Abstract: Based on the conventional observation data and the ECWMF 6-hourly reanalysis data with a resolution of 0.25°×0.25°, the paper conducted a diagnostic analysis on the dynamic and thermal conditions of severe sandstorm in Ningxia on Mar 9, 2013. The results show that the main cause of this strong sandstorm is the cold air intrusion which reached cold wave strength. Under the combined effects of strong sensitive, frontogenesis and the upper and low-level jets, strong turbulent mixing occurred in the boundary layer, producing strong winds and dust ground. Before the sandstorm occurrence, the negative values of the sensitive heat flux on surface, the 6 h surface allobaric, the isallobaric wind and the horizontal helicity increased, meanwhile there were significant frontogenesis activities between the middle-lower troposphere and the boundary layer, and the high potential vortex in the upper troposphere with the upper level jet downloaded 2000 gpm to be low-level jet along the isentropic surface. Strong sandstorm appeared in the regions where met the following conditions: first, the increase of the surface sensible heat flux was over 250W·m^-2; second, the center value of the frontogenesis in the lower troposphere reached 20×10^-10 K·m^-1·s^-1; third, the 6h surface allobaric was higher than 8 hPa and isallobaric wind reached 8m·s^-1; at last, the horizontal helicity was lower than -500m²·s^-2.

Key words: strong sandstorm, sensitive heat flux, frontogenesis function, high and low-level jets, isallobaric wind, horizontal helicity