Vertical Eddy Diffusivity Parameterization Based on a Large‐Eddy Simulation and Its Impact on Prediction of Hurricane Landfall

Li, Xin; Pu, Zhaoxia

doi:10.1029/2020gl090703

Cited by 12 publications

(8 citation statements)

References 39 publications

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“…Although the finest grid spacing of 1 km in this study is sufficient to represent a wide range of dynamical phenomena in TCs down to the mesoscale, it is still one to two orders of magnitude larger than the large eddies that mix the physical quantities in the turbulent PBLs (e.g., Rotunno et al, 2009;Li & Pu, 2021;Chen & Bryan, 2021). Because of this scale gap, the turbulent mixing of the physical quantities in the PBL needs to be fully parametrized.…”

Section: Overview Of the Pbl Parametrizations For The Simulationsmentioning

confidence: 99%

The vortex structure and near‐surface winds of Typhoon Faxai (2019) during landfall. Part II: Evaluation of WRF simulations

Takahashi,

Nolan,

McNoldy

2024

Quart J Royal Meteoro Soc

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This two‐part study presents a comprehensive analysis of (1) the vortex structure, (2) the inner core planetary boundary layer (PBL) wind profile, and (3) the overland surface winds of Typhoon Faxai(2019) during landfall observationally (Part I) and in high‐resolution Weather Research and Forecasting Model (WRF) simulations (Part II). Part II presents a framework for evaluating the wind field in the WRF simulations of Typhoon Faxai (2019) by comparing them with the observations presented in Part I. First, WRF simulations with two different surface roughness tables are presented. The simulation with the default table in WRF is shown to largely overestimate the surface wind speed. The overestimation is largely mitigated by using larger based on the climatology for urban and forest areas in Japan. Next, using the modified table, WRF simulations with three different PBL parametrizations, namely, Mellor–Yamada–Janjić, Yonsei University, and Mellor–Yamada–Nakanishi–Niino schemes are presented, and their impacts on the simulated vortex structure, inner core PBL wind profile, and overland surface winds are evaluated. In particular, the simulated surface winds are in good agreement with the observations outside the inner core of Typhoon Faxai. However, during the passage of the eyewall, the maximum surface winds are underestimated in the simulations. We show that the underestimation of the inertial stability, associated with the excessively large inner core of Typhoon Faxai in the simulations, led to the overestimation of the eyewall PBL jet height. This, in turn, caused the underestimation of the peak surface winds, as based on the empirical model of the wind reduction factor proposed in Part I.

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Section: Overview Of the Pbl Parametrizations For The Simulationsmentioning

confidence: 99%

The vortex structure and near‐surface winds of Typhoon Faxai (2019) during landfall. Part II: Evaluation of WRF simulations

Takahashi,

Nolan,

McNoldy

2024

Quart J Royal Meteoro Soc

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“…Although the WRF physics was from a 2013 version, key physics for rolls is the PBL parameterization, which in our case was YSU. We are confident that YSU is viable for our analysis since it continues to be used in WRF, at grid resolutions similar to that used herein, to study small-scale vortices in HBLs (e.g., Wu et al [42]) as well as for realistic representations of tropical cyclone (TC) surface wind fields [43][44][45]. Cloud physics was modeled using WSM6 6-class microphysics with graupel [46].…”

Section: Archived Weather Research and Forecasting (Wrf) Simulationmentioning

confidence: 99%

Airstream Association of Large Boundary Layer Rolls during Extratropical Transition of Post-Tropical Cyclone Sandy (2012)

Schiavone

2023

Meteorology

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Better understanding of roll vortices that often occur in the tropical cyclone (TC) boundary layer is required to improve forecasts of TC intensification and the granularity of damaging surface winds. It is especially important to characterize rolls over a wide variety of TCs, their environments, and TC development phases. Boundary layer rolls have been observed in TCs since 1998, but only recently in a TC during its extratropical transition phase. The work reported herein is the first to analyze how boundary layer rolls are distributed among the extratropical features of a transitioning TC. To this end, routine and special operational observations recorded during landfalling Post-tropical Cyclone Sandy (2012) were leveraged, including radar, surface, rawinsonde, and aircraft reconnaissance observations. Large rolls occurred in cold airstreams, both in the cold conveyor belt within the northwestern storm quadrant and in the secluding airstream within the northeastern quadrant, but roll presence was much diminished within the intervening warm sector. The large size of the rolls and their confinement to cold airstreams is attributed to an optimum inflow layer depth, which is deep enough below a strong stable layer to accommodate deep and strong positive radial wind shear to promote roll growth, yet not so deep as to limit radial wind shear magnitude, as occurred in the warm sector.

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“…These describe turbulent mixing and related fluxes in terms of the vertical gradient of the mean quantities, which control the feedbacks involving momentum, moisture, and heat between the surface and atmosphere. Numerical and observational studies have sought to constrain the turbulent mixing parameterizations in a numerical weather prediction (NWP) model for forecasting both TC track and intensification events over the ocean [6][7][8][9][10][11][12][13][14][15][16]. For example, Nolan et al [17], Kepert [18], and Zhang et al [19] found that improved estimations of the eddy diffusivity coefficient in the hurricane boundary layer are beneficial for hurricane prediction over the ocean.…”

Section: Introductionmentioning

confidence: 99%

Vertical Eddy Diffusivity in the Tropical Cyclone Boundary Layer during Landfall

Chen

2022

Atmosphere

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This study investigated surface layer turbulence characteristics and parameters using 20 Hz eddy covariance data collected from five heights with winds up to 42.27 m s–1 when Super Typhoon Maria (2018) made landfall. The dependence of these parameters including eddy diffusivities for momentum (Km) and heat (Kt), vertical mixing length (Lm), and strain rate (S) on wind speed (un), height, and radii was examined. The results show that momentum fluxes (τ), turbulent kinetic energy (TKE), and Km had a parabolic dependence on un at all five heights outside three times the RMW, the maximum of Km and S increased from the surface to a maximum value at a height of 50 m, and then decreased with greater heights. However, Km and S were nearly constant with wind and height within two to three times the RMW from the TC center before landfall. Our results also found the |τ|, TKE, and Km were larger than over oceanic areas at any given wind, and Km was about one to two orders of magnitude bigger than Kt. The turbulence characteristic and parameters’ change with height and radii from the TC center should be accounted for in sub-grid scale physical processes of momentum fluxes in numerical TC models.

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Vertical Eddy Diffusivity Parameterization Based on a Large‐Eddy Simulation and Its Impact on Prediction of Hurricane Landfall

Cited by 12 publications

References 39 publications

The vortex structure and near‐surface winds of Typhoon Faxai (2019) during landfall. Part II: Evaluation of WRF simulations

The vortex structure and near‐surface winds of Typhoon Faxai (2019) during landfall. Part II: Evaluation of WRF simulations

Airstream Association of Large Boundary Layer Rolls during Extratropical Transition of Post-Tropical Cyclone Sandy (2012)

Vertical Eddy Diffusivity in the Tropical Cyclone Boundary Layer during Landfall

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