15 research outputs found
Surface currents in operational oceanography: Key applications, mechanisms, and methods
This paper reviews physical mechanisms, observation techniques and modelling approaches
dealing with surface currents on short time scales (hours to days) relevant for operational
oceanography. Key motivations for this article include fundamental difficulties in reliable
measurements and the persistent lack of a widely held consensus on the definition of surface
currents. These problems are augmented by the fact that various methods to observe and
model ocean currents yield very different representations of a surface current. We distinguish
between four applicable definitions for surface currents; (i) the interfacial surface current, (ii) the
direct wind-driven surface current, (iii) the surface boundary layer current, and (iv) an effective
drift current. Finally, we discuss challenges in synthesising various data sources of surface
currents - i.e. observational and modelling – and take a view on the predictability of surface
currents concluding with arguments that parts of the surface circulation exhibit predictability
useful in an operational context
Turbulence in Rivers
The study of turbulence has always been a challenge for scientists working on geophysical flows. Turbulent flows are common in nature and have an important role in geophysical disciplines such as river morphology, landscape modeling, atmospheric dynamics and ocean currents. At present, new measurement and observation techniques suitable for fieldwork can be combined with laboratory and theoretical work to advance the understanding of river processes. Nevertheless, despite more than a century of attempts to correctly formalize turbulent flows, much still remains to be done by researchers and engineers working in hydraulics and fluid mechanics. In this contribution we introduce a general framework for the analysis of river turbulence. We revisit some findings and theoretical frameworks and provide a critical analysis of where the study of turbulence is important and how to include detailed information of this in the analysis of fluvial processes. We also provide a perspective of some general aspects that are essential for researchers/ practitioners addressing the subject for the first time. Furthermore, we show some results of interest to scientists and engineers working on river flows