Observational study of surface wind along a sloping surface over mountainous terrain during winter

Abstract

The 2018 Winter Olympic and Paralympic Games will be held in Pyeongchang, Korea, during February and March. We examined the near surface winds and wind gusts along the sloping surface at two outdoor venues in Pyeongchang during February and March using surface wind data. The outdoor venues are located in a complex, mountainous terrain, and hence the near-surface winds form intricate patterns due to the interplay between large-scale and locally forced winds. During February and March, the dominant wind at the ridge level is westerly; however, a significant wind direction change is observed along the sloping surface at the venues. The winds on the sloping surface are also influenced by thermal forcing, showing increased upslope flow during daytime. When neutral air flows over the hill, the windward and leeward flows show a significantly different behavior. A higher correlation of the wind speed between upper- and lower-level stations is shown in the windward region compared with the leeward region. The strong synoptic wind, small width of the ridge, and steep leeward ridge slope angle provide favorable conditions for flow separation at the leeward foot of the ridge. The gust factor increases with decreasing surface elevation and is larger during daytime than nighttime. A significantly large gust factor is also observed in the leeward region.

摘要

2018 冬季奥运会和残奥会将于 2,3 月在韩国平昌举行. 本文使用地面风资料检验 2,3 月平昌两个室外场馆地面风场和坡面地表阵风的特性. 由于这两个室外场馆位于复杂的山区地形中, 近地面风场在大尺度环流和局地流场共同影响下形成错综复杂的结构. 2,3 月山脊高度上的主导风是西风, 然而在场馆坡面上观测到风向发生明显偏转. 坡面上的地面风场还受到山区热力强迫日变化影响, 表现为白天上坡风增强. 在中性气流过山时, 迎风面和背风面流场有一显著差异, 即: 迎风区高低层风速相关性比背风区更强. 强天气尺度风, 较窄的山脊宽度和较陡的背风区坡度都是山脊脚下背风区气流发生分离的有利条件. 随着地面海拔降低, 阵风系数增加, 且白天数值大于夜间. 在背风区能观测到阵风系数的一个大值区.