Climatological Characteristics Of Severe Convective Weather Affected By Cold Vortices And A Case Study

In this paper, cold vortexes during the time period of 2000-2014 are objectively identified by the NCEP FNL analysis data. The characteristics of cold vortexes climate distribution and influence scope of cold vortexes analyses and climate characteristics of lightning, hail, strong winds, heavy rainfall and other severe convective weather under the influence of cold vort ex are studied. By classified statistical and analytical methods, the results of weather situation and characteristics of physical quantities of different severe convective weather under the influence of cold vortexes have been obtained. Combining with the observation data, a squall line process induced by the cold vortex has been analyzed, learning more about the mechanism of action of the cold vortex to strong convective weather.Research on the distribution of cold vortex climate characteristics: Summer is the most frequent cold vortexes out break season, and inter-monthly cold vortex variation is bimodal, the most occurrence month of cold vortex is May. The distribution of cold vortex radius is the single peak. The radius of cold vortex in warm season(April to September) is small but relatively stable. The monthly variation of cold vortex influence scope is bimodal, and peak area respectively range from May to July and November to January, the most frequently affected area by the cold vortex have seasonal variation. The distribution of cold vortex most frequently region is in the west comparing with winter and spring in the summer and autumn, it reaches the most western position on the June to September and move eastward to the vicinity of 126 ° E.Distribution of severe convective weather under cold vortex: The diurnal variations of strong convective weather under the influence cold vortex are divided into two types, one is unimodal, such as lightning, hail, thunderstorms and windy weather, the other one is bimodal, such as heavy rainfall and TBB. From the spatial distribution of convection weather percentage under influence of cold vortex, Northeast China and eastern Inner Mongolia are the most affected areas. In these areas, hail has the biggest impact f rom cold vortex, while rainfall has the smallest impact. However, more than 70% heavy rainfall days are induced by cold vortex. Moreover, rainfall induced by cold vortex appears to have high values in the region of Jianghuai, which indicate that precipitations in Jianghuai are correlated with cold vortex in the North-East of China.According to the environmental conditions of different convective weathers induced by cold vortex, severe convective weathers, include thunderstorm, hail and strong wind(SC weathers, hereafter), have stronger jet in 200 h Pa and higher intensity of cold vortex in 500 hPa than heavy rainfall weathers(R weathers, hereafter). Meanwhile R weathers have stronger low level jet in 850 hPa, and higher mid- and low-level relative humidity than SC weathers. Also, PWAT and Q850 is larger in R weathers than that in SC weathers. For weather processes with different influence areas, PWAT, 0℃ height and shear between 0 and 6 km differential the most. PWAT is larger inside cold vortex than that in t he area of continuous positive vorticities, which is because the southern transport band of warm moisture air. And the mid-level shear is lager in the area of continuous positive vorticities than that inside cold vortex, which could be attributed to the mid-level strong wind induced by the large pressure gradient in 500 hPa.A process of squall line induced by cold vortex is analyzed and it is found that this process happens under the influence of the northwest jet behind cold vortex and the southwest jet in low-levels. The structure of squall line could be separated into three systems in the horizontal direction, and southern systems have higher intensity than the northern one. For vertical structure, radar echoes of southern systems appear to have an overha nging large reflectivity and are cognizable weak echo region, which are typical features of hail process. In the meantime, the northern system also has some rears reflectivity, but the top height is very rugged. And consider the high air humidity in the mi d-level, it indicates the short time heavy rainfall instead of hail.