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1.
Towards continuous long-term measurements of suspended particulate matter (SPM) in turbid coastal waters 总被引：1，自引：1，他引：0
Thomas H. Badewien Elke Zimmer Alexander Bartholomä Rainer Reuter 《Ocean Dynamics》2009,59(2):227-238
The dynamics of sediment transport in the East Frisian Wadden Sea are important for the coastal zone and for ecosystem functioning.
The tidal inlets between the East Frisian islands connect the back-barrier intertidal flats to the North Sea. Here, concentrations
of suspended particulate matter (SPM) in the water column are highly variable, depending on weather conditions and tides.
In order to estimate the nature and quantity of sediment transport, in situ measurements were carried out at a Time Series
Station in the tidal inlet between the islands of Spiekeroog and Langeoog. This study shows the suitability of multispectral
transmissometry (MST) for obtaining long-term SPM measurements with high resolution. The comparability of this technique to
the standard filter method and the laser diffraction method [laser in situ scattering and transmissometry (LISST)] is demonstrated.
In addition, the Junge coefficients derived from both MST and LISST measurements are compared. A time series of SPM data covering
nearly 4 months is presented. As a major result, the data reveal that a single storm surge can have less impact on SPM dynamics
than longer-lasting gales. This high-resolution long-term data set is very valuable for modelling suspended matter flux. It
also provides background information for studying the influence of SPM dynamics on coastal sediments. 相似文献
2.
Modeling the impact of wind and waves on suspended particulate matter fluxes in the East Frisian Wadden Sea (southern North Sea) 总被引：3，自引：1，他引：2
Suspended particulate matter (SPM) fluxes and dynamics are investigated in the East Frisian Wadden Sea using a coupled modeling
system based on a hydrodynamical model [the General Estuarine Transport Model (GETM)], a third-generation wave model [Simulating
Waves Nearshore (SWAN)], and a SPM module attached to GETM. Sedimentological observations document that, over longer time
periods, finer sediment fractions disappear from the Wadden Sea Region. In order to understand this phenomenon, a series of
numerical scenarios were formulated to discriminate possible influences such as tidal currents, wind-enhanced currents, and
wind-generated surface waves. Starting with a simple tidal forcing, the considered scenarios are designed to increase the
realism step by step to include moderate and strong winds and waves and, finally, to encompass the full effects of one of
the strongest storm surges affecting the region in the last hundred years (Storm Britta in November 2006). The results presented here indicate that moderate weather conditions with wind speeds up to 7.5 m/s and
small waves lead to a net import of SPM into the East Frisian Wadden Sea. Waves play only a negligible role during these conditions.
However, for stronger wind conditions with speeds above 13 m/s, wind-generated surface waves have a significant impact on
SPM dynamics. Under storm conditions, the numerical results demonstrate that sediments are eroded in front of the barrier
islands by enhanced wave action and are transported into the back-barrier basins by the currents. Furthermore, sediment erosion
due to waves is significantly enhanced on the tidal flats. Finally, fine sediments are flushed out of the tidal basins due
to the combined effect of strong erosion by wind-generated waves and a longer residence time in the water column because of
their smaller settling velocities compared to coarser sediments.
相似文献
| Karsten A. LettmannEmail: |
3.
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
4.
Observational data, high-resolution numerical modelling results and a simple analytical theory are combined in this paper to demonstrate the dependence of the volume transports through tidal inlets on topographical or morphological parameters of a Wadden Sea system. The area of interest covers the East Frisian Wadden Sea and consists of seven weakly connected tidal basins. The observations include time series of tidal gauge data and surface currents measured at a pile station in the backbarrier basin of the island Langeoog, as well as several ADCP transects in the Accumer Ee tidal inlet. The numerical simulations are based on the 3-D primitive equation General Estuarine Transport Model (GETM) with a horizontal resolution of 200 m and terrain following vertical coordinates. The model is forced at its open boundaries with sea-level data from an operational model for the German Bight (German Hydrographic Office). The simple theoretical concepts presented illustrate the effect of topography (hypsometry) in the tidal basins on the temporal variability of the exchange of water. This topographic control is effectuated through the bottom slope in the areas prone to drying and flooding. For our study area it takes about twice as long from slack water to maximum flood current than from slack water to maximum ebb current. The underlying physics of this signal modulation from a more or less harmonic forcing at the open-sea boundary and the quantification of the contributing physical processes are the major results of this paper. Estimates based simply on volume conservation are consistent with observations and results from numerical modelling, but they do not completely capture the actual non-linear tidal response. Our analysis shows that at least during part of the tidal cycle characteristic topographic parameters of the inlet/bay system have a major impact on the rate of exchange of waters between the Wadden Sea and the open ocean. This impact is especially strong during the transition between flood and ebb conditions. The possible morphodynamic responses are also addressed focusing on some common (universal) topographic features in seven tidal basins.Responsible Editor: Hans Burchard 相似文献
5.
The Adriatic Sea general circulation model coupled to a third generation wave model SWAN and a sediment transport model was implemented in the Adriatic Sea to study the dynamics of the sediment transport and resuspension in the northern Adriatic Sea (NAS) during the Bora event in January 2001. The bottom boundary layer (BBL) was resolved by the coupled model with high vertical resolution, and the mechanism of the wave–current interaction in the BBL was also represented in the model. The study found that, during the Bora event of 13–17 January 2001, large waves with significant wave height 2 m and period of 5 s were generated by strong winds in the northwestern shelf of the Adriatic where the direction of wave propagation was orthogonal to the current. The combined motion of the wave and current in the BBL increased the bottom stress over the western Adriatic shelf, resulting in stronger sediment resuspension there. Combining stronger bottom resuspension and strong upward vertical flux of resuspended sediments due to turbulent mixing, the model predicted that sediment concentration near the Po River was much higher than that predicted by the model run without wave forcing. The study also shows that wave–current interaction in the BBL reduced the western Adriatic Coastal Currents (WACCs) in the shallower north. It is concluded that wave forcing significantly changed the sediment distributions and increased the total horizontal fluxes over the western shelf. These results signified wave effect on sediment flux and distribution in the NAS, and suggested that waves cannot be neglected in the study of dynamics of sediment transport and resuspension in the shallow coastal seas. By including the tidal forcing in the coupled model, we also examined the effect of tides on the sediment transport dynamics in the NAS. 相似文献
6.
Rainer Reuter Thomas H. Badewien Alexander Bartholomä Axel Braun Andrea Lübben Jürgen Rullkötter 《Ocean Dynamics》2009,59(2):195-211
In the tidal inlet between the East Frisian islands of Langeoog and Spiekeroog, southern North Sea, a time-series station
was set up in autumn 2002 as part of the research programme BioGeoChemistry of Tidal Flats run by the University of Oldenburg. The purpose of the station is to provide continuous data on physical, biological and
chemical parameters. In addition to instruments recording basic hydrographic and meteorological parameters, the time-series
station is equipped with acoustic Doppler profilers for measuring surface waves and current profiles. Compact optical spectrometers
are being used for spectral measurements of seawater transmission and for daylight reflectance. Additional sensors were installed
for measuring oxygen, nutrients and methane in the seawater. The data shall help to quantify the flux of dissolved and suspended
matter between the backbarrier tidal flat and the open sea and to characterise the material transformation in the tidal flat
area by biogeochemical processes over the tidal cycle. Due to its novel design, operation of the station is also possible
during winter and under extreme weather conditions (gales, storm surges, and sea ice) when data sampling with conventional
platforms such as research vessels, buoys, or smaller poles could not be performed in the past. In this way, time series of
data are obtained, which include events that are most relevant to the evolution of this coastal area. The performance of the
station and its equipment are presented with data covering 6 years of operation. Time series of air and water temperature
as well as seawater salinity demonstrate the multiyear dynamics of these parameters in the East Frisian Wadden Sea. Hydrographic
data collected under specific meteorological conditions such as gales and storm surges exemplify the all-weather capabilities
of the station and its value for studying hydrographic processes in the Wadden Sea. 相似文献
7.
8.
Here, we address the sediment dynamics in the Black Sea based on analysis of remote sensing data from the Medium Resolution
Imaging Spectrometer and numerical simulations with Nucleus for European Modelling of the Ocean model. Boundary conditions
consist of realistic meteorological forcing, including significant wave height generated by wave prediction model. A number
of sensitivity runs was analysed with the aim to find the most suitable parameters governing sediment fluxes. The comparison
between numerical simulations and remote sensing data gives credibility to the quality of simulations. The combined effect
of wind waves and currents in the bed layer controls the sediment resuspension that appears to be the major basin-wide source
of sediment. Sensitivity experiments included or excluded different forcing terms, e.g. sediment flux from rivers enable to
determine the spatial extensions of different point sources. It is concluded that wind-wave forcing is manifested in the sediment
dynamics through episodic high energy events contributing to the increase of horizontal sediment fluxes over the northwestern
shelf. Both satellite images and numerical model simulations demonstrated that the penetration of suspended sediment into
the basin interior was governed by the dynamics of coastal and open-ocean eddies. While fine sediment at sea surface could
cross the continental slope propagating into the open ocean, coarser fractions follow the bottom and their penetration into
the open ocean is limited. The conclusion is thus that the deposition patterns correlate with the specific shape of Black
Sea topography, and the largest depositions are observed in the area of continental slope. 相似文献
9.
Emil V. Stanev Jörg-Olaf Wolff Hans Burchard Karsten Bolding Götz Flöser 《Ocean Dynamics》2003,53(1):27-51
In this paper we use a combination of numerical modeling and data analysis to gain a better understanding of the major characteristics
of the circulation in the East Frisian Wadden Sea. In particular, we concentrate on the asymmetry of the tidal wave and its
modulation in the coastal area, which results in a complex pattern of responses to the sea-level forcing from the North Sea.
The numerical simulations are based on the 3-D primitive equation General Estuarine Transport Model (GETM) with a horizontal
resolution of 200 m and terrain-following vertical coordinates. The model is forced at its open boundaries with sea-level
data from an operational model for the German Bight (German Hydrographic Office). The validation data for our model simulations
include time series of tidal gauge data and surface currents measured at a pile in the back-barrier basin of the Island Langeoog,
as well as several ADCP transects in the Accumer Ee tidal inlet.
Circulation and turbulence characteristics are investigated for typical situations driven by spring and neap tides, and the
analysis is focused on dominating temporal and spatial patterns. By investigating the response of five back-barrier basins
with rather different morphologies to external forcing, an attempt is made to elucidate the dominating physical balances controlling
the circulation in the individual sub-basins. It is demonstrated that the friction at the seabed tends to slow down the tidal
signal in the shallow water. This leads to the establishment of flood dominance in the shallow sea north of the barrier islands.
South of the islands, where the water volume of the channels at low tide is smaller than the tidal prism, the asymmetry of
the tidal signal is shifted towards ebb dominance, a feature which is particularly pronounced at spring tide.
At the northern open boundary, the tidal wave propagating from west to east generates a sea-level difference of ∼1 m along
the boundary, and thereby triggers vigorous alongshore currents. The frictional control in the model is located in the inlets,
as well as along the northern boundary. The correlation between velocity and turbulent kinetic energy tends to the establishment
of a net southward transport, giving theoretical support to the observed accumulation of sediments on the intertidal flats.
Weak turbulence along the northern shores of the barrier islands and the small magnitude of the residual currents there promote
accumulation of suspended matter in these areas, although wave action will generally counteract this effect.
Received: 29 May 2002 / Accepted: 26 September 2002
Responsible Editor: Jean-Marie Beckers
Acknowledgements We are indebted to S. Dick for providing the data from the operational model of BSH and to B. Flemming for the useful discussions.
The topography data and Fig. 1 have been prepared in cooperation with F. Meyer. Figure 2 has been prepared by G. Brink-Spalink.
We also thank for the comments from an anonymous reviewer which helped to improve our paper. 相似文献
10.
Local and remote response of the North Sea dynamics to morphodynamic changes in the Wadden Sea 总被引：1，自引：1，他引：0
The response of the tidal system in the southern North Sea to morphodynamic changes was investigated in a modelling study using fine resolution bathymetric observations available for 1982–2011. The Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM) was set up for the different sets of bathymetries. One set of bathymetry was compiled from a large number of bathymetric measurements over many years, while the other two reflected bathymetry state in the area of Wadden Sea during 2000 and 2011, respectively. The temporal and spatial evolution of bathymetry was dominated by migration of tidal channels. The M4 tide showed larger sensitivity to bathymetric change in the Wadden Sea than the M2 tide, whereas the structure of the latter remained rather robust. The largest change of the tidal wave due to the differences in bathymetries was located off the North Frisian Wadden Sea. Traces of changes were also found far away from the regions of their origin because the tidal waves in the North Sea propagate the local disturbances basin-wide. This illustrated an efficient physical mechanism of teleconnectivity, i.e. effecting the local responses to the larger-scale or remote change of ocean bottom caused by erosion and deposition. The tidal distortion resulting from the relatively small bathymetric changes was substantial, particularly in the coastal zone. This is a manifestation of the nonlinear tidal transformation in shallow oceans and is crucial for the sediment transport and the morphodynamic feedback, because of the altered tidal asymmetry. 相似文献
11.
Daan Wesselman Renske de Winter Anita Engelstad Robert McCall Ap van Dongeren Piet Hoekstra Albert Oost Maarten van der Vegt 《地球表面变化过程与地形》2018,43(3):579-592
Under natural conditions, barrier islands might grow vertically and migrate onshore under the influence of long‐term sea level rise. Sediment is transported onshore during storm‐induced overwash and inundation. However, on many Dutch Wadden Islands, dune openings are closed off by artificial sand‐drift dikes that prevent the influx of sediment during storms. It has been argued that creating openings in the dune row to allow regular flooding on barrier islands can have a positive effect on the sediment budget, but the dominant hydrodynamic processes and their influence on sediment transport during overwash and inundation are unknown. Here, we present an XBeach model study to investigate how sediment transport during overwash and inundation across the beach of a typical mesotidal Wadden Sea barrier island is influenced by wave, tide and storm surge conditions. Firstly, we validated the model XBeach with field data on waves and currents during island inundation. In general, the XBeach model performed well. Secondly, we studied the long‐term sediment transport across the barrier island. We distinguished six representative inundation classes, ranging from frequently occurring, low‐energy events to infrequent, high‐energy events, and simulated the hydrodynamics and sediment transport during these events. An analysis of the model simulations shows that larger storm events cause larger cross‐shore sediment transport, but the net sediment exchange during a storm levels off or even becomes smaller for the largest inundation classes because it is counteracted by larger mean water levels in the Wadden Sea that oppose or even reverse sediment transport during inundation. When taking into account the frequency of occurrence of storms we conclude that the cumulative effect of relatively mild storms on long‐term cross‐shore sediment transport is much larger than that of the large storm events. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. 相似文献
12.
A large number of sediment cores collected during 2005-2010 from the Taiwan Strait were analyzed for radionuclides (210Pb, 137Cs and 7Be) to elucidate sedimentation dynamics in this all-important gateway linking two largest marginal seas in the western Pacific (namely, the South China Sea and the East China Sea). Apparent sediment accumulation rates derived from 210Pb and 137Cs profiles vary from <0.1 to >2 cm/yr, averaging ∼0.4 cm/yr and showing a spatial pattern closely related to hydrodynamics and sediment source-to-sink pathways. Spatial-temporal variation of 7Be activity in surface sediments off Taiwan’s west coast indicates episodic deposition of flood layers and their mobility from river estuaries toward the north. In conjunction with particle size distribution in surface sediments and the structure of sediment strata revealed by sub-bottom echo images; the radionuclide data can be used to outline three different sediment source-to-sink dispersal systems. Based on sediment loads of surrounding rivers and the distribution of sediment accumulation rates, lateral transport is required to account for the budget and size distribution of sediments in the strait. 相似文献
13.
Johannes Becherer Jacobus Hofstede Ulf Gräwe Kaveh Purkiani Elisabeth Schulz Hans Burchard 《Ocean Dynamics》2018,68(1):131-151
The impact of sea level rise (SLR) on the future morphological development of the Wadden Sea (North Sea) is investigated by means of extensive process-resolving numerical simulations. A new sediment and morphodynamic module was implemented in the well-established 3D circulation model GETM. A number of different validations are presented, ranging from an idealized 1D channel over a semi-idealized 2D Wadden Sea basin to a fully coupled realistic 40-year hindcast without morphological amplification of the Sylt-Rømøbight, a semi-enclosed subsystem of the Wadden Sea. Based on the results of the hindcast, four distinct future scenarios covering the period 2010–2100 are simulated. While these scenarios differ in the strength of SLR and wind forcing, they also account for an expected increase of tidal range over the coming century. The results of the future projections indicate a transition from a tidal-flat-dominated system toward a lagoon-like system, in which large fractions of the Sylt-Rømøbight will remain permanently covered by water. This has potentially dramatic implications for the unique ecosystem of the Wadden Sea. Although the simulations also predict an increased accumulation of sediment in the back-barrier basin, this accumulation is far too weak to compensate for the rise in mean sea level. 相似文献
14.
In order to simulate the dynamics of fine sediments in short tidal basins, like the Wadden Sea basins, a 1D cross-sectional averaged model is constructed to simulate tidal flow, depth-limited waves, and fine sediment transport. The key for this 1D model lies in the definition of the geometry (width and depth as function of the streamwise coordinate). The geometry is computed by implementing the water level and flow data, from a 2D flow simulation, and the hypsometric curve in the continuity equation. By means of a finite volume method, the shallow-water equations and sediment transport equations are solved. The bed shear stress consists of the sum of shear stresses by waves and flow, in which the waves are computed with a depth-limited growth equation for wave height and wave frequency. A new formulation for erosion of fines from a sandy bed is proposed in the transport equation for fine sediment. It is shown by comparison with 2D simulations and field measurements that a 1D schematization gives a proper representation of the dynamics in short tidal basins.
相似文献15.
In order to simulate the dynamics of fine sediments in short tidal basins, like the Wadden Sea basins, a 1D cross-sectional averaged model is constructed to simulate tidal flow, depth-limited waves, and fine sediment transport. The key for this 1D model lies in the definition of the geometry (width and depth as function of the streamwise coordinate). The geometry is computed by implementing the water level and flow data, from a 2D flow simulation, and the hypsometric curve in the continuity equation. By means of a finite volume method, the shallow-water equations and sediment transport equations are solved. The bed shear stress consists of the sum of shear stresses by waves and flow, in which the waves are computed with a depth-limited growth equation for wave height and wave frequency. A new formulation for erosion of fines from a sandy bed is proposed in the transport equation for fine sediment. It is shown by comparison with 2D simulations and field measurements that a 1D schematization gives a proper representation of the dynamics in short tidal basins. 相似文献
16.
In situ observations were combined with 3D modeling to gain understanding of and to quantify the suspended sediment transport in the Gulf of Lions (NW Mediterranean Sea). The outputs of a hydrodynamic–sediment transport coupled model were compared to near-bottom current and suspended sediment concentration measurements collected at the head of seven submarine canyons and at a shallow shelf site, over a 6-month period (November 2003–May 2004). The comparisons provide a reasonable validation of the model that reproduces the observed spatial and time variations. The study period was marked by an unusual occurrence of marine storms and high river inputs. The major water and sediment discharges were supplied by the Rhone, the largest Mediterranean river, during an exceptional flood accompanying a severe marine storm in early December 2003. A second major storm, with moderate flooding, occurred in February 2004. The estimate of river input during the studied period was 5.9 Mt. Our study reveals (i) that most of the particulate matter delivered by the Rhone was entrapped on the prodelta, and (ii) that marine storms played a crucial role on the sediment dispersal on the shelf and the off-shelf export. The marine storms occurring in early December 2003 and late February 2004 resuspended a very large amount of shelf sediment (>8 Mt). Erosion was controlled by waves on the inner shelf and by energetic currents on the outer shelf. Sediment deposition took place in the middle part of the shelf, between 50 and 100 m depth. Resuspended sediments and river-borne particles were transported to the southwestern end of the shelf by a cyclonic circulation induced by these onshore winds and exported towards the Catalan shelf and into the Cap de Creus Canyon which incises the slope close to the shore. Export taking place mostly during marine storms was estimated to reach 9.1 Mt during the study period. 相似文献
17.
Christian Ferrarin Andrea Cucco Georg Umgiesser Debora Bellafiore Carl L. Amos 《Continental Shelf Research》2010
To describe the exchange of water and sediment through the Venice Lagoon inlets a 3-D hydrodynamic and sediment transport model has been developed and applied to a domain comprising Venice Lagoon and a part of the Adriatic Sea. The model has been validated for both current velocities and suspended particle concentration against direct observations and from observations empirically derived fluxes from upward-looking acoustic Doppler current profiler probes installed inside each inlet. The model provides estimates of the suspended sediment transport in the lower 3 m of the water column that is not detected by acoustic Doppler current profiler sensors. The bedload model prediction has been validated against measured sand transport rates collected by sand traps deployed in the Lido and Chioggia inlets. Results indicate that, in the Lido inlet, 87% of the total load is in suspension, while the rest moves as bedload. 相似文献
18.
Seasonal variation of upper layer circulation in the northern part of the East/Japan Sea and its mechanism were investigated using empirical orthogonal function (EOF) analysis with satellite sea surface heights over the northern East/Japan Sea and a three-dimensional circulation model. The spatial structure and temporal variation of first EOF mode, which explains about 64% of the total variance, indicate that a large cyclonic circulation in the northern East/Japan Sea shows a semi-annual variation with maximum strength in summer and winter. According to numerical model result, the Liman Cold Current, accepted as a major current in the northern East/Japan Sea, is well mixed vertically by the winter monsoon and the current in the upper layer has a relatively deep structure, with a maximum westward speed of about 20 cm/s in winter. On the other hand, in summer the current has a stronger baroclinic structure of velocity than in winter. Numerical experiments showed that in summer the temporal variation of upper layer circulation is controlled by thermal forcing, such as sea surface heat flux and inflow of heat transport into the East/Japan Sea through the Korea/Tsushima Strait. Moreover, the cyclonic circulation in the upper layer of the northern East/Japan Sea is also generated and strengthened by the positive wind stress curl occupying most of the East/Japan Sea during the winter. The seasonal variation of each forcing that drives the circulation is responsible for the strength or weakness of the upper layer circulation in the northern East/Japan Sea. The contribution of each forcing to the seasonal variation of the upper layer circulation is examined through sensitivity experiments. According to these numerical experiments, the upper layer circulation in the northern East/Japan Sea is strengthened twice a year, in winter and summer, and this semi-annual variation is determined by a combination of wind (winter) and thermal (summer) forcing. 相似文献
19.
Daphne van der Wal Thijs van Kessel Marieke A. Eleveld Joris Vanlede 《Ocean Dynamics》2010,60(3):519-533
The fate of mud in an estuary over an entire year was unravelled using complementary, independent, spatially explicit techniques.
Sequential ERS-2 SAR and Envisat MERIS-FR data were used to derive synoptic changes in intertidal bottom mud and suspended
particulate matter (SPM) in the top of the water column, respectively. These satellite data were combined with in situ measurements
and with a high resolution three-dimensional cohesive sediment model, simulating mud transport, resuspension, settling and
deposition under the influence of tides, wind, waves and freshwater discharge. The spatial distribution of both bottom mud
and SPM as observed by in situ and satellite techniques was largely explained by modelled estuarine circulation, tidal and
wind-induced variations in vertical mixing and horizontal advection. The three data sources also showed similar spring-neap
and seasonal variations in SPM (all factor 1.5 to 2), but semi-diurnal tidal variations were underestimated by the model.
Satellite data revealed that changes in intertidal bottom mud were spatially heterogeneous, but on average mud content doubled
during summer, which was confirmed by in situ data. The model did not show such seasonal variation in bed sediment, suggesting
that seasonal dynamics are not well explained by the physical factors presently implemented in the model, but may be largely
attributed to other (internal) factors, including increased floc size in summer, temporal stabilisation of the sediment by
microphytobenthos and a substantially lower roughness of the intertidal bed in summer as observed by the satellite. The effects
of such factors on estuarine mud dynamics were evaluated. 相似文献
20.
A series of numerical experiments for data assimilation with the Ensemble Kalman Filter (EnKF) in a shallow water model are
reported. Temperature profiles measured at a North Sea location, 55°30ˊ North and 0°55ˊ East (referred to as the CS station
of the NERC North Sea project), are assimilated in 1-D simulations. Comparison of simulations without assimilation to model
results obtained when assimilating data with the EnKF allows us to assess the filter performance in reproducing features of
the observations not accounted for by the model. The quality of the model error sampling is tested as well as the validity
of the Gaussian hypothesis underlying the analysis scheme of the EnKF. The influence of the model error parameters and the
frequency of the data assimilation are investigated and discussed. From these experiments, a set of optimal parameters for
the model error sampling are deduced and used to test the behavior of the EnKF when propagating surface information into the
water column. 相似文献