Some Experiments in Variational Normal Mode Initialization in Data Assimilation

Abstract

A variational formalism for constrained normal mode initialization has been used in the ANMRC data assimilation scheme. A 5-day data assimilation cycle using FGGE level II data shows that the constrained scheme leads to a significant improvement in the retention of surface pressure information during initialization. The choice of weights is a crucial factor in the constrained initialization used in the study and a compromise has to be made between the level of retention of the mass field and the accompanying loss in wind field information.