排序方式： 共有17条查询结果，搜索用时 15 毫秒
11.
Tidal wave transformations in the German Bight 总被引：2，自引：2，他引：0
Emil V. Stanev Rahma Al-Nadhairi Joanna Staneva Johannes Schulz-Stellenfleth Arnoldo Valle-Levinson 《Ocean Dynamics》2014,64(7):951-968
Mesoscale and submesoscale dynamics associated with tidal wave transformations were addressed in the German Bight using numerical simulations. Tidal gauge and velocity observations in several locations were used to validate the numerical model. A downscaling approach included analysis of simulations with horizontal resolutions of 1, 0.4, and 0.2 km. It was shown that the modified tidal wave lost most of its energy after reflection or refraction over the eastern part of the German Bight. Energy loss resulted in a pronounced change of the wave’s spectral composition and generation of overtides. Tidal oscillations were modified by mesoscale processes associated with bathymetric channels. Semidiurnal and quarterdiurnal tides revealed very different spatial patterns. The former were aligned with the bathymetric channels, while the latter were rather “patchy” and had about half the spatial scales. In numerous areas around the bathymetric channels, the major axis of the M4 ellipses was normal or at some angle with the major axis of the M2 ellipses. Thus, higher harmonics developed “orthogonal” patterns that drove secondary circulations. Moreover, the ratio between spring and neap tidal amplitudes was relatively low in the Wadden Sea, showing reduced sensitivity of this very shallow area to fortnightly tidal variations. It was demonstrated that simulated hydrodynamics patterns help explain the physical mechanism shaping the median grain size distribution in the German Bight. 相似文献
12.
13.
This work deals with the analysis of simulations carried out with a primitive equation numerical model for the region of the
East Frisian Wadden Sea. The model, with 200-m resolution, is forced by wind, air–sea heat, and water fluxes and river runoff
and is nested in a German Bight 1-km-resolution numerical model, the latter providing tidal forcing for the fine resolution
model. The analysis of numerical simulations is focused both on responses due to moderate conditions, as well as to extreme
events, such as the storm surge Britta, for which the model demonstrates very good skills. The question addressed in this
paper is how well the model output can be compressed with the help of empirical orthogonal function analysis. It is demonstrated
that, for the short-time periods of the order of a spring–neap cycle, only a few modes are necessary to almost fully represent
the circulation. This is just an illustration that the circulation in this region is subject to the dominating tidal forcing,
creating clear and relatively simple response patterns. However, for longer periods of about several months, wind forcing
is also very important, and correspondingly, the circulation patterns become much more complex. Possible applications of the
results in hindcasting and forecasting of hydrodynamics and sediment dynamics in the coastal zone are considered. 相似文献
14.
E.V. Stanev J. Staneva J.L. Bullister J.W. Murray 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):2137-2169
Data from field observations and numerical model simulations are used to understand and quantify the pathways by which passive tracers penetrate into the Black Sea intermediate and deep layers. Chlorofluorocarbon (CFC) concentrations measured during the1988 R.V. Knorr cruise show strong decrease with increasing density in the Black Sea and illustrate the very slow rate of ventilation of deep water in this basin. We develop a 3D numerical model based on the Modular Ocean Model (MOM), and calibrate it in a way to produce consistent simulations of observed temperature, salinity and CFCs. One important feature is the implementation of a special parameterization for convection, which is an alternative of the convective adjustment in MOM and handles the penetration of the Bosporus plume into the halocline. The model forcing includes interannually variable wind, heat and water fluxes constructed from Comprehensive Ocean–Atmosphere Data Set and ECMWF atmospheric analysis data and river runoff data. The analysis of observations and simulated data are focused on correlations between thermohaline and tracer fields, dynamic control of ventilation, and the relative contributions of sources at the sea surface and outflow from the Bosporus Strait in the formation of intermediate and deep waters. A simple theory is developed which incorporates the outflow from the strait along with the vertical circulation (vertical turbulent mixing and Ekman upwelling) and reveals their mutual adjustment. The analyses of simulated and observed CFCs demonstrate that most of the CFC penetrating the deep layers has its source at the sea surface within the Black Sea rather than from the Marmara Sea via the Bosporus undercurrent. Under present-day conditions, the surface CFC signals have reached only the upper halocline. Intrusions below 600 m are not simulated. The major pathways of penetration of CFCs are associated with cold-water mass formation sites, Bosporus effluent, as well as with the diapycnal mixing in the area of Rim Current. Future CFC sampling strategies coherent with the unique conditions in the Black Sea are discussed. 相似文献
15.
Joanna Staneva Victor Alari Øyvind Breivik Jean-Raymond Bidlot Kristian Mogensen 《Ocean Dynamics》2017,67(1):81-101
The effect of wind waves on water level and currents during two storms in the North Sea is investigated using a high-resolution Nucleus for European Modelling of the Ocean (NEMO) model forced with fluxes and fields from a high-resolution wave model. The additional terms accounting for wave-current interaction that are considered in this study are the Stokes-Coriolis force, the sea-state-dependent energy and momentum fluxes. The individual and collective role of these processes is quantified and the results are compared with a control run without wave effects as well as against current and water-level measurements from coastal stations. We find a better agreement with observations when the circulation model is forced by sea-state-dependent fluxes, especially in extreme events. The two extreme events, the storm Christian (25–27 October 2013), and about a month later, the storm Xaver (5–7 December 2013), induce different wave and surge conditions over the North Sea. Including the wave effects in the circulation model for the storm Xaver raises the modelled surge by more than 40 cm compared with the control run in the German Bight area. For the storm Christian, a difference of 20–30 cm in the surge level between the wave-forced and the stand-alone ocean model is found over the whole southern part of the North Sea. Moreover, the modelled vertical velocity profile fits the observations very well when the wave forcing is accounted for. The contribution of wave-induced forcing has been quantified indicating that this represents an important mechanism for improving water-level and current predictions. 相似文献
16.
Bonaduce Antonio Staneva Joanna Grayek Sebastian Bidlot Jean-Raymond Breivik Øyvind 《Ocean Dynamics》2020,70(12):1547-1569
Ocean Dynamics - The contribution of sea-state-induced processes to sea-level variability is investigated through ocean-wave coupled simulations. These experiments are performed with a... 相似文献
17.
Climatic records for the last 15 years indicate that Bulgaria is experiencing a period of exceptionally low precipitation. During 1993, significant water supply problems emerged, approaching crisis proportions in Sofia, the nation's capital, by the end of 1994. The record-setting drought of 1993 can be explained from a synoptic climatic perspective. Whether consequences of the continuing drought could have been foreseen is arguable. That these consequences were fully realized only in 1994 may be understood through examination of Bulgarian water use since the end of the socialist era in 1989. If Bulgaria had experienced the same levels of industrial activity and irrigation as occurred in 1989, the current situation would have been national catastrophe, a situation that could quickly emerge in coming years should climatic patterns persist. 相似文献