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31.
E. Durisch-Kaiser A. Doberer J. Reutimann A. Pavel S. Balan S. Radan B. Wehrli 《Aquatic Sciences - Research Across Boundaries》2011,73(1):21-33
The transformation of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorous (SRP), and the release of dissolved
organic and particulate N and P, were analyzed in two lake complexes (Uzlina–Isac and Puiu–Rosu–Rosulet) of the Danube Delta
wetland during flood conditions in May and at low water level in September 2006. The Uzlina–Isac complex was hydrologically
tightly-connected with the Danube River and was flushed with river-borne nutrients and organic matter. These lakes acted as
effective transformers for nutrients and produced large amounts of fresh biomass, that promoted the excretion of dissolved
organic N and P during active growth. Biomass breakdown created particulate matter (<0.45 μm), which was widely liberated
during low flow in the fall. The Puiu–Rosu–Rosulet complex was characterized by a more distant position to the Danube and
proximity to the Black Sea, and received dominantly transformed organic compounds from the flow-through water and vast vegetation
cover. Due to reduced nutrient input, the internal production of organic biomass also was reduced in these more remote lakes.
Total N and P export from the lake nearest to the shelf was governed by dominantly dissolved organic and particulate compounds
(mean 58 and 82%, respectively). Overall, this survey found that these highly productive wetlands efficiently transform nutrients
into a large pool of dissolved organic and particulate N and P. Hence, wetland lakes may behave widely as net sources of organic
N and P to downstream waters and coastal marine systems. 相似文献
32.
Radan Květ 《GeoJournal》1991,24(4):417-420
Conclusion The proposal for a new complete classification of the Earth's evolution in accordance with periods of geotectonic cycles — depending on the external cosmic influence of the galactic year — has been elaborated as an additional application of a system model. Its basic idea is the principle of a hierarchical division and recurring cycles. For the time being, the significance of a periodical time table is a theoretical one. It allows a new view to be used when evaluating the last stages of the Earth's history during the Phanerozoic for which comparatively more geological information is available. However, a universal approach like the one described above can aid in directing further research on the older history of the Earth. Later on, theoretical knowledge could be applied to economic geology, above all if using a hierarchical classification of the phases of geotectonic cycles. 相似文献
33.
34.
Formation of homogeneous regions for regional frequency analysis of extreme precipitation events in the Czech Republic 总被引:1,自引:0,他引:1
Extreme high precipitation amounts are among environmental events with the most disastrous consequences for human society.
This paper deals with the identification of ‘homogeneous regions’ according to statistical characteristics of precipitation
extremes in the Czech Republic, i.e. the basic and most important step toward the regional frequency analysis. Precipitation
totals measured at 78 stations over 1961–2000 are used as an input dataset. Preliminary candidate regions are formed by the
cluster analysis of site characteristics, using the average-linkage clustering and Ward’s method. Several statistical tests
for regional homogeneity are utilized, based on the 10-yr event and the variation of L-moment statistics. In compliance with
results of the tests, the area of the Czech Republic has been divided into four homogeneous regions. The findings are supported
by simulation experiments proposed to evaluate stability of the test results. Since the regions formed reflect also climatological
differences in precipitation regimes and synoptic patterns causing high precipitation amounts, their future application may
not be limited to the frequency analysis of extremes. 相似文献
35.
Time variations of the relationships between the North Atlantic Oscillation and European winter temperature and precipitation 总被引:1,自引:0,他引:1
The degree of stationarity of relationships between the NAO index and long European temperature and precipitation series in
winter is quantified by running correlations with a time window of 31 years at 29 and 27 stations in Europe, respectively.
They indicate major nonstationarities in the NAO-to-surface climate relationships at most stations. The temporal course most
common for correlations with temperature is a slight change prior to about 1950, followed by an increase; for precipitation,
a typical course is a decrease in the first half of the 20th century, followed by an increase. The temporal variations in correlations do not result from the presence of trends in the
time series. The periods of high correlations with temperature are accompanied with an eastward shift of both NAO action centres;
the eastward shift is thus at least partly responsible for the time variations in correlations.
huth@ufa.cas.cz 相似文献
36.
37.
Radan Květ 《GeoJournal》1991,25(4):367-370
Conclusion The gas eruption in Lake Nyos allows solely a deep inorganic origin of the CO2, and CO2 ascent along intersecting ruptures to be considered. Enormous gas volumes can be liberated from ascension paths with voids
in the deep sections of the Earth's crust rather than from the water-dissolved phase (a lake) on the Earth's surface. In this
case, rupture activity rather than volcanic activity should be involved. Similarly to volcanic activity, other events are
also associated with open ruptures in the Earth's crust. No interrelations exist between the single phenomena. One of them
consists in the ascent of CO2 with no relation to magma. Earthquakes, too, are associated with ruptures. Even a very slight tremor of the Earth's crust
can contribute to the liberation of deepseated compressed CO2. However, disturbing the equilibrium of the water-column pressure and the compressed gas can result in an eruption even with
no external impetus, e. g. an earthquake. 相似文献
38.
Radan Květ 《GeoJournal》1995,37(4):413-417
39.
Radan Květ 《GeoJournal》1990,22(4):387-390
Conclusion The suggested application of hierarchical systems to geology and geography offers a new view on the evolution of the Earth and a new classification of geosciences. The application of these systems allows the individual fields of geosciences to be connected with each other and also with other disciplines (e.g. physics, astronomy, biology). Hierarchical systems including periodicity can aid future advances in natural sciences because they can be regarded as a uniting principle and key to new approaches to research in natural sciences. 相似文献
40.
Constructing Site-Specific Climate Change Scenarios on a Monthly Scale Using Statistical Downscaling 总被引:1,自引:1,他引:0
Summary Monthly mean temperature and monthly precipitation totals in two small catchments in the Czech Republic are estimated from
large-scale 500 hPa height and 1000/500 hPa thickness fields using statistical downscaling. The method used is multiple linear
regression. Whereas precipitation can be determined from large-scale fields with some confidence in only a few months of the
year, temperature can be determined successfully. Principal components calculated separately from the height and thickness
anomalies are identified as the best predictor set. The method is most accurate if the regression is performed using seasons
based on three months. The test on an independent sample, consisting of warm seasons, confirms that the method successfully
reproduces the difference in mean temperature between two climatic states, which indicates that this downscaling method is
applicable for constructing scenarios of a future climate change. The ECHAM3 GCM is used for scenario construction. The GCM
is shown to simulate surface temperature and precipitation with low accuracy, whereas the large-scale atmospheric fields are
reproduced well; this justifies the downscaling approach. The observed regression equations are applied to 2xCO2 GCM output so that the model’s bias is eleminated. This procedure is then discussed and finally, temperature scenarios for
the 2xCO2 climate are constructed for the two catchments.
Received December 3, 1998 Revised December 4, 1999 相似文献