Abstract: In this paper, the cold wind momentum transfer characteristics at a large scale in northwest China are on analyzed using the NCEP reanalysis data. The results show that the momentum transfer during the wind process is caused by convergence and divergence of air at high and low height field. The convergence takes place at the entrance of jet with strong pressure at surface pressure field. as a compensation, updrafts appear at the downstream of the jet , and strong wind occurs generally in the south of jet , where vertical velocity of the whole layer is close to zero. The velocity in the jet stream has an obvious reverse when the strong wind occurs, and sinking airflow lands earlier. Its speed is smaller than the cold wind, but it's longer. The potential vorticity has a downward transportation after a cold vortex area, meaning an invasion of high potential vorticity. The strong northwest currents after upper trough can cause sustained wind, and the upper through is main reason of momentum transfer. The research results can enhance understanding on momentum characteristics, and gather experience for accurate prediction of strong wind.

Key words: strong wind, example analysis, momentum transmission