The Relationship between the Ural Blocking in Boreal Winter and the East Asian Winter Monsoon

Based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) gridded reanalysis data during 1948-2013, the relationship between the Ural blocking in boreal winter and the East Asian winter monsoon was investigated on both interannual and intraseasonal time scales. Results show that the integrated index of the East Asian winter monsoon is highly correlated with the Ural blocking frequency. In addition, they share the same linear tendency and period. The Ural blockings exert significant influences on the East Asian winter monsoon on interannual time scale. Further analyses suggest that in the winter with frequent occurrence of the Ural blocking, the anti-cyclone over Siberia at 500 hPa tends to intensify and the East Asian trough becomes deeper than normal. There are also significant signals in the lower troposphere. High frequency of the Ural blocking potentially promotes a cold EAWM (East Asia Winter Monsoon) and equatorward wind anomalies over Lake Baikal and the coastal region of East Asia. As such, a link is established between the EAWM and the Ural blocking. The intensification and eastward migration of Siberia High correspond to the peak and decaying of the Ural blocking. Meanwhile, equatorward wind anomalies develop and gradually affect a large area from Lake Baikal to the east of the Philippines.