Tab. 1

Precipitation process information"

Fig. 1

The terrain height around Helan Mountain and the average precipitation distribution of 20 rainstorm processes at its eastern side (a) and the terrain vertical profile along AB (b, gray shadow, unit: m)"

Fig. 2

Vertical distribution (gray solid line) of specific humidity (a, unit: g·kg-1), potential temperature (b, unit: K), wind speed (c, unit: m·s-1) and average distribution of meteorological elements (black solid line) during individual precipitation of 20 rainstorms at the eastern foot of Helan Mountain"

Fig. 3

Distribution of three type vertical wind field structures were used in the numerical tests: a single layer of uniform east wind (a), low level with wind shear east wind (b), and low level similar to (Ⅱ) but high level with west wind (c)"

Tab. 2

Design of experiments"

Fig. 4

Vertical velocity field (shadow, unit: m·s-1) and potential temperature field (contour line, unit: K) simulated by single-layer uniform-air flow mountain experiments (D1) in different Fr number"

Fig. 5

Vertical velocity field (shadow, unit: m·s-1) and vertical velocity variation at 2 km height on both sides of the mountain (red line, unit: m·s-1) simulated by easterly cross-mountain experiments (D2) with different sizes of wind shear (a: ushear =-8 m·s-1, b: ushear =-10 m·s-1, c: ushear =-12 m·s-1, d: ushear =-15 m·s-1)"

Fig. 6

Temporal variation of vertical velocity (unit: m·s-1) at 3 km altitude by D2 experiments (a: ushear= -10 m·s-1, b: ushear= -15 m·s-1)"

Fig. 7

Simulated precipitation distribution (a, unit: mm) on both sides of mountain under different wind speed (u0) in M1 experiments and cumulative precipitation for the entire simulation period under several specific wind speed conditions (b, unit: mm)"

Fig. 8

Simulated vertical velocity field (shadow, unit: m·s-1) and potential temperature field (contour line, unit: K) at 360 min in M1 (a: u0= -4 m·s-1, b: u0= -7 m·s-1, c: u0= -10 m·s-1, d: u0= -13 m·s-1) experiments"

Fig. 9

Simulated cloud water content (shadow, unit: 10-4 kg·kg-1), flow field (vector arrow, unit: m·s-1) vertical profile at 540 min and accumulated precipitation during 480-600 min (red curve, unit: mm) in M1 experiments (a: u0= -6 m·s-1, b: u0= -7 m·s-1, c: u0= -8 m·s-1, d: u0= -9 m·s-1, e: u0= -10 m·s-1, f: u0= -11 m·s-1)"

Fig. 10

Simulated precipitation distribution (a, unit: mm) on both sides of mountain under different wind speed (ushear) in M2 experiments and cumulative precipitation for the entire simulation period under several specific wind speed conditions (b, unit: mm)"

Fig. 11

Simulated vertical velocity field (shadow, unit: m·s-1) and potential temperature field (contour line, unit: K) at 360 min by M2 (a: ushear= -8 m·s-1, b: ushear= -12 m·s-1, c: ushear= -16 m·s-1, d: ushear= -20 m·s-1) experiments"

Fig. 12

Simulated cloud water content (shadow, unit: 10-4 kg·kg-1), flow field (vector arrow, unit: m·s-1) vertical profile at 540 min and accumulated precipitation during 480-600 min (red curve, unit: mm) in M2 experiments (a: ushear=-9 m·s-1, b: ushear=-11 m·s-1, c: ushear= -13 m·s-1, d: ushear= -15 m·s-1, e: ushear= -17 m·s-1, f: ushear= -19 m·s-1 )"

Fig. 13

Distribution of accumulated precipitation (unit: mm) on both sides of the mountain in the whole period simulated by M3 experiments(u1= -14 m·s-1 and u2 = 5 m·s-1, 10 m·s-1, 20 m·s-1, 30 m·s-1, 40 m·s-1)"

Fig. 14

Simulated cloud water content (shadow, unit: 10-4 kg·kg-1), flow field (vector arrow, unit: m·s-1) vertical profile at 540 min and accumulated precipitation during 480-600 min (red curve, unit: mm) in M3 experiments (u1= -14 m·s-1; u2= 5 m·s-1(b), 10 m·s-1(c), 20 m·s-1(d), 30 m·s-1(e), 40 m·s-1(f) )"