• Atmosphere
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• v.34 no.4
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• pp.397-415
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• 2024

Reported tornado event occurred in Dangjin, Chungcheongnam-do at 0650~0730 UTC on 15 March 2019 was examined using Weather Research and Forecasting model with four nested domains (dx = 5, 1, 0.2, and 0.05 km). From synoptic analysis in ERA5 reanalysis data, eastward moving upper-level trough was developed rapidly in the Yellow Sea. Strong tropopause folding with Potential Vorticity Unit (PVU) higher than 1.5 PVU moved downward to 600-hPa level in mid troposphere following the trough over the location of tornado event. Under this large-scale background condition, surface front developed very intensively in the west coast of Korea along with strong low-level jet and moisture band at 850-hPa level. In domain 2, the maximum Bulk wind shear at Dorido point was 12.86 m s^-1. Cold front evolved to be a comma cloud with upper-level trough and strong bulk vertical shear near Dangjin, which include eastward moving gust front revealed as a strong horizontal temperature gradient and convergence near the surface. In domains 3 and 4, the local maximum value of the simulated vertical vorticity (24 × 10^-2 s^-1) with strong updraft (8.18 m s^-1) near the observed tornado event along with the surface gust front was found to be a possible area for tornadogenesis from the x-z and time-z cross-sections near the simulated tornado event. In the vorticity budget analysis, the local maximum of vertical vorticity during this event was generated significantly by tilting and stretching forcings.

• Wind and Structures
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• v.19 no.1
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• pp.89-111
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• 2014

The dynamics of a tornado-like vortex with touching down is investigated by using the LES turbulence model. The detailed information of the turbulent flow fields is provided and the force balances in radial and vertical directions are evaluated by using the time-averaged axisymmetric Navier-Stokes equations. The turbulence has slightly influence on the mean flow fields in the radial direction whereas it shows strong impacts in the vertical direction. In addition, the instantaneous flow fields are investigated to clarify and understand the dynamics of the vortex. An organized swirl motion is observed, which is the main source of the turbulence for the radial and tangential components, but not for the vertical component. Power spectrum analysis is conducted to quantify the organized swirl motion of the tornado-like vortex. The gust speeds are also examined and it is found to be very large near the center of vortex.