Dynamical mechanism of the stratospheric quasibiennial oscillation impact on the South China Sea Summer Monsoon

摘要

The National Center for the Atmospheric Research (NCAR) middle atmospheric model is used to study the effects of the quasi-biennial oscillation in the stratosphere (QBO) on the tropopause and upper troposphere, and the relationship between the QBO and South China Sea Summer Monsoon (SCSSM) is explored through NCEP (the National Centers for Environmental Prediction)/NCAR, ECMWF (European Centre for Medium-Range Weather Forecasts) monthly mean wind data and in situ sounding data. The simulations show that the QBO-induced residual circulations propagate downwards, and affect the tropopause and upper troposphere during the periods of mid-late QBO phase and phase transition. Meanwhile, diagnostic analyses indicate that anomalous circulation similar to SCSSM circulation is generated to strengthen the SCSSM during the easterly phase and anomalous Hadley-like circulation weakens the SCSSM during the westerly. Though the QBO has effects on the SCSSM by meridional circulation, it is not a sole mechanism on the SCSSM TBO mode.