Anomalous Propagation of the Quasi-stationary Planetary Waves in the Atmosphere and Its Roles in the Impact of the Stratosphere on the East Asian Winter Climate

Abstract

East Asian monsoon region is influenced by both the vast ocean and continent in the world.Strong disturbances with planetary scale are forced by this thermal contrast between ocean and continent and the topography of Tibetan Plateau.And these planetary scale disturbances are quasi-stationary.By using the reanalysis dataset the influences of anomalous planetary wave activities on the East Asian winter climate are studied mainly on the interannual and intraseasonal timescales.On the interannual timescale,two waveguides of planetary waves in the northern winter have anti-phase oscillation.On the one hand,this interannual oscillation has an interaction with the Northern Annular Mode.On the other hand,it exerts influence on the climate anomalies over East Asia.During the strong low-latitude waveguide winters,the Siberian high tends to wea and the temperature tends to increase over Northeast China and North China.The situation tends to be reverse during the weak low-latitude waveguide winters.The results also indicate that the relationship between the planetary wave activity and the East Asian winter climate on interannual timescale is strongly modulated by the tropical quasi-biennial oscillation(QBO) of zonal wind in the stratosphere.Only in the QBO easterly phase,the interannual oscillation of planetary wave propagation is closely related to the climate anomalies over East Asia.On the intraseasonal timescale,the variability in the quasi-stationary planetary wave activity is closely associated with the low frequency variation of stratospheric polar vortex.The results indicate that the anomalous polar vortex in the stratosphere may have a downward influence on the short-term climate in the troposphere via the interaction with the planetary waves.This downward propagation of stratospheric anomalies associated with polar vortex has an evident influence on the general circulation in the troposphere,and the influence is particularly significant over East Asia.Since the stratospheric variability generally has longer timescales and this downward propagation leads the variations in the troposphere,our research provides a new predictor for the East Asian winter short-term climate anomalies.