Interdecadal change between the Arctic Oscillation and East Asian climate during 1900–2015 winters

ABSTRACT Using the ERA‐20th century reanalysis data for the period 1900–2009 and NCEP/NCAR reanalysis data for the period 1948–2016, this work inspects the interdecadal variations between Arctic Oscillation (AO) and the surface air temperature (SAT) in East Asia, then investigates possible mechanisms, and finally considers a recent switch of the AO–SAT relationship. It is revealed that the AO–SAT relationship is statistically significant during 1928–1948 and 1975–1995. It means that positive AO is associated with significant weakening of the sea level pressure (SLP) gradient over East Asia, East Asian trough, and East Asian jet stream. However, the AO–SAT relationship is statistically insignificant and there is little significance in the AO‐related circulation during 1905–1925 and 1950–1970. Further examination revealed that the unstable AO–SAT relationship might be attributable to the interdecadal change of AO's Azores center. During 1928–1948/1975–1995 winters, the SLP anomalies of Azores high in the positive phase of AO are robust and lead to upper‐level convergence anomalies, which can induce obvious significant Rossby wave source (RWS) anomalies over the Mediterranean and northeastern Atlantic. During 1905–1925/1950–1970, however, the SLP anomalies of Azores high in the positive AO phase become weaker. As a result, the convergence and RWS anomalies at upper level are mainly confined to the Mediterranean region and the associated wave activity is weaker compared with that in 1928–1948/1975–1995. Since the AO–SAT relationship has experienced two significant periods and two insignificant periods, it suggests a weakening of the AO–SAT relationship in recent two decades.