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Significant Hazard (significant + hazard)
Selected AbstractsTornado climatology of Canada revisited: tornado activity during different phases of ENSOINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 8 2001David Etkin Abstract Tornadoes are a significant hazard in some parts of Canada, particularly in the southern Prairie provinces and southwestern Ontario, though they are not as common as in some parts of the US. Since the early 1980s, the regional weather offices in Canada have been recording tornado event information on a routine basis, and thus data exists that can be used to update older analyses of tornado frequencies. On average, about 60 tornadoes are reported each year, though many doubtless occur that are not observed or recorded in the Environment Canada records. An analysis of tornado frequencies with El Niño,Southern Oscillation (ENSO) events suggest that the cooler La Niña events tend to suppress tornadic activity, while El Niño events tend to enhance it (though there are exceptions to this trend). Copyright © 2001 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Hazard Reduction in NanotechnologyJOURNAL OF INDUSTRIAL ECOLOGY, Issue 3 2008Lucas Reijnders Summary The release of hazardous substances is a matter of concern for nanotechnology. This may include some nanoparticles, reactants, by-products, and solvents. The use of low-hazard solvents may reduce the hazards from nanoparticle production and nanomaterial processing. The hazards of inorganic nanoparticles may be reduced by modifying their chemical composition, surface characteristics, or structure. In nanomedicine, optimizing the balance between persistence and excretion and preventing the release of toxic degradation products may reduce hazard. In applications of fixed inorganic nanoparticles, the focus should be on preventing the release of such particles and of hazardous compounds during the product life cycle. When, after exhaustion of known hazard reduction options, significant hazard remains, other approaches merit consideration. [source] Observations of downslope winds and rotors in the Falkland IslandsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 605 2005S. D. Mobbs Abstract A field campaign aimed at observing the near-surface flow field across and downwind of a mountain range on the Falkland Islands, South Atlantic, is described. The objective was to understand and eventually predict orographically generated turbulence. The instrumentation was based primarily on an array of automatic weather stations (AWSs), which recorded 30 s mean surface pressure, wind speed and direction (at 2 m), temperature and relative humidity for approximately one year. These measurements were supported by twice-daily radiosonde releases. The densest part of the AWS array was located to the south of the Wickham mountain range, across Mount Pleasant Airfield (MPA). In northerly flow the array provides a detailed study of the flow downwind of the mountain range. The dataset contains several episodes in which the flow downwind of the mountains is accelerated relative to the upwind flow. During some of these episodes short-lived (typically ,1 hour) periods of unsteady flow separation are observed and these are associated with the formation of rotors aloft. Such events present a significant hazard to aviation at MPA. Examination of radiosonde profiles suggests that the presence of a strong temperature inversion at a height similar to the mountain height is a necessary condition for both downwind acceleration and the formation of rotors. The data are used to show that the downwind fractional speed-up is proportional to the non-dimensional mountain height (based on upstream near-surface winds and a depth-averaged Brunt,Väisälä frequency diagnosed from radiosonde data). Similarly, a relationship is established between a quantity that describes the spatial variability of the flow downwind of the mountains and the upstream wind and depth-averaged Brunt,Väisälä frequency. The dependence of the flow behaviour on the Froude number (defined in the usual way for two-layer shallow-water flow) and ratio of mountain height to inversion height is presented in terms of a flow regime diagram. © Royal Meteorological Society, 2005. S. B. Vosper's and P. F. Sheridan's contributions are Crown copyright [source] Numerical simulations of rotors, hydraulic jumps and eddy shedding in the Falkland IslandsATMOSPHERIC SCIENCE LETTERS, Issue 4 2005P. F. Sheridan Abstract High-resolution three-dimensional simulations of flows over East Falkland, South Atlantic, are presented. With a temperature inversion upwind, lee waves, rotors and hydraulic jumps are found to occur, giving rise to highly unsteady phenomena such as wakes and eddy shedding. Such flows are known to represent a significant hazard to aviation. Copyright © 2006 Royal Meteorological Society [source] | ||||||||||