PowerPoint Presentation - Methods for dealing with spurious covariances arising from small samples in ensemble data assimilation

Flow Dependent Localization (Hodyss and Bishop, QJR)

Ensembles give flow dependent noisy correlations

Stable flow error correlations

Unstable flow error correlations


	Recently, some new algorithms have been proposed to make localization flow dependent.
	When flow is stable, in the atmosphere on can expect the background error correlations to be larger scale (errors are larger scale). When flow is unstable (e.g. lots of small scale turbulence, convection), the errors will also be smaller scale. More sampling error for a finite ensemble in the unstable situation.