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|Title:||Calibration and Uncertainty Analysis of a Simple Model of Silica-limited Diatom Growth in the Elbe River|
|Authors:||CALLIES Ulrich; SCHARFE Mirco; RATTO MARCO|
|Citation:||ECOLOGICAL MODELLING vol. 213 p. 229-244|
|Publisher:||ELSEVIER SCIENCE BV|
|Type:||Articles in Journals|
|Abstract:||A simple Lagrangian water quality model was designed to investigate the hypothesis of sporadic silica limitations of diatom growth in the lower Elbe river in Germany. For each fluid parcel a limited reservoir of silica was specified to be used up by diatoms. The model¿s simplicity notwithstanding, a set of six selected model parameters could not be fully identified from existing observations at one station. After the introduction of prior knowledge on the ranges of meaningful parameter values, calibration of the over-parameterised model manifested itself primarily in the generation of posterior parameter covariances. Estimations of the covariance matrix based on (a) second-order partial derivatives at the optimum of a quadratic cost function and (b) Monte Carlo simulations that explore the whole space of parameter values gave consistent results. Principal component analysis of the covariance matrix yielded two linear parameter combinations that were most effectively controlled by data from periods with and without lack of silica, respectively. The two parameter combinations were identified as the essential inputs that govern the successful simulation of intermittently decreasing chlorophyll a concentrations in summer. A simulation of the pronounced chlorophyll a minimum in spring, by contrast, was found to be beyond the means of the postulated model structure.|
|JRC Institute:||Institute for the Protection and Security of the Citizen|
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