Analysis of the Occurrence Mechanism of a Strong Sandstorm Based on Potential Vorticity

Based on the observational data, NCEP 1°×1° reanalysis data and potential vorticity theory, the occurrence mechanism of a strong sandstorm occurring in Inner Mongolia during March 14-15 was studied. The results show that the large potential vortex area in the upper troposphere moved eastward and downward, and a structure similar to a "funnel" appeared;the cyclone moved eastward and developed;the high potential vortex region always matched the region where the cyclone developed;the development of the cyclone was closely related to the cold air activity, and there was an obvious interaction between high-and low-altitude systems. The potential vorticity at 500 hPa had obvious significance for the influencing system of this sandstorm. The 0.5 PVU contour line can be used as the boundary of sandstorm weather area. On the potential temperature profile, the occurrence process of this sandstorm was the process of the expansion of cold air from high latitudes to low latitudes. When the high-value potential vorticity system slide along the isentropic surface, the lower vertical vorticity increased due to the increasing slope of the isentropic surface and the conservation of potential vorticity, leading to the development of the surface cyclone circulation and the enhancement of wind speed, and further causing the occurrence of this sandstorm.