海南岛一次强飑线系统演变的双偏振特征分析

DUAL-POLARIZATION CHARACTERISTICS OF A STRONG SQUALL LINE EVOLUTION IN HAINAN ISLAND

关键词:  飑线系统  海南岛  上升气流  双偏振雷达

Key words:  squall line  Hainan Island  updraft  dual-polarization radar

摘要:

2020年4月22日发生在海南岛的一次长生命史飑线系统导致海南岛中北部地区遭受大风、强降雨等气象灾害影响。结合常规气象资料及双偏振雷达等探测数据对该次飑线天气系统的演变发展过程进行分析，结果表明：该次飑线天气过程发生在副热带高压带西北边缘地区，地面受准静止锋控制，冷空气强度偏弱，主要受西南暖湿气流影响，配合地面辐合线及合适的热力条件提供较好的环境触发因素。在飑线成形至后续发展演变过程中，雷达反射率因子始终保持较强盛状态（大片云体超过55 dBZ）；在飑线初始阶段（16:20—[16:43]），云系内部的差分反射率因子（ZDR）出现大片区域超过5 dB（垂直方向伸展至8~9 km）；在飑线影响过程中海口站和文昌站上空的ZDR均在降水前期达到最大值，随后伴随降水的逐渐增大而进入减弱阶段，差分传播相移率（KDP）基本与降水强度的变化呈现同升同降趋势。此外，地闪频数在降水前期15~20 min内有明显跃升趋势，并且较ZDR提前6~12 min左右达到最大值，比KDP提前24~48分钟左右达到最大值。

Abstract:

A long-lived squall line system caused strong winds and heavy rainfall in the central and northern parts of Hainan Island on April 22, 2020. The present study analyzed the evolution of the squall line system by comparing conventional meteorological data with dual-polarization radar detection data. The results indicated that the squall line occurred on the northwestern edge of the subtropical high-pressure zone, with a quasi-stationary front controlling the ground. Mainly affected by the warm and humid southwest airflow, the intensity of cold air was generally weak. The ground convergence line and suitable thermal conditions acted as environmental triggers. Throughout the evolution of the squall line, the radar combined reflectivity consistently maintained a strong value with large areas exceeding 55 dBZ. However, the differential reflectance (ZDR) of the cloud system exhibited a large area exceeding 5 dB and extended up to 8-9 km vertically during the initial formation of the squall line (16:20-16:43). During the squall line process, the ZDR over Haikou and Wenchang stations peaked approximately 12 minutes before ground precipitation and decreased as precipitation increased. The KDP was closely correlated with precipitation intensity. Additionally, the frequency of ground lightning increased in the early stage of precipitation, peaking approximately 6 to 12 minutes before ZDR and about 24 to 48 minutes before KDP.