This is a central workpackage for the proposal. It is composed by a number of activities related to assimilation of radar and satellite data with three different techniques.
Variational Assimilation – Partners 4 and 5 – Implementation of an observation operator for radial winds in 3D-VAR and 4D-VAR for NWP purposes. Projection of the model state on the radar radial wind field. Coding of tangent-linear and adjoint observation operators. In the first phase, emphasis will be on using low elevation radar angles to minimise problems with projection of vertical velocities on radial wind vectors. Algorithms for quality control and ambiguity removal will also be developed and tested. Observation error statistics will be developed by comparison with other available observations (radiosonde data and aircraft wind data) and with model data. The impact of radial wind vectors on NWP forecast quality will be investigated by case studies (severe weather situations) and by Observing System Experiments, i.e. data assimilation and forecast experiments over extended periods with and without use of radar radial wind vectors.
Continuous Assimilation – Partner 7 – Implementation of 4-dimensional continuous assimilation, based on nudging (Newtonian relaxation) for radar, satellite as well as surface and radiosonde data.