The dynamic diagnosis on developing mechanism of two low vortex snowstorm processes in Liaoning in early 2015

By using NCEP reanalysis data, analyzed the formation mechanism of two low vortex snowstorm processes by the angle of dynamics in Liaoning area in early 2015. The results showed that: the formation and strengthening of low vortex was the direct cause of two snowstorm. The development reason of low vortex in the two snowstorm processes exist differences. Convergence in low troposphere level had positive contribution for the development of low vortex in “2.16” snowstorm processes. Vertical vorticity transport had positive contribution for the development of low vortex in “2.25” snowstorm processes. Through 500 hPa positive vorticity advection developing, upward motion had enhanced, leading to increased of the convergence near 850 hPa height, it could cause to the development of positive vorticity,that is the developing mechanism of “2.16” snowstorm processes. The strong upward movement leading to vertical vorticity transport was the developing mechanism of “2.25” snowstorm processes. The cold advection in trough of 500 hPa level was the heat causes of the developing mechanism of “2.16” snowstorm processes. The warm advection in low troposphere level was the heat causes of the developing mechanism of “2.25” snowstorm processes.