基于卫星遥感-卷积神经网络的深远海台风近地水平风场实时反演

REAL-TIME INVERSION OF NEAR-GROUND HORIZONTAL WIND FIELD OF DEEP SEA TYPHOON BASED ON SATELLITE REMOTE SENSING-CONVOLUTIONAL NEURAL NETWORK

  • 摘要: 台风场高精度数值模拟依赖于准确的初始场与约束场作为输入与实时同化条件,相比于台风发展成熟且观测手段相对丰富的近海与陆地区域,台风快速增强的深远海区域往往缺乏有效的常规观测数据,无法为台风数值模拟提供充分的同化数据。卫星红外遥感是当前深远海气象观测的重要技术手段,但其在台风风场方面的应用目前仍局限于人工识别云系特征的方法开展定位与定强,未建立遥感资料与台风风场之间的空间映射关系。该文提出了一种台风风速自适应的新型损失函数,解决了常规卷积神经网络无法考虑台风水平风场中高低风速区域数据分布不平衡的问题,建立了基于卫星九通道红外遥感资料的深远海台风近地水平风场反演模型。研究表明:自适应损失函数准确捕捉了深远海台风近地水平风场中高风速区域的分布特性,该文提出的模型对台风水平风场反演的平均风速误差为2.24 m/s,风向误差为11.5°,其中台风场中强风风速区间反演误差相比于传统卷积神经网络降低了24.16%。同时,该方法具有良好的泛化外推能力,将再分析风场生成的时间分辨率提升至与遥感资料一致的10 min,为深远海台风再分析风场反演提供了新思路。

     

    Abstract: High-precision numerical simulation of typhoon field relies on accurate initial field and constrained field as input and real-time assimilation data. Compared with the inshore and land areas where typhoons are mature and observation methods are relatively abundant, the deep sea areas with rapidly intensification often lack effective conventional observation data, and cannot provide sufficient assimilation data for typhoon numerical simulation. Infrared remote sensing of satellite is an important technical means for deep sea meteorological observation, but its application in typhoon wind field is still limited to the method of artificial identification of cloud system characteristics for positioning and intensity determination, and no spatial mapping relationship between satellite remote sensing data and typhoon wind field has been established. A novel adaptive loss function for typhoon wind speed is proposed to solve the problem that conventional convolutional neural networks cannot consider the unbalanced distribution of high and low wind speed data in the typhoon horizontal wind field, and a deep sea typhoon near-ground horizontal wind field inversion model based on satellite nine-channel infrared remote sensing data is established. The research shows that the adaptive loss function accurately captures the distribution characteristics of high wind speed range in the near-ground horizontal wind field of the deep sea typhoon. The average wind speed error and wind direction error of the model proposed in this paper are 2.24 m/s and 11.5°. The inversion error of strong wind speed interval in typhoon field is reduced by 24.16% compared with the traditional convolutional neural network. At the same time, this method has good generalization and extrapolation ability, and improves the time resolution of reanalysis of wind field generated to 10 minutes, which is consistent with the remote sensing data, and provides a new idea for the wind field inversion of the reanalysis of the deep sea typhoon.

     

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