Dissipative inertial transport patterns near coherent Lagrangian eddies in the ocean

Recent developments in dynamical systems theory have revealed long-lived and coherent Lagrangian (i.e., material) eddies in incompressible, satellite-derived surface ocean velocity fields. Paradoxically, observed drifting buoys and floating matter tend to create dissipative-looking patterns near oceanic eddies, which appear to be inconsistent with the conservative fluid particle patterns created by coherent Lagrangian eddies. Here we show that inclusion of inertial effects (i.e., those produced by the buoyancy and size finiteness of an object) in a rotating two-dimensional incompressible flow context resolves this paradox. Specifically, we obtain that anticyclonic coherent Lagrangian eddies attract (repel) negatively (positively) buoyant finite-size particles, while cyclonic coherent Lagrangian eddies attract (repel) positively (negatively) buoyant finite-size particles. We show how these results explain dissipative-looking satellite-tracked surface drifter and subsurface float trajectories, as well as satellite-derived \emph{Sargassum} distributions.Comment: Submitted to \emph{Chaos} Focus Issue on Objective detection of Lagrangian Coherent Structures. Revised 23-Feb-1

Lagrangian transport by deep-water surface gravity wavepackets: effects of directional spreading and stratification

The Lagrangian mass transport by non-dissipating surface gravity wavepackets consists of the Stokes drift and the wave-induced return flow. We examine how directional spreading and density stratification affect this mass transport for an isolated non-dissipating wavepacket in deep water using a perturbation expansion. For an unstratified ocean, we show that the net displacement by the return flow is finite, negative, the same at all vertical levels and inversely proportional to the depth for spanwise-infinite packets representing unidirectional (two-dimensional) seas, but zero for spanwise-localised packets representing directionally spread seas (three-dimensional). We resolve this difference by demonstrating that a transition between two-dimensional-like (finite) and three-dimensional-like (zero) displacement occurs on a time scale inversely proportional to the degree of directional spreading. For a stratified ocean, we show that in two dimensions the net displacement profile by the return flow oscillates slowly with depth, with a wavelength dependent on the ratio of buoyancy frequency to the surface wave group velocity, and infinite displacements are predicted when the surface wavepacket resonantly excites internal waves. In three dimensions, the net displacement remains zero in the presence of stratification, but finite-time displacements may be appreciably altered

Solid flux in travelling fluidized bed operating in square-nosed slugging regime

The performance of gas-fluidized bed reactors depends significantly on their hydrodynamics. Among the important properties that dictate the characteristics of a gas-fluidized bed, local solid flux plays a significant role, influencing vital parameters such as bed-to-surface heat exchange and solid circulation rate. Developing techniques that can provide accurate measurements of solid flux is extremely important for: 1) assessing the accuracy of other measurement techniques applicable to industrial units, and 2) validation of CFD models. Comparison of different measurement techniques that provide similar hydrodynamic information is helpful in assessing the errors associated with each methodology. Most measurement techniques for obtaining solid flux in gas-fluidized beds are based on intrusive probes that can simultaneously measure solid velocity and voidage. Previously (1), the novel travelling fluidized bed (TFB) was operated to determine particle velocity from radioactive particle tracking (RPT), positron emission particle tracking (PEPT) and borescopy with silica sand particles of mean diameter 292 μm at superficial gas velocities from 0.4 to 0.6 m/s. In this study, the TFB, operated under identical conditions, was deployed to compare RPT and PEPT for the investigation of solid flux in square-nosed slugging. Both techniques provided solid flux data of the same order, but there were significant quantitative differences. Differing physical properties of tracer particles and the bed material, and differences in the tracer localization techniques are among the factors that contributed to the observed discrepancies. The results provide useful insights on the merits and challenges associated with advanced techniques for measuring solids flux in gas-fluidized beds. REFERENCES S. Tebianian, K. Dubrawski, N. Ellis, R. A. Cocco, R. Hays, S.B.R. Karri, T. W. Leadbeater, D.J. Parker, J. Chaouki, R. Jafari, P. Garcia-Trinanes, J.P.K. Seville, J.R. Grace. Comparison of Particle Velocity Measurement Techniques in a Fluidized Bed Operating in the Square-Nosed Slugging Flow Regime. Powder Technol., 2015. doi:http://dx.doi.org/10.1016/j.powtec.2015.08.040

New chemical engineering provision: Quality in diversity

Recent growth in chemical engineering student numbers has driven an increase in the number of UK universities offering the subject. The implications of this growth are described, along with the different challenges facing new providers in the UK compared with established departments. The approaches taken by the various new entrants are reviewed, with reference to recruitment strategies, infrastructure, the use of external facilities, and the particular flavours of chemical engineering being offered by the new providers. Information about the differentiating features of the large number of chemical engineering degree courses now available is somewhat indistinct: this should be rectified in the interests both of prospective students and of employers. Dilemmas facing new providers include the need to address the fundamentals of the subject as well as moving into more novel research-led areas; enabling students to develop the competencies to sustain them for a whole career as well as meeting immediate employer needs; and providing sufficient industry understanding when academics may lack substantial industrial experience. The central importance of practical provision and of the design project, and the approaches taken by new providers to deliver these components, are reviewed, together with the role of software tools in chemical engineering education, and measures to facilitate industry input into courses. As long as it is not used prescriptively or to inhibit innovation, the accreditation process provides constructive guidance and leverage for universities developing new chemical engineering programmes

Climate warming and increasing Vibrio vulnificus infections in North America

Vibrio vulnificus is an opportunistic bacterial pathogen, occurring in warm low-salinity waters. V. vulnificus wound infections due to seawater exposure are infrequent but mortality rates are high (~ 18%). Seawater bacterial concentrations are increasing but changing disease pattern assessments or climate change projections are rare. Here, using a 30-year database of V. vulnificus cases for the Eastern USA, changing disease distribution was assessed. An ecological niche model was developed, trained and validated to identify links to oceanographic and climate data. This model was used to predict future disease distribution using data simulated by seven Global Climate Models (GCMs) which belong to the newest Coupled Model Intercomparison Project (CMIP6). Risk was estimated by calculating the total population within 200 km of the disease distribution. Predictions were generated for different “pathways” of global socioeconomic development which incorporate projections of greenhouse gas emissions and demographic change. In Eastern USA between 1988 and 2018, V. vulnificus wound infections increased eightfold (10–80 cases p.a.) and the northern case limit shifted northwards 48 km p.a. By 2041–2060, V. vulnificus infections may expand their current range to encompass major population centres around New York (40.7°N). Combined with a growing and increasingly elderly population, annual case numbers may double. By 2081–2100 V. vulnificus infections may be present in every Eastern USA State under medium-to-high future emissions and warming. The projected expansion of V. vulnificus wound infections stresses the need for increased individual and public health awareness in these areas

More than 50 years of successful continuous temperature section measurements by the global expendable bathythermograph network, its integrability, societal benefits, and future

The first eXpendable BathyThermographs (XBTs) were deployed in the 1960s in the North Atlantic Ocean. In 1967 XBTs were deployed in operational mode to provide a continuous record of temperature profile data along repeated transects, now known as the Global XBT Network. The current network is designed to monitor ocean circulation and boundary current variability, basin-wide and trans-basin ocean heat transport, and global and regional heat content. The ability of the XBT Network to systematically map the upper ocean thermal field in multiple basins with repeated trans-basin sections at eddy-resolving scales remains unmatched today and cannot be reproduced at present by any other observing platform. Some repeated XBT transects have now been continuously occupied for more than 30 years, providing an unprecedented long-term climate record of temperature, and geostrophic velocity profiles that are used to understand variability in ocean heat content (OHC), sea level change, and meridional ocean heat transport. Here, we present key scientific advances in understanding the changing ocean and climate system supported by XBT observations. Improvement in XBT data quality and its impact on computations, particularly of OHC, are presented. Technology development for probes, launchers, and transmission techniques are also discussed. Finally, we offer new perspectives for the future of the Global XBT Network

Tracking the impacts of climate change on human health via indicators: lessons from the Lancet Countdown

Background: In the past decades, climate change has been impacting human lives and health via extreme weather and climate events and alterations in labour capacity, food security, and the prevalence and geographical distribution of infectious diseases across the globe. Climate change and health indicators (CCHIs) are workable tools designed to capture the complex set of interdependent interactions through which climate change is affecting human health. Since 2015, a novel sub-set of CCHIs, focusing on climate change impacts, exposures, and vulnerability indicators (CCIEVIs) has been developed, refined, and integrated by Working Group 1 of the “Lancet Countdown: Tracking Progress on Health and Climate Change”, an international collaboration across disciplines that include climate, geography, epidemiology, occupation health, and economics. / Discussion: This research in practice article is a reflective narrative documenting how we have developed CCIEVIs as a discrete set of quantifiable indicators that are updated annually to provide the most recent picture of climate change’s impacts on human health. In our experience, the main challenge was to define globally relevant indicators that also have local relevance and as such can support decision making across multiple spatial scales. We found a hazard, exposure, and vulnerability framework to be effective in this regard. We here describe how we used such a framework to define CCIEVIs based on both data availability and the indicators’ relevance to climate change and human health. We also report on how CCIEVIs have been improved and added to, detailing the underlying data and methods, and in doing so provide the defining quality criteria for Lancet Countdown CCIEVIs. / Conclusions: Our experience shows that CCIEVIs can effectively contribute to a world-wide monitoring system that aims to track, communicate, and harness evidence on climate-induced health impacts towards effective intervention strategies. An ongoing challenge is how to improve CCIEVIs so that the description of the linkages between climate change and human health can become more and more comprehensive

Tracking the impacts of climate change on human health via indicators: lessons from the Lancet Countdown

Background: In the past decades, climate change has been impacting human lives and health via extreme weather and climate events and alterations in labour capacity, food security, and the prevalence and geographical distribution of infectious diseases across the globe. Climate change and health indicators (CCHIs) are workable tools designed to capture the complex set of interdependent interactions through which climate change is affecting human health. Since 2015, a novel sub-set of CCHIs, focusing on climate change impacts, exposures, and vulnerability indicators (CCIEVIs) has been developed, refined, and integrated by Working Group 1 of the “Lancet Countdown: Tracking Progress on Health and Climate Change”, an international collaboration across disciplines that include climate, geography, epidemiology, occupation health, and economics. Discussion: This research in practice article is a reflective narrative documenting how we have developed CCIEVIs as a discrete set of quantifiable indicators that are updated annually to provide the most recent picture of climate change’s impacts on human health. In our experience, the main challenge was to define globally relevant indicators that also have local relevance and as such can support decision making across multiple spatial scales. We found a hazard, exposure, and vulnerability framework to be effective in this regard. We here describe how we used such a framework to define CCIEVIs based on both data availability and the indicators’ relevance to climate change and human health. We also report on how CCIEVIs have been improved and added to, detailing the underlying data and methods, and in doing so provide the defining quality criteria for Lancet Countdown CCIEVIs. Conclusions: Our experience shows that CCIEVIs can effectively contribute to a world-wide monitoring system that aims to track, communicate, and harness evidence on climate-induced health impacts towards effective intervention strategies. An ongoing challenge is how to improve CCIEVIs so that the description of the linkages between climate change and human health can become more and more comprehensive