filter4dABSTRACT Lappeenranta University of Technology Department of Mathematics and Physics Idrissa S. Amour On Variational Ensemble Kalman Filtering Thesis for the Degree of Master ofABSTRACT Lappeenranta University of Technology Department of Mathematics and Physics Idrissa S. Amour On Variational Ensemble Kalman Filtering Thesis for the Degree of Master of