Modulation of the Tibetan Plateau snow cover on the interannual variations of the MJO-Related winter surface air temperature anomalies over East Asia

Previous studies have revealed that the Madden-Julian oscillation (MJO) can exert a profound impact on the surface air temperature (SAT) anomalies over East Asia during winter (December-February). In this study, it is found that such MJO-related winter SAT anomalies can be modulated by the interannual variability of the Tibetan Plateau snow cover (TPSC). During the excessive TPSC (ETPSC) winters, the MJO-related East Asian SAT anomalies in phase 3 are significantly colder than normal. However, during the reduced TPSC (RTPSC) winters, such SAT anomalies are close to normal. A linear baroclinic model is used to examine the possible physical mechanisms. During the ETPSC winters, the more energetic MJO can excite stronger poleward Rossby waves and intensify the upper level cyclonic anomalies over East Asia and lead to the significantly colder SAT anomalies. While during the RTPSC winters, the suppressed MJO convection excites weaker poleward Rossby waves and cannot make colder SAT anomalies over East Asia. The numerical evidences also show that the variation of the mean state could affect the teleconnections but it does not benefit a stronger Rossby wave train over East Asia in ETPSC winters. These results confirm that the TPSC can exert a profound modulation effect on the MJO teleconnection and further impact on the winter SAT anomalies over East Asia.

Automated summary

Previous studies have shown that the Madden-Julian oscillation (MJO) has a significant impact on surface air temperature (SAT) anomalies over East Asia during winter. This study reveals that the interannual variability of the Tibetan Plateau snow cover (TPSC) can modulate these MJO-related winter SAT anomalies.