Geodetic altimeters provide unique observations of the river surface longitudinal profile due to their long repeat periods and densely spaced ground tracks. This information is valuable for calibrating hydraulic model parameters, and thus, for producing reliable simulations of water level for flood forecasting and river management, particularly in poorly instrumented catchments. In this study, we present an efficient calibration approach for hydraulic models based on a steady-state hydraulic solver and CryoSat-2 observations. In order to ensure that only coherent forcing/observation pairs are considered in the calibration, we first propose an outlier filtering approach for CryoSat-2 observations in data-scarce regions using a simulated runoff produced by a hydrologic model. In the hydraulic calibration, a steady-state solver computes the water surface elevation (WSE) profile along the river for selected discharges corresponding to the days of CryoSat-2 overpass. In synthetic calibration experiments, the global search algorithm generally recovers the true parameter values in portions of the river where observations are available, illustrating the benefit of dense spatial sampling from geodetic altimetry. The most sensitive parameters are the bed elevations. In calibration experiments with real CryoSat-2 data, validation performance against both Sentinel-3 WSE and in situ records is similar to previous studies, with Root Mean Square Deviation ranging from 0.43 to 1.14 m against Sentinel-3 and from 0.60 to 0.73 against in situ WSE observations. Performance remains similar when transferring parameters to a one-dimensional hydrodynamic model. Because the approach is computationally efficient, model parameters can be inverted at high spatial resolution to fully exploit the information contained in geodetic CryoSat-2 altimetry.

中文翻译：

---

使用 CryoSat-2 观测在赞比西河流域进行水力模型校准

大地高度计由于其长重复周期和密集间隔的地面轨迹，可以提供对河面纵向剖面的独特观测。该信息对于校准水力模型参数非常有价值，因此对于洪水预测和河流管理的水位模拟非常有价值，尤其是在仪器设备较差的集水区。在这项研究中，我们提出了一种基于稳态水力求解器和 CryoSat-2 观测的水力模型的有效校准方法。为了确保在校准中只考虑相干的强迫/观测对，我们首先提出了一种使用水文模型产生的模拟径流对数据稀缺地区的 CryoSat-2 观测进行异常值过滤的方法。在液压校准中，稳态求解器计算沿河的水面高程 (WSE) 剖面，用于对应于 CryoSat-2 立交桥天数的选定排放。在合成校准实验中，全局搜索算法通常会在可以进行观测的河流部分恢复真实的参数值，这说明了从大地测量高度进行密集空间采样的好处。最敏感的参数是床高。在使用真实 CryoSat-2 数据的校准实验中，针对 Sentinel-3 WSE 和原位记录的验证性能与之前的研究相似，均方根偏差范围为 0.43 到 1.14 m（针对 Sentinel-3，针对 in 的范围从 0.60 到 0.73）现场 WSE 观测。将参数传递到一维流体动力学模型时，性能保持相似。