Dependence of drifting snow saltation lengths on snow surface hardness

Drifting snow experiments were conducted in a cold wind tunnel at a constant temperature of −15 °C to investigate saltation lengths of snow particles over loose and hard snow surfaces. Vertical mass flux of falling snow particles to the snow surface was measured by a box-type snow collector, which was composed of ten metallic boxes, set at the downwind end of the test section. Saltation lengths were calculated from the distributions of the falling mass flux along the snow collector. altation length over loose snow surfaces increased from 8 to 15 cm with increasing wind velocity from 6 to 15 m s−1. Mean saltation length over hard snow surfaces increased from 40 to 140 cm with increasing wind velocity from 5.5 to 8 m s−1. Mean saltation length over hard snow surfaces was several times as large as that over loose snow surfaces for the same wind velocity. Saltation length distributions were also obtained from analyses of the falling mass flux distributions. Saltation length distributions were shown as exponential functions of length in previous studies for loose snow surfaces. Present results showed that saltation length distributions over hard snow surfaces were well approximated by log-normal distributions.