ENSO regulation of MJO teleconnection

Abstract

The extratropical teleconnections associated with Madden–Julian Oscillation (MJO) are shown to have an action center in the North Pacific where the pressure anomalies have opposite polarities between the Phase 3 (convective Indian Ocean) and Phase 7 (convective western Pacific) of the MJO. The teleconnection in the same phase of MJO may induce opposite anomalies over East Asia and North America between El Nino and La Nina years. During MJO Phase 3, a gigantic North Pacific anticyclonic anomaly occurs during La Nina, making coastal northeast Asia warmer/wetter than normal, but the west US colder/drier; whereas during El Nino the anticyclonic anomaly is confined to the central North Pacific, hence the northwest US experiences warmer than normal weather under influence of a downstream cyclonic anomaly. During Phase 7, an extratropical cyclonic anomaly forms over the northwest Pacific during La Nina due to convective enhancement over the Philippine Sea, causing bitter winter monsoon over Japan; whereas during El Nino, the corresponding cyclonic anomaly shifts to the northeast Pacific due to enhanced convection over the equatorial central Pacific, which causes warm and wet conditions along the west coast of US and Canada. Further, the presence of ENSO-induced seasonal anomalies can significantly modify MJO teleconnection, but the aforementioned MJO teleconnection can still be well identified. During Phase 3, the MJO teleconnection pattern over North Pacific will be counterbalanced (enhanced) by El Nino (La Nina)-induced seasonal mean anomalies. During Phase 7, on the other hand, the MJO teleconnection anomalies in the northeastern Pacific will be enhanced during El Nino but reduced during La Nina; thereby the impacts of MJO teleconnection on the North America is expected to be stronger during El Nino than during La Nina.