Correction: Warming of the lower ocean layer modulated by vertical advection prior to typhoon arrival

During the period from 25 August 2012 to 11 December 2013, five typhoons were tracked passing by an observation station near the Xisha Islands in the northern South China Sea (NSCS). An analysis of the temperature observations revealed that the lower ocean layer (below the thermocline) experiences warming prior to the typhoon’s arrival. A three-dimensional model was used to analyze the dynamic processes of lower layer ocean warming. The simulations indicate that the upper layer (above the thermocline) is controlled by Ekman dynamics, with intense vertical mixing leading to upper-ocean cooling, consistent with previous understanding. Below the thermocline, the barotropic quasigeostrophic constraint emerges as the pivotal dynamic control of the waters preceding the typhoon, where the vertical velocity induced by Ekman suction drives the circulation in the lower layer. The geostrophic imbalance contributed by the pressure gradient force supplies anticlockwise acceleration and enhances divergence. Due to the negative Ekman suction and the lower layer ocean divergence, there is strong downwelling prior to the typhoon, which induces vertical warm advection leading to the warming of the intermediate ocean. Finally, a simplified estimate is formulated for the lower layer ocean warming preceding the typhoon's arrival.