Variation of circulation and East Asian climate associated with anomalous strength and displacement of the East Asian trough

Abstract

Variations of the East Asian trough (EAT) and its relationship with the East Asian climate are documented in this study. The variations investigated include the trough’s strength and its meridional and zonal displacements. Anomalous cold (warmth) in Southeast Asia is concurrent with the southward (northward) displacement of the EAT. The southward displacement of the EAT is likely associated with an anomalous strong Siberian high and Aleutian low, which manipulate anomalous northerly wind between them. On the other hand, the temperature in northeast Asia is influenced by both the strength and the zonal displacement of the trough. These properties of the EAT are closely linked to temperatures in the northern and southern portions of East Asia. The relation between variations of the EAT and the East Asian winter monsoon is also examined. In addition, the relation between the EAT and transient eddies is studied. Anomalous transient eddies concurrent with variations of the EAT are contributed by a localized anomalous meridional gradient due to the variation of stationary eddies and zonal symmetric structure. Variations in the polar vortex are significant for variations in the strength of the EAT. To investigate the role of eddies in the anomalous evolution of the EAT, we also study stationary and transient eddy forcing on the evolution of anomalous EAT and zonal symmetric structures using wave activity flux and extended E-vectors.