scholarly journals Evolution of the Warm-Core Structure during the Eyewall Replacement Cycle in a Numerically Simulated Tropical Cyclone

2019 ◽  
Vol 76 (8) ◽  
pp. 2559-2573
Author(s):  
Hui Wang ◽  
Yuqing Wang ◽  
Jing Xu ◽  
Yihong Duan
Keyword(s):  
Tropical Cyclone ◽  
Potential Temperature ◽  
Outer Edge ◽  
Core Structure ◽  
Upper Troposphere ◽  
Secondary Eyewall Formation ◽  
Warm Core ◽  
Eyewall Replacement Cycle ◽  
Upper Level ◽  
Replacement Cycle

Abstract This study examines the evolution of the warm-core structure during the secondary eyewall formation (SEF) and the subsequent eyewall replacement cycle (ERC) in a numerically simulated tropical cyclone (TC) under idealized conditions. Results show that prior to the SEF, the TC exhibited a double warm-core structure centered in the middle and upper troposphere in the eye region, and as the storm intensified with a rapid outward expansion of tangential winds, the warm core strengthened and a secondary off-center warm ring developed between 8- and 16-km heights near the outer edge of the eye. During the SEF, both the upper-level warm core and the secondary off-center warm ring rapidly strengthened. As the secondary eyewall intensified and contracted and the primary eyewall weakened and dissipated, the off-center warm ring extended inward and merged with the inner warm core to form a warm core typical of a single-eyewall TC. Results from the azimuthal-mean potential temperature budget indicate that the warming in the eye is due to subsidence and the warming above 14-km height outside the eye is largely contributed by radial warm advection in the outflow. The development of the off-center warm ring is largely due to the subsidence warming near the inner edge of the primary eyewall and in the moat area and the warming by diabatic heating in the upper part of the inner eyewall below 14-km height. Further analysis indicates that the eddy advection also played some role in the warming above 12-km height in the upper troposphere.

scholarly journals Recent Advances in Our Understanding of Tropical Cyclone Intensity Change Processes from Airborne Observations

Atmosphere ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 650
Author(s):  
Robert F. Rogers
Keyword(s):  
Tropical Cyclone ◽  
Inner Core ◽  
Vertical Shear ◽  
Intensity Change ◽  
Change Processes ◽  
Cyclone Intensity ◽  
Secondary Eyewall Formation ◽  
Warm Core ◽  
Major Hurricane ◽  
Upper Level

Recent (past ~15 years) advances in our understanding of tropical cyclone (TC) intensity change processes using aircraft data are summarized here. The focus covers a variety of spatiotemporal scales, regions of the TC inner core, and stages of the TC lifecycle, from preformation to major hurricane status. Topics covered include (1) characterizing TC structure and its relationship to intensity change; (2) TC intensification in vertical shear; (3) planetary boundary layer (PBL) processes and air–sea interaction; (4) upper-level warm core structure and evolution; (5) genesis and development of weak TCs; and (6) secondary eyewall formation/eyewall replacement cycles (SEF/ERC). Gaps in our airborne observational capabilities are discussed, as are new observing technologies to address these gaps and future directions for airborne TC intensity change research.

Effect of TC–Trough Interaction on the Intensity Change of Two Typhoons

2005 ◽  
Vol 20 (2) ◽  
pp. 199-211 ◽  
Author(s):  
Hui Yu ◽  
H. Joe Kwon
Keyword(s):  
Tropical Cyclone ◽  
Wind Shear ◽  
Large Scale ◽  
Vertical Wind Shear ◽  
Vertical Wind ◽  
Intensity Change ◽  
Eddy Flux ◽  
Upper Troposphere ◽  
Shallow Layer ◽  
Upper Level

Abstract Using large-scale analyses, the effect of tropical cyclone–trough interaction on tropical cyclone (TC) intensity change is readdressed by studying the evolution of upper-level eddy flux convergence (EFC) of angular momentum and vertical wind shear for two TCs in the western North Pacific [Typhoons Prapiroon (2000) and Olga (1999)]. Major findings include the following: 1) In spite of decreasing SST, the cyclonic inflow associated with a midlatitude trough should have played an important role in Prapiroon’s intensification to its maximum intensity and the maintenance after recurvature through an increase in EFC. The accompanied large vertical wind shear is concentrated in a shallow layer in the upper troposphere. 2) Although Olga also recurved downstream of a midlatitude trough, its development and maintenance were not strongly influenced by the trough. A TC could maintain itself in an environment with or without upper-level eddy momentum forcing. 3) Both TCs started to decay over cold SST in a large EFC and vertical wind shear environment imposed by the trough. 4) Uncertainty of input adds difficulties in quantitative TC intensity forecasting.

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.

scholarly journals The Warm-Core Structure of Hurricane Earl (2010)

2016 ◽  
Vol 73 (8) ◽  
pp. 3305-3328 ◽  
Author(s):  
Daniel P. Stern ◽  
Fuqing Zhang
Keyword(s):  
Inner Core ◽  
Local Environment ◽  
Core Structure ◽  
Reference State ◽  
Intensity Change ◽  
Warm Core ◽  
Wind Structure ◽  
Environmental Reference ◽  
Flight Level ◽  
Upper Level

Abstract The warm-core structure of Hurricane Earl (2010) is examined on four different days, spanning periods of both rapid intensification (RI) and weakening, using high-altitude dropsondes from both the inner core and the environment, as well as a convection-permitting numerical forecast. During RI, strong warming occurred at all heights, while during rapid weakening, little temperature change was observed, implying the likelihood of substantial (unobserved) cooling above flight level (12 km). Using a local environmental reference state yields a perturbation temperature profile with two distinct maxima of approximately equal magnitude: one at 4–6-km and the other at 9–12-km height. However, using a climatological-mean sounding instead results in the upper-level maximum being substantially stronger than the midlevel maximum. This difference results from the fact that the local environment of Earl was warmer than the climatological mean and that this relative warmth increased with height. There is no obvious systematic relationship between the height of the warm core and either intensity or intensity change for either reference state. The structure of the warm core simulated by the convection-permitting forecast compares well with the observations for the periods encompassing RI. Later, an eyewall replacement cycle went unforecast, and increased errors in the warm-core structure are likely related to errors in the forecast wind structure. At most times, the simulated radius of maximum winds (RMW) had too great of an outward slope (the upper-level RMW was too large), and this is likely also associated with structural biases in the warm core.

scholarly journals A 13-Year Global Climatology of Tropical Cyclone Warm-Core Structures from AIRS Data

2019 ◽  
Vol 147 (3) ◽  
pp. 773-790 ◽  
Author(s):  
Xiang Wang ◽  
Haiyan Jiang
Keyword(s):  
Core Structure ◽  
Tropical Storms ◽  
Atmospheric Infrared Sounder ◽  
Warm Core ◽  
Microwave Sounding Unit ◽  
Microwave Sounding ◽  
Upper Level ◽  
Core Height ◽  
Temperature Retrieval ◽  
Do So

Abstract There is uncertainty as to whether the typical warm-core structure of tropical cyclones (TCs) is featured as an upper-level warm core or not. It has been hypothesized that data from the satellite-borne Advanced Microwave Sounding Unit (AMSU) are inadequate to resolve a realistic TC warm-core structure. This study first evaluates 13 years of Atmospheric Infrared Sounder (AIRS) temperature retrieval against recent dropsonde measurements in TCs. AIRS can resolve the TC warm-core structure well, comparable to the dropsonde observations, although the AMSU-A retrievals fail to do so. Using 13-yr AIRS data in global TCs, a global climatology of the TC warm-core structure is generated in this study. The typical warm-core height is at the upper level around 300–400 hPa for all TCs and increases with TC intensity: 400 hPa (~8 km) for tropical storms, 300 hPa (~10 km) for category 1–3 hurricanes, 250–300 hPa (~10–11 km) for category 4 hurricanes, and 150 hPa (~14 km) for category 5 hurricanes. The range of warm-core height varies with TC intensity as well. A strong correlation between TC intensity and warm-core strength is found. A weaker but still significant correlation between TC intensity and warm-core height is also found.

Tropopause Evolution in a Rapidly Intensifying Tropical Cyclone: A Static Stability Budget Analysis in an Idealized Axisymmetric Framework

2019 ◽  
Vol 76 (1) ◽  
pp. 209-229 ◽  
Author(s):  
Patrick Duran ◽  
John Molinari
Keyword(s):  
Potential Vorticity ◽  
Lower Stratosphere ◽  
Potential Temperature ◽  
Static Stability ◽  
Layer Potential ◽  
Upper Troposphere ◽  
Budget Analysis ◽  
Upper Level ◽  
Cold Point ◽  
Differential Advection

Abstract Upper-level static stability (N2) variations can influence the evolution of the transverse circulation and potential vorticity in intensifying tropical cyclones (TCs). This paper examines these variations during the rapid intensification (RI) of a simulated TC. Over the eye, N2 near the tropopause decreases and the cold-point tropopause rises by up to 4 km at the storm center. Outside of the eye, N2 increases considerably just above the cold-point tropopause and the tropopause remains near its initial level. A budget analysis reveals that the advection terms, which include differential advection of potential temperature θ and direct advection of N2, are important throughout the upper troposphere and lower stratosphere. These terms are particularly pronounced within the eye, where they destabilize the layer near and above the cold-point tropopause. Outside of the eye, a radial–vertical circulation develops during RI, with strong outflow below the tropopause and weak inflow above. Differential advection of θ near the outflow jet provides forcing for stabilization below the outflow maximum and destabilization above. Turbulence induced by vertical wind shear on the flanks of the outflow maximum also modifies the vertical stability profile. Meanwhile, radiative cooling tendencies at the top of the cirrus canopy generally act to destabilize the upper troposphere and stabilize the lower stratosphere. The results suggest that turbulence and radiation, alongside differential advection, play fundamental roles in the upper-level N2 evolution of TCs. These N2 tendencies could have implications for both the TC diurnal cycle and the tropopause-layer potential vorticity evolution in TCs.

Symmetric Instability in the Outflow Layer of a Major Hurricane

2014 ◽  
Vol 71 (10) ◽  
pp. 3739-3746 ◽  
Author(s):  
John Molinari ◽  
David Vollaro
Keyword(s):  
Potential Temperature ◽  
Outer Edge ◽  
Unstable State ◽  
Upper Troposphere ◽  
Hurricane Ivan ◽  
Equivalent Potential ◽  
Inertial Instability ◽  
Major Hurricane ◽  
Cloudy Region ◽  
Symmetric Instability

Abstract A set of 327 dropsondes from the NOAA G-IV aircraft was used to create a composite analysis of the azimuthally averaged absolute angular momentum in the outflow layer of major Hurricane Ivan (2004). Inertial instability existed over a narrow layer in the upper troposphere between the 350- and 450-km radii. Isolines of potential and equivalent potential temperature showed that the conditions for both dry and moist symmetric instability were satisfied in the same region, but over a deeper layer from 9 to 12 km. The radial flow maximized at the outer edge of the unstable region. The symmetrically unstable state existed above a region of outward decrease of temperature between the cirrus overcast of the storm and clear air outside. It is hypothesized that the temperature gradient was created as a result of longwave heating within the cirrus overcast and longwave cooling outside the cloudy region. This produced isentropes that sloped upward with radius in the same region that absolute momentum surfaces were flat or sloping downward, thus creating symmetric instability. Although this instability typically follows rather than precedes intensification, limited numerical evidence suggests that the reestablishment of a symmetrically neutral state might influence the length of the intensification period.

On the Warm Core of a Tropical Cyclone Formed near the Tropopause

2015 ◽  
Vol 72 (2) ◽  
pp. 551-571 ◽  
Author(s):  
Tomoki Ohno ◽  
Masaki Satoh
Keyword(s):  
Diabatic Heating ◽  
Lower Stratosphere ◽  
Potential Temperature ◽  
Numerical Results ◽  
Forced Flow ◽  
Mature Stage ◽  
Warm Core ◽  
Budget Analysis ◽  
Tangential Wind ◽  
Upper Level

Abstract On the basis of numerical results of a three-dimensional model diagnosed using balance dynamics, a mechanism by which the upper-level warm core of tropical cyclones (TCs) forms is proposed. The numerical results reveal that an upper-level warm core develops when TCs intensify just prior to reaching the mature stage. Potential temperature budget analysis reveals that for the tendency of potential temperature, the azimuthal-mean component of advection is dominant at the upper level of the eye at the mature stage. Sawyer–Eliassen diagnosis shows that tendencies due to forced flow by diabatic heating and diffusion of tangential wind are dominant in the eye and are negatively correlated to each other. The distributions of the diabatic heating in the simulated TC are not peculiar. Therefore, it is unlikely that the heating distribution itself is the primary cause of the flow from the lower stratosphere. The analyses of forced circulations of idealized vortices show that the upper-level subsidence is enhanced in the eye when the vortex is sufficiently tall to penetrate the statically stable stratosphere. This result is deduced because the stronger inertial stability extends the response to the heating of the lower stratosphere and causes upper-level adiabatic warming. Therefore, the upper-level warm core emerges if angular momentum is transported into the lower stratosphere due to processes such as convective bursts. The present analysis suggests that TCs can be even stronger than that expected by theories in which the TC vortex is confined in the troposphere.

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