Abstract
The Yeongdong region, located east of the Taebaek Mountains, South Korea, often experiences severe windstorms in spring, causing a lot of damages, especially when forest fires spread out rapidly by strong winds. Here, the characteristics and generation mechanisms of the windstorms in the Yeongdong region on 8 April 2012 are examined through a high-resolution Weather Research and Forecasting (WRF) model simulation. In the Yangyang area, the steep descent of the isentropes on the lee slope of the mountain and their recovery farther leeward are seen. Inversion layers and incoming flow in hydraulic jump regime suggest that the hydraulic jump is responsible for the downslope windstorm. In the Jangjeon area, the plume-shaped wind pattern extending seaward from the gap exit is seen when the sea-level pressure difference between the gap inside and the gap exit, being responsible for the gap winds, is large. In the Uljin area, downslope windstorms pass over the region with weak wind, low Richardson number, and deep planetary boundary layer (PBL), making banded pattern in the wind and PBL height fields. This study demonstrates that the characteristics of the windstorms in the lee of the Taebaek Mountains and their generation mechanisms differ depending on local topographic features.
Highlights
There are many meteorological phenomena directly associated with topography, which include mountain/valley winds, downslope windstorms, gap winds, lee waves, lee vortices, cold-air damming, and banner clouds [1]
Lee [17] showed that downslope windstorms in the Yeongdong region on 11 February 1996 are mainly caused by the hydraulic jump mechanism rather than the partial reflection of gravity waves at the tropopause, based on a numerical simulation
The Weather Research and Forecasting (WRF) results and observation both show the elevated inversion layer below a height of ~1 km, and the simulated inversion layer is thicker than the observed inversion layer
Summary
There are many meteorological phenomena directly associated with topography, which include mountain/valley winds, downslope windstorms, gap winds, lee waves, lee vortices, cold-air damming, and banner clouds [1]. Decker and Robinson [10] showed that the downslope windstorm in New Jersey is caused by hydraulic jump or trapped lee waves, using a regime diagram suggested by [16], and partial reflection is not enough to explain the observed wind speed. Lee [17] showed that downslope windstorms in the Yeongdong region on 11 February 1996 are mainly caused by the hydraulic jump mechanism rather than the partial reflection of gravity waves at the tropopause, based on a numerical simulation. Using surface and upper-air sounding data, they analyzed 92 cases with the observed maximum instantaneous wind speed exceeding two standard deviations of the total mean and showed that most of the cases can be explained by the hydraulic jump, partial reflection or critical-level reflection mechanism.
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