Abstract:A model simulation of“2002.3”sandstorm by nonhydrostatic mesoscale model MM5 is analyzed in an effort to study the
mechanism of the sandstorm.The diagnosis of convective momentum transport (CMT) shows that, at every level,the maximum bud-
get residualXof the horizontal momentum is located behind the trough,whichXstrengthened the northwest cold air flow to south.
The angle between Xand Vwas smaller than 90°behind the trough,that means accelerated northwest cold air flow
to south and it is in favor of deepening the trough and moves to southeast. At the level of 300hPa, kinetic ener-
gy transferEhad clear belt distribution, and the maximum centers ofEwas mainly located on the each side of upper Jet, that
showed the upper Jet played a very important role in kinetic energy transfer. The distribution character of vorticity and divergency is
consistent with the trough that trigged the sandstorm.Model trajectories analyses indicated that there was airstream in the trough at
the upper level of 300hPa, and it flow to southeast at the level of 500hPa, there exist mountain-plain circulation to the north of the
Plateau. The sand transport routing can be determined by superimposing the sand concentration over the trajectories, theoretically,
but the forecasting of the trajectories is difficult at now.