Interaction between the MJO and Polar Circulations

The tropical-polar connection was examined using the Wheeler-Hendon MJO RMM index and daily indices for the annular modes - Arctic Oscillation (AO) and Antarctic Oscillation (AAO), from 1979 to 2008. The AO and AAO indices were filtered to extract the intraseasonal and long term component. Our results support the conclusion of L’Heureux and Higgins that the MJO convection located in the Indian Ocean (the MJO phase 1-4) may contribute to forcing or enhancing of the positive phase of AO. However, on the longer (larger then 90 days) time scales the relationship between the MJO and AO is the opposite - with the phases 5-8 (Pacific convection) associated with the positive AO. This suggests the negative feedback - possibly through the atmosphere-ocean interaction. The relationship between the MJO phase and the Antarctic annular mode was also investigated. We found that during the Southern Hemisphere winter Indian Ocean convection was favored during the positive phase of AAO, suggesting the teleconnection mechanism similar to that observed in the Northern Hemisphere for MJO and AO. During the Southern Hemisphere summer, positive AAO was associated with suppressed MJO convection in the Indian Ocean. This seasonal reversal of MJO interaction with an annular mode was not observed in the Northern Hemisphere.