Some advances in studies of the climatic impacts of the Southern Hemisphere annular mode

The Southern Hemisphere (SH) annular mode (SAM) is the dominant mode of atmospheric circulation in the SH extratropics. The SAM regulates climate in many regions due to its large spatial scale. Exploration of the climatic impacts of the SAM is a new research field that has developed rapidly in recent years. This paper reviews studies of the climatic impact of the SAM on the SH and the Northern Hemisphere (NH), emphasizing linkages between the SAM and climate in China. Studies relating the SAM to climate change are also discussed. A general survey of these studies shows that signals of the SAM in the SH climate have been systematically investigated. On interannual scales, the SAM can influence the position of storm tracks and the vertical circulation, and modulate the dynamic and thermodynamic driving effects of the surface wind on the underlying surface, thus influencing the SH air-sea-ice coupled system. These influences generally show zonally symmetrical characteristics, but with local features. On climate change scales, the impacts of the SAM on SH climate change show a similar spatial distribution to those on interannual scales. There are also meaningful results on the relationship between the SAM and the NH climate. The SAM is known to affect the East Asian, West African, and North American summer monsoons, as well as the winter monsoon in China. Air-sea interaction plays an important role in these connections in terms of the storage of the SAM signal and its propagation from the SH to the NH. However, compared with the considerable knowledge of the impact of the SAM on the SH climate, the response of the NH climate to the SAM deserves further study, including both a deep understanding of the propagation mechanism of the SAM signal from the SH to the NH and the establishment of a seasonal prediction model based on the SAM.