Reconstructing the spatial distribution of large vegetation formations during the mid-Holocene in Romania: a predictive modeling approach     

Cristian Valeriu Patriche  Radu Gabriel Pîrnău  Bogdan Roşca 《第四纪科学杂志》2020,35(8):1081-1088

The present study tests the usefulness of SoLIM software and GIS techniques for the reconstruction of large vegetation formations from the mid-Holocene period in Romania. We used current reference climate data (temperature, precipitation) and the current extent of ecological regions in Romania to derive climate optimality functions for each vegetation formation. The optimality functions were used to simulate current and past distributions of vegetation. The results showed that the current and mid-Holocene simulated spatial distributions of vegetation are quite similar. Changes were found for about 14% of the Romanian territory (33 946 km²), the most important being the retreat of coniferous forests in favor of mixed forests and of mixed forests in favor of forest steppe. The former is validated by previous pollen-based studies showing the transition from coniferous forests to mixed forests that occurred in several areas of the country after the mid-Holocene. The study demonstrates the potential of this methodological approach to reconstruct past vegetation formations, and at the same time that it is a straightforward and expert knowledge-based method. Although our application uses only climate factors, the results can be further refined by incorporating additional drivers (soil and landform information, site-specific pollen and fossil data, wildfire data) for a more accurate inference of paleovegetation.  相似文献   

Toward very high horizontal resolution NWP over the alps: Influence of increasing model resolution on the flow pattern   总被引：1，自引：0，他引：1  

Michał Z. Ziemiański  Marcin J. Kurowski  Zbigniew P. Piotrowski  Bogdan Rosa  Oliver Fuhrer 《Acta Geophysica》2011,59(6):1205-1235

The increasing resolution of contemporary regional numerical weather prediction (NWP) models, reaching horizontal grid sizes of O(1 km), requires robust and reliable dynamical cores, working well beyond the approximation of quasi-horizontal flows. That stimulates an interest in an application for NWP purposes of dynamical cores based on the anelastic, or — more generally — sound-proof flow equations, and characterized by appropriate robustness and reliability. The paper presents results from testing the dynamical core of EULAG, the anelastic research model for multi-scale flows, as a prospective NWP dynamical core. The model simulates the semi-realistic frictionless and adiabatic flow over realistic steep Alpine topographies, employing horizontal grid sizes of 2.2, 1.1, and 0.55 km. The paper demonstrates not only the numerical robustness of EULAG, but also studies the influence of the varying horizontal resolution on the simulated flow. Results show that the increased horizontal resolution increases orographic drag on the flow. While the general flow pattern remains the same, increased resolution influences the flow on scales from hundreds of kilometers to meso-gamma scales. The differences are especially apparent in the near-surface layer of 1.5 to 3 km deep, and in the distribution and amplitudes of the orographically-induced gravity waves.  相似文献   

Testing the anelastic nonhydrostatic model EULAG as a prospective dynamical core of a numerical weather prediction model Part I: Dry benchmarks     

Bogdan Rosa  Marcin J. Kurowski  Michał Z. Ziemiański 《Acta Geophysica》2011,59(6):1236-1266

In this paper, a feasibility of anelastic approach for numerical weather prediction (NWP) is examined. The study concerns the anelastic nonhydrostatic model EULAG as a prospective candidate for the new dynamical core of a high-resolution NWP model. Such an application requires a series of benchmark tests to be performed. The study presents the results of dry idealized two-dimensional linear and non-linear tests. They include evolution of cold and warm density currents in neutrally stratified atmosphere, inertia-gravity waves in short and long channels, as well as mountain gravity waves for a set of different flow regimes. Detailed comparison of the results with the reference solutions, based mainly on the results of compressible models, indicates a high level of conformity for all of the experiments. It verifies the anelastic approach as strongly consistent with the compressible one for a broad class of atmospheric problems. It also corroborates the robustness of EULAG numerics, an essential requirement of dynamical core of NWP model.  相似文献   

Guano-derived δ13C-based paleo-hydroclimate record from Gaura cu Musca Cave,SW Romania   总被引：1，自引：0，他引：1  

Bogdan P. Onac  Ferenc L. Forray  Jonathan G. Wynn  Alexandra M. Giurgiu 《Environmental Earth Sciences》2014,71(9):4061-4069

The δ¹³C values of 23 unevenly spaced guano samples from a 17-cm long clay sediment profile in Gaura cu Musc? Cave (GM), in SW Romania, made it possible to preliminarily characterize the Medieval Warm Period summer hydroclimate regime. The beginning of the sequence (AD 990) was rather wet for more than a century, before becoming progressively drier. After a brief, yet distinct wet period around AD 1170, drier conditions, with a possible shift from C₃ to a mixed C₃-dominated/C₄ type vegetation (2 ‰ lower δ¹³C values), prevailed for almost half a century before the climate became colder and wetter at the onset of the Little Ice Age, when bats left the cave. The guano-inferred wet and dry intervals from the GM Cave are mirrored by changes in the color and amount of clay accumulated in the cave. They also agree well with reconstructions based on pollen and charcoal from peat bogs and δ¹³C and δ¹⁸O on speleothems from other Romanian sites. Overall, these results indicate that the δ¹³C of bat guano can provide a sensitive record of the short-term coupling between local/regional climate and the plant–insect–bat–guano system.  相似文献   

Erratum to: Guano-derived δ13C-based paleo-hydroclimate record from Gaura cu Musca Cave,SW Romania     

Bogdan P. Onac  Ferenc L. Forray  Jonathan G. Wynn  Alexandra M. Giurgiu 《Environmental Earth Sciences》2014,71(9):4071-4071

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Tracking UVCS/SOHO Responsivity with Observations of <Emphasis Type="Italic">ζ</Emphasis> Tau     

Bogdan Valcu  Peter L. Smith  Larry D. Gardner  John C. Raymond  Mari-Paz Miralles  John L. Kohl 《Solar physics》2007,243(1):93-104

We have tracked the spectral responsivity of the ultraviolet channels of the UVCS (Ultraviolet Coronagraph Spectrometer) instrument on SOHO by repeated observations of a stable hot star. We demonstrate first that the ultraviolet spectral irradiance of the Be star ζ Tau (HD 37202) for the 100- to 125-nm wavelength range has been sufficiently constant for our purposes when measured periodically over the course of the SOHO mission. We then use ζ Tau as a radiometric transfer standard to determine an average decrease beginning in November of 1998 of 13.0% per year in the responsivity of the UVCS O vi channel for wavelengths near H i Ly α and for a particular UVCS unvignetted aperture used for science observations. The calibration tracking method involves separating two ζ Tau spectral regions that are overlapped on part of the detector. The change in the responsivity of UVCS/SOHO began in late 1998 as determined by comparison of simultaneous observations of the corona carried out with UVCS/SOHO and the freshly-calibrated UVCS instrument on the Spartan 201 satellite in early November of 1998. B. Valcu now at BrainLAB, Inc, 3 Westbrook Corporate Ctr., Tower 3, Suite 400, Westchester, IL 60154, USA, e-mail: bogdan.valcu@brainlab.com or Bogdan_valcu@hotmail.com  相似文献   

Poisson Recoding Of Solar Images For Enhanced Compression     

Bogdan Nicula  David Berghmans  Jean-François Hochedez 《Solar physics》2005,228(1-2):253-264

The amount of useful scientific data that a space-borne telescope produces is often limited by the available telemetry of the platform. General purpose image compression schemes are usually used to compress the image either lossy or losslessly. These schemes do not take into account the fact that pixel values of typical solar images are only known to within a certain uncertainty range. We present a preprocessing method to enhance the performance (compression ratio) of any subsequent image compression scheme. The method uses estimates of the photon shot and thermal noises to compute a recoding look-up table that maps the initial data into uncertainty intervals. The recoding method is lossy in a mathematical sense but lossless in a physical sense, since the image alterations are guaranteed to be smaller than the Poisson noise. The performance of any further compression algorithm is enhanced while achieving a known guaranteed maximum absolute error for each pixel in the case of lossless compression. This revised version was published online in October 2005 with corrections to one of the authors' names.  相似文献   

Geohazards assessment and mapping of some Balkan countries   总被引：1，自引：0，他引：1  

Betim Mu?o  Georgi Alexiev  Shyqyri Aliaj  Zenun Elezi  Bogdan Grecu  Neculai Mandrescu  Zoran Milutinovic  Mircea Radulian  Boyko Ranguelov  Defrim Shkupi 《Natural Hazards》2012,64(2):943-981

The assessment of geological hazard is a topic with significant interest for the Balkans. During the last decade of twentieth century, most of the countries in the region have embarked on the road of a hasty transitory period from totalitarian regimes to democracy. Development of free market economy has given rise to uncontrolled movement of people, fast construction of housing and facilities and unproportioned accumulation of population around and in big cities. Besides Greece, an old member of European Union, and two newcomers in the organization, Romania and Bulgaria, the other countries are all hoping to enter the Union as faster as they can. Many different candidate or full-fledged member country programs of European Community offer a lot of joint and cross-border projects for constructing road infrastructure and facilities. As development accelerates in the Balkans and given the intensive geohazard elements that this territory exhibits, it becomes increasingly important to understand, study, and map these elements for being aware of the damage to the total environment these hazards might cause. The geohazard map and assessment of some Balkan countries has been carried out through two scientific meetings in Ohrid, Macedonia, and Tirana, Albania during 2007. The map is compiled in the Albanian Geological Survey, Tirana, Albania in the scale 1:1,000,000. As a base map, we used the topographic map produced by VGI, formerly Yugoslavia mapping authorities. As a seismic layer in our map, we used the values of peak ground acceleration obtained from Global Seismic Hazard Assessment Program. Two catalogs were constructed: The first one that contains the crustal earthquakes (hypocentral depth within first 70?km) and the second one that contains intermediate earthquakes (hypocentral depth below 70?km). This work is largely based on previous studies and investigations by earth scientists and specialists of each country comprised in this territory. In this respect, the map we constructed should be considered as a preliminary composite geohazard map with the possibility to be enriched and added with other new elements and data in the future.  相似文献   

Toponymy and the Communist city: Street names in Bucharest, 1948–;1965     

Duncan Light  Ion Nicolae  Bogdan Suditu 《GeoJournal》2002,56(2):135-144

Past studies of the Socialist/Communist city have paid only limited attention to the ways in which Communist regimes mobilised a wide variety of symbols in the urban landscape in order to legitimate and institutionalise the ideology of revolutionary socialism. This paper considers the role of street names in this process with particular reference to Bucharest, Romania during the 1948–1965 period. When the Communist regime came to power it embarked on widespread renaming of streets as one means of both `decommemorating' the pre-socialist regime and proclaiming the agenda and ideology of the Communist state. The new street names commemorated a variety of events and personalities from the history of Romanian and Soviet Communism. The impact of street names was amplified further through practices such as multiple namings and the spatial clustering of street names of high ideological resonances. The paper argues that Bucharest's street names can be `read' as a mirror of ideological change, changing constructions of national identity, and Romania's macro-political orientation (especially its changing relations with the Soviet Union).  相似文献   

Groundwater study of a volcanic area near Bandung,Java, Indonesia     

Bogdan Pulawski  Hans Øbro 《Journal of Hydrology》1976,28(1):53-72

A hydrogeological investigation of the Bandung area, Java, Indonesia, is described. The investigation was carried out as part of a feasibility study directed towards improvement and development of the city's water supply.The area is situated in a tropic mountainous region, dominated by pyroclastic volcanic deposits and with abundant rainfall. The main activities of the investigation were compilation and evaluation of existing climatological and hydrogeological data, testing of four existing wells, a geo-electrical survey, drilling and testing of a new test well, study of water quality by analysis of samples from both springs and wells, and measurements of spring yields.The results of the investigation indicated presence of large groundwater resources within a distance of 15–20 km from the city. The feasibility study recommended that Bandung's water supply be based on these groundwater resources and this recommendation is being implemented.During the investigation some results concerning rainfall, infiltration, aquifers, geoelectrical surveying, and groundwater quality were obtained, which may be of general interest for hydrologists and geologists working in tropical volcanic and mountainous regions. These results are summarized in the conclusion of this paper.  相似文献