Climate-aware hybrid Kolmogorov-Arnold networks for interpretable solar radiation forecasting

Accurate short-term solar radiation forecasting is essential for the reliable integration of photovoltaic systems into modern power grids, particularly in regions characterized by strong climatic heterogeneity. This study proposes a Climate-Aware Hybrid Kolmogorov-Arnold Network (CA-HKAN) framework for forecasting hourly Global Horizontal Irradiance (GHI) under diverse atmospheric regimes. The framework integrates an intrinsically interpretable spline-based Kolmogorov-Arnold Network with a feed-forward neural network through a deterministic switching mechanism governed by Extreme Value Theory (EVT). EVT is employed to derive climate-specific clearness-index thresholds, which are scaled to delineate stable and volatile irradiance regimes. These thresholds deterministically activate the interpretable spline-based component under physically stable conditions, while a neural network fallback is engaged during volatile or extreme atmospheric states. The proposed approach is evaluated using hourly meteorological and irradiance data from five climatically distinct regions in Saudi Arabia, representing desert, coastal, mountainous, and transitional environments. Experimental results demonstrate that the proposed CA-HKAN framework achieves predictive accuracy competitive with modern deep learning baselines, such as CNN-BiLSTM models, across all regions while maintaining physical consistency, including non-negativity and realistic irradiance bounds. Compared with standalone models, the hybrid approach offers a favorable balance between accuracy, robustness, and transparency. Ablation analyses further confirm the complementary roles of the hybrid components and the effectiveness of EVT-based regime control. Overall, the CA-HKAN framework provides a practical and interpretable solution for climate-aware solar radiation forecasting, supporting trustworthy deployment in sustainable energy systems operating under heterogeneous and non-stationary atmospheric conditions.