Study Of The Oceanic Response To The Winter Strong Wind Events In The Yellow And Bohai Sea

During the winter monsoon, the strong wind events often occur over the YellowSea (YS) and the Bohai Sea (BS). This study focuses on the high-frequency oceanicresponse to the winter strong wind events in the Yellow and Bohai Sea, including thedelayed response of the Yellow Sea Warm Current (YSWC), the west-shifted processof the YSWC and the exchange between the YS and the BS. The roles of the shelfwave and the Kelvin wave of the synoptic scale are also investigated in this study.About the delayed response of the YSWC, both the in-site observation and thenumerical simulation results show that the variation of the YSWC corresponds wellwith the wind bursts but has a delay, and the response of the YSWC is accompaniedwith the propagation of the shelf wave. The role of the shelf wave in this responseprocess is explored theoretically. Because the upwind flow is at the geostrophicbalance in the zonal direction, the shelf wave could change the speed of the upwindflow by changing the zonal pressure gradient force. During the wind burst, the zonalpressure gradient force will be formed after the shelf wave starts to propagate, andthen the up wind flow generates, namely the generation of the upwind flow lagsbehind the wind burst. During the wind decay, the zonal pressure gradient force willbe gradually strengthened with the release of the shelf wave, and then the up windflow reaches peak, namely the peak of the upwind flow lags behind the peak of thewind.About the west-shifted process of the YSWC, both the numerical simulation andthe numerical experiment results show that the axis of the YSWC is gradually shiftedwestward to the west-shelf of the YS during the wind burst, and then the YSWCintensifies and decays along the west-shelf of the YS during the wind decay. The roleof the shelf wave in controlling the axis of the upwind flow is studied theoretically.Because the topography at the northern basin has no Potential Vorticity (PV) barrier,the shelf wave of the east-shelf could turn around on the north to propagate southward on the west-shelf of the basin, so that the zonal pressure gradient would be shiftedwestward. Due to the geostrophic balance of the upwind flow, the axis will be alsoshifted westward. Furthermore, the capability and efficiency of the shelf wave incontrolling the axis of the upwind flow are determined by the northern boundary andbottom friction respectively.About the exchange between the YS and the BS, both the in-site observation andthe numerical simulation results show that the discharge process in the BS isassociated with the wind burst stage, whereas the recharge process is linked to thewind decay stage. The role of the Kelvin wave in the exchange between the YS andthe BS is discussed theoretically. During the wind burst, the signal of the Korea-sideKelvin wave propagates into the BS and induces the large fall of the sea level in theBS, and this propagation makes the BS lose water. During the wind burst, the Kelvinwave in the BS is released so that the signal propagates out from the BS, and thispropagation makes the BS gain water.