The East Atlantic/West Russia (EA/WR) teleconnection in the North Atlantic: climate impact and relation to Rossby wave propagation

摘要

Large-scale winter teleconnection of the East Atlantic/West Russia (EA/WR) over the Atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence. A rotated empirical orthogonal function analysis of the upper-tropospheric monthly height field captures successfully the EA/WR pattern and its interannual variation, with the North Atlantic Oscillation (NAO) as the first mode. EA/WR's climate impact extends from eastern North America to Eurasia. The positive (negative) EA/WR produces positive (negative) temperature anomalies over the eastern US, western Europe and Russia east of Caspian Sea, with negative (positive) anomalies over eastern Canada, eastern Europe including Ural Mountains, northeastern Africa and the Middle East. These anomalies are largely explained by lower-tropospheric temperature advections. Positive (negative) precipitation anomalies are found over the mid-latitude Atlantic and central Russia around similar to 60 degrees anomaly is dominant. Eastern Canada and western Europe including the Mediterranean region are characterized by negative (positive) precipitation anomalies. The EA/WR is found to be closely associated with Rossby wave propagation. Wave activity fluxes show that it is strongly tied to large-scale stationary waves. Furthermore, a stationary wave model (SWM) forced with vorticity transients in the mid-latitude Atlantic (similar to 40 degrees N) or diabatic heat source over the subtropical Atlantic near the Caribbean Sea produces well-organized EA/WR-like wave patterns, respectively. Sensitivity tests with the SWM indicate enhancement of EA/WR-like blocking over west of Scandinavia when the mean state is modified to have a positive NAO component that enhances upper-level westerlies between 40 and 60 degrees N.