Modulations of the Silk Road Teleconnection Pattern Under Global Warming in Large Ensemble AGCM Simulations

Abstract:

The Silk Road pattern is a wave-like teleconnection pattern along the summertime Asian jet which induces extreme climate anomalies in East Asia in summer. The present study examines modulations of the Silk Road pattern under global warming, based on large ensemble simulations by a high-resolution atmospheric general circulation model called d4PDF. While there is little change in the horizontal structure, the magnitude of the Silk Road pattern significantly decreases under global warming, with a slight upward shift of the anomaly peak level. This vertical structure change is consistent with the upward shift of the Asian jet associated with the tropopause elevation. Due to this structural change and increased background static stability, the baroclinic energy conversion becomes less efficient in the lower troposphere, contributing to the weakening of the Silk Road pattern. Besides, the North Atlantic polar front jet shifts poleward while the Asian jet displaces equatorward under global warming, which are robust across CMIP5 models. This enlarging gap between the two jets makes the wave-activity injection less efficient from Euro-Atlantic blocking, which forms in the exits of the polar front jet, to the Asian jet. Besides the blocking activity and its interannual variability weaken over Europe. Resultant reduction of upstream influences also contribute to the weakening of the Silk Road pattern.