Two Leading Modes in the Evolution of Major Sudden Stratospheric Warmings and Their Distinctive Surface Influence

Height-time domain empirical orthogonal function (EOF) analysis is conducted to extract the dominant variations in the evolution of sudden stratospheric warming events (SSWs). The EOF1 corresponds to weak (I+) and strong (I-) polar vortex before the onset of SSWs and EOF2 indicates strong (W+) and weak (W-) warming during SSWs. The development of I- SSWs is associated with stronger eddy heat flux contributed by planetary wavenumbers 1 and 2, whereas the I + SSWs is related to wavenumber 1. W + SSWs are linked to both wavenumbers 1 and 2, while the happening of W- SSWs is associated with wavenumber 1. SSWs of I+ and W+ can exert influence on the surface such as negative phase of the North Atlantic Oscillation, which indicates that SSWs with different initial polar vortex states and warming intensities lead to different surface influence. This could help to better predict the tropospheric response following SSWs.