Identification and assessment of the drift velocity of green tides using the maximum cross-correlation method in the Yellow Sea.

The green tides outbreak events seriously threaten the ecological balance of the coastal areas. Quickly and accurately obtaining the spatial distribution and drift state of green tides is key to early warning. Based on Landsat 8 (L8) and Sentinel-2 (S2) image pair, the green tides drift velocity was extracted using the maximum cross-correlation (MCC) method, and windage was calculated by combining ocean current and wind data. The results of the MCC method were validated. Ulva's drift in the Yellow Sea is shaped by both ocean currents and wind, closely aligning with the direction of the currents. Notably, the northward drift velocity of Ulva exhibits a clear boundary around 34°40′N. Windage shows similar characteristics with the Ulva drift velocity, as its values vary with time and space. This study will enhance our comprehension of the dynamic mechanism of green tides drift. • Automated extraction of Ulva drift velocity from medium-resolution imagery pair • The northward drift velocity of Ulva exhibits a distinct boundary around 34°40′N. • Ulva's drift in the Yellow Sea is shaped by both ocean currents and wind. [ABSTRACT FROM AUTHOR]