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71.
Changes of snow cover in Poland 总被引:2,自引:2,他引:0
Małgorzata Szwed Iwona Pińskwar Zbigniew W. Kundzewicz Dariusz Graczyk Abdelkader Mezghani 《Acta Geophysica》2017,65(1):65-76
The present paper examines variability of characteristics of snow cover (snow cover depth, number of days with snow cover and dates of beginning and end of snow cover) in Poland. The study makes use of a set of 43 long time series of observation records from the stations in Poland, from 1952 to 2013. To describe temporal changes in snow cover characteristics, the intervals of 1952–1990 and of 1991–2013 are compared and trends in analysed data are sought (e.g., using the Mann–Kendall test). Observed behaviour of time series of snow-related variables is complex and not easy to interpret, for instance because of the location of the research area in the zone of transitional moderate climate, where strong variability of climate events is one of the main attributes. A statistical link between the North Atlantic Oscillation (NAO) index and the snow cover depth, as well as the number of snow cover days is found. 相似文献
72.
Studia Geophysica et Geodaetica - Msplit(q) estimation is a development of M-estimation which is based on the assumption that a functional model of observations can be split into q competitive... 相似文献
73.
The Nysa K
odzka river drainage basin in the Sudeten Mts., SW Poland, preserves a complex late Cainozoic succession that includes eight fluvial series or terraces and deposits from two glacial episodes as well as local volcanic rocks, slope deposits and loess. Fluvial sedimentation took place during the Late Pliocene and from the early Middle Pleistocene (Cromerian), with a long erosion phase (gap) during the Early Pleistocene. Fluvial series are dated to the Late Pliocene, Cromerian, Holsteinian, late Saalian/Eemian, Weichselian, and the Holocene. Glacial deposits represent the early Elsterian and early Saalian stages. Almost all these stratigraphic units have been observed in all geomorphic zones of the river: the mountainous K
odzko Basin, the Bardo Mts. (Bardo gorge) and in the mountain foreland. The main phase of tectonic uplift and strong erosion was during the Early Pleistocene. Minor uplift is documented also during the post-early Saalian and probably the post-Elsterian. The post-early Saalian and post-Elstrian uplift phases are probably due to glacio-isostatic rebound. The Quaternary terrace sequence was formed due to base-level changes, epigenetic erosion after glaciations and neotectonic movements. The Cromerian fluvial deposits/terraces do not indicate tectonic influence at all. All other Quaternary terraces indicate clear divergence, and the post-early Saalian terraces also show fault scarps. The fluvial pattern remained stable, once formed during the Pliocene, with only minor changes along the uplifted block along the Bardo gorge, inferring an antecedent origin for the Bardo gorge. Only during the post-glacial times, have epigenetic incisions slightly modified the valley. 相似文献
74.
75.
Wiesław Wiśniewolski Jerzy Nabiałek 《Aquatic Sciences - Research Across Boundaries》1993,55(2):143-152
Fish survival, tag retention and tag loss were evaluated in pond experiments and described by linear regression equations. Tagging of fish had no significant influence on their survival. However, loss of tags caused strong differences between actual fish survival and the survival rate e–z estimated on recovered tags. Mathematical functions were derived to correct tag loss. Values of those functions depend upon the type of tag and time after tagging. The B-type of tagging, which approximated the Swedish Carlin method, appeared to be most effective. The rate of tag loss was independent of the fish species (common carp, tench) used in the experiments. 相似文献
76.
The studies presented explore post-depositional changes of zinc, cadmium, lead, manganese and 137Cs distribution in alluvial sediments accumulated in the upper Odra River valley in southern Poland. The rate of these changes
was estimated by comparing metal and 137Cs distributions in four vertical alluvial profiles with a history of river pollution and sediment deposition. The untypical
137Cs distribution with peaks in the surface 40–60 cm and lower down, even at a depth of 2.5 m in strata deposited before the
beginning of nuclear tests in 1954, indicates rapid post-depositional migration of this isotope from the surface and its retention
in lower, less permeable layers. Moreover, the highest concentrations of lead, zinc and cadmium were found at a depth of 4 m
in sediments accumulated in the mid-nineteenth century in spite of the growth of industrialization and the pollution of the
Odra River with heavy metals until the end of the twentieth century. The post-depositional changes in heavy metals and 137Cs are rapid in comparison with the slow element migration usually observed in uninundated soils. This difference is explained
by the frequent and easy infiltration of polluted river water into the gravelly and sandy sediments present in the profiles. 相似文献
77.
The integrated effects of climate and hydrologic uncertainty on future flood risk assessments 总被引:2,自引:0,他引:2
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This work examines future flood risk within the context of integrated climate and hydrologic modelling uncertainty. The research questions investigated are (1) whether hydrologic uncertainties are a significant source of uncertainty relative to other sources such as climate variability and change and (2) whether a statistical characterization of uncertainty from a lumped, conceptual hydrologic model is sufficient to account for hydrologic uncertainties in the modelling process. To investigate these questions, an ensemble of climate simulations are propagated through hydrologic models and then through a reservoir simulation model to delimit the range of flood protection under a wide array of climate conditions. Uncertainty in mean climate changes and internal climate variability are framed using a risk‐based methodology and are explored using a stochastic weather generator. To account for hydrologic uncertainty, two hydrologic models are considered, a conceptual, lumped parameter model and a distributed, physically based model. In the conceptual model, parameter and residual error uncertainties are quantified and propagated through the analysis using a Bayesian modelling framework. The approach is demonstrated in a case study for the Coralville Dam on the Iowa River, where recent, intense flooding has raised questions about potential impacts of climate change on flood protection adequacy. Results indicate that the uncertainty surrounding future flood risk from hydrologic modelling and internal climate variability can be of the same order of magnitude as climate change. Furthermore, statistical uncertainty in the conceptual hydrological model can capture the primary structural differences that emerge in flood damage estimates between the two hydrologic models. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
78.
79.
M-estimation with probabilistic models of geodetic observations 总被引:1,自引:1,他引:0
Z. Wiśniewski 《Journal of Geodesy》2014,88(10):941-957
The paper concerns \(M\) -estimation with probabilistic models of geodetic observations that is called \(M_{\mathcal {P}}\) estimation. The special attention is paid to \(M_{\mathcal {P}}\) estimation that includes the asymmetry and the excess kurtosis, which are basic anomalies of empiric distributions of errors of geodetic or astrometric observations (in comparison to the Gaussian errors). It is assumed that the influence function of \(M_{\mathcal {P}}\) estimation is equal to the differential equation that defines the system of the Pearson distributions. The central moments \(\mu _{k},\, k=2,3,4\) , are the parameters of that system and thus, they are also the parameters of the chosen influence function. The \(M_{\mathcal {P}}\) estimation that includes the Pearson type IV and VII distributions ( \(M_{\mathrm{PD(l)}}\) method) is analyzed in great detail from a theoretical point of view as well as by applying numerical tests. The chosen distributions are leptokurtic with asymmetry which refers to the general characteristic of empirical distributions. Considering \(M\) -estimation with probabilistic models, the Gram–Charlier series are also applied to approximate the models in question ( \(M_{\mathrm{G-C}}\) method). The paper shows that \(M_{\mathcal {P}}\) estimation with the application of probabilistic models belongs to the class of robust estimations; \(M_{\mathrm{PD(l)}}\) method is especially effective in that case. It is suggested that even in the absence of significant anomalies the method in question should be regarded as robust against gross errors while its robustness is controlled by the pseudo-kurtosis. 相似文献
80.
Kazimierz Więski Hongyu Guo Christopher B. Craft Steven C. Pennings 《Estuaries and Coasts》2010,33(1):161-169
We examined patterns of habitat function (plant species richness), productivity (plant aboveground biomass and total C), and nutrient stocks (N and P in aboveground plant biomass and soil) in tidal marshes of the Satilla, Altamaha, and Ogeechee Estuaries in Georgia, USA. We worked at two sites within each salinity zone (fresh, brackish, and saline) in each estuary, sampling a transect from the creekbank to the marsh platform. In total, 110 plant species were found. Site-scale and plot-scale species richness decreased from fresh to saline sites. Standing crop biomass and total carbon stocks were greatest at brackish sites, followed by freshwater then saline sites. Nitrogen stocks in plants and soil decreased across sites as salinity increased, while phosphorus stocks did not differ between fresh and brackish sites but were lowest at salty sites. These results generally support past speculation about ecosystem change across the estuarine gradient, emphasizing that ecosystem function in tidal wetlands changes sharply across the relatively short horizontal distance of the estuary. Changes in plant distribution patterns driven by global changes such as sea level rise, changing climates, or fresh water withdrawal are likely to have strong impacts on a variety of wetland functions and services. 相似文献