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21.
Identification of extreme events using drought indices and their impact on the Danube lower basin discharge 
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下载免费PDF全文 In this study extreme droughts and extremely wet periods in the Danube upper and middle basin (DUMB) have been highlighted with specific indices. The most widely used indices have been considered to estimate both the dry and wet phenomena severity and the frequency or spatio‐temporal extension. The climatic condition of 15 meteorological stations situated in the Danube basin has been evaluated using four indices: Palmer Drought Severity Index (PDSI), Palmer Hydrological Drought Index (PHDI), Weighted PDSI (WPLM) and Palmer Z‐index (ZIND). The four indices have been analysed separately for each of the four seasons between 1901 and 2000. First the internal structure of the time series of the four indices has been analysed separately. Then the overall temporal characteristic has been analysed by means of the principal component of the Multivariate Empirical Orthogonal Functions decomposition of the four indices (PC1‐MEOF). For the discharge in the Danube lower basin, station Orsova has been chosen, representing an integrator of the discharges from the DUMB. A very close connection has been found between Palmer indices and Danube discharge in all seasons (with correlation coefficients greater then 0.80) excepting the spring season. A classification in five classes of both the four indices separately and the PC1‐MEOF has been achieved in order to highlight extreme events. The impact of phenomena quantified by Palmer indices in DUMB upon discharges in Danube lower basin is evident. It was demonstrated in this study that the Greenland‐Balkan Oscillation (GBO) influences the south‐east European hydro‐climatic regime more than the North Atlantic Oscillation (NAO) Index. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
22.
Mihaela Constantin Aurelian C. Trandafir Marta C. Jurchescu Daniel Ciupitu 《Environmental Earth Sciences》2010,59(7):1569-1578
The May–August 2005 heavy rainstorm events in Romania triggered a large number of geomorphic hazards of great magnitude, consisting
of primarily floods and landslides. Some of the most affected regions were the Curvature Carpathians and Subcarpathians. This
paper addresses the effects of rainfall on slopes, especially in the middle sector of the Sibiciu basin (the Buzău Carpathians)
outlining the significant landslide damage along the road connecting the Colţi and Aluniş villages. The landslides are analyzed
in terms of geologic, geomorphic and engineering geologic features, focusing on the Colţi–Aluniş landslide which had the greatest
impact on the road displacement. The related environmental and social impacts are also discussed. 相似文献
23.
Mihaela I. Chidean Antonio J. Caama&#;o Carlos Casanova-Mateo Julio Ramiro-Bargue&#;o Sancho Salcedo-Sanz 《Theoretical and Applied Climatology》2020,140(3):927-949
The authors present a novel self-organized climate regionalization (CR) method that obtains a spatial clustering of regions, based on the explained variance of physical measurements in their coverage. This method enables a microscopic characterization of the probabilistic spatial extent of climate regions, using the statistics of the obtained clusters. It also allows for the study of the macroscopic behaviour of climate regions through time by using the dissimilarity among different cluster size probability histograms. The main advantages of the presented method, based on the Second-Order Data-Coupled Clustering (SODCC) algorithm, are that SODCC is robust to the selection of tunable parameters and that it does not require a regular or homogeneous grid to be applied. Moreover, the SODCC method has higher spatial resolution, lower computational complexity, and allows for a more direct physical interpretation of the outputs than other existing CR methods, such as Empirical Orthogonal Function (EOF) or Rotated Empirical Orthogonal Function (REOF). These facts are illustrated with an example of winter wind speed regionalization in the Iberian Peninsula through the period (1979 − 2014). This study also reveals that the North Atlantic Oscillation (NAO) has a high influence over the wind distribution in the Iberian Peninsula in a subset of years in the considered period. 相似文献
24.
Landslide susceptibility assessment using the bivariate statistical analysis and the index of entropy in the Sibiciu Basin (Romania) 总被引：13，自引：6，他引：7
Mihaela Constantin Martin Bednarik Marta C. Jurchescu Marius Vlaicu 《Environmental Earth Sciences》2011,63(2):397-406
The Sibiciu Basin is located in Romania between the Buzău Mountains and the Buzau Subcarpathians (Curvature Carpathians and
Subcarpathians). The geology of the basin consists of Paleogene flysch deposits represented by an alternation of sandstones,
marls, clays and schists and Neogene deposits represented by marls, clays and sands. The area is affected by different types
of landslides (shallow, medium-deep and deep-seated failures). In Romania, in the last decades, direct and indirect methods
have been applied for landslide susceptibility assessment. The most utilized before 2000 were based on qualitative approaches.
This study evaluates the landslide susceptibility in the Sibiciu Basin using a bivariate statistical analysis and an index
of entropy. A landslide inventory map was prepared, and a susceptibility estimate was assessed based on the following parameters
which influence the landslide occurrence: slope angle, slope aspect, curvature, lithology and land use. The landslide susceptibility
map was divided into five classes showing very low to very high landslide susceptibility areas. 相似文献
25.
Mihaela Trelea‐Newton Nicholas R. Golledge 《Boreas: An International Journal of Quaternary Research》2012,41(4):614-628
Geomorphological mapping of locally nourished glaciers was conducted in four glens in the southeastern Monadhliath Mountains, Scotland. Three glaciers are interpreted to be of Younger Dryas age based on geomorphological similarity to features in other Scottish upland areas known to have been glaciated during the Younger Dryas, and on comparison to adjacent ice‐free areas in the lower glens where landform‐sediment assemblages typically reflect peri/paraglacial readjustment during the stadial. Here we reconstruct Younger Dryas glacier termini based on moraine alignments and associated geomorphological and sedimentological evidence. An adjacent wide plateau area at high altitude may have permitted extensive ice accumulation, but no unequivocal geomorphological signature is evident. To establish upper glacier limits, a series of ice profiles are modelled. The results yield a range of realistic glacier configurations bracketed between two distinct scenarios: a valley glaciation with the glaciers' upper limit on the plateau edge, and a low‐domed icecap centred on the plateau with ice flowing radially into the lower glens. Reconstructed equilibrium‐line altitudes are 795 m a.s.l. for the valley‐glacier scenario and 894 m a.s.l. for the icecap scenario. Calculated mean ablation‐season temperatures at the ELA are 1.2°C and 0.4°C for the valley‐glacier and the icecap scenario, respectively, from which we infer mean annual precipitation rates between 323 and 520 mm a?1. Palaeoclimate results indicate a stadial climate in central Scotland 65–79% more arid than at present, comparable to that of western Norway for the stadial and to the present‐day Canadian Arctic. 相似文献
26.
Torben Koenigk Christof K?nig Beatty Mihaela Caian Ralf D?scher Klaus Wyser 《Climate Dynamics》2012,38(11-12):2389-2408
Decadal prediction is one focus of the upcoming 5th IPCC Assessment report. To be able to interpret the results and to further improve the decadal predictions it is important to investigate the potential predictability in the participating climate models. This study analyzes the upper limit of climate predictability on decadal time scales and its dependency on sea ice albedo parameterization by performing two perfect ensemble experiments with the global coupled climate model EC-Earth. In the first experiment, the standard albedo formulation of EC-Earth is used, in the second experiment sea ice albedo is reduced. The potential prognostic predictability is analyzed for a set of oceanic and atmospheric parameters. The decadal predictability of the atmospheric circulation is small. The highest potential predictability was found in air temperature at 2?m height over the northern North Atlantic and the southern South Atlantic. Over land, only a few areas are significantly predictable. The predictability for continental size averages of air temperature is relatively good in all northern hemisphere regions. Sea ice thickness is highly predictable along the ice edges in the North Atlantic Arctic Sector. The meridional overturning circulation is highly predictable in both experiments and governs most of the decadal climate predictability in the northern hemisphere. The experiments using reduced sea ice albedo show some important differences like a generally higher predictability of atmospheric variables in the Arctic or higher predictability of air temperature in Europe. Furthermore, decadal variations are substantially smaller in the simulations with reduced ice albedo, which can be explained by reduced sea ice thickness in these simulations. 相似文献
27.
Marius Visarion Serban Veliciu Mihai StefĂnescu Reviewer V. Čermák 《Studia Geophysica et Geodaetica》1978,22(2):196-200
Summary Using heat flow and heat generation measurements together with deep seismic sounding and gravity data, a reasonable geothermal model has been constructed for the Romanian Carpathian Bend. At the level of the MOHO discontinuity the calculated temperatures exhibit conspicuous differences between inner and outer border of the Carpathian Bend and a horizontal gradient of 200–300 °C/100 km in the region is not to be excluded.Paper presented at the KAPG Symposium on Geothermics in Liblice, November 1976. 相似文献
28.
Georges Clauzon Jean-Pierre Suc† Speranta-Maria Popescu† Mariana Marunteanu‡ Jean-Loup Rubino¶ Florian Marinescu‡ Mihaela Carmen Melinte§ 《Basin Research》2005,17(3):437-462
A recently published scenario viewing the Messinian salinity crisis as two evaporitic steps rather than one has led to a search for new indices of the crisis in the Eastern Paratethys. Fluvial processes characterized the southwestern Dacic Basin (Southern Romania, i.e. the Carpathian foredeep) whereas brackish sediments were continuously deposited in its northern part. This is consistent with previously evidenced responses of the Black Sea to the Messinian salinity crisis. High sea‐level exchanges between the Mediterranean Sea and Eastern Paratethys are considered to have occurred just before and just after desiccation of the Mediterranean. This accounts for two successive Mediterranean nannoplankton‐dinocyst influxes into the Eastern Paratethys that, respectively, belong to zones NN 11 and NN 12. Meanwhile, two separate events that gave rise to Lago Mare facies (with Paratethyan Congeria, ostracods and/or dinoflagellate cysts) arose in the Mediterranean Basin in response to these high sea‐level exchanges and located 5.52 and 5.33 Ma (isotopic stages TG 11 and TG 5, respectively), i.e. just before and just after the almost complete desiccation of the Mediterranean). These Lago Mare facies formed independently of lakes with ostracods of the Cyprideis group that developed in the central basins during the final stages of desiccation. The gateway faciliting these water exchanges is not completely identified. A proto‐Bosphorus strait seems unlikely. A plausible alternative route extends from the northern part of the Thessaloniki region up to the Dacic Basin and through Macedonia and the Sofia Basin. The expression ‘Lago Mare’ is chronostratigraphically ambiguous and should be discontinued for this purpose, although it might remain useful as a palaeoenvironmental term. 相似文献
29.
M.H. Engel J. Rafalska-Bloch C.F. Schiefelbein J.E. Zumberge A. Serban 《Organic Geochemistry》1986,10(4-6)
Amino acids and sugars are principal constituents of marine organisms. The condensation of amino acids and sugars is one possible nonenzymatic, early diagenetic pathway for the incorporation of these compounds into more complex geopolymers. In this study, aqueous solutions consisting of l-lysine, l-histidine, l-arginine and d-(+)-glucose were heated (100°C) for up to 288 h. Portions of the melanoidin polymer isolated after heating were reheated in the presence of water (hydrous pyrolysis) for 72 h at 325°C. Reaction products were identified by GC and GC/MS. Stable isotopic (δ13C) and elemental analyses were used to follow thermal evolution.While the initial melanoidin was synthesized from a simple, four component system, the products generated during hydrous pyrolysis are of considerable complexity, and include straightchain and branched alkanes, alkadienes, alkynes, indole, dimethyl indane, ethyl phenol, quinoline, and xylenes, in addition to a multitude of as yet, unidentified components. Stable carbon isotopic values for the reactants and products correspond to trends observed for naturally generated geopolymers and light gases. Elemental analyses of the melanoidin prior and subsequent to hydrous pyrolysis indicate a kerogen evolution pathway similar to that observed for natural samples. Considering the intractable nature of kerogen, laboratory simulation studies of simple systems can provide an alternative approach for elucidating the origins of geopolymers and their potential for hydrocarbon generation. 相似文献
30.
Quantitative analysis of variations in morphological types of charcoal were undertaken in sediment cores from three lakes
on the Interior Plateau (BC, Canada) over the period AD 1919–2000. Seven distinct morphological types of charcoal were identified
based on particle shape and structural features and were compared with seasonal precipitation and recorded area burned within
20 km-radius of study lakes. Fragile-type charcoal fragments, termed type M, displayed significant relationships to recorded
area burned in sediment cores from Prosser (r
2 = 0.5; p = 0.0001) and Opatcho (r
2 = 0.2; p = 0.02) lakes. However, nonsignificant correlations (p > 0.05) were found between total charcoal and area burned. Robust and highly elongated morphotypes C and F were correlated
to recorded spring precipitation (r
2 = 0.5; p = 0.002) in Opatcho Lake. Charcoal from a sediment core from Big Lake, the lake with the largest watershed, was significantly
but inversely related to past fires (r
2 = 0.44; p = 0.0003), suggesting important contributions from secondary transportation and deposition. Models were developed to infer
relative area burned and precipitation for the study lakes. Our results suggest that charcoal morphotypes are related to the
biogeoclimatic and lake watershed characteristics. This study also suggest that charcoal morphotypes can provide insights
on past fire and climate, which was not possible based on traditional analysis of total charcoal. 相似文献