The new data assimilation system at the Italian Air Force Weather Service: design and preliminary results

A new data assimilation system has been designed and implemented at the National Center for Aeronautic Meteorology and Climatology of the Italian Air Force (CNMCA) and it is undergoing testing before eventual operational use. The new system is based on an "observation space" version of the 3D-Var method for the objective analysis component, and on the High Resolution Regional Model (H.R.M) of CNMCA for the prognostic component. New features of the system include completely rewritten correlation functions in spherical geometry, derivation of the objective analysis parameters from a statistical analysis of the innovation increments, introduction of an anisotropic component in the correlation functions, solution of analysis equations by a preconditioned conjugate gradient descent method. The analysis and forecast fields derived from the assimilation system are being subjectively and statistically evaluated through comparisons with parallel runs based on European Centre for Medium Range Weather Forecast (ECMWF): preliminary results of these studies are also presented.