Cyclone Model Research Articles

Research in Modeling and Simulation for Improving Construction Engineering Operations

Construction simulation, a fast-growing field, is the science of developing and experimenting with computer-based representations of construction systems to understand their underlying behavior. This paper provides a history of construction simulation theory, explores the CYCLONE modeling methodology and its major subsequent developments, examines the development of the Simphony.NET and COSYE modeling environments and their functionality as more generic simulation platforms, and reviews effective strategies for applying simulation in construction. A construction simulation case study is presented that illustrates one successful approach for adopting simulation technology in the industry and outlines the benefits to industry of integrating these technologies. The paper provides an overview of long-term simulation initiatives leading to the next generation of computer modeling systems for construction, where simulation plays an integral role in a futuristic vision of automated project planning and control.

Return period estimates of extreme sea level along the east coast of India from numerical simulations

Estimates of return periods of extreme sea level events along the coast are useful for impact assessment. In this study, a vertically integrated 2D model was developed for the simulation of storm surges in the Bay of Bengal. The bathymetry for the model was derived from an improved ETOPO-5 data set, which was prepared in our earlier work. The meteorological forcing for the model was obtained from the cyclone model of Holland using the data available for 136 low-pressure systems that occurred during 1974–2000 in the Bay of Bengal. The simulated total sea level and the surge component were obtained for each event. The simulated peak levels showed good agreement with the observations available at few stations. The annual maxima of sea levels, extracted from the simulations, were fitted with Gumbel distribution using r-largest annual maxima method to estimate the 5- and 50-year return periods of extreme events at 26 stations along the east coast of India. The return periods estimated from simulated sea levels showed good agreement with those obtained from observations. The 5- and 50-year return levels of total sea level along the east coast of India show a considerable increase from south to north, with the 50-year return total sea levels being as high as 6.9 and 8.7 m at stations along the north eastern coast such as Sagar Island and Chandipur, respectively. The high return levels are expected at these stations as the cyclones developed in the Bay of Bengal generally move north or north-west, producing extreme events in the northern part, and moreover, these stations are characterized by high tidal ranges. However, at some regions in the southern part such as Surya Lanka and Machilipatnam, though 50-year return levels of total sea level are not very high (2.98 and 2.97 m, respectively) because of the relatively lower tidal ranges, high return levels of surges (0.84 and 0.57 m, respectively) are found. In addition to the role of shallow depths (5.0 and 6.1 m, respectively) at the two stations, the high return levels of surges are attributed to the effect of geometrical configuration at Surya Lanka and width (100 km) and orientation of continental shelf at Machilipatnam.

Occluded Fronts and the Occlusion Process: A Fresh Look at Conventional Wisdom

Traditionally, the formation of an occluded front during the occlusion process in extratropical cyclones has been viewed as the catch-up of a faster-moving cold front to a slower-moving warm front separating the warm-sector air from the low center, as first described in the Norwegian cyclone model over 90 yr ago. In this article, the conventional wisdom, or the commonly held beliefs originating from the Norwegian cyclone model, about occluded fronts and the occlusion process are critically examined. The following four tenets of this conventional wisdom are addressed. First, the occlusion process is better described not by catch-up, but by the wrapping up and lengthening of the warm-air tongue as a result of deformation and rotation around the low center. Second, the merger of the cold front and warm front does not result in the frontal zone with the warmer air ascending over the other frontal zone. Instead, the occluded frontal zone tilts over the more statically stable frontal zone. Because a warmfrontal zone tends to be more stable than a cold-frontal zone, this process usually produces a warm-type occlusion, confirming that cold-type occlusions are less common than warm-type occlusions. Third, occlusion does not mean that the cyclone has stopped deepening, because many cyclones continue to deepen 10–30 mb for 12–36 h after the formation of the occluded front. Fourth, clouds and precipitation associated with occluded fronts differ from their widespread stratiform depiction in textbooks. Embedded precipitation bands may be parallel to the front, and little relationship may exist between the fronts and the cloud mass. These four tenets help to explain anomalies in the Norwegian cyclone model, such as how occluded fronts that spiral around the low center do not require catch-up to form, how Shapiro–Keyser cyclones undergo occlusion, why some cyclones do not form occluded fronts, how some cyclones deepen after occlusion, why few cold-type occlusions have been observed, and why occluded cyclones are often associated with heavy precipitation. This reexamination of conventional wisdom leads to a new paradigm for occluded fronts and occluded cyclones. A supplement to this article is available online: DOI: 10.1175/2010BAMS3057.2

Balanced Contribution to the Intensification of a Tropical Cyclone Simulated in TCM4: Outer-Core Spinup Process*

Abstract The balanced contribution to the intensification of a tropical cyclone simulated in the three-dimensional, nonhydrostatic, full-physics tropical cyclone model version 4 (TCM4), in particular the spinup of the outer-core circulation, is investigated by solving the Sawyer–Eliassen equation and by computing terms in the azimuthal-mean tangential wind tendency equation. Results demonstrate that the azimuthal-mean secondary circulation (radial and vertical circulation) and the spinup of the midtropospheric outer-core circulation in the simulated tropical cyclone are well captured by balance dynamics. The midtropospheric inflow develops in response to diabatic heating in mid–upper-tropospheric stratiform (anvil) clouds outside the eyewall in active spiral rainbands and transports absolute angular momentum inward to spin up the outer-core circulation. Although the azimuthal-mean diabatic heating rate in the eyewall is the largest, its contribution to radial winds and thus the spinup of outer-core circulation in the middle troposphere is rather weak. This is because the high inertial stability in the inner-core region resists the radial inflow in the middle troposphere, limiting the inward transport of absolute angular momentum. The result thus suggests that diabatic heating in spiral rainbands is the key to the continued growth of the storm-scale circulation.

Study of the Pressure Drop and Flow Field in Standard Gas Cyclone Models Using the Granular Model

A particle‐laden flow inside solid gas cyclones has been studied using computational fluid dynamics (CFD). The effects of high temperatures and different particle loadings have been investigated. The Reynolds stress (RSM) model‐predicted results, in the case of pure gas, are within engineering accuracy even at high temperatures. Using the granular mixture model for the cases of particle‐laden flow, discrepancies occurred at relatively high loadings (up to 0.5 kg/m3). Since the pressure drop is strongly related to the friction inside the cyclone body, the concept of entropy generation has been employed to detect regions of high frictional effects. Friction has been observed to be important at the vortex finder wall, the bottom of the conical‐part wall, and the interface separating the outer and the core streams. The discrepancies between the present numerical simulation and the experimental results taken from the existing literature, which are caused by the mixture and turbulence models simplifying assumptions, are discussed in this paper.

Prediction and Diagnosis of Typhoon Morakot (2009) Using the Naval Research Laboratory's Mesoscale Tropical Cyclone Model

Prediction and Diagnosis of Typhoon Morakot (2009) Using the Naval Research Laboratory's Mesoscale Tropical Cyclone Model

Global Stochasic Tropical Cyclone Modeling and Application to Analysis of Future Cyclone Properties due to Global Climate Change

The scarcity of tropical cyclone data causes the difficulty of external force estimation for coastal structures. The Stochastic Tropical cyclone Model (STM) is a useful method for overcoming this problem. We developed a global STM based on IBTrACS dataset and validated the model performance for statistics of tropical cyclone data. After that, the future change estimated from 8 different General Circulation Model projections under global warming scenarios was implemented in the STM. By using the STM, we estimated the future cyclone number and magnitude quantitatively.

Sensitivity of the Simulated Tropical Cyclone Inner-Core Size to the Initial Vortex Size*

Abstract The multiply nested, fully compressible, nonhydrostatic tropical cyclone model version 4 (TCM4) is used to examine and understand the sensitivity of the simulated tropical cyclone (TC) inner-core size to its initial vortex size. The results show that although the simulated TC intensity at the mature stage is weakly dependent on the initial vortex size for the general settings, the simulated TC inner-core size is largely determined by the initial vortex size. The initial vortex size is critical to both the energy input from the ocean and the effectiveness of the inward angular momentum transport by the transverse circulation driven by eyewall convection and diabatic heating in spiral rainbands. Strong outer winds in a storm with a large initial size lead to large entropy fluxes to a large radial extent outside the eyewall, favoring the development of active spiral rainbands. Latent heat released in spiral rainbands plays a key role in increasing the low-level radial inflow and accelerating tangential winds outside the eyewall, leading to outward expansion of tangential wind fields and thus increasing the inner-core size of the simulated storm. On the contrary, a storm with a small initial size has weaker outer winds and smaller surface entropy fluxes outside the eyewall and is accompanied by less active spiral rainbands and thus a much slower increase in the inner-core size. The effectiveness of the inward transport of absolute angular momentum to increase the tangential winds outside the eyewall is largely determined by the radial extent of the vertical absolute vorticity, which is shown to be higher in a large size vortex. The relative importance of the initial vortex size and the environmental relative humidity (RH) to the TC inner-core size is also evaluated. It is found that the inner-core size of the simulated storm at the mature stage depends more heavily on the initial vortex size than on the initial RH of the environment.

On the consistency between dynamical and thermodynamic equations with prescribed vertical motion in an analytical tropical cyclone model

In our earlier paper, we presented an analytical model for intensifying tropical cyclones (TCs), in which the effects of all nonlinear terms in the horizontal momentum equations are retained. This analytical model was obtained by prescribing the time evolution of the vertical motion. In this paper, we demonstrate that, with the prescribed vertical motion, the system of governing equations for geophysical flows can be separated into two subsystems: one consisting of the horizontal momentum and continuity equations, and the other including the vertical momentum and thermodynamical equations. Results show that the analytical solutions for the horizontal winds obtained from the first subsystem are consistent with the mass field in the second subsystem, such as the thermal wind relationship in TCs. Furthermore, we show that use of any functional form for the mean vertical motion will not affect our previous major conclusions about the different growth rates either between the secondary and primary circulations or between the inner and outer regions in TCs. Copyright © 2010 Royal Meteorological Society

Modeling and multi-objective optimization of square cyclones using CFD and neural networks

Increasing of collection efficiency ( η) and decreasing of the pressure drop (Δ p), simultaneously, are important purpose in the design of cyclone separators. In the present study, multi-objective optimization of square cyclones is performed at three steps. At the first step, collection efficiency ( η) and the pressure drop (Δ p) in a set of square cyclones are numerically investigated using CFD techniques. Two meta-models based on the evolved group method of data handling (GMDH) type neural networks are obtained, at the second step, for modeling of η and Δ p with respect to geometrical design variables. Finally, using obtained polynomial neural networks, multi-objective genetic algorithms are used for Pareto based optimization of square cyclones considering two conflicting objectives, η and Δ p. It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of square cyclones can be discovered by Pareto based multi-objective optimization of the obtained polynomial meta-models. Such important optimal principles would not have been obtained without the use of both GMDH-type neural network modeling and the Pareto optimization approach.

Leukotriene B4 BLT Receptor Signaling Regulates the Level and Stability of Cyclooxygenase-2 (COX-2) mRNA through Restricted Activation of Ras/Raf/ERK/p42 AUF1 Pathway

Recent studies suggest that active resolution of the inflammatory response in animal models of arthritis may involve leukotriene B(4) (LTB(4))-dependent stimulation of "intermediate" prostaglandin production, which in turn favors the synthesis of "downstream" anti-inflammatory and pro-resolving lipoxins, resolvins, and protectins. We explored a putative mechanism involving LTB(4)-dependent control of cyclooxygenase-2 (COX-2) expression, the rate-limiting step in inflammatory prostaglandin biosynthesis. Indeed, LTB(4) potently up-regulated/stabilized interleukin-1beta-induced COX-2 mRNA and protein expression under conditions of COX-2 inhibitor-dependent blockade of PGE(2) release in human synovial fibroblasts (EC(50) = 16.5 + or - 1.7 nm for mRNA; 19 + or - 2.4 nm for protein, n = 4). The latter response was pertussis toxin-sensitive, and semi-quantitative reverse transcription-PCR confirmed the quantitative predominance of the BLT2 receptor. Transfection experiments, using human COX-2 promoter plasmids and chimeric luciferase-COX-2 mRNA 3'-untranslated region (3'-UTR) reporter constructs, revealed that LTB(4) exerted its stabilizing effect at the post-transcriptional level through a 116-bp adenylate/uridylate-rich sequence in the proximal region of the COX-2 3'-UTR. Using luciferase-COX-2 mRNA 3'-UTR reporter constructs and Ras/c-Raf expression and mutant constructs, we showed that the Ras/c-Raf/MEK1/2/ERK1/2 signaling pathway mediated LTB(4)-dependent COX-2 mRNA stabilization. Knockdown experiments with specific short hairpin RNAs confirmed that LTB(4) stabilization of COX-2 mRNA was apparently mediated through the RNA-binding protein, p42 AUF1. The nuclear export of p42 AUF1 was driven by c-Raf/MEK1/2/ERK1/2 signaling and sensitive to leptomycin B treatment, suggesting a CRM1-dependent mechanism. We conclude that LTB(4) may support the resolution phase of the inflammatory response by stabilizing COX-2, ensuring a reservoir of ambient pro-resolution lipid mediators.

TBM construction process simulation and performance optimization

Long tunnel excavation with tunnel boring machine (TBM) is a complex and stochastic process. It is easily affected by uncertainties and needs to be adjusted according to specific geological conditions in different tunnel sections, which makes the construction scheduling and management difficult. Based on the rock mass classification, this paper estimates the penetration rate. Using the rate, a cyclic network simulation (CYCLONE) model of TBM boring system is established, and the advance rates under different geological conditions are determined. Then, the impact of different cutter head thrust, which is chosen in reasonable range according to previous experiences, on project schedule is analyzed. Moreover, the simulation model of mucking system is built to determine the number of muck trains and rail intersections reasonably, regarding the efficiency of muck loading and material transporting. Based on the interaction and interrelation between TBM boring system and mucking system, the combined CYCLONE model for the entire tunneling process is established. Then reasonable construction schedule, the utilization rate of working resources, and the probability of project completion are obtained through the model programming. At last, a project application shows the feasibility of the presented method.

Distribution of multi-phase gas–solid flow across identical parallel cyclones: Modeling and experimental study

There is evidence in the literature of mal-distribution of multi-phase flow across identical parallel branches. The distribution of gas–solid flow through identical parallel cyclones is investigated based on an analytical model which includes a semi-empirical equation from the literature for cyclone pressure drop. Using the proposed model, many steady-state gas–solid distributions are obtained. Solutions with maximum energy dissipation are considered to be unlikely. The results indicate that the non-linearity of the system can lead to non-uniform distributions for high solids loadings, whereas lower loadings result in uniform distributions, or those that are so close to being uniform that experiments will not be able to distinguish differences between the flows. Experiments were carried out for a pair of identical standard cyclones of diameter 101.6 mm to determine the distribution of dilute gas–solid flow. The results are consistent with the proposed cyclone model. Finally, it is likely that differential fouling can influence the flow distribution and make it non-uniform.

A radius –depth model for midlatitude cyclones in reanalysis data and simulations

AbstractGeometric properties of winter (DJF) and summer (JJA) midlatitude cyclones are analysed in reanalysis data, present‐day and global warming simulations. Cyclone centres are identified by the minima of the 1000 hPa geopotential height. Fitting an azimuthally symmetric Gaussian function to the surrounding height field provides cyclone depth (difference between the cyclone centre and the synoptic environment), radius (standard deviation), geostrophic wind and vorticity. Analysing ERA‐40 reanalysis data of different resolutions and Intergovernmental Panel on Climate Change (IPCC) scenario simulations by the coupled atmosphere–ocean general circulation model ECHAM5/MPI‐OM yields mean radii of 300–500 km in winter and 300–400 km in summer. Depth maxima occur in the storm tracks (determined by the bandpass‐filtered variance of the geopotential height), and the smallest radii characterize oceanic cyclogenesis regions. The geostrophic vorticity, derived from the fitted Gaussian model, agrees reasonably well with the observed relative vorticity. Future warmer climate scenarios exhibit smaller radii and weaker depths during winter and summer. An intense growth of the depth is found during the 2 –10 day cyclone life cycles, while the radii reveal negligible growth. Compositing depths with respect to normalized total lifetime leads to rescaled depth life cycles, which collapse to a simple universal function, ã(1 − ã), for relative cyclone age ã. Copyright © 2010 Royal Meteorological Society

Specifying Air-Sea Exchange Coefficients in the High-Wind Regime of a Mature Tropical Cyclone by an Adjoint Data Assimilation Method

Uncertainty in the values of air-sea exchange coefficients has a detrimental effect on tropical cyclone (TC) modeling. Since a TC is one of the most destructive disasters, a method is required to reduce such uncertainty with respect to scientific progress and disaster prevention. In this study, we investigate the feasibility of specifying air-sea exchange coefficients in the high-wind regime of a mature TC by an identical twin experiment using the adjoint data assimilation method. The forward integration is executed by an intermediate cloud-resolving atmosphere-ocean coupled model, while the datasets for the backward integration are sampled as in multiple aircraft missions. Our results show that the air-sea exchange coefficients are successfully improved toward the “True” values. The updated air-sea exchange coefficients yield persistent improvements in the maximum wind speed, the radius of maximum wind, the radius of strong updraft, and in the distribution of water vapor. Without adjustment of the exchange coefficients, the analysis field of the inner-core is contaminated, even if the initial state is modified by the adjoint method.

Long‐term rainfall risk from tropical cyclones in coastal areas

We develop a methodology for the frequency of extreme rainfall intensities caused by tropical cyclones (TCs) in coastal areas. The model does not account for landfall effects. This makes the developed framework best suited for open water sites and coastal areas with flat topography. The mean rainfall field associated with a TC with maximum tangential wind speed Vmax, radius of maximum winds Rmax, and translation speed Vt is obtained using a physically based model, whereas rainfall variability at both large scales (from storm to storm) and small scales (due to rainbands and local convection) is modeled statistically. The statistical component is estimated using precipitation radar data from the Tropical Rainfall Measuring Mission. Taylor's hypothesis is used to convert spatial rainfall intensity fluctuations to temporal fluctuations at a given location A. The combined physical‐statistical model gives the distribution of the maximum rainfall intensity at A during an averaging period D for a TC with characteristics (Vmax, Rmax, Vt) that passes at a given distance from A. To illustrate the use of the model for long‐term rainfall risk analysis, we formulate a recurrence model for tropical cyclones in the Gulf of Mexico that make landfall between longitudes 85° and 95°W. We then use the rainfall and recurrence models to assess the rainfall risk for New Orleans. For return periods of 100 years or more and long averaging durations (D around 12–24 h), tropical cyclones dominate over other rainfall event types, whereas the reverse is true for shorter return periods or shorter averaging durations.

Computational investigation of typhoon-induced storm surge in Hangzhou Bay, China

The Hangzhou Bay faces frequent threats from typhoon-induced storm surge and has attracted considerable attentions of coastal researchers and environmental workers. A three-dimensional storm surge model system based on Finite-Volume Coastal Ocean Model (FVCOM) and analytical cyclone model is applied to investigate the hydrodynamic response in the Hangzhou Bay to tropical typhoon. This model has been used to reproduce the storm surge generated by Typhoon Agnes (No. 8114) and the simulated wind field and water elevations have been compared with the available field observations. A series of numerical experimental cases have been conducted to study the effects of land reclamation project (shoreline relocation and seabed deformation) and cyclonic parameters (minimal central pressure (MCP), radius to maximal wind (RMW) and translation speed (TS)) on the hydrodynamics in the Hangzhou Bay. The results show that the shoreline relocation and seabed deformation could generate much higher storm surge in the vicinity of reclamation project with the shoreline relocation making main contribution (about 70%) to this increase. It is found that among the cyclonic parameters, RMW is the most important factor affecting the peak surge in the Hangzhou Bay.

Balanced and unbalanced aspects of tropical cyclone intensification

AbstractWe investigate the extent to which the azimuthally–averaged fields from a three‐dimensional, non‐hydrostatic, tropical cyclone model can be captured by axisymmetric balance theory. The secondary (overturning) circulation and balanced tendency for the primary circulation are obtained by solving a general form of the Sawyer–Eliassen equation with the diabatic heating, eddy heat fluxes and tangential momentum sources (eddy momentum fluxes, boundary‐layer friction and subgrid‐scale diffusion) diagnosed from the model. The occurrence of regions of weak symmetric instability at low levels and in the upper‐tropospheric outflow layer requires a regularization procedure so that the Sawyer–Eliassen equation remains elliptic. The balanced calculations presented capture a major fraction of the azimuthally–averaged secondary circulation of the three‐dimensional simulation except in the boundary layer, where the balanced assumption breaks down and where there is an inward agradient force. In particular, the balance theory is shown to significantly underestimate the low‐level radial inflow and therefore the maximum azimuthal‐mean tangential wind tendency. In the balance theory, the diabatic forcing associated with the eyewall convection accounts for a large fraction of the secondary circulation. The findings herein underscore both the utility of axisymmetric balance theory and also its limitations in describing the axisymmetric intensification physics of a tropical cyclone vortex. Copyright © 2009 Royal Meteorological Society

An assessment of a Greenland lee cyclone during the Greenland Flow Distortion experiment: An observational approach

AbstractOn 3 March 2007 between 0920 and 1545 UTC, the mesoscale structure of a mature lee cyclone southeast of Greenland was successfully captured during a flight with a research aircraft during the Greenland Flow Distortion experiment (GFDex). The cyclone was accompanied by hazardous weather conditions such as extensive icing and low‐level wind speeds exceeding 34 m s−1. Calculations based on atmospheric soundings from Egedesminde on the west coast of Greenland indicate that conditions were favourable for flow splitting and hence cyclogenesis in the lee of Greenland during the formation of the cyclone. PV inversion carried out on an upper‐level southward‐moving potential vorticity (PV) anomaly indicates that upper‐level forcing as well as orographic forcing had an important role in the cyclone development. The frontal seclusion of the cyclone's warm core was consistent with both the Norwegian cyclone model and Shapiro and Keyser's model. However, it was not possible to match this cyclone precisely with any of these models, which is probably a consequence of the strong influence from Greenland on the cyclone development. In situ measurements showing a combination of warm dry air with relatively high ozone concentrations in the centre of the cyclone together with trajectory calculations indicate that this air had experienced considerable descent, probably induced by Greenland's orography. The observations documented the cyclone's mesoscale structure, and clearly revealed a deep tropopause fold. This tropopause fold is a manifestation of the forcing on the cyclone from the upper‐level PV anomaly. Copyright © 2009 Royal Meteorological Society

Generation of Nanoparticles with a Nebulizer-Cyclone System

A cyclone was used to modify the droplet output with a three-jet Collison nebulizer. The cyclone-nebulizer system was tested by producing ammonium fluorescein particles from a liquid suspension. The particle size distribution produced with the cyclone was smaller and narrower than that produced without the cyclone. Thus, the cyclone effectively removed the large droplets produced by the nebulizer. The nebulizer-cyclone system reduced the GSD of the output aerosol from 1.7 to 1.4. At the input pressures greater than 138 kPa, the concentration of 10–60 nm particles was greater with the cyclone than without the cyclone. These results are consistent with the shattering of large droplets within the cyclone and re-entrainment of these small secondary droplets. Optimization of the system using cyclone modeling to enhance the sharpness of cut, operational improvements, and decreased venting could maximize the output of tailored distributions of nanoparticles for various applications.