Stratospheric Arctic Polar Vortex Modulated by the Sea Surface Temperature Warming in the Western Equatorial Pacific in Early Spring

Stratospheric Arctic vortex (SAV) anomalies can provide indications for severe weather and Arctic ozone losses in winter and spring. In early spring, the SAV is connected to the second mode of the interannual sea surface temperature (SST) in the Tropical Pacific from 1979 to 2020 and the spatial pattern of SST anomalies in the western equatorial Pacific from the ERA5 reanalysis data. The specific progress of the western equatorial Pacific SST anomalies affecting the SAV is revealed using CAM5 numerical simulations. In winter and spring, the SST warming in the western equatorial Pacific can intensify local deep convective precipitation. The anomalous latent heating induces a Rossby wave (high-pressure anomalies in the upper troposphere) to its northwest side via the Matsuno–Gill atmospheric response. The Rossby wave modifies the strength and position of the strongest trough-ridge system of the Northern Hemisphere in the North Pacific along the great circle path, decreasing the amplitude of the meridional winds’ wave 1 and an increase in the phase difference of wave 3 between the meridional wind and temperature, resulting in less wave activity fluxes of waves 1 and 3 propagating to the stratosphere. Finally, in the spring, decreased poleward transmission of eddy heat flux enhances the SAV.