Current Capabilities
Cryosat-2 Hydrodynamic Modelling: e.g. Brahmaputra
  • Exact orbit repeat 369 days; Sub-cycles of 30 days (Fig. 17).
  • Non-repeat orbit: no virtual station time series and cannot convert altimetry to depth.
  • Daily measurements for about 10 days per sub-cycle. 20 days per sub-cycle without any data. Measurements cascading in downstream direction (Fig. 18). Spatial distance between measurements ≈ 50 km, i.e. measurements proceed slower than a flood wave.
  • Objective to simulate water level everywhere in the river and can thus assimilate any altimetric reading (Fig. 16).
  • Approach based on Saint Venant and Manning equations: Requires accurate river bottom elevation and river cross sections.
  • The hydrodynamic model is non-linear: Ensemble Kalman Filter.
Figure. 17. The Brahmaputra and Cryosat-2 crossings in 30 day sub-cycle
Figure. 18. Schematic of cascading Brahmaputra crossings
Figure 16. Hydrodynamic runs using synthetic Cryosat-2 heights. No data assimilated (upper) and assimilated data (lower). Runs assume: Runoff error (20 %); Altimetry error: 0.3 m. Ensemble size: 20.