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51.
J. F. Read M. I. Lucas S. E. Holley R. T. Pollard 《Deep Sea Research Part I: Oceanographic Research Papers》2000,47(12):2341-2367
A survey was made of the Southwest Indian Ocean frontal region between 30 and 50°E containing the Agulhas Return, Subtropical and Subantarctic Fronts. From CTD, SeaSoar and extracted samples the distribution of nitrate, silicate and chlorophyll a is shown to be strongly linked to the front and water mass structure, varying zonally and meridionally. Surface chlorophyll a concentrations were low to the north and south leaving a band of elevated chlorophyll between the Subtropical and Subantarctic Fronts. The low concentration of chlorophyll a to the north, in Subtropical Water, was clearly due to nitrate limitation. Between the Subtropical and Subantarctic Fronts, where the chlorophyll a concentrations were highest, the surface layer showed silicate depletion limiting diatom growth. South of the Subantarctic Front there were deep extending, low concentrations of chlorophyll a, but despite plentiful supplies of macro-nutrients and a well-stratified surface layer, high concentrations of chlorophyll a were absent. Changes from west to east were associated with the meandering of the Southern Ocean Fronts, especially the Subtropical Front, and their strength and proximity to each other. Concentrations of chlorophyll a peaked where the Agulhas Return, Subtropical and Subantarctic Fronts were in close proximity. Combined frontal structures appear to have particularly pronounced vertical stability and are associated with enhanced upwelling of nutrients and leakage of nutrients across the front. Light levels are high within the shallow stable layer. Such conditions are clearly favourable for biological growth and support the development of larger-celled phytoplankton communities. 相似文献
52.
Cathy H. Lucas 《Journal of Sea Research》2003,50(4):301-308
Observations of resuspended diatoms in the shallow waters (<60 cm) of the turbid tidal edge are described for single sites on two tidal flats–the Molenplaat in the Westerschelde estuary, and the Hond in the Ems-Dollard estuary, The Netherlands. High concentrations of chlorophyll-a (chl-a) were observed in the trailing edge of the ebbing tide in water depths of <20 cm, after which concentrations decreased markedly. Peak mean values were 19 μg chl-a l−1 in 10 cm of water at the Molenplaat, and 45 μg chl-a l−1 in 5 cm of water at the Hond. Similar trends were observed on the flooding tide, although peak values were far less pronounced (6 and 30 μg chl-a l−1 respectively). Microscopic examination of the diatom community within the turbid tidal edge at the Molenplaat revealed that peaks in biomass were caused by suspended benthic diatoms, as well as the large centric diatom Coscinodiscus sp., particularly on the ebb tide. Planktonic diatoms other than Coscinodiscus sp. were more randomly distributed and did not appear to follow any particular trend. It would seem that as the tide recedes, resuspended benthic diatoms and large Coscinodiscus sp. cells become concentrated in the shallow water. However, the virtual absence of Coscinodiscus sp. from the leading edge of the flooding tide suggests that most of the resuspended cells do not settle to the seabed, but are washed away into the channels. The small peak of benthic diatoms at the leading edge of the flood tide is most likely resuspended locally from the sediment, along with large numbers of diatom frustules. 相似文献
53.
54.
Lucas O. Bianchi Juan Antonio Rivera Facundo Rojas Mauro Britos Navarro Ricardo Villalba 《水文科学杂志》2017,62(4):533-545
In the Central Andes of Argentina (30–37°S), snowmelt is the main source of freshwater, an essential natural resource for ~2.2 million people in the adjacent arid lowlands. In this region, Laguna Llancanelo collects the water inputs from the Malargüe endorheic basin. Previous studies concerning the annual and intra-annual variations of this lagoon and its relationship with regional climate are rare. We obtained a monthly record for the Laguna Llancanelo area (LLA, 1984–2013) using the modified normalized difference water index derived from Landsat images. Monthly LLA ranges between 35 km2 and 411 km2 and is significantly related to variations of the Río Malargüe, the main snow-fed tributary to the lagoon. There is no long-term relationship between LLA and local rainfall, but rapid increases in LLA result from heavy rainfall around the lagoon. Conversely, rapid reductions in LLA encompass periods with both reduced discharge from the Río Malargüe and low local rainfall. The LLA integrates moisture of both Pacific (snowfall in the upper Andes) and Atlantic (lowland rainfall) origins; therefore, we propose using LLA as an indicator of regional water balance. 相似文献
55.
Research presented here explores the feasibility of leveraging vegetation data derived from airborne light detection and ranging (LiDAR) and terrestrial laser scanning (TLS) for visibility modeling. Using LiDAR and TLS datasets of a lodgepole pine (Pinus contorta) dominant ecosystem, tree canopy and trunk obstructions were isolated relevant to a discrete visibility beam in a short‐range line‐of‐sight model. Cumulative obstruction factors from vegetation were compared with reference visibility values from digital photographs along sightline paths. LiDAR‐derived tree factors were augmented with single‐scan TLS data for obstruction prediction. Good correlation between datasets was found up to 10 m from the terrestrial scanner, but fine scale visibility modeling was problematic at longer distances. Analysis of correlation and regression results reveal the influence of obstruction shadowing inherent to discrete LiDAR and TLS, potentially limiting the feasibility of modeling visibility over large areas with similar technology. However, the results support the potential for TLS‐derived subcanopy metrics for augmenting large amounts of aerial LiDAR data to significantly improve models of forest structure. Subtle LiDAR processing improvements, including more accurate tree delineation through higher point density aerial data, combined with better vegetation quantification processes for TLS data, will advance the feasibility and accuracy of data integration. 相似文献
56.
Using structured telephone interviews this research focuses on how Canadian migrants living in the United States experience
and describe home. We argue that the globalisation of peoples’ lives, transnationalism and the concomitant creation of transnational
social spaces have greatly affected the meaning of home for migrants. The understandings of home that result reflect the reality
of living in social worlds that span two countries and the development of decentred multiple attachments and feelings of belonging
in more than one place. In response to these circumstances Canadian migrants experience home as multi-dimensional, pluri-local,
and characterized by regular movement across the U.S.–Canada border. When asked specifically about feeling at home upon re-entry
to the U.S. many respondents answered yes. However, many interviewees qualified their answers by describing home in different
ways and associating different aspects of their lives with each country. Canada as home was most often described in terms
of family, while home in the U.S. was associated with work. Respondents also differentiated between feeling at home once they
reached their residence as opposed to feeling unwelcome at the U.S. border. 相似文献
57.
Richard Menzel 《Aquatic Sciences - Research Across Boundaries》1946,10(2-3):186-191
58.
Imaging polarimetry of class I young stellar objects 总被引:1,自引:0,他引:1
59.
60.
John D. Monnier Stefan Kraus Michael J. Ireland Fabien Baron Amelia Bayo Jean-Philippe Berger Michelle Creech-Eakman Ruobing Dong Gaspard Duchêne Catherine Espaillat Chris Haniff Sebastian Hönig Andrea Isella Attila Juhasz Lucas Labadie Sylvestre Lacour Stephanie Leifer Antoine Merand Ernest Michael Stefano Minardi Christoph Mordasini David Mozurkewich Johan Olofsson Claudia Paladini Romain Petrov Jörg-Uwe Pott Stephen Ridgway Stephen Rinehart Keivan Stassun Jean Surdej Theo ten Brummelaar Neal Turner Peter Tuthill Kerry Vahala Gerard van Belle Gautam Vasisht Ed Wishnow John Young Zhaohuan Zhu 《Experimental Astronomy》2018,46(3):517-529
The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust emission using mid-infrared capabilities made possible by precise fringe tracking in the near-infrared. An L/M band combiner will be especially sensitive to thermal emission from young exoplanets (and their disks) with a high spectral resolution mode to probe the kinematics of CO and H2O gas. In this paper, we give an overview of the main science goals of PFI, define a baseline PFI architecture that can achieve those goals, point at remaining technical challenges, and suggest activities today that will help make the Planet Formation Imager facility a reality. 相似文献