The joint effects of Interhemispheric Oscillation and Arctic Oscillation on climate anomlies in winter

The winter temperature anomalies are influenced by the joint effects of multiple factors. Using NCEP/NCAR reanalysis data from 1979 to 2022,this paper analyzes the circulation patterns and mechanisms influencing temperature anomalies in the mid-to-high latitudes of the Northern Hemisphere under the joint effects of Interhemispheric Oscillation (IHO) and Arctic Oscillation (AO). It was found that the temperature changes under the joint effects of IHO and AO were mainly influenced by AO, with IHO playing a disruptive role. Specifically, when IHO and AO were in the same phase, the disturbance in the polar region would weaken due to the cancellation of different signals, while the disturbance in the mid latitudes would strengthen due to the superposition of the same signals. There is a significant meridional horizontal propagation of Rossby wave energy in the North Pacific and North Atlantic. Stratospheric planetary waves mainly propagate downward over the Eurasian continent, while areas north of 60 °N in North America exhibit oblique downward propagation of stratospheric planetary waves, and areas south of 60 °N exhibit significant southward propagation of planetary waves in the troposphere. When IHO and AO are in opposite phases, disturbances in the Arctic region are enhanced due to the superposition of the same sign, but disturbances in the mid latitude region are weakened due to the cancellation of opposite signs. There is obvious Rossby meridional propagation in the North Pacific and North Atlantic, with wave energy dispersed upwards at high latitudes and propagating towards low latitudes. In addition, the maximum contribution of IHO and AO to surface air temperature is mainly due to the disturbance of horizontal temperature advection caused by the steady wind field and diabatic heating. These conclusions provide reference for studying temperature anomalies and can better understand the mechanisms and impacts of atmospheric circulation anomalies.