Drifter-Observed Reversal of the South China Sea Western Boundary Current From Summer to Autumn

This study analyzes the formation, reversal, and variation of the South China Sea Western Boundary Current (SCSWBC) by nine trajectories of Beidou satellite-tracked drifters, combined with reanalysis current data and satellite remote sensing wind data. It is indicated that: (1) the maximum current speeds of Drifters 1490016, 1490026, 1488526, 862259, and 927745 exceed 1.5 m/s, with the speed of Drifter 862259 even reaching 2.3 m/s in the strong current region of the SCSWBC; ( 2) the SCSWBC in autumn can be sourced from either the northeastward current in the central South China Sea in summer or the westward current in the northeastern South China Sea in September; (3) the monsoon wind transition is attributed for the formation, disappearance, and reversal of the SCSWBC from summer to autumn; and (4) the interannual variation of the SCSWBC mainly depends on the transition time of the monsoon wind.