Application of Deep Learning Model TAGAN in Nowcasting of Strong Convective Echo
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摘要: 近年来深度学习模型在解决对防灾减灾影响巨大且极具挑战性的临近预报问题的应用中日益增多。本文中,我们把临近预报作为一个时空序列预测的任务,将雷达反射率因子作为试验对象,使用基于对抗神经网络(GAN)优化构建的TAGAN深度学习模型预测未来1小时的雷达回波图像,并且与Rover光流法、基于卷积神经网络的3D U-Net模型进行对比试验。选取2018年全球气象AI挑战赛雷达回波数据集进行训练与测试,检验结果表明TAGAN模型在命中率(POD),虚警率(FAR),临界成功指数(CSI)以及相关系数等多种评分上要优于传统的光流法和对比的3D U-Net深度学习模型,TAGAN模型在以上的检验评分表现出色,并且随预测时间的增加较之传统光流模型效果更优,这为拓展和提升深度学习模型在临近天气预报中的应用提供了参考依据。Abstract: In recent years, deep learning models have been increasingly used in solving nowcasting problems that largely affect disaster prevention and mitigation. In this study, we take nowcasting as a spatio-temporal sequence prediction task and use the radar reflectivity factor as the test object. We use the two-stream attention generative adversarial network (TAGAN) deep learning model based on the Generative Adversarial Network frame to predict the radar echo image of the future 1 h and compare it with the Rover optical flow method and the 3D U-Net model based on the convolutional neural network. The radar echo data set of the 2018 Global Weather AI Challenge is selected for training and testing. The test results show that the TAGAN model has advances by multiple scores, including hit rate, false alarm rate, critical success index, and correlation coefficient. The TAGAN model performs well in these test scores and increases with the prediction time compared to the traditional optical flow method and the comparative deep learning model. Moreover, compared with that of the traditional optical flow model, the improvement effect of the TAGAN model is more significant. The results may shed some light on the expansion and improvement of the application of deep learning models in near-weather forecasting.
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Key words:
- Nowcasting /
- Spatiotemporal prediction /
- Deep learning /
- Radar echo
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图 6 30 dBZ阈值下三种模型FAR和HSS测试集平均得分随时间变化(折线),阴影上下界代表测试集所有样本得分的上下四分位数
Figure 6. Average scores of the False Alarm Rate and Heidke Skill Score test sets of the three models under 30 dBZ threshold change over time (broken line): the upper and lower bounds of the shade represent the upper and lower quartiles, respectively, of the scores of all samples in the test set
图 7 四组预测个例最后一帧对比。(a–d)分别为四组回波过程,每一列分别为真实过程、Rover、TAGAN、3DUnet在四组预测个例中的最后一帧
Figure 7. Comparison of the last frame of the four sets of prediction cases, where (a–d) are the four sets of echo processes, and each column is the last frame of the real process, Rover, TAGAN, and 3DUnet in the four sets of process predictions
图 9 四组预测个例第一帧回波图真实值,其中红框为计算质心的范围(覆盖未来9帧回波主体范围),蓝线轮廓为回波值大于30 dBZ的回波主体
Figure 9. True value of the first frame of the four groups of prediction cases: the red box represents the range of the calculated centroid covering the range of the echo subject of the next nine frames), while the blue line outline is the echo subject with an echo value greater than 30 dBZ
表 1 混淆矩阵
Table 1. Confusion matrix
预测正类 预测负类 观测正类 TP FN 观测负类 FP TN 表 2 测试集检验对比
Table 2. Test set comparison
阈值30 min预测 阈值60 min预测 模型 10 dBZ 20 dBZ 30 dBZ 40 dBZ 10 dBZ 20 dBZ 30 dBZ 40 dBZ CSI TAGAN 0.71 0.66 0.48 0.16 0.61 0.55 0.34 0.08 3DUnet 0.66 0.60 0.42 0.11 0.54 0.47 0.24 0.04 Rover 0.63 0.57 0.40 0.15 0.52 0.44 0.27 0.06 FAR TAGAN 0.20 0.23 0.30 0.39 0.27 0.31 0.40 0.51 3DUnet 0.27 0.29 0.38 0.56 0.38 0.40 0.53 0.75 Rover 0.23 0.29 0.43 0.66 0.33 0.41 0.60 0.82 POD TAGAN 0.86 0.81 0.60 0.19 0.80 0.71 0.44 0.10 3DUnet 0.87 0.79 0.54 0.13 0.81 0.66 0.31 0.05 Rover 0.78 0.73 0.57 0.19 0.70 0.63 0.43 0.09 HSS TAGAN 0.78 0.75 0.61 0.25 0.69 0.65 0.46 0.12 3DUnet 0.71 0.67 0.53 0.18 0.61 0.56 0.33 0.06 Rover 0.72 0.70 0.54 0.24 0.60 0.54 0.38 0.11 注:加粗的数字表示对比模型中检验评分最优 表 3 测试集检验对比
Table 3. Test set comparison
模型 均方误差(MSE) 平均绝对误差(MAE) 相关系数
(COR)TAGAN 2046.30 8513.19 0.853 3DUnet 2610.69 10372.13 0.812 Rover 2922.36 10427.86 0.793 注:加粗的数字表示对比模型中检验评分最优 -
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