QUASI-CONTINUOUS VARIATIONAL DATA ASSIMILATION

All the computations associated with the operational meteorological da ta assimilation are usually carried out after the so called cut-off-ti me, i.e. a few hours after the end of the assimilation period. In this article we propose an alternative implementation of the four-dimensio nal variational assimilation where some of the computations occur duri ng the 24-hour assimilation period. The feasibility of the approach is first validated with an assimilation system built around a low resolu tion barotropic grid point model. The results are then confirmed with a multi-level primitive equation model using real observations. The ma in result of these experiments is that the peak computer power require ment of the four-dimensional variational data assimilation may be sign ificantly reduced by the suggested approach.