Asymmetric characteristics and possible mechanisms of the circulation corresponding to the Arctic-Eurasian temperature dipole pattern
Based on the atmospheric reanalysis data from NCEP/NCAR and the sea surface temperature and sea ice concentration data from 1950 to 2021 provided by the Met Office Hadley Centre,this paper concentrates on the Arctic-Eurasia temperature dipole mode on the interannual timescale and the asymmetric characteristics of its corresponding circulation and possible mechanisms.Results show that the asymmetry of the surface air temperature anomalies of the WACE(Warm Arctic-Cold Eurasia)pattern is weak from both aspects of location and intensity.The temperature anomalies during the WACE events are distributed slightly more northward,and the cold anomalies in Eurasia are slightly stronger compared with the intensity of the warm anomalies during the Cold Arctic-Warm Eurasia(CAWE)events.However,the corresponding circulation of the WACE pattern has obvious asymmetry in its warm and cold phases.The WACE events are usually accompanied with weak positive phase of the North Atlantic Oscillation(NAO)and strong high-pressure systems over Eurasia,while the CAWE events correspond to strong negative phase of NAO.Further analyses show that the asymmetric characteristics of this circulation are related to the asymmetric modulation of the sea surface temperature in the tropical Pacific.When a La Nina event occurs,especially when the center of negative sea temperature anomalies is displaced westward,the surface air temperature anomalies in the mid-high latitudes of Eurasia tend to present a WACE-like pattern.In contrast,CAWE events are mainly controlled by atmospheric internal variability,which are not closely related to the tropical Pacific Sea surface temperature anomalies.
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