Based on conventional observation data and Doppler weather radar products from Shanxi Datong station, two types of blizzard weather processes in Shanxi (the cold front inverted trough type and the occluded front type, hereinafter referred to as typeⅠand typeⅡ, respectively) had been compared and analyzed. The results show that there were similarities between two types of blizzard weathers: (1) The lowlevel zero velocity line showed obvious “S”shaped curve when precipitation phase was rain or sleet. The change of the zerovelocity line shape and the position of the 0 ℃ layer bright band had obvious indications to phase transition. (2) The mean basic reflectivity factor profiles of the typeⅠand typeⅡsnowstorm drawn by using the 9point average method showed similar characteristics, that was, the intensities of mean basic reflectivity factor profiles ranged from 30 dBZ to 40 dBZ, which could be used to estimate snowfall level and judge the 0 ℃ layer bright band. However, there were obvious differences between the two types of blizzards: (1) For the typeⅠblizzard, it was cold cloud precipitation with deep cold pad. The water vapor channel was cut off by the strong lowerlevel cold air, however, the dynamic uplift caused by the radial convergence of the midlevel southward jet and the northwest air made the snowfall maintain and reach the magnitude of blizzard. While for the typeⅡblizzard, it was warm cloud precipitation and triggered by the warm shear Line. The longterm maintenance of occluded front and south wind jet was the main cause of formation of the typeⅡ blizzard. (2) During the typeⅠblizzard, a clear bright band of 0 ℃ layer appeared and remained for a long time, while for the typeⅡit had no clear bright band of 0 ℃ layer. (3) During the process of the typeⅠblizzard, when the “S” zerovelocity line reversed to a northsouth straight line, it indicated that the lowlevel warm advection was weakened and an easterly damp cold pad was formed. At this time, the precipitation phase changed from rain to snow. During the typeⅡ blizzard process, when the zero velocity line changed from “S” to reverse “S”, it indicated that the cold advection intrusion was obvious. At this time, the precipitation phase changed from sleet to snow. The zerospeed line turned significantly forward again, indicating that the weakening of blizzard was coming to an end.

Based on the hourly precipitation data from June to September of 7 national meteorological stations during 1996-2015 and 63 automatic weather stations during 2008-2015 in Taiyuan, and relative radiosonde and surface observation data, the synoptic patterns of circulation configuration on short-time heavy rainfall days in Taiyuan were classified and the characteristics of key environmental parameters under different patterns were studied. The results show that there were four circulation patterns on 500 hPa during short-time heavy rainfall processes in Taiyuan including cold vortex type, upper trough type, upper trough with subtropical high type and northwest flow type. Short-time heavy rainfalls in Taiyuan always happened under weak CAPE, and in most cases it was less than 1500 J·kg-1, and for all of cold vortex type it was less than 1000 J·kg-1. For northwest flow type, the ΔT850-500 was bigger and there always was stronger static instability and obviously dry layer on 500 hPa. For upper trough with subtropical high type, there always was a higher K index, and mean value of warm cloud thickness was 3576 m, which was significantly thicker than those of the other types. The entire cases of cold vortex type and 85% cases of upper trough type happened under weak vertical wind shear within 0-6 km, 35% cases of upper trough with subtropical high type and northwest flow type occurred under a moderate vertical wind shear condition. Cold vortex type and northwest flow type always had better vapor conditions on 700 hPa than that of 850 hPa. The extreme rainfall more than 70 mm·h-1 occurred under northwest flow type, which had moderate CAPE, strong unstable stratification, weak 0-6 km vertical wind shear, and plenty vapor from low to middle layer with warm cloud thickness more than 3550 m, the cooperation of these environmental parameters had denotative meaning for the strong precipitation efficiency.