Information criteria can help to determine the number of sources from EEG and MEG

A problem with analyzing EEG measurements is the reconstruction of the sources that generate the observed data. Most methods used to solve this problem are based on the assumption that the number of sources is known. Most methods to determine this number are based on the eigenvalues of the covariance matrix of the measured data, the so-called principal components. The assumption is that many of the smaller eigenvalues represent only noise. The decision, where to cut off the spectrum of eigenvalues, is often taken subjectively. Taking into account the properties of the noise, several criteria will be discussed, which allow a more objective choice. The effectiveness of these criteria is assessed by means of computer simulations and the analysis of measurements. Simulations were performed by adding noise to the signals that arise from two rotating current dipoles. The simulations show that the decision which criterion to use, has to be based on the available information about the noise. Besides, it depends on whether overestimation or underestimation of the number of sources would be less harmful. The criteria were also applied to measured data

Effects of wave orbital velocity parameterization on nearshore sediment transport and decadal morphodynamics

Nearshore morphological modelling is challenging due to complex feedback between hydrodynamics, sediment transport and morphology bridging scales from seconds to years.Such modelling is, however, needed to assess long-term effects of changing climates on coastal environments, for example. Due to computational efficiency, the sediment transport driven by currents and waves often requires a parameterization of wave orbital velocities. A frequently used parameterization of skewness-only was found to overfeed the coast unrealistically on a timescale of years—decades. To improve this, we implemented a recently developed parameterization accounting for skewness and asymmetry in a morphodynamic model (Delft3D). The objective was to compare the effects of parameterizations on long-term coastal morphodynamics. We performed simulations with default and calibrated sediment transport settings, for idealized coastlines, and compared the results with measured data from analogue natural systems. The skewness-asymmetry parameterization was found to predict overall stable coastlines within the measured envelope with wave-related calibration factors within a factor of 2. In contrast, the original parameterization required stronger calibration, which further affected the alongshore transport rates, and yet predicted erosion in deeper areas and unrealistic accretion near the shoreline. The skewness-asymmetry parameterization opens up the possibility of more realistic long-term morphological modelling of complex coastal systems