The Circulation Dynamical Structure of a Severe Dust Storm Process in Northwest China

The observed data and the NCEP/NCAR 1°× 1° 6-hour reanalysis data were used to analyze the circulation dynamical structure of dust storm processes during April 9—11, 2006 in Northwest China. The results show that upper jet flow, relative vorticity, pressure vertical velocity differently matched in various periods of dust storm development, and their values and spatial distributions were well-corresponding to the forming, developing and decaying of dust event. In strong stage of dust storm, the asymmetric structure of relative vorticity was enhanced. There was a couter-circulation at the lower side of the centre of the upper jet flow, and dust storms mainly occurred in the area of 37° N to 44° N, just the downdraught region of the couter-circulation.