On the stability of a coupled ocean atmosphere system in the presence of wave-CISK

The stability of a simple coupled ocean-atmosphere system similar to the one studied by Hirst with general ocean thermodynamics is investigated in which the atmospheric heating is determined by sea surface temperature anomalies as well as the convergence feedback (low level moisture convergence by the waves themselves). It is shown that the unstable coupled mode found by Hirst (UH mode) is profoundly modified by the convergence feedback. The feedback increases the unstable range of the UH mode and can increase its growth rate several folds. The maximally growing UH mode can become westward propagating for certain strength of convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal modes are also introduced. These modes are basically ‘advective’ modes. For relatively weak strengths of the convergence feedback the growth rates of these modes are smaller than that of the UH mode. As the atmosphere approaches ‘moist neutral’ state, the growth rates of these modes could become comparable or even larger than that of the UH mode. It is argued that these results explain why the El Nino and Southern Oscillation (ENSO) signal is clear in the eastern Pacific but not so in the western Pacific and they may also explain some of the differences between individual ENSO events. Our results also explain the aperiodic behaviour of some coupled numerical models. Importance of this process in explaining the observed aperiodicity of the ENSO phenomenon is indicated.     

Bioconcentration factors for petroleum hydrocarbons, PAHs, LABs and biogenic hydrocarbons in the blue mussel

Bioconcentration factors (K_bc) for petroleum hydrocarbons, PAHs, LABs and biogenic hydrocarbons in Mytilus edulis were measured in field experiments using time-integrating water samplers. Seven deployments at five sites gave lipid weight K_bcs for total hydrocarbons ranging from 0.99 × 10⁶ to 3.1 × 10⁶ (mean 1.6 × 10⁶)—a narrower range than has been obtained previously. Bioconcentration factors for the PAHs were similar to those for total hydrocarbons where the major hydrocarbon source was oil. However, at other sites the factors for PAHs were an order of magnitude lower than those for petroleum and for hydrocarbons originating from algae. Compositional profiles for the linear alkyl benzenes (LABs) suggested that these compounds were assimilated primarily from the dissolved phase, despite their greater abundance on particles.     

Effect of spatial resolution on regionalization of hydrological model parameters

Lack of availability of historical data series is one of the major hindrances in hydrological modelling. Regionalization of hydrological model parameters is one of the solutions to obtain the parameters for ungauged basins. Recently, lots of methodologies have been developed. They can be categorized as model calibration then fitting regression between model parameters and catchments characteristics, using some kind of transfer function. The aim of this study was to compare different regionalization methods as well as to look how the spatial resolution affects regionalization. In this study, a modified Lipschitz and monotony condition was used for regionalization. To identify the effect of the model resolution, the parameters of a distributed and semi‐distributed version of the Hydrologiska Byråns Vattenbalansavdelning (HBV) model were regionalized. The study was conducted at the upper Neckar catchment of southwest Germany. It has been found that the combination of Lipschitz and monotony condition has performed reasonably. It has been seen that the distributed model structure has outperformed the semi‐distributed model structure. It shows under present data conditions that higher model resolution can describe processes of ungauged basins reasonably. Copyright © 2011 John Wiley & Sons, Ltd.     

Sm–Nd and Sr isotope systematics of scheelite from the giant Au(–W) deposit Muruntau (Uzbekistan): implications for the age and sources of Au mineralization

The application of the Sm-Nd isotope system of scheelite to dating of low-sulfide, quartz-vein hosted Au mineralization is still under discussion. In the present work, new Sm-Nd and Rb-Sr data for scheelite from the giant Muruntau/Myutenbai Au deposit (Kyzylkum, Western Uzbekistan) are discussed. Based on the geological relationship, mineralogical properties, and trace element characteristics, two types of scheelite can be distinguished within the deposit. The first one is represented by early bluish luminescent and weakly coloured scheelite (generation 1) found within strongly deformed flat quartz veins. The apparent isochron defined by this scheelite (351ᆪ Ma) is interpreted as a mixing line. Typically brownish to orange and yellowish luminescent scheelite from steeply dipping veins (generation 2) defines a Sm-Nd isochron age of 279ᆦ Ma ()_Nd=-9.5ǂ.3; MSWD: 1.5). No evidence for mixing or disturbance by late alteration were found for these scheelites. This Sm-Nd isochron age agrees with the Rb-Sr and K-Ar age range for wall rock alteration in this deposit reported previously. The age of 280 Ma is interpreted to date the high-grade ore formation in the Muruntau deposit. There are currently no reliable age data available on the magmatic events in the Muruntau region. Probably, there is some overlap in time of the Hercynian gold deposition with the intrusion of lamprophyric dykes. The Nd and Sr isotopic signatures of scheelite define the wall rocks (mainly metasiltstones and metasandstones) as the most probable sources for these elements in scheelite.     

Forecasting weather radar propagation conditions

Summary The increasing use of weather radar quantitative precipitation estimates, particularly in automatic applications such as operational hydrometeorological modelling or assimilation in numerical weather prediction (NWP) models, has promoted the development of quality control procedures on radar data. Anomalous propagation (AP) of the radar beam due to deviation from the standard refractivity vertical profile, is one of the factors that may affect seriously the quality of radar observations because of the increase in quantity and intensity of non-precipitating clutter echoes and consequent contamination of the estimated rainfall field. Another undesired effect of AP is the change in the expected radar echo height, which may be relevant when correcting for beam blockage in radar rainfall estimation in complex terrain. The aim of this paper is to study the use of NWP mesoscale forecasts to predict and monitor AP events. A nested 15-km grid resolution version of the MASS model has been used to retrieve refractivity profiles in the coastal area of Barcelona, near a weather radar and a radiosonde station. Using the refractivity profiles two different magnitudes were computed: the vertical refractivity profile of the lowest 1000 m layer and a ducting index which describes the existence and intensity of the most super-refractive layer contained in the lowest 3-km layer. A comparison between model forecasts and radiosonde diagnostics during a six-month period showed that the model tended to underestimate the degree of super-refraction, with a bias of 4 km⁻¹ and RMSE of 11 km⁻¹ in the 1-km vertical refractivity gradient. Further analysis of the data showed that a combination of previous observations and forecasts allowed to produce modified forecasts improving the original direct model output, decreasing substantially the bias, reducing the RMSE by 20% and improving the skill by 40%, beating also radiosonde observations persistence.     

Structural controls of lode-gold mineralization by mafic dykes in late-Paleozoic granitoids of the Kochkar district, southern Urals, Russia

The Kochkar gold district in the East Uralian Zone of the southern Urals is located in late-Paleozoic granite gneisses of the Plast massif. Gold mineralization is associated with tabular quartz lodes that are preferentially developed along the margins of easterly trending mafic dykes. Fabric development indicates that dykes had a profound influence on the development of shear zones in granitoids. ENE- and SE-trending dykes have been reactivated as dextral and sinistral oblique strike-slip shear zones, respectively, forming a set of approximately conjugate shear zones related to the Permian, regional-scale E-W directed shortening. Dyke-shear zone relationships in the Plast massif are the result of strain refraction due to the presence of biotite-rich, incompetent dykes in more competent granite-gneisses. Deformation and the formation of associated gold-quartz lodes occurred close to peak-metamorphic, upper-greenschist to lower-amphibolite facies conditions. Strain refraction has resulted in partitioning of the bulk strain into a component of non-coaxial mainly ductile shear in mafic dykes, and a component of layer-normal pure shear in surrounding granitoids where deformation was brittle-ductile. Brittle fracturing in granitoids has resulted in the formation of fracture permeabilities adjacent to sheared dykes, that together with the layer-normal dilational component, promoted the access of mineralizing fluids. Both ore-controlling dykes and gold-quartz lodes were subsequently overprinted by lower greenschist-facies, mainly brittle fault zones and associated hydrothermal alteration that post-date gold mineralization. Received: 15 October 1998 / Accepted: 18 August 1999     

Rock albedo and monitoring of thermal conditions in respect of weathering: some expected and some unexpected results

Broadly speaking, there is, at least within geomorphic circles, a general acceptance that rocks with low albedos will warm both faster and to higher temperatures than rocks with high albedos, reflectivity influencing radiative warming. Upon this foundation are built notions of weathering in respect of the resulting thermal differences, both at the grain scale and at the scale of rock masses. Here, a series of paving bricks painted in 20 per cent reflectivity intervals from black through to white were used to monitor albedo‐influenced temperatures at a site in northern Canada in an attempt to test this premise. Temperatures were collected, for five months, for the rock surface and the base of the rock, the blocks being set within a mass of local sediment. Resulting thermal data did indeed show that the dark bricks were warmer than the white but only when their temperatures were equal to or cooler than the air temperature. As brick temperature exceeded that of the air, so the dark and light bricks moved to parity; indeed, the white bricks frequently became warmer than the dark. It is argued that this ‘negating’ of the albedo influence on heating is a result of the necessity of the bricks, both white and black, to convect heat away to the surrounding cooler air; the darker brick, being hotter, initially convects faster than the white as a product of the temperature difference between the two media. Thus, where the bricks become significantly hotter than the air, they lose energy to that air and so their respective temperatures become closer, the albedo influence being superceded by the requirement to equilibrate with the surrounding air. It is argued that this finding will have importance to our understanding of weathering in general and to our perceptions of weathering differences between different lithologies. Copyright © 2005 John Wiley & Sons, Ltd.     

The magmatic evolution of the Seiland province,and Caledonian plate boundaries in northern Norway

The synorogenic intrusive activity of the eastern part of the Seiland province evolved from tholeiitic basalt low in K and Ti, through high-K calc-alkaline magmas and possible transitional basalt, to alkaline olivine basalt and picrite; finally, highly differentiated alkaline magmas and carbonatites were emplaced. For intrusive rocks with equivalent SiO₂ contents, K₂O, K₂O + Na₂O and K₂O/Na₂O increased with time, and the degree of iron enrichment in basaltic suites dimished. The western part of the province shows no equivalent evolution, tholeiitic magmas being emplaced at the same time as calc-alkaline magmas to the east.The magmatism is believed to have stemmed from a diapiric complex established in the mantle above a Benioff zone dipping to the east beneath the deforming Andean-type margin of the Baltic plate. Tectonic shortening of the continental edge and rearward movement of the underthrust plate relative to the asthenosphere resulted in migration of the plate junction, steepening of the seismic zone, and increasing depth to the magmagenetic region.