THE ASSESSMENT OF APPLICATION EFFECTIVENESS OF THREE MACHINE LEARNING METHODS IN AUTOMATIC IDENTIFICATION OF THUNDERSTORM GALE IN GUANGDONG
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摘要: 基于2012—2019年自动站雷暴大风观测实况和对应雷达回波,利用传统机器学习方法(决策树)和深度学习方法(CNN、YOLO)等三种机器学习方法分别建立雷暴大风自动识别模型。根据广东雷暴大风回波特征,选取50 dBZ高度、反射率因子强度梯度等5个回波参量作为决策树的特征因子;将1~9 km高度的雷达回波分为11层,作为YOLOv3的输入层,使其由原3个特征层扩展到11层,训练优化后的YOLOv3可更合理刻画雷暴大风的空间结构特征。经批量测试和业务试运行试验,检验结果表明:三种模型中基于决策树的模型虚警最高,基于CNN的模型漏报最多,基于YOLO的模型识别效果最好,其POD和CSI均最高。通过对广东2020年汛期5次系统性和5次局地性雷暴大风过程进行分类型自动识别效果评估,并选取任意天气下长达30天连续时段进行不间断识别检验,结果表明该算法对于不同类型的雷暴大风均有较好的识别能力,具备业务化应用前景。Abstract: On the basis of radar data and thunderstorm gale observation in Guangdong from 2012 to 2019, three machine learning algorithms, including a traditional machine learning algorithm (Decision Tree) and two deep learning algorithms (CNN and YOLO), were applied to establish automatic identification models for thunderstorm gale respectively. In line with the radar echo characteristics of thunderstorm gale in Guangdong, six echo parameters, such as 50 dBZ height and reflectivity factor gradient, were selected as the characteristic factors of the decision tree. In addition, the heights of 1 to 9 km were divided into 11 radar echo input layers of YOLOv3, expanding from the original three characteristic layers, which described the spatial structure characteristics of thunderstorm gale more reasonably after optimization. A series of business run-in tests indicated that among the three identification models, the model using the decision tree presents the highest FAR and the one based on CNN misses the most identifications, while the identification model based on YOLO behaves the best, with the highest POD and CSI. By evaluating the automatic identification effects of five systematic and five local thunderstorm gale processes during the rainy season of 2020 in Guangdong, and selecting continuous periods of up to 30 days under any weather condition for ongoing identification tests, the results reveal that the YOLO algorithm possesses good recognition ability for different types of thunderstorm gale with considerable business application prospect.
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Key words:
- thunderstorm gale /
- automatic identification /
- machine learning /
- radar echo /
- deep learning
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表 1 三种模型识别效果批量测试对比
模型 POD FAR CSI 决策树 0.934 0.57 0.363 CNN 0.865 0.489 0.421 YOLO 0.994 0.308 0.685 说明:表中YOLO识别结果的置信度=0.7,后文中YOLO识别结果均采用该置信度。 表 2 2016年4月13日飑线型雷暴大风天气过程识别评估结果
模型 实况记录 命中数 空报数 漏报数 POD FAR CSI 决策树 200 214 14 0.935 0.517 0.467 CNN 214 189 135 25 0.883 0.417 0.542 YOLO 210 101 4 0.981 0.325 0.667 表 3 2019年3月2日雷暴大风、强降水混合天气过程识别评估结果
模型 实况记录 命中数 空报数 漏报数 POD FAR CSI 决策树 26 39 2 0.929 0.600 0.388 CNN 28 25 30 3 0.893 0.545 0.431 YOLO 28 28 0 1.000 0.500 0.500 表 4 基于YOLO的识别模型对于局地性天气过程识别能力的评估
类型 实况记录 POD FAR CSI 局地性过程 71 0.958 0.364 0.618 系统性过程 148 0.986 0.321 0.673 表 5 基于YOLO的识别模型在连续时段内识别能力的评估
模型 实况记录 POD FAR CSI YOLO 1 520 0.939 0.374 0.601 表 6 2021年全年雷暴大风过程识别效果评估结果
模型 实况记录 POD FAR CSI YOLO 1 603 0.927 0.338 0.629 -
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