Quasi‐continuous variational data assimilation

Abstract

All the computations associated with the operational meteorological data assimilation are usually carried out after the so called cut-off-time, i.e. a few hours after the end of the assimilation period. In this article we propose an alternative implementation of the four-dimensional variational assimilation where some of the computations occur during the 24-hour assimilation period. The feasibility of the approach is first validated with an assimilation system built around a low resolution barotropic grid point model. The results are then confirmed with a multi-level primitive equation model using real observations. The main result of these experiments is that the peak computer power requirement of the four-dimensional variational data assimilation may be significantly reduced by the suggested approach.