Abstract:Based on the observed data and output data from MM5, the terrain effect on the blizzard process in central and south of Hebei Province from November 10 to 11 in 2009 is analyzed. The results show that there is a downward motion on the north side of the trumpet shaped terrain, and an upward motion on the south side; the eastward flow has been brought together due to the role of the trumpet shaped terrain, the terrain effect exists under the 800 hPa and an upward motion is generated. Vertical profiles show that the low level upward motion generated by terrain penetrates through the inversion layer, and merged with upward streams caused by westerly trough, thus strengthening the vertical upward movement. The northeast flow encountered Taihang Mountains is divided into two flows, a flow sinking in the piedmont, and the other flow ascending before the cold air heap and gradually forms a piedmont circulation of cold air sinking branch, indicating accumulation of cold air in the piedmont. This may be the main reason for snowfall center occurring generally in the plains and not in the hill.