Classification of wintertime large-scale tilted ridges over the Eurasian continent and their influences on surface air temperature

Abstract

This study investigates the major patterns of large-scale tilted ridges (LSTRS) over the Eurasian continent and their connections with large-scale surface air temperature during boreal winter. A total number of 134 LSTR events with zonal extent exceeding 90° of longitude on the peak day are identified. Using self-organizing map (SOM), the LSTRs are classified into five clusters that are characterized by different spatial distributions and orientations. The leading two clusters are closely associated with extensive and persistent cold events over different places. Considering the first cluster, LSTRs extend from the Ural Mountains to Northeast Asia and are favorable for the amplification and southeastward extension of the Siberian high. Therefore, this cluster is closely associated with the occurrence of extensive and persistent cold events in china. In comparison with the first cluster, the LSTRs of second group are situated to the west, with starting points from the Kola Peninsula, and cause extensive and persistent cold events over Eastern Europe, central Asia, and central Siberia. The results suggest that the vertical coupling between LSTRs and the corresponding anomalous sea level pressure is crucial for the persistent cold temperature events associated with the leading two SOM clusters.

Keywords

• Large-scale tilted ridges
• self-organizing map
• extensive and persistent cold event
• Siberian high