Interannual Relationship between the West Asian and East Asian Jet Meridional Displacements in Summer

The meridional displacements of the upper-tropospheric westerly jet streams over both West Asia and East Asia (WJMD and EJMD, respectively) in summer manifest as the leading pattern of the zonal wind anomalies over their local domains on the interannual time scale. This study identifies a significant interannual relationship between these two leading patterns, tending to displace in the same meridional direction, either northward or southward. It is shown that the Silk Road pattern, which is a zonal teleconnection pattern along the Asian jet, is an important modulator for the WJMD-EJMD relationship. Another factor is the precipitation anomalies over a broad tropical region, including the Indian subcontinent, the northern Indian Ocean, and the western North Pacific Ocean. Enhanced or suppressed tropical precipitation respectively induces a northward or southward displacement of the primary body of the jet stream from West Asia to East Asia, which contributes to the in-phase WJMD-EJMD relationship, as suggested by both the observations and simple model results. The SST anomalies associated with the tropical precipitation and in-phase WJMD-EJMD relationship are also discussed. The WJMD-EJMD relationship may have an important implication for identifying and explaining the teleconnections of rainfall and temperature over the broad area from West Asia to East Asia, and from the tropics to the extratropics.

Automated summary

The study shows a significant interannual relationship between the meridional displacements of the upper-tropospheric westerly jet streams over West Asia and East Asia. The Silk Road pattern and precipitation anomalies in the tropical region are important factors affecting this relationship. Enhanced or suppressed tropical precipitation can induce a northward or southward displacement of the jet stream, contributing to the in-phase relationship between West Asia and East Asia.