The ISOCAM/LW Detector Dark Current Behaviour

We describe the calibration, measurements and data reduction, ofthe dark current of the ISOCAM/LW detector. We point-out theexistence of two significant drifts of the LW dark-current, onethroughout the ISO mission, on a timescale of days, another within each single revolution, on a timescale of hours. We alsoshow the existence of a dependence of the dark current on thetemperature of the ISOCAM detector.By characterizing all these effects through polynomial fittings,we build a model for the LW calibration dark, that depends onthe epoch of observation (parametrized with the revolutionnumber and the time elapsed in that given revolution since theactivation) and on the temperature of the ISOCAM detector. Themodel parameters are tuned for each of ISOCAM/LW pixel.We show that the modelling is very effective in taking intoaccount the dark-current variations and allows a much cleanerdark subtraction than using a brute average of severalcalibration dark images.The residuals of the LW model-dark subtraction are, on average,similar to the pre-launch expectation.     

跨进新世纪的特种精密工程测量

为了对二十一世纪的特种精密工程测量有一个新概念,在回顾特种精密工程测量发展概况的基础上,给出了如下几点展望：特种精密工程测量将走向自动化、智能化、实时化和系统化;特种精密工程测量将服务于国民经济各部门;特种精密工程测量将与其它科学技术一起发展。     

Hydrological and meteorological data from research catchments at the Marcell Experimental Forest,Minnesota, USA

The Marcell Experimental Forest (MEF) in northern Minnesota, USA, with hydrological research and monitoring of peatland catchments in a low-topographic relief landscape, contrasts with the mountainous terrain that typifies most research catchments. Six research catchments were instrumented and hydrological and meteorological monitoring was initiated during 1960. Paired-catchment studies, which started during 1969, have been used to assess land management and environmental change effects on forests, water availability, and biogeochemistry. Over the decades, the research and collaborations have proliferated to include new monitoring and ecosystem experiments. We provide an overview of available datasets and access information for hydrological and meteorological data. Data on streamflow, water table elevation, precipitation, snow, ground frost, air temperature, soil moisture, upland runoff, and water chemistry are discoverable with associated metadata and are archived through several Web-based, community repositories. The research programme is ongoing and we anticipate updates on an annual or more frequent basis. Additionally, we aim to release other physical, chemical, and isotopic measurements associated with long-term catchment monitoring and studies at the MEF.     

Fishes and decapod crustaceans of Cape Cod eelgrass meadows: Species composition,seasonal abundance patterns and comparison with unvegetated substrates

Bimonthly trawl samples from eelgrass and nearby unvegetated areas on Cape Cod, Massachusetts, showed greater species richness in eelgrass meadows relative to unvegetated areas, and greater summer abundance in vegetation for decapod crustaceans and fishes. The composition of eelgrass-associated decapods and fishes was dominated by cold-water taxa and was strikingly different from that of the better studied eelgrass meadows of the mid-Atlantic coast. Four of the eight decapod species collected, including the second and third most abundant taxa, do not even appear in collections reported from Chesapeake Bay eelgrass meadows. Similarly, 10 of the 22 fish species taken, including the first and sixth most abundant species, are not reported from Chesapeake Bay eelgrass samples. Cape Cod eelgrass beds seem to play a nursery role for several commercially important fish species, although the nursery function is less obvious than in previously studied mid-Atlantic eelgrass meadows.     

Aeolization on the Atlantic coast of Galicia (NW Spain) from the end of the last glacial period to the present day: Chronology,origin and evolution of coastal dunes linked to sea-level oscillations

The Atlantic coast of Galicia (NW Spain) is a high-energy environment where shingle beaches are currently developing. These coarser sediments alternate with sandy deposits which are also considered as beaches typical of a low-energy environment. The physical association of both types of sediment with contrasted sedimentary significance raises problems of interpretation. The study of four outcrops of fossil aeolianites on this coast has allowed us to reconstruct their evolution from the end of the Upper Pleistocene to the present day. Their chronology, estimated by optically stimulated luminescence between 35 and 14 ky at the end of the last glaciation (MIS2), coincides with a local sea level 120 m below the present one. This implies a coastline shifted several kilometres from its current location and the subaerial exposure of a wide strip of the continental shelf covered by sands. The wind blew sand to form dunes towards the continent, covering the coastal areas, which then emerged with no other limitation than the active river channels. Sea-level rise during the Holocene transgression has progressively swamped these aeolian deposits, leaving only flooded dunes, relict coastal dunes and climbing dunes on cliffs up to 180 m high. The aeolian process continued as long as there was a sandy source area to erode, although accretion finished when the sea reached its current level (Late Holocene). Since then, the wind turned from accretion to erosion of the dunes and sand beaches. This erosion exposes the older shingle beaches (probably of Eemian age) buried under the aeolian sands, as well as old, submerged forest remains and megalithic monuments. The destruction of sand beaches and dunes currently observed along the Galician coast is linked, according to most researchers, to anthropogenic global warming. However, their management should consider these evolutive issues.     

Cyber Literacy for GIScience: Toward Formalizing Geospatial Computing Education

The unprecedented availability of geospatial data and technologies is driving innovation and discovery but not without the risk of losing focus on the geographic foundations of space and place in this vast “cyber sea” of data and technology. There is a pressing need to educate a new generation of scientists and citizens who understand how space and place matter in the real world and who understand and can keep pace with technological advancements in the computational world. We define cyberliteracy for GIScience (cyberGIScience literacy) and outline eight core areas that serve as a framework for establishing the essential abilities and foundational knowledge necessary to navigate and thrive in this new technologically rich world. The core areas are arranged to provide multiple dimensions of learning ranging from a technological focus to a problem solving focus or a focus on GIScience or computational science. We establish a competency matrix as a means of assessing and evaluating levels of cyberGIScience literacy across the eight core areas. We outline plans to catalyze the collaborative development and sharing of instructional materials to embed cyberGIScience literacy in the classroom and begin to realize a cyberliterate citizenry and academe. Key Words: big data, computational thinking, geographic education, GIS, spatial thinking.     

Hazard assessment of the Tidal Inlet landslide and potential subsequent tsunami, Glacier Bay National Park, Alaska

An unstable rock slump, estimated at 5 to 10 × 10⁶ m³, lies perched above the northern shore of Tidal Inlet in Glacier Bay National Park, Alaska. This landslide mass has the potential to rapidly move into Tidal Inlet and generate large, long-period-impulse tsunami waves. Field and photographic examination revealed that the landslide moved between 1892 and 1919 after the retreat of the Little Ice Age glaciers from Tidal Inlet in 1890. Global positioning system measurements over a 2-year period show that the perched mass is presently moving at 3–4 cm annually indicating the landslide remains unstable. Numerical simulations of landslide-generated waves suggest that in the western arm of Glacier Bay, wave amplitudes would be greatest near the mouth of Tidal Inlet and slightly decrease with water depth according to Green’s law. As a function of time, wave amplitude would be greatest within approximately 40 min of the landslide entering water, with significant wave activity continuing for potentially several hours.     

Impacts of Hypoxia on Zooplankton Spatial Distributions in the Northern Gulf of Mexico

The northern Gulf of Mexico (NGOMEX) was surveyed to examine the broad-scale spatial patterns and inter-relationships between hypoxia (<2?mg?L^?1 dissolved oxygen) and zooplankton biovolume. We used an undulating towed body equipped with sensors for conductivity, temperature, depth, oxygen, fluorescence, and an optical plankton counter to sample water column structure, oxygen, and zooplankton at high spatial resolution (1?m??vertical; 0.25?C1?km??horizontal). We contrast the distribution of zooplankton during summer surveys with different freshwater input, stratification, and horizontal and vertical extent of bottom-water hypoxia. Bottom-water hypoxia did not appear to influence the total amount of zooplankton biomass present in the water column or the areal integration of zooplankton standing stock in the NGOMEX region surveyed. However, where there were hypoxic bottom waters, zooplankton shifted their vertical distribution to the upper water column during the day where they normally would reside in deeper and darker waters. When bottom waters were normoxic (>2?mg?L^?1 dissolved oxygen), the daytime median depth of the water column zooplankton was on average 7?m deeper than the median depth of zooplankton in water columns with hypoxic bottom waters. A reduction in larger zooplankton when there were hypoxic bottom waters suggests that if zooplankton cannot migrate to deeper, darker water under hypoxic conditions, they may be more susceptible to size-selective predation by visual predators. Thus, habitat compression in the northern Gulf of Mexico due to hypoxic bottom water may have implications for trophic transfer by increasing the contact between predators and prey.     

Quantitative Analysis of H2OComa Images Using a Multiscale MHD Model with Detailed Ion Chemistry

The observation of ions created by ionization of cometary gas, either by ground-based observations or byin situmeasurements can give us useful information about the gas production and composition of comets. However, due to the interaction of ions with the magnetized solar wind and their high chemical reactivity, it is not possible to relate measured ion densities (or column densities) directly to the parent gas densities. In order to quantitatively analyze measured ion abundances in cometary comae it is necessary to understand their dynamics and chemistry. We have developed a detailed ion–chemical network of cometary atmospheres. We include production of ions by photo- and electron impact-ionization of a background neutral atmosphere, charge exchange of solar wind ions with cometary atoms/molecules, reactions between ions and molecules, and dissociative recombination of molecular ions with thermal electrons. By combining the ion–chemical network with the three-dimensional plasma flow as computed by a new fully three-dimensional MHD model of cometary plasma environments (Gombosiet al.1996) we are able to compute the density of the major cometary ions everywhere in the coma. The input parameters for our model are the solar wind conditions (density, speed, temperature, magnetic field) and the composition and production rate of the gas. We applied our model to Comet P/Halley in early March 1986, for which the input parameters are reasonably well known. We compare the resulting column density of H₂O⁺with ground-based observations of H₂O⁺from DiSantiet al.(1990). The results of our model are in good agreement with both the spatial distribution and the absolute abundance of H₂O⁺and with their variations with the changing overall water production rate between two days. The results are encouraging that it will be possible to obtain production rates of neutral cometary constituents from observations of their ion products.