Abstract
Abstract. This paper presents the application of the Linear Quadratic Optimal Control (LQOC) method to a parameter optimization problem for a one-dimensional marine ecosystem model of NPZD (N for dissolved inorganic nitrogen, P for phytoplankton, Z for zooplankton and D for detritus) type. This ecosystem model, developed by Oschlies and Garcon, simulates the distribution of nitrogen, phytoplankton, zooplankton and detritus in a water column and is driven by ocean circulation data. The LQOC method is used to introduce annually periodic model parameters in a linearized version of the model. We show that the obtained version of the model gives a significant reduction of the model-data misfit, compared to the one obtained for the original model with optimized constant parameters. The found inner-annual variability of the optimized parameters provides hints for improvement of the original model. We use the obtained optimal periodic parameters also in validation and prediction experiments with the original non-linear version of the model. In both cases, the results are significantly better than those obtained with optimized constant parameters.
Highlights
In this paper we present an application of the LQOC (Linear Quadratic Optimal Control) method on a parameter optimization in a marine ecosystem model
The ql are the biogeochemical coupling terms which depend on space and time via light intensity and on temperature, and on most of the parameters summarized in the vector u. In this spatially one-dimensional setting, the only physical process taken into account is vertical diffusion, which appears as a space and time-dependent mixing coefficient κ, taken from the Ocean Circulation and Climate Advanced Model OCCAM in hourly profiles
We use the method of linear quadratic optimal control (LQOC) to determine optimal periodic parameters in a one-dimensional marine ecosystem model
Summary
The model used here, as example, is a one-dimensional marine ecosystem model presented in Oschlies and Garcon (1999) It is of NPZD type, i.e., it simulates the interaction of dissolved inorganic nitrogen (N), phytoplankton (P), zooplankton (Z) and detritus (D), whose concentrations (in mmol N m−3) are denoted by the model variables (yl)l=N, P, Z, D =: y. The ql are the biogeochemical coupling terms which depend on space and time via light intensity and on temperature, and on most of the parameters summarized in the vector u In this spatially one-dimensional setting, the only physical process taken into account is vertical diffusion, which appears as a space and time-dependent mixing coefficient κ, taken (as well as temperature) from the Ocean Circulation and Climate Advanced Model OCCAM (see Sinha and Yool, 2006) in hourly profiles. For more details see Schartau and Oschlies (2003a)
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