Exploratory analysis of paleoecological data using the program CanoDraw     

Petr Šmilauer 《Journal of Paleolimnology》1994,12(2):163-169

This paper attempts to persuade the reader that methods of direct gradient analysis may serve as a basis for more detailed exploration of the data and that these exploration methods can be also used for checking the appropriateness of the assumptions of the applied ordination method. Generalized linear models and generalized loess smoothing together with several ways of data presentation are used to explore a sample data set.  相似文献   

On the occurrence of blue asymmetry in chromospheric flare spectra   总被引：1，自引：0，他引：1  

Petr Heinzel  Marian Karlický  Pavel Kotrč  Zdeněk Švestka 《Solar physics》1994,152(2):393-408

We present observations of optical spectra of a flare in which blue line asymmetry was seen for more than 4 min close to the flare onset. The maximum blue asymmetry coincided with the maximum of a hard X-ray and microwave burst. We discuss possible interpretations of the blue asymmetry and conclude that the most plausible one is electron-beam heating with return current. Although this process predicts downflows in the lower transition region and upper chromosphere, its ultimate effect on the line profiles can be blue asymmetry: the upper layers moving away from us absorb the radiation of the red peak thus lowering its intensity in comparison to the blue one.  相似文献   

Magnetotellurisches feld in einem homogenen anisotropen medium     

Václav Petr 《Studia Geophysica et Geodaetica》1966,10(4):446-459

Резюме Рассматривается теория распространения плоских электромагнитнЫх волн в однородной анизотропной среде, где одна ось совпадает с направлением распространения электроманитной волны. БЫли вЫведенЫ вЫражения для главнЫх значений тензора проводимости и азимута одной главной составляющей тензора проводимости. Приводится также описание метода посредстввом которого приведеннЫе вЫше параметрЫ можно определить.

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Anschrift: Boční II, Praha 4-Spořilov.  相似文献   

The stratigraphic and paleoenvironmental setting of Aptian OAE black shale deposits in the Pieniny Klippen Belt, Slovak Western Carpathians     

Jozef Michalík  Jn Sotk  Otília Lintnerov  Eva Halsov  Marta B&#x;k  Petr Skupien  Daniela Boorov 《Cretaceous Research》2008,29(5-6):871

During the Jurassic and Cretaceous, the Pieniny Klippen Belt units of the Outer Western Carpathians were situated on the edge of the Paleoeuropean shelf rimming the northermost margin of the Mediterranean Tethys. During the late early Aptian humid event, Lower Cretaceous pelagic carbonate (Maiolica) sedimentation was interrupted by terrigenous input as a consequence of the first major mid-Cretaceous climate perturbations. The fluctuation of radiolarian abundance indicated an expansion of the oxygen-minimum zone due to upwelling conditions and salinity changes. Foraminifera, radiolarians, non-calcareous dinocysts, and calcareous nannofossils encountered in the West Carpathian Rochovica section enable a comparison of the black shales of the upper lower Aptian Koňhora Formation with the well-known Selli Event. Subsequent anoxia patterns (depositional, productive, and stagnant) have taken part in the depositional regime. Early Aptian climate perturbations both in the Outer Western Carpathians, Swiss Prealps (situated in a similar position on the distal southern edge of the former Paleoeuropean shelf) and/or in other parts of the world are traceable with sedimentological, biological, and chemical proxies.  相似文献   

Dynamics of the land use,land use change,and forestry sink in the European Union: the impacts of energy and climate targets for 2030     

Stefan Frank  Hannes Böttcher  Mykola Gusti  Petr Havlík  Ger Klaassen  Georg Kindermann  Michael Obersteiner 《Climatic change》2016,138(1-2):253-266

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Spatial variability and interdependence of rain event characteristics in the Czech Republic          下载免费PDF全文

Martin Hanel  Petr Máca 《水文研究》2014,28(6):2929-2944

Rain event characteristics are assessed in a 10‐year (1991–2000) record for 122 stations in the Czech Republic. Individual rain events are identified using the minimum interevent time (mit) concept. For each station, the optimal mit value is estimated by examining the distribution of interevent times. In addition, various mit values are considered to account for the effect of mit on rain event characteristics and their interrelationships. The interdependence between rain event characteristics and altitude, average rainfall depth, and geographic location are explored using simple linear models. Most rain event characteristics can be to some extent explained by average total rainfall or altitude, although models including the former significantly outperformed models using the latter. Significant correlation was found among several pairs of monthly mean characteristics often including event rain rate (with event duration, depth, maximum intensity, and fraction of intraevent rainless periods). Moreover, strong correlation was revealed between number of events, interevent time, event depth, and duration. In general, correlation decreases in absolute value with mit. Strong spatial correlation was found for the mean monthly interevent time and number of events. Spatial correlation was considerably smaller for other characteristics. In general, spatial dependence was smaller for larger mit values. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

The pace of Holocene vegetation change – testing for synchronous developments     

Thomas Giesecke  K.D. Bennett  H. John B. Birks  Anne E. Bjune  Elisaveta Bozilova  Angelica Feurdean  Walter Finsinger  Cynthia Froyd  Petr Pokorný  Manfred Rösch  Heikki Seppä  Spasimir Tonkov  Verushka Valsecchi  Steffen Wolters 《Quaternary Science Reviews》2011,30(19-20):2805-2814

Mid to high latitude forest ecosystems have undergone several major compositional changes during the Holocene. The temporal and spatial patterns of these vegetation changes hold potential information to their causes and triggers. Here we test the hypothesis that the timing of vegetation change was synchronous on a sub-continental scale, which implies a common trigger or a step-like change in climate parameters. Pollen diagrams from selected European regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed. The results show that the temporal pattern of vegetation change was significantly different from random. Times of change cluster around 8.2, 4.8, 3.7, and 1.2 ka, while times of higher than average stability were found around 2.1 and 5.1 ka. Compositional changes linked to the expansion of Corylus avellana and Alnus glutinosa centre around 10.6 and 9.5 ka, respectively. A climatic trigger initiating these changes may have occurred 0.5 to 1 ka earlier, respectively. The synchronous expansion of C. avellana and A. glutinosa exemplify that dispersal is not necessarily followed by population expansion. The partly synchronous, partly random expansion of A. glutinosa in adjacent European regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally.  相似文献   

Automatic Video System for Continues Monitoring of the Meteor Activity     

Pavel Koten  Karel Fliegel  Stanislav Vítek  Petr Páta 《Earth, Moon, and Planets》2011,108(1):69-76

In this paper we present current progress in development of new observational instruments for the double station video experiment. The Meteor Automatic Imager and Analyser (MAIA) system is based on digital monochrome camera JAI CM-040 and well proved image intensifier XX1332. Both the observations as well as the data processing will be fully automatic. We are expecting the recorded data of better quality and both spatial and time resolution in comparison with currently used analogue system. The main goal of the MAIA project is to monitor activity of the meteor showers and sporadic meteor each night for the period of at least 3 years. First version of the system was already assembled and has been intensively tested in the optical laboratory. Optical properties were measured and the result confirmed our expectations according to image quality and resolution. First night sky observation was already carried out.  相似文献   

New period study of the eclipsing binary V865 Cygni     

Petr Molík  Marek Wolf  Miloslav Zejda 《Astrophysics and Space Science》2007,310(1-2):149-152

Several new precise times of minima, based on CCD observations, have been secured for the relatively seldom studied eclipsing binary V865 Cyg (P=0^d.365 days). Its O–C diagram was analysed and new light elements are given. We showed that there is probably no parabolic period increase in V865 Cyg. Instead, a single abrupt period increase can be distinguished in the O–C diagram.  相似文献   

Consequences of climate change for the soil climate in Central Europe and the central plains of the United States   总被引：2，自引：0，他引：2  

Miroslav Trnka  Kurt Christian Kersebaum  Josef Eitzinger  Michael Hayes  Petr Hlavinka  Mark Svoboda  Martin Dubrovský  Daniela Semerádová  Brian Wardlow  Eduard Pokorný  Martin Možný  Don Wilhite  Zdeněk Žalud 《Climatic change》2013,120(1-2):405-418

This study aims to evaluate soil climate quantitatively under present and projected climatic conditions across Central Europe (12.1°–18.9° E and 46.8°–51.1° N) and the U.S. Central Plains (90°–104° W and 37°–49° N), with a special focus on soil temperature, hydric regime, drought risk and potential productivity (assessed as a period suitable for crop growth). The analysis was completed for the baselines (1961–1990 for Europe and 1985–2005 for the U.S.) and time horizons of 2025, 2050 and 2100 based on the outputs of three global circulation models using two levels of climate sensitivity. The results indicate that the soil climate (soil temperature and hydric soil regimes) will change dramatically in both regions, with significant consequences for soil genesis. However, the predicted changes of the pathways are very uncertain because of the range of future climate systems predicted by climate models. Nevertheless, our findings suggest that the risk of unfavourable dry years will increase, resulting in greater risk of soil erosion and lower productivity. The projected increase in the variability of dry and wet events combined with the uncertainty (particularly in the U.S.) poses a challenge for selecting the most appropriate adaptation strategies and for setting adequate policies. The results also suggest that the soil resources are likely be under increased pressure from changes in climate.  相似文献