排序方式： 共有95条查询结果，搜索用时 484 毫秒
51.
Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project 总被引：1，自引：1，他引：0
Zbigniew W. Kundzewicz Markus Stoffel Ryszard J. Kaczka Bartłomiej Wyżga Tadeusz Niedźwiedź Iwona Pińskwar Virginia Ruiz-Villanueva Ewa Łupikasza Barbara Czajka Juan Antonio Ballesteros-Canovas Łukasz Małarzewski Adam Choryński Karolina Janecka Paweł Mikuś 《Acta Geophysica》2014,62(3):620-641
The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness. 相似文献
52.
Robert J. Bialik Mikołaj Karpiński Agnieszka Rajwa Bartłomiej Luks Paweł M. Rowiński 《Acta Geophysica》2014,62(6):1413-1434
This paper presents results of a field investigation conducted to examine the bed sediment, riverbed morphology and flow structure over dunes in natural and regulated channels. Field measurements using an acoustic Doppler current profiler (ADCP) have been carried out on two parts of lowland Wilga River in Poland. It is shown that the bedforms with a low angle of lee side develop more frequently than asymmetrical dunes with high lee-side angles, which are mostly associated with the occurrence of local scours and river meanders. Wavenumber analysis of bed elevation confirms the existence of scaling region in the longitudinal wavenumber spectrum, with “?3” scaling exponents for the natural and regulated channels as well. Moreover, the results of flow velocity field are presented in the form of a 2-D streamwise-vertical vector field, showing several similarities to previous laboratory and field investigations conducted on much deeper rivers than the Wilga. The experimental campaign and methods used to obtain the results are also presented briefly. In addition, a short database of fluvial dunes statistics is provided. 相似文献
53.
Multiscale interaction between monsoonal circulation and the local topography causes the southern front of the Darjeeling–Bhutan Himalaya to receive one of the highest annual rainfalls (3000–6000 mm) and most frequent heavy rains (up to 800 mm day?1) along the whole southern Himalayan margin. An examination of the patterns of annual rainfall, rainfall concentration, overland flow generation and slope instability indices in the Darjeeling–Bhutan Himalaya for 1986–2015 indicates that the mountain front disturbs rainfall gradient between the Bay of Bengal and the Tibetan Plateau. The results show that the precipitation concentration indices are lowest at the Himalayan front where the annual rainfall and the number of rainy days are highest. The Himalayan front has the highest predisposition to produce overland flow compared to adjacent foreland and the mountain interior. The average probability of the rainfall initialising the shallow landslides increases from 0.6% for a 1-day rainfall threshold of 144 mm to 6.1% for a 4-day rainfall threshold of 193 mm in the study area. The highest probability (up to 10%) of 2-day and longer low-intensity storms at the mountain front indicate that its area is threatened with particularly larger and deeper landslides. The multivariate regression analysis reveals statistically significant linear relationships of rainfall hazard indices with elevation and the distance to the mountain front in the mountain foreland and Himalaya, respectively. Regionally, the Darjeeling Himalaya reveals lower values of rainfall hazard indices, in comparison to the Bhutan Himalaya. 相似文献
54.
—?The empirical Green's function deconvolution technique is used to retrieve the source time functions from the records of P waves of seven seismic events that occurred at the Rudna copper mine in 1996 and were located in the middle of the underground network. Their moment magnitudes ranged from 2.1 to 2.9. The records of smaller events from the same area and with similar source mechanism, with moment magnitudes ranging from 1.5 to 2.0, were accepted as empirical Green's functions. The relative source time functions were successfully retrieved at a number of stations for six events. Directivity effects, implying unilateral rupture propagation, were observed in five cases. The azimuth of rupture propagation direction and the rupture velocity were estimated from the distribution of pulse widths and pulse maximum amplitudes as a function of the cosine of station azimuths. The rupture propagated approximately either from south to north or from north to south. The rupture velocity was low, ranging from 0.25 to 0.54 of the shear-wave velocity. The source dimensions, represented by the fault length, were also small in comparison with those estimated in the frequency domain and ranged from 80 to 250?m. 相似文献
55.
The paper presents the method of local magnitude determination used at Polish seismic stations to report events originating
in one of the four regions of induced seismicity in Poland or its immediate vicinity. The method is based on recalculation
of the seismic moment into magnitude, whereas the seismic moment is obtained from spectral analysis. The method has been introduced
at Polish seismic stations in the late 1990s but as of yet had not been described in full because magnitude discrepancies
have been found between the results of the individual stations. The authors have performed statistics of these differences,
provide their explanation and calculate station corrections for each station and each event source region. The limitations
of the method are also discussed. The method is found to be a good and reliable method of local magnitude determination provided
the limitations are observed and station correction applied. 相似文献
56.
Heavy metals in sediments as evidence for recent pollution and quasi-estuarine processes: an example from Lake Druzno,Poland 总被引：1，自引：0，他引：1
Wojciech Tylmann Roman Gołębiewski Piotr Paweł Woźniak Karolina Czarnecka 《Environmental Geology》2007,53(1):35-46
This article presents the results of a geochemical investigation of sediments from Lake Druzno (northern Poland), a reservoir
fed by freshwater from the catchment, with periodic input of brackish water from Vistula Lagoon. This study analyzed the spatial
variation in heavy metal content in surface sediments as well as the temporal changes in metal content in two sediment cores
dated using the 210Pb method. In the surface sediments, the highest metal concentrations were recorded in the northern part of the lake, with
lower concentrations in the central and southern parts. Absolute values of metal concentrations in the cores were low, but
normalization with respect to Al showed an increase during the second half of the 20th century. Mean enrichment factors (EF)
in sediments from the second half of the 20th century ranged from insignificant (1–1.2) for Fe to (1.55–3.3) for Cu, Cd, Pb
and Zn. The sediments deposited before 1950 had lower EF values (>1.5) and had low variability. Results from both the surface
sediments and the cores indicate that the main source of lake pollution is brackish water intrusion from the Vistula Lagoon
via the contaminated River Elbląg. 相似文献
57.
Chandra Kant Pawe 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2018,118(1):88-100
Unplanned urban growth, particularly in developing countries has led to changes in land use/land cover (LULC). Numerous Indian cities face problems of unplanned LULC change due to nominal or non-existent planning efforts compounded by rapid urban population growth. The Guwahati Metropolitan Area (GMA) is one such urban centre. The present study assesses the trajectories of LULC change using Landsat imageries acquired in 1976, 1989, 2002 and 2015. Natural and semi natural vegetated area and artificial and natural water bodies decreased while built-up areas, cultivated and managed areas, and natural and semi natural non-vegetated areas increased. The built-up area increased from 23.9 in 1976 to 115.1 km2 in 2015 becoming the dominant land cover class accounting for 41.8% of the total geographical area. During this period, natural and semi natural vegetated land were reduced by 88.9 km2 at an annual rate of 2.2 km2. Over the years there was an increasing trend of built-up land and cultivated and managed areas in the peripheral areas of the city while natural and semi natural vegetated land diminished. Consequently, as in many other developing countries, there is an urgent need for the governmental authorities and other stakeholders to implement effective urban planning policies. 相似文献
58.
Earthquake of November 30, 2004, in Podhale region, southern Poland, was of unexpectedly big size in this area of weak seismicity.
As Poland is considered a country of low seismicity, the earthquake has caused concern about seismic hazard in Poland, especially
since it took place shortly after the even more unexpected Kaliningrad Region, Russia, earthquakes of September 21, 2004,
that inflicted minor damage in northern Poland. The paper presents the findings on the Podhale earthquake which reached macroseismic
intensity up to 7 and magnitude 4.7 (m
b
; ISC). The event was felt up to a distance of about 100 km and inflicted slight damage to buildings in its narrow epicentral
area, thus evidencing its relatively shallow depth. The quake has been located near the village of Skrzypne, about 15 km west-southwest
of the district capital Nowy Targ. The source mechanism has been found to be of dip slip normal fault type, although a problem
remains of association of this mechanism with known tectonic dislocations in the region. The earthquake has been followed
by a long series of aftershocks. Their distribution in time is also studied and the biggest aftershocks have been located. 相似文献
59.
In this paper, optical measurements of aerosol properties made during a ship cruise from Poland to Antarctic Station in September and October 2006, and during the cruise back to Gdynia in April and May 2007 are described. A large gradient of pollution between the clear South Atlantic and the dusty North Atlantic was observed. The maximum of aerosol optical thickness at a wavelength of 500 nm reached 0.4 at 20°N in September 2006 and 0.3 at 40°N in May 2007, respectively. Strong Saharan dust transport is suggested as an explanation for the small values of Ångström exponent observed (values of 0.2 and 0.4 on these respective dates). On the Southern Hemisphere the aerosol optical thickness at 500 nm ranged from 0.05 to 0.2. Significant increases of the aerosol optical thickness were associated with strong wind and sea salt production. Good agreement was found when the in situ measurements of aerosol optical thickness were compared to satellite retrievals and modelling results. 相似文献
60.
Rafał Iwański Anna Odzimek Lasse B.N. Clausen Vijay Kanawade Ingrid Cnossen Niklas J.T. Edberg 《Acta Geophysica》2009,57(3):760-777
The first red sprite events scientifically observed from Poland on 20/21 July 2007, during the two-week SPARTAN Sprite-Watch
2007 campaign, are analysed in the context of the meteorological conditions over Poland and the Czech Republic at that time.
The phenomena were detected and recorded from the IMWM High-Mountain Meteorological Observatory at Mount Śnieżka using a low-light
television CCD camera. Meteorological conditions over the south-west Poland were monitored on the basis of information from
the Polish and Czech meteorological radar and lightning detection systems and also from satellite infra-red difference images,
indicating the development of thunderstorm clouds over central Europe. Four sprite events detected in the night-time of 20/21
July indicate that in this region sprites are produced by massive storm cells built on warm fronts which are supplied by warm
and humid tropical air masses during local summer thunderstorm season. 相似文献