A Novel Hybrid Framework for Spatio-Temporal Reconstruction of HF Radar Surface Currents along the Western Andaman Sea

Abstract

High Frequency (HF) Radars measure surface currents at higher resolutions (hourly at every ∼6 km), which are essential for understanding the coastal ocean circulation processes at multiple spatio-temporal scales. However, as shore-based remote sensing platforms, these systems are susceptible to data gaps due to environmental noise, unfavourable sea states, or technical interruptions. This study presents a novel hybrid reconstruction framework that couples the Data Interpolating Empirical Orthogonal Function (DINEOF) with the Discrete Cosine Transform-Penalized Least Squares (DCT-PLS) methods to reconstruct HF Radar-derived surface currents along the western Andaman Sea. The reconstruction is validated using leave-one-out cross-validation, independent moored buoy (BD12) observations, satellite-based algorithm-derived currents, and dynamical consistency tests based on mixed-layer depth variability. These complimentary assessments demonstrate strong agreement with observations, yielding correlations exceeding 0.80 and root-mean-square errors below 0.06 m s −1 for both zonal and meridional components. EOF analysis demonstrates that the reconstruction fields preserve the dominant statistical and physical characteristics of the observed circulation, with the first three modes explaining over 70% of the total variance. The reconstructed circulation is consistent with the known large-scale seasonal flow reversals and mesoscale eddy field of the region. Spectral analysis further confirms that the reconstructed fields preserve the dominant seasonal and intraseasonal variability, with a kinetic-energy spectral slope of −1.59 indicative of realistic energy cascade from large to small-scale circulation features. Overall, the proposed hybrid reconstruction framework provides a robust approach for gap-filling HF Radar surface current fields while preserving their dominant statistical and physical characteristics, making it suitable for coastal ocean monitoring, operational oceanography, surveillance, and maritime applications.