The role of Antarctic sea ice in modulating the relationship between September-October Antarctic Oscillation and following January-February wet and cold weather in southern China

A previous study found that the September-October (SO) Antarctic Oscillation (AAO) shows an out-of-phase variation of late January-February (JF) wet and cold weather (wet-cold) in southern China. This study explored the underlying mechanism and found that Antarctic sea ice may be responsible partially for such a relationship. The SO AAO stimulates the Antarctic sea-ice dipole pattern (ADP) anomalies, which induce the anomalous convective precipitation of the Inter-Tropical Convergence Zone (ITCZ) in Latin America-Atlantic (LAA) and Western Pacific (WP) in following JF. The anomalous convections over the ITCZ regions trigger planetary wave dispersions from the tropical LAA and WP to adjust the East Asian atmospheric circulation. Through the bridge of anomalous ITCZ, an increased JF ADP decreases the invasion of both northerly cold air flow and southwesterly moist airflow into southern China, resulting in the dissipation of wet-cold and vice versa. Furthermore, the variation of JF ADP is well correlated with the in-phased polar vortex, connecting to the stratospheric Quasi-Biennial Oscillation (QBO). The variation of JF QBO induces the anomalous convection over the tropical North Atlantic and ITCZ in LAA and WP, in turn modulating the contemporary invasion of cold and wet airflow into southern China by Rossby wave dispersion, subsequently wet-cold in southern China. To summarize, JF ADP affects the simultaneous wet-cold in southern China through the anomalous ITCZ. The turning phase of QBO modulates such correlation by inducing the anomalous ITCZ correlated with ADP and the anomalous convection due to QBO itself over tropical North Atlantic.