Geographical and monthly variability of the first baroclinic Rossby radius of deformation in the South China Sea

Abstract

In this paper, based on the 1-degree grided data of the monthly mean temperature and salinity data at standard levels in the South China Sea(SCS), we solve the linearized vertical eigenvalue problem for horizontal large-scale waves, the first baroclinic phase speed c 1 and the first baroclinic Rossby radius of deformation R 1 are obtained. Due to the regional variations of the water depth, stratification and latitude, R 1 varies largely. In most months of a year, in the deep sea area, the effect of temporal variation of the stratification on R 1 can be neglected, however, in November and December, R 1 in the central SCS changes largely due to a large stratification variation of the local water mass; in the wide continental shelf, the effect of temporal variation of the stratification on R 1 is very important. The westward phase speed of the first baroclinic Rossby wave C R 1 derived from observations and numerical models give an independent estimation which is consistent with solving the vertical eigenvalue problem, which shows that the estimated C R 1 could be used to distinguish and trace the propagation signal of baroclinic Rossby waves in the SCS.