Abstract:

On the basis of snowfall data from 1990 to 2009, the weather chart, the MICAPS data and the NCEP reanalysis data, backflow heavy snowfall cases in the North China were analyzed and its basic characteristics were summarized. The situation of backflow heavy snowfall and physical features in upper and lower levels at Langfang station and its upstream stations were diagnosed, and some forecast indexes were selected. The results show that the 500 hPa circulation and ground patterns can be respectively divided into two types, i.e. the two troughs and one ridge type and the multi-wave type. It appears “high north and low south” or “northeast high and southwest low” in the east of Asia-Europe on the ground map. The mean intensity at the center of high pressure reaches 1045.5 hPa. The upstream wind direction of ground wind along Langfang is north to East, namely in the west coast of the Bohai sea. The heavy snowfall will happen when the wind speed exceeds 5 m·s^-1.

Key words: Backflow, Heavy snow, Prediction index