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1.
The paper presents a numerical two-dimensional model (with a realistic sea basin and wind fields as exter nal forcing) to simulate the basic features of the wintertime circulation in the Bohai and Huanghai (Yellow) Seas (BHS) and to show how the circulation can be driven by wind. The main results can be summarized as follows (1) The basic features of the BHS wintertime circulation can be depicted by the wind-driven barotropi'c motion. (2) The traditionally named Huanghai Sea Warm Current (HSWC) is actually generated by the north wind field, at least in winter. (3) The southward coastal current off the Korean west coast plays a more significant role in the southern Huanghai Sea wintertime circulation than traditionally believed. (4) Though the coastal landform and bottom topography play important roles in the wintertime BHS circulation pattern, the wind is a primary forcing.  相似文献   

2.
An advanced ocean observatory has been established in Lunenburg Bay of Nova Scotia, Canada as part of an interdisciplinary research project of marine environmental prediction. The development of a high-resolution coastal circulation model is one of important components of the observatory. The model horizontal resolution is 60m and the vertical resolution is about 1 m. The coastal circulation model is used to simulate the semi-diurnal tidal circulation and associated nonlinear dynamics with the M2 forcing specified at the model open boundaries. The model is also used to simulate the storm-induced circulation in the bay during Hurricane Juan in September 2003, with the model forcing to be the combination of tides and remotely generated waves specified at the model open boundaries and wind stress applied at the sea surface. The model results demonstrate strong interactions between the local wind stress, tidal forcing, and remotely generated waves during this period. Comparison of model results with the surface elevation and current observations demonstrates that the coastal circulation model has reasonable skills in simulating the tidal and storm-induced circulation in the bay.  相似文献   

3.
1Introduction GamakBay,anegg shapedseasurfaceareaofap proximately112km2,isasemi enclosedshallowwaterareawithameandepthof9mandhasbotheastandsouthchannelstoreceiveseawaterfromoutside(seeFig.1).Similarscalesoftidalwavesalmostsimultane ouslyenterorexitthrough…  相似文献   

4.
Six coupled general circulation models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are employed for examining the full evolution of the North Pacific mode water and Subtropical Countercurrent (STCC) under global warming over 400 years following the Representative Concentration Pathways (RCP) 4.5. The mode water and STCC first show a sharp weakening trend when the radiative forcing increases, but then reverse to a slow strengthening trend of smaller magnitude after the radiative forcing is stablized. As the radiative forcing increases during the 21st century, the ocean warming is surface-intensified and decreases with depth, strengthening the upper ocean’s stratification and becoming unfavorable for the mode water formation. Moving southward in the subtropical gyre, the shrinking mode water decelerates the STCC to the south. After the radiative forcing is stabilized in the 2070s, the subsequent warming is greater at the subsurface than at the sea surface, destabilizing the upper ocean and becoming favorable for the mode water formation. As a result, the mode water and STCC recover gradually after the radiative forcing is stabilized.  相似文献   

5.
Spatial distribution and seasonal variation of explosive cyclones (ECs) over the North Atlantic from October 2000 to September 2016 are investigated using the reanalysis data of Final Analysis (FNL), Mean Sea Level Pressure (MSLP) and Optimum Interpolation (OI) Sea Surface Temperature (SST) provided by the National Centers for Environmental Prediction (NCEP), the European Centre for Medium-Range Weather Forecasts (ECMWF) and the National Oceanic and Atmospheric Administration (NOAA), respectively. Considering the meridional distribution of ECs and 10-m height wind field associated with the ECs, the definition of EC given by Yoshida and Asuma (2004) is modified. It is found that the ECs occurred mainly in four regions during winter season, namely, North America continent (NAC), the Northwest Atlantic (NWA), the North-central Atlantic (NCA), and the Northeast Atlantic (NEA), depending on the spatial distribution of EC’s maximum deepening rate of central sea level pressure (SLP). According to the magnitude of maximum deepening rate, the trend of EC numbers basically decrease with the increase of EC’s maximum deepening rate over the North Atlantic during the whole time period. Over the North Atlantic basin, for monthly statistics, the NEA, NCA, and NWA cyclones occur mainly in December, from December to March, and from January to February, respectively. NWA, NCA and NEA cyclones in winter are associated with low-level baroclinicity, both low-level baroclinicity and upper-level forcing and upper-level forcing, respectively. According to monthly variation, the averaged maximum deepening rate of central SLP firstly increases and then decreases from July to June. Overall, the distribution of ECs’ tracks is basically in the southwest-northeast direction. During winter circulation stage (from October to May), the averaged maximum deepening rate of central SLP and the averaged minimum central SLP of ECs decrease, and the averaged explosive-deepening duration of ECs shortens from west to east over the North Atlantic basin. During summer circulation stage (from June to September), the number of ECs is far less than that of winter circulation. NCA cyclones are the lowest in the average minimum central SLP of ECs, and the longest in the average explosive- deepening duration of ECs. NEA cyclones are the strongest in the average maximum deepening rate of central SLP.  相似文献   

6.
Anchovy (Engraulis japonicus), a small pelagic fish and food of other economic fishes, is a key species in the Yellow Sea ecosystem. Understanding the mechanisms of its recruitment and biomass variation is important for the prediction and management of fishery resources. Coupled with a hydrodynamic model (POM) and a lower trophic level ecosystem model (NEMURO), an individual-based model of anchovy is developed to study the influence of physical environment on anchovy’s biomass variation. Seasonal variations of circulation, water temperature and mix-layer depth from POM are used as external forcing for NEMURO and the anchovy model. Biomasses of large zooplankton and predatory zooplankton which anchovy feeds on are output from NEMURO and are controlled by the consumption of anchovy on them. Survival fitness theory related to temperature and food is used to determine the swimming action of anchovy in the model. The simulation results agree well with observations and elucidate the influence of temperature in over-wintering migration and food in feeding migration.  相似文献   

7.
A probabilistic view of debris flow   总被引：1，自引：1，他引：0  
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8.
In the investigation of debris flow, the detection of the source area of the post-disaster debris flow is an important basis for evaluating the distribution of the debris flow accumulation layer and the subsequent control. In this paper, a shallow high-resolution TEM is used to detect the debris flow source area in Dashigou village, Yongji County, Jilin Province. The purpose of this investigation is to determine the depth range of debris flow damage. The detection results show that there is an obvious low resistance zone at about 10 m depth along the survey line, which is in good agreement with the drilling data and the high density electrical detection. It is proved that the depth is the maximum impact depth of the debris flow. The practical engineering proves that the method has high resolution in shallow layer detection, high efficiency and convenience in field acquisition. The maximum detection depth range of this method is 30--40 m, which meets the requirements of high efficiency and accurate detection for regional debris flow source area, and has high practical application value.  相似文献   

9.
由地下水补给、径流和排泄过程构成的地下水循环运动，是水文循环的重要组成部分，也是水文地质学的基本研究对象。地下水循环在空间上表现为不同结构单元的组合，存在以含水层特性为依据的介质结构和以渗流场为依据的动力结构2种划分方法。地下水流系统是动力结构意义上的地下水循环单元。近10年来，区域地下水流系统理论取得了显著进展，更加全面深入地揭示了地下水循环结构的动力学特性。通过对河间地块地下水流系统的研究，发现潜水面最高点并非地下水分水岭的准确位置。在盆地尺度上，系统研究了沟谷地貌、降水入渗强度、渗透性随埋深变化和盆地厚度等因素对潜水面波形与地下水循环动力结构的影响，初步发现了动力结构的周期性或趋势性演化特征。通过大规模流线路径的精细识别或驻留时间的统计分析，提出了三维地下水循环单元的划分方法。在水文地质效应方面，发现地下水循环的动力结构对地下水年龄的分布有重要影响。地下水循环的动力结构反映了不同补给区和排泄区之间的水力联系，在盆地尺度地球化学过程、流域尺度生态水文过程中发挥着关键作用，未来的研究重点是三维地下水循环的动力特性和演变规律。   相似文献   

10.
This paper presents the results from laboratory experiments and theoretical analysis to investigate the development of scour around submarine pipeline under steady current conditions. Experiments show that the scour process takes place in two stages: the initial rapid scour and the subsequent gradual scour development stage. An empirical formula for calculating the equilibrium scour depth (the maximum scour depth) is developed by using the regression method. This formula together with the maximum entropy theory can be applied to establish a formula to predict the scour process for given water depth, diameter of pipeline and flow velocity. Good agreement between the predicted and measured scour depth is obtained.  相似文献   

11.
地下水垂向循环水动力条件是岩溶发育深度的主要控制因素。为探求川东背斜构造岩溶区多级水流系统控制下的岩溶强发育深度，采用地理信息系统（GIS）技术，选取地形指数和水动力坡降构建岩溶水动力强弱的量化因子FHQ，并结合钻孔数据推求假角山背斜构造区地下岩溶强发育深度。研究显示:水动力因子FHQ与地形指数、水动力坡降在空间上呈明显正相关关系，同时可指示岩溶水流系统向深循环的深度，以此推求背斜构造区地下岩溶的强发育深度下限。假角山背斜两翼FHQ集中在0.1~0.4之间，岩溶水动力整体偏弱，深沟FHQ值整体高于浅沟。东、西翼深沟控制下的地下岩溶强发育深度分别约40~100 m和110~180 m；浅沟控制下的地下岩溶强发育深度分别约15~60 m和10~90 m。研究成果可进一步丰富川东背斜区岩溶发育评价方法体系，为隧道工程岩溶突水灾害预测防治提供理论依据。   相似文献   

12.
We present a three-level nested-grid ocean circulation modeling system for the Belize shelf of the western Caribbean Sea. The nested-grid system has three subcomponents： a coarse-resolution outer model of the western Caribbean Sea; an intermediate-resolution middle model of the southern Mest〉American Barrier Reef System; and a fine-resolution inner model of the Belize shelf. The two-way nesting technique based on the semi-prognostic method is used to exchange information between the three subcomponents. We discuss two applications of the nested-grid system in this study. In the first application we simulate the seasonal mean circulation in the region, with the nested system forced by monthly mean surface fluxes and boundary forcing. The model results reproduce the general circulation features on the western Caribbean Sea and mest〉scale circulation features on the Belize shelf. In the second application, we simulate the storm-induced circulation during Hurricane Mitch in 1998, with the nested-grid system forced by the combination of monthly mean forcing and idealized wind stress associated with the storm. The model results demonstrate that the storm-induced currents transport a large amount of estuarine waters from coastal regions of Honduras and Guatemala to offshore reef atolls.  相似文献   

13.
Debris flows have caused serious human casualties and economic losses in the regions strongly affected by the Ms8.0 Wenchuan earthquake of 2008. Debris flow mitigation and risk assessment is a key issue for reconstruction.The existing methods of inundation simulation are based on historical disasters and have no power of prediction.The rain-flood method can not yield detailed flow hydrograph and does not meet the need of inundation simulation. In this paper,the process of water flow was studied by using the Arc-SCS model combined with hydraulic method,and then the debris flow runoff process was calculated using the empirical formula combining the result from Arc-SCS.The peak discharge and runoff duration served as input of inundation simulation. Then,the dangerous area is predicted using kinematic wave method and Manning equation.Taking the debris flow in Huashiban gully in Beichuan County,Sichuan Province,China on 24 Sep.2008 as example,the peak discharge of water flow and debris flow were calculated as 35.52 m3·s-1 and 215.66 m3·s-,with error of 4.15%compared to the measured values.The simulated area of debris-flow deposition was 161,500 m2,vs.the measured area of 144,097 m2,in error of 81.75%.The simulated maximum depth was 12.3 m,consistent with the real maximum depth between 10 and 15 m according to the field survey.The minor error is mainly due to the flow impact on buildings and variations in cross-section configuration.The present methodology can be applied to predict debris flow magnitude and evaluate its risk in other watersheds inthe earthquake area.  相似文献   

14.
Current data from a moored Acoustic Doppler Current Profiler(ADCP) deployed at 69?30.155′N,169?00.654′W in the central Chukchi Sea during 2012 summertime is analyzed in the present paper.Characteristics of tidal and residual currents are ob-tained with Cosine-Lanczos filter and cross-spectral analyses.The main achievements are as follows:1) Along with the local inertial frequency of 12.8 h,two other peaks at ~12-h and ~10-d dominate the time series of raw velocity;2) The M_2 dominates the 6 resolved tide constituents with significant amplitude variations over depth and the ratios of current speed of this constituent to that of the total tidal current are 54% and 47% for u and v components,respectively.All the resolved tidal constituents rotate clockwise at depth with the exception of MM and O1.The constituents of M_2 and S_2 with the largest major semi-axes are similar in eccentricity and orientation at deeper levels;3) The maximum of residual currents varies in a range of 20–30 cms~(-1) over depth and the current with lower velocities flow more true north with smaller magnitudes compared to the current in surface layer.The ~10 d fluctuation of residual current is found throughout the water column and attributed to the response of current to the local wind forcing,with an approximate 1.4 d lag-time at the surface level and occurring several hours later in the lower layer;4) Mean residual currents flow toward the north with the magnitudes smaller than 7 cms~(-1) in a general agreement with previous studies,which suggests a relatively weaker but stable northward flow indeed exists in the central Chukchi Sea.  相似文献   

15.
The erosion shape and the law of development of debris flow sabo dam downstream is a weak part in the study on debris flow erosion. The shape and development of scour pit have an important effect on the stability and safety of debris flow sabo dam, which determines the foundational depth of the dam and the design of protective measures downstream. Study on the scouring law of sabo dam downstream can evaluate the erosion range and reasonably arrange auxiliary protective engineering. Therefore, a series of flume experiments are carried out including different debris flow characteristics （density is varying from 1.5 t/m3 to 2.1 t/m~） and different gully longitudinal slopes. The result shows that the scour pit appears as an oval shape in a plane and deep in the middle while superficial at the ends in the longitudinal section, the position of the maximum depth point moves towards downstream with an increase of flume slope angle. The maximum depth of scour pit is mainly affected by the longitudinal slope of gully, density of debris flow, and the characteristics of gully composition （particle size and the viscosity of soil）. The result also indicates that the viscosity of soil will weaken the erosion extent. The interior slopes of scour pit are different between the upstream and the downstream, and the downstream slope is smaller than the upper one. For the viscous and non-viscous sands with the same distribution of gradation, the interior slope of non- viscous sand is smaller than the viscous sand.According to tbe regression analysis on the experimental data, the quantitative relationship between the interior slope of scour pit, slope of repose under water and the longitudinal slope of gully is established and it can be used to calculate the interior slope of scour pit. The results can provide the basis for the parameter design of the debris flow control engineering foundation.  相似文献   

16.
The Florida Current （FC） largely fills the Straits of Florida and is variable on a broad spectrum of time and space scales. Some portions of the variability are due to variable forcing by tides, winds, heating/cooling, and throughflow; other portions are due to intrinsic instabilities of the FC. To predict, as well as to better understand this complex regime, a nowcast/forecast system （East Florida Shelf Information System （EFSIS）） has been implemented and assessed （http：//efsis. rsmas. miami. edu）. EFSIS is based on an implementation of the Princeton Ocean Model （POM） with mesoscale-admitting resolution on a curvilinear grid. It is forced by a mesoscale numerical weather prediction system （called Eta） run operationally by the National Centers for Environmental Prediction （NCEP）, eight tidal constituents from a global tidal model, and lateral boundary conditions from an operational global ocean prediction model, i.e., the Navy Coastal Ocean Model （NCOM）. Real-time observations of coastal sea level, coastal sea surface temperature, coastal HF radar-derived surface current maps, and FC volume transport are used to verify and validate EFSIS. EFSIS is part of an evolving strategy for real-time predictive coastal ocean modeling methodology, and for fostering the understanding of the variability of the regime on several time and space scales. Here, some of the verification and validation results are provided, as well as diagnostic analyses of dynamical processes. The central point is that an example is provided of a ＇scientific revolution＇ in progress that combines real-time observations and numerical circulation models to yield a credible sequence of synoptic views of coastal ocean circulation for the first time.  相似文献   

17.
The mega debris flow occurred on August 13 th 2010 in Qingping town,China(hereafter called ’8.13’ Debris Flow) have done great damage to the local habitants as well as to the re-construction projects in the quake-hit areas,and the channel-fill deposit problem caused by the debris flow was the most destructive.Moreover,it is of high possibility that an even severe deposit problem would reappear and result in worse consequences.In order to maximize risk reduction of this problem,relevant departments of the government established a series of emergency river restoration schemes,for which the numerical analysis is an important procedure to evaluate and determine the optimized one.This study presents a numerical analysis by applying a twodimensional debris flow model combined with a relevant water-sediment model to simulate the deposit during the progress of the debris flow,and to calculate and analyze the river flow field under both the present condition and different restoration conditions.The results show that the debris flow model,which takes the confluence of the Wenjia Gully to the main river into account,could simulate the deposit process quite well.In the reproduced debris flow from the simulation of the ’8.13’ Debris Flow,the original river flow path has switched to a relatively lower place just along the right bank with a high speed of near 7m.s-1 after being blocked by the deposit,which is highly hazardous.To prevent this hazard,a recommended scheme is derived through inter-comparison of different restoration conditions.It shows that the recommended scheme is able to reduce the water level and as well to regulate the flow path.Based on the given conditions of the mainstream and the tributary confluence for the simulated ’8.13’ Debris Flow,when encountering a debris flow with deposit volume less than 0.5 million m3,the river channel can endure a 20-year return flood;however,when the deposit volume increases to 2 million m3,the flood capacity of the river will be greatly impacted and the scheme becomes invalid.The recommended scheme supported by the present study has been applied to the emergency river restoration after this mega-debris flow.  相似文献   

18.
温度是地下水的固有属性，地下水温度场和动态特征是地下水流系统的外在表现。为揭示地下水开采等人类活动影响下西北内陆盆地浅层地下水温度场特征与地下水流系统的关系，基于多点位、长序列、高精度的地下水温度监测数据，在酒泉东盆地开展了地下水温度场及动态特征研究。结果表明:酒泉东盆地浅层地下水温度9.33~20.77℃不等，平均水温为13.54℃，自地下水补给区至排泄区，沿地下水径流方向，浅层地下水温度逐渐升高；循环深度相近的不同地下水流系统对比表明，浅层地下水温度与地下水动力条件呈负相关，地表水入渗补给大、水动力条件强的水流系统地下水平均温度低，入渗补给小、水动力条件弱的地下水平均温度高；浅层地下水温度动态受自然地下水循环和地下水开采等人类活动共同影响，从山前地下水补给区到中游绿洲区再到下游排泄区，浅部地下水温度动态可划分为4种基本类型，依次分别为河流补给型、水温稳定型、开采相关型、正弦波动型。   相似文献   

19.
We investigated the Stokes drift-driven ocean currents and Stokes drift-induced wind energy input into the upper ocean using a two-way coupled wave-current modeling system that consists of the Princeton Ocean Model generalized coordinate system (POMgcs), Simulating WAves Nearshore (SWAN) wave model, and the Model Coupling Toolkit (MCT). The Coriolis-Stokes forcing (CSF) computed using the wave parameters from SWAN was incorporated with the momentum equation of POMgcs as the core coupling process. Experimental results in an idealized setting show that under the steady state, the scale of the speed of CSF-driven current was 0.001 m/s and the maximum reached 0.02 m/s. The Stokes drift-induced energy rate input into the model ocean was estimated to be 28.5 GW, taking 14% of the direct wind energy rate input. Considering the Stokes drift effects, the total mechanical energy rate input was increased by approximately 14%, which highlights the importance of CSF in modulating the upper ocean circulation. The actual run conducted in Taiwan Adjacent Sea (TAS) shows that: 1) CSF-based wave-current coupling has an impact on ocean surface currents, which is related to the activities of monsoon winds; 2) wave-current coupling plays a significant role in a place where strong eddies present and tends to intensify the eddy’s vorticity; 3) wave-current coupling affects the volume transport of the Taiwan Strait (TS) throughflow in a nontrivial degree, 3.75% on average.  相似文献   

20.
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