The Causes Of Interdecadal Variation Of "Warm Arctic-Cold Eurasia" Mode

Based on the surface temperature of NASA's Goddard Institute for space research,the reanalysis data of NOAA-CRISES in the 20 th century,the sea surface temperature and sea-level pressure of the Met Office Hadley Center of the United Kingdom,the reanalysis data of the NCEP/NCAR of the United States,and the results of Coupled Model Intercomparison Project Phase 6,We analysis the interdecadal variation characteristics and physical causes of the "Warm Arctic-Cold Eurasian"(WACE)mode during the boreal winter(DJF)of 1910 / 1911 ? 2019 / 2020.It is found that WACE has a significant interdecadal variation characteristic.During the positive phase of WACE,the blocking frequency of Ural at high latitude is high,which leads to the heat transferred to the Arctic and the abnormal warm advection in the Arctic region.At the same time,the water vapor convergence in the Arctic region leads to the increase of downward long wave radiation.In addition,the convective activity is enhanced and the latent heat is released,which results in the positive anomaly of Arctic temperature.At the same time,the weakening of Eurasian polar vortex and Eurasian westerly,and the high frequency of blocking in high latitude of Urals are conducive to the frequent southward movement of cold air,resulting in abnormal cold advection in Eurasia.At the same time,the divergence of water vapor in Eurasia,the negative anomaly of downward long wave radiation,accompanied by the decrease of convective activity and the decrease of latent heat release,lead to the negative anomaly of temperature in Eurasia.In addition,there is a close relationship between North Atlantic sea surface temperature and WACE on interdecadal scale.The anomalous atmospheric circulation patterns corresponding to the interdecadal variation of sea surface temperature in the North Atlantic are similar to those corresponding to WACE.Furthermore,using the CAM3.0 general circulation model,We have verified that the positive sea surface temperature anomalies in the middle latitude and subtropical regions of the North Atlantic may affect the tropospheric water vapor transport by causing abnormal anticyclone over Eurasia,thus affecting the interdecadal variation of WACE.At the same time,we explore the interdecadal variation of the relationship between the Antarctic oscillation and WACE.Dynamic diagnosis results show that the Antarctic oscillation negative phase with upper troposphere in the southern hemisphere at the high latitude easterly anomaly,abnormal center is located in the northwest of the Antarctic peninsula in the southeast Pacific Ocean and northeast of the Antarctic peninsula over the high latitude in south Atlantic Ocean,through the wave flow interaction,Rossby waves sources are generated in the south of South America and high-latitudes south Atlanticwith Rossby wave energy propagates northward to tropical areas and spreads to Eurasia and the Arctic through the window area of equatorial Atlantic Ocean and equatorial eastern Pacific Ocean in twodimensional horizontal heterogeneous airflow.This may lead to the spread of "-+-+-+" abnormal zonal wind from the middle and high latitude of the South Atlantic in the Southern Hemisphere,through the middle of the South Atlantic,the equatorial Atlantic,the southern side of the Sahara Desert,then to western Siberia,and the northern side of the Kara,leading to abnormal anticyclone in the north of Siberia in upper troposphere.It is conducive to the formation of WACE.