The summer North Atlantic Oscillation (SNAO) strongly affects the climate variability over Europe and down- stream East Asia similar to its winter counterpart. This study thus investigates the interannual relationship between SNAO and the subsequent autumn precipitation anomalies over Yunnan, Southwest China and related physical mech- anisms based on reanalysis data during 1958–2020. The results show that the interannual variations in SNAO exhibit a significant positive correlation with anomalies of Yunnan precipitation in November. Composite analyses demon- strate that for the positive SNAO phase, the positive sea surface temperature anomalies (SSTAs) in midlatitude North Atlantic as part of a tripole SSTA tend to weaken from summer to November through changes in surface heat fluxes. In turn, the predominately negative SSTA in tropical North Atlantic that persists into November induces an anomal- ous cyclone at midlatitudes, which triggers two middle–upper tropospheric wave trains propagating from midlatitude North Atlantic to Yunnan. The subtropical wave train propagates eastward along the subtropical westerly jet, and the mid–high latitude wave train follows the great circle path across Scandinavia and central Asia to the Tibetan Plateau. Both wave trains favor development of an anomalous cyclone over the southern Tibetan Plateau. The upper-tropo- spheric divergent condition on the southeastern side of the anomalous cyclone is dynamically conducive to locally as- cending motion over Yunnan, thus producing above-normal precipitation. The opposite situation occurs in the negat- ive SNAO phase. A coupled model reproduces well the wave train propagation and thereby confirms the positive re- lationship between SNAO and Yunnan precipitation in November.

Shabin HAO;Jiandong LI;Jiangyu MAO

State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics,Chinese Academy of Sciences,Beijing 100029;University of Chinese Academy of Sciences,Beijing 100049

气象学报（英文版）

[1]Shabin HAO;Jiandong LI;Jiangyu MAO-.Interannual Relationship between Summer North Atlantic Oscillation and Subsequent November Precipitation Anomalies over Yunnan in Southwest China)[J].气象学报（英文版）,2022(05):718-732,中插24-中插27

SNAO,anomal,Scandinavia,tropo,cending,negat

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