Near-surface mean circulation and kinetic energy in the central North Atlantic from drifter data

An analysis of a large drifting buoy data set is presented. The objective is to obtain a self‐contained description of the properties of the near‐surface circulation (drogue depth 100 m) in the central North Atlantic Ocean, independent of hydrographic data. A necessary preanalysis step was the removal of all data from undrogued buoys from the data set. The physical parameters of the circulation were deduced by averaging the remaining data in 2°×3° boxes. The minimum amount of data which is necessary to get statistically stable results was determined by an empirical quality criterion. All important mean currents in the investigation area are reproduced by the near‐surface mean velocity field. A separation of the mean velocity field into a nondivergent and an irrational part shows that the flow field is almost nondivergent. The distribution of eddy kinetic energy is concentrated along the mean currents and provides the largest part of the total kinetic energy, but there are regional variations. Energy from inertial movements dominates the high‐frequency part of the kinetic energy. Its distribution is very patchy. The analysis of the Reynolds stress terms shows an energy transfer from the eddy field to the mean circulation in the vicinity of the North Atlantic Current

On the generation and role of eddy variability in the central North Atlantic Ocean: Results from surface drifters satellite altimetry and numerical modelling

Sources of near-surface oceanic variability in the central North Atlantic are identified from a combined analysis of climatology, surface drifter, and Geosat altimeter data as well as eddy-resolving math formula and math formula Community Modeling Effort North Atlantic model results. Both observational and numerical methods give a consistent picture of the concentration of mesoscale variability along the mean zonal flow bands. Three areas of high eddy energy can be found in all observational data sets: the North Equatorial Current, the North Atlantic Current, and the Azores Current. With increasing horizontal resolution the numerical models give a more realistic representation of the variability in the first two regimes, while no improvement is found with respect to the Azores Current Frontal Zone. Examination of the upper ocean hydrographic structure indicates baroclinic instability to be the main mechanism of eddy generation and suggests that the model deficiencies in the Azores Current area are related to deficiencies in the mean hydrographic fields. A linear instability analysis of the numerical model output reveals that instability based on the velocity shear between the mixed layer and the interior is also important for the generation of the mid-ocean variability, indicating a potential role of the mixed layer representation for the model. The math formula model successfully simulates the northward decrease of eddy length scales observed in the altimeter data, which follow a linear relationship with the first baroclinic Rossby radius. An analysis of the eddy-mean flow interaction terms and the energy budget indicates a release of mean potential energy by downgradient fluxes of heat in the main frontal zones. At the same time the North Atlantic Current is found to be supported by convergent eddy fluxes of zonal momentum

The Coastal Observing System for Northern and Arctic Seas (COSYNA)

The Coastal Observing System for Northern and Arctic Seas (COSYNA) was established in order to better understand the complex interdisciplinary processes of northern seas and the Arctic coasts in a changing environment. Particular focus is given to the German Bight in the North Sea as a prime example of a heavily used coastal area, and Svalbard as an example of an Arctic coast that is under strong pressure due to global change. The COSYNA automated observing and modelling system is designed to monitor real-time conditions and provide short-term forecasts, data, and data products to help assess the impact of anthropogenically induced change. Observations are carried out by combining satellite and radar remote sensing with various in situ platforms. Novel sensors, instruments, and algorithms are developed to further improve the understanding of the interdisciplinary interactions between physics, biogeochemistry, and the ecology of coastal seas. New modelling and data assimilation techniques are used to integrate observations and models in a quasi-operational system providing descriptions and forecasts of key hydrographic variables. Data and data products are publicly available free of charge and in real time. They are used by multiple interest groups in science, agencies, politics, industry, and the public

Empowering the User to Build Smart Home Applications

Recent research has shown that end-user programming will form an important part of any general purpose context-aware computing system, since the system behavior of existing context-aware systems does not reflect the situation the end-user intended. This paper is concerned with end-user programming and modification of context-aware application behavior. We present a three-tier approach to build context-aware applications, which separates context collection and distribution from rule-based inference that controls application behavior. Prototypes were created to evaluate our approach. The primary focus was directed towards the rule conflict management and user interface issue, that are related to defining rules. We conclude this paper with a short usability case study based on these prototypes and an outlook into future work