共查询到20条相似文献，搜索用时 500 毫秒
1.
A multi-envelope generalised coordinate system for numerical ocean modelling is introduced. In this system, computational levels are curved and adjusted to multiple ‘virtual bottoms’ (aka envelopes) rather than following geopotential levels or the actual bathymetry. This allows defining computational levels which are optimised to best represent different physical processes in different sub-domains of the model. In particular, we show how it can be used to improve the representation of tracer advection in the ocean interior. The new vertical system is compared with a widely used z-partial step scheme. The modelling skill of the models is assessed by comparison with the analytical solutions or results produced by a model with a very high-resolution z-level grid. Three idealised process-oriented numerical experiments are carried out. Experiments show that numerical errors produced by the new scheme are much smaller than those produced by the standard z-partial step scheme at a comparable vertical resolution. In particular, the new scheme shows superiority in simulating the formation of a cold intermediate layer in the ocean interior and in representing dense water cascading down a steep topography. 相似文献
2.
Emulation modelling can be an effective alternative to traditional mechanistic approaches for complex environmental systems and, if carefully conceived, can offer significantly reduced run times and user expertise requirements. We present a case study of dynamic emulation for the domain of estuarine water quality modelling, by reporting the development and evaluation of a one-dimensional hydrodynamic model emulator. The proposed “neuroemulator” retains the dynamic nature of the process-based model utilizing a set of artificial neural networks. The underlying hydrodynamic model is routinely used for analysis and management of the northern reach of the San Francisco Bay-Delta estuary, a large complex region of strategic importance for water supply and ecosystem services on the Pacific coast of California, USA. The reduced computational expense of the emulator affords opportunities for direct use, as well as embedded use within other modelling frameworks such as those developed for reservoir operations and socio-hydrology. 相似文献
3.
By modelling the observed distribution of210Pb and210Po in surface waters of the Pacific, residence times relative to particulate removal are determined. For the center of the North Pacific gyre these are τPo = 0.6years andτPb = 1.7years. The surface ocean τPb is determined by particulate transport rather than plankton settling. The fact that it is about two orders of magnitude smaller than τPb for the deep ocean implies a sharp change in the adsorptive quality of particles during descent through the water column. 相似文献
4.
The scale factors to permit a laboratory analogue model study of the problem of magnetic fields induced by ocean waves in the earth's field are derived. An analogue model employing surface fluid waves in mercury to simulate ocean waves is described. In the analogue model, magnetic field measurements were made 1 cm above a 2 cm deep model mercury ocean for a wave period of 0.21 s. This model simulates measurements 38 m above the surface of a shallow ocean 78 m deep for a wave period of 13 s. The validity of the analogue modelling technique is established by the good agreement obtained in comparing the analogue model measurements of the induced magnetic fields with fields using Podney's expression for an ocean of finite depth. 相似文献
5.
Carracedo P Torres-López S Barreiro M Montero P Balseiro CF Penabad E Leitao PC Pérez-Muñuzuri V 《Marine pollution bulletin》2006,53(5-7):350-360
An integrated system named METEOMOHID, developed by MeteoGalicia in the first stage of the Prestige accident in November 2002 was used successfully in an operational form to support decision making and assist in recovering tasks. Afterwards, METEOMOHID has been enhanced with the aim of developing an operational oceanography system to be used in the NW of the Iberian Peninsula. The METEOMOHID system includes local area hydrodynamic coastal ocean modelling (MOHID), real time atmospheric forcing from a local meteorological model (ARPS). Using the available data from the Prestige crisis, a set of simulations were designed in order to reproduce the oil spill drift. The implementation of a detailed vertical resolution in the model has allowed obtaining a detailed surface dynamic, improving our knowledge of the behaviour of tarballs into the water column. Thus, the wind-driven Eckman drift, the direct dragging of the wind were detached, and the possible existence of subsurface oil was assessed. In addition, the present work evaluates the effects of introducing climatologic large scale currents in the METEOMOHID system. 相似文献
6.
Water Resources - A water resource allocation model coupling quantity and quality is a topic of concern in China. The water resources supply modelling is set up according to the water quality, and... 相似文献
7.
Gill M. Martin 《Surveys in Geophysics》2014,35(3):553-575
Despite their obvious environmental, societal and economic importance, our understanding of the causes and magnitude of the variations in the global water cycle is still unsatisfactory. Uncertainties in hydrological predictions from the current generation of models pose a serious challenge to the reliability of forecasts and projections across time and space scales. This paper provides an overview of the current issues and challenges in modelling various aspects of the Earth’s hydrological cycle. These include: the global water budget and water conservation, the role of model resolution and parametrisation of precipitation-generating processes on the representation of the global and regional hydrological cycle, representation of clouds and microphysical processes, rainfall variability, the influence of land–atmosphere coupling on rainfall patterns and their variability, monsoon processes and teleconnections, and ocean and cryosphere modelling. We conclude that continued collaborative activity in the areas of model development across timescales, process studies and climate change studies will provide better understanding of how and why the hydrological cycle may change, and better estimation of uncertainty in model projections of changes in the global water cycle. 相似文献
8.
9.
Mike Herzfeld 《Ocean Dynamics》2009,59(1):21-46
An operational limited-area ocean modelling system was developed to supply forecasts of ocean state out to 3 days. This system
is designed to allow non-specialist users to locate the model domain anywhere within the Australasian region with minimum
user input. The model is required to produce a stable simulation every time it is invoked. This paper outlines the methodology
used to ensure the model remains stable over the wide range of circumstances it might encounter. Central to the model configuration
is an alternative approach to implementing open boundary conditions in a one-way nesting environment. Approximately 170 simulations
were performed on limited areas in the Australasian region to assess the model stability; of these, 130 ran successfully with
a static model parameterisation allowing a statistical estimate of the model’s approach toward instability to be determined.
Based on this, when the model was deemed to be approaching instability a strategy of adaptive intervention in the form of
constraint on velocity and elevation was invoked to maintain stability. 相似文献
10.
针对河流模拟中未知不确定性源对模拟精度的影响,以巢湖流域南淝河为研究对象,建立了基于四维变分同化方法的南淝河干流水质模型,研究了含未知污染源的南淝河水质过程模拟.模型以未知污染负荷的动态变化过程为控制变量,通过同化沿河不同断面的逐日水质监测数据,识别不同河段的逐日入河污染负荷过程来实现水质过程的模拟,改变了常规模型模拟需提前预知并输入污染负荷的应用前提.模拟结果表明,采用四维变分同化方法的水质模拟结果有明显改进,重点河段水质模拟的纳什效率系数从小于0提高到0.5以上.识别的入河污染过程与降雨过程波动总体一致,证实南淝河的入河污染与降雨过程密切;同时,模型也可识别异常的入河负荷,提高模型对水环境问题的诊断分析能力.该方法可推广应用于复杂河流系统,为巢湖等流域污染来源定量解析、水质预测预警及污染管控提供支持. 相似文献
11.
Produced water discharge accounts for the greater portion of wastes arising from offshore oil and gas production operations. Development and expansion of Canada’s offshore oil and gas reserves has led to concerns over the potential long-term impacts of produced water discharges to the ocean. To examine this emerging environmental issue at a regional scale, an integrated risk assessment approach was developed in this study based on the princeton ocean model (POM), a random walk (RW) and Monte Carlo simulation. The use of water quality standards arrayed in a Monte Carlo design in the developed approach has served to reflect uncertainties and quantify environmental risks associated with produced water discharge. The model was validated against field data from a platform operating off Canada’s east coast, demonstrating its usefulness in supporting effective management of future produced water discharge. 相似文献
12.
Paleoreconstructions suggest that during the Last Glacial Maximum (LGM) the North Atlantic circulation was noticeably different from its present state. However, the glacial salt conveyor belt is believed to be similar to the present-day’s conveyor, albeit weaker and shallower because of an increased freshwater flux in high-latitudes. We present here the investigation of the conveyor operation based on ocean circulation modelling using two numerical models in parallel. The GFDL primitive equation model and a planetary geostrophic model are employed to address the problem of the paleocirculation modelling in cases of uncertain and sparse data comprising the glacial surface boundary conditions. The role of different simplifications that may be used in the ocean climate studies, including the role of grid resolution, bottom topography, coast-line, etc., versus glacial-interglacial changes of the ocean surface climatology is considered. The LGM reverse conveyor gyre appeared to be the most noticeable feature of the glacial-to-interglacial alteration of the ocean circulation. The reversed upper-ocean conveyor, weaker and subducting ‘normal’ conveyor in the intermediate depths, and the change of the deep-ocean return flow route are robust signatures of the glacial North Atlantic climate. The results are found to be ‘model-independent’ and fairly insensitive to all factors other than the onset of the glacial surface conditions. 相似文献
13.
In urban drainage modelling, uncertainty analysis is of undoubted necessity. However, uncertainty analysis in urban water-quality modelling is still in its infancy and only few studies have been carried out. Therefore, several methodological aspects still need to be experienced and clarified especially regarding water quality modelling. The use of the Bayesian approach for uncertainty analysis has been stimulated by its rigorous theoretical framework and by the possibility of evaluating the impact of new knowledge on the modelling predictions. Nevertheless, the Bayesian approach relies on some restrictive hypotheses that are not present in less formal methods like the Generalised Likelihood Uncertainty Estimation (GLUE). One crucial point in the application of Bayesian method is the formulation of a likelihood function that is conditioned by the hypotheses made regarding model residuals. Statistical transformations, such as the use of Box–Cox equation, are generally used to ensure the homoscedasticity of residuals. However, this practice may affect the reliability of the analysis leading to a wrong uncertainty estimation. The present paper aims to explore the influence of the Box–Cox equation for environmental water quality models. To this end, five cases were considered one of which was the “real” residuals distributions (i.e. drawn from available data). The analysis was applied to the Nocella experimental catchment (Italy) which is an agricultural and semi-urbanised basin where two sewer systems, two wastewater treatment plants and a river reach were monitored during both dry and wet weather periods. The results show that the uncertainty estimation is greatly affected by residual transformation and a wrong assumption may also affect the evaluation of model uncertainty. The use of less formal methods always provide an overestimation of modelling uncertainty with respect to Bayesian method but such effect is reduced if a wrong assumption is made regarding the residuals distribution. If residuals are not normally distributed, the uncertainty is over-estimated if Box–Cox transformation is not applied or non-calibrated parameter is used. 相似文献
14.
Identifiability analysis enables the quantification of the number of model parameters that can be assessed by calibration with respect to a data set. Such a methodology is based on the appraisal of sensitivity coefficients of the model parameters by means of Monte Carlo runs. By employing the Fisher Information Matrix, the methodology enables one to gain insights with respect to the number of model parameters that can be reliably assessed. The paper presents a study where identifiability analysis is used as a tool for setting up measuring campaigns for integrated water quality modelling. Particularly, by means of the identifiability analysis, the information about the location and the number of the monitoring stations in the integrated system required for assessing a specific group of model parameters were gained. The analysis has been applied to a real, partially urbanised, catchment containing two sewer systems, two wastewater treatment plants and a river. Several scenarios of measuring campaigns have been considered; each scenario was characterised by different monitoring station locations for the gathering of quantity and quality data. The results enabled us to assess the maximum number of model parameters quantifiable for each scenario i.e. for each data set. The methodology resulted to be a powerful tool for designing measuring campaign for integrated water quality modelling. Indeed, the crucial cross sections throughout the integrated wastewater system were detected optimizing both human and economic efforts in the gathering of field data. Further, a connection between the data set and the number of model parameters effectively assessable has been established leading to much more reliable model results. 相似文献
15.
Daniel J. Twigt Erik D. De Goede Firmijn Zijl Dirk Schwanenberg Alex Y. W. Chiu 《Ocean Dynamics》2009,59(6):1077-1093
Within the hydrodynamic modelling community, it is common practice to apply different modelling systems for coastal waters
and river systems. Whereas for coastal waters 3D finite difference or finite element grids are commonly used, river systems
are generally modelled using 1D networks. Each of these systems is tailored towards specific applications. Three-dimensional
coastal water models are designed to model the horizontal and vertical variability in coastal waters and are less well suited
for representing the complex geometry and cross-sectional areas of river networks. On the other hand, 1D river network models
are designed to accurately represent complex river network geometries and complex structures like weirs, barrages and dams.
A disadvantage, however, is that they are unable to resolve complex spatial flow variability. In real life, however, coastal
oceans and rivers interact. In deltaic estuaries, both tidal intrusion of seawater into the upstream river network and river
discharge into open waters play a role. This is frequently approached by modelling the systems independently, with off-line
coupling of the lateral boundary forcing. This implies that the river and the coastal model run sequentially, providing lateral
discharge (1D) and water level (3D) forcing to each other without the possibility of direct feedback or interaction between
these processes. An additional disadvantage is that due to the time aggregation usually applied to exchanged quantities, mass
conservation is difficult to ensure. In this paper, we propose an approach that couples a 3D hydrodynamic modelling system
for coastal waters (Delft3D) with a 1D modelling system for river hydraulics (SOBEK) online. This implies that contrary to
off-line coupling, the hydrodynamic quantities are exchanged between the 1D and 3D domains during runtime to resolve the real-time
exchange and interaction between the coastal waters and river network. This allows for accurate and mass conserving modelling
of complex coastal waters and river network systems, whilst the advantages of both systems are maintained and used in an optimal
and computationally efficient way. The coupled 1D–3D system is used to model the flows in the Pearl River Delta (Guangdong,
China), which are determined by the interaction of the upstream network of the Pearl River and the open waters of the South
China Sea. The highly complex upstream river network is modelled in 1D, simulating river discharges for the dry and wet monsoon
periods. The 3D coastal model simulates the flow due to the external (ocean) periodic tidal forcing, the salinity distribution
for both dry and wet seasons, as well as residual water levels (sea level anomalies) originating from the South China Sea.
The model is calibrated and its performance extensively assessed against field measurements, resulting in a mean root mean
square (RMS) error of below 6% for water levels over the entire Pearl River Delta. The model also represents both the discharge
distribution over the river network and salinity transport processes with good accuracy, resolving the discharge distribution
over the main branches of the river network within 5% of reported annual mean values and RMS errors for salinity in the range
of 2 ppt (dry season) to 5 ppt (wet season). 相似文献
16.
M. van Der Perk 《水文研究》1998,12(5):683-699
A method that combines calibration and identifiability analysis of a dynamic water quality model to evaluate the relative importance of various processes affecting the dynamic aspects of water composition is illustrated by a study of the response of suspended sediment and dissolved nutrients to a flood hydrograph in a rural catchment area in the Netherlands. Since the water quality model simulates the observed concentrations of suspended sediment and dissolved nutrients reasonably well, the most important processes during the observed flood hydrograph could be determined. These were erosion, exchange between dissolved phase and bed sediments and denitrification. It is concluded that the method is very useful for identifying the most significant model parameters and processes that are essential for water quality modelling. © 1998 John Wiley & Sons, Ltd. 相似文献
17.
M.G. Hutchins R.J. Williams C. Prudhomme M.J. Bowes H.E. Brown A.J. Waylett 《水文科学杂志》2013,58(16):2818-2833
ABSTRACTA modelling study was undertaken to quantify effects that the climate likely to prevail in the 2050s might have on water quality in two contrasting UK rivers. In so doing, it pinpointed the extent to which time series of climate model output, for some variables derived following bias correction, are fit for purpose when used as a basis for projecting future water quality. Working at daily time step, the method involved linking regional climate model (HadRM3-PPE) projections, Future Flows Hydrology (rainfall–runoff modelling) and the QUESTOR river network water quality model. In the River Thames, the number of days when temperature, dissolved oxygen, biochemical oxygen demand and phytoplankton exceeded undesirable values (>25°C, <6 mg L?1, >4 mg L?1 and >0.03 mg L?1, respectively) was estimated to increase by 4.1–26.7 days per year. The changes do not reflect impacts of any possible change in land use or land management. In the River Ure, smaller increases in occurrence of undesirable water quality are likely to occur in the future (by 1.0–11.5 days per year) and some scenarios suggested no change. Results from 11 scenarios of the hydroclimatic inputs revealed considerable uncertainty around the levels of change, which prompted analysis of the sensitivity of the QUESTOR model to simulations of current climate and hydrology. Hydrological model errors were deemed of less significance than those associated with the derivation and downscaling of driving climatic variables (rainfall, air temperature and solar radiation). Errors associated with incomplete understanding of river water quality interactions with the aquatic ecosystem were found likely to be more substantial than those associated with hydrology, but less than those related to climate model inputs. These errors are largely a manifestation of uncertainty concerning the extent to which phytoplankton biomass is controlled by invertebrate grazers, particularly in mid-summer; and the degree to which this varies from year to year. The quality of data from climate models for generating flows and defining driving variables at the extremes of their distributions has been highlighted as the major source of uncertainty in water quality model outputs.
EDITOR A. Castellarin; ASSOCIATE EDITOR X. Fang 相似文献
18.
在地球物理问题中,有两种方法通常用于解释地磁和地电异常,这就是数字模型技术和实验室模拟模型法。实验室模拟模型对于分析不易求得数学解的问题非常有用,并且已经广泛用于研究复杂的地球物理问题。本文评述了国外特别是加拿大开展模拟模型研究的情况;描述了平面波、线电流、磁偶极等各种类型的场源模型;给出了该法在研究海岸效应、岛陆通道电流、海浪电磁效应和各向异性导体等方面的应用。模拟模型测量和数字计算的比较结果显示了非常好的一致性,这就进一步证实了模拟模型法对于研究复杂二维和三维感应问题的可靠性。该项研究工作对于了解天然电磁场源的性质、进行地球物理勘探以及研究地球地壳和地幔的电性结构都十分有益。 相似文献
19.
Predicting seasonal and hydro-meteorological impact in environmental variables modelling via Kalman filtering 总被引：1，自引：1，他引：0
A. Manuela Gonçalves Marco Costa 《Stochastic Environmental Research and Risk Assessment (SERRA)》2013,27(5):1021-1038
This study focuses on the potential improvement of environmental variables modelling by using linear state-space models, as an improvement of the linear regression model, and by incorporating a constructed hydro-meteorological covariate. The Kalman filter predictors allow to obtain accurate predictions of calibration factors for both seasonal and hydro-meteorological components. This methodology can be used to analyze the water quality behaviour by minimizing the effect of the hydrological conditions. This idea is illustrated based on a rather extended data set relative to the River Ave basin (Portugal) that consists mainly of monthly measurements of dissolved oxygen concentration in a network of water quality monitoring sites. The hydro-meteorological factor is constructed for each monitoring site based on monthly precipitation estimates obtained by means of a rain gauge network associated with stochastic interpolation (kriging). A linear state-space model is fitted for each homogeneous group (obtained by clustering techniques) of water monitoring sites. The adjustment of linear state-space models is performed by using distribution-free estimators developed in a separate section. 相似文献
20.
A numerical model of the Atlantic Ocean was used to study the low-frequency variability of meridional transports in the North Atlantic. The model shows a behaviour similar to those used in previous studies, and the temporal variability of certain variables compares favourably to observed time series. By changing the depth and width of the sills between the subpolar North Atlantic and the Nordic Seas, the mean horizontal and overturning circulation as well as some water mass properties are modified significantly. The reaction of meridional oceanic transports to atmospheric forcing fluctuations remains, however, unchanged. The critical role of the surface heat flux retroaction term for the meridional heat transport in stand-alone ocean models is discussed. The experiments underline the role of atmospheric variability for fluctuations of the large-scale ocean circulation on time scales from years to decades, and they support the hypothesis that the mean overturning strength is controlled by the model representation of the density of the overflow water masses.Responsible Editor: Dirk Olbers 相似文献