不同环流背景下甘肃陇东地区区域性暴雨的环境特征分析

Environmental Characteristics of Regional Rainstorms under Different Circulation Backgrounds in Longdong, Gansu Province

  • 摘要: 为了提高甘肃陇东地区区域性暴雨的预报服务水平,基于常规气象观测资料、NCEP/NCAR再分析资料、风云二号(FY-2)卫星观测资料等,分析了2010—2020年陇东地区区域性暴雨的环流特征,并进行了天气学分型和差异研究。结果表明:陇东地区区域性暴雨可分为副热带高压(简称副高)型(Ⅰ型和Ⅱ型)、东高西低型、低槽东移型、低涡型和西北气流型,其中副高型出现次数最多,西北气流型最少。各型暴雨的环流形势均表现为中低层存在切变线、低空急流或显著偏南风、地面辐合线或冷锋等抬升触发系统。副高型和东高西低型水汽条件最好,而低涡型和西北气流型较差。低涡型动力条件最强,而副高型最差。副高型的对流不稳定最强,而低槽东移型和东高西低型较差,西北气流型的垂直温差平流最强。副高型云团一般发展比较旺盛,云顶温度较低,降水对流系统较强,而东高西低型云系差别较大,盛夏对流系统较强。低槽东移型云顶黑体亮度温度(TBB)较高,对流系统相对较弱,低涡型云系多为涡旋云系或逗点云系,对流系统差异较大。西北气流型多发生在少云区或层云区,时有分散的对流云团,平均最低TBB是所有类型中最高的。

     

    Abstract: To improve the forecast service of regional rainstorms in Longdong, the circulation characteristics of regional rainstorms in the region from 2010 to 2020 are analyzed by using conventional meteorological observation data, NCEP/NCAR reanalysis data, and Fengyun-2 (FY-2) satellite data. In addition, synoptic types and their differences are also studied. The results show that the regional rainstorms in Longdong can be divided into five types: Subtropical high type (which can be further divided into subtropical high type Ⅰ and subtropical high type Ⅱ), east-high west-low type, eastward-moving low trough type, low vortex type and northwest airflow type. Among them, the subtropical high type occurs most frequently, while the northwest airflow type occurs least frequently. The circulation patterns of all types show the presence of lifting triggering systems such as shear lines in the middle and lower levels, low-level jet streams or significant southerly winds, and surface convergence lines or cold fronts. The water vapor conditions are the most favorable for the subtropical high type and the east-high west-low type, whereas they are relatively poor under the low vortex type and the northwest airflow type. The dynamic conditions are the strongest for the low vortex type, while the weakest for the subtropical high type. The subtropical high type exhibits the strongest convective instability, while the eastward-moving low trough type and the east-high west-low type show relatively weaker convective instability. The northwest airflow type features the strongest vertical temperature differential advection. Cloud clusters associated with the subtropical high type are generally well-developed, with low cloud-top temperatures and strong convective precipitation. In contrast, cloud systems under the east-high west-low type show large variations, with strong convective activity in midsummer. For the eastward-moving low trough type, the cloud-top black body temperature (TBB) is relatively high, and convection is comparatively weak. Cloud systems under the low vortex type are mostly vortex- or comma-shaped, with large variations in convective intensity. The northwest airflow type mostly occurs in cloud-sparse regions or stratiform cloud regions, occasionally accompanied by scattered convective cloud clusters, and its average minimum TBB is the highest among all types.

     

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