Austral winter external and internal atmospheric variability between 1980 and 2014

Abstract

We examine the interannual variability of the seasonal mean atmospheric circulation in the Southern Hemisphere during austral winter. The three major modes are identified by rotated empirical orthogonal function (REOF) analysis. As expected, REOF1 is associated with the Southern Annular Mode which is dominated by internal atmospheric dynamics. REOF2 displays a wave train, linked to the western North Pacific monsoon and the Pacific-Japan pattern in East Asia in the same season; REOF3 resembles the Pacific-South American pattern. Externally forced variability strongly projects on both REOF2 and REOF3 so that in the ensemble mean, an atmospheric model with prescribed observed sea surface temperature captures considerable parts of the time evolution of REOF2 (50%) and REOF3 (25%), suggesting a potential predictability for the two modes.