Articles | Volume 8, issue 4
Ocean Sci., 8, 587–602, 2012

Special issue: The MyOcean project: scientific advances for operational ocean...

Ocean Sci., 8, 587–602, 2012

Research article 08 Aug 2012

Research article | 08 Aug 2012

Estimation of positive sum-to-one constrained zooplankton grazing preferences with the DEnKF: a twin experiment

E. Simon1,2, A. Samuelsen1,2, L. Bertino1,2, and D. Dumont3 E. Simon et al.
  • 1Nansen Environmental and Remote Sensing Center, Norway
  • 2Bjerknes Center for Climate Research, Norway
  • 3Institut des sciences de la mer, Université du Québec à Rimouski, Canada

Abstract. We consider the estimation of the grazing preferences parameters of zooplankton in ocean ecosystem models with ensemble-based Kalman filters. These parameters are introduced to model the relative diet composition of zooplankton that consists of phytoplankton, small size-classes of zooplankton and detritus. They are positive values and their sum is equal to one. However, the sum-to-one constraint cannot be guaranteed by ensemble-based Kalman filters when parameters are bounded. Therefore, a reformulation of the parameterization is proposed. We investigate two types of variable transformations for the estimation of positive sum-to-one constrained parameters that lead to the estimation of a new set of parameters with normal or bounded distributions. These transformations are illustrated and discussed with twin experiments performed with the 1-D coupled model GOTM-NORWECOM with Gaussian anamorphosis extensions of the deterministic ensemble Kalman filter (DEnKF).