Relationship Between Phase Reversal Of The Winter Temperature In Middle-high Latitude Of The Northern Hemisphere And The Winter AO/NAO's Intraseasonal Fluctuation

Besides the winter mean temperature,the conspicuous intraseasonal oscillation of winter air temperature also exerts large influence on human beings and economic activities.Based on the observational and the reanalysis datasets during the period of 1959-2018,this paper expounds the characteristics of the phase reversal in middle-high latitudes of the Northern Hemisphere temperature from early to late winter,and its relationship with AO/NAO's intraseasonal fluctuation.The main conclusions of this article are as follows:(1)The characteristic of intraseasonal winter temperature is a reversal phase pattern which is universal in middle-high latitudes of the northern hemisphere.The spatiotemporal variability of temperature in East Asian is mainly characterized by the intraseasonal phase inversion variation pattern,which means warmer(colder)than normal in early winter and colder(warmer)in late winter.This mode accounts for 31.1% of the temperature variance.The circulation evolution of this mode is mainly characterized by the phase inversion of the Eurasian teleconnection pattern(EU)from a positive(negative)phase in early winter(December)to a negative(positive)phase in late winter(February).The main mode of winter temperature fluctuation in North American is also in a reverse phase from the early to late winter.Differently,their spatial distribution is characterized by east-west dipole.The circulation evolution of this mode is mainly characterized by the AO/NAO's phase reversal from the early to late winter.(2)The mode of AO/NAO phase reversal from the early(December)to late winter(February)often occurs,and it can impact the intraseasonal oscillation of winter temperature throughout the northern hemisphere.For different regions,influences of winter temperature from AO/NAO phase reversal and its physical mechanisms are different.As for East Asia,AO/NAO through the connection of the North Atlantic heat flux("Ocean Bridge")affects the Eurasian teleconnection phase reversal("Atmospheric Bridge"),which father affects the winter temperature phase reversal from early to late winter.The influence of AO/NAO on Eurasia is indirect.As for America,AO/NAO can directly affect the temperature phase reversal through the circulation of the North Atlantic and the North Pacific.(3)In 2015/2016 winter,the temperature is a phase reversal pattern from early to late winter in the whole northern hemisphere.The positive phase of AO with warmer temperature in East Asian and East America in the early winter was affected by the stratospheric polar vortex,and the colder temperature in late winter was affected by the El Ni(?)o event with AO turned to negative phase.The intraseasonal turning of AO/NAO phase in 2015/16 is related to the combined action of stratospheric polar vortex and ENSO.