The North Atlantic Oscillation(NAO)is a major atmospheric mode in the Northern Hemisphere,characterized by frequent fluctuations in sea level pressure(SLP)across the North Atlantic sector.In the development and evolut...The North Atlantic Oscillation(NAO)is a major atmospheric mode in the Northern Hemisphere,characterized by frequent fluctuations in sea level pressure(SLP)across the North Atlantic sector.In the development and evolution of the NAO,various dynamic physical processes such as the El Niño-Southern Oscillation(ENSO)and Madden-Julian Oscillation(MJO)influence it to different extents.Previous studies using numerical models or deep learning models for daily NAO forecasts have not accounted for the impact of these dynamic physical processes,making accurate and stable NAO forecasting still a challenge.In this study,the Varimax-Rotation Principal Component Analysis(PCA)and data-driven causal inference are used to identify key dynamic physical processes linked to the NAO.Based on these,a deep learning model called the NAO-Causal Weighted Model(NAO-CWM)is developed,which incorporates causal relationships to assign different weights to these processes,providing effective daily forecasts with a lead time of 1-14 days.Evaluation results show that NAO-CWM outperforms the advanced numerical models,offering reliable NAO forecasts and a better capturing of NAO variation trends.展开更多
Numerical models face persistent challenges in subseasonal-to-seasonal(S2S)precipitation forecasting over China due to strong precipitation variability and complex multi-sphere coupling at S2S timescales.In recent yea...Numerical models face persistent challenges in subseasonal-to-seasonal(S2S)precipitation forecasting over China due to strong precipitation variability and complex multi-sphere coupling at S2S timescales.In recent years,artificial intelligence(AI)-based post-processing has emerged as a promising approach,owing to its capacity to learn complex nonlinear relationships and correct systematic model biases from historical data.However,most existing AI-based methods neglect the spatial structure and physical interactions among multi-sphere predictors(e.g.,atmosphere,ocean,and land),limiting their ability to capture the underlying dynamics required for physical consistency.This study develops an S2S precipitation bias-correction network(S2SPre-BCNet)based on a cycle-consistent generative adversarial network(Cycle GAN),which incorporates causality-selected multi-sphere predictors as conditional inputs to improve weekly accumulated precipitation forecasts from the ECMWF S2S system over China at lead times of 1-6 weeks.Compared to the ECMWF S2S,S2SPre-BCNet reduces mean RMSE(root mean square error)by 11.6%(maximum 17.2%),increases mean ACC(anomaly correlation coefficient)by 27.2%(maximum 49.2%),and raises mean HSS(Heidke skill score)by 1.23%(maximum 2.12%).Across the case studies,S2SPre-BCNet lowers the absolute mean precipitation error by 16.4%.Additionally,interpretability analyses reveal that multi-sphere predictors contribute distinctly across lead times,and the model focuses on physically meaningful regions where precipitation dynamics are most complex,highlighting the potential of causality-informed AI for operational S2S bias correction.This study underscores that AI techniques augmented by causality-based predictor selection can effectively correct biases in forecasts produced by numerical models,enabling their use in operational forecasting.展开更多
基金Supported by the National Key Research and Development Program of China(2020YFA0608000)Meteorological Joint Funds of the National Natural Science Foundation of China(U2142211)+1 种基金National Natural Science Foundation of China(42075141,42341202,and 62088101)Shanghai Municipal Science and Technology Major Project(2021SHZDZX0100)。
文摘The North Atlantic Oscillation(NAO)is a major atmospheric mode in the Northern Hemisphere,characterized by frequent fluctuations in sea level pressure(SLP)across the North Atlantic sector.In the development and evolution of the NAO,various dynamic physical processes such as the El Niño-Southern Oscillation(ENSO)and Madden-Julian Oscillation(MJO)influence it to different extents.Previous studies using numerical models or deep learning models for daily NAO forecasts have not accounted for the impact of these dynamic physical processes,making accurate and stable NAO forecasting still a challenge.In this study,the Varimax-Rotation Principal Component Analysis(PCA)and data-driven causal inference are used to identify key dynamic physical processes linked to the NAO.Based on these,a deep learning model called the NAO-Causal Weighted Model(NAO-CWM)is developed,which incorporates causal relationships to assign different weights to these processes,providing effective daily forecasts with a lead time of 1-14 days.Evaluation results show that NAO-CWM outperforms the advanced numerical models,offering reliable NAO forecasts and a better capturing of NAO variation trends.
基金Supported by the Meteorological Joint Funds of National Natural Science Foundation of China(U2542211 and U2542212)Original Exploration Project of National Natural Science Foundation of China(42450163)National Natural Science Foundation of China(42405147)。
文摘Numerical models face persistent challenges in subseasonal-to-seasonal(S2S)precipitation forecasting over China due to strong precipitation variability and complex multi-sphere coupling at S2S timescales.In recent years,artificial intelligence(AI)-based post-processing has emerged as a promising approach,owing to its capacity to learn complex nonlinear relationships and correct systematic model biases from historical data.However,most existing AI-based methods neglect the spatial structure and physical interactions among multi-sphere predictors(e.g.,atmosphere,ocean,and land),limiting their ability to capture the underlying dynamics required for physical consistency.This study develops an S2S precipitation bias-correction network(S2SPre-BCNet)based on a cycle-consistent generative adversarial network(Cycle GAN),which incorporates causality-selected multi-sphere predictors as conditional inputs to improve weekly accumulated precipitation forecasts from the ECMWF S2S system over China at lead times of 1-6 weeks.Compared to the ECMWF S2S,S2SPre-BCNet reduces mean RMSE(root mean square error)by 11.6%(maximum 17.2%),increases mean ACC(anomaly correlation coefficient)by 27.2%(maximum 49.2%),and raises mean HSS(Heidke skill score)by 1.23%(maximum 2.12%).Across the case studies,S2SPre-BCNet lowers the absolute mean precipitation error by 16.4%.Additionally,interpretability analyses reveal that multi-sphere predictors contribute distinctly across lead times,and the model focuses on physically meaningful regions where precipitation dynamics are most complex,highlighting the potential of causality-informed AI for operational S2S bias correction.This study underscores that AI techniques augmented by causality-based predictor selection can effectively correct biases in forecasts produced by numerical models,enabling their use in operational forecasting.
