 1.84 K without the interpolation but with lower observation frequencies). Retrieved RCWs are correlated well with in-situ river water discharges indicating potentials to assess variations of not only snow melt water but also precipitation within the river basin. Thus, SGLI data can be used to reconstruct not only the river water temperature but also the river water discharges along the continental river channels for assessing heat flux flowing into the Arctic Ocean.