用经验正交函数降维,结合神经网络预测智利气候时空变化。
Spatiotemporal Forecasting in Climate Data Using EOFs and Machine Learning Models: A Case Study in Chile
- 先用时变经验正交函数分解气候数据,降维为单变量时间序列。
- 通过小波-神经网络模型预测未来中短期气候模式,准确率较高。
- 识别出空间一致性高的区域,提升预测效果,适合气象资源规划者。
在气候变异性强的地区如智利,高效资源配置与环境规划需要先进的预测工具。本研究提出一种创新且计算高效的混合方法,将机器学习(ML)时间序列预测与成熟统计技术结合。对时空数据进行时变经验正交函数(EOFs)分解,得到时间函数ϕ_k(t)与空间系数α_k(s),实现降维。利用小波分析提取ϕ_k(t)的高分辨率时频信息,再通过神经网络对未来时间步h内ϕ_k(t+h)进行预测,并重构原始时空数据。该方法应用于覆盖智利全境的网格化气候数据集,将高维多变量时空预测问题转化为低维单变量预测。结合动态时间规整聚类分析,识别降雨序列相似性,评估空间一致性和可预测性,定位性能更优区域。同时揭示了空间一致性差、可预测性低区域预测不佳的原因。通过聚类中心(medoids)优化预测流程,显著降低计算复杂度,获得具实用价值的中短期预测结果。
原文摘要 · Abstract (English)
Effective resource management and environmental planning in regions with high climatic variability, such as Chile, demand advanced predictive tools. This study addresses this challenge by employing an innovative and computationally efficient hybrid methodology that integrates machine learning (ML) methods for time series forecasting with established statistical techniques. The spatiotemporal data undergo decomposition using time-dependent Empirical Orthogonal Functions (EOFs), denoted as \(ϕ_{k}(t)\), and their corresponding spatial coefficients, \(α_{k}(s)\), to reduce dimensionality. Wavelet analysis provides high-resolution time and frequency information from the \(ϕ_{k}(t)\) functions, while neural networks forecast these functions within a medium-range horizon \(h\). By utilizing various ML models, particularly a Wavelet - ANN hybrid model, we forecast \(ϕ_{k}(t+h)\) up to a time horizon \(h\), and subsequently reconstruct the spatiotemporal data using these extended EOFs. This methodology is applied to a grid of climate data covering the territory of Chile. It transitions from a high-dimensional multivariate spatiotemporal data forecasting problem to a low-dimensional univariate forecasting problem. Additionally, cluster analysis with Dynamic Time Warping for defining similarities between rainfall time series, along with spatial coherence and predictability assessments, has been instrumental in identifying geographic areas where model performance is enhanced. This approach also elucidates the reasons behind poor forecast performance in regions or clusters with low spatial coherence and predictability. By utilizing cluster medoids, the forecasting process becomes more practical and efficient. This compound approach significantly reduces computational complexity while generating forecasts of reasonable accuracy and utility.
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