A re-evaluation of the threat status of New Zealand's marine invertebrates was undertaken in 2009, following earlier review of New Zealand's Threat Classification System and subsequent refinement of the national criteria for classifying threat of extinction to New Zealand's flora and fauna. Sufficient information was available to enable 295 marine invertebrate taxa to be fully evaluated and assigned to a national threat category. The 10 taxa at most risk of extinction (‘nationally critical’) were the giant seep clam Calyptogena sp., the primitive acorn barnacle Chionelasmus crosnieri, O'Shea's vent barnacle Volcanolepas osheai, the stalked barnacle Ibla idiotica, the four-blotched umbrella octopus Cirroctopus hochbergi, the roughy umbrella octopus Opisthoteuthis chathamensis, the giant squid Idioteuthis cordiformis, the large-egged polychaete Boccardiella magniovata and two gravel maggots, Smeagol climoi and Smeagol manneringi. The key threatening processes identified for marine invertebrates were fishing and land-use associated impacts such as sedimentation. We identified no taxa that had improved in threat status as a result of past or ongoing conservation management action, nor any taxa that had worsened in threat status because of known changes in their distribution, abundance or rate of population decline. We evaluated a small fraction of New Zealand's marine invertebrate fauna for their threat status. Many taxa remain ‘data deficient’ or unlisted. In addition to the most threatened taxa, we recommend these taxa and their habitats as priorities for further survey and monitoring. 相似文献
Probability of occurrence, hazard intensity and encounter probability are key parameters in the quantitative risk analysis (QRA) of landslides. All are strongly dependent on magnitude of the landslides. As a result, magnitude–frequency analysis should be a part of QRA. Deriving representative magnitude–frequency relationships for debris avalanches and debris flows, however, is difficult. One key problem is illustrated with the example of a unique database from the coastal region of British Columbia, Canada, which was compiled entirely from detailed ground investigations. The magnitude of debris avalanches and debris flows is not an independent statistical quantity, but a function of the scale of a given slope, as characterized by the slope length. Thus, attempting to derive probability and magnitude for a given location or sub-region from a regionally-derived magnitude–frequency curve may lead to incorrect predictions. The same problem is pertinent to the application of the same approach to any type of landslide in which the largest combined dimension of the source volume (including entrainment) is of the same order as the length of the slope. It is recommended that greater emphasis be placed on site-specific geological observations, at the expense of generalized statistics. 相似文献
This paper documents an experimental investigation in which a differentially-heated rotating annulus experiment was used to investigate the effects of topography on fluid flow under conditions similar to the atmospheric and oceanic circulation on Earth and other planets. In particular, the relationship between the effects of topographic resonance and the existence and mechanism for generation of low-frequency variability (LFV) were studied, motivated by outstanding questions in works such as Jin and Ghil (J. Atmos. Sci., 1990, 47) and Read and Risch (Geophys. Astrophys. Fluid Dyn., 2011, 105). Whilst employing sinusoidal wavenumber-3 topography a new regime was encountered within a region of stationary wavenumber-3 structural vacillation. Denoted as the “stationary-transition” regime, it featured periodic oscillations between a dominant stationary wavenumber-3 flow and axisymmetric or chaotic flow. Further investigation found that the “stationary-transition” regime appeared to be a near-resonant region where nonlinear topographic resonant instability led to a 23–42 “day” oscillatory behaviour. Within the regime, a Hopf bifurcation sequence was discovered, and the nonlinear instabilities were found to have terms in both wave-zonal flow and wave–wave interactions, including a notable resonant wave-triad. This report summarises the nature of the “stationary-transition” regime, and also makes comparisons with similar regimes of LFV found in other experimental studies, as well as intraseasonal oscillations in the atmosphere. 相似文献
The problem of flow separation around islands is investigated using a dynamically adaptive finite element model to allow for
resolution of the shear layers that form in the advent of separation. The changes in secondary circulation and vertical motion
that occur in both attached and separated flows are documented, as is the degree of closure of the wake eddies. In the numerical
experiments presented, the strongest motion always takes place at the sides of the idealised island, where flow curvature
and shear act together to induce ascent. In contrast, it is the slower motion within the wake eddies that allow streamlines
to extend from the bottom to the surface. We find no evidence for closure of the wake eddies. Rather, all of our separated
experiments show that streamlines that pass through the eddies originate outside of the shear layers and frictional boundary
layers on the upstream side of the idealised island. The numerical experiments demonstrate the potential for dynamically adaptive,
unstructured meshes to resolve the separated shear layers that occur downstream of the idealised island, as well as the narrow
boundary layers that form on the island itself. 相似文献
The analysis of granitic pegmatites still remains a challenge because suitable natural reference materials are scarce or not available. Two new reference materials were prepared at the Smithsonian Institution, to provide an avenue to pursue the geochemical analysis of micas and feldspars in granitic pegmatites: STL-1, the Stewart lepidolite (NMNH 174041) and ZA-1, the Zapot amazonite (NMNH 174042). STL-1 was prepared from lepidolite collected from the lithium-rich Stewart pegmatite, San Diego County, California (33°22'52'N, 117°03'41'W). ZA-1 was prepared from an amazonite from the topaz-bearing Zapot pegmatite, Mineral County, Nevada, (38° 41'N, 118 °33'W). The results of this study indicated that STL-1 and ZA-1 are homogeneous and could be used as reference materials that would allow the expansion of calibration curves in XRF analysis up to 16000 μg g−1 for Rb, 2000 μg g−1 for Cs and 100 μg g−1 for Tl. STL-1 and ZA-1 also contain unusually high concentrations of Ga and Tl, and STL-1 of Nb. 相似文献
We explore the causes and predictability of extreme low minimum temperatures (Tmin) that occurred across northern and eastern Australia in September 2019. Historically, reduced Tmin is related to the occurrence of a positive Indian Ocean Dipole (IOD) and central Pacific El Niño. Positive IOD events tend to locate an anomalous anticyclone over the Great Australian Bight, therefore inducing cold advection across eastern Australia. Positive IOD and central Pacific El Niño also reduce cloud cover over northern and eastern Australia, thus enhancing radiative cooling at night-time. During September 2019, the IOD and central Pacific El Niño were strongly positive, and so the observed Tmin anomalies are well reconstructed based on their historical relationships with the IOD and central Pacific El Niño. This implies that September 2019 Tmin anomalies should have been predictable at least 1–2 months in advance. However, even at zero lead time the Bureau of Metereorolgy ACCESS-S1 seasonal prediction model failed to predict the anomalous anticyclone in the Bight and the cold anomalies in the east. Analysis of hindcasts for 1990–2012 indicates that the model's teleconnections from the IOD are systematically weaker than the observed, which likely stems from mean state biases in sea surface temperature and rainfall in the tropical Indian and western Pacific Oceans. Together with this weak IOD teleconnection, forecasts for earlier-than-observed onset of the negative Southern Annular Mode following the strong polar stratospheric warming that occurred in late August 2019 may have contributed to the Tmin forecast bust over Australia for September 2019.
A stochastic simulation technique was used with ship wave observations, which form the largest world-wide data base of wave information. Twenty years of wave parameter (height, period, and direction) observations from the Comprehensive Ocean–Atmosphere Data Set (COADS) were used as the input data. Simulations were compared to four years of wave parameters from a National Data Buoy Center (NDBC) data buoy near Monterey Bay, CA. The comparisons are satisfactory with differences mainly caused by biases between ship observations and buoy data. The stochastic simulation technique is attractive because it is computationally efficient and few decisions are required for its application. The applied techniques can be employed with global COADS data to simulate wave conditions at many world-wide locations where measurements and hindcasts by computer models do not exist. 相似文献
As the impacts of climate-change on resource-dependent industries manifest, there is a commensurate effort to identify and implement strategies to reduce them. Yet, even when useful knowledge and tools exist, there can be poor adoption of adaptation strategies. We examine the reasons behind sub-optimal adoption of seasonal climate forecasts by graziers for managing climate variability. We surveyed 100 graziers in north-east Queensland, Australia and examined the influence of adaptive capacity, resource-dependency and forecast-perception on uptake. Technical perceptions were not important. Strategic skills, environmental awareness and social capital were. Results suggest that social factors (but not technical factors) are significant. These insights are important for adaptation planning and for maximising the resilience of communities and industries dependent on climate-sensitive resources. 相似文献