Nadine Goris

Four-Dimensional variational assimilation of atmospheric chemical data – application to regional modelling of air quality

The chemistry transport model system EURAD-IM and its variational data assimilation implementation are applied to air quality assessment problems The facility of joint initial value and emission rate optimisation together with a nested 4d-var module is employed to the measurement campaign BERLIOZ To emphasise the benefits of computationally efficient data assimilation for monitoring and simulating air quality, results of an operational 3d-var implementation are also given.

Constraining Projection-Based Estimates of the Future North Atlantic Carbon Uptake

AbstractThe North Atlantic is one of the major sinks for anthropogenic carbon in the global ocean. Improved understanding of the underlying mechanisms is vital for constraining future projections, which presently have high uncertainties. To identify some of the causes behind this uncertainty, this study investigates the North Atlantic’s anthropogenically altered carbon uptake and inventory, that is, changes in carbon uptake and inventory due to rising atmospheric CO2 and climate change (abbreviated as -uptake and -inventory). Focus is set on an ensemble of 11 Earth system models and their simulations of a future with high atmospheric CO2. Results show that the model spread in the -uptake originates in middle and high latitudes. Here, the annual cycle of oceanic pCO2 reveals inherent model mechanisms that are responsible for different model behavior: while it is SST-dominated for models with a low future -uptake, it is dominated by deep winter mixing and biological production for models with a high future ...

Optimization methods for solving bang-bang control problems with state constraints and the verification of sufficient conditions

We consider bang-bang control problems with state inequality constraints. It is shown that the control problem induces an optimization problem where the optimization vector consists of all switching times of the bang-bang control and junction times with boundary arcs. The induced optimization problem is a generalization of the one studied in [1], [19]. [20], [22] for bang-bang controls without state constraints. We develop second order sufficient conditions (SSC) for the state-constrained control problem which require that (1) the SSC for the induced optimization problem are satisfied and (2) additional conditions for the switching function hold at switching and junction times. An optimization algorithm is presented which simultaneously carries out the second-order test. The algorithm is illustrated on a numerical example in cancer chemotherapy.