Analysis of a Record Heavy Snowfall Event in North China

In this paper, the authors discussed a record heavy snowfall event that occurred in North China in November of 2009. The conventional and unconventional data including satellite images and Doppler radar and automatic weather station (AWS) observations were utilized. The related physical quantities including the frontogenesis function, the kinetic energy budget and moisture flux were computed and the formation mechanism for the heavy snowfall was investigated. Major conclusions are as follows:(1) The returning flow accompanied with disturbances intensified the moisture transport and horizontal convergence in North China. The "inverted trough" to the south of the cold high pressure in the lower troposphere also played an important role in the formation of the heavy snowfall. (2) Radar data revealed clearly that a convergence zone maintained stably to the southwest of Shijiazhuang City, where convective cloud clusters developed continuously and directly led to the formation of heavy snowfall. (3) In the T-lnp diagrams of sounding data at Taiyuan and Xingtai, the frontal zone with the inversion layer could be seen clearly, which was favorable for the accumulation of unstable energy. However, the "warm nose" did not exist, which explains why only the snowfall occurred and there existed no freezing rain. (4) Based on the above discussions, a conceptual model for North China heavy snowfall was proposed.