Development of an operational variational assimilation scheme

The United Kingdom Meteorological Office is developing a variational assimilation for its Unified Model forecast system, which contains a grid-point model, run operationally in global, regional, and mesoscale configurations. Key characteristics of the design are: development path from 3-dimensional to 4-dimensional scheme global and limited area configurations variational analysis of perturbations carefully designed, well conditioned 'background' term This paper describes the variational scheme, with some example results from a simple 2-dimensional variational analysis which has been developed as a prototype.