Cloud as stumbling block for the propagation of the Southern Annular Mode

The Southern Annular Mode (SAM), with an iconic dipolar zonal wind pattern centered around the axis of the storm track, is the most dominant mode of variability orchestrating the weather and wind from the subtropics to the poles. Its origin, maintenance and feedback have been one of the central themes of atmospheric dynamics. But what role the clouds play in the life cycle of the annular mode remains largely unknown until now, while the wind pattern associated with SAM has long been observed to organize the distribution of cloud in the storm track.