Dynamic configuration before quasi-biennial oscillation disruptions revealed from the perspective of planetary waves

Abstract

The zonal wind in the tropical stratosphere shows a quasi-biennial oscillation (QBO), which is an important reference for climate prediction and stratosphere-troposphere interaction. However, the periodicity of the QBO was disrupted during the 2015/16 and 2019/20 Northern Hemisphere winters, raising big challenges to its predictability and attracting widespread attention. Previous studies have indicated that planetary wave (PW) activity from mid-latitude in the lower stratosphere is one of the main sources for the reversal of the zonal wind field, our results show that in addition to that, the presence of dissipated eastward-moving waves in the middle stratosphere can be important for the formation of QBO disruptions. The above two wave signs appear successively before the disruption, exert strong negative forcing on the background flow, and together form a dynamic configuration that occurs before the tropical stratospheric circulation anomalies. It may be necessary to take this PW dynamic configuration into account when predicting future QBO disruptions.