用统计与机器学习分析泰晤士河溶解氧变化,揭示地理影响和预测关键因素。
Analyzing Spatio-Temporal Dynamics of Dissolved Oxygen for the River Thames using Superstatistical Methods and Machine Learning
- 用q-高斯分布建模溶解氧波动,多乘性经验模态分解法最优。
- 温度、pH和季节是预测溶解氧的关键,长期预测用Informer模型最佳。
- 揭示溶解氧半衰期规律,适合环境政策与生态监测人员参考。
通过超统计方法与机器学习分析泰晤士河水质量指标的时间序列数据,聚焦溶解氧动态。去趋势后,溶解氧波动的概率密度函数呈现重尾特征,可用q-高斯分布有效建模。结果表明,多乘性经验模态分解法在几乎所有拟合中表现最优,对数似然最高。最优q-高斯宽度参数与距海距离呈负相关,凸显地理因素的影响。在同期预测中,结合多种水质指标与时间特征的回归分析显示,轻量梯度提升机(LightGBM)表现最佳;SHAP分析指出温度、pH和季节起关键作用。针对长期预测,使用Transformer模型,Informer在192个历史时间步下持续优于其他模型,实现最低的平均绝对误差(MAE)与对称平均绝对百分比误差(SMAPE)。其性能归因于概率稀疏自注意力机制,更有效捕捉长程依赖,准确识别溶解氧的半衰期周期特征。研究为生态保护评估与水体健康维护提供重要支持。
原文摘要 · Abstract (English)
By employing superstatistical methods and machine learning, we analyze time series data of water quality indicators for the River Thames, with a specific focus on the dynamics of dissolved oxygen. After detrending, the probability density functions of dissolved oxygen fluctuations exhibit heavy tails that are effectively modeled using $q$-Gaussian distributions. Our findings indicate that the multiplicative Empirical Mode Decomposition method stands out as the most effective detrending technique, yielding the highest log-likelihood in nearly all fittings. We also observe that the optimally fitted width parameter of the $q$-Gaussian shows a negative correlation with the distance to the sea, highlighting the influence of geographical factors on water quality dynamics. In the context of same-time prediction of dissolved oxygen, regression analysis incorporating various water quality indicators and temporal features identify the Light Gradient Boosting Machine as the best model. SHapley Additive exPlanations reveal that temperature, pH, and time of year play crucial roles in the predictions. Furthermore, we use the Transformer to forecast dissolved oxygen concentrations. For long-term forecasting, the Informer model consistently delivers superior performance, achieving the lowest MAE and SMAPE with the 192 historical time steps that we used. This performance is attributed to the Informer's ProbSparse self-attention mechanism, which allows it to capture long-range dependencies in time-series data more effectively than other machine learning models. It effectively recognizes the half-life cycle of dissolved oxygen, with particular attention to key intervals. Our findings provide valuable insights for policymakers involved in ecological health assessments, aiding in accurate predictions of river water quality and the maintenance of healthy aquatic ecosystems.
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