In this study, in situ observations of wind holes at the Ice Valley in Korea and Nakayama in Fukushima, Japan are carried out. Based on the observational results, we conducted a series of numerical model simulations of the wind hole circulation using a zero dimensional model, one-dimensional model along the flow path, and two dimensional model in the vertical cross section to understand the detail of the wind hole circulation.
As a result of the observations and numerical experiments, it is found that: (1) the main driving force of the wind hole circulation is the horizontal pressure gradient force induced by the temperature contrast between outer air and interior talus; (2) the mean wind hole circulation is about 1mm/s and the residence time of air in the tales is about 2 days; (3) cold wind hole circulation of katabatic wind in spring to summer is replace by warm wind hole circulation of anabatic wind in fall to winter; (4) contrasted with the stable and steady katabatic flow in summer, the unstable stratification in winter causes convective overturning of warm and cold air at the Ice Valley with no vegetation along the slope. This seasonal asymmetry of the wind hole circulations acts as a thermal filter which accumulates only the coldness in the talus.
It is interesting to note that the hotter the outer air during spring is, the stronger the freezing katabatic wind is. This mechanism, in part, explains the mysterious ice formation during the hottest season at the Ice Valley and Nakayama.