A review of operational methods of variational and ensemble‐variational data assimilation

Variational and ensemble methods have been developed separately by various research and development groups and each brings its own benefits to data assimilation. In the last decade or so, various ways have been developed to combine these methods, especially with the aims of improving the background‐error covariance matrices and of improving efficiency. The field has become confusing, even to many specialists, and so there is now a need to summarize the methods in order to show how they work, how they are related, what benefits they bring, why they have been developed, how they perform, and what improvements are pending. This article starts with a reminder of basic variational and ensemble techniques and shows…

• SR
  Sight Research UK

  Award: nceo020004
• NE
  Natural Environment Research Council

  Award: nceo020004
• NC
  National Centre for Earth Observation