Estimation of the surface energy balance in the Sahelian zone of Western Africa     

Henrik Søgaard 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):108-115

Søgaard, Henrik: Estimation of the surface energy balance in the Sahelian zone of Western Africa. Geografisk Tidsskrift 88: 108- 115. Copenhagen 1988.

In studies of desertification in the Sahelian zone of Western Africa an improved knowledge of the water and surface energy balance is recognized to be of major importance. Based on micro-climatological measurements collected during an ongoing field study in the northern part of Burkina Faso, a number of methods for deriving surface energy balance are examined. It is found that for the actual case, with profile measurements restricted to two levels above the surface, exact values of the sensible heat flux can accurately be obtained by applying non-dimensional gradients based on the Monin-Obukhov turbulence theory. Utilization of the results for deriving actual evapotranspiration from standard observations is demonstrated, and the paper finally discusses applicability of the results in satellite remote sensing.  相似文献   

Biomarker responses in Atlantic cod (Gadus morhua) exposed to produced water from a North Sea oil field: laboratory and field assessments     

Sundt RC  Ruus A  Jonsson H  Skarphéðinsdóttir H  Meier S  Grung M  Beyer J  Pampanin DM 《Marine pollution bulletin》2012,64(1):144-152

Biological markers of produced water (PW) exposure were studied in Atlantic cod (Gadus morhua) in both laboratory and field experiments, using authentic PW from a North Sea oil field. In the laboratory study, the PW exposure yielded significantly elevated levels of metabolites of polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APs) in bile even at the lowest exposure dose (0.125% PW). Other biomarkers (hepatic CYP1A induction and DNA adduct formation) responded at 0.25% and 0.5% PW concentrations. In the field study, bile metabolite markers and hepatic CYP1A were clearly increased in fish caged close to the PW outfall. Induction of plasma vitellogenin was not found in laboratory or field exposures, suggesting that the levels of oestrogen agonists (such as APs) might not have been sufficient to elicit induction, under the present conditions. The applicability of the biomarkers for use in water column biomonitoring programs is discussed.  相似文献   

Stochastic rainfall-runoff forecasting: parameter estimation,multi-step prediction,and evaluation of overflow risk   总被引：2，自引：2，他引：0  

Roland Löwe  Peter Steen Mikkelsen  Henrik Madsen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):505-516

Probabilistic runoff forecasts generated by stochastic greybox models can be notably useful for the improvement of the decision-making process in real-time control setups for urban drainage systems because the prediction risk relationships in these systems are often highly nonlinear. To date, research has primarily focused on one-step-ahead flow predictions for identifying, estimating, and evaluating greybox models. For control purposes, however, stochastic predictions are required for longer forecast horizons and for the prediction of runoff volumes, rather than flows. This article therefore analyzes the quality of multistep ahead forecasts of runoff volume and considers new estimation methods based on scoring rules for k-step-ahead predictions. The study shows that the score-based methods are, in principle, suitable for the estimation of model parameters and can therefore help the identification of models for cases with noisy in-sewer observations. For the prediction of the overflow risk, no improvement was demonstrated through the application of stochastic forecasts instead of point predictions, although this result is thought to be caused by the notably simplified setup used in this analysis. In conclusion, further research must focus on the development of model structures that allow the proper separation of dry and wet weather uncertainties and simulate runoff uncertainties depending on the rainfall input.  相似文献   

Inertial waves near corotation in three-dimensional hydrodynamical discs     

Henrik N. Latter  Steven A. Balbus 《Monthly notices of the Royal Astronomical Society》2009,399(2):1058-1073

This paper concerns the interaction between non-axisymmetric inertial waves and their corotation resonances in a hydrodynamical disc. Inertial waves are of interest because they can localize in resonant cavities circumscribed by Lindblad radii and, as a consequence, can exhibit discrete oscillation frequencies that may be observed. It is often hypothesized that these trapped eigenmodes are affiliated with the poorly understood quasi-periodic oscillation phenomenon. We demonstrate that a large class of non-axisymmetric three-dimensional (3D) inertial waves cannot manifest as trapped normal modes. This class includes any inertial wave whose resonant cavity contains a corotation singularity. Instead, these 'singular' modes constitute a continuous spectrum and, as an ensemble, are convected with the flow, giving rise to shearing waves. Finally, we present a simple demonstration of how the corotation singularity stabilizes 3D perturbations in a slender torus.  相似文献   

Numerical nucleosynthesis results for Bianchi type-V cosmological models     

Mark S. Madsen  D. R. Matravers  Davin Milun 《Astrophysics and Space Science》1986,123(2):411-414

Results of numerical calculations of helium-4 and deuterium abundances in a wide range of Bianchi type-V locally rotationally-symmetric cosmological models are presented. The tabulated element abundances show that these models generically yield helium fractions which are unacceptably large compared with the available observational data.  相似文献   

Adsorption of polar aromatic hydrocarbons on synthetic calcite   总被引：1，自引：0，他引：1  

Lene Madsen  Laila Grahl-Madsen  Christian Grøn  Ida Lind  John Engell 《Organic Geochemistry》1996,24(12):1151-1155

The wettability of hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. A model system of synthetic calcite, cyclohexane and the three probe molecules: benzoic acid, benzyl alcohol and benzylamine, have been studied by adsorption experiments. The results clearly demonstrate the differences in the adsorption behaviour between probes with different functional groups of varying polarity and acidity. The maximum adsorption decreases in the order: benzoic acid, benzyl alcohol and benzylamine. The order of magnitude of ΔG° for the adsorption process implies the formation of a strong bond between the calcite surface and the adsorbate molecules.  相似文献   

Rock geochemistry of an iron ore field in the Divrigi region, Central Anatolia, Turkey. A new exploration model for iron ores in Turkey     

Henrik Stendal  Taner Ünlü 《Journal of Geochemical Exploration》1991,40(1-3)

One hundred and sixty rock samples of iron ore deposits and their host rocks from the Divrigi iron ore region were analysed for ten major and 31 trace elements, and 30 samples were analysed for rare earth elements. Statistical analyses divide rock types into different units (discriminant analyses) and several element associations (cluster and factor analyses). Individual rock types were also treated statistically. Different element associations and the geochemistry of the REE point to a genetic relationship between ore and host rocks and later hydrothermal overprints.The interpretation suggests iron ores are closely associated with mafic ultramafic rocks. This exploration model has been applied iron ore deposits in central Anatolia, Turkey. The results stimulated first air-magnetic and later ground-magnetic field surveys leading to discovery of new iron ore occurrences which are currently being evaluated for their economic potential.  相似文献   

Late quaternary glacial and vegetation changes,Little Cottonwood Canyon area,Wasatch mountains,Utah     

David B. Madsen  Donald R. Currey 《Quaternary Research》1979,12(2):254-270

Glacial geology and ¹⁴C dating in the central Wasatch Mountains indicate: an early canyon-mouth glaciation (Dry Creek till), probably during isotope stage 6; on that till, a paleosol (Majestic Canyon soil) dated at about 26,000 yr B.P.; overriding that soil, a later canyon-mouth glaciation (Bells Canyon till) probably beginning prior to about 19,000 yr B.P.; a midcanyon deglacial pause (Hogum Fork till) prior to 12,300 yr B.P.; an upper-canyon deglacial pause (Devils Castle till) prior to 7500 yr B.P.; and late Holocene periglaciation. Pollen ratios from bog profiles in the mid to upper reaches of the canyon suggest that temperatures cooler than the Holocene average occurred until after about 8000 yr B.P. Warmer and dryer than average conditions were initiated about 8000 to 7500 yr B.P. During the later portion of this Altithermal period conditions became relatively warm and wet. Two subsequent episodes of cooler than average temperatures correspond chronologically to the initial stades of Neoglaciation elsewhere in the Rocky Mountains. However, there is no geomorphic evidence of corresponding glacial activity in the canyon area. Relative moisture during these two periods differs significantly, suggesting that Neoglacial conditions were controlled primarily by changes in summer temperature.  相似文献   

A Late Pleistocene Tephra Layer in the Southern Great Basin and Colorado Plateau Derived from Mono Craters, California     

David B. Madsen  Andrei M. Sarna-Wojcicki  Robert S. Thompson 《Quaternary Research》2002,57(3):382

A newly identified tephra in stratified deposits in southwestern Utah, dated 14,000 ¹⁴C yr B.P., may aid in correlating late Pleistocene deposits across parts of the southern Great Basin and west-central Colorado Plateau. Geochemical analyses of the ash suggest the tephra originated from Mono Craters, California, and most probably correlates with Wilson Creek ash #3. Because the ash is 2 mm thick 550 km from its source, the event may have been larger than others correlated to Mono Craters eruptions.  相似文献   

Water in boninite glass and coexisting orthopyroxene: concentration and partitioning   总被引：3，自引：0，他引：3  

Patrick F. Dobson  Henrik Skogby  George R. Rossman 《Contributions to Mineralogy and Petrology》1995,118(4):414-419

 Spectroscopic measurements of water in glass inclusions in pyroxene from boninite samples from the Bonin Islands conclusively document the high (2.8–3.2 wt %) primary water contents of boninite magmas. Associated quenched glass from pillow lava rims have slightly lower (2.2–2.4 wt %) water contents, suggesting that minor amounts of degassing occurred between the time of melt entrapment in the orthopyroxenes and subsequent eruption on the sea floor. Some zonation of molecular water contents in pillow rim glasses was observed. OH contents of the host orthopyroxene phenocrysts were also measured, allowing for the calculation of partition coefficients for water between boninite melt and orthopyroxene. These values (0.003–0.004) for water partitioning between orthopyroxene and mafic melts may help constrain petrogenetic models of mantle-derived magmas. Received: 20 September 1993 / Accepted: 26 June 1994  相似文献