ADCP Alboran Sea Atlantic Jet Doppler anomaly Gibraltar Gulf of Naples HF radar History of engineering & technology Sentinel-1 Sentinel-2 Sentinel-3 TensorFlow X-band radar artificial neural network augmented observatory circulation cloudiness coastal surface currents current velocity measurement flow reversal frequency band adaptation high frequency radar high-frequency (HF) radar oceanography high-frequency ocean radar hypertrophic ecosystem interference mitigation intertidal foreshore slope inversion marine radar modified temporal waterline method