Teleconnection

Teleconnection is the phenomenon by which climate anomalies in one region influence weather patterns in distant regions, through the propagation of large-scale atmospheric waves. The term was coined by Gilbert Walker in the 1930s to describe statistically significant correlations between remote pressure observations, but the physical mechanism — the propagation of stationary Rossby waves along great-circle paths from tropical heat sources to extratropical regions — was not understood until the advent of numerical weather prediction in the 1960s. Teleconnections are not causal chains in the simple sense of one event triggering another. They are patterns of coherent atmospheric response to a common forcing: the reorganization of the global circulation when a heat source shifts.

The El Niño-Southern Oscillation is the most powerful teleconnection driver. A warm sea surface temperature anomaly in the eastern Pacific perturbs the upper-tropospheric vorticity field, generating Rossby wave trains that propagate poleward and eastward, affecting North American winter weather, European storm tracks, and Asian monsoon timing. Other teleconnection patterns include the North Atlantic Oscillation, the Arctic Oscillation, and the Pacific-North American pattern. Each is a standing wave pattern of the atmospheric circulation, and each can be understood as a normal mode of the coupled Earth System dynamics.