用深度学习修正气候模型海温偏差,提升预测精度。
Global Climate Model Bias Correction Using Deep Learning
- 采用UNet、BiLSTM等深度神经网络,基于历史数据训练修正模型。
- 对孟加拉湾海温预测的均方误差降低15%,优于传统方法。
- 适合关注气候模拟精度提升的研究者与政策制定者。
气候变化影响海洋温度、盐度和海平面,进而影响季风与海洋生产力。基于耦合模型比较计划(CMIP)共享社会经济路径的全球气候模型(GCM)广泛用于气候影响预测,但其在孟加拉湾区域与再分析数据存在显著偏差。例如,CNRM-CM6模型的海表温度(SST)投影与海洋再分析系统(ORAS5)相比,均方根误差(RMSE)达1.5℃。本文开发了一套数据驱动的深度学习模型,用于修正气候模型的投影偏差,并应用于孟加拉湾海温预测。提出三种深度神经网络架构:卷积编码器-解码器UNet、双向LSTM与ConvLSTM;同时使用线性回归与等距累积分布函数(EDCDF)作为对比基准。所有模型以月度CMIP6投影与对应月份的ORAS5为输入输出对进行训练,使用1950–2014年历史数据及2015–2020年未来投影数据进行训练与验证,包含超参数调优。测试集为2021–2024年未来投影数据。详细分析表明,以去气候态的CNRM-CM6投影为输入、去气候态的ORAS5为输出训练的UNet模型表现最优。该新方法使CNRM-CM6数据的均方根误差较EDCDF降低15%。
原文摘要 · Abstract (English)
Climate change affects ocean temperature, salinity and sea level, impacting monsoons and ocean productivity. Future projections by Global Climate Models based on shared socioeconomic pathways from the Coupled Model Intercomparison Project (CMIP) are widely used to understand the effects of climate change. However, CMIP models have significant bias compared to reanalysis in the Bay of Bengal for the time period when both projections and reanalysis are available. For example, there is a 1.5C root mean square error (RMSE) in the sea surface temperature (SST) projections of the climate model CNRM-CM6 compared to the Ocean Reanalysis System (ORAS5). We develop a suite of data-driven deep learning models for bias correction of climate model projections and apply it to correct SST projections of the Bay of Bengal. We propose the use of three different deep neural network architectures: convolutional encoder-decoder UNet, Bidirectional LSTM and ConvLSTM. We also use a baseline linear regression model and the Equi-Distant Cumulative Density Function (EDCDF) bias correction method for comparison and evaluating the impact of the new deep learning models. All bias correction models are trained using pairs of monthly CMIP6 projections and the corresponding month's ORAS5 as input and output. Historical data (1950-2014) and future projection data (2015-2020) of CNRM-CM6 are used for training and validation, including hyperparameter tuning. Testing is performed on future projection data from 2021 to 2024. Detailed analysis of the three deep neural models has been completed. We found that the UNet architecture trained using a climatology-removed CNRM-CM6 projection as input and climatology-removed ORAS5 as output gives the best bias-corrected projections. Our novel deep learning-based method for correcting CNRM-CM6 data has a 15% reduction in RMSE compared EDCDF.
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