[8-1] Invited

Scale-dependent ensemble covariance localization for EnVar data assimilation

M. Buehner (Environment Canada), and Anna Shlyaeva (Environment Canada)

An approach is presented for efficiently applying scale-dependent spatial covariance localization within an EnVar data assimilation system. More severe localization is applied to small scales and less localization to large scales within the same single analysis procedure. It will be shown that such an approach leads necessarily to a reduction in the between-scale corrections. The approach is motivated by the challenge of assimilating all available observations in future high-resolution global NWP systems to simultaneously correct all scales resolved by the model and observations (i.e. from global scales down to convective scales). This is in contrast with most current operational systems that focus on either correcting only the relatively large scales or only the small scales. Examples will be given using an idealized 1-D system and a simple 2-D sea ice data assimilation system.