Intraseasonal variability of the South Vietnam upwelling, South China Sea: influence of atmospheric forcing and ocean intrinsic variability

Abstract. The South Vietnam upwelling (SVU) develops off the Vietnamese coast (South China Sea, SCS) during southwest summer monsoon over four main areas: northern coastal (NCU), southern (SCU), offshore (OFU) and shelf Mekong River mouth (MKU). An ensemble of 10 simulations with perturbed initial conditions were run fine-resolution SYMPHONIE model (1 km inshore) to investigate daily intraseasonal variability SVU influence ocean intrinsic (OIV) strong 2018. is similar for SCU, MKU OFU, driven first order by wind variability. SCU are induced stable dynamics (the northeastward then eastward boundary current) have very little chaotic OIV has a stronger on OFU. In July, OFU mainly along flank jet. strongest related meridional position August, this in area positive curl cyclonic eddies north OIV, weaker than organization mesoscale circulation. NCU shows behavior different from that observed other areas. heart summer, large-scale circulation formed jet eddy dipole well established an alongshore current preventing development. early late weaker, allowing strongly nature develop area. During those periods, circulation: favored (annihilated) offshore-oriented (alongshore) structures.