Abstract: In this note, it is discussed how a coordinate transformation based on semigeostrophic theory can be introduced in a global data assimilation scheme in order to improve the analysis of frontal structures. An expression of ...

Abstract: The use of local spatial averaging to estimate and validate background error covariances has received increasing attention recently, in particular in the context of variational data assimilation for global numerical weather ...

Abstract: The analysis of a frontal discontinuity is difficult as the hypothesis of isotropy commonly assumed by inter- polation schemes is obviously erroneous in that case. Starting from the semigeostrophic theory, the authors ...

Abstract: Real-size assimilation systems basically rely on estimation theory in which two sources of information, background and observations, are combined in an optimal way. However, the optimality of such large problems is not ...