The role of wind, mesoscale dynamics, and coastal circulation in the interannual variability of the South Vietnam Upwelling, South China Sea – answers from a high-resolution ocean model

Abstract. The South Vietnam Upwelling (SVU) develops in the China Sea (SCS) under influence of southwest monsoon winds. To study role small spatiotemporal scales on SVU functioning and variability, a simulation was performed over 2009–2018 with high-resolution configuration (1 km at coast) SYMPHONIE model implemented western region SCS. Its capability to represent ocean dynamics water masses from daily interannual coastal regional areas is quantitatively demonstrated by comparison available satellite data four situ datasets. variability examined for three development already known: southern (SCU) northern (NCU) upwelling offshore area (OFU). Our model, together observations data, moreover shows first time that Sunda Shelf off Mekong Delta (MKU). results confirm SCU OFU show MKU mean summer intensity wind cyclonic circulation driving intensity. They further reveal other factors contribute variability. First, intraseasonal chronology strengthens (in case regular peaks occurring throughout or stronger winds July–August OFU) weakens intermittent SCU) average Second, mesoscale influences this (multiple dipole eddies associated eastward jets developing along coast enhance intensity). NCU less driven regional-scale (with weaker favoring NCU) more area: prevented (favored) when alongshore (offshore) currents prevail.