scholarly journals A Numerical Study of the Track Deflection of Supertyphoon Haitang (2005) Prior to Its Landfall in Taiwan

2008 ◽  
Vol 136 (2) ◽  
pp. 598-615 ◽  
Author(s):  
Guo-Ji Jian ◽  
Chun-Chieh Wu
Keyword(s):  
Control Experiment ◽  
Inner Core ◽  
Numerical Study ◽  
Sensitivity Study ◽  
Weather Research And Forecasting ◽  
Translation Speed ◽  
Fine Mesh ◽  
Steering Flow ◽  
Moving Storm ◽  
Channeling Effect

Abstract A series of numerical simulations are conducted using the advanced research version of the Weather Research and Forecasting model with a 4-km fine mesh to examine the physical processes responsible for the significant track deflection and looping motion before the landfall of Supertyphoon Haitang (2005) in Taiwan, which poses a unique scientific and forecasting issue. In the control experiment, a low-level northerly jet induced by the channeling effect forms in the western quadrant of the approaching storm, where the inner-core circulation is constrained by the presence of Taiwan’s terrain. Because of the channeling effect, the strongest winds of the storm are shifted to the western portion of the eyewall. The northerly advection flow (averaged asymmetric winds within 100-km radius) results in a sharp southward turn of the westward-moving storm. The time series of the advection flow shows that the advection wind vectors rotate cyclonically in time and well match the motion of the simulated vortex during the looping process. A sensitivity study of lowering the Taiwan terrain elevations to 70% or 40% of those in the control experiment reduces the southward track deflection and loop amplitude. The experiment with the reduced elevation to 10% of the control experiment does not show a looping track and thus demonstrates the key role of the terrain-induced channeling effect. Experiments applying different values of the structure parameter α illustrate that increasing the strength, size, and translation speed of the initial storm results in a smaller interaction with Taiwan’s terrain and a smaller average steering flow caused by the asymmetric circulation, which leads to a proportionally smaller southward track deflection without making a loop.

scholarly journals Impact of environmental moisture on tropical cyclone intensification

2015 ◽  
Vol 15 (11) ◽  
pp. 16111-16139 ◽  
Author(s):  
L. Wu ◽  
H. Su ◽  
R. G. Fovell ◽  
T. J. Dunkerton ◽  
Z. Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Inner Core ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Convective Activity ◽  
Dry Air ◽  
Moving Storm ◽  
Lagrangian Boundary ◽  
Moisture Increase

Abstract. The impacts of environmental moisture on the intensification of a tropical cyclone (TC) are investigated in the Weather Research and Forecasting (WRF) model, with a focus on the azimuthal asymmetry of the moisture impacts. A series of sensitivity experiments with varying moisture perturbations in the environment are conducted and the Marsupial Paradigm framework is employed to understand the different moisture impacts. We find that modification of environmental moisture has insignificant impacts on the storm in this case unless it leads to convective activity in the environment, which deforms the quasi-Lagrangian boundary of the storm. By facilitating convection and precipitation outside the storm, enhanced environmental moisture ahead of the northwestward-moving storm induces a dry air intrusion to the inner core and limits TC intensification. However, increased moisture in the rear quadrants favors intensification by providing more moisture to the inner core and promoting storm symmetry, with primary contributions coming from moisture increase in the boundary layer. The different impacts of environmental moisture on TC intensification are governed by the relative locations of moisture perturbations and their interactions with the storm Lagrangian structure.

scholarly journals The Influence of Island Topography on Typhoon Track Deflection

2011 ◽  
Vol 139 (6) ◽  
pp. 1708-1727 ◽  
Author(s):  
Yi-Hsuan Huang ◽  
Chun-Chieh Wu ◽  
Yuqing Wang
Keyword(s):  
High Resolution ◽  
Inner Core ◽  
Realistic Model ◽  
Cloud Microphysics ◽  
The North ◽  
Steering Flow ◽  
Typhoon Track ◽  
Physics Model ◽  
Channeling Effect ◽  
Prediction And Simulation

Abstract High-resolution simulations for Typhoon Krosa (2007) and a set of idealized experiments are conducted using a full-physics model to investigate the eminent deflection of typhoon track prior to its landfall over mountainous island topography. The terrain height of Taiwan plays the most important role in Typhoon Krosa’s looping motion at its landfall, while the surface properties, details in the topographic shape of Taiwan, and the cloud microphysics are shown to be secondary to the track deflection. A simulation with 3-km resolution and realistic model settings reproduces the observed Krosa’s track, while that with 9-km resolution fails, suggesting that high resolution to better resolve the typhoon–terrain interactions is important for the prediction and simulation of typhoon track deflection prior to landfall. Results from idealized experiments with model configurations mimicking those of Supertyphoon Krosa show that vortices approaching the northern and central topography are significantly deflected to the south before making sharp turns to the north, forming a kinked track pattern prior to and during landfall. This storm movement is consistent with the observed looping cases in Taiwan. Both real-case and idealized simulations show strong channel winds enhanced between the storm and the terrain when deflection occurs. Backward trajectory analyses support the concept of the channeling effect, which has been previously found to be crucial to the looping motion of Typhoon Haitang (2005) as well. However, the inner-core asymmetric ventilation flow does not match the movement of a deflected typhoon perfectly, partly because the steering flow is not well defined and could not completely capture the terrain-induced deflection in the simulation and in nature.

scholarly journals Impact of environmental moisture on tropical cyclone intensification

2015 ◽  
Vol 15 (24) ◽  
pp. 14041-14053 ◽  
Author(s):  
L. Wu ◽  
H. Su ◽  
R. G. Fovell ◽  
T. J. Dunkerton ◽  
Z. Wang ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Moisture Transport ◽  
Inner Core ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Convective Activity ◽  
Dry Air ◽  
Moving Storm ◽  
Lagrangian Boundary ◽  
Moisture Increase

Abstract. The impacts of environmental moisture on the intensification of a tropical cyclone (TC) are investigated in the Weather Research and Forecasting (WRF) model, with a focus on the azimuthal asymmetry of the moisture impacts relative to the storm path. A series of sensitivity experiments with varying moisture perturbations in the environment are conducted and the Marsupial Paradigm framework is employed to understand the different moisture impacts. We find that modification of environmental moisture has insignificant impacts on the storm in this case unless it leads to convective activity that deforms the quasi-Lagrangian boundary of the storm and changes the moisture transport into the storm. By facilitating convection and precipitation outside the storm, enhanced environmental moisture ahead of the northwestward-moving storm induces a dry air intrusion to the inner core and limits TC intensification. In contrast, increased moisture in the rear quadrants favors intensification by providing more moisture to the inner core and promoting storm symmetry, with primary contributions coming from moisture increase in the boundary layer. The different impacts of environmental moisture on TC intensification are governed by the relative locations of moisture perturbations and their interactions with the storm Lagrangian structure.

scholarly journals The Impact of Idealized Terrain on Upstream Tropical Cyclone Track

2018 ◽  
Vol 75 (11) ◽  
pp. 3887-3910 ◽  
Author(s):  
Kuan-Chieh Huang ◽  
Chun-Chieh Wu
Keyword(s):  
Large Scale ◽  
Inner Core ◽  
Wrf Model ◽  
Weather Research And Forecasting ◽  
Core Dynamics ◽  
Underlying Mechanisms ◽  
Channeling Effect ◽  
The Impact ◽  
Steering Current

Abstract Tropical cyclones (TCs) encountering the terrain of Taiwan usually experience prominent track deflection, resulting in uncertainty in TC track forecasts. The underlying mechanisms of TC deflection are examined to better understand the pattern of TC tracks under various flow regimes. In this study, idealized experiments are carried out utilizing the Advanced Research version of the Weather Research and Forecasting (WRF) Model. This study investigates the motion of a TC that is deflected southward while moving westward toward an idealized terrain similar to Taiwan. An analysis of both the flow asymmetries and the potential vorticity tendency (PVT) demonstrates that horizontal advection contributes to the southward movement of the TC. The track deflection is examined in two separate time periods, with different mechanisms leading to the southward movement. Changes in the background flow induced by the terrain first cause the large-scale steering current to push the TC southward while the TC is still far from the terrain. As the TC approaches the idealized topography, the role of the inner-core dynamics becomes important, and the TC terrain-induced channeling effect results in further southward deflection. Asymmetries in the midlevel flow also develop during this period, in part associated with the effect of vertical momentum transport. The combination of the large-scale environmental flow, the low-level channeling effect, and asymmetries in the midlevel flow all contribute to the southward deflection of the TC track.

A Numerical Study of Typhoon Megi (2010). Part II: Eyewall Evolution Crossing the Luzon Island

2020 ◽  
Author(s):  
Hui Wang ◽  
Yuqing Wang
Keyword(s):  
Control Experiment ◽  
Numerical Study ◽  
Wrf Model ◽  
Surface Friction ◽  
Weather Research And Forecasting ◽  
Sensitivity Experiment ◽  
Structure Changes ◽  
Surface Enthalpy ◽  
Spiral Rainbands ◽  
Reduced Surface

AbstractTyphoon Megi (2010) experienced drastic eyewall structure changes when it crossed the Luzon Island and entered the South China Sea (SCS), including the contraction and breakdown of the eyewall after landfall over the Luzon Island, the formation of a new large outer eyewall accompanied by re-intensification of the storm after it entered the SCS, and the appearance of a short-lived small inner eyewall. These features were reproduced reasonably well in a control simulation using the Advanced Weather Research and Forecasting (ARW–WRF) model. In this study, the eyewall processes of the simulated Megi during and after landfall have been analyzed.Results show that the presence of the landmass of Luzon Island increased surface friction and reduced surface enthalpy flux, leading to the original eyewall to contract and break down and the weakening of the storm. The formation of the new large eyewall results mainly from the axisymmetrization of outer spiral rainbands after the storm core moved across the Luzon Island and entered the SCS. The appearance of the small inner eyewall over the SCS was due to the increased surface enthalpy flux and the revival of convection in the central region of the storm core. In a sensitivity experiment with the mesoscale-mountain replaced by flat surface over the Luzon Island, a new large outer eyewall formed over the western Luzon Island with its size about one third smaller after the storm entered the SCS than that in the control experiment with the terrain over the Luzon Island unchanged.

Failure behavior analysis of steel strip–reinforced flexible pipe under combined tension and internal pressure

2018 ◽  
Vol 33 (6) ◽  
pp. 727-753
Author(s):  
Wei Chen ◽  
Haichao Xiong ◽  
Yong Bai
Keyword(s):  
Internal Pressure ◽  
Numerical Study ◽  
Steel Strip ◽  
Sensitivity Study ◽  
Failure Behavior ◽  
Load Path ◽  
Flexible Pipe ◽  
Fe Method ◽  
Axial Extension ◽  
The Relationship

The mechanical behaviors of steel strip–reinforced flexible pipe (steel strip PSP) under combined axial extension → internal pressure ( T→ P) load path were investigated. Typical failure characteristics of pipe samples under pure internal pressure and T→ P load path were identified in the full-scale experiments. A theoretical model for pipe under tension load was proposed to capture the relationship between axial extension of the pipe body and stress state of the steel strip. Numerical study based on finite element (FE) method was conducted to simulate the experiment process, and good agreement between FE data and experiment results were observed. Sensitivity study was conducted to study the effect of some key parameters on the pipe antiburst capacities in T→P load path; the effect of preloaded internal pressure on the pipe tensile capacity in P→T load path was also studied. Useful conclusions were drawn for the design and application of the steel strip PSP.

scholarly journals Causes of Altered Ventricular Mechanics in Hypertrophic Cardiomyopathy—an In-Silico Study

2021 ◽  
Author(s):  
Ekaterina Kovacheva ◽  
Tobias Gerach ◽  
Steffen Schuler ◽  
Marco Ochs ◽  
Olaf Dössel ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Mechanical Behaviour ◽  
In Silico ◽  
Numerical Study ◽  
Radial Strain ◽  
Sensitivity Study ◽  
Homogeneous Distribution ◽  
Wall Thickening ◽  
Force Development ◽  
Ventricular Mechanics

Abstract Background: Hypertrophic cardiomyopathy is a common heart disease causing alteration in the mechanical behaviour of the left ventricle (LV). Decreased myocardial velocities, reduced strain and strain rates have been reported clinically. These alterations result from underlying pathological mechanisms in the tissue: increased wall thickness, altered active and passive force development and/or fiber disarray, which are cumbersome to measure clinically. With a numerical study, we aim to answer: how the variability in each of these mechanisms contributes to altered mechanics of the LV and if the deformation obtained in in-silico experiments is comparable to values reported from clinical measurements. Results: We conducted an in-silico sensitivity study on physiological and pathological mechanisms potentially underlying the clinical hypertrophic cardiomyopathy phenotype. Deformation and mechanical behaviour of whole heart models was evaluated globally and regionally. Hypertrophy of the LV affected the course of strain, strain rate and wall thickening—the root mean squared difference of the wall thickening between control (mean thickness 10 mm) and hypertrophic geometries (17 mm) was >10 %. A reduction of active force development by 40 % led to less overall deformation: maximal radial strain reduced from 26 % to 21 %. A five-fold increase in tissue stiffness caused a more homogeneous distribution of the strain values among the 17 AHA segments. Fiber disarray led to minor changes in the circumferential and radial strain. A combination of pathological mechanisms led to reduced and slower deformation of the LV and halved the longitudinal shortening of the left atria. Conclusions: This study uses a computer model to determine the changes in LV deformation caused by pathological mechanisms that are presumed to underlay hypertrophic cardiomybopathy. This knowledge can complement imaging-derived information to obtain a more accurate diagnosis of hypertrophic cardiomyopathy.

scholarly journals Seismic Vulnerability of Ancient Colonnade

2016 ◽  
pp. 950-974 ◽  
Author(s):  
Vasilis Sarhosis ◽  
Gian Piero Lignola ◽  
Panagiotis G. Asteris
Keyword(s):  
Seismic Vulnerability ◽  
Numerical Study ◽  
Distinct Element ◽  
Structural Response ◽  
Frictional Resistance ◽  
Sensitivity Study ◽  
Distinct Element Method ◽  
Water Lubrication ◽  
Non Linear ◽  
Element Method

In this chapter, a numerical study to investigate the seismic vulnerability of the two storey colonnade of the Forum in Pompeii has been conducted. Software based on the Distinct Element Method (DEM) of analysis has been used. The colonnade was represented as an assemblage of distinct blocks connected together by zero thickness interfaces which could open and/or close depending on the magnitude and direction of stresses applied to them. Both static and non-linear static analyses have been undertaken. Also, a sensitivity study has been performed to investigate the effect of frictional resistance of the joints on the structural response of the colonnade. This was to simulate potential joint degradation effects and/or possible water lubrication at the joint.

Evaluation of a Wind-Wave System for Ensemble Tropical Cyclone Wave Forecasting. Part I: Winds

2013 ◽  
Vol 28 (2) ◽  
pp. 297-315 ◽  
Author(s):  
Steven M. Lazarus ◽  
Samuel T. Wilson ◽  
Michael E. Splitt ◽  
Gary A. Zarillo
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Synthetic Data ◽  
Radial Distance ◽  
Wave System ◽  
Computationally Efficient ◽  
Wind Fields ◽  
Translation Speed ◽  
Maximum Wind ◽  
Regional Reanalysis

Abstract A computationally efficient method of producing tropical cyclone (TC) wind analyses is developed and tested, using a hindcast methodology, for 12 Gulf of Mexico storms. The analyses are created by blending synthetic data, generated from a simple parametric model constructed using extended best-track data and climatology, with a first-guess field obtained from the NCEP–NCAR North American Regional Reanalysis (NARR). Tests are performed whereby parameters in the wind analysis and vortex model are varied in an attempt to best represent the TC wind fields. A comparison between nonlinear and climatological estimates of the TC size parameter indicates that the former yields a much improved correlation with the best-track radius of maximum wind rm. The analysis, augmented by a pseudoerror term that controls the degree of blending between the NARR and parametric winds, is tuned using buoy observations to calculate wind speed root-mean-square deviation (RMSD), scatter index (SI), and bias. The bias is minimized when the parametric winds are confined to the inner-core region. Analysis wind statistics are stratified within a storm-relative reference frame and by radial distance from storm center, storm intensity, radius of maximum wind, and storm translation speed. The analysis decreases the bias and RMSD in all quadrants for both moderate and strong storms and is most improved for storms with an rm of less than 20 n mi. The largest SI reductions occur for strong storms and storms with an rm of less than 20 n mi. The NARR impacts the analysis bias: when the bias in the former is relatively large, it remains so in the latter.

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