融合经验周期模型和ConvLSTM的GNSS水汽时空预报方法

Spatiotemporal Forecasting Method for GNSS Water Vapor Integrating an Empirical Periodic Model and ConvLSTM

  • 摘要: 大气水汽(Precipitable Water Vapor,PWV)在整个自然界中扮演着非常重要的角色,其精准监测与预报对于极端天气预警及卫星对地观测信号延迟改正具有重要作用。为此,本文基于昆明市连续运行参考站(Continuously Operating Reference Station,CORS) 2023至2024年观测数据,构建了融合经验周期模型和卷积长短期记忆神经网络( Convolutional Long Short-Term Memory,ConvLSTM)的区域GNSS水汽递归预报模型。首先,基于多项式函数和44个站点GNSS水汽构建了昆明地区时空连续的水汽分布场,同时引入Lomb-Scargle(LS)方法探测水汽时间序列周期信号,并采用傅里叶级数构建昆明地区水汽变化经验周期模型。其次,将周期性分量从原始数据中分离,得到无明显模式的水汽残差场,并采用ConvLSTM学习水汽残差时空变化特征并构建残差递归预报模型。最后,将经验周期模型与ConvLSTM残差预报模型进行组合,得到昆明区域短临水汽递归预报模型。利用2024年独立观测进行精度验证,结果表明,向后预报水汽1小时的均方根误差(Root Mean Square Error,RMSE)为0.86 mm。此外,当递归预报时长不超过12小时时,模型精度优于1.27 mm。尽管模型预报性能随预报时长的增加有所降低,但仍优于直接预报。该融合预报方法为二维水汽信息预报提供了新的思路,预报产品对于气象灾害预警与高精度定位具有重要价值。

     

    Abstract: Objectives: Atmospheric precipitable water vapor (PWV) plays a crucial role in natural atmospheric processes. Its accurate monitoring and forecasting are of great importance for extreme weather early warning and for correcting signal delays in satellite-based Earth observation. Methods: A regional recursive forecasting model for GNSS-derived PWV is developed by integrating an empirical periodic model with a Convolutional Long ShortTerm Memory (ConvLSTM) neural network, using observations collected from the Kunming Continuously Operating Reference Station (CORS) network during 2023-2024. Meanwhile, the Lomb-Scargle (LS) method is introduced to detect periodic signals in the PWV time series, and a Fourier series is employed to establish an empirical periodic model characterizing PWV variations in the Kunming region. Second, the periodic component is separated from the original PWV observations collected in 2023, and a PWV residual field without evident periodic patterns is obtained. ConvLSTM is then used to learn the spatiotemporal variation characteristics of the PWV residual field and to construct a residual-based recursive forecasting model. Finally, the empirical periodic model iscombined with the ConvLSTM residual forecasting model to obtain a short-term regional recursive PWV forecasting model for Kunming. Compared with purely black-box models, the proposed method achieves satisfactory fitting performance while offering stronger interpretability. Results: The forecasting accuracy is evaluated using independent observations from 2024. The results show that the root mean square error (RMSE) of the one-hourahead PWV forecast is 0.86 mm. It is further demonstrated by the recursive forecasting experiments that the RMSE remains below 1.27 mm for forecast horizons of up to 12 h. Conclusions: Although the forecasting performance gradually decreases with increasing forecast horizon, the proposed model still outperforms the direct forecasting strategy. The integrated method provides a new approach for two-dimensional PWV field forecasting, with forecast products supporting meteorological disaster early warning and high-precision positioning.

     

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