THE CANADIAN GLOBAL DATA ASSIMILATION SYSTEM - DESCRIPTION AND EVALUATION

A global data assimilation system has been in operation at the Canadia n Meteorological centre (CMC) since March 1991 when it replaced the pr evious hemispheric system. This paper describes the system and present s an evaluation of its performance from several points of view, includ ing the fit of the analyses and short-range forecasts to observations, the relative roles of various components of the system, the functioni ng of some specific subcomponents in a particular case, and the abilit y of the system to represent important aspects of the mean monthly gen eral circulation. This latter part of the evaluation includes comparis ons with the corresponding statistics derived from the analyses of the National Meteorological Center. The global data assimilation system i s found to be functioning well, especially in extratropical regions wi th reasonable data coverage. Problems and weaknesses of the system are discussed.