Dynamics of Yellow Sea Warm Current under Intermittent Winter Monsoon

The dynamics of the Yellow Sea Warm Current (YSWC) under intermittent winter monsoon is studied by numerical modeling with ROMS. Consistent with previous results, the winter mean YSWC is almost located on the western flank of the Yellow Sea Trough (YST), while on synoptic scale the flow pattern is always undergoing intense variation. That is because the winter monsoon, which is an important driving force of YSWC, is not constant but with several strong wind events and breezeless intermittences during the season. The flow pattern and dynamics of YSWC features significant dimorphic corresponding to the variation of wind forcing. The winter mean flow pattern is just a synthetic image of them.

During a strong wind event, a ridge-trough system of sea level parallel to YST is generated after 1~2 days setup, and a bi-loop barotropic current system composed by a strong and wide upwind flow centered in YST and downwind coastal flows on both sides is formed. The flow pattern is comparable to the wind driven current system in elongated, rotating basin described by Winant (2004). After wind event the sea level ridge-trough system falls into oscillation and collapse because of the vanishment of surface forcing, while the barotropic current system becomes much weaker and shifts westward following PV conservation. In contrast to the dramatic variation of barotropic flow pattern, the structure of baroclinic flow pattern doesn’t vary much: a northward flow which is as weak as that after-wind-event barotropic component exists all over the region with an also weak deep counterflow in YST.