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基于物理引导与加权策略的高原阵风预报及可解释性分析

Physically Guided and Weighted Strategy for Gust Forecasting over the Tibetan Plateau with Interpretability Analysis

  • 摘要: 青藏高原复杂地形区的阵风预报是业务难点,冬春干季大风频发使这一问题尤为突出。为提升高原干季阵风预报能力并解析其多尺度物理机制,本研究针对青藏高原复杂地形特点,构建了欧洲中期天气预报中心(ECMWF)预报变量、历史持续性信息、时空属性及地形动力因子的四类物理引导特征体系。基于轻量梯度提升机(LightGBM)算法,设计了由简至繁的递进式特征融合试验(Exp1—Exp4),系统量化了各类特征对预报性能的边际贡献。结果表明,融合全特征的Exp4模型效果最优,平均绝对误差较数值模式预报降低52.5%。特征重要性分析揭示,经度、海拔、纬度为核心影响因子,地形动力因子(海拔、坡度、坡向变率等)的累计贡献率达13.42%,SHAP(SHapley Additive exPlanations)分析进一步揭示了海拔3000?m的阈值效应。针对训练样本中强阵风(≥10.8?m·s?1)占比约10%的稀缺问题,引入分级加权策略。加权Exp4模型在8级(17.2–20.7?m·s?1)和9级(≥20.8??m·s?1)阵风预报中,TS评分较未加权模型分别提升79.4%和148.2%,漏报率降低23.1%和10.5%;与ECMWF相比,TS评分分别提升96%和60%。误差分析表明,该模型有效订正了ECMWF在高海拔复杂地形区的系统性高估偏差,并显著提升了午后强阵风的捕捉能力。本研究为高原灾害性阵风预警提供了兼具精度与可解释性的技术方案。

     

    Abstract: Gust forecasting over the complex terrain of the Qinghai–Tibet Plateau remains a major operational challenge, particularly during the frequent gales of the winter–spring dry season. To improve dryseason gust forecasts and reveal the underlying multiscale physical mechanisms, this study constructs four physically guided feature sets: European Centre for Medium-Range Weather Forecasts (ECMWF) forecast variables, historical persistence information, spatiotemporal attributes, and topographic dynamic factors. Using the Light Gradient Boosting Machine (LightGBM) algorithm, a set of progressive feature fusion?experiments (Exp1–Exp4) is designed to systematically quantify the marginal contribution of each feature category to forecast performance. Results show that the fullfeature Exp4 model achieves the best performance, with a mean absolute error (MAE) that is 52.5% lower than that of the raw ECMWF forecast. Feature importance analysis identifies longitude, altitude, and latitude as the most influential factors, with topographic dynamic factors (altitude, slope, aspect variability, etc.) contributing a cumulative 13.42%. SHapley Additive exPlanations (SHAP) is used to interpret the model. The SHAP-based analysis further reveals a threshold effect at 3000 m altitude. To address the systematic underestimation caused by the scarcity of stronggust samples (≈10% of the training set), a graded weighting strategy is introduced. For gust events of level?8 (17.2–20.7?m·s?1) and level?9 (≥20.8?m·s?1), the weighted Exp4 model increases the Threat score (TS) by 79.4% and 148.2%, and reduces the Miss rate by 23.1% and 10.5%, respectively, compared with the unweighted model. Relative to the raw ECMWF forecast, the TS improvements are 96% and 60%, respectively. Error analysis demonstrates that the proposed model effectively corrects the systematic overestimation bias of ECMWF over the highaltitude complex terrain and significantly enhances the capture of strong gusts in the afternoon. This study provides an accurate and interpretable technical solution for operational hazardous gust warning over the Tibetan Plateau.

     

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