Modulation of the MJO-Related Teleconnection by the QBO in Subseasonal-to-Seasonal Prediction Models

It was found in previous observational studies that the quasi-biennial oscillation (QBO) can modulate the teleconnection over the Atlantic basin related to the Madden–Julian Oscillation (MJO). In this study, we assess the modulation of the MJO-related teleconnection by the QBO in the operational models that participated in the subseasonal-to-seasonal prediction (S2S) project of the World Climate Research Programme/World Weather Research Programme. The enhancement of the positive North Atlantic Oscillation (NAO) after the occurrence of MJO phase 3, which corresponds to enhanced convection in the equatorial Indian Ocean and reduced convection in the tropical western Pacific, under westerly QBO (WQBO) conditions is seen to be captured by most S2S models but, not unexpectedly, to different degrees. In contrast, the enhancement of the NAO after the occurrence of MJO phase 7, when tropical convection anomalies have the opposite signs compared with MJO phase 3, under WQBO conditions is not reproduced in most S2S models. Under easterly QBO (EQBO) conditions, however, some S2S models can reproduce a significant negative NAO after the occurrence of MJO phase 7 but not a positive NAO after the occurrence of MJO phase 3. The results indicate that although the S2S models are able to predict a reasonable MJO up to around three weeks, representing the impact of the QBO on the extratropical teleconnection of the MJO remains challenging.