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Zbynek Sokol 《Studia Geophysica et Geodaetica》1995,39(1):74-83
Summary A series of Helmholtz equations has to be solved in short-range weather forecast models which use a splitting scheme of integration. For these purposes the successive overrelaxation, the Gauss-Seidel relaxation, the conjugate gradient method, the steepest descent method, the full-multigrid method and the direct method based on the minimum degree algorithm were used and their efficiencies were compared. It was found that the full-multigrid method was the most efficient among the iterative methods in terms of computational time, and that the effect rapidly increased with the grid size. The direct method may be an appropriate approach if the solution is repeated for various right-hand sides, but it requires large auxiliary computer memory. The selection of the optimum method depends on the concrete problem being solved and on the computer memory available. 相似文献
3.
Local flash flood storms with a rapid hydrological response are a real challenge for quantitative precipitation forecasting (QPF). It is relevant to assess space domains, to which the QPF approaches are applicable. In this paper an attempt is made to evaluate the forecasting capability of a high-resolution numerical weather prediction (NWP) model by means of area-related QPF verification. The results presented concern two local convective events, which occurred in the Czech Republic (CR) on 13 and 15 July 2002 and caused local flash floods. We used the LM COSMO model (Lokall Model of the COSMO consortium) adapted to the horizontal resolution of 2.8 km over a model domain covering the CR. The 18 h forecast of convective precipitation was verified by using radar rainfall totals adjusted to the measured rain gauge data. The grid point-related root mean square error (RMSE) value was calculated over a square around the grid point under the assumption that rainfall values were randomly distributed within the square. The forecast accuracy was characterized by the mean RMSE over the whole verification domain. We attempt to show a dependence of both the RMSE field and the mean RMSE on the square size. The importance of a suitable merger between the radar and rain gauge datasets is demonstrated by a comparison between the verification results obtained with and without the gauge adjustment. The application of verification procedure demonstrates uncertainties in the precipitation forecasts. The model was integrated with initial conditions shifted by 0.5° distances. The four verifications, corresponding to the shifts in the four directions, show differences in the resulting QPF, which depend on the size of verification area and on the direction of the shift. 相似文献
4.
Z. Vencelides Z. Hrkal H. Nováková H. Prchalová 《Journal of Atmospheric Chemistry》2011,68(2):127-138
In harmony with requirements of Water Framework Directive the natural backgrounds of selected metals were established on the
territory of Czech Republic. This paper is intended to provide characteristics and results of testing methods focused on quantification
of the impacts of anthropogenic activities based on data of regional monitoring and their separation from acid atmospheric
deposition including an appropriate discussion regarding the natural backgrounds of relevant metals. The results indicate
that even in regions extremely affected by acid atmospheric deposition as is the territory of the Czech Republic this acid
deposition will not have direct impact on the quality of ground waters on a regional scale. Consequently, the proved changes
in quality of ground waters seem to have been caused by secondary processes, specifically by mobilization of metals in a rock
environment due to increased acidity. 相似文献
5.
The hydro-meteorological evaluation of a flood event in July 1997 (the Odra flood in Central Europe) demonstrated that new procedures to estimate design floods for the reservoir outflow structures in the Czech Republic (CR) were needed. Therefore, the techniques of the estimation of Probable Maximum Precipitation (PMP) were developed in a national research project (1998–2000), and the activity focused on the improvement of the area related PMP estimates was going on within a present national project. In the frame of the evaluation of the next extreme precipitation event in August 2002 (the Labe flood in the CR and Germany), we compared the catchments related precipitation with the PMP estimates. In this paper, an outline of the PMP estimation techniques is given and the use of data from the Czech gauges is described, the aim being the statistical derivation of the point and area PMP estimates for precipitation duration of 1 to 5 days. The use of radar data in assessing the maximized area reduction factor is discussed and the relationship resulting from the radar measurements over the CR territory is presented. An evaluation of the radar-based area rainfall enabled us to transform the point PMP to the area PMP estimate designed for the river basins in CR. In the last part of the paper, the results obtained by comparing the rainfalls in 1997 and 2002 flood events with the PMP estimates are presented. The comparison showed that the maximum area rainfalls over small Czech catchments (the 3rd order river basins) did not exceed 63% of the corresponding PMP values. 相似文献
6.
Hana Jir��kov�� Fr��d��ric Huneau H��l��ne Celle-Jeanton Zbynek Hrkal Philippe Le Coustumer 《Hydrogeology Journal》2011,19(8):1545-1562
Climatic instability during the late Pleistocene has been reflected in the pattern of groundwater recharge. This report summarizes palaeoclimate knowledge during the late Weichselian in Europe. During this period the majority of northern Europe was covered by thick ice sheets and permafrost, preventing aquifers from recharging. In contrast, southern Europe was generally free of these palaeoclimatic features. Palaeoclimatic information has been combined with isotope data to better understand the palaeorecharge conditions and recharge timing across the European continent. The 18O and 2H relationship shows latitudinal plus climatic influences. Radiocarbon data show that while southern European aquifers have generally been recharged continuously during the last 40,000 years, northern European aquifers typically show a recharge gap during the Last Glacial Maximum. Areas that underwent continuous recharge during the entire late Pleistocene period can also be distinguished from areas where recharge to aquifers was prevented during the Last Glacial Maximum. Finally, several examples are presented of melt-water recharge or subglacial recharge. The identification of such diversity in the groundwater palaeorecharge in Europe is of great importance for modellers developing management schemes for groundwater resources. 相似文献
7.
Groundwater resources use and management in the Amu Darya River Basin (Central Asia) 总被引：2，自引：0，他引：2
Shavkat Rakhmatullaev Frédéric Huneau Jusipbek Kazbekov Philippe Le Coustumer Jamoljon Jumanov Bouchra El Oifi Mikael Motelica-Heino Zbynek Hrkal 《Environmental Earth Sciences》2010,59(6):1183-1193
This paper analyses groundwater resources use and management in the socio-economic context of the Amu Darya River Basin which
covers a part of the following landlocked Central Asian countries: Afghanistan, Tajikistan, Turkmenistan and Uzbekistan. These
agrarian nations for sustaining their vital agricultural productions started to use groundwater during the recent drought
years (1998–2001) because of its relatively good quality and quantity and as an alternative to highly mineralized surface
waters. Present extent of groundwater resources use is discussed with consideration to their reserves, quality, and institutional
management and transboundary aspects within the basin. After the collapse of the centralized water resources management system
and infrastructure of the former Soviet Union, new underdeveloped systems are being practiced over the whole Amu Darya River
Basin. The critical situation of groundwater management in Afghanistan is also discussed. This work attempts to document the
management and use of groundwater in the Amu Darya Basin and present time management realities, with fragmented and weak national
and regional regulation on groundwater. Special attention is given to groundwater resources in irrigated agriculture, which
increased use in all countries of the basin is due to quick access to underground resources and relatively good quality and
quantity. 相似文献
8.
9.
Zbynek Hrkal 《Hydrogeology Journal》2001,9(4):348-357
The area of the Jizerské Mountains in the northern part of the Czech Republic is known to have suffered from heavy acid atmospheric
deposition which has led to mass extinction of the forest cover in apical parts of the mountains and to degradation of groundwater
quality. A methodology for construction of groundwater vulnerability maps, using a Geographical Information System (GIS),
has been developed as a tool for protecting the groundwater resources.
The maps were constructed by using four subsidiary layers, each of which reflects a particular parameter that governs acidification.
The factors that determine vulnerability are: (1) elevation above sea level, (2) morphology of the terrain, (3) areal extent
and type of vegetation cover, and (4) lithology of the aquifer. A step-wise analysis and application of the data in each of
the layers was accomplished to compare changes in the quality of groundwaters, and to obtain the best weighting factors for
the individual parameters. Changes in alkalinity of the groundwater during the last 30 years were used as a test criterion.
The vulnerability map should be a valuable tool to identify and outline areas most vulnerable to acidification and also areas
considered for reforestation.
Electronic Publication 相似文献
10.
Knowledge of the natural background content of metals is important, but can be difficult to establish because the concentrations of substances dissolved in ground waters vary considerably with time and space. The main objective of the paper is to assess the natural background of five selected elements: As, Al, Cd, Pb and Hg. Each of these elements, with the exception of Al, is included in the Minimum list of pollutants and their indicators for which the EU Member States should establish threshold values (Daughter Groundwater Directive). The data of the Czech Hydrometeorological Institute which contains analyses obtained by regular monitoring of the quality of ground waters at intervals of 6 months has been used as the source information. This system incorporates ca. 450 monitoring sites which provide information about water in all the types of rocks penetrated by individual boreholes. Because of the low concentrations of certain elements (Hg, Pb and Cd in particular) a significant number of analytical results lie below the quantification limit of the analytical methods used. Therefore, conventional statistical methods for processing data were not applicable and alternative procedures were used. The Kaplan–Meier procedure was used within the NADA module for statistical analysis of data sets containing values below the quantification limit. The concentrations of monitored elements that can be considered natural background are suggested to be values of the third quartile, i.e. values that are less than or equal to 75% of analytical results in the assessed dataset. The remaining 25% of analytical results that exceed the proposed limit can be considered to be anomalies which may be natural or anthropogenic. Based on the statistical analysis of data specific values for the natural background content of elements in ground waters within particular types of lithology have been proposed. These can be considered the natural background values that apply within the whole of the territory of the Czech Republic. 相似文献