Investigating the uncertainty of satellite altimetry products for hydrodynamic modelling

Satellite altimetry products are increasingly used in many hydraulic applications, and recent studies demonstrate their suitability for the calibration of hydraulic models. The study investigates the effect of satellite-data uncertainty on the calibration of a quasi-two-dimensional (quasi-2D) model of the middle-lower portion of the Po river (~140km). We refer to extended (~16years of observations) ERS and ENVISAT altimetry products (i.e. River and Lake Hydrology data, RLH) to investigate the effect of (i) record length (i.e. number of satellite measurements at a given satellite track) and (ii) data uncertainty (i.e. altimetry measurements errors) on the calibration of the quasi-2D model. We first present an assessment of ERS and ENVISAT altimetry errors and then perform the investigations in a Monte Carlo framework by generating datasets of synthetic altimetry products. The results of our analysis further emphasize the suitability of satellite data for the calibration of hydraulic models, providing also a quantitative assessment of the effect of the uncertainty of altimetry products. The analysis highlights the higher accuracy of ENVISAT data, which ensures a stable calibration with ~1.5years of data (Mean Absolute Error, MAE, lower than 0.4m, ~0.2m of which results directly from the uncertainty of ENVISAT data). ERS-based calibrations become stable with longer series (~3.5-5years of data), and the negative effect of uncertainty in ERS data is higher (i.e. MAE of 0.6-0.9m, of which 0.4-0.6m results from the uncertainty of ERS measurements).