Improved water-level forecasting for the Northwest European Shelf and North Sea through direct modelling of tide, surge and non-linear interaction

In real-time operational coastal forecasting systems for the northwest European shelf, the representation accuracy of tide–surge models commonly suffers from insufficiently accurate tidal representation, especially in shallow near-shore areas with complex bathymetry and geometry. Therefore, in conventional operational systems, the surge component from numerical model simulations is used, while the harmonically predicted tide, accurately known from harmonic analysis of tide gauge measurements, is added to forecast the full water-level signal at tide gauge locations. Although there are errors associated with this so-called astronomical correction (e.g. because of the assumption of linearity of tide and surge), for current operational models, astronomical correction has nevertheless been shown to increase the representation accuracy of the full water-level signal. The simulated modulation of the surge through non-linear tide–surge interaction is affected by the poor representation of the tide signal in the tide–surge model, which astronomical correction does not improve. Furthermore, astronomical correction can only be applied to locations where the astronomic tide is known through a harmonic analysis of in situ measurements at tide gauge stations. This provides a strong motivation to improve both tide and surge representation of numerical models used in forecasting. In the present paper, we propose a new generation tide–surge model for the northwest European Shelf (DCSMv6). This is the first application on this scale in which the tidal representation is such that astronomical correction no longer improves the accuracy of the total water-level representation and where, consequently, the straightforward direct model forecasting of total water levels is better. The methodology applied to improve both tide and surge representation of the model is discussed, with emphasis on the use of satellite altimeter data and data assimilation techniques for reducing parameter uncertainty. Historic DCSMv6 model simulations are compared against shelf wide observations for a full calendar year. For a selection of stations, these results are compared to those with astronomical correction, which confirms that the tide representation in coastal regions has sufficient accuracy, and that forecasting total water levels directly yields superior results.     

Tide–surge interactions and their effects on total sea levels in Irish coastal waters

The research presented in this paper involves the application of the joint probability method to the estimation of extreme water levels resulting from astronomical tides and surge residuals and the investigation of the effects of tide–surge interactions on extreme water levels. The distribution of tide peaks was analysed from field records (<20 years) and a 46-year dataset of monthly maximum tidal amplitudes. Large surges were extracted from both field records and a numerical model hindcast covering the 48 largest storm events in the Irish Sea over the period 1959–2005. Extreme storm surges and tides were independently modelled using the generalised extreme value statistical model, and derived probability distributions were used to compute extreme water levels. An important, and novel, aspect of this research is an analysis of tide–surge interactions and their effects on total water level; where interactions exist, they lead to lower total water levels than in the case of independency. The degree of decrease varies with interaction strength, magnitude of surge peak at a particular phase of tide and the distribution of peaks over a tidal cycle. Therefore, including interactions in the computation of extreme levels may provide very useful information at the design stage of coastal protection systems.     

Application of data assimilation for improving forecast of water levels and residual currents in Singapore regional waters

Hydrodynamic models are commonly used for predicting water levels and currents in the deep ocean, ocean margins and shelf seas. Their accuracy is typically limited by factors, such as the complexity of the coastal geometry and bathymetry, plus the uncertainty in the flow forcing (deep ocean tide, winds and pressure). In Southeast Asian waters with its strongly hydrodynamic characteristics, the lack of detailed marine observations (bathymetry and tides) for model validation is an additional factor limiting flow representation. This paper deals with the application of ensemble Kalman filter (EnKF)-based data assimilation with the purpose of improving the deterministic model forecast. The efficacy of the EnKF is analysed via a twin experiment conducted with the 2D barotropic Singapore regional model. The results show that the applied data assimilation can improve the forecasts significantly in this complex flow regime.     

Tactical ethics: How the discourses of Fairtrade and Black Economic Empowerment change and interact in wine networks from South Africa to the UK

This paper explores the spaces and power relations of ethical foodscapes. Ethics can offer a commodity a valuable unique selling point in a competitive marketplace but managing the changeable and multiple motivations for stakeholder participation throughout the commodity chain in order to utilise this opportunity is a complex negotiation. Through exploring the spaces and relations within three South African–UK ethical wine networks, the discursive tactics used to sustain these are uncovered. The discourses of Fairtrade, Black Economic Empowerment and organics are highly adaptive, interacting with each other in such a way as to always be contextually appealing. This ‘tactical mutability’ is combined with ‘scales of knowing’, which, this paper argues, are essential for network durability. ‘Scales of knowing’ refers to the recognition by stakeholders of the potential for different articulations of a discourse within the network, which combines with ‘tactical mutability’ to allow for a scalar, contextual and ’knowing’ (im)mutability to ensure the discourse’s continued appeal. However, even when one discourse is the ‘lead’ it always folds within it linkages to other ethical discourses at work, suggesting that ethical practice is mutually supportive discursively. This means that at the producer end ethical interactions may offer more capacity to enact genuine transformation than the solo operations of a discourse.     

Efficient collection of training data for sub-pixel land cover classification using neural networks

Artificial neural networks (ANNs) are a popular class of techniques for performing soft classifications of satellite images. They have successfully been applied for estimating crop areas through sub-pixel classification of medium to low resolution images. Before a network can be used for classification and estimation, however, it has to be trained. The collection of the reference area fractions needed to train an ANN is often both time-consuming and expensive. This study focuses on strategies for decreasing the efforts needed to collect the necessary reference data, without compromising the accuracy of the resulting area estimates. Two aspects were studied: the spatial sampling scheme (i) and the possibility for reusing trained networks in multiple consecutive seasons (ii). Belgium was chosen as the study area because of the vast amount of reference data available. Time series of monthly NDVI composites for both SPOT-VGT and MODIS were used as the network inputs. The results showed that accurate regional crop area estimation (R² > 80%) is possible using only 1% of the entire area for network training, provided that the training samples used are representative for the land use variability present in the study area. Limiting the training samples to a specific subset of the population, either geographically or thematically, significantly decreased the accuracy of the estimates. The results also indicate that the use of ANNs trained with data from one season to estimate area fractions in another season is not to be recommended. The interannual variability observed in the endmembers’ spectral signatures underlines the importance of using up-to-date training samples. It can thus be concluded that the representativeness of the training samples, both regarding the spatial and the temporal aspects, is an important issue in crop area estimation using ANNs that should not easily be ignored.     

Precise ionosphere-free single-frequency GNSS positioning

Ionospheric delays can be efficiently eliminated from single-frequency data using a combination of carrier phases and code ranges. Unfortunately, GPS and GLONASS ranges are relatively noisy which can limit the use of the positioning method. Nevertheless, position standard deviations are in the range of 6–8 cm (horizontal) and 7–9 cm (3d) obtained from diurnal data batches from selected IGS reference stations can be further reduced to 2–3 cm (3d) for weekly smoothed averages. GPS data sets collected in Ghana (Africa) reveal a typical level of 10 cm of deviation that must be anticipated under average conditions. Looking at the future of GNSS, the European Galileo system will, in contrast to GPS, provide the broadband signal E5 that is by far less affected by multipath thus providing rather precise range measurements. Simulated processing runs featuring both high ionospheric and tropospheric delay variations show a 3d position precision of 4 cm even for a data batch as short as just 1 h, whereas GPS L1/Galileo E1 performance is close to 13 cm for the same data set.     

Multi‐Criteria Analysis for Optimization of Sodium Chromate Production from Chromic Waste

The proposal of application of multi‐criteria analysis and technological quality method for optimization of technological processes on the case study of sodium chromate production variants from waste was presented. The research on the use of chromic waste for the production of sodium chromate made it possible to determine the optimal process parameters. Technological quality method was used to define the value of criterions for multi‐criteria analysis while multi‐criteria analysis allowed determining the impact of criterions weights for ranking variants of technological process. Both methods in a complex way evaluate the degree of modernization of technologies, describing them qualitatively within the area of environmental, technical, and the economic effects of the proposed technological variants. Based on the proposed evaluating criteria both methods yield comparable results. The most advantageous alternatives provided realization of the sodium chromate production process with the use of in‐process recycling of chromic mud, off‐site recycling of chromic tannery waste and on‐site recycling of waste from the old chromic heaps.     

Contrasting variability in foraminiferal and organic paleotemperature proxies in sedimenting particles of the Mozambique Channel (SW Indian Ocean)

Accurate sea surface temperature (SST) proxies are important for understanding past ocean and climate systems. Here, we examine material collected from a deep-moored sediment trap in the Mozambique Channel (SW Indian Ocean) to constrain and compare both inorganic (δ¹⁸O, Mg/Ca) and organic (, TEX₈₆) temperature proxies in a highly dynamic oceanographic setting for application in paleoceanography. High-resolution time-series current velocity data from long-term moorings (2003 - present) deployed across the Mozambique Channel reveal the periodic migration of four to six meso-scale eddies through the channel per year. These meso-scale eddies strongly influence water mass properties including temperature and salinity. Despite the dynamic oceanographic setting, fluxes of the surface-dwelling planktonic foraminifera Globigerinoidesruber and Globigerinoides trilobus follow a seasonal pattern. Temperatures reconstructed from G. ruber and G. trilobus δ¹⁸O and Mg/Ca closely mirror seasonal SST variability and their flux-weighted annual mean SSTs of 28.1 °C and 27.3 °C are in close agreement with annual mean satellite SST (27.6 °C). The sub-surface dwelling foraminifera Neogloboquadrina dutertrei and Globigerinoides scitula recorded high-frequency temperature variations that, on average, reflect conditions at water depths of 50-70 m and 200-250 m, respectively. Concentrations and fluxes of organic compounds (alkenones and crenarchaeol) display no or only moderate seasonality but flux weighted means of the associated temperature signatures, , and of 28.3 °C and 28.1 °C, respectively, also closely reflect mean annual SST. We analyzed all time-series data using multiple statistical approaches including cross-correlation and spectral analysis. Eddy variability was clearly expressed in the statistical analysis of physical oceanographic parameters (current velocity and sub-surface temperature) and revealed a frequency of four to six cycles per year. In contrast, statistical analysis of proxy data from the sediment trap did not reveal a significant coupling between eddy migration and organic compound fluxes or reconstructed temperatures. This is likely a result of the relatively low resolution (21 days) and short (2.5 years) duration of the time series, which is close to the detection limit of the eddy frequency.     

Privacy, reconsidered: New representations, data practices, and the geoweb

Blogging, social networking, and other Web 2.0 practices have sparked widespread debate about the status and future of privacy. This paper examines an explicitly geographical aspect of Web 2.0 with respect to these debates: the geospatial web, or ‘geoweb’. As part of fundamental shifts in the kinds of geographic information available, its circulation, and representative forms it assumes, the geoweb implies new objects of privacy concern and subsequent privacy-related negotiations over the aggregate of its component information, technologies, and data praxes. Thus we argue that privacy must not only be revisited, but indeed re-conceptualized. Whereas prior research on privacy vis-à-vis geographic information technologies has tended to question what privacy ‘is’, we focus instead on the constitutive outcomes of societal struggles over privacy. We examine how privacy is being negotiated around two geoweb services - Google Street View and the Twitter GeoAPI - to illustrate that these contestations produce privacy as a social object in particular ways. We show that public discourse around actual or anticipated privacy harms stemming from geoweb services and their uses, as well as the preventatives and remedies proposed or implemented to address such harms, reconstitute the objects and practices of privacy concern, and alter the roles and relationships of state, civil and corporate actors in the construction of privacy. Finally we suggest that the geoweb raises new privacy concerns because some of its representational forms - namely geo-tagged images and self-authored texts - facilitate identification and disclosure with more immediacy and less abstraction.