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991.
S. M. Khaykin V. A. Yushkov L. I. Korshunov A. N. Luk’yanov J. -P. Pommereau J. Nielsen H. Vömel 《Izvestiya Atmospheric and Oceanic Physics》2010,46(1):76-84
The results of measurements of water-vapor vertical profiles in the upper troposphere and stratosphere on board a meteorological
balloon with a FLASH-B optical fluorescent hygrometer (Russia) are presented. These data were obtained during two international
field campaigns in West Africa (August 2006) and Central America (August 2007). Eleven high-resolution water-vapor vertical
profiles measured in the course of these works make it possible to characterize the processes controlling humidity in the
tropical tropopause region. Layers with increased humidity are detected in the lower stratosphere over West Africa to the
level of the potential temperature 450 K. An analysis of satellite maps of the brightness temperature, balloon ozone measurements,
and aerosol scattering, as well as trajectory modeling, display the relation between the observed layers with increased humidity
and the phenomena of convective overshooting of the tropopause, as a result of which cold and ozone-depleted air penetrates
into the lower stratosphere together with ice particles, which, rapidly sublimating, locally increase the water-vapor concentration.
A comparison of the humidity data obtained in West Africa in 2006 and in Central America in 2007 reveals substantial distinctions
in values and vertical structures of water vapor, both in the tropopause region and in the middle stratosphere. 相似文献
992.
993.
Anne Willem Omta Jorn Bruggeman Bas Kooijman Henk Dijkstra 《Journal of Sea Research》2009,62(2-3):179
The growth, sinking and remineralisation of phytoplankton constitute the soft-tissue carbon pump. Here we derive the expression for the strength of this carbon pump in terms of the nutrient utilisation and the carbon:nutrient ratio of plankton. Furthermore, we aim to determine how the physical environment affects this carbon pump. Thereto, we have used a plankton physiological model with a novel representation of the effect of temperature and light on plankton stoichiometry; it predicts that the effect of temperature on the carbon:nutrient ratio depends on the light conditions. Using this model combined with a mechanistic model for the mixed layer, we have studied the biological carbon pump at the BATS site and at various locations along a meridional transect through the Atlantic Ocean. Our results suggest that the soft-tissue carbon pump is stronger at mid-latitudes than in the (sub-)tropics and near the poles as a consequence of latitudinal variations in algal stoichiometry. 相似文献
994.
H.I. Petersen N. Sherwood A. Mathiesen M.B.W. Fyhn N.T. Dau N. Russell J.A. Bojesen-Koefoed L.H. Nielsen 《Marine and Petroleum Geology》2009
Several exploration wells have intersected a Cenozoic coal-bearing, fluvial-deltaic mudstone and sandstone succession in the northeastern Vietnamese part of the Malay Basin, and have successfully tested seismically identified direct hydrocarbon indicators (DHIs). The oil and gas/condensate discovery well 46-CN-1x encountered a ∼55 m thick section of lacustrine mudstones having considerable potential as an oil source. Vitrinite reflectance (VR) measurements from these alginite-bearing rocks introduce several problems in thermal maturity evaluation, including associated VR suppression and delineation of cavings and bitumens. Reliable thermal maturity gradients, however, may be established using a combination of conventional VR measurements and ‘equivalent VR’ (EqVR) values derived from the fluorescence alteration of multiple macerals (FAMM) technique. These measurements, performed on dispersed organic matter (DOM) in cuttings from 46-CN-1x, allow separation of low-reflecting bitumens and vitrinite in cavings from indigenous vitrinite and the FAMM results indicate VR suppression of 0.14% in an alginite-bearing mudstone with a high Hydrogen Index value. On the basis of available ‘raw’ VR data, a highly irregular maturity trend is determined, with the deepest sample (2675–2680 m) having a VR of ∼0.4%Ro. The EqVR value, however, for the deepest sample is 0.70%. The maturity trend determined from the FAMM data (and VR data, omitting samples having suppressed VR) indicates that the top of the oil window (VR of 0.75%Ro) is located at about 2800 m depth. Modelling the geothermal gradient using the EASY%Ro algorithm yields ∼40 °C/km for both of the two maturity profiles; this is in the low end of the range for the Malay Basin. Modelled temperature histories indicate onset of hydrocarbon generation for the uppermost Oligocene source rocks between 2 Ma and present-day, which post-dates trap formation. Seismic facies patterns suggest that lacustrine oil-prone units are in the oil window in the same graben complex a few km NW of the investigated well, and these rocks are likely to be the source of the hydrocarbons found in the well. A more widespread occurrence of hydrocarbons sourced from this kitchen is indicated by other discoveries and mapping of DHIs in the area. 相似文献
995.
Recent research has on the basis of general equilibrium models warned that trade liberalisation in non-optimally managed renewable resources might cause over-exploitation and reduced steady-state welfare. Welfare effects of trade liberalisation in open access and optimal management are found case specific and dependent on factors such as the country's status as importer or exporter, the state of the fish stocks and the size of the countries on the world market. The present paper develops an alternative partial equilibrium framework capable of identifying welfare effects of fish trade liberalisation also in the presence of complex but realistic management schemes, such as regulated open access and regulated restricted access. The case dependency known from the general equilibrium analysis is confirmed, but the introduction of realistic fisheries management schemes in the partial equilibrium model extended this case dependency. The welfare effect of trade liberalisation in an exporter country is negative under open access, but was found positive under regulated restricted access in the present paper. 相似文献
996.
An assemblage of geoduck clam shells from the marine environment of coastal British Columbia was studied. Shells were cut
and the widths of internal shell growth increments, annuli, were measured from the hinge plate. The largest shells showed
more than one hundred annual increments. Shell growth exhibited juvenile maxima at ontogenetic ages 3–6 years. The growth
maximum was followed by a distinct decline that continued until the death of each individual. Further, this ontogenetic growth
trend was mathematically removed from the data in order to examine growth variations other than ageing. The longest growth
records from the oldest shells were compared to monthly indices of the Pacific Decadal Oscillation (PDO). It was found that
the PDO exerts the strongest influence on the shell growth during the very start of the growing season, in February and March.
We also detected increased magnitude of growth variations towards the end of the 20th century. Similar trends were apparent
in the PDO record. Moreover, the shell specimen displaying the strongest trend of increasing variance had the strongest PDO-linked
regional growth signal. Our results support the view that PDO exerts a governing influence on the biological and ecological
system along Northeast Pacific coastal areas. Incorporation of geoduck shell growth increment analyses into multi-disciplinary
studies dealing with palaeoceanography and archaeology is suggested as a promising future approach. 相似文献
997.
998.
Charlotte L. Clarke Mary E. Edwards Antony G. Brown Ludovic Gielly Youri Lammers Peter D. Heintzman Francisco Javier Ancin‐Murguzur Kari‐Anne Brthen Tomasz Goslar Inger G. Alsos 《Boreas: An International Journal of Quaternary Research》2019,48(2):299-316
We present a Holocene record of floristic diversity and environmental change for the central Varanger Peninsula, Finnmark, based on ancient DNA extracted from the sediments of a small lake (sedaDNA). The record covers the period c. 10 700 to 3300 cal. a BP and is complemented by pollen data. Measures of species richness, sample evenness and beta diversity were calculated based on sedaDNA sampling intervals and 1000‐year time windows. We identified 101 vascular plant and 17 bryophyte taxa, a high proportion (86%) of which are still growing within the region today. The high species richness (>60 taxa) observed in the Early Holocene, including representatives from all important plant functional groups, shows that modern shrub‐tundra communities, and much of their species complement, were in place as early as c. 10 700 cal. a BP. We infer that postglacial colonization of the area occurred prior to the full Holocene, during the Pleistocene‐Holocene transition, Younger Dryas stadial or earlier. Abundant DNA of the extra‐limital aquatic plant Callitriche hermaphroditica suggests it expanded its range northward between c. 10 200 and 9600 cal. a BP, when summers were warmer than present. High values of Pinus DNA occur throughout the record, but we cannot say with certainty if they represent prior local presence; however, pollen influx values >500 grains cm?2 a?1 between c. 8000 and 7300 cal. a BP strongly suggest the presence of pine woodland during this period. As the site lies beyond the modern tree limit of pine, it is likely that this expansion also reflects a response to warmer Early Holocene summers. 相似文献
999.
Laurie Boithias Yves Auda Stéphane Audry Jean-Pierre Bricquet Alounsavath Chanhphengxay Vincent Chaplot Anneke de Rouw Thierry Henry des Tureaux Sylvain Huon Jean-Louis Janeau Keooudone Latsachack Yann Le Troquer Guillaume Lestrelin Jean-Luc Maeght Pierre Marchand Pierre Moreau Andrew Noble Anne Pando-Bahuon Kongkeo Phachomphon Khambai Phanthavong Alain Pierret Olivier Ribolzi Jean Riotte Henri Robain Emma Rochelle-Newall Saysongkham Sayavong Oloth Sengtaheuanghoung Norbert Silvera Nivong Sipaseuth Bounsamay Soulileuth Xaysatith Souliyavongsa Phapvilay Sounyaphong Sengkeo Tasaketh Chanthamousone Thammahacksa Jean-Pierre Thiebaux Christian Valentin Olga Vigiak Marion Viguier Khampaseuth Xayyathip 《水文研究》2021,35(5):e14126
Mountain regions of the humid tropics are characterized by steep slopes and heavy rains. These regions are thus prone to both high surface runoff and soil erosion. In Southeast Asia, uplands are also subject to rapid land-use change, predominantly as a result of increased population pressure and market forces. Since 1998, the Houay Pano site, located in northern Lao PDR (19.85°N 102.17°E) within the Mekong basin, aims at assessing the long-term impact of the conversion of traditional slash-and-burn cultivation systems to commercial perennial monocultures such as teak tree plantations, on the catchment hydrological response and sediment yield. The instrumented site monitors hydro-meteorological and soil loss parameters at both microplot (1 m2) and small catchment (0.6 km2) scales. The monitored catchment is part of the network of critical zone observatories named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Houay Pano are (1) rainfall, (2) air temperature, air relative humidity, wind speed, and global radiation, (3) catchment land use, (4) stream water level, suspended particulate matter, bed particulate matter and stones, (5) soil surface features, and (6) soil surface runoff and soil detachment. The dataset has already been used to interpret suspended particulate matter and bed particulate matter sources and dynamics, to assess the impact of land-use change on catchment hydrology, soil erosion, and sediment yields, to understand bacteria fate and weed seed transport across the catchment, and to build catchment-scale models focused on hydrology and water quality issues. The dataset may be further used to, for example, assess the role of headwater catchments in large tropical river basin hydrology, support the interpretation of new variables measured in the catchment (e.g., contaminants other than faecal bacteria), and assess the relative impacts of both climate and land-use change on the catchment. 相似文献
1000.