The atmospheric chemistry dynamics with a convection-diffusion model is studied. The numerical Data Assimilation (DA) algorithm presented is based on the additive-averaged splitting schemes. It carries out "fine-grained" variational data assimilation at separate splitting stages with respect to the spatial dimensions, i.e., the same measurement data are assimilated with different parts of a split model. This design has an efficient implementation due to the direct data assimilation algorithms of the transport process along the coordinate lines.
The objective of this paper is to compare the performance of the algorithm proposed with the one that does the variational data assimilation the splitting model as a whole and requires iterations at every time step.