Assimilation of virtual wide swath altimetry to improve Arctic river modeling
Assimilation of virtual wide swath altimetry to improve Arctic river modeling
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DOI：
10.1016/j.rse.2010.09.008
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发表时间：
2011-02
影响因子：
13.5
通讯作者：
S. Biancamaria;M. Durand;K. Andreadis;P. Bates;A. Boone;N. Mognard;E. Rodríguez;D. Alsdorf;D. Lettenmaier;E. Clark
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文献类型：
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作者：
S. Biancamaria;M. Durand;K. Andreadis;P. Bates;A. Boone;N. Mognard;E. Rodríguez;D. Alsdorf;D. Lettenmaier;E. Clark
全球地表水的变化仍然难以用目前的卫星测量进行监测。未来的地表水和海洋地形使命就是为了解决这个问题。它的主要有效载荷将是一个宽测绘带高度计，可提供120公里测绘带内78°S和78°N之间的水面高程图。本研究的目的是结合联合收割机耦合水文/水力模拟的北极河流与虚拟SWOT观察使用本地集合卡尔曼平滑，以表征河流水深变化。我们假设模型误差仅是由于大气强迫场（降水和气温）的不确定性，并对不同的SWOT轨道进行了测试。首先，我们测试的轨道都有一个三天的重复周期，但不同的空间覆盖范围的研究达到;这些轨道对应的前三个月的使命，这将是专门用于校准和验证实验。对于这些轨道，平均空间均方根误差（RMSE）在建模通道水深下降了29%和79%之间的建模RMSE没有同化相比，根据空间覆盖范围。相应的平均时间RMSE下降在54%和91%之间。然后，我们测试了22天重复周期的标称轨道，这将在使命的剩余寿命期间使用。与三天重复轨道不同，该轨道将在一个重复周期内观测所有大陆表面（南极洲和格陵兰岛北方部分除外）。同化的SWOT观测计算与此标称轨道到水力模型导致的平均空间和时间的RMSE在建模通道水深，分别减少59%和66%。这些结果表明，未来的SWOT使命在陆地表面水文学方面具有巨大潜力，特别是在高纬度地区，在一个轨道重复周期内将进行很好的采样。不过，需要进一步的工作，以减少目前的建模不确定性，并更好地描述SWOT测量误差。
Global surface water variations are still difficult to monitor with current satellite measurements. The future Surface Water and Ocean Topography (SWOT) mission is designed to address this issue. Its main payload will be a wide swath altimeter which will provide maps of water surface elevations between 78°S and 78°N over a 120km swath. This study aims to combine coupled hydrologic/hydraulic modeling of an Arctic river with virtual SWOT observations using a local ensemble Kalman smoother to characterize river water depth variations. We assumed that modeling errors are only due to uncertainties in atmospheric forcing fields (precipitation and air temperature) and different SWOT orbits were tested. First, we tested orbits that all have a three day repeat period but differ in terms of their spatial coverage of the study reach; these orbits correspond to the first three months of the mission, which will be dedicated to calibration and validation experiments. For these orbits, the mean spatial Root Mean Square Error (RMSE) in modeled channel water depth decreased by between 29% and 79% compared to the modeled RMSE with no assimilation, depending on the spatial coverage. The corresponding mean temporal RMSE decrease was between 54% and 91%. We then tested the nominal orbit with a twenty two day repeat period which will be used during the remaining lifetime of the mission. Unlike the three day repeat orbits, this orbit will observe all continental surfaces (except Antartica and the northern part of Greenland) during one repeat period. The assimilation of SWOT observations computed with this nominal orbit into the hydraulic model leads to a decrease of 59% and 66% in the mean spatial and temporal RMSE in modeled channel water depth, respectively. These results show the huge potential of the future SWOT mission for land surface hydrology, especially at high latitudes which will be very well sampled during one orbit repeat period. Still, further work is needed to reduce current modeling uncertainties and to better characterize SWOT measurement errors.