Flow in open channels under the influence of ice cover     

Wojciech Majewski 《Acta Geophysica》2007,55(1):11-22

During winters in Poland, lakes, ponds, rivers, channels, run-of-reservoirs, ditches and streams are covered with ice, which changes significantly the flow and thermal conditions in water bodies. The paper presents a very complicated process of ice formation on stagnant and flowing waters. Various kinds of ice are described together with their consequences for flow and thermal conditions. The possibility to define flow conditions in open channels with ice cover is described. In 1982, a significant flood on Włocławek Reservoir (Lower Vistula River) appeared, which was caused by the coincidence of unfavourable, extreme hydrological and meteorological conditions. These conditions, as well as the run and consequences of the flood, are described. Detailed field measurements of ice cover and flow were carried out. One-dimensional model for steady nonuniform flow was developed and applied to the conditions existing in 1982 on the Włocławek Reservoir.  相似文献   

On the influence of microphysics parametrization on the rainfall rates in numerical models of clouds     

Wojciech W. Grabowski 《Pure and Applied Geophysics》1985,123(6):941-950

Accuracy of formulas for growth by accretion and evaporation of rain in bulk parametrization of these processes for the case of light and moderate precipitation is investigated. It is done by comparison of results from two simple models: with bulk approach and with exact calculations of growth or evaporation of drops in each size bin separately. Growth by accretion is accurately represented in bulk parametrization but rain evaporation is overpredicted. Corrected formula for rain evaporation is suggested.  相似文献   

Holocene climate and glacial history of the northeastern Antarctic Peninsula: the marine sedimentary record from a long SHALDRIL core     

Bradley R. Michalchuk  John B. Anderson  Julia S. Wellner  Patricia L. Manley  Wojciech Majewski  Steve Bohaty 《Quaternary Science Reviews》2009,28(27-28):3049-3065

A high-resolution record of Holocene deglacial and climate history was obtained from a 77 m sediment core from the Firth of Tay, Antarctic Peninsula, as part of the SHALDRIL initiative. This study provides a detailed sedimentological record of Holocene paleoclimate and glacial advance and retreat from the eastern side of the peninsula. A robust chronostratigraphy was derived from thirty-three radiocarbon dates on carbonate material. This chronostratigraphic framework was used to establish the timing of glacial and climate events derived from multiple proxies including: magnetic susceptibility, electric resistivity, porosity, ice-rafted debris content, organic carbon content, nitrogen content, biogenic silica content, and diatom and foraminiferal assemblages. The core bottomed-out in a stiff diamicton interpreted as till. Gravelly and sandy mud above the till is interpreted as proximal glaciomarine sediment that represents decoupling of the glacier from the seafloor circa 9400 cal. yr BP and its subsequent landward retreat. This was approximately 5000 yr later than in the Bransfield Basin and South Shetland Islands, on the western side of the peninsula. The Firth of Tay core site remained in a proximal glaciomarine setting until 8300 cal. yr BP, at which time significant glacial retreat took place. Deposition of diatomaceous glaciomarine sediments after 8300 cal. yr BP indicates that an ice shelf has not existed in the area since this time.The onset of seasonally open marine conditions between 7800 and 6000 cal. yr BP followed the deglacial period and is interpreted as the mid-Holocene Climatic Optimum. Open marine conditions lasted until present, with a minor cooling having occurred between 6000 and 4500 cal. yr BP and a period of minor glacial retreat and/or decreased sea ice coverage between 4500 and 3500 cal. yr BP. Finally, climatic cooling and variable sea ice cover occurred from 3500 cal. yr BP to near present and it is interpreted as being part of the Neoglacial. The onset of the Neoglacial appears to have occurred earlier in the Firth of Tay than on the western side of the Antarctic Peninsula. The Medieval Warm Period and Little Ice Age were not pronounced in the Firth of Tay. The breadth and synchroneity of the rapid regional warming and glacial retreat observed in the Antarctic Peninsula during the last century appear to be unprecedented during the Holocene epoch.  相似文献   

Various Approaches to Forward and Inverse Wide-Angle Seismic Modelling Tested on Data from DOBRE-4 Experiment     

Tomasz Janik  Piotr Środa  Wojciech Czuba  Dmytro Lysynchuk 《Acta Geophysica》2016,64(6):1989-2019

The interpretation of seismic refraction and wide angle reflection data usually involves the creation of a velocity model based on an inverse or forward modelling of the travel times of crustal and mantle phases using the ray theory approach. The modelling codes differ in terms of model parameterization, data used for modelling, regularization of the result, etc. It is helpful to know the capabilities, advantages and limitations of the code used compared to others.This work compares some popular 2D seismic modelling codes using the dataset collected along the seismic wide-angle profile DOBRE-4, where quite peculiar/uncommon reflected phases were observed in the wavefield.The ~505 km long profile was realized in southern Ukraine in 2009, using 13 shot points and 230 recording stations. Double P_MP phases with a different reduced time (7.5–11 s) and a different apparent velocity, intersecting each other, are observed in the seismic wavefield. This is the most striking feature of the data. They are interpreted as reflections from strongly dipping Moho segments with an opposite dip. Two steps were used for the modelling. In the previous work by Starostenko et al. (2013), the trial-and-error forward model based on refracted and reflected phases (SEIS83 code) was published. The interesting feature is the high-amplitude (8–17 km) variability of the Moho depth in the form of downward and upward bends. This model is compared with results from other seismic inversion methods: the first arrivals tomography package FAST based on first arrivals; the JIVE3D code, which can also use later refracted arrivals and reflections; and the forward and inversion code RAYINVR using both refracted and reflected phases. Modelling with all the codes tested showed substantial variability of the Moho depth along the DOBRE-4 profile. However, SEIS83 and RAYINVR packages seem to give the most coincident results.  相似文献   

Airborne Fungal Spores of Subalpine Zone of the Karkonosze and Izerskie Mountains （Poland）   总被引：4，自引：1，他引：3  

Wojciech PUSZ  Wlodzimierz KITA  Andrzej DANCEWICZ  Ryszard WEBER 《山地科学学报》2013,10(6):940-952

The incidence of the airborne fungal spores was determined in the air of subalpine zone of the Karkonosze Mountains and of the Izerskie Mountains in the borderland between Poland and the Czech Republic. The experiment was conducted in 2011 and 2012 at three to four week intervals from May to October. Air samples were taken from three locations in the Karkonosze Mts. and one from the Izerskie Mts. To examine the air, the Air Ideal 3P sampler and acidified PDA medium were used. The results show that Cladosporium cladosporioides was the most abundant spore type in all the sampling locations （up to 30%）, followed by Alternaria alternata （16%-20%）, Fusarium （up to 10%） and Sclerotinia sclerotiorium （up to 6%）. The lower spore counts were recorded in May samples, compared to the other months. In this case the snow cover, that was still present in the area at the beginning of May, may be the reason for the lower, compared to June, July and August samplings, CFU （Colony Forming Unit） counts in that month.. The influx of air masses from SE, S and SW sectors in the area under study may affect dissemination of the plant-pathogenic fungi from the Czech Republic and from the South of Europe in general.  相似文献   

Estimating the Earthquake Source Time Function by Markov Chain Monte Carlo Sampling     

Wojciech Dȩbski 《Pure and Applied Geophysics》2008,165(7):1263-1287

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Sediment lithology and stable isotope composition of organic matter in a core from a cirque in the Krkonoše Mountains,Czech Republic     

Zbyněk Engel  Grzegorz Skrzypek  Debajyoti Paul  Wojciech Drzewicki  Daniel Nývlt 《Journal of Paleolimnology》2010,43(4):609-624

This study presents detailed lithostratigraphy and stable carbon and nitrogen isotopic variations in a 520-cm-long sediment core from a cirque basin in the Labsky důl Valley, Krkonoše Mountains, Czech Republic. Detailed study of the core reveals five major periods of sedimentation during the last 7600 years: silt and sand deposition during ~7.6–5.1 ka cal BP, Sphagnum peat accumulation during ~5.1–4.0 ka cal BP, sandy silt and sand during ~4.0–2.8 ka cal BP, raised peat bog during ~2.8–2.0 ka cal BP (Sphagnum peat), and sedimentation of sandy silt since ~2.0 ka cal BP. The δ¹³C values of the organic matter in the core vary in the range typical for C3 plants, from −24.35 to −27.68‰, whereas the δ¹⁵N values vary from −2.65 to +4.35‰. Core sections having ash contents ≥70% have δ¹⁵N > 1‰ and δ¹³C < −26‰, whereas those having ≤70% ash content have δ¹⁵N < 1‰ and δ¹³C > −26‰. Strong linear correlations are observed between δ¹³C and δ¹⁵N values as well as between C:N ratios and δ¹⁵N values in the horizons with ash content >10%, primarily for sand and silt horizons. On the other hand, poor correlations between δ¹³C and C:N ratio, as well as δ¹⁵N and C:N ratio, were observed in Sphagnum peat layers (45–125 and 185–265 cm). We conclude that the primary stable isotope variations are not preserved in the layers where significant correlation between δ¹⁵N and C:N ratio is observed. The relatively small δ¹³C variation in the uppermost Sphagnum peat layer suggests stable temperature during ~2.8–2.0 ka cal BP.  相似文献   

Mycobiota of the disused ore mine of Marcinków in?nie?nik Masiff(western Poland)     

Wojciech Pusz  Anna Baturo-Cieśniewska  Paweł Zagożdżon  Rafał Ogórek 《山地科学学报》2017,14(12):2448-2457

Marcinków(Lower Silesia, ?nie?nik Masiff,south-western Poland) has been a well-known mining centre since the mid-15 th century. Mineral extraction ended in 1949 with the ores of Pb, Ag, Cu and occasionally Au, U or graphite mined there. The mine is surrounded by metamorphic graphite and mica schist. It is not open to the public and no bats have been recorded living in. The aim of this study was the mycological analysis of the air, the rock surface and the water of the disused ore mine of Marcinków.Additionally, the chemical composition of rocks and water, and microclimate conditions of the adit were determined. Fungi were identified using a combination of phenotypic and molecular methods.Six taxa of fungi were cultured from the indoor air samples of the adit, whereas the outdoor air samples contained only five taxa. On the other hand, nine taxa were isolated from both the rocky walls and the water.The Aspergillus group was present only on the rocks and in the water, whereas Cladosporium herbarum,Dumontinia tuberosa, Epicoccum nigrum, Hirsutella sp., were found exclusively in the air. The mycobiota found in the ore mine were mostly similar to those recorded in other mines and natural caves. However,it should be noted that the internal microclimate and chemical compounds of the rocks.  相似文献   

Sedimentary anatomy and hydrological record of relic fluvial deposits in a karst cave conduit     

Pavel Bella  Micha&#x; Gradzi&#x;ski  Helena Hercman  Stanis&#x;aw Leszczy&#x;ski  Wojciech Nemec 《Sedimentology》2021,68(1):425-448

This case study from the renowned Demänová Cave System in the Carpathians of Slovakia demonstrates that the conventional methods of fluvial sedimentology, combined with an allostratigraphic mapping and speleothem U‐series isotopic dating, can give unprecedented insights into the hydrological history of underground karst conduit. The deposits studied are a relic compound sidebar ranging from gravel to mud and encapsulating the conduit’s hydrological history from the middle Pleistocene to the present time. A succession of 10 allostratigraphic units, time‐constrained by speleothems, are recognized in the sidebar deposits, and the corresponding morphodynamics of an evolving cave‐floor sedimentation are reconstructed in considerable detail. The subterranean river water stages recognized from the deposits, time‐constrained by flowstone layers and stalagmites, correlate with and add to the regional record of climate changes. Two distinct episodes of flow ponding (high‐stage slackwater conditions) are recognized and attributed to the independently documented downstream cave‐roof collapses, probably triggered by the Carpathian post‐orogenic earthquakes. This multidisciplinary study may serve as a useful methodological guide for the analysis of fluviokarstic deposits in speleological research and reconstruction of their hosting cave hydrological history.  相似文献   

Modeling of propagation and transformation of transient nonlinear waves on a current     

Wojciech Sulisz  Maciej Paprota 《中国海洋工程》2013,27(5):579-592

A novel theoretical approach is applied to predict the propagation and transformation of transient nonlinear waves on a current. The problem was solved by applying an eigenfunction expansion method and the derived semi-analytical solution was employed to study the transformation of wave profile and the evolution of wave spectrum arising from the nonlinear interactions of wave components in a wave train which may lead to the formation of very large waves. The results show that the propagation of wave trains is significantly affected by a current. A relatively small current may substantially affect wave train components and the wave train shape. This is observed for both opposing and following current. The results demonstrate that the application of the nonlinear model has a substantial effect on the shape of a wave spectrum. A train of originally linear and very narrow-banded waves changes its one-peak spectrum to a multi-peak one in a fairly short distance from an initial position. The discrepancies between the wave trains predicted by applying the linear and nonlinear models increase with the increasing wavelength and become significant in shallow water even for waves with low steepness. Laboratory experiments were conducted in a wave flume to verify theoretical results. The free-surface elevations recorded by a system of wave gauges are compared with the results provided by the nonlinear model. Additional verification was achieved by applying a Fourier analysis and comparing wave amplitude spectra obtained from theoretical results with experimental data. A reasonable agreement between theoretical results and experimental data is observed for both amplitudes and phases. The model predicts fairly well multi-peak spectra, including wave spectra with significant nonlinear wave components.  相似文献