Numerical Modeling System Research Articles

Characterizing the severe turbulence environments associated with commercial aviation accidents. A real-time turbulence model (RTTM) designed for the operational prediction of hazardous aviation turbulence environments

In this paper, we will focus on the real-time prediction of environments that are predisposed to producing moderate-severe (hazardous) aviation turbulence. We will describe the numerical model and its postprocessing system that is designed for said prediction of environments predisposed to severe aviation turbulence as well as presenting numerous examples of its utility. The purpose of this paper is to demonstrate that simple hydrostatic precursor circulations organize regions of preferred wave breaking and turbulence at the nonhydrostatic scales of motion. This will be demonstrated with a hydrostatic numerical modeling system, which can be run in real time on a very inexpensive university computer workstation employing simple forecast indices. The forecast system is designed to efficiently support forecasters who are directing research aircraft to measure the environment immediately surrounding turbulence. The numerical model is MASS version 5.13, which is integrated over three different grid matrices in real-time on a university workstation in support of NASA-Langley’s B-757 turbulence research flight missions. The model horizontal resolutions are 60, 30, and 15 km and the grids are centered over the region of operational NASA-Langley B-757 turbulence flight missions. The postprocessing system includes several turbulence-related products including four turbulence forecasting indices, winds, streamlines, turbulence kinetic energy, and Richardson numbers. Additionally there are convective products including precipitation, cloud height, cloud mass fluxes, lifted index, and K-index. Furthermore, soundings, sounding parameters, and Froude number plots are also provided. The horizontal cross section plot products are provided from 16,000–46,000 feet in 2,000 feet intervals. Products are available every three hours at the 60 and 30 km grid interval and every 1.5 hours at the 15 km grid interval. The model is initialized from the NWS ETA analyses and integrated two times a day.

Development and validation of tools for the implementation of european air quality policy in Germany (Project VALIUM)

Abstract. In the framework of the German Atmospheric Research Program AFO-2000 a system of consistent coupled numerical models has been developed. The purpose of the model system is to serve as a tool for the execution of European urban air quality regulations. A consortium with the acronym VALIUM was formed, which consisted of German research institutes, environmental consultancies and an environmental agency. A substantial part of the VALIUM program was devoted to the generation of a set of high quality data for the validation of the numerical model system. The validation data are based on a combination of field studies, tracer experiments and corresponding wind tunnel experiments. The field experiments were carried out inside and around a street canyon in a city district of Hanover/Germany. After a brief introduction to the VALIUM project a summary of the main results will be given.

Modeling studies of the upper ocean response to a tropical cyclone

A coupled ocean and boundary layer flux numerical modeling system is used to study the upper ocean response to surface heat and momentum fluxes associated with a major hurricane, namely, Hurricane Dennis (July 2005) in the Gulf of Mexico. A suite of experiments is run using this modeling system, constructed by coupling a Navy Coastal Ocean Model simulation of the Gulf of Mexico to an atmospheric flux model. The modeling system is forced by wind fields produced from satellite scatterometer and atmospheric model wind data, and by numerical weather prediction air temperature data. The experiments are initialized from a data assimilative hindcast model run and then forced by surface fluxes with no assimilation for the time during which Hurricane Dennis impacted the region. Four experiments are run to aid in the analysis: one is forced by heat and momentum fluxes, one by only momentum fluxes, one by only heat fluxes, and one with no surface forcing. An equation describing the change in the upper ocean hurricane heat potential due to the storm is developed. Analysis of the model results show that surface heat fluxes are primarily responsible for widespread reduction (0.5°–1.5°C) of sea surface temperature over the inner West Florida Shelf 100–300 km away from the storm center. Momentum fluxes are responsible for stronger surface cooling (2°C) near the center of the storm. The upper ocean heat loss near the storm center of more than 200 MJ/m2 is primarily due to the vertical flux of thermal energy between the surface layer and deep ocean. Heat loss to the atmosphere during the storm’s passage is approximately 100–150 MJ/m2. The upper ocean cooling is enhanced where the preexisting mixed layer is shallow, e.g., within a cyclonic circulation feature, although the heat flux to the atmosphere in these locations is markedly reduced.

National Emissions Ceilings For 2005 And 2010And Their Impact On Portuguese Air Quality

Accordingly to the EU Directive 2001/81/EC, all the Member States should develop and implement a national programme to reduce the emissions of acidifying gases, in order to reach, before 2010, the National Emission Ceilings (NEC). In this context, Portugal has developed technical studies aiming to set up a reference scenario until 2010 and to evaluate the compliance of the emission ceilings established to this target year. In addition to this reference scenario, high and low emission reduction scenarios were also defined. Notwithstanding 2010 scenarios, the same procedure was applied to 2005 and two reduction scenarios, high and low, were considered. This works intends to evaluate the impacts of these national emission reduction scenarios on the air quality in Portugal, verifying the fulfilment of the air quality thresholds for 2005 and 2010. A numerical modelling system was applied over Portugal to these hypothetical situations and results were compared to those from an application to a baseline year 2001. The selected numerical system is the 3D chemistry-transport model CHIMERE, which uses data from the European Centre for Medium Range Weather Forecast as meteorological input. Assuming the 2001 simulated meteorological conditions, the results point towards a reasonable improvement of the air quality over Portugal. It forecasted a significant decrease of ozone levels, especially in the downwind urban areas of Lisbon and Porto. These results strengthen the importance of including the NEC emission scenarios into the national strategy for air quality management.

Computer Simulation and Validation of the Archimedes Lever Hypothesis as a Mechanism for Aortic Isthmus Disruption in a Case of Lateral Impact Motor Vehicle Crash: A Crash Injury Research Engineering Network (CIREN) Study

Can aortic isthmus disruption occurring in a lateral motor vehicle crash (LMVC) be explained by the Archimedes Lever Hypothesis, where the intrathoracic aorta, super-pressurized by the thoracic impact force, functions as a rigid lever system? The long arm of this lever system is the proximal aorta-aortic arch, the short arm is the aortic isthmus fixed distally at the descending aorta, and the fulcrum is at the great vessels, especially the left subclavian artery. The theory was tested by a simulation technique using a computer-based finite element numerical model system. This simulation model included the dynamics of the crashed vehicles, the direction of force impact, and the structure of the thorax and intrathoracic viscera, including the entire intrathoracic aorta. The specific patient whose data were entered into the model was chosen from a study of 34 LMCV aortic injuries (AIs). The model was constrained by patient and vehicle data from this surviving case. Three sequential lateral thoracic levels impacted by the vehicle side structures were selected. At each level, the maximum mean intra-aortic pressure was 50 to 100 ms after impact, the structure dynamics of the actual crash and the resultant vehicle deformation were simulated; only when the lateral impact was induced in a transverse plane including the first 4 ribs at the level of the aortic arch/isthmus system, with intra-aortic pressures from 200 to 500 mm Hg, were AI-compatible stresses and deformations in the aortic wall achieved at the isthmus. In LMVC AI, the simulation suggests that the aorta functions as an Archimedes Lever System in which the magnified force mediated by the long lever arm produces sufficient strain on the short lever arm to rupture the aorta at the isthmus.

An integrated numerical and physical modeling system for an enhanced in situ bioremediation process

Groundwater contamination due to releases of petroleum products is a major environmental concern in many urban districts and industrial zones. Over the past years, a few studies were undertaken to address in situ bioremediation processes coupled with contaminant transport in two- or three-dimensional domains. However, they were concentrated on natural attenuation processes for petroleum contaminants or enhanced in situ bioremediation processes in laboratory columns. In this study, an integrated numerical and physical modeling system is developed for simulating an enhanced in situ biodegradation (EISB) process coupled with three-dimensional multiphase multicomponent flow and transport simulation in a multi-dimensional pilot-scale physical model. The designed pilot-scale physical model is effective in tackling natural attenuation and EISB processes for site remediation. The simulation results demonstrate that the developed system is effective in modeling the EISB process, and can thus be used for investigating the effects of various uncertainties.

A review on integration of artificial intelligence into water quality modelling

With the development of computing technology, numerical models are often employed to simulate flow and water quality processes in coastal environments. However, the emphasis has conventionally been placed on algorithmic procedures to solve specific problems. These numerical models, being insufficiently user-friendly, lack knowledge transfers in model interpretation. This results in significant constraints on model uses and large gaps between model developers and practitioners. It is a difficult task for novice application users to select an appropriate numerical model. It is desirable to incorporate the existing heuristic knowledge about model manipulation and to furnish intelligent manipulation of calibration parameters. The advancement in artificial intelligence (AI) during the past decade rendered it possible to integrate the technologies into numerical modelling systems in order to bridge the gaps. The objective of this paper is to review the current state-of-the-art of the integration of AI into water quality modelling. Algorithms and methods studied include knowledge-based system, genetic algorithm, artificial neural network, and fuzzy inference system. These techniques can contribute to the integrated model in different aspects and may not be mutually exclusive to one another. Some future directions for further development and their potentials are explored and presented.

A review on the integration of artificial intelligence into coastal modeling

With the development of computing technology, mechanistic models are often employed to simulate processes in coastal environments. However, these predictive tools are inevitably highly specialized, involving certain assumptions and/or limitations, and can be manipulated only by experienced engineers who have a thorough understanding of the underlying theories. This results in significant constraints on their manipulation as well as large gaps in understanding and expectations between the developers and practitioners of a model. The recent advancements in artificial intelligence (AI) technologies are making it possible to integrate machine learning capabilities into numerical modeling systems in order to bridge the gaps and lessen the demands on human experts. The objective of this paper is to review the state-of-the-art in the integration of different AI technologies into coastal modeling. The algorithms and methods studied include knowledge-based systems, genetic algorithms, artificial neural networks, and fuzzy inference systems. More focus is given to knowledge-based systems, which have apparent advantages over the others in allowing more transparent transfers of knowledge in the use of models and in furnishing the intelligent manipulation of calibration parameters. Of course, the other AI methods also have their individual contributions towards accurate and reliable predictions of coastal processes. The integrated model might be very powerful, since the advantages of each technique can be combined.

Comparison of two three-dimensional hydrodynamic modeling systems for coastal tidal motion

A comparison of two three-dimensional numerical modeling systems for tidal elevations and velocities in the coastal waters is presented. The two modeling systems are: (1) the Princeton Ocean Model (POM) and (2) the MIKE 3 flow model. The model performance results for Singapore's coastal waters show that the predicted tidal elevations from the two hydrodynamic modeling systems are almost identical and are in very good agreement with field measurement data. The simulated tidal current velocities match well with field measurement data at the selected stations, but it seems that the POM provides the slightly better simulation, compared to the MIKE 3 flow model. The depth profiles of the velocities obtained from the two modeling systems may be greatly different at some time, due to the vertical diffusion coefficient calculated from different turbulent sub-models in the two modeling systems. The POM generally predicts larger peak tidal velocities. The maximum speed differences for the model results from the two modeling systems occur in the top and differ from time to time and from location to location, reaching up to 20%.

Research and application on the technology system of multi-scale assessment of the impact on the atmospheric environment by urban planning

Improvement of the atmospheric environment in urban planning is an important issue to implement the sustainable development of cities. In this paper, in order to meet the demand of planning office to compare and assess quantitatively of the designs in multi-scale, based on geographical information system (GIS) data with high resolution, a multi-scale numerical modeling system for the atmospheric environment impact of urban planning is set up, and the multi-scale assessment index system is established, which compose the technology system of multi-scale assessment of the impact on the atmospheric environment by urban planning. In urban planning (urban development of Beijing) and optimizing layouts of Olympic Green, it has been applied to quantitatively evaluating the impact on atmospheric environment by urban planning before construction, which offers scientific foundation to optimize the whole and local urban layout.

Sediment Properties in the Western Baltic Sea for Use in Sediment Transport Modelling

BOBERTZ, B.; KUHRTS, C.; HARFF, J.; FENNEL, W.; SEIFERT, T., and BOHLING, B., 2005. Sediment properties in the western Baltic Sea for the use in sediment transport modelling. Journal of Coastal Research, 21(3), 588‐597. West Palm Beach (Florida), ISSN 0749-0208. To simulate transport of clastic material in the Baltic a sediment transport module is linked to a Baltic Sea Model that is based on the Modular Ocean Model—MOM3. In order to describe the properties of the seabed sediment parameters as mean grain size, critical shear velocity and bed roughness length must be provided as input data to the numerical model system. To obtain maps of these quantities for the Baltic Sea area the proxy-target concept is applied. As proxy-variable the mean grain size of the sediment types is used. For different sediment samples the critical shear velocity was measured and serves as the target variable. Using the relation between the sediment classifications based on the mean grain size (proxy) and the measured critical shear velocity (target) a map of the critical shear velocity in the Baltic is derived. In January 1993 several extreme strong storm events occurred in the Baltic. Using this period for a model calculation maximum values of current and wave induced bottom shear velocities were obtained. Comparing these model results with the critical shear velocity distribution provided by the proxy-target concept we identify potential erosion areas. Further we show the transport path of material initially deposited in the Mecklenburgian Bight.

DERIVED RELEASE LIMITS FOR THE GREEK RESEARCH REACTOR SITE BASED ON A DIAGNOSTIC ATMOSPHERIC MODELING SYSTEM FOR IRREGULAR TERRAIN

The upper limits for the rate of release of radionuclides into the atmosphere, i.e., the "derived release limits," are calculated for the Greek Research Reactor (GRR-1) in order to determine possible operational schemes compatible with the effective dose limits for the general population. GRR-1 is located at the northwestern foot of Hymettos Mountain and at the eastern border of the urbanized area of Athens basin. Due to the topographic complexity of the region, the meteorological and atmospheric dispersion calculations were based on a numerical modeling system that is especially designed to work over irregular terrains by using a prismatic unstructured grid. The calculation of derived release limits was made using guidelines and methods that conform to the system of dose limits prescribed by the European radiation protection regulations.

Air pollution forecast in Portugal: a demand from the new air quality framework directive

This work aims at developing and validating a numerical air quality operational forecasting system that will be applied over Portugal. The CHIMERE model was chosen for the chemistry-transport simulation using the meteorological parameters supplied by the MM5 mesoscale meteorological model, forced by the AVN/NCEP global forecasts. An experiment of 48-hour real-time forecast simulations was performed, on a daily basis, during the four summer months of 2003. The numerical model system is then evaluated against hourly time series of basic meteorological variables and of ozone and NO2 concentrations, collected in several Portuguese monitoring stations included in meteorological and air quality network. Statistical skill scores are discussed and compared with previous studies. The results point this developed model system as a useful tool that can be used and implemented to anticipate pollution episodes, to local and regional air quality management and for population information purpose.

A hybrid numerical model system of LCO 2 and CO 2 enriched seawater dynamics in the ocean induced by moving-ship releasing

A numerical modeling system has been developed, based on an engineering background, of the direct disposal of liquid carbon dioxide into the ocean by a moving-ship, to predict the physico–chemical dynamics of liquid carbon dioxide droplets and carbon dioxide enriched seawater in the ocean. This is a hybrid simulation model system consisting of a three-dimensional small-scale near-field model and a two-dimensional horizontal turbulent dispersion model. The dynamics near to release sites include double-plume creation, interaction, evolution, and coupling with ocean currents; these are described by using two-fluid large-eddy simulation technology. The further development of carbon dioxide enriched seawater, as a passive-inert scalar, in relatively larger spatial and time scales (28×28 km and up to 100 h) is then simulated by a horizontal turbulent dispersion model. For the case of liquid carbon dioxide release at a depth of 2000 m with mass flow rate of 100 kg/s and initial droplet diameter of 8.0 mm, and with ship speed of 3.0 m/s, the model predicts a vertically separated carbon dioxide enriched seawater plume, 330 m in height and 40 m in width at time about 1 h after release with a minimum pH of 6.20 corresponding to carbon dioxide concentration of 0.18 kg/m 3, in the surrounding area. This carbon dioxide enriched seawater plume diffused turbulently in the horizontal surface to an area of 9.8×10.5 km 2 after 100 h.

A Numerical Daily Air Quality Forecast System for The Pacific Northwest

A real-time photochemical air quality forecast system has been implemented for the Puget Sound region to support public awareness of air quality issues. The Air Indicator Report for Public Access and Community Tracking (AIRPACT) forecast system uses daily numerical weather forecasts from the fifth-generation Pennsylvania State University (PSU)–National Center for Atmospheric Research (NCAR) Mesoscale Model (MM5) to drive the California Meteorological Model (CALMET)/California photochemistry grid model (CALGRID) Eulerian photochemical modeling suite. Hourly forecasts of ozone and other pollutant concentrations, including primary particulate emissions from diesel sources, are produced for urban Seattle and environs within a gridded domain consisting of 62 × 67 grid cells (4 km × 4 km) with 13 vertical layers. Detailed gridded emission inventories are adjusted dynamically for time of day, day of the week, month, and gridded ambient temperatures to generate requisite emissions. The forecast system also uses hourly pollutant observation data, reported daily, to perform automated evaluations of forecast accuracy. Forecasts and verification results are provided on a daily basis via the Web (see www.airpact.wsu.edu). This paper describes the forecast system and presents preliminary forecast evaluation results from the Pacific Northwest 2001 (PNW2001) field program and from selected months using the routine monitoring network. AIRPACT is unique nationally as the sole numerical modeling system producing daily, year-round, high-resolution regional air quality forecasts with daily verification.

Evaluation of coastal area modelling systems at an estuary mouth

Most numerical models are run and compared to data in a subjective manner. This paper demonstrates how model performance statistics can be used to calibrate and/or validate hydrodynamic models in a more objective way. Statistics were also used to compare model runs that used different amounts of field data in order to inform the debate about the optimum mix of modelling and measurement. The hydrodynamics around the mouth of the Teign estuary (UK) have been simulated using two coastal area numerical modelling systems. Model performance statistics were calculated to assess the accuracy of the predictions of the measured currents at a number of locations around the estuary mouth. The relative mean absolute error was used as it is applicable to vectors as well as scalars and measures all types of errors. An adjusted relative mean absolute error was also used to reduce the effect of measurement error. A classification table was adopted that categorises the results according to the size of the error. In addition, time series and scatter plots were used to judge the performance of the modelling systems. Calm conditions during a spring tide were simulated, as was a relatively large storm. The two modelling systems gave more or less equal performances when run in engineering mode (where default values were used for most of the system settings). In each case, one modelling system performed better than the other at some locations and worse than it at other locations. One model was also run using a scientific approach, where different amounts of information were used to alter the model settings and sensitivity tests were performed. The model performance statistics showed that using more data does not necessarily lead to better model predictions. New methods for incorporating data into the operation of a model need to be evaluated thoroughly before they can be used without site-specific calibration.

The multi-scale numerical modeling system for research on the relationship between urban planning and meteorological environment

Considering the urban characteristics, a customized multi-scale numerical modeling system is established to simulate the urban meteorological environment. The system mainly involves three spatial scales: the urban scale, urban sub-domain scale, and single to few buildings scale. In it, different underlying surface types are employed, the building drag factor is used to replace its roughness in the influence on the urban wind field, the effects of building distribution, azimuth and screening of shortwave radiation are added, and the influence of anthropogenic heating is also taken into account. All the numerical tests indicate that the simulated results are reasonably in agreement with the observational data, so the system can be used to simulate the urban meteorological environment. Making use of it, the characteristics of the meteorological environment from the urban to urban sub-domain scales, even the among-buildings scale, can be recognized. As long as the urban planning scheme is given, the corresponding simulated results can be obtained so as to meet the need of optimizing urban planning.

An Elle-based 2-D model for cation exchange reaction between garnet and biotite

We have developed a model for diffusion zoning development in garnet employing a numerical modeling system, Elle [Jessell et al. 2001]. The Elle system simulates textural development at thin section scale with an assumption that long term textural changes can be achieved by adding incremental processes. Many numerical models have been developed for the diffusion zoning pattern of garnet, but these models considered only lattice diffusion without allowing grain boundary diffusion. However, our model simulates the diffusion zoning in garnets by considering not only lattice diffusion but also grain boundary/lattice reaction and grain boundary diffusion. Sub-processes for our garnet-biotite system include (1) lattice diffusion, (2) grain-boundary diffusion, and (3) grain boundary/lattice reaction. The finite difference explicit method was used for the numerical calculation of lattice and boundary diffusion. For diffusion calculation, chemical concentrations of individual nodal points are used to calculate the amount of transported cations with diffusion coefficients determined from experiments. For lattice/boundary reaction, the lowest energy compositions of garnet and biotite were calculated using the distribution coefficient. Experimental runs were performed to test the consistency and reproducibility of the results. The results demonstrate the consistency and reproducibility, but show somewhat different zoning from that of Spear (1991), due to reduced dimension (3D in nature vs 2D in our model) and the arbitrarily chosen reaction constant. In spite of these limitations, we feel that the model presented here is at least a good starting point for diffusive mass transfer in a material with grain boundary structure. Journal of the Virtual Explorer, 2004 Volume 15 Paper 6 http://virtualexplorer.com.au/ An Elle-based 2-D model for cation exchange reaction between garnet and biotite Page 2 Journal of the Virtual Explorer, 2004 Volume 15 Paper 6 http://virtualexplorer.com.au/ An Elle-based 2-D model for cation exchange reaction between garnet and biotite Page 3

Effects of breaking-induced currents on refraction–diffraction of irregular waves over submerged shoal

To investigate the accuracy degeneration of conventional wave models for the case of breaking waves over a shoal, a system of numerical models is constructed by combining wave and flow models. The wave model employs the parabolic equation considering wave and current interaction. The flow model employs the shallow water equations including radiation stresses of waves. Numerical tests show that the breaking waves induce jet-like strong currents behind the shoal, and the currents, in turn, defocus the waves. As a result, the calculated wave height distribution agrees much closer to the measured data than that obtained using conventional wave models. Thus the effect of breaking-induced currents on the refraction–diffraction of waves over a shoal is clearly understood.

A numerical simulation of dust storms in China

Wind erosion occurs in many arid, semiarid and agricultural areas of the world. The desert areas of China, which occupy approximately 13% of China’s total surface area, are major sources of Asian dust. The major wind-erosion areas are the sandy lands in western and northwestern China together with the extensive regions of the Gobi desert in northern and northeastern China, especially along the basin of the Yellow River. In this paper, dust storms which occurred in China in the spring of 2002 were simulated using an integrated numerical modeling system. The purpose of the simulation is to produce quantitative predictions of wind erosion on regional scales. The integrated wind erosion modeling system used in this study coupled the following three major components: (1) An atmospheric prediction model, together with a land-surface model; (2) a wind-erosion model and (3) a geographic information database. The atmospheric model provides the necessary input data for the wind erosion scheme, including wind speed and precipitation. It also provides input data for the land-surface model that produces predictions for soil moisture. Dust transport and deposition are also considered in the atmospheric model. The wind-erosion model predicts streamwise saltation and dust emission rate for given atmospheric, soil and land surface conditions. The geographic information database provides spatially distributed parameters, such as soil type and vegetation coverage, for the atmospheric, land surface and wind erosion models. Dust storms in China occur mainly in spring and winter, but most frequently in April. In spring, surface soils frozen in the previous winter become especially loose, creating a favorable condition for wind erosion. As an example, the severe dust storms of 15–20 March were simulated. The results show the integrated modeling system can simulate the main characteristics of the dust storms. The system produced estimates of wind erosion intensity and patterns that are in agreement with observations. Such a system offers the possibility of determining wind erosion patterns on broad scales with high spatial resolution, as well as dust transport and deposition.