Observational study for strong downslope wind event under fine weather condition during ICE-POP 2018

Abstract. A strong downslope wind event under fine weather condition on 13–15 February 2018 was examined by various observational and high resolution reanalysis datasets during the 2018 Winter Olympic and Paralympic games in Pyeongchang, Korea. High spatio-temporal resolution of wind information was obtained by Doppler lidars, automatic weather stations (AWS), wind profiler, and sounding observations under the International Collaborative Experiments for Pyeongchang 2018 Olympic and Paralympic winter games (ICE-POP 2018). This study aimed to understand the possible generation mechanisms of localized strong wind event across high mountainous areas and in the lee side of mountains associated with the underlying large-scale pattern of a low-pressure system (LPS). The spatial distribution of linear trends for surface wind shows different patterns, exhibiting increased trend in the lee side and a persistent one in mountainous areas with the approaching LPS. Surface wind speed was intensified dramatically from ~3 to ~12 m s−1 (gust was stronger than 20 m s−1 above ground) at a surface station in the lee side (named as GWW). However, the mountainous station at DGW site appeared to have a persistently strong wind (~10 m s−1) during the research period. Budget analysis of horizontal momentum equation and local reanalysis data suggests that the pressure gradient force (PGF) derived by adiabatic warming along the downslope and subsequent hydraulic jump in the lee side of mountains was a main factor in the acceleration of the surface wind at the GWW site. Detailed analysis of the retrieved 3D winds reveals that the PGF also dominate at the DGW site, which causes the persistent strong wind that is related to the channeling effect across the valley areas in the mountain range. The observational evidence presented here shows that the different mechanisms in local areas under the same synoptic condition with LPS are important references in determining the strength and persistence of the orographic-induced strong winds under fine weather condition.