资源环境科技发展态势分析平台

Previous studies indicated that boreal winter cold events over East Asia are related to the Madden-Julian Oscillation (MJO) convection situating over the tropical Indian Ocean (commonly known as MJO phases 2-3). The present study identified that more than 70% of intraseasonal cold events over eastern China are associated with the MJO phases 2-3 in early winter (November-December) but less than 50% of the cold events are linked to MJO phases 2-3 in late winter (February-March). This difference is related to a change in the connection between the MJO and the Arctic Oscillation (AO) from early winter to late winter. In early winter, MJO phases 2-3 related cold events over eastern China are related to a midlatitude Rossby wave train triggered by negative AO, as MJO phases 2-3 tend to follow negative AO. In late winter, the connection between the MJO and the AO is weak, which leads to a weakened relationship between MJO phases 2-3 and cold events. The weakened connection between the MJO and the AO in late winter is caused by the weakened meridional heat fluxes and their weakened constructive interference with climatological stationary waves and a decrease in the poleward propagation of tropospheric eddy momentum and heat fluxes over the western Pacific.