The influence of Quasi-Two-Day waves on the transport of CO₂ based on WACCM-NEDAS data assimilation

The distribution and transport of carbon dioxide (CO₂) in the middle and upper atmosphere are closely linked to atmospheric dynamical processes, but the influence of planetary waves on CO₂ transport remains unclear. This study aims to investigate the impact of quasi-two-day waves (Q2DW) on CO₂ transport in the stratosphere-mesosphere during the SSW period. Based on NEDAS+WACCM data assimilation (DA) from December 2018 to February 2019, we used the transformed Eulerian mean (TEM) framework to conduct diagnostic analysis on Q2DW propagation and amplification. Meanwhile, unstable regions are identified in the stratosphere between 60°N and 80°N. This configuration facilitates the amplification of Q2DWs through enhanced baroclinic/barotropic instability. The results demonstrate that the dynamic features exhibit distinct propagation and amplification characteristics. Besides, we also found distinct Q2DWs in CO₂ at mid-latitudes of the Southern Hemisphere (SH), which are mainly induced by the Q2DWs in temperature. Further analysis shows that the anomalous vertical motions during the SSW period could lead to the enhancement of CO₂ vertical gradients, which also contribute to the strengthening of Q2DWs in CO₂.