关键词: 暴雪, 流型配置, 急流, 倾斜结构, 降水相态

Abstract:

Using the conventional meteorological data and NCEP reanalysis data, the heavy snow process in the middle of Shanxi Province on 19 April 2013 was analyzed. The results show that the co-existence of plateau trough on 500 hPa, low vortex shear line at low level, ground return airflow and Hetao cyclone provided advantageous flow pattern configuration for snowstorm. The southwest jet(SWJ) on 700 hPa, the southeast jet (SEJ) on 850 hPa and the eastly jet (EJ) on 925 hPa provided the strong water vapor transport and supplement together. The coupling of the northwest jet (NWJ) on 500 hPa and northeasterly severe airflow on 850 hPa, the positive vorticity transport at high level, the tilt vertical structure of lower-level convergence and upper-level divergence made ascending motion enhancement and triggered the release of unstable energy at low level, which led to occurrence of the snowstorm. The change of low level and near surface temperature, the drop of 0 ℃ level height, increase of  inversion layer depth and vertical wind shear were important indexes to judge the change of precipitation phases and enhance of snowfall intensity during the process.

Key words:  heavy snow , configuration of flow pattern, jet, inclined structure, precipitation phases