Open-boundary conditions for open-coast hurricane storm surge

Harper, B.A. and Sobey, R.J., 1983. Open-boundary conditions for open-coast hurricane storm surge. Coastal Eng., 7: 41–60.The specification of realistic open-boundary conditions for the numerical simulation of hurricane (or tropical cyclone) storm surge is considered in the context of the very considerable spatial extent of the meteorological forcing. Existing practice is reviewed and an alternative approach, a Bathystrophic Storm Tide approximation to open-boundary water levels, is presented. Results from a series of numerical experiments demonstrate the advantages of this approach over existing methods.     

Effects of observed and experimental climate change on terrestrial ecosystems in northern Canada: results from the Canadian IPY program

Tundra and taiga ecosystems comprise nearly 40?% of the terrestrial landscapes of Canada. These permafrost ecosystems have supported humans for more than 4500?years, and are currently home to ca. 115,000 people, the majority of whom are First Nations, Inuit and Métis. The responses of these ecosystems to the regional warming over the past 30?C50?years were the focus of four Canadian IPY projects. Northern residents and researchers reported changes in climate and weather patterns and noted shifts in vegetation and other environmental variables. In forest-tundra areas tree growth and reproductive effort correlated with temperature, but seedling establishment was often hindered by other factors resulting in site-specific responses. Increased shrub cover has occurred in sites across the Arctic at the plot and landscape scale, and this was supported by results from experimental warming. Experimental warming increased vegetation cover and nutrient availability in most tundra soils; however, resistance to warming was also found. Soil microbial diversity in tundra was no different than in other biomes, although there were shifts in mycorrhizal diversity in warming experiments. All sites measured were sinks for carbon during the growing season, with expected seasonal and latitudinal patterns. Modeled responses of a mesic tundra system to climate change showed that the sink status will likely continue for the next 50?C100?years, after which these tundra systems will likely become a net source of carbon dioxide to the atmosphere. These IPY studies were the first comprehensive assessment of the state and change in Canadian northern terrestrial ecosystems and showed that the inherent variability in these systems is reflected in their site-specific responses to changes in climate. They also showed the importance of using local traditional knowledge and science, and provided extensive data sets, sites and researchers needed to study and manage the inevitable changes in the Canadian North.     

Multi-Source Emission Determination Using an Inverse-Dispersion Technique

Inverse-dispersion calculations can be used to infer atmospheric emission rates through a combination of downwind gas concentrations and dispersion model predictions. With multiple concentration sensors downwind of a compound source (whose component positions are known) it is possible to calculate the component emissions. With this in mind, a field experiment was conducted to examine the feasibility of such multi-source inferences, using four synthetic area sources and eight concentration sensors arranged in different configurations. Multi-source problems tend to be mathematically ill-conditioned, as expressed by the condition number κ. In our most successful configuration (average κ = 4.2) the total emissions from all sources were deduced to within 10% on average, while component emissions were deduced to within 50%. In our least successful configuration (average κ = 91) the total emissions were calculated to within only 50%, and component calculations were highly inaccurate. Our study indicates that the most accurate multi-source inferences will occur if each sensor is influenced by only a single source. A “progressive” layout is the next best: one sensor is positioned to “see” only one source, the next sensor is placed to see the first source and another, a third sensor is placed to see the previous two plus a third, and so on. When it is not possible to isolate any sources κ is large and the accuracy of a multi-source inference is doubtful.     

The Upper Oligocene of Antigua: the volcanic to limestone transition in a limestone Caribbee

Antigua is a small island at the northern end of the Lesser Antilles chain. Its geology is largely limited to the Upper Oligocene and it records with unusual fidelity the transition from island arc volcanism to quiescence and limestone deposition. Despite the apparent limitation of a rock record confined to a short stratigraphical interval, Antigua has a geodiversity that ranges from thick andesites through silicified logs and freshwater snails in cherts to limestones that include both shallow and deeper water facies, and fine karstic features.     

A radar transparent layer in a temperate valley glacier: Bench Glacier,Alaska

Radar surveys of Bench Glacier, Alaska, collected over five field seasons between 2002 and 2006 reveal a surface layer of radar transparent ice in this temperate valley glacier. The transparent layer covers the up‐glacier half of the ablation zone and is defined by a distinct lack of the radar scattering events considered typical of temperate ice. Radar scattering ice underlies the transparent zone, and extends to the surface elsewhere on the glacier. We observed the layering in constant offset radar surveys conducted with characteristic frequencies ranging from 5 MHz to 100 MHz. The radar transparent layer extends from the surface to 20 m depth on average, but up to 50 m in some places. Bench Glacier's transparent layer appears similar to the cold surface layer of polythermal glaciers, however, observations in over 50 boreholes on Bench Glacier suggest there is no cold ice corresponding to the radar transparent layer. We conclude that spatially extensive radar‐transparent layers normally used to identify cold ice in polythermal glaciers are present in some temperate glaciers. Copyright © 2009 John Wiley & Sons, Ltd.     

Far-infrared and submillimeter brightness temperatures of the giant planets

We have measured the brightness temperatures of Jupiter, Saturn, Uranus, and Neptune in the range 35 to 1000 μm. The effective temperatures derived from the measurements, supplemented by shorter wavelength Voyager data for Jupiter and Saturn, are 126.8 ± 4.5, 93.4 ± 3.3, 58.3 ± 2.0, and 60.3 ± 2.0°K, respectively. We discuss the implications of the measurements for bolometric output and for atmospheric structure and composition. The temperature spectrum of Jupiter shows a strong peak at ～350 μm followed by a deep valley at ～450 to 500 μm. Spectra derived from model atmospheres qualitatively reproduce these features but do not fit the data closely.     

Ordovician provincial signals from Appalachian- Caledonian terranes

Statistical analysis of mainly mid to deep-shelf Ordovician brachiopod faunas from localities within and marginal to the Appalachian- Caledonian Orogen reveals biogeographical patterns not entirely consistent with those presumed for the progressive orthogonal closure of the Iapetus Ocean. Correspondence analysis of faunas of late Arenig-early Llanvirn, late Llandeilo-earliest Caradoc and late Ashgill age emphasize the importance of marginal and island faunas, the role of regressions and transgressions on faunal distributions and the effects of climatic change in the definition of biogeographical trends during the Ordovician.