Introduction to Data Assimilation

Data Assimilation (DA) is an add-on module, which can be used in conjunction with the HD and AD modules to guide the simulation towards observed values of either hydrodynamic quantities (level and flow) or AD components.

For an ordinary simulation, the state of the model at some future time is determined by using the model equations to advance the initial state under the influence of the boundary conditions. The model's accuracy at the future state depends on the model design, the quality of the initial condition and on the quality of the boundary conditions. Data assimilation can improve the model accuracy by using observed values to correct the simulated model states.

It must be kept in mind that data assimilation cannot replace a well-designed, calibrated model, it can only adjust the output. If the simulated states are far from the observed, it is a sign that the model is not a good representation of the measurements. Such issues must be addressed before applying data assimilation, by investigating the model design and the calibration.