[A-AS03] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS03-P11] The interannual impact of the North Atlantic sea surface temperature on the surface air temperature over southern China in February

*Chengyang Zhang¹、Zhihai Zheng²、Shaobo Qiao³、Sheng Lai¹、Liyang He¹ (1.Guangxi Meteorological Bureau, China、2.National Climate Center, China、3.Sun Yat-sen University)

キーワード：Prolonged low temperature, Rossby wave train, North Atlantic SST, East Asian winter monsoon

Prolonged low temperature significantly threatens transportation and planting in populous areas and is closely linked to slowly varying forcing such as sea surface temperature (SST). In this study, we reveal the impact of the north–south dipole pattern in extra-tropical North Atlantic SST (DNA) anomaly on surface air temperature (SAT) over southern China in February. The positive phase of the DNA is favorable for a positive North Atlantic Oscillation (NAO)-like pattern at the troposphere via synoptic eddy vorticity forcing and triggers a southeastward-propagating Rossby wave train associated with the deepened East Asian trough and the strengthened Siberian high, which are conducive to enhancement of the East Asian winter monsoon. A stronger monsoon leads to lower-than-normal SAT over southern China by intensifying southward cold air outbreaks. Considerably, the extremely low temperature over southern China in February 2022 is explainable by this physical mechanism. Furthermore, experiments with a linear baroclinic model verify that the proposed downstream propagating Rossby wave train is mainly associated with the midlatitude North Atlantic SST anomaly. These results emphasize that the extra-tropical North Atlantic SST anomaly should be focused when interpreting and predicting the late winter SAT over southern China.