Selective response of the South China Sea circulation to summer monsoon

Abstract

esponse of the South China Sea (SCS) circulation to intraseasonal variability of the summer monsoon is studied with both observations and a 1.5-layer reduced gravity model. Intraseasonal variability of the SCS summer monsoon is characterized by evolution of the wind jet intensity in the middle basin with typical amplitude of 6ms-1 and several peaks on its power spectrum between 10-60 days. However, we find that intraseasonal variability of the Sea Surface Height (SSH) in the SCS presents significant variability to the southeast of Vietnam with amplitude of 6cm and period only between 40-60 days. This implicates the frequency selectivity of oceanic response to wind forcing. Numerical experiments suggest that the intrinsic variability of the SCS circulation accounts for this phenomenon. Based on the Rossby basin mode theory, this is explained by the interaction between the long, westward propagating Rossby waves and the short, eastward propagating Rossby waves.