River levels from multi mission altimetry, a statistical approach

Satellite altimetry is a key technique to measure water level change in continental bodies. Altimetry-based time series of rivers are typically constructed at locations where the satellite ground tracks intersect rivers, so-called virtual stations. The relatively low sampling frequency (10–27 days) repeat missions may result an under-sampling hydrological regime with sub-monthly weekly events. We currently unique position more than handful simultaneously mapping surface elevation Earth. In combination, these contain unexploited potential obtain detailed picture many Earth's rivers. task combining levels measured different and/or by satellites orbits however, challenging due e.g. topography, intermission biases, variation river morphology, and other unidentified causes. this work, we present new method combine multi-mission altimetry-based from reach. This will also enable use geodetic like CryoSat-2 SARAL/AltiKa (after June 2016) series. To data set up state-space model process part first-order autoregressive process. observations as function distance along reach described sum given scaled distance-dependent factor, mean distance, error term. scale factor modeled spline functions. employ for six Lena, Solimões, Mississippi, Danube, Po, Red, which range width 3 km few hundred meters. For each river, consider 200–300 apply CryoSat-2, Sentinel-3A/3B, SARAL/AltiKa. selected must have continuous profile preferable no major tributaries, might alter considerably. length compromise ensuring enough but not violating aforementioned criteria. When validated against situ find root square ranging 0.34 m (Solimões River) 2.53 (Lena correlation 0.83 (Danube 0.99 River). These summary statistics based on approximately 2000–3000 pairs levels. largest increase detail reconstructed Red Rivers, variations under-sampled Po River, can detect sub-weekly events Lena spring flood related ice snowmelt better captured when data. An additional advantage approach that be all considered