排序方式： 共有17条查询结果，搜索用时 31 毫秒
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Joanna Staneva Emil V. Stanev Jörg-Olaf Wolff Thomas H. Badewien Rainer Reuter Burghard Flemming Alexander Bartholomä Karsten Bolding 《Continental Shelf Research》2009
This work deals with analysis of hydrographic observations and results of numerical simulations. The data base includes acoustic Doppler current profilers (ADCP) observations, continuous measurements on data stations and satellite data originating from the medium resolution imaging spectrometer (MERIS) onboard the European Space Agency (ESA) satellite ENVISAT with a spatial resolution of 300 m. Numerical simulations use nested models with horizontal resolutions ranging from 1 km in the German Bight to 200 m in the East Frisian Wadden Sea coupled with a suspended matter transport model. Modern satellite observations have now a comparable horizontal resolution with high-resolution numerical model of the entire area of the East Frisian Wadden Sea allowing to describe and validate new and so far unknown patterns of sediment distribution. The two data sets are consistent and reveal an oscillatory behaviour of sediment pools to the north of the back-barrier basins and clear propagation patterns of tidally driven suspended particulate matter outflow into the North Sea. The good agreement between observations and simulations is convincing evidence that the model simulates the basic dynamics and sediment transport processes, which motivates its further use in hindcasting, as well as in the initial steps towards forecasting circulation and sediment dynamics in the coastal zone. 相似文献
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C. Gregory Knight Heejun Chang Marieta P. Staneva Deyan Kostov 《The Professional geographer》2001,53(4):533-545
A GIS‐based distributed‐parameter runoff simulation model for the Struma River Basin in southwestern Bulgaria calculates the monthly snow/rain proportion, direct or surface runoff, snow cover and snowmelt, soil moisture, evapotranspiration, and total runoff. Simulation during the Bulgarian hydrologic year from November to October was compared with observed runoff data. The model closely replicates mean monthly runoff from climate conditions during the years 1961 –1990 as well as specific years. The simplified GIS model simulates hydrologic processes under limited data availability. 相似文献
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Bulgaria's indigenous water resources derive largely from mountain watersheds where orographic effects enhance precipitation. These watersheds provide resources upon which lowland communities, industry, and irrigation depend. On the basis of a comprehensive network of water management structures, Bulgaria has been able to harness a considerable proportion of internal water resources for human use, although the nation is, by European standards, dry. This paper explores the physical and human geography of Bulgarian water resources as a perspective from which the multiple dimensions of current Bulgarian water research and water issues can be seen. 相似文献
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This study assesses the regional impact of climate change on runoff in a mountainous region of southwestern Bulgaria. A GIS-based
distributed hydrologic model and two climate change scenarios – HadCM2 and CCC – were employed for years around 2025 and 2085.
Results from both scenarios demonstrate the basin's sensitivity of runoff to climate change, which produce significant spatial
and temporal changes in the basin's water yield with maximum runoff shift into early spring and further decreases in summer
runoff. There could be no reduction in mean annual runoff, except under the Hadley scenario by 2085. Changes in the magnitude
of mean monthly and peak flow are associated with early snowmelt and a reduction in snow cover in spring. Increases in spatial
variability of runoff reflect the basin's complex physiographic characteristics. The increase of spatial and temporal variability
in runoff points to different strategies for future water resource management.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Climate change presents both threats and opportunities to the nations and peoples of central and eastern Europe. National
and international programs are directly addressing climate change, and other programs speak to natural resource and environmental
quality issues that will have significant effects on vulnerability and adaptation to climate change. This paper explores examples
of ongoing climate change activity in the region, setting a broad context for the subsequent papers in this volume ofGeoJournal.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Alexander Barth Aida Alvera-Azcárate Jean-Marie Beckers Joanna Staneva Emil V. Stanev Johannes Schulz-Stellenfleth 《Ocean Dynamics》2011,61(5):599-610
Surface winds are crucial for accurately modeling the surface circulation in the coastal ocean. In the present work, high-frequency
radar surface currents are assimilated using an ensemble scheme which aims to obtain improved surface winds taking into account
European Centre for Medium-Range Weather Forecasts winds as a first guess and surface current measurements. The objective
of this study is to show that wind forcing can be improved using an approach similar to parameter estimation in ensemble data
assimilation. Like variational assimilation schemes, the method provides an improved wind field based on surface current measurements.
However, the technique does not require an adjoint, and it is thus easier to implement. In addition, it does not rely on a
linearization of the model dynamics. The method is validated directly by comparing the analyzed wind speed to independent
in situ measurements and indirectly by assessing the impact of the corrected winds on model sea surface temperature (SST)
relative to satellite SST. 相似文献
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Alexander Port Klaus-Werner Gurgel Joanna Staneva Johannes Schulz-Stellenfleth Emil V. Stanev 《Ocean Dynamics》2011,61(10):1567-1585
Tidal and wind-driven surface currents in the German Bight between shallow mudflats of the North Frisian islands and the island
of Helgoland are studied using coastal high-frequency radar (HFR) observations and hindcasts from a primitive equation numerical
model. The setup of the observational system is described, and estimates of expected measurement errors are given. A quantitative
comparison of numerical model results and observations is performed. The dominant tidal components are extracted from the
two data sources using tidal harmonic analysis and the corresponding tidal ellipses are defined. Results show that the spatial
patterns of different tidal ellipse parameters are consistent in the two data sets. Model sensitivity studies with constant
and variable salinity and temperature distributions are used to study density-related mechanisms of circulation. Furthermore,
the role of the surface wind field in driving the German Bight circulation is investigated using the complex correlation between
wind and surface current vectors. The observed change of the respective correlation patterns from the coastal to open ocean
is shown to be due to a combination of density effects, the coastline and topography. The overall conclusion is that HFR observations
resolve the small-scale and rapidly evolving characteristics of coastal currents well in the studied area and could present
an important component for regional operational oceanography when combined with numerical modelling. Some unresolved issues
associated with the complex circulation and large instability of circulation in front of the Elbe River Estuary justify further
considerations of this area using dedicated surveys and modelling efforts. 相似文献