On The Linkage Between Arctic Near-surface Temperature Variations And East Asian Winter Temperature

Based on the NCEP/NCAR monthly reannlysis dataset,ERA-interim daily reannlysis dataset,monthly and pentad surface air temperature(SAT)provided by National Meteorological Information Center,using Empirical Orthogonal Function(EOF),power spectrum,correlation,regression and composite analysis and t-test,the paper investigates the effect of the Arctic near-surface temperature on East Asian winter temperature,There exist direct and indirect relationships between Arctic near-surface temperature and SAT over eastern China at the interannual timescale.The results demonstrate that the nearsurface warming in Barents-Kara Sea has rapidly increased in winter since 1998 and presents a significant negative interannual correlation with SAT over Eastern China,which is named the direct connection between the Arctic and Eastern China.Meanwhile,the interannual associations between the three indexes-Siberian High central intensity(SHCI),Siberian High area(SHA)and Siberian High east boundary(SHEB),and the near-surface temperature over the Arctic and Eastern China are significant in winter,reflecting that the Siberian High is a bridge linking the Arctic and East Asian climate to some extent.When the Arctic near-surface temperature rises(decreases),the intensity of the Siberian High enhances(weakens),its coverage expands(shrinks),its east boundary extends eastward(retreats westward),and SAT decreases(rises)in Eastern China,which is called indirect connection between the Arctic and Eastern China.Then the possible physical mechanisms of the Eastern Asian temperature influenced by the Arctic near-surface temperature are discussed.Subsequently,the possible reasons for cold events over central and eastern China(CEC)in early 2008 and 2016 are explored.Although the tropical Pacific sea surface temperature indicates mature La Ni?a and El Ni?o phase in early 2008 and 2016,respectively,the Arctic is warmer,and notable cold events appear over CEC.At the same time,the westerlies decelerate at mid-latitudes in the upper troposphere,the Ural Mountain Blocking High enhances in the mid troposphere and the Siberian High reinforces in the lower troposphere.Further analyses indicate that cold events and related atmospheric circulation anomalies are associated with Arctic warming.Additionally,the cold/warm phase of the ENSO causes the East Asian winter monsoon(EAWM)to enhance/weaken and correspondingly intensify/mitigate cold events over CEC.In brief,the Arctic warming is superimposed on cold/warm phase of ENSO by thermal and dynamic processes,the atmospheric circulations in the upper,mid and lower troposphere,and the intensity and extent of the EAWM are influenced at first,which are closely linked with East Asian weather and climate.Then,the above-mentioned led to cold events together over East Asia in early 2008 and 2016,simultaneously inducing differences in the intensity and extent of cold events between the two years.With the assistance of the above content,the synergistic influence of ENSO and Arctic warming on East Asian winter temperature is discussed.The results show that the key system in the lower troposphere that influences East Asian winter temperature is Siberian High and in the mid troposphere,the key system is Eurasian Blockings and East Asian trough.La Ni?a and the warming of the Barents-Kara Sea are both conducive to the enhancement of key systems and further promote colder East Asia,but the role of the two factors is not a simple linear superposition.