The Lack of a QBO‐MJO Connection in Climate Models With a Nudged Stratosphere
The observed connection between the easterly phase of the quasi-biennial oscillation (QBO) and enhanced Madden-Julian oscillation (MJO) activity over the maritime continent during boreal winter is not well captured by climate models. We nudge stratospheric horizontal winds to improve the QBO in the E3SM, CESM, GFDL, and GISS models to see if they are then able to capture this relationship.
Improving the QBO through nudging stratospheric winds is not sufficient to capture the QBO-MJO relationship that is found in observations. Additionally, although the mechanisms for the observed relationship are not well understood, we assess some hypotheses for model deficiencies related to this stratosphere-troposphere interaction.
By testing this method of improving the simulated representation of the QBO, we find that the models still do not capture the QBO-MJO connection that is found in observations. We find that the MJO-related vertical structure of temperature and winds are well represented in the models compared with observations. However, we do find biases in the cloud-radiative feedbacks and MJO vertical velocity, yet neither of these conclusively explain the lack of simulated QBO-MJO connection.