1. A Structured Graph Neural Network for Improving the Numerical Weather Prediction of Rainfall.
- Author
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Peng, Xuan, Li, Qian, Chen, Lei, Ning, Xiangyu, Chu, Hai, and Liu, Jinqing
- Subjects
NUMERICAL weather forecasting ,MACHINE learning ,RAINFALL frequencies ,RAINFALL ,LONG-range weather forecasting ,RAINFALL probabilities - Abstract
The current challenges of numerical weather prediction (NWP) of rainfall mainly stem from the complex and multiscale nature of rainfall. In recent years, as observation capability improved worldwide, there has been an increased feasibility to use data‐driven models to enhance forecasting performance with rainfall observation. Compared to traditional statistical and machine learning models, deep‐learning models show considerable promise in capturing the spatial‐temporal features of weather processes from multiple predictors, but the convolution‐based feature extractor is suboptimal due to the linear nature of convolution kernels. In this study, a multilevel forecasting model is proposed to forecast each rainfall level, in which each submodel adopts a graph neural network for feature extraction. Spatial and temporal propagation functions based on grid structure are designed to explicitly represent feature fusion and propagation of multiple predictors across multiple scales. On model training, a weight setting strategy that balances the impact of samples with different rainfall values on the total training loss is proposed, and a soft classification label is designed to convert observed rainfall into the probability of rainfall above each threshold. The proposed model was trained and validated on NWP data provided by European Center for Medium‐Range Weather Forecast, and results show significant improvement over the NWP in terms of threat score (TS) and Heidke Skill Score (HSS) scores. Analysis of the forecast results for two typical rainfall processes also illustrates that the proposed method can predict rainfall with more reasonable location and intensity. Plain Language Summary: Rainfall forecast plays an important role in human's daily life, and numerical weather prediction (NWP) has helped to greatly improve the performance of rainfall forecast. However, accurate forecasting is still challenging due to the complex characteristics of rainfall and uncertainty of NWP models. In recent years, there has been accumulated large amount of high‐precision rainfall observation data around the world. It becomes possible to enhance the forecasting performance with these data. However, the traditional statistical models either ignore the weather background information or struggle to capture the complex interactions between different variables produced by the NWP model. To handle these shortages, a neural network model based on grid structure is proposed, which can extract multiscale features from the output variables of the NWP model trough an information propagation mechanism. Meanwhile, a multilevel forecasting strategy is proposed for better handling different rainfall levels along with different uncertainties, from light rain to heavy downpours. The proposed model was applied to a real NWP data for the central part of East China, and the results illustrate significant improvement in terms of common forecast skills and intuitive feeling. Key Points: A graph neural network for extracting features from the output variables of the numerical weather prediction (NWP) model for rainfall forecastingA level‐specific training label and a weighted loss function based on the relative frequency of rainfall amount to better training the modelThe proposed method improves the forecast skill at all rainfall intensity levels and can yields more reasonable location and intensity of rainfall [ABSTRACT FROM AUTHOR]
- Published
- 2023
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