A Multiscale Numerical Study of Hurricane Andrew (1992). Part V: Inner-Core Thermodynamics

2002 ◽  
Vol 130 (11) ◽  
pp. 2745-2763 ◽  
Author(s):  
Da-Lin Zhang ◽  
Yubao Liu ◽  
M. K. Yau
Keyword(s):  
Inner Core ◽  
Numerical Study ◽  
Hurricane Andrew

scholarly journals An Idealized Numerical Study of Shear-Relative Low-Level Mean Flow on Tropical Cyclone Intensity and Size

2019 ◽  
Vol 76 (8) ◽  
pp. 2309-2334 ◽  
Author(s):  
Buo-Fu Chen ◽  
Christopher A. Davis ◽  
Ying-Hwa Kuo
Keyword(s):  
Boundary Layer ◽  
Tropical Cyclone ◽  
Inner Core ◽  
Numerical Study ◽  
Vertical Wind Shear ◽  
Development Stage ◽  
Surface Fluxes ◽  
Mean Flow ◽  
Low Level ◽  
Core Convection

Abstract Given comparable background vertical wind shear (VWS) magnitudes, the initially imposed shear-relative low-level mean flow (LMF) is hypothesized to modify the structure and convective features of a tropical cyclone (TC). This study uses idealized Weather Research and Forecasting Model simulations to examine TC structure and convection affected by various LMFs directed toward eight shear-relative orientations. The simulated TC affected by an initially imposed LMF directed toward downshear left yields an anomalously high intensification rate, while an upshear-right LMF yields a relatively high expansion rate. These two shear-relative LMF orientations affect the asymmetry of both surface fluxes and frictional inflow in the boundary layer and thus modify the TC convection. During the early development stage, the initially imposed downshear-left LMF promotes inner-core convection because of high boundary layer moisture fluxes into the inner core and is thus favorable for TC intensification because of large radial fluxes of azimuthal mean vorticity near the radius of maximum wind in the boundary layer. However, TCs affected by various LMFs may modify the near-TC VWS differently, making the intensity evolution afterward more complicated. The TC with a fast-established eyewall in response to the downshear-left LMF further reduces the near-TC VWS, maintaining a relatively high intensification rate. For the upshear-right LMF that leads to active and sustained rainbands in the downshear quadrants, TC size expansion is promoted by a positive radial flux of eddy vorticity near the radius of 34-kt wind (1 kt ≈ 0.51 m s−1) because the vorticity associated with the rainbands is in phase with the storm-motion-relative inflow.

Numerical Study on the Extremely Rapid Intensification of an Intense Tropical Cyclone: Typhoon Ida (1958)

2015 ◽  
Vol 72 (11) ◽  
pp. 4194-4217 ◽  
Author(s):  
Sachie Kanada ◽  
Akiyoshi Wada
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Numerical Study ◽  
Vertical Wind Shear ◽  
Leading Edge ◽  
Central Pressure ◽  
Rapid Intensification ◽  
Near Surface ◽  
Warm Core ◽  
Upper Level

Abstract Extremely rapid intensification (ERI) of Typhoon Ida (1958) was examined with a 2-km-mesh nonhydrostatic model initiated at three different times. Ida was an extremely intense tropical cyclone with a minimum central pressure of 877 hPa. The maximum central pressure drop in 24 h exceeded 90 hPa. ERI was successfully simulated in two of the three experiments. A factor crucial to simulating ERI was a combination of shallow-to-moderate convection and tall, upright convective bursts (CBs). Under a strong environmental vertical wind shear (>10 m s−1), shallow-to-moderate convection on the downshear side that occurred around the intense near-surface inflow moistened the inner-core area. Meanwhile, dry subsiding flows on the upshear side helped intensification of midlevel (8 km) inertial stability. First, a midlevel warm core appeared below 10 km in the shallow-to-moderate convection areas, being followed by the development of the upper-level warm core associated with tall convection. When tall, upright, rotating CBs formed from the leading edge of the intense near-surface inflow, ERI was triggered at the area in which the air became warm and humid. CBs penetrated into the upper troposphere, aligning the areas with high vertical vorticity at low to midlevels. The upper-level warm core developed rapidly in combination with the midlevel warm core. Under the preconditioned environment, the formation of the upright CBs inside the radius of maximum wind speeds led to an upright axis of the secondary circulation within high inertial stability, resulting in a very rapid central pressure deepening.

Numerical study of elliptical modons using a spectral method

1990 ◽  
Vol 221 ◽  
pp. 597-611 ◽  
Author(s):  
John P. Boyd ◽  
Hong Ma
Keyword(s):  
Analytical Solution ◽  
Spectral Method ◽  
Inner Core ◽  
Numerical Study ◽  
Earth’S Rotation ◽  
Dynamical Structure ◽  
Irrotational Flow ◽  
Strongly Nonlinear ◽  
Vortex Pairs ◽  
The Relationship

We study the relationship between dynamical structure and shape for vortex pairs, now usually named ‘modons’. When the boundary between the exterior irrotational flow and the inner core of non-zero vorticity is a circle, an analytical solution is known. Here, we generalize the circular modons to solitary vortex pairs whose vorticity boundary is an ellipse. We find that as the eccentricity of the ellipse increases, the vorticity becomes concentrated in narrow ridges which run just inside the elliptical vorticity boundary and continue just inside the line of zero vorticity which divides the two vortices. Each vortex becomes increasingly ‘hollow’ in the sense that each contains a broad valley of low vorticity which is completely enclosed by the ridge of high vorticity already described. The relationship between vorticity ζ and streak function Ψ, which is linear for the circular modons, becomes strongly nonlinear for highly eccentric modons, qualitatively resembling ζ ∝ Ψe−λΨ for some constant λ. In this study, we neglect the Earth's rotation, but our method is directly applicable to quasi-geostrophic modons, too. An efficient and simple spectral method for modon problems is provided.

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 Seismic Performance Evaluation of a Proposed Buckling-Restrained Brace for RC-MRFS

2019 ◽  
Vol 29 (3) ◽  
pp. 164-173
Author(s):  
Arunraj Ebanesar ◽  
Daniel Cruze ◽  
Ehsan Noroozinejad Farsangi ◽  
Vincent Sam Jebadurai Seenivasan ◽  
Adil Dar Mohammad ◽  
...  
Keyword(s):  
Seismic Performance ◽  
Inner Core ◽  
Numerical Study ◽  
Construction Material ◽  
Time History ◽  
Expanded Polystyrene ◽  
Disaster Mitigation ◽  
Ductile Material ◽  
Conventional Concrete ◽  
Buckling Restrained Brace

Abstract This paper presents a novel buckling-restrained brace (BRB) where the inner core is restrained by a concrete infilled Expanded Polystyrene Sheet (EPS) instead of the conventional concrete infilled tube section, to resist inner core buckling. It serves two purposes, firstly, the EPS is a ductile material, which is favourable in terms of seismic performance and, secondly, the outer construction material has better corrosion resistance. Thus, the life of the steel core can be prolonged. In this study, 6 BRB specimens were prepared, of which 3 BRB specimens were infilled with concrete and the remaining 3 BRB specimens with concrete and EPSs, in order to study their performance under cyclic loading. Three different core heights, all with the same core thickness, were adopted. The test results indicate that the load-carrying capacity of this novel BRB is higher than the conventional BRB. Further, the length of the steel tube also affects the strength of the seismic disaster mitigation system. Lastly, a numerical study on a single bay RC frame, with and without BRB subjected to time history analysis, was conducted to check the global performance of this novel system. It was found that the structural responses had substantially decreased.

A Numerical Study of Outer Rainband Formation in a Sheared Tropical Cyclone

2017 ◽  
Vol 74 (1) ◽  
pp. 203-227 ◽  
Author(s):  
Qingqing Li ◽  
Yuqing Wang ◽  
Yihong Duan
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Numerical Study ◽  
Outer Boundary ◽  
Vertical Wind Shear ◽  
Dynamical Process ◽  
Radial Gradient ◽  
Core Convection ◽  
Vortex Rossby Wave ◽  
Convective Cells

Abstract The dynamical process of outer rainband formation in a sheared tropical cyclone (TC) is examined in this study using the fully compressible, nonhydrostatic TC model. After the easterly vertical wind shear of 10 m s−1 was imposed upon an intensifying strong TC, an outer rainband characterized by a wavenumber-1 structure formed as a typical principal rainband downshear. Further analysis indicates that the outer rainband formation was closely connected to the activity of the inner rainband previously formed downshear. Moving radially outward, the inner rainband tended to be filamented owing to the strong radial gradient of angular velocity. As the inner rainband approached the outer boundary of the inner core, convection in its middle and upwind segments reinvigorated and nascent convective cells formed upwind of the rainband, caused mainly by the decreased filamentation and stabilization. Subsequently, the rainband reorganized into a typical outer rainband. Three different scenarios are found to be responsible for the outer rainband formation from downshear inner rainbands. The first is the outer rainband forming from an inner rainband downshear as a sheared vortex Rossby wave. The second is the outer rainband forming directly from a single deformation-induced inner rainband. The third is the outer rainband developing from an inner rainband downshear organized from a blend–merger of inner rainbands that were initiated from locally deformed convection upshear right.

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