The present situation with the absolute methods of observations in fundamental astrometry

Conclusions The present situation with absolute methods is the accumulated result of continuous deviations from the classical basic principles during the current century, and this has led to the obfuscation of the general clear concepts.While the available catalogues which contain hybrid coordinates of stars are useful for many purposes, they are of limited use for improving the theories of the solar system bodies or verifying the laws of dynamics. For these tasks, one must compare calculated coordinates with theory independent ones, i.e. such, wich are either related to absolute coordinates of stars or related to extragalactic radio objects. If international cooperation in the field of absolute observations with astrolabes and other BIH instruments should be organized, the coming years will show which of the alternatives is more effective.     

The Impact of Cloud Representation on the Sub-Seasonal Forecasts of Atmospheric Teleconnections and Preferred Circulation Regimes in the Northern Hemisphere

Abstract

The impact of cloud representation on the simulation of mid-latitude recurrent large-scale flows and forecast skill of mid-latitude atmospheric teleconnections is evaluated using the Community Climate System Model, version 4 (CCSM4), and the super-parameterized CCSM4 (SP-CCSM4). Patterns of low-level atmospheric circulation anomalies and convection associated with the Madden–Julian oscillation (MJO) are affected by the method used for the representation of cloud processes. The configuration of the model using super-parameterization for the representation of cloud processes produces MJO-related patterns that agree better with observations than the configuration of the model using a conventional cloud parameterization scheme. The recurrent circulation regimes of the mid-latitudes are also sensitive to the representation of cloud processes. In the North Atlantic sector, the inability of CCSM4 to simulate the Scandinavian blocking regime is corrected in the super-parameterized version of the model. In the North Pacific sector, the strength of the clustering (measured by a variance ratio) is too large in CCSM4 compared with observations and SP-CCSM4. The SP-CCSM4 model has better forecast skill for the MJO amplitude and phase than the model with conventional representation of moist convective processes. In turn, the improved forecast skill of the super-parameterized model results in better forecast skill for mid-latitude teleconnections in 500 hPa geopotential height anomalies forced by the MJO convection.     

The spatial distribution of the lignite qualitative parameters and variant estimates of coal reserves: the Czech Part of the Vienna Basin

The aim of this article is to inform about the spatial distribution of the lignite qualitative parameters and total lignite reserves in the Czech Part of the Vienna Basin—The South Moravian Lignite Coalfield (SMLC). The total reserves were estimated on the basis of several composed variant digital models of individual seams in four partial area of SMLC. Calculations of the reserves resulted from the identified spatial distribution of chemical-technological parameters obtained from the thousands analysis of samples taken from more than 4,000 exploration works. The basic model of the deposit was so-called geological model characterising genetic evolution of the deposit and defines the spatial positions of the coal seams. Subsequently developed variant economical models spatially define the selected areas by the quality of lignite expressed by the limits of ash yield. Based on the created models, it was found that in the past just 3–7 % (depending on the variant model) of the total lignite reserves SMLC had been extracted. The presented geological reserves are currently using the existing mining technologies only partially mineable.     

The Potential Response of Terrestrial Carbon Storage to Changes in Climate and Atmospheric CO2

We use a georeferenced model of ecosystem carbon dynamics to explore the sensitivity of global terrestrial carbon storage to changes in atmospheric CO₂ and climate. We model changes in ecosystem carbon density, but we do not model shifts in vegetation type. A model of annual NPP is coupled with a model of carbon allocation in vegetation and a model of decomposition and soil carbon dynamics. NPP is a function of climate and atmospheric CO₂ concentration. The CO₂ response is derived from a biochemical model of photosynthesis. With no change in climate, a doubling of atmospheric CO₂ from 280 ppm to 560 ppm enhances equilibrium global NPP by 16.9%; equilibrium global terrestrial ecosystem carbon (TEC) increases by 14.9%. Simulations with no change in atmospheric CO₂ concentration but changes in climate from five atmospheric general circulation models yield increases in global NPP of 10.0–14.8%. The changes in NPP are very nearly balanced by changes in decomposition, and the resulting changes in TEC range from an increase of 1.1% to a decrease of 1.1%. These results are similar to those from analyses using bioclimatic biome models that simulate shifts in ecosystem distribution but do not model changes in carbon density within vegetation types. With changes in both climate and a doubling of atmospheric CO₂, our model generates increases in NPP of 30.2–36.5%. The increases in NPP and litter inputs to the soil more than compensate for any climate stimulation of decomposition and lead to increases in global TEC of 15.4–18.2%.     

‘Invisible gold’ in bismuth chalcogenides

Gold concentrations have been determined by LA-ICPMS in bismuth chalcogenides (tellurides and sulfosalts, minerals with modular structures; chalcogen X = Te, Se, and S) from 27 occurrences. Deposit types include epithermal, skarn, intrusion-related and orogenic gold. The samples comprised minerals of the tetradymite group, aleksite series, bismuth sulfosalts (cosalite, lillianite, hodrushite, bismuthinite, and aikinite), and accompanying altaite. Gold concentrations in phases of the tetradymite group range from <0.1 to 2527 ppm. Phases in which Bi > X tend to contain lower gold concentrations than Bi₂X₃ minerals (tellurobismuthite and tetradymite). Cosalite and lillianite contain Au concentrations ranging up to 574 and 3115 ppm, respectively. Bismuthinite derivatives have lower Au concentrations: <2 ppm in bismuthinite and up to 542 ppm in aikinite. In our samples, Au concentrations in altaite range from <0.2 to 1662 ppm.Smoother parts of the LA-ICPMS profiles suggest lattice-bound gold, whereas irregularities on the profiles are best explained by the presence of gold particles (?1 μm in diameter). Plotting Au vs. Ag for the entire dataset gives a wedge-shaped distribution, suggesting that Ag underpins Au uptake in both bismuth tellurides and sulfosalts. In the tellurides, correlation trends suggest statistical substitution of Ag(Au), together with Pb, into the octahedral site in the layers. In sulfosalts, Au follows coupled substitutions in which M¹⁺ (Ag, Cu) enters the structure. In tellurides, the presence of van der Waals gaps at chalcogen-chalcogen contacts provides for p-type semi-conductive properties critical for gold scavenging from fluids. Such weak bonds may also act as sites for nucleation of Au (nano)particles. In sulfosalts, contacts between different species that replace one another are also highly predictable to act as traps for (nano)particulate gold.Invisible gold in Bi-chalcogenides is useful to (i) identify trends of orefield zonation, (ii) discriminate between ‘melt’ and ‘fluid-driven’ scavenging, and (iii) interpret replacement and remobilisation processes. Bismuth chalcogenides have the potential to be significant Au carriers in sulfide-poor Au systems, e.g., intrusion-related gold, with impact on the overall Au budget if mean Au concentrations are high enough and the minerals are sufficiently abundant.     

Trace and minor elements in sphalerite from metamorphosed sulphide deposits

Sphalerite is a common sulphide and is the dominant ore mineral in Zn-Pb sulphide deposits. Precise determination of minor and trace element concentrations in sulphides, including sphalerite, by Laser-Ablation Inductively-Coupled-Plasma Mass-Spectrometry (LA-ICP-MS) is a potentially valuable petrogenetic tool. In this study, LA-ICP-MS is used to analyse 19 sphalerite samples from metamorphosed, sphalerite-bearing volcanic-associated and sedimentary exhalative massive sulphide deposits in Norway and Australia. The distributions of Mn, Fe, Co, Cu, Ga, Se, Ag, Cd, In, Sn, Sb, Hg, Tl, Pb and Bi are addressed with emphasis on how concentrations of these elements vary with metamorphic grade of the deposit and the extent of sulphide recrystallization. Results show that the concentrations of a group of trace elements which are believed to be present in sphalerite as micro- to nano-scale inclusions (Pb, Bi, and to some degree Cu and Ag) diminish with increasing metamorphic grade. This is interpreted as due to release of these elements during sphalerite recrystallization and subsequent remobilization to form discrete minerals elsewhere. The concentrations of lattice-bound elements (Mn, Fe, Cd, In and Hg) show no correlation with metamorphic grade. Primary metal sources, physico-chemical conditions during initial deposition, and element partitioning between sphalerite and co-existing sulphides are dominant in defining the concentrations of these elements and they appear to be readily re-incorporated into recrystallized sphalerite, offering potential insights into ore genesis. Given that sphalerite accommodates a variety of trace elements that can be precisely determined by contemporary microanalytical techniques, the mineral has considerable potential as a geothermometer, providing that element partitioning between sphalerite and coexisting minerals (galena, chalcopyrite etc.) can be quantified in samples for which the crystallization temperature can be independently constrained.