湖北冷季高架雷暴天气分类及环境参数特征分析

Environment Parameter Characteristics of Different Types of Cold Season Elevated Thunderstorms in Hubei

关键词:  冷季  高架雷暴  环境参数  箱线图

Key words:  cold season  elevated thunderstorm  environmental parameter  boxplots

摘要:

利用常规观测资料、加密地面自动站、闪电定位仪和ERA5再分析资料，将2011—2020年湖北冷季91次高架雷暴事件，按照形成机制分为雷雨型、强对流型和雷打雪型3类，并细致归纳了3类事件的时空分布特征、大气环流背景及关键环境参数等特征。(1) 湖北冷季高架雷暴雷雨型最多，强对流型次之，雷打雪型最少。3类型存在明显的时空分布差异，雷雨型主要发生在秋末冬初(11月)和冬末初春(1—2月)，强对流型及雷打雪型常出现在早春2月，3月基本以强对流型为主。(2) 低槽冷锋、850 hPa切变线及低空西南急流是冷季高架雷暴发生的有利环流背景，近地面为稳定的冷气团控制，逆温明显，西南低空急流沿着锋面逆温层以上的850 hPa附近触发抬升，水汽、上升运动及不稳定层结均出现在850 hPa以上。雷雨型和雷打雪型距离冷锋超过100 km以上，强对流型不足100 km。(3) 850 hPa是风场转换的重要层次。强对流型850 hPa露点温度(Td850)、K指数、850 hPa与 500 hPa温差(ΔT85)、850 hPa假相当位温(θse850)、西南急流厚度和强度(I700)、切变线强度(S850)最大，中低层(850~700 hPa)垂直风切变(SL78)最小；雷打雪型对水汽和不稳定能量的要求最低，SL78最大。

Abstract:

Based on conventional observation data, data from intensive automatic ground stations, lightning location data, and NCAR reanalysis data, we analyzed the weather types, spatial-temporal distribution, and environmental conditions of cold season elevated thunderstorms in Hubei from 2011 to 2020. Moreover, we discussed the environmental parameter characteristics of different types of cold season elevated thunderstorms according to the results in boxplots. The main results are as follows: (1) Cold season elevated thunderstorms in Hubei, occurring from November to March the following year, can be categorized into thunderstorm, severe convection, and thundersnow. The spatial distributions of cold season elevated thunderstorms were uneven: there were seasonal and regional differences in the spatial-temporal distribution of different types of cold season elevated thunderstorms. The thunderstorm type occurred mostly in November, January, and February, the strong convective type and thundersnow type usually appeared in early spring (February), and the strong convective type was dominant in March. (2) The low trough cold front, 850 hPa shear line, and low-level southwest jet were favorable circulation backgrounds for the occurrence of overhead thunderstorms in the cold season. The low-level southwest jet was controlled by stable cold air mass near the surface, and the temperature inversion was obvious. The uplift of the low-level southwest jet was triggered along the front inversion layer near 850 hPa, and water vapor, ascending motion, and unstable stratification all appeared above 850 hPa. The distance between thunderstorms and thundersnow was more than 100 km, and the distance between severe convection was less than 100 km. (3) 850 hPa was an important level of wind field transformation. The maximum dew point temperature (Td850), K index, temperature difference between 850 hPa and 500 hPa (ΔT85), false equivalent potential temperature (θse850) of 850 hPa, southwest jet stream thickness and intensity (I700), and shear line intensity (S850) were observed in the severe convection type, while the minimum vertical wind shear (SL78) was observed in the middle and lower layers (850—700 hPa). The thundersnow type had the lowest requirement for water vapor and unstable energy, while the SL78 was the highest.