Impact of subgrid‐scale processes on eyewall replacement cycle of tropical cyclones in HWRF system

Zhu, Ping; Zhu, Zhenduo; Gopalakrishnan, Sundararaman; Black, Roger W.; Marks, Frank D.; Tallapragada, Vijay; Zhang, Jun A.; Zhang, Xuejin; Gao, Chen

doi:10.1002/2015gl066436

Cited by 24 publications

(13 citation statements)

References 38 publications

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“…The eyewall continued to expand radially outward in time. This eyewall expansion in HWRF idealized simulations was also demonstrated in Zhu et al (). The storm began a period of weakening about 130 h into the simulation.…”

Section: Idealized Casesupporting

confidence: 75%

“…Using simulations from the Hurricane Weather Research and Forecasting (HWRF) model, Zhu et al () showed that the lack of solid‐phase hydrometeors and evaporative cooling from precipitation in the outer rainband region are the likely culprits for not generating SEF. Zhu and Zhu () demonstrated that changing the snow terminal velocity by various factors directly led to the presence or absence of SEF in the Advanced Research Weather Research and Forecasting (WRF‐ARW) model.…”

Section: Introductionmentioning

confidence: 99%

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A Top‐Down Pathway to Secondary Eyewall Formation in Simulated Tropical Cyclones

et al. 2018

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Idealized and real‐case simulations conducted using the Hurricane Weather Research and Forecasting (HWRF) model demonstrate a “top‐down” pathway to secondary eyewall formation (SEF) for tropical cyclones (TCs). For the real‐case simulations of Hurricane Rita (2005) and Hurricane Edouard (2014), a comparison to observations reveals the timing and overall characteristics of the simulated SEF appear realistic. An important control of the top‐down pathway to SEF is the amount and radial‐height distribution of hydrometeors at outer radii. Examination into the simulated hydrometeor particle fall speed distribution reveals that the HWRF operational microphysics scheme is not producing the lightest hydrometeors, which are likely present in observed TCs and are most conducive to being advected from the primary eyewall to the outer rainband region of the TC. Triggering of SEF begins with the fallout of hydrometeors at the outer radii from the TC primary eyewall, where penetrative downdrafts resulting from evaporative cooling of precipitation promote the development of local convection. As the convection‐induced radial convergence that is initially located in the midtroposphere extends downward into the boundary layer, it results in the eruption of high entropy air out of the boundary layer. This leads to the rapid development of rainband convection and subsequent SEF via a positive feedback among precipitation, convection, and boundary layer processes.

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Section: Idealized Casesupporting

confidence: 75%

Section: Introductionmentioning

confidence: 99%

A Top‐Down Pathway to Secondary Eyewall Formation in Simulated Tropical Cyclones

et al. 2018

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“…The importance of radial distance between inner eyewall and outer rainband to SEF was also noted in previous studies of Zhu and Zhu [] and Zhu et al . []. In addition, the frictional updraft in the potential SEF region is markedly weaker and therefore is less able to influence the convection.…”

Section: Discussionmentioning

confidence: 99%

Dynamics and predictability of secondary eyewall formation in sheared tropical cyclones

Zhang

Tao

Sun

et al. 2017

J Adv Model Earth Syst

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This study examines the predictability and dynamics of tropical cyclone (TC) secondary eyewall formation (SEF), eyewall replacement cycles (ERC), and intensity changes under moderate environmental shear through convection‐permitting ensemble simulations. Even with the same environmental shear, the TC intensity changes during formation, rapid intensification, and SEF/ERC can be extremely sensitive to small, unobservable, random initial condition uncertainties, or computer's truncation error due to the chaotic nature of moist convection. Through composite analysis of five ensemble members with similar clear SEF/ERC and diagnostics with a nonlinear boundary layer (BL) model, we identify several key factors in the SEF/ERC process: (1) fast expansion of outer wind fields and changing inertial stability through shear‐induced peripheral convection outside of the primary eyewall, (2) downward building and axisymmetrization of the primary (outer) rainband due to enhanced inertial stability and positive feedback between BL and outer convection, (3) establishment of the secondary eyewall along with moat formation that is facilitated by compensating subsidence from the primary eyewall, and (4) weakening and eventual replacement of the original primary eyewall by the strengthening secondary eyewall. It is also seen from the partial ERC cases that the preexisting rainband can be of great importance to the later development of SEF. Diagnosis with the nonlinear BL model shows that the location and relative strengths of the diagnosed frictional updrafts closely match those in the ensemble simulation of the ERC case, suggesting that the boundary layer convergence substantially influences the location of the convection in both eyewalls there.

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“…The secondary eyewall, which plays an important role in TC internal dynamical processes, has been routinely studied and modeled using the idealized axisymmetric vortex framework (e.g., Houze et al, ; Kepert, ; Montgomery, ; Shapiro & Willoughby, ; Willoughby et al, ; Zhu et al, ). In the idealized axisymmetric vortex framework, a theory of the eyewall replacement cycle (ERC) has been formally proposed by Willoughby et al (), which demonstrates that any eyewall will contract in the presence of annular convective heating.…”

Section: Introductionmentioning

confidence: 99%

Effects of Asymmetric Secondary Eyewall on Tropical Cyclone Evolution in Hurricane Ike (2008)

Zhang

Perrie

2018

Geophysical Research Letters

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The secondary eyewall plays an important role in tropical cyclone evolution and intensification and is routinely assumed to be axisymmetric. A unique opportunity to investigate the characteristics of the secondary eyewall in two dimensions is provided by the high spatial resolution (about 1 km) sea surface winds that were observed by spaceborne synthetic aperture radar over Hurricane Ike (2008). Here we extract the asymmetric characteristics using our Symmetric Hurricane Estimates for Winds model and analyze the related hurricane evolution by comparisons with aircraft measurements. Compared to the classic eyewall replacement cycle theory, our investigation finds that the primary eyewall did not weaken and the secondary eyewall did not shrink over a period of more than 30 hr. We suggest that the reason for this persistence is that a boundary layer inflow pathway is provided by the relatively low winds in the asymmetric secondary eyewall area, as observed by synthetic aperture radar.

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Impact of subgrid‐scale processes on eyewall replacement cycle of tropical cyclones in HWRF system

Cited by 24 publications

References 38 publications

A Top‐Down Pathway to Secondary Eyewall Formation in Simulated Tropical Cyclones

A Top‐Down Pathway to Secondary Eyewall Formation in Simulated Tropical Cyclones

Dynamics and predictability of secondary eyewall formation in sheared tropical cyclones

Effects of Asymmetric Secondary Eyewall on Tropical Cyclone Evolution in Hurricane Ike (2008)

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