Meridional displacement of the East Asian trough and its response to the ENSO forcing

This paper examined the underlying dynamic mechanisms associated with the meridional displacement of the East Asian trough (EAT), which is closely related to the temperature variability in the southern part of East Asian winter monsoon (EAWM). During the southward displacement of the EAT, the Siberian high is stronger and the Aleutian low is displaced southward. This is due mainly to the anomalous cyclonic flow associated with seasonal eddies over the midlatitude central Pacific, which enhances the horizontal advection of cold (warm) air to the southern (northern) part of the EAT in the lower troposphere. The cold (warm) advection narrows (thickens) the height thickness and results in negative (positive) temperature anomalies in the southern (northern) part of the EAT. These anomalous circulation features can be reasonably explained by the phase of the El Nino–Southern Oscillation (ENSO). The results are also verified by the numerical experiments with prescribing ENSO-like heat source anomalies over the tropical eastern and western Pacific in an anomaly atmospheric general circulation model. All of these results advance our understanding for the linkage between the ENSO and the EAWM via its modulation of the EAT.