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341.
342.
Peter R. Gent Stephen G. Yeager Richard B. Neale Samuel Levis David A. Bailey 《Climate Dynamics》2010,34(6):819-833
A decadal climate projection between 1980 and 2030 using a nominal 0.5° resolution in the atmosphere and land components has
been performed using the Community Climate System Model, version 3.5. The mean climate is compared to a companion simulation
using a nominal 2° resolution in the atmosphere and land components. The increased atmosphere resolution has several benefits,
and produces a significantly better mean climate. The maximum sea surface temperature biases in the major upwelling regions,
including the West Coast of the USA, are reduced by more than 60%. Precipitation patterns are improved in the summer Asian
monsoon, mostly due to the better resolved orography, and in the eastern tropical Pacific Ocean south of the equator. The
improved precipitation patterns lead to better river flows in many rivers worldwide. The atmospheric circulation in the Arctic
also improves, which leads to a better regional sea ice thickness distribution in the Arctic Ocean. 相似文献
343.
Samuel Nicolay Georges Mabille Xavier Fettweis Michel Erpicum 《Climate Dynamics》2009,33(7-8):1117-1129
A wavelet-based methodology is applied to relevant climatic indices and air temperature records and allow to detect the existence of unexpected cycles. The scale spectrum shows the presence of two cycles of about 30 and 43 months, respectively, in the air–temperature time series, in addition to the well-known cycles of 1 day and 1 year. The two cycles do not affect the globe uniformly: some regions seem to be more influenced by the period of 30 months (e.g. Europe), while other areas are affected by the period of 43 months (e.g. North-West of the USA). Similar cycles are found in the indices and the regions influenced by these indices: the NAO index and the Western Europe display a cycle of 30 months, while the cycle of 43 months can be found in the ENSO index and in regions where it is known to have an impact. 相似文献
344.
Marcelo Samuel Berman 《Astrophysics and Space Science》2009,321(3-4):157-160
We “explain”, using a Classical approach, how the Universe was created out of “nothing”, i.e., with no input of initial energy nor mass. The inflationary phase, with exponential expansion, is accounted for, automatically, by our equation of state for the very early Universe. This is a Universe with no-initial infinite singularity of energy density. 相似文献
345.
OluKayode J. Samuel Chris Cornford Martin Jones Olabisi A. Adekeye Samuel O. Akande 《Organic Geochemistry》2009,40(4):461-483
Biomarker and n-alkane compound specific stable carbon isotope analyses (CSIA) were carried out on 58 crude oil samples from shallow water and deepwater fields of the Niger Delta in order to predict the depositional environment and organic matter characteristics of their potential source rocks. Using a source organofacies prediction approach from oil geochemistry, the presence in the western deepwater oils relatively abundant C27 steranes, C30 24-n-propyl cholestane, low oleanane index, relatively low pr/ph ratios, gammacerane, and positive to nearly flat C12–C30 n-alkane compound specific stable carbon isotope profiles, suggests that the source facies that expelled these oils contain significant marine derived organic matter deposited under sub-oxic and stratified water column conditions. This contrasts with the terrigenous organic matter dominated source rocks accepted for shallow water Niger Delta oils. Oils in the shallow water accumulations can be separated into terrigenous and mixed marine-terrigenous families. The terrigenous family indicates expulsion from source rock(s) containing overwhelmingly higher plant source organic matter (average oleanane index = 0.48, high C29 steranes) as well as having negative sloping n-alkane isotope profiles. Oxic source depositional conditions (pr/ph > 2.5) and non-stratified conditions (absence to low gammacerane content) are inferred for the terrigenous family. The mixed marine-terrigenous family has biomarker properties that are a combination of the deepwater and terrigenous shallow water oils. Bitumen extracts of the sub-delta Late Cretaceous Araromi Formation shale in the Dahomey Basin are comparable both molecularly and isotopically to the studied western deepwater oil set, but with an over all poor geochemical correlation. This poor geochemical match between Araromi shale and the western deepwater oils does not downgrade the potential of sub-delta Cretaceous source rock contribution to the regional oil charge in the deepwater Niger Delta. 相似文献
346.
Geochemical fingerprinting is a rapidly expanding discipline in the earth and environmental sciences. It is anchored in the recognition that geological processes leave behind chemical and isotopic patterns in the rock record. Many of these patterns, informally referred to as geochemical fingerprints, differ only in fine detail from each other. For this reason, the approach of fingerprinting requires analytical data of very high precision and accuracy. 相似文献
347.
Hydrogeochemical controls and usability of groundwater in the semi-arid Mayo Tsanaga River Basin: far north province,Cameroon 总被引:2,自引:0,他引:2
Wilson Y. Fantong Hiroshi Satake Samuel N. Ayonghe Festus T. Aka Kazuyoshi Asai 《Environmental Geology》2009,58(6):1281-1293
Deuterium, δ
18O, major ions and dissolved silica in groundwater from semi-arid Mayo-Tsanaga river basin in the Far North Province, Cameroon
were used to trace hydrogeochemical processes that control their concentrations and to explore for usability of the water.
Electrical conductivity ranges from 57–2,581 μs/cm with alternating low and high values along the hydraulic gradient. Waters
from piedmont alluvium show low concentrations in major cations, which peak in Mg within basalt, Na within plain alluvium,
and Ca within basalt and the sandy Limani-Yagoua ridge. The initial dominant groundwater composition is CaHCO3, which did not evolve within the basalt and piedmont alluvium, but evolved to NaHCO3 in the granite and plain alluvium. The main processes controlling the major ions composition include the following: (1) dissolution
of silicates and fluorite; (2) precipitation of fluorite and carbonate; (3) cation exchange of Ca in water for Na in clay;
(4) and anthropogenic activities. The δD and δ
18O ratios vary from −35 to 0.7 and −5.3 to 1.1‰, respectively. The lowest and highest isotope ratios are observed in groundwater
within the downstream sandy Limani-Yagoua ridge and the upstream graintes respectively. Variation in isotope ratios depends
on altitude effect of −0.48‰ per 100 m between 600 and 850 m asl, and on evaporation, which had insignificant effect on the
water salinity. Seventy percent of the groundwater shows poor drinking quality and 90% is suitable for irrigation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
348.
Benjamin I. Cook Gordon B. Bonan Samuel Levis Howard E. Epstein 《Climate Dynamics》2008,31(1):107-124
We use a state of the art climate model (CAM3–CLM3) to investigate the sensitivity of surface climate and land surface processes
to treatments of snow thermal conductivity. In the first set of experiments, the thermal conductivity of snow at each grid
cell is set to that of the underlying soil (SC-SOIL), effectively eliminating any insulation effect. This scenario is compared
against a control run (CTRL), where snow thermal conductivity is determined as a prognostic function of snow density. In the
second set of experiments, high (SC-HI) and low (SC-LO) thermal conductivity values for snow are prescribed, based on upper
and lower observed limits. These two scenarios are used to envelop model sensitivity to the range of realistic observed thermal
conductivities. In both sets of experiments, the high conductivity/low insulation cases show increased heat exchange, with
anomalous heat fluxes from the soil to the atmosphere during the winter and from the atmosphere to the soil during the summer. The increase in surface heat exchange leads to soil cooling of up to 20 K in the winter, anomalies that
persist (though damped) into the summer season. The heat exchange also drives an asymmetric seasonal response in near-surface
air temperatures, with boreal winter anomalies of +6 K and boreal summer anomalies of −2 K. On an annual basis there is a
net loss of heat from the soil and increases in ground ice, leading to reductions in infiltration, evapotranspiration, and
photosynthesis. Our results show land surface processes and the surface climate within CAM3–CLM3 are sensitive to the treatment
of snow thermal conductivity. 相似文献
349.
A high-resolution dataset of trace element concentrations is presented for the Murray–Darling Basin, Australia, Australia’s most important river system. The data were obtained by solution quadrupole ICP-MS resulting in concentrations for 44 elements. Of these, 21 were determined with a long-term external precision of better than 1% and a further 13 at a precision better than 2%. Trace element maps for the surface sediments constructed from such high precision data reveal small but coherent variations in the four major sub-catchments of the basin, even in ratios of elements with very similar geochemical behaviour, such as Y/Ho, Nb/Ta and Zr/Hf. The origin of these chemical fingerprints of drainage systems are discussed in terms of the geochemical character of the upper continental crust. The potential of trace element maps for palaeo-environmental and climatic reconstruction is then illustrated. First, a sample of dust collected in a trap located in the far southeastern corner of the study area is used to pinpoint the location of the dust source. Next the fine-scale change in down-stream alluvial sediment chemistry is analysed to estimate the importance of sediment contribution from tributaries with a view to reconstructing river flow dynamics. Finally, the chemistry of dune sediments is compared with surrounding floodplain alluvium to estimate relative age of deposition. These examples demonstrate that in low-elevation river systems, such as the Murray–Darling Basin, extended trace element maps of sediment offer substantially more applications than radiogenic isotope data alone. 相似文献
350.
Identifying factors influencing flood mitigation at the local level in Texas and Florida: the role of organizational capacity 总被引:1,自引:0,他引:1
In the United States, mitigating the adverse impacts of flooding has increasingly become the responsibility of local decision
makers. Despite the importance of understanding why flood mitigation techniques are implemented at the local level, few empirical
studies have been conducted over the last decade. Our study addresses this lack of research by examining the factors influencing
local communities to adopt both structural and non-structural flood mitigation strategies. We use statistical models to predict
multiple flood mitigation techniques implemented by cities and counties based on a survey of floodplain administrators and
planning officials across Texas and Florida. Particular attention is paid to the role of organizational capacity to address
floods in addition to various local geophysical and socioeconomic characteristics. Results indicate that organizational capacity
is a significant factor contributing to the implementation of both structural and non-structural flood mitigation techniques,
even when controlling for contextual characteristics. 相似文献