Long-term changes in the relationship between stratospheric circulation and East Asian winter monsoon

Abstract

Using two generations of reanalysis datasets from the National Center for Atmospheric Research (NCAR), European Centre for Medium-Range Weather Forecasts (ECMWF), and Japan Meteorological Agency (JMA), we showed that on the interannual timescale the two leading modes of the East Asian winter monsoon (EAWM) are associated with tropospheric annular mode (AM) and stratospheric polar vortex (SPV), respectively. The relationship between AM and the first EAWM mode remained stable during 1958–2013, whereas that between SPV and the second EAWM mode increased suddenly since the late 1980s. The SPV-related circulation and planetary wave activities are intensified in the latter period. We suggested that this change might be caused by the global warming and ozone depletion.