309 / 2024-09-13 20:37:08

Linkage between the tropical SST forcings and the surface air temperature over mid-high latitudes of Eurasia during boreal spring: a new perspective of potential vorticity circulation

potential vorticity (PV), PV circulation, surface air temperature

In this study, firstly the new concept of potential vorticity (PV) circulation whose convergence (divergence) leads to a positive (negative) PV is revisited. By introducing the “PV circulation” (PVC) into Northern Hemisphere, we demonstrate that the interannual cross-equatorial PVC is closely linked to the notable uniform anomalies of spring cold surface air temperature (SAT) over the mid–high latitudes of Eurasia by virtue of the PVC, and the PV-θ mechanism. Further analysis reveals that equatorial sea surface temperature (SST) forcings, such as the El Niño–Southern Oscillation and tropical South Atlantic uniform SST, can directly drive anomalous cross-equatorial PVC by changing the zonal circulation over the equator, thereby influencing SAT in the Northern Hemisphere. All results indicate that the perspective of PVC can provide a reasonably direct and simple connection of the circulation and climate between the tropics and the mid–high latitudes. Finally, this new PVC and the traditional Rossby wave framework are briefly compared in the context of tropical-extratropical interaction.