Propagation diversity of mid-high-latitude Eurasian intraseasonal oscillation during boreal winter

This study aims to explore the propagation diversity of mid-high-latitude Eurasian intraseasonal oscillation (ISO) during boreal winter. Based on K-means cluster analysis, the observed ISO propagation patterns can be objectively classified into a continuous westward propagation, a weak eastward propagation and a jumping westward propagation. A dynamic diagnosis reveals that the interaction between meridional wind and vorticity on different time scales is the important cause of different ISO propagation types. Moreover, background sea surface temperature (SST) anomaly potentially affected the ISO propagation diversity. The three types of propagating ISOs are related to Central Pacific (CP) El Ni & ntilde;o-like SST, Pacific tripolar SST, and CP La Ni & ntilde;a-like SST, respectively. The background wind field due to different wave trains results in propagation diversity of mid-high-latitude ISO. The experiments using ECHAM4.6 model further indicate that heating in the equatorial western-central Pacific, warm SST in eastern Pacific and CP La Ni & ntilde;a-like SST are important in inducing the observed background wave train at mid-high latitudes in three ISO types, respectively. Additionally, the above different propagating ISOs can modulate the extreme cold events in southeastern Europe, Central Asia and Northeast Asia. The present results deepen the understanding of intraseasonal variability at mid-high latitudes and facilitate the prediction of the extreme cold events.