What type of summer North Atlantic Oscillation will trigger the downstream Silk Road teleconnection pattern, and how?

The summer North Atlantic Oscillation (SNAO) has been shown to exert a significant influence on downstream climate anomalies, primarily via the Silk Road teleconnection pattern (SRP). However, the linkage between the SNAO and the SRP is not consistently robust, and the SNAO does not invariably excite the SRP. The SRP itself is an upper-tropospheric teleconnection pattern traveling along the midlatitude Asian westerly jet, characterized by alternating southerly and northerly wind anomalies. In this study, we focus on the considerable variability of the SNAO’s southern branch and categorize the interannual SNAO–SRP relationship into two categories: a strongly linked category and a weakly linked category. Our results indicate that, under the strongly linked category, the SNAO’s southern branch retracts westward toward the Baltic Sea, whereas under the weakly linked category, it extends eastward beyond the Ural Mountains. When the southern branch retracts westward, a pronounced negative precipitation anomaly over Europe induces upper-level convergence, producing a strong positive Rossby wave source (RWS) anomaly, which effectively excites the downstream SRP wave train. In contrast, when the southern branch extends eastward, this process does not hold. These findings link the morphology of the SNAO to its capability to initiate the SRP, offering new insights into how the SNAO exerts remote impacts.