Variations of the East Asian Jet Stream and Asian–Pacific–American Winter Climate Anomalies

Abstract

In this study, the authors apply the NCEP-NCAR reanalysis and other observations to depict the association of the Asian-Pacific-American climate with the East Asian jet stream (EAJS). With an emphasis on boreal winter seasons and on interannual timescales, they analyze the variations of the EAJS and their relationships with El Nino-Southern Oscillation (ENSO) and extratropical North Pacific sea surface temperature (SST), and assess the relative connections of the EAJS and ENSO to the anomalies of atmospheric circulation, surface temperature, and precipitation in the Asian-Pacific-American region. It is found that the EAJS is coupled to a teleconnection pattern spanning the entire Asian-Pacific-American region with the strongest signals over east Asia and the western Pacific. This pattern differs significantly from that associated with ENSO, which influences the earth's climate extensively with a strongest impact on the climate over the central Pacific and east. A strong EAJS is associated with an intensification of the weather and climate systems in Asia and over the Pacific such as deepening of the east Asian trough and the Aleutian low and strengthening of the east Asian winter monsoon. It is linked to colder and drier conditions in east Asia and stronger convection over the tropical Asia-Australia sector. Compared with ENSO, the EAJS seems to link to the climate signals of Asia and the Pacific more strongly. An intensified EAJS is also associated with anomalies of temperature and precipitation in North America due to the related changes in stationary wave patterns. While the EAJS does not strongly link to the tropical central-eastern Pacific SST, it is significantly associated with the extratropical North Pacific SST, more specifically the second most dominant mode of the empirical orthogonal function analysis of the SST. In addition, a strong (weak) EAJS seems to follow a large (small) meridional gradient of the western Pacific SST associated with warming (cooling) in the Tropics-subtropics and cooling (warming) in the extratropics.