Eurasian (Wallace–Gutzler)

−¼Z*(55°N,20°E) + ½Z*(55°N,75°E) − ¼Z*(40°N,145°E) on standardized Z500 anomalies. Positive = ridge over western Siberia, troughs over Europe and Japan (strong Siberian High). Commonly cited WG81 coefficients. — Wallace & Gutzler 1981, Mon. Wea. Rev. 109, 784–812, doi:10.1175/1520-0493(1981)109<0784:TITGHF>2.0.CO;2