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.

 A continuous rainstorm event in the middle of Shanxi Province during 1-3 August 2015 was analyzed by using meteorological observations and NCEP/NCAR reanalysis data. Based on the test of ECMWF ensemble forecast products, the joint probability method was used to improve the ensemble forecast of rainstorm. The results are as follows: (1) The precipitation was characterized obviously by convection in this event, which could be divided into two stages. The first stage was the sudden rainstorm in the front of the cold front. In the second stage, the heavy rainfall was caused by the regional strong convective weather, which was affected by the high trough, the low shear line, and the surface cold front. (2) The strong upward motion caused by the convergence of the lower level made many mesoscale convective cloud clusters merge and develop continually, which resulted in rainstorm directly. In the first stage, the convergence layer at the middle and low level was deeper, the suction effect at high level was stronger, and the precipitation rate was greater. In the second stage, the dynamic and energy disturbances at the lower layer were more obvious, and the precipitation area was more concentrated. (3) Mesoscale baroclinic diagnosis showed that, in the first stage, the convergence and frontogenesis of the wet Q-vector at the lower layer increased many times and caused the convective motion stronger and the range larger, and formed many rain peaks of the precipitation. While in the second stage, the baroclinic development of mesoscale system was stronger, but the thickness of instability decreased, therefore the precipitation intensity decreased. (4) The improved ensemble forecast product of the joint probability showed that the range of high probability coincided with the center of rainstorm.

Based on the surface and radiosonde observation data, Doppler weather radar data of Shanxi Province from 2014 to 2017 and reanalysis data of NCEP/NCAR, the rain-to-snow transformation processes were classified and analyzed in winter half year in Shanxi Province, and the effect of surface air temperature on transformation of precipitation phases was discussed, then the precursor information of precipitation phase transition was extracted. The relationship between snowfall and snow depth increment for snowfall processes was statistically analyzed, and the prediction indicators of snow depth were refined. Finally, two rain-to-snow processes from 23 to 24 November 2015 and 21 to 22 November 2016 were analyzed comparatively in order to reveal physical mechanism of precipitation phase transition. The results are as follows: (1) The rain-to-snow transformation process was the most in November in Shanxi Province, and followed by February. As an indicator of precipitation phase change, the surface air temperature was related to climatic and weather (such as the intensity and moving path of cold air) characteristics, geographic location, etc. (2) The ratio of snow depth increment and snowfall was about 0.68 cm·mm-1 in winter half year in Shanxi, and it increased with the decrease of temperature, so it had obvious temporal and spatial differences with the change of month, latitude and altitude. (3) During the change of rain to snow, the proportion of snow-ice layer thickness to total cloud layer increased with the cooling in lower layer of troposphere and the falling path of solid condensate in cloud shortened, which reduced the melting probability of solid condensate, and resulting in the change of phases.

Based on conventional observation data，NCEP reanalysis data，satellite images and radar mosaic products，and combined with WRF mesoscale simulation，the severe convective weather which occurred in the south of Shanxi on 22 May，2013 was analyzed． The results show that during this weather process，lasting transport of positive vorticity advection over Hetao area played a significant role in formation，maintenance and development of the cut － off vortex on 500 hPa level． Both the low － level cold advection from the front and more stronger warm advection from the back made the vortex develop continually，and excited isolated cloud clusters nearby． The vertical structure with high － level divergence and low － level convergence above the cloud clusters made the upward motion strengthen continuously． Consequently，the isolated cloud clusters maintained and developed． These meso － and meso － scale clusters were the direct cause leading to this severe convective weather． The dry frontogenesis caused by surface continuous strengthening of water vapor from the sea at the back of high pressure system and the invading of dry air at the front of ridge，was an important triggering mechanism of the strong convective weather． From the radar mosaic products of composite reflectivity，this process resulted from the development and merging of convective cells． The evolution of these cells went through a process from convective cell，merging，ribbon echo，bow echo to weakening and vanishing ，and the whole process was divided into two stages，when the area，intensity and moving speed of echoes were different，the characteristics of convective weather were different too． Obvious differences among three types during this process existed in temperature and humidity profiles and environmental parameters，which could be served as judging the severe convective weathers．