(a)

(b)

(c)

(d)

Figure 6: Meteorological control of the Sahara dust transportation (2.5 degrees by 2.5 degrees): (a) Frequency of dust aerosols occurrence overplotted with horizontal wind, (b) averaged dust layer top height (AGL), (c) wind speed and direction (1000 mb~850 mb), and (d) vertical velocity (1000 mb~850 mb).