第七届青年地学论坛

The El Niño-Southern Oscillation (ENSO) events which generally mature in winter profoundly affect the following summer rainfall in eastern China (ECSR), but such an impact can change significantly with decadal background. This study examines how the impact changes since the 1950s by running correlation and regression analyses. It is found that the ENSO’s impact on ECSR has undergone two decadal shifts in the late 1970s and 1990s, respectively. Sequentially, three distinct ENSO-induced ECSR anomaly patterns are categorized, which exhibit both robust and changeable sides. The robust side manifests generally more precipitation in the Yangtze River basin affected by the anomalous tropical western North Pacific anticyclone (WNPAC) in the post-El Niño summer. The changeable side is reflected in the more variable ENSO-induced rainfall anomalies north of the Yangtze River, due to the ENSO-induced different East Asian midlatitude circulation anomalies. Meanwhile, the El Niño-induced drought in South China is enhanced since the late 1970s with the intensification of the anomalous WNPAC. The ENSO’s changing impact on the ECSR stems from the changes of ENSO-induced tropical and midlatitude circulation anomalies over East Asia, which are associated with different zonal (from tropical Pacific to Indian Ocean) and meridional (from tropical Pacific to Midlatitude North Pacific) teleconnections of ENSO-induced SST anomalies. The former affects the intensity and location of the anomalous WNPAC by affecting Indian Ocean capacitor effect and convection anomalies over the tropical Indo-western Pacific. The latter modulates the ocean-to-atmosphere feedback in the midlatitude North Pacific, contributes to different local geopotential anomaly sources, and then directly or indirectly through Rossby wavetrain affects the East Asian midlatitude circulation.
 

ENSO,climate change,sea surface temperature,Teleconnection; decadal change,Rainfall,atmospheric circulation