TRAJECTORY ANALYSES OF THE DUSTSTORMS OVER EAST ASIA

The transports of dust are calculated using 3-dimensional(3-D)trajectory method for three cases of duststorms inthe terrain-following coordinate system,and the synoptic processes are also discussed for each case.The case of 17—20April 1980,a severe duststorm was associated with the rapid development of a cyclone over the Mongolia Plateau.Thedust moved from west to east across several deserts,formed a typical dust path in spring.The other two were weaker andthe dust was triggered by the strong wind behind the cold front from northwest or north.Because the vertical velocity isconsidered in 3-D trajectory analysis,trajectories calculated should better reveal the transport rule of the dust particlesand the results seem to be more consistent with the synoptic processes.The trajectory analysis on the 2-D isobaric sur-faces is simpler but can be used only in the conditions with weak vertical wind shear and weak vertical velocity.The dif-ference of trajectories at lower levels between two methods may be caused by the different treatment of orography.