Development of GIS as a tool in the Ministry of Mining and Energy,Serbia

On behalf of the Serbian Government, the Ministries of Mining and Energy and of Science and Environment Protection are signatories to a master plan for the promotion of the mining industry in Serbia. This is being achieved with the assistance of the Japanese Government through the Japanese International Cooperation Agency (JICA), who engaged a mining company from Tokyo–Mindeco (Mitsui Mineral Development Engineering Co. Ltd) to partner the Serbian ministries, the Mining and Geology Faculty in Belgrade, the Geological Institute of Serbia (Belgrade), the Copper Institute (Bor), and the Military Geographical Institute (Belgrade), as well as private companies dealing in geological exploration, etc. Apart from other things, the master plan contains a newly‐formed GIS application, which registers exploration, exploitation fields and other relevant data. This GIS web application was one the first steps towards the realization of ‘e‐Government’ in the field of geological exploration and mining activities within the Republic of Serbia.     

Tendencies for the amounts of chemical material used for cloud seeding in Serbia

Weather modification activities are performed predominantly by cloud seeding. Some operational projects have been performed for more than half a century and cover planetary scales. These activities lead to a large amount of deposited chemical materials (seeding agents) at the ground level during precipitation. These deposits depend on the amount of the seeding agent. In the future, increased amounts of seeding agent deposits could be a serious problem due to various negative effects on the human environment. Therefore, the main intent of this paper is to determine trends for the seeding agent amount over certain areas of Serbia. Four areas covered by the Hail Suppression Project in Serbia are considered: the target area in central Serbia and areas in western and central Serbia, which are well-known hailfall regions. The annual seeding agent amounts show a slow decreasing trend because fewer seedings were performed during the last decade of the last century, which was due to economic reasons. In contrast, the annual seeding agent amounts of the other analysed areas indicate an increasing trend induced by the transfer of rockets to these hailfall regions. The main difference among small areas is the mean agent amount and its maximum time position as a consequence of the high spatial and time variability of the hail. However, a sharp decreasing trend that is influenced by the implementation of new methodologies, seeding agents and delivery tools may also be a factor in the implementation of cloud seeding projects. The given method is not only strictly applicable locally and may be applied to any other cloud seeding scenario and seeding area. Dominantly increasing trends in the agent amount indicate that the importance of weather modifications in the future will be greater than ever and will have both positive and negative effects.     

Characteristics of the lithospheric mantle beneath East Serbia inferred from ultramafic xenoliths in Palaeogene basanites

Mantle xenoliths from Paleogene basanites of East Serbia were studied using EMP and LA-ICP-MS techniques in order to better understand mantle characteristics in this region. Five different mantle lithologies have been distinguished: a dunite/harzburgite/lherzolite (D/HZ/L) group, clinopyroxene-rich lherzolites (Cpx-L), clinopyroxene megacrysts (Cpx-M), spinel-rich olivine websterites (OWB₁) and spinel-poor olivine websterites (OWB₂). D/HZ/L xenoliths are the most common and represent normal mantle composed of typical anhydrous spinel peridotites with well equilibrated, unzoned silicates characterized by high Mg# s. Negative correlations between Mg# and TiO₂, Al₂O₃ and CaO wt% in clinopyroxenes (cpx) and orthopyroxenes (opx) and the Cr–Al trend in spinel (sp) suggest depletion via extraction of basaltic melts. The modal composition of D/HZ/L xenoliths and unusual low-Al opx suggest that the lithospheric mantle underneath East Serbia is more depleted than normal European lithosphere. D/HZ/L xenoliths contain numerous pockets and veins filled by Cr-rich cpx, Ti-rich spinel, altered glass, apatite and rare ilmenite and phlogopite. Petrographic observations, supported by major element contents in sp and cpx, and modelling using trace element contents in cpx, indicate that the pockets and veins formed from infiltration of alkaline melts and reaction with peridotite wall-rock causing opx and spinel replacement. The same alkaline melt-related metasomatism gave rise to the Cpx-L and OWB₁ mantle xenoliths and Cpx-M xenocrysts. Trace element contents of cpx in these xenoliths show a distinctively concave downwards REE pattern with a HFSE depletion, very similar to cpx megacrysts from the Pannonian Basin and to vein cpx from Eifel. In contrast, the OWB₂ xenoliths show evidence of precipitation from subduction-related mafic to ultramafic melts, as inferred from their opx-rich lithology and unusual Cr-rich spinels. They are probably related to subduction magmatism during the Late Cretaceous.Milivoje Jovanovi: deceased in April 2004     

Geodynamic significance of ultramafic xenoliths from Eastern Serbia: Relics of sub-arc oceanic mantle?

A suite of highly depleted peridotite xenoliths in East Serbian Palaeogene basanites represents the lithospheric mantle beneath the Balkan Peninsula. The xenoliths are harzburgites, clinopyroxene-poor lherzolites and rare dunites. They contain mostly <5 vol.% of modal clinopyroxene and are characterized by high Mg# in silicates (>91), high Cr# in spinel (mostly 0.5–0.7), and by distinctively low Al₂O₃ contents in orthopyroxene (mostly 1–2 wt.%). They have experienced some mantle metasomatism which has slightly obscured their original composition. Nevertheless, the general characteristics of the xenoliths imply a composition which is significantly more depleted than most non-cratonic sub-continental mantle xenolith suites, as well as orogenic peridotites and abyssal peridotites. Geological and compositional evidence suggests that the xenoliths do not represent Archean mantle. The existence of Proterozoic mantle cannot be entirely excluded, although it is in disagreement with geological evidence. On the other hand, the studied xenoliths are compositionally very similar to peridotites of modern oceanic sub-arc settings. The existence of such a depleted lithospheric mantle segment is also inferred from the presence of rare orthopyroxene-rich xenoliths in the same suite. These are interpreted to have originated as lithospheric precipitates of high-Mg, SiO₂-saturated magmas that require a highly depleted mantle source. Such source is typically required by boninitic-like magmas of intraoceanic suprasubduction settings. A proposed geodynamic model to explain these observations involves accretion or underplating of the lower parts of the Tethyan oceanic lithosphere during the Upper Jurassic closure of the eastern branch of the Vardar ocean.     

Thermal emission at radio frequencies from supernova remnants and a modified theoretical Σ–D relation

In this paper, we discuss known discrepancies between theoretically derived and empirically measured relations between the radio surface brightness Σ and the diameter D of supernova remnants (SNRs): these relations are commonly known as the Σ–D relations. We argue that these discrepancies may be at least partially explained by taking into account thermal emission at radio frequencies from SNRs at particular evolutionary stages and located in particular environments. The major contributions of this paper may be summarized as follows: (i) we consider thermal emission at radio frequencies from SNRs in the following scenarios: a relatively young SNR evolving in a dense molecular cloud environment (n  100–1000 cm⁻³) and an extremely evolved SNR expanding in a dense warm medium (n  1–10 cm⁻³). Both of these SNRs are assumed to be in the adiabatic phase of evolution. We develop models of the radio emission from both of these types of SNRs and each of these models demonstrate that through the thermal bremsstrahlung process significant thermal emission at radio frequencies is expected from both types of SNR. Based on a literature search, we claim that thermal absorption or emission at radio frequencies has been detected for one evolved Galactic SNR and four young Galactic SNRs with similar properties to our modelled evolved and young SNRs. (ii) We construct artificial radio spectra for both of these two types of SNRs: in particular, we discuss our simulated spectrum for the evolved Galactic SNR OA 184. By including thermal emission in our simulated spectra, we obtain different slopes in Σ–D relations: these new slopes are in closer agreement to empirically obtained relations than the theoretically derived relations which do not take thermal emission into account. (iii) Lastly, we present an additional modification to the theoretical Σ–D relation for SNRs in the adiabatic expansion phase. This modification is based on the convolution of the synchrotron emissivity with the emissivity derived in this paper for thermal bremsstrahlung emission from an ionized gas cloud (that is, a theoretical construct of an SNR).     

Discs and haloes in pre-main-sequence stars

We study the infrared (IR) emission from flared discs with and without additional optically thin haloes. Flux calculations of a flared disc in vacuum can be considered a special case of the more general family of models in which the disc is imbedded in an optically thin halo. In the absence of such a halo, flux measurements can never rule out its existence because the disc flaring surface defines a mathematically equivalent halo that produces the exact same flux at all IR wavelengths. When a flared disc with height H at its outer radius R is imbedded in a halo whose optical depth at visual wavelengths is  τ_halo  , the system IR flux is dominated by the halo whenever  τ_halo > (1/4) H / R   . Even when its optical depth is much smaller, the halo can still have a significant effect on the disc temperature profile. Imaging is the only way to rule out the existence of a potential halo, and we identify a decisive test that extracts a signature unique to flared discs from imaging observations.     

Graupel growth and trajectories in a shallow cb cloud determined by a forced 1‐D model

Abstract

A kinematic model is applied to graupel growth. The vertical velocity and ther‐modynamic field data are taken from the forced 1‐D time‐dependent model of Cb cloud developed by Curie and Jane (1988). The graupel embryo pocket was released at the height of the — 10°C isotherm. The influence of the forced lifting on further graupel growth and its trajectory is analysed by sensitivity experiments based on the amplitude of the forced lifting, and initial graupel radius, density and cloud droplet concentration for the forced lifting initiation time derived from the model and the forced lifting duration time that agreed with observations. In particular, the sensitivity analysis was carried out for the forced lifting initiation and duration times.

It is shown that for large values of the forced lifting amplitudes, the residence time of the graupel within cloud and the final graupel radius may be significantly larger compared with those in the non‐forced case. The residence time in a cloud can also be significantly larger for the smallest amplitude, whereas the final radius is rather insensitive owing to oscillations around the melting level. For some cases the forced lifting causes recycling inside the updraft, contrary to the results of previous non‐forced numerical models. The recycling mechanism is sensitive to the forced lifting duration time and the time interval between the graupel pocket injection in cloud and the initiation of the forced lifting. Initially the observed recycling mechanism is a consequence of the periodic forced lifting mechanism, but then combines with recycling of the Pflaum type (1980).     

Numerical simulation of Cb cloud vorticity

Vertical vorticity characteristics within individual cumulonimbus (Cb) cloud moving over complex terrain are investigated by cloud-resolving mesoscale model. Orography impact on vorticity is recognized by comparison of its characteristics within the storm moving over flat terrain under the same other conditions. In present study, two cases are considered: complex terrain case (referred to as CT case) and flat terrain case (referred to as FT case). A sensitivity study shows that orographical effects on vorticity are important. Main findings are:

– For CT case vortices produced by convective tilting of horizontal vortices are closer to each other and more stretched in form owing to valley configuration. The vortex with positive vorticity is mainly stronger in magnitude compared to its negative counterpart.

– Magnitudes of vorticities for CT case are greater at lowest levels and initial time intervals compared to those for FT case.

– For CT case the vortices with opposite signs of vorticity produced by precipitation appear later than in FT case. Their duration is shorter and they are weaker in intensity compared to those formed within a cloud over flat terrain.

– Complex terrain intensifies the splitting of simulated cloud.

Dependence of accumulated precipitation on cloud drop size distribution

Convective precipitation is the main cause of extreme rainfall events in small areas. Its primary characteristics are both large spatial and temporal variability. For this reason, the monitoring of accumulated precipitation fields (liquid and solid components) at the surface is difficult to carry out through the use of rain gauge networks or remote-sensing observations. Alternatively, numerical models seem to be the most powerful tool in simulating convective precipitation for various analyses and predictions. Due to a lack of comparisons between modelled and observed precipitation characteristics over a long period of time, we focus our research on comparisons between observations and three model samples of accumulated convective precipitation over a particular study area. We use a numerical cloud model with two model schemes involving the unified Khrgian–Mazin size distribution of cloud drops and a model scheme involving a monodisperse cloud droplet spectrum and the Marshall–Palmer size distribution for raindrops, respectively. For comparison, we have selected a study area with a sounding site. Our analysis shows that the model version with the Khrgian–Mazin size distribution exhibits a better agreement with the observed mean, median and range of extreme values of accumulated convective precipitation. Model simulations with the Khrgian–Mazin size distribution most closely match observations, with a correlation coefficient of 0.91. Use of the Marshall–Palmer size distribution, on the other hand, systemically underestimates the observed precipitation and has the lowest correlation coefficient among the methods, 0.83. Such an investigation is crucial to improve predictions of accumulated convective precipitation for various climatological and hydrological analyses and predictions.