Near-daily monitoring of surface temperature and channel width of the six largest Arctic rivers from space using GCOM-C/SGLI

[摘要] 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.

[发布日期] 2021-09-15

[关键词] River surface temperature;Channel width;Discharge;Arctic;GCOM-C;SGLI;Thermal infrared