Figure 1.

Time series of instantaneous horizontal wind velocity u and blown-sand impact count n at the Hasaki Beach [22,31]; the data were recorded for 5 min at a frequency of 1 Hz (a) during intervals without rainfall on 12 January 2005 and (b) after a rainfall event on 25 September 2005. The wind velocity was measured using an ultrasonic anemometer at a height of 0.9 m above the flat ground surface (z_u = 0.9 m). The impact count was measured using UD-101 at z_s = 0.04 m. The horizontal distance between the wind and saltation sensors was 1 m. The median sand grain size d₅₀ of the ground surface at the beach was 0.2 × 10⁻³ m.