Atmospheric Responses to Kuroshio SST Front in the East China Sea under Different Prevailing Winds in Winter and Spring

Abstract

tmospheric responses to the Kuroshio SST front in the East China Sea under different prevailing winds are examined using high-resolution observations and numerical modeling. Satellite data reveal a significant in-phase relationship between SST and surface wind speed, indicative of ocean-to-atmosphere influence. The atmospheric response varies according to the relative surface wind direction with respect to the SST front orientation. Under the alongfront condition, low (high) SLP anomalies are found on the warmer (colder) flank of the front, accompanied by surface wind convergence (divergence). Enhanced precipitation and frequent cumulus convection appear over the warm Kuroshio, suggesting an atmospheric response extending into the free troposphere. Under the cross-front condition, when the air blows from cold to warm (warm to cold) SST, divergence (convergence) is located directly over the SST front, and its magnitude is proportional to the downwind SST gradient. Under such prevailing winds, the SST front has little effect on the SLP and precipitation.The Weather Research and Forecasting (WRF) Model is used to investigate the mechanism responsible for the atmospheric adjustment. The results show that under the alongfront condition, large temperature and pressure perturbations in the boundary layer are caused by SST gradients, while stability and turbulent mixing are less affected. By contrast, under the cross-front condition, the perturbations of temperature and pressure are small and shifted downstream, while the SST gradient exerts stronger impact on vertical mixing. The modeling results confirm that the pressure adjustment mechanism contributes more to the atmospheric response under alongfront prevailing winds, while the vertical mixing mechanism dominates the atmospheric adjustment under cross-front winds.