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基于雷达客观识别的湖北省对流初生时空分布特征

Spatiotemporal distribution characteristics of Convection Initiation based on objective radar identification in Hubei Province

  • 摘要: 对流初生(Convection Initiation,CI)是强对流天气开始活动的标志,其识别与预警对于气象防灾减灾具有重要意义。基于2020—2024年湖北省高时空分辨率雷达组合反射率拼图数据和地面自动气象站降水资料,采用改进的CI客观识别算法,构建湖北省CI数据集,并分析了时空分布特征及其与地形的关系。结果表明:(1) 2020—2024年湖北省识别CI共107 322次,日平均CI次数59次,日数占比73%,其中2020年日平均CI次数和日数占比最多,2022年最少;季节分布上,夏季最活跃,春、秋季次之,冬季最少。(2) 湖北省CI活动月变化呈双峰型,主峰位于6—7月,对应梅雨季,次峰位于10—11月,与季节转换冷暖气团交汇以及台风等热带系统影响相对应。(3) CI日变化特征呈午后至傍晚的单峰或主峰结构,夏季后半夜存在次峰;除秋季外,白天CI次数普遍高于夜间。(4) CI分布受下垫面影响显著,湖北省高频区主要集中在鄂西南山地的恩施与宜昌交界处,鄂东南幕阜山、鄂东北大别山、鄂西北山地及大型湖泊水库周边为CI较高频区,而中部平原盆地相对低发。上述结果初步揭示了湖北省CI活动的发生发展规律,有助于本地化CI预报模型的构建,以实现对强对流天气的早发现、早预警。

     

    Abstract: Convection Initiation (CI) is an important precursor to the occurrence of severe convective weather, and its identification and early warning are of great significance for meteorological disaster prevention and mitigation. Using high spatiotemporal resolution radar composite reflectivity mosaic data and surface automatic weather station precipitation data from Hubei Province for the period 2020–2024, this study employed an improved high-resolution grid-based objective CI identification algorithm to construct a CI dataset for Hubei Province. The spatiotemporal distribution characteristics of CI and their relationship with topography were subsequently analyzed. The results are as follows. (1) A total of 107,322 CI number were identified in Hubei Province from 2020 to 2024, with a daily mean CI number of 59 times and a percentage of CI days of 73%. Both the daily mean CI number and the percentage of CI days were highest in 2020 and lowest in 2022. Seasonally, CI activity was most active in summer, followed by autumn and spring, and least active in winter. (2) The monthly variation of CI activity during this period was characterized by a bimodal pattern, with the primary peak observed in June–July, corresponding to the Meiyu season, and a secondary peak noted in October–November, associated with seasonal transition, cold-warm air convergence, and the influence of tropical systems such as typhoons. (3) The diurnal variation of CI was characterized by a single or dominant peak from afternoon to evening, with a secondary peak identified in the late night during summer. Except in autumn, daytime CI occurrences were generally higher than those at night. (4) The distribution of CI was found to be uneven and significantly influenced by underlying surfaces. High-frequency areas were concentrated mainly in the mountainous regions of southwestern Hubei, particularly at the border of Enshi and Yichang. Relatively high-frequency areas included the Mufu Mountains in southeastern Hubei, the Dabie Mountains in northeastern Hubei, mountainous regions in northwestern Hubei, and areas surrounding large lakes and reservoirs, while the central plains and basins were associated with a relatively lower CI number. These findings preliminarily reveal the occurrence and development patterns of CI activity in Hubei Province, contributing to the construction of a localized CI forecasting model, which facilitates the early detection and warning of severe convective weather.

     

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