Study of the Boundary Layer Structure of a Landfalling Typhoon Based on the Observation from Multiple Ground-Based Doppler Wind Lidars

Shi, Wenhao; Tang, Jie; Chen, Yonghang; Liu, Qiong; Liu, Tongqiang

doi:10.3390/rs13234810

Cited by 4 publications

(5 citation statements)

References 40 publications

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“…The results are consistent with the comparison of average diurnal patterns between typhoon and nontyphoon cases, as shown in Figure 2. Besides, the observed wind surge accompanying by the dramatically enhanced turbulent intensity during the typhoon landfall is similar to previous studies using ground‐based remote sensing measurements (Shi et al., 2021; Xia et al., 2021).…”

Section: Resultssupporting

confidence: 89%

Downward Momentum Flux: An Important Mechanism of Typhoon Maintaining Ground Destructive Force

Lan

Xie

et al. 2023

JGR Atmospheres

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Under the background of global climate change, typhoons have been attracting increasing attention due to their extraordinary destructive potential and great impact on the coastal areas of the South China Sea. Although the risk of strong winds related to typhoons has long been of interest, less is known about the underlying mechanism responsible for the severe near‐surface winds. Using eddy covariance data collected at four different heights on a 365‐m meteorological tower located in a coastal region, the characteristics of the convective typhoon boundary layer and the associated turbulence structures are compared with their counterparts in the “textbook” dynamically unstable boundary layer. In the convective typhoon boundary layer, bulk wind shear predominates the generation of mechanical turbulence, enhancing the vertical correlation between vertical layers. The spectral analysis highlights the salient features of turbulent structures under the convective typhoon boundary layer, confirming that the gust disturbance with the nondimensional frequency ranging from 0.003 to 0.3 modulates not only turbulent transports but also the horizontal flow. Such gusts with reduced phase difference enhance the downward momentum transport, mainly responsible for the maintenance of the strong near‐surface winds during typhoon landfalls.

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Section: Resultssupporting

confidence: 89%

Downward Momentum Flux: An Important Mechanism of Typhoon Maintaining Ground Destructive Force

Lan

Xie

et al. 2023

JGR Atmospheres

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“…However, the magnitude was much smaller than that reported by using sodium radar measurements [49]. The TKE was almost constant at a distance of 2-3 times the RMW before landfall, while the TKE increased with decreasing distance to the typhoon center found in the meteorology radar from Shi et al [50] before Typhoon Maria's landfall. There still needs to be more turbulence observations and to couple the remotely sensed results to verify the process under extreme wind conditions.…”

Section: Conclusion and Discussionmentioning

confidence: 54%

“…Momentum fluxes obtained by the EC method are plotted as a function of u n at the five measurement levels (10,30,50,70, and 110 m) on the two towers during Typhoon Maria (Figure 9a). |τ| values at all heights exhibited a clear parabolic trend with u n , and at low-moderate u n (<30 m s −1 ), |τ| initially increased up to 22 m s −1 , at which point |τ| was 11 m −1 s −2 , then slowly decreased with u n increasing further (>30 m s −1 ).…”

Section: Variations In Momentum Fluxes and Turbulent Kinetic Energy W...mentioning

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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“…Because measurements obtained using anemometers typically have the highest accuracy of all wind observation instruments, anemometer-measured data are generally regarded as "true" values. In recent years, doppler wind lidar (DWL) has been increasingly adopted for performing observations of aerodynamic characteristics under typhoon conditions (Chen et al, 2023; T. T. Li et al, 2023;Shi et al, 2021). As a portable remote sensing device with high spatial and temporal resolutions, good anti-interference capability, and easy and rapid deployment, the accuracy of DWL-measured winds has been proven to be high under typhoon conditions (Tang et al, 2022(Tang et al, , 2023.…”

Section: Introductionmentioning

confidence: 99%

A Comparative Study on Wind Profiles and Surface Aerodynamic Parameters of Typhoons Over Coastland and Coastal Sea

Tang,

Wang,

et al. 2024

JGR Atmospheres

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Understanding the aerodynamic characteristics of landfalling typhoons is of great importance for both wind engineering and meteorology. This study comparatively investigated the near‐surface wind profiles and aerodynamic parameters over coastland and coastal sea areas using typhoon observational data collected by Doppler wind lidars and wind tower anemometers during the passage of 15 typhoons that made landfall over China during 2009–2020. Specifically, the three surface aerodynamic parameters of roughness length, friction velocity, and drag coefficient (Cd) were obtained using the logarithmic law wind profile method. Results showed that the near‐surface wind profiles became much closer to the power law wind profile with increase in wind speed. The values of roughness length and friction velocity over the coastal sea were found to exceed those over coastland areas when the 10‐m wind speed (U(10)) was larger than 18 m s−1. The critical wind speed at which Cd peaks over the coastal sea was found to be 24 m s−1. There are two peaks in the variation of Cd with U(10) under the condition of onshore wind over the sea, which has never been reported in previous observational studies. Finally, a formula for Cd was proposed to describe the variation in Cd with U(10) under the condition of onshore wind over land, which is expected to be applied in the typhoon surface layer scheme to improve numerical simulation of landfalling typhoons.

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Study of the Boundary Layer Structure of a Landfalling Typhoon Based on the Observation from Multiple Ground-Based Doppler Wind Lidars

Cited by 4 publications

References 40 publications

Downward Momentum Flux: An Important Mechanism of Typhoon Maintaining Ground Destructive Force

Downward Momentum Flux: An Important Mechanism of Typhoon Maintaining Ground Destructive Force

Vertical Eddy Diffusivity in the Tropical Cyclone Boundary Layer during Landfall

A Comparative Study on Wind Profiles and Surface Aerodynamic Parameters of Typhoons Over Coastland and Coastal Sea

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